STAR FISH.CHAPTER LV.THE OCEAN AS A FIELD—THE VARIOUS CROPS IT YIELDS—THE SPONGE—TRANSPLANTING SPONGES—CORAL FISHING—THE DISCOVERY OF THE NATURE OF CORAL—ITS RECEPTION BY NATURALISTS—OYSTER FISHERY—THE OYSTER A SOCIAL ANIMAL—THE YOUNG OYSTER—OYSTER CULTURE—DREDGING FOR OYSTERS—THE AMERICAN OYSTER FISHERY—PEARL OYSTERS—PEARL FISHERIES—THEIR VALUE—SHARK FISHING—CUTTLE FISHING.Though the ocean may appear to be a barren waste of water to the farmer, it has by no means this aspect to the fisherman. To him it is the field in which he labors, and the crops he gathers from it are as diversified in character, and as important for satisfying the demands of the world, as those which the farmer raises. And further than this, the labors of the fisherman have helped to increase our knowledge of the composition and character of the sea, of the habits of the organized beings found in it, as the labors of the farmer have done the same thing for the soil, and the products which it bears.In considering the various fisheries of the ocean, naturally that of the sponge, as one of the lowest forms of animal life, comes first in order. Science is hardly yet decided in its views concerning the organization and development of these obscure and complex creatures, and despite the investigations of modern naturalists, their position in the scale of animal life is still problematical, and their internal organization is still known only imperfectly. Dr. Bowerbank in his work on British Sponges, published in 1866, describes nearly 200 species, but this number by no means includes them all. They are of all sizes, and of all possible diversity of shape. At present the chief sponge fishing is carried on in the Grecian Archipelago and on the coast of Syria. The boat's crew consists of four or five men who, between June and October, seek the sponges under the cliffs and ledges of the rocks. Those obtained in shallow waters are considered inferior; the best are obtained at a depth ranging from twenty to thirty fathoms. The poorer sponges are taken from the shallow waters with harpoons, but are injured by this method of capture. The others are taken by hand. The diver descends to the bottom, and can stay there from a minute to a minute and a half, and carefully detaches the sponges from the rocks with a knife.SPONGE FISHING.Sponge fishing is also carried on in other parts of the Mediterranean, but without any foresight, so that the sponges will, in time, be exhausted. To guard against this contingency, it has been proposed to transplant and acclimatize the sponges upon the coast of France and Algeria, where the composition of the water is the same as that upon the coast of Syria, and where the difference of temperature would prove no impediment to their flourishing. In fact, the farther north the sponges grow, the finer and compacter are their tissue. By use of a submarine boat, supplied with air by a force-pump, it was proposed to collect such specimens, as were best suited for the purpose, removing the rocks with them; and also to collect the young sponges, during the months of April and May, shortly after they have commenced their independent existence, and before they have anchored themselves to some permanent abode, and transport them to a favorable locality. The French Acclimatization Society, in 1862, gave a commission to M. Lamiral, who had passed years in the study of sponges, and who has published an excellent work upon their habits, to collect the germs, and transplant them to the coast of France.Though up to this time, the attempts which have been made to do this have not met with perfect success, yet the results already gained, show that with further experience, perseverance will attain its desired end.Sponges are also fished for in the Red Sea. On the Bahama Banks, and in the Gulf of Mexico, sponges are taken by Mexicans, Spaniards, and Americans, in shallow water. A mast is sunk at the side of the boat, and the diver descends this; gathering the sponges found near the bottom of the pole.Next in order of fishing in deep sea, comes coral fishing. The ancients believed that the coral was a plant, but it is now known that the coral is constructed by a family of polyps living together, and constituting a polypidom. It abounds in the waters of the Mediterranean where upon rocky beds like a submarine forest, the red coral, the most brilliant and celebrated of all coral, grows at various depths, rarely less than five fathoms, or more than one hundred. Each polypidom resembles a red leafless shrub, bearing delicate little star-shaped white flowers. The branches and trunk of this little tree, are the parts common to the family, the flowers are the individual polyps. The branches show a soft, reticulated crust, or bark, full of small holes, which are the cells of the polyps and they are permeated by a milky juice. Beneath the crust is the coral, hard as marble, and remarkable for its striped surface, its red color, and the fine polish it will take. The fishing is chiefly carried on by sailors from Genoa, Leghorn, and Naples, and is a very laborious occupation. The barks engaged in it are small, ranging from ten to fifteen tons. The coral is fished with an apparatus called an engine, consisting of cross bars of wood tied and bolted together at the centre. Below this is a large stone with nets or bags attached. Each engine has a number of these nets, and when let down into the sea, they spread out. The coral grows on the tops of the rocks, and the object is to scrape it off into these bags. By experience, the fishermen come to learn the favorable places for capturing the coral. When such a spot is reached, the engine is thrown overboard, and as soon as it reaches the bottom, the speed of the vessel is slackened, and the capstan, for hauling it up is manned. In this way the engine is dragged over the bottom, becomes entangled with the rocks, and the nets catch the coral. Sometimes rocks of large size are brought on board.CORAL FISHING OFF THE COAST OF SICILY.Up to the last century the opinion of antiquity that coral was a vegetable product was accepted by all naturalists, though no one attempted an explanation how it grew. This opinion was confirmed when the Count de Marsigli announced his discovery of the flowers of the coral plant, and this announcement was considered the final proof of the vegetable origin of coral. In 1723, however, Jean André de Peyssonnel, a pupil of Marsigli's, and a student of medicine and natural history at Paris, was sent to Marseilles, his native place, by the Academy of Sciences, to study the coral in its living condition, and continued his studies on the northern coast of Africa, where he was sent by the French Government.He soon discovered, by a series of careful and delicate experiments, that the coral was an animal product, and that the supposed flowers were the expanded little animals who build up the coral, and who form one of the lowest forms in the series of organized life on the globe. Peyssonnel says: "I put the flower of the coral in vases full of sea-water, and I saw that what had been taken for a flower of this pretended plant was, in truth, only an animal, like a sea nettle or polyp, I had the pleasure of seeing the feet of the creature move about, and having put the vase full of water, which contained the coral, in a gentle heat over the fire, all the small animals seemed to expand. The polyp extended his feet, and showed what M. de Marsigli and I had taken for the petals of a flower. The calyx of this pretended flower, in short, was the animal, which advanced and issued out of his cell."This discovery was received by the naturalists of the time with contempt and ridicule; so much so that Peyssonnel, disgusted, retired into obscurity, leaving his manuscripts in the Museum of Natural History in Paris, where they still remain, unpublished. Before his death, however, in his retirement, he had the satisfaction of seeing his views accepted, and some of those who had most ridiculed them on their first presentation, become the most enthusiastic and effective advocates of them.Besides the coral fished for as we have described, the coral polyp constructs islands, and carries on labors which very materially affect the condition of the ocean and the form of the land, concerning which we will have occasion to speak else where.Another fishery which may be fitly mentioned here is the oyster fishery. There are several varieties of the oyster. Those usually eaten in France are the common oyster (Ostrea edulis), and the horse foot oyster (O. hippopus). The oysters of the Mediterranean are the rose-colored oyster (O. rosacea), and the milky oyster (O. lacteola), with the small and little known crested oyster (O. instata), and the folded oyster (O. plicata). On the Corsican coast the oysters are called foliate (Olamleosa). In France the Cancale and Ostend oysters are chiefly noted. When the first of these has been fed for some time in the parks or beds, and has assumed a greenish color, it is known as the Narenna oyster, from the name of the park in the Bay of Scudre.Natural oyster beds occur in every sea where the coast affords the proper conditions with a shelving and not too rocky bottom. In France the beds of Rochelle, Rochefort, the isles of Re and Oleron, the bay of St. Brieuc, Cancale and Granville are the most famous. On the Danish coast there are forty or fifty beds on the west coast of Schleswig, the best lying between the small islands of Sylt, Amzon, Fohr, Pelworm and Nordstrand. The oyster beds of England extendfrom Gravesend, in the estuary of the Thames and midway along the Kentish coast, and in the estuary of the Coluc and other small streams on the Essex coast. The Frith of Forth is also famous for its oyster beds. The product of these beds has diminished in recent times; according to some authorities from too improvident and persistent dredging, but Mr. Buckland attributes the decrease in the yield to sudden changes in the temperature at the critical period when the spat, or young oysters, are just formed, rather than to over-dredging.The United States is more abundantly furnished with oyster beds than any other country. They extend along almost the entire coast. Those of Virginia are estimated to comprise nearly 2,000,000 of acres. The sea-board of Georgia is famous for its immense supplies, while the whole 115 miles of Long Island is occupied with them.The oyster is one of the lowest forms of the mollusk. Its mouth opens right into its stomach, which is surrounded by its liver, permeated by a yellow liquid, the bile. It may thus be said that they have their stomach and intestine in the liver, the mouth upon the stomach and the opening of the intestine in the back. They have a heart which circulates a colorless blood. They breathe at the bottom of sea, having an organ which separates from the water the small amount of oxygen it contains. Their respiratory organs are two pair of gills, or branchiae, curved and formed by a double series of very delicate canals placed close together, resembling the teeth of a fine comb. This apparatus, like the mouth, is hidden under the fold of the mantle. They have no brain, but a ganglion of nerves, a whitish substance situated near their mouths. From this originate the nerves, which branch off to the region of the liver and stomach; here they re-unite in a second ganglion which is placed behind the liver. The nerves of the mouth and its tentacles originate in the first ganglion, those of the respiratory organs in the second. It has no sense of sightor hearing, the sense of touch is all that it has, and this resides in the tentacles of the mouth. Its taste, if it has any, must be very feeble. Its powers are most limited; imprisoned forever in its shell, it has no power of locomotion, and being without any distinction of sex, its wants or desires must be very few.Still the oyster appears to be a social animal, and loves to gather together in great numbers, so that despite their apparently low grade of intelligence, we cannot say that they have not sympathetic feelings. Uniting as they do both sexes in each individual, the oyster's organs of reproduction are visible only at the period they are in use. Their young are produced from eggs, which are produced between the folds of their mantle, and in the midst of their respiratory organs. The number of these eggs is prodigious. According to some authorities the number produced by a single oyster reaches 10,000,000. Naturalists, however, at present consider this estimate too high, and limit it at about 2,000,000 for each individual. The eggs are yellow, are hatched in the mantle, and when the embryo leaves its parent it can breathe. The spawning time is from June to September. The oyster differs from most shell-fish in that when the young leave the parent they can support themselves; ordinarily the shell-fish throw out their eggs committing them to chance for their protection. In the spawning season an oyster bed is the most interesting place; each oyster is throwing out a whole array of descendants, filling the water with a cloud of living dust, so that the sea is clouded with thespatas it is called.Under the microscope the spat is seen to be provided with a shell, and with vibratory cils which enable it to swim. When the current carries it against any stationary body, it immediately adheres to it, the cils disappear and the young oyster, becoming fixed, commences to develop. It takes three years for them to attain their full size. While the spat isswimming about, before becoming fixed, it is said that if anything alarm them they seek refuge again within the maternal shell. Such prolific production would soon stock the whole sea, were it not for the fact that the young are feeble swimmers, and that millions of them are annually swept away and lost by the current, or fall a prey to the numerous animals which feed upon them.FAGGOTS SUSPENDED TO RECEIVE OYSTER SPAT.The favorite place for the oyster is on the shore, in water not very deep and free from currents; here they are very prolific. The idea of breeding them is as old as the Romans, and to-day the planting of oyster beds, and fishing from them gives occupation to thousands. Some of the oyster beds of France which were nearly exhausted twenty years ago have been made again very productive by attention and care. The plan of suspending faggots upon which the spawn should adhere, has been found very successful. From the Bay of St. Brieuco two faggots, taken up at random, were found to contain about 20,000 young oysters, ranging in size from one to three inches in diameter. Their exhibition excited astonishment; they looked like leafy branches, each leaf being a living oyster.In the island of Re oyster farming is in full operation. It is calculated that the beds contain 600 oysters to the square yard, the majority of marketable condition, making a total of 378,000,000 in these beds alone. In the United States, theproductiveness of the beds is almost inestimable, and yet, despite the immense number of oysters yearly brought to market, the demand continually outstrips the supply. The modern methods of canning have opened a so much wider market, the whole inland country being thus opened to the supply, it is almost impossible to overstock the market.The peculiar green color of the oysters in France, which have been planted in beds, or claries, and which is thought to make their flavor better, arises from some cause, concerning which naturalists differ. It seems, however, to be some kind of disease, arising from the condition of the water in these beds.Oyster fishing is pursued in different ways, in different countries. Around Minorca the diver descends with a hammer in his hand to knock the oysters from the rocks, and brings up generally a dozen or more with each descent. On the English and French coasts the dredge is used. This method is very destructive, since it tears the large and small together from their native spot, and buries many also in the mud. Oysters, as we know them, are of convenient size for making a mouthful; the largest may have to be separated into parts before a delicate person can swallow them, but it is only the largest which have to be submitted to this process, and your real oyster lover has too tender a regard for his favorite mollusk to so maltreat it. On the coast of Coromandel, however, the oysters grow to be as big as soup plates, and larger, the shells of some of them measuring almost two feet across. These shells are frequently used in the Catholic churches of Europe to contain the holy water, placed near the door for the use of the faithful, and are quite as large as big hand basins. A half-dozen such oysters on the half-shell, would make a feast even for the most voracious oyster eater.The oyster beds on the coast of the United States are generally in so shallow water that they can be readily reached withrakes furnished with handles fifteen to twenty feet long. A pair of these are mounted like a gigantic pair of scissors, the pivot being nearer the rakes than the other end of the poles. Taking an end of one of these poles in each hand, the fisherman sinks it to the bottom, opens it, and moves the handles until a supply of oysters is scraped up between the rakes. Then pulling up the instrument, he empties the oysters into the bottom of his boat, and uses his rakes again. Millions of dollar's worth of oysters is thus fished every year, and fleets of small sailing ships are constantly engaged in the traffic along the coast.To an European, the American oyster at first appears enormous, compared with those he is accustomed to. Their flavor also is different; they have not a peculiar coppery taste to which he is accustomed, and which most Americans in Europe dislike at first. A little practice, however, soon enables the European to recognize the merit of our oysters, and they become very fond of them. Both Thackaray and Dickens, during their visits to this country, were loud in their praises of the excellence of the oysters.DREDGING FOR OYSTERS.The pearl oyster (Meleagrina margaritifera), is one of the most interesting and valuable of the varieties of the oyster. The pearls are formed of the same substance which lines the shells of so many shell-fish, and which as nacre, or mother of pearl, is so well known for its iridescent beauty. It is deposited by the animal in very thin layers, and it is the interference of the rays of light in their reflection from this varying surface which produces the phenomena of iridescence. It is easy for any one to satisfy himself of this. Press a piece of wax upon a piece of mother of pearl, or any other iridescent body, and the surface of the wax when removed will itself appear iridescent. It has reproduced the fine lines of the iridescent body. Soap bubbles, being formed of films of the soapy water, attain their brilliant coloring from the same cause. Brass buttons were once fashionable which showed the same colors. They were made by having the polished surface ruled with microscopically fine lines. It was, however, so costly to make them, they cost a guinea each, that they were soon abandoned.A SHELL CONTAINING CHINESE PEARLS.Pearls are the secretion of nacreous material, spread, it is supposed, over some foreign substance which has been introduced into the shell, under the mantle of the mollusk. When the pearls are deposited on the shells, they generally adhere to it, when they originate in the body of the animal they are free. As a rule some foreign body is found in their centre which served as the nucleus for the deposit of the secretion. It may be a sterile egg of the animal itself, or of a fish, or a grain of sand, which was washed in.The Chinese and other nations of the East, take advantage of this fact in natural history, for purposes of profit. They take up the living mollusk, and opening the shell introduce into it glass beads, or small metallic casts, representing some one of their gods, or other objects, and then returning the mollusk tothe water, in time the animal has coated them with mother of pearl. The illustration shows a shell into which small beads have been introduced, and converted into pearls, together with a dozen small figures of Buddha, the Hindoo divinity, seated, which have been covered over with nacre also.The pearls are at first very small, but they increase in size with the yearly deposit of a layer on the original centre. Sometimes they are diaphanous, semi-transparent, lustrous and more or less irridescent, at other times, however, they prove to be dull, obscure, and smoky even. The pearl fisheries are carried on in various places. They are found in the Persian Gulf, on the coast of Arabia, in Japan, on the shores of California, and in the islands of the South Sea. The most important ones are, however, those of the Bay of Bengal, the coast of Ceylon, and elsewhere in the Indian Ocean. Previous to 1795 most of the Indian fisheries were in the hands of the Dutch, but in 1802, after the treaty of Amiens, they passed into the possession of the English. Sometimes the Ceylon fisheries are undertaken by the Government, while at others they are sold to a contractor. In either case, before they begin, the coast is inspected by a Government official, in order to see that the banks are not exhausted by too frequent fishing.The chief supply of mother of pearl is obtained from the fishery in the Gulf of Manaar, a large bay on the northeast of the island of Ceylon. It commences in February or March, and lasts thirty days. Some two hundred and fifty boats are engaged in it, coming for the purpose from all parts of the coast. At ten at night a gun gives the signal for them to set sail, and reaching the ground they commence as soon as the dawn affords sufficient light. Each boat carries ten rowers and ten divers, five of whom rest while the others are engaged. A negro to attend to the odd jobs and chores accompanies each boat.PEARL FISHER IN DANGER.The divers descend from forty to fifty feet, seventy is the utmost they can stand. Thirty seconds is the time they usually remain under water, and the best cannot stay longer than a minute and a half. When the fishing ground is reached a staging, built of the oars, is rigged to project from the boat over the water, and to the edge of this the diving-stones are hung, weighing from fifty to sixty pounds. The diver stands in a stirrup upon this, or if this is wanting upon the stone itself, holding the cord attached to it between his toes, with his left foot he holds the net for the reception of the pearl-oysters. Then, pressing his nostrils firmly with his left hand, and with his right grasping the signal cord, he is let rapidly down to the bottom. As soon as he arrives there, he removes his foot from the stone which is immediately drawn up again. Then throwing himself flat upon the ground, he hastily gathers into his net all the oysters within his reach. When he feels he must return to the surface he pulls the signal cord with a jerk, and is pulled up as quickly as possible. A good diver seeks to avoid straining himself, and so stays under water only the shortest time, seldom more than half aminute, but he will repeat the operation sometimes as much as fifteen or twenty times. The work is very distressing, the increased pressure of the water affects the entire system, and frequently on rising to the surface the water which runs from their ears, nose and mouth is tinged with blood. The effect is also to induce pulmonary diseases, and the divers rarely attain old age. Sharks are also common in these waters, and the divers are not unfrequently destroyed by these rapacious monsters, who are the more attracted by the fact that the divers, for their own convenience, are naked.The work continues until noon, when a second gun gives notice for its cessation. The boats then return with the cargo they have gained, and are received by the proprietors on the shore, who personally superintend their discharge, which must be finished before dark, since anything left over night would most certainly be stolen.The fisheries of Ceylon were formerly very valuable, but at present the banks show signs of exhaustion, from over-fishing most probably. In 1798 they are said to have produced nearly a million dollars' worth of pearls, but now they seldom yield more than a hundred thousand dollars' worth. The inhabitants along the coast of the Bay of Bengal, the Chinese seas, and the islands of Japan, are also engaged in the pearl fishing. Together the yield is estimated at about four millions of dollars.Further west, on the Persian coast, the Arabian gulf and the Muscat shore, as well as in the Red sea, pearls are found.In these latter countries the pearl fishing commences in July, for during this and the next month the sea is usually calm. When the boats have arrived over the bed, they anchor, the water being eight or nine fathoms deep. The divers carry their bag tied around their waists, and plug their nostrils with cotton, then closing their mouths, are sunk by a stone rapidly to the bottom. The pearls obtained from thefisheries on the Arabian coast reach a value of over a million and a half of dollars.Pearl fishing is also carried on, on the coast of South America. Before the Spanish conquest of Mexico the fisheries were situated between Acapulco and the Gulf of Tehuantepec, but since that time other beds have been found near the islands of Cubagua, Margarita and Panama. The yield at first was so promising that flourishing cities grew up in the vicinity of these places, and during the reign of Charles V., pearls to the value of nearly a million of dollars were sent to Spain, but the present yield averages only about three hundred thousand dollars.When the oysters are taken from the boats, they are piled up on grass mats on the shore, and left in the sun. The mollusks soon die, and begin to decompose. In about ten days they are sufficiently putrified to become soft. Then they are thrown into tanks of sea water, opened and washed. The pearls which adhere to the shells are taken off with pinchers; those that are in the body of the animal are secured by passing its substance through a sieve, after boiling the flesh to make it soft. The shells furnish the nacre, which is split off from the rough outside with a sharp instrument, or the outside is dissolved from the mother of pearl by an acid. Three kinds of mother of pearl are known in commerce, as silver face, bastard white and bastard black; the first is the most valuable. The pearls are the most important part of the product. Those which adhere to the shell are always more or less irregular in their shape, and are sold by weight. They are calledbaroques. Those found in the body of the animal are calledvirgin pearls, orparagons, and are round, oval or pyramid shaped. These are sold generally singly; the price varying according to size, lustre, clearness, etc. Months after the shells have been examined, poor natives are seen diligently turning over the putrifying mass which has been cast aside, eagerly searching forsome pearl that has been overlooked; as in our cities the ashes, barrels and gutters are searched by the same wretched class for the refuse of luxury.The pearls are polished by shaking them together in a bag with nacre powder. By this process they are smoothed and polished. Then they are assorted according to sizes by being passed through a series of copper sieves, placed over each other, and pierced with an increasing number of holes, growing smaller. Thus, sieve number twenty has twenty holes in it; fifty, fifty holes, and the last of the series of twelve, one thousand holes. The pearls retained between twenty and eighty are called mill, and are considered to be of the first order. Those between one hundred and eight hundred are vivadoe, and class second. Those which pass through all but the thousand are tool, or seed pearls, and are third. The seed pearls are sold by measure or weight. The larger ones are drilled, strung on a white or blue silk thread, and exposed for sale.In the American fisheries the oysters are opened each separately with a knife, and the animal is pressed between the thumb and finger in the search for pearls. This process takes longer, and is not considered as certain to find them all as that followed in the East, but the nacre and the pearls thus taken from the live animal are fresher and more brilliant than from those oysters which have died and decayed. Other mollusks also furnish pearls, but not in a regular enough supply to justify their fishing. In fact pearls are often found in our common oysters.SHARK FISHING.Fishing for sharks is one of the most exciting kinds of sport, and has the further merit that its success is the destruction of the most destructive inhabitant of the sea; a predatory robber, who spares none that come in his way. The prey in which the shark most delights is, however, man himself. He even manifests, according to some authorities, a preference for Europeans over the Asiatic or the Negro races. A shark who has once enjoyed the luxury of human flesh is said to haunt the neighborhood where he obtained it. He follows a ship from some instinctive feeling, and has been known to leap into a fisherman's boat, or throw himself against a ship in an effort to reach a sailor who had shown himself over the bulwarks. The slave ships during their voyages were constantly followed by sharks, who battled eagerly for the corpses of the unhappy dead which were thrown overboard. In one case it is recorded that a corpse was hung from the yard arm, dangling twenty feet above the water, and was devoured, limb by limb, by a shark, who leaped that distance from the water to obtain his horrid repast.On the African coast the negroes boldly attack the shark in his own element. As his mouth is placed under his head, he has to turn round before he can seize anything, and taking advantage of this, the negro seizes the opportunity to rip him up with a sharp knife.Shark fishing is regularly followed off the coast of Nantucket, for their skins and the oil they furnish. The skins are used for various purposes in the arts. In Norway and Iceland portions of the flesh are dried, and serve as provision for the food of winter.The persistancy with which a shark will follow a vessel at sea leads to their frequently being caught. The hook is of iron, as thick as a man's finger, and six or eight inches long, the point made very sharp. It is fastened with a chain five or six feet long, to prevent the shark's teeth from severing it. Baited with a good sized piece of pork, and fastened to a long line, it is thrown over. Sometimes in his eagerness to catch it the shark will jump from the water, but oftener, having probably learned from experience something about the tricks of men, he is more cautious in taking it. Often he will examine it, swim round it, and manage to get it, without taking the hook also, as often as it is offered to him rebaited. If he, however, swallows the hook with the bait, it still requires some dexterity to catch him; the line must not be jerked prematurely; he must be given time enough to swallow it well, then a good jerk fixes the point of the hook, and the sport commences for everybody but the shark. In hauling him in it is not safe to trust only to the hook; his struggles are so violent and his strength is so great that he may break away. Being hauled therefore to the surface, the next thing is to get the noose of another rope round his body near the tail, or round one of his pectoral fins. This done he may be safely hauled on board, but even then he cannot be approached without danger, since a blow from his tail may prove fatal. In catching sharks off the coast of Nantucket, in smacks, the fishermen haul them to the surface at the side of the boat, and then kill them with blows on the head before taking them on board.CUTTLE FISH MAKING HIS CLOUD.Among the monsters of the deep, none is more terrific in appearance than the cuttle fish. Terrible stories have been told of the magnitude of these sea monsters. Under the name of the Kraken marvelous tales were told of its destruction of ships, one of them, it being said, embracing a three-masted ship in its gigantic arms. Our illustration, however, shows a well authenticated case of the capture of an enormous cuttle fish. An account of the capture was made to the French Academy of Sciences by Lieutenant Bayer, the commander of the French corvette Alecton, who made the capture, and M. Sabin Berthelot, the French Consul at the Canary Islands. While on her course between Teneriffe and Madeira, the Alecton fell in with a large cuttle fish measuring about fifty feet in length, without counting its eight arms, covered with suckers. Its head, its largest part, measured about twenty feet in circumference: its tail consisted of two fleshy lobes or fins. Its weight was estimated at 4,000 pounds. Its color was brickish red, and its flesh was soft and glutinous. The shots which were fired at it passed through it without apparently producing any injury. After it was thus wounded, however, the sea was observed to be covered with foam and blood, and a strong odor of musk was smelt. Harpoons were also cast into it, but they took no hold. Finally, however, one of the harpoons stuck fast, and the sailors succeeded in getting a running noose round the lower part of its body, near the tail. On attempting to haul it on board, the rope cut it in two, the head part disappearing and the tail portion being brought on deck.IDEAL SCENE.—MONSTERS OF THE GREAT DEEP BEFORE THE DELUGE.It is supposed that the animal was either sick, or exhausted from some cause, possibly a recent struggle with some other marine monster, and that on this account it had left its usual haunts on the rocks at the bottom of the sea, since otherwise it would have been more active than it was, or would have discharged the inky cloud, which the cuttle fish has always at its disposal for avoiding its enemies.RED CORAL.DREDGING.CHAPTER LVI.DREDGING IN MODERN TIMES—WHAT IT HAS TAUGHT US—DEEP SEA SOUNDINGS—FIRST ATTEMPTS—IMPLEMENTS USED FOR IT—THE CHANCE FOR INVENTORS.In modern times we have learned a great deal more of the ocean than the ancients knew, from dredging. By this means we have become acquainted not only with the outline of the bottom, but have also become acquainted with the temperature of deep seas, with the varied forms of animal and vegetable life which are present there, and have come to know, with far greater certainty and completeness than ever before, the part which the ocean has played and is still playing in the preparation of the land.By sounding, the ancients, of course, knew the depths of the shallow waters along their coasts. It would be the most natural thing for a sailor to tie a stone to a string, and let it down into the water, when he wanted to know whether it was deep enough to float his vessel, and the same means would also be used to discover whether there were any sunken rocksin such harbors as he was frequenting. But the ocean, to all antiquity, was unfathomable; they dared not attempt to cross it, and of course did not think they could measure its depth. Long after the ocean had been crossed by ships the belief was still current that it was impossible to measure its depth, and this belief was made the stronger by the unsuccessful attempts made in mid ocean to obtain soundings with the ordinary lead and line.Before we arrived at a positive knowledge of the depth of the ocean, scientific men attempted to calculate it by various methods. Laplace, calculating the mean elevation of the land, supposed the sea must be of about equal depth. Young, drawing his deductions from the tides, calculated the depth of the sea. This method has been recently used to calculate the depth of the Pacific. A wave of a certain velocity indicates water of such a depth. In the case of the earthquake of 1854, in Japan, which caused a wave that extended to California, the rate of its progress afforded an indication of the mean depth of the sea it passed over, and authentic soundings taken since have confirmed the general accuracy of the calculation.The ordinary lead used for soundings is a pyramid of lead, the bottom of which has a depression in it, which is filled with tallow; on striking the bottom a little of the sand or mud adheres to this tallow and is brought up to the surface. In this way something is learned about the depth and bottom of the sea, but not enough to satisfy the naturalists, who inquired whether it might not be possible to dredge the bottom of the sea in the ordinary way, and to send down water bottles and registering instruments to settle finally the conditions of the deep waters, and determine with precision the composition and temperature at great depths.An investigation of this kind is beyond the powers of private enterprise. It requires more power and sea skill than naturalists usually have. It is a work for governments. Thatof the United States has contributed fully its share. The coast survey has added a great deal to our knowledge of the deep sea, and the ships of the navy took part in the soundings by which the existence of the plateau across the bed of the North Atlantic, which has been used for the ocean telegraphic cable, was proved.In 1868 the English government provided the vessels and crews for the purpose of conducting deep sea dredgings, under the direction of Dr. Carpenter and Mr. Wyville Thompson. These expeditions have found that it is quite possible to work with certainty, though not with such ease, at the depth of 600 fathoms, as at a depth of 100; and in 1869 it carried on deep sea dredging at a depth of 2,435 fathoms, 14,610 feet, or very nearly three miles, with perfect success. Dredging in such deep water is very trying. Each haul occupied seven or eight hours, and during the whole of this time the constant attention of the commander was necessary, who stood with his hand on the regulator of the accumulator, ready at any moment to ease an undue strain, by a turn of the ship's paddles. The men, stimulated and encouraged by the cordial interest taken by the officers in the operations, worked with a willing spirit; but the labor of taking up three miles of rope, coming up with a heavy strain, was very severe. The rope itself, of the very best Italian hemp, 2 1/2 inches in circumference, with a breaking strain of 2 1/4 tons, looked frayed out and worn, as if it could not have been trusted to stand such an extraordinary ordeal much longer.The ordinary deep sea lead used for soundings weighs from 80 to 120 pounds. The samples of the bottom which it brings up are marked upon the charts as mud, shells, gravel, ooze or sand, thus 2,000 m. sh. s. means mud, shells and sand at 2,000 fathoms; 2,050 oz. st. means ooze and stones at 2,050 fathoms; 2,200 m. s. sh. sc. means mud, sand, shells, and scoriæ, at 2,200 fathoms, and so on. When no bottom is found with the leadit is entered on the chart thus:——3,200, meaning no bottom was reached at that depth.This method of sounding answers very well for comparatively shallow water, but it is useless for depths much over 1,000 fathoms, or six thousand feet. The weight is not sufficient to carry the line rapidly and vertically to the bottom; and if a heavier weight is used, the ordinary sounding line is not strong enough to draw up its own weight, and that of the lead from a great depth, and so breaks. No impulse is felt when the lead touches the bottom, and so the line continues running out, and any attempt to stop it breaks it. In some cases the slack of the line is carried along by currents, and in others it is found that the line has been running out by its own weight and coiling in a tangled mass on top of the lead.These sources of error vitiate the results of very deep soundings. Thus Lieutenant Walsh, of the U.S. schooner Taney, reported 34,000 feet without touching bottom; and the U.S. brig Dolphin used a line 39,000 feet long without reaching bottom. An English ship reported 46,000 feet in the South Atlantic and the U.S. ship Congress 50,000 feet without touching bottom. These are, however, known to be errors, so that no soundings are entered on charts over 4,000 feet, and few over 3,000. The U.S. Navy introduced the first great improvement in deep soundings. This consisted in using a heavy weight and a small line. The weight, a 32 or 68-pound shot, was rapidly run down, and when it touched bottom, which was shown by the sudden change in the rapidity with which the line was run out, the line was cut and the depth estimated from the length of cord remaining on the reel. This, however, cost the loss of the shot and the line for each sounding.One of the first attempts at deep sea dredging was made in 1818, by Sir John Ross, in command of the English navy vessel Isabella, on a voyage for the exploration of Baffin's Bay with a machine of his own invention, which he called a "deepsea clamm." It consisted of a pair of forceps, kept apart by a bolt, and so contrived that when the bolt struck the ground a heavy iron weight slipped down a spindle and closed the forceps, which retained a portion of the mud, sand, or small stones, from the bottom. With this instrument he sounded in 1,050 fathoms, and brought up six pounds of very soft mud, using a whale line, made of the best hemp, and measuring 2 1/2 inches in circumference.The cup lead is another invention. With this there is a pointed cup at the bottom of the lead, fastened to it with a rod upon which a circular plate of leather plays, serving as a cover to the cup. As it strikes the bottom, the cup is driven in the mud, and on hauling up the cover is pressed into the cup by the water, and brings up the mud it contains. The objection to this is that it is too crude; in its passage up, the water washes away the mud, so that only on an average of once in three times does the cup come up with anything in it; and deep sea soundings take too much time, and are too valuable, to admit so large an average of loss.About 1854 Mr. J. M. Brooke, of the U.S. Navy, who was at the time associated with Prof. Maury, so well known for his labor in gathering and diffusing a knowledge of the currents of the ocean, invented a deep sea sounding apparatus, which is known by his name. It is still in use, and all the more recent contrivances have been, to a great extent, only modifications and improvements upon the original idea, that of detatching the weight. The instrument is very simple. A 64-pound shot is cast with a hole in it. An iron rod, with a cavity in its end, fits loosely in the hole in the shot. Two movable arms at the top of the rod are furnished with eyes holding ends of a sling in which the ball hangs. The cavity at the end of the rod is furnished with tallow, and the apparatus is let down. On reaching the bottom, the rod is forced into the mud, the cavity becomes filled with it, and there being no more tension, on the rope holding up the movable arms, they fall, disengage the ends of the sling, and allow the ball to slide down the rod. The rod is then withdrawn, carrying up the portion of the bottom secured in the cavity at its foot, and leaving the ball on the bottom. This apparatus costs a ball each time it is used, and brings up but a small portion of the bottom, which is also apt to be diminished on its way to the top, by the water it passes through.STRIKING THE SEA BOTTOM. BROOK'S DEEP SEA SOUNDING APPARATUS.Commander Dayman, of the English Navy, in 1857 invented an improvement upon Mr. Brooke's original invention. He used iron wire braces to support the sinker, as these detach more easily than slings of rope. The shot he replaced by a cylinder of lead, as offering less surface to the water in its descent, and he fitted the cavity in the bottom of the rod with a valve opening inward. Commander Dayman used the apparatus, with these modifications, in the important series of soundings he made in the North Atlantic, while engaged in surveying the plateau for the ocean telegraphic cable, and reports that it worked well.THE BULLDOG SOUNDING MACHINE.The apparatus known as the bull-dog machine is an adaptation of Sir John Ross' deep-sea clamms, together with Brooke's idea of disengaging the weight. It was invented during the cruise of the English Navy vessel, the Bull-dog, in 1860, and the chief credit for it belongs to the assistant engineer during that cruise, Mr. Steil. A pair of scoops are hinged together like a pair of scissors, the handles represented by B. These are permanently fastened to the sounding rope, F, which is here represented as hanging loose, by the spindle of the scoops. Attached to this spindle is the rope, D, ending in a ring. E represents a pair of tumbler hooks, like those used so generally. C is a heavy weight, of iron or lead, hollow, with a hole large enough for the ring upon D to pass through. B is an elastic ring of India rubber, fitted to the handles of the scoops, and designed to shut them together as soon as theweight, C, which now holds them apart, is removed. When the bottom is reached, the scoops, open, are driven into the ground, the tension on the rope ceases, the tumbler hooks open and release the weight, which falls on its side, and allows the elastic ring to shut the scoops, inclosing a portion of the bottom in which they have been forced. The trouble with this apparatus is its complicated character; pebbles may get in the hinge and prevent the scoops from closing. In all apparatus to be used for such a purpose the greater the simplicity the better, and an invention, which shall at once be simple and effective, capable of bringing up a pound or two from the bottom at a depth of 2,000 fathoms or more, without fail, and without too much trouble, is still a desideratum, and its invention is well worth the attention of the ingenious.Another arrangement, called the Hydra sounding machine, is intended to bring up portions of the bottom and water from the lowest strata reached. It consists of a strong brass tube, which unscrews into four chambers, closed with valves, opening upward, so that in the descent the water passes through them, freely; but when it is commenced to haul up, the pressure of the water closes the valves. This apparatus is also furnished with weights to sink it, which are released, on reaching the bottom, by a similar method to those described. This instrument was used during the deep sea sounding cruise of the Porcupine, and never once failed. Its faults are its complication, and that it brings up only small samples of the bottom. Captain Calver, who used it, could always, when at the greatest depths, distinctly feel the shock of the arrest of the weight upon the bottom communicated to his hand.MASSEY'S SOUNDING MACHINE.Various attempts have been made to construct instruments which should accurately determine the amount of the vertical descent of the lead by self-registering machinery. The most successful and the one most commonly used is Massey's sounding machine. This instrument, in its most improved form, is shown in the accompanying cut. It consists of a heavy oval brass shield, furnished with a ring at each end of its longer axis. To one of these a sounding rope is attached, and to the other, the weight is fastened at about a half fathom below the shield. A set of four brass wings or vanes are set obliquely to an axis, so that, like a windmill or propeller wheels, it shall turn by the force of the water as it descends. This axis communicates its motion to the indicator, which marks the number of revolutions on the dial plate. One of these dials marks every fathom, and the other every fifteen fathoms of descent. This sounding machine answers very well in moderately deep water, and is very valuable for correcting soundings by the lead alone, where deep currents are suspected, as it is designed to register vertical descent alone. In very deep water it is not satisfactory, from some reason which it is difficult to determine. The most probable explanation is that it shares the uncertainty inherent in all instruments using metal wheel work. Their machinery seems to get jammed in some way, under the enormous pressure of the water, at great depths.To ascertain the surface temperature of the water of the sea is simple enough. A bucket of water is drawn up, and a thermometer is placed in it. With an observation of this kind the height of the thermometer in the air should be always noted. Until very recently, however, very little or nothing was known with any certainty about the temperature of the sea at depths below the surface. Yet this is a field of inquiry of very greatimportance in physical geography, since an accurate determination of the temperature at different depths is certainly the best, and frequently the only means, for determining the depth, the width, the direction and general path of the warm ocean currents, which are the chief agents in diffusing the equatorial heat; and more especially of those deeper currents of cold water which return from the poles to supply their places, and complete the watery circulation of the globe. The main cause of this want of accurate knowledge of deep sea temperatures is undoubtedly the defective character of the instruments which have been hitherto employed.The thermometer which has been generally used for making observations on the temperature of deep water is that known as Six's self-regulating thermometer, inclosed in a strong copper case, with valves or apertures above and below, to allow a free passage of the water through the case and over the face of the instrument. This registering thermometer, consists of a glass tube, bent in the form of a U. One arm terminates in a large bulb, entirely filled with a mixture of creosote and water. The bend in the tube contains a column of mercury, and the other arm ends in a small bulb, partly filled with creosote and water, but with a large space empty, or rather filled with the vapor of the mixture and compressed air. A small steel index with a hair tied round it, so as to act like a spring against the side of the tube, and keep the index at any point it may assume, lies free in either arm, among the creosote, floating on the mercury. This thermometer gives its indications only from the expansions and contractions of the liquid in the large full bulb, and consequently is liable to some slight error, from the variations of temperature upon the liquids in other parts of the tube. When the liquid in the large bulb expands, the column of mercury is driven upward toward the half-empty bulb, and the limb of the tube in which it rises is graduated from below, upward, for increasing heat. When the liquidcontracts in the bulb, the mercury rises in this arm of the tube, which is graduated from above downward, but falls in the other arm. When the thermometer is going to be used, the steel indices are drawn down in each limb of the tube, by a strong magnet, till they rest, in each arm, upon the surface of the mercury. When the thermometer is drawn up from deep water, the height at which the lower end of the index stands in each tube indicates the limit to which the index has been driven by the mercury, the extreme of heat or cold to which the instrument has been exposed. Unfortunately, the accuracy of the ordinary Six's thermometer cannot be depended upon beyond a very limited depth, for the glass bulb which contains the expanding fluid yields to the pressure of the water, and compressing the contained fluid, gives an indication higher than is due to temperature alone. This cause of error is not constant, since the amount to which the bulb is compressed depends upon the thickness and quality of the glass. Yet, as in thoroughly well-made thermometers, the error from pressure is pretty constant, it has been proposed to make a scale, from an extended series of observations, which might be used to correct the observations, and thus closely approximate the truth.A better plan has been proposed, and being practically applied, has been found to work very well. This consists in incasing the full bulb in an outer covering of glass, so that there shall be a coating of air between the bulb and the outside coating, and that this air being compressed by the pressure of the water outside, shall thus protect the inside bulb. Observations taken in 1869 with thermometers constructed in this way, as deep as 2,435 fathoms, in no instance gave the least reason to doubt their accuracy. A modification of the metallic thermometer, invented by Mr. Joseph Saxton, of the United States office of weights and measures, for the use of the coast survey, may be thus described. A ribbon of platinum and oneof silver are soldered with silver solder to an intermediate plate of gold, and this compound ribbon is coiled round a central axis of brass, with the silver inside. Silver is the most expansible of the metals under the influence of heat, and platinum nearly the least. Gold holds an intermediate place, and its intervention between the platinum and silver moderates the strain and prevents the coil from cracking. The lower end of the coil is fixed to the brazen axis, while the upper end is fastened to the base of a short cylinder. Any variation of temperature causes the coil to wind or unwind and its motion rotates the axial stem. This motion is increased by multiplying wheels, and is registered upon the dial of the instrument by an index, which pushes before it a registering hand, moving with sufficient friction to retain its place, when pushed forward. The instrument is graduated by experiment. The brass and silver parts are thickly gilt by the electrotype process, so as to prevent their being acted upon by the salt water.The box in which the instrument is protected is open to admit the free passage of the water. This instrument seems to answer very well for moderate depths. Up to six hundred fathoms its error does not exceed a half degree, centigrade; at 1,500 fathoms it rises however to five degrees, quite as much as an unprotected Six thermometer, and the error is not so constant. Instruments which depend for their accuracy upon the working of metal machinery cannot be depended upon when subjected to the great pressure of deep soundings.For taking bottom temperatures at great depths, two or more of the thermometers are lashed to the sounding line at a little distance from each other, a few feet above the sounding instrument. The lead is rapidly run down, and after the bottom is reached an interval of five or ten minutes is allowed before hauling in. In taking serial temperature soundings, which are to determine the temperature at certain intervals of depth the thermometers are lashed to an ordinary deep sealead, the required quantity of line for each observation of the series ran out, and the thermometers and lead are hove each time. The operation is very tedious; a series of such observations in the Bay of Biscay, where the depth was 850 fathoms and the temperature taken for every fifty fathoms, occupied a whole day. In taking bottom temperatures with a self-registering thermometer, the instrument of course simply indicates the lowest temperature to which it has been subjected, so that if the bottom stratum is warmer than any other through which the thermometer has passed, the result would be erroneous. This is only to be tested by serial observations; but from these it appears, wherever they have been made, that the temperature sinks gradually, sometimes very steadily, sometimes irregularly from the surface to the bottom, the bottom water being always the coldest.Several important facts of very general application in physical geography have been settled by the deep sea temperature soundings which have been recently made, and the theories formerly held on this subject shown to be erroneous. It has been shown that in nature, as in the experiments of M. Despretz, sea water does not share in the peculiarities of fresh water, which, as has been long known, attains its maximum density at four degrees, centigrade; but like most other liquids increases in density to its freezing point; and it has also been shown that, owing to the movement of great bodies of water at different temperatures in different directions, we may have in close proximity two ocean areas with totally different bottom climates, a fact which, taken along with the discovery of abundant animal life at all depths, has most important bearings upon the distribution of marine life, and upon the interpretation of palaeontological data.Mr. Wyville Thompson, who conducted the series of important deep sea soundings undertaken in the Porcupine, says very truly, "It had a strange interest to see these little instruments,upon whose construction so much skilled labor and consideration had been lavished, consigned to their long and hazardous journey, and their return eagerly watched for by a knot of thoughtful men, standing, note-book in hand, ready to register this first message, which should throw so much light upon the physical conditions of a hitherto unknown world."Up to the middle of the last century the little that was known of the inhabitants of the bottom of the sea beyond low water mark, appears to have been gathered almost entirely from the few objects thrown up on the beaches after storms or from chance specimens brought up on sounding lines, or by fishermen engaged in sea fishing or dredging for oysters. From this last source, however, it was almost impossible to obtain specimens, since the fishermen were superstitious concerning bringing home anything but the regular objects of their industry, and from a fear that the singular things which sometimes they drew up might be devils in disguise, with possibly the power to injure the success of their business, threw them again, as soon as caught, back into the sea. Such superstitions are dying out, and in fact so singular are many of the animals hid in the depths of the sea; their forms and general air are so different from anything which the fishermen were used to see, that we can hardly wonder at the fear they excited. When, however, the attention of naturalists was turned toward the sea, they used the dredge such as was used by the oyster fishermen, and all the dredges now in use are simply modifications of this.The dredge for deep sea operations is made with two scrapers, so that it shall always present a scraping surface to the bottom, however it may fall. The iron work should be of the very best, and weighing about twenty pounds. The bag is about two feet deep, and is a hand-made net of very strong twine, the meshes half an inch to the side. As so open a net-work wouldlet many small things through, the bottom of the bag, to the height of about nine inches, is lined with a light open kind of canvas, called by the sailors "bread-bag." Raw hides have been used for making the dredge bag, but, though very strong, they are apt to become too much so to another sense than touch. It is bad economy to use too light a rope in such operations, and best to fasten it to only one arm of the dredge, the eyes of the two arms being tied together with a thinner cord. In case, then, the dredge becomes entangled at the bottom, this cord will break first, and thus releasing one of the arms of the dredge, may so change the direction of the strain upon the rope as to free the dredge itself.Dredging in deep water, that is, at depths beyond 200 fathoms, is a matter of some difficulty, and can hardly be done with the ordinary machinery at the disposal of amateurs. The description of the apparatus used in the Porcupine, in 1869 and '70, on her dredging cruise in the Bay of Biscay, will show what is necessary. These arrangements are also shown in the cut. This vessel, a gun-boat of the English navy, of 382 tons, was fitted out specially for this work. Amidships she was furnished with a double cylinder donkey-engine, of about twelve horse-power, with drums of various sizes, large and small. The large drum was generally used, except when the cord was too heavy, and brought up the rope at a uniform rate of more than a foot a second. A powerful derrick projected over the port bow, and another, not so strong, over the stern. Either of these was used for dredging, but the one at the stern was generally used for soundings. The arrangement for stowing away the dredge rope was such as made its manipulation singularly easy, notwithstanding its great weight, about 5,500 pounds. A row of some twenty large pins of iron, about two feet and a half long, projected over one side of the quarterdeck, rising obliquely from the top of the bulwark. Each of these held a coil of from two to three hundred fathoms, and the rope was coiled continuously along the whole row. When the dredge was going down, the rope was taken rapidly by the men from these pins in succession, beginning from the one nearest the dredging derrick, and in hauling up a relay of men carried the rope from the drum of the donkey-engine and laid it in coils on the pins, in reverse order. The length of the dredge rope was 3,000 fathoms, nearly three and a half miles. Of this, 2,000 fathoms were hawser-laid, of the best Russian hemp, 2 1/2 inches in circumference, with a breaking strain of 2 1/4 tons. The 1,000 fathoms next the dredge were hawser laid, 2 inches in circumference. Russia hemp seems to be the best material for such a purpose. Manilla is considerably stronger for a steady pull, but is more likely to break at a kink.THE STERN OF THE PORCUPINE.The frame of the largest dredge used weighed 225 pounds. The bag was double, the outside of strong twine netting, lined with canvass. Three sinkers, one of 100 pounds, and two of 56 pounds each, were attached to the dredge rope at 500 fathoms from the dredge. A description of the sounding made in the Bay of Biscay on the 22d of July, 1869, will give an idea of the process. When the depth had been ascertained, the dredge was let go about 4:45 p.m., the vessel drifting slowly before a moderate breeze. At 5:50 p.m. the whole 3,000 fathoms of rope were out. While the dredge is going down the vessel drifts gradually to leeward; and when the whole 3,000 fathoms of rope are out, she has moved so as to make the line from the dredge slant. The vessel now steams slowly to windward, and is then allowed to drift again before the wind. The tension of the vessel's motion, thus instead of acting immediately on the dredge, now drags forward the weight, so that the dredging is carried on from the weight and not directly from the vessel The dredge is thus quietly pulled along, with the lip scraping the bottom, in the position it naturally assumes from the center of weight of its iron frame and arms. If, on the contrary, the weights were hung close tothe dredge, and the dredge was dragged directly from the vessel, owing to the great weight and spring of the rope the arms would be continually lifted up, and the lip of the dredge be prevented from scraping. In very deep water this operation of steaming up to windward until the dredge rope is nearly perpendicular, after drifting for half an hour or so to leeward, is usually repeated three or four times. At 8:50 p.m. hauling-in is commenced, and the donkey-engine delivers the rope at a little more than a foot a second. A few moments before 1 o'clock in the morning the weights appear, and a little after one, eight hours after it was cast, the dredge appears and is safely landed on deck, having in the meantime made a journey of over eight miles. The dredge, as the result of this haul, contained 1 1/2 hundred weight of characteristic pale grey Atlantic ooze. The total weight brought up by the engine was as follows:2,000 fathoms of rope,4,0001,000 " "1,5005,500Weight of rope reduced to 1/4 in water1,375Dredge and bag275Ooze168Weight attached2242,042pounds.In many of the dredgings at all depths it was found that while few objects of interest were brought up within the dredge, many echinoderms, corals and sponges came to the surface sticking to the outside of the dredge bag, and even to the first few fathoms of the rope. The experiment was therefore tried of fastening to a rod attached to the bottom of the dredge bag, a half dozen swabs, such bundles of hemp as are used on ship-board for washing the decks. The result was marvelous; the tangled hemp brought up everything rough and movable that came in its way, and swept the bottom of the ocean as it would have swept the deck. So successful was this experiment, that the hempen tangles are now regarded asan essential adjunct to the dredge, and nearly as important as the dredge itself, and when the ground is too rough for using the dredge, the tangles alone are used.The mollusca have the best chance of being caught in the dredge; their shells are comparatively small bodies mixed with the stones on the bottom, and they enter the dredge with these. Echinoderms, corals and sponges, on the contrary, are bulky objects, and are frequently partially buried in the mud, or more or less firmly attached, so that the dredge generally misses them. With the tangles it is the reverse, the smooth heavy shells are rarely brought up, while the tangles are frequently loaded with specimens; on one occasion not less than 20,000 examples came up on the tangles in a single haul.In the Porcupine both derricks were furnished with accumulators, which were found of great value. The block through which the sounding line or dredging rope passed was not attached directly to the derrick, but to a rope which passed through an eye at the end of the spar, and was fixed to a bitt on the deck. On a bight of this rope, between the block and the bitt, the accumulator was lashed. This consists of thirty or forty, or more, vulcanized india-rubber springs, fastened together at the two extremities, and kept free from each other by being passed through holes in two wooden ends like barrel heads. The loop of the rope is made long enough to permit the accumulator to stretch to double or treble its length, but it is arrested far within its breaking point. The accumulator is valuable in the first place as indicating roughly the amount of strain upon the line; and in order that it may do so with some degree of accuracy it is so arranged as to play along the derrick, which is graduated, from trial, to the number of hundred weights of strain indicated by the greater or less extension of the accumulator; but its more important function is to take off the suddenness of the strain on the line when the vessel is pitching. The friction of one or two milesof cord in the water is so great as to prevent its yielding to a sudden jerk, such as is given to the attached end when the vessel rises to a sea, and the line is apt to snap.The results which have been gained by deep sea dredging are so important that the English Government recently fitted out another vessel, the Challenger, for such a cruise, with every appliance. This vessel is now due in New York.AQUARIUM.
STAR FISH.CHAPTER LV.THE OCEAN AS A FIELD—THE VARIOUS CROPS IT YIELDS—THE SPONGE—TRANSPLANTING SPONGES—CORAL FISHING—THE DISCOVERY OF THE NATURE OF CORAL—ITS RECEPTION BY NATURALISTS—OYSTER FISHERY—THE OYSTER A SOCIAL ANIMAL—THE YOUNG OYSTER—OYSTER CULTURE—DREDGING FOR OYSTERS—THE AMERICAN OYSTER FISHERY—PEARL OYSTERS—PEARL FISHERIES—THEIR VALUE—SHARK FISHING—CUTTLE FISHING.Though the ocean may appear to be a barren waste of water to the farmer, it has by no means this aspect to the fisherman. To him it is the field in which he labors, and the crops he gathers from it are as diversified in character, and as important for satisfying the demands of the world, as those which the farmer raises. And further than this, the labors of the fisherman have helped to increase our knowledge of the composition and character of the sea, of the habits of the organized beings found in it, as the labors of the farmer have done the same thing for the soil, and the products which it bears.In considering the various fisheries of the ocean, naturally that of the sponge, as one of the lowest forms of animal life, comes first in order. Science is hardly yet decided in its views concerning the organization and development of these obscure and complex creatures, and despite the investigations of modern naturalists, their position in the scale of animal life is still problematical, and their internal organization is still known only imperfectly. Dr. Bowerbank in his work on British Sponges, published in 1866, describes nearly 200 species, but this number by no means includes them all. They are of all sizes, and of all possible diversity of shape. At present the chief sponge fishing is carried on in the Grecian Archipelago and on the coast of Syria. The boat's crew consists of four or five men who, between June and October, seek the sponges under the cliffs and ledges of the rocks. Those obtained in shallow waters are considered inferior; the best are obtained at a depth ranging from twenty to thirty fathoms. The poorer sponges are taken from the shallow waters with harpoons, but are injured by this method of capture. The others are taken by hand. The diver descends to the bottom, and can stay there from a minute to a minute and a half, and carefully detaches the sponges from the rocks with a knife.SPONGE FISHING.Sponge fishing is also carried on in other parts of the Mediterranean, but without any foresight, so that the sponges will, in time, be exhausted. To guard against this contingency, it has been proposed to transplant and acclimatize the sponges upon the coast of France and Algeria, where the composition of the water is the same as that upon the coast of Syria, and where the difference of temperature would prove no impediment to their flourishing. In fact, the farther north the sponges grow, the finer and compacter are their tissue. By use of a submarine boat, supplied with air by a force-pump, it was proposed to collect such specimens, as were best suited for the purpose, removing the rocks with them; and also to collect the young sponges, during the months of April and May, shortly after they have commenced their independent existence, and before they have anchored themselves to some permanent abode, and transport them to a favorable locality. The French Acclimatization Society, in 1862, gave a commission to M. Lamiral, who had passed years in the study of sponges, and who has published an excellent work upon their habits, to collect the germs, and transplant them to the coast of France.Though up to this time, the attempts which have been made to do this have not met with perfect success, yet the results already gained, show that with further experience, perseverance will attain its desired end.Sponges are also fished for in the Red Sea. On the Bahama Banks, and in the Gulf of Mexico, sponges are taken by Mexicans, Spaniards, and Americans, in shallow water. A mast is sunk at the side of the boat, and the diver descends this; gathering the sponges found near the bottom of the pole.Next in order of fishing in deep sea, comes coral fishing. The ancients believed that the coral was a plant, but it is now known that the coral is constructed by a family of polyps living together, and constituting a polypidom. It abounds in the waters of the Mediterranean where upon rocky beds like a submarine forest, the red coral, the most brilliant and celebrated of all coral, grows at various depths, rarely less than five fathoms, or more than one hundred. Each polypidom resembles a red leafless shrub, bearing delicate little star-shaped white flowers. The branches and trunk of this little tree, are the parts common to the family, the flowers are the individual polyps. The branches show a soft, reticulated crust, or bark, full of small holes, which are the cells of the polyps and they are permeated by a milky juice. Beneath the crust is the coral, hard as marble, and remarkable for its striped surface, its red color, and the fine polish it will take. The fishing is chiefly carried on by sailors from Genoa, Leghorn, and Naples, and is a very laborious occupation. The barks engaged in it are small, ranging from ten to fifteen tons. The coral is fished with an apparatus called an engine, consisting of cross bars of wood tied and bolted together at the centre. Below this is a large stone with nets or bags attached. Each engine has a number of these nets, and when let down into the sea, they spread out. The coral grows on the tops of the rocks, and the object is to scrape it off into these bags. By experience, the fishermen come to learn the favorable places for capturing the coral. When such a spot is reached, the engine is thrown overboard, and as soon as it reaches the bottom, the speed of the vessel is slackened, and the capstan, for hauling it up is manned. In this way the engine is dragged over the bottom, becomes entangled with the rocks, and the nets catch the coral. Sometimes rocks of large size are brought on board.CORAL FISHING OFF THE COAST OF SICILY.Up to the last century the opinion of antiquity that coral was a vegetable product was accepted by all naturalists, though no one attempted an explanation how it grew. This opinion was confirmed when the Count de Marsigli announced his discovery of the flowers of the coral plant, and this announcement was considered the final proof of the vegetable origin of coral. In 1723, however, Jean André de Peyssonnel, a pupil of Marsigli's, and a student of medicine and natural history at Paris, was sent to Marseilles, his native place, by the Academy of Sciences, to study the coral in its living condition, and continued his studies on the northern coast of Africa, where he was sent by the French Government.He soon discovered, by a series of careful and delicate experiments, that the coral was an animal product, and that the supposed flowers were the expanded little animals who build up the coral, and who form one of the lowest forms in the series of organized life on the globe. Peyssonnel says: "I put the flower of the coral in vases full of sea-water, and I saw that what had been taken for a flower of this pretended plant was, in truth, only an animal, like a sea nettle or polyp, I had the pleasure of seeing the feet of the creature move about, and having put the vase full of water, which contained the coral, in a gentle heat over the fire, all the small animals seemed to expand. The polyp extended his feet, and showed what M. de Marsigli and I had taken for the petals of a flower. The calyx of this pretended flower, in short, was the animal, which advanced and issued out of his cell."This discovery was received by the naturalists of the time with contempt and ridicule; so much so that Peyssonnel, disgusted, retired into obscurity, leaving his manuscripts in the Museum of Natural History in Paris, where they still remain, unpublished. Before his death, however, in his retirement, he had the satisfaction of seeing his views accepted, and some of those who had most ridiculed them on their first presentation, become the most enthusiastic and effective advocates of them.Besides the coral fished for as we have described, the coral polyp constructs islands, and carries on labors which very materially affect the condition of the ocean and the form of the land, concerning which we will have occasion to speak else where.Another fishery which may be fitly mentioned here is the oyster fishery. There are several varieties of the oyster. Those usually eaten in France are the common oyster (Ostrea edulis), and the horse foot oyster (O. hippopus). The oysters of the Mediterranean are the rose-colored oyster (O. rosacea), and the milky oyster (O. lacteola), with the small and little known crested oyster (O. instata), and the folded oyster (O. plicata). On the Corsican coast the oysters are called foliate (Olamleosa). In France the Cancale and Ostend oysters are chiefly noted. When the first of these has been fed for some time in the parks or beds, and has assumed a greenish color, it is known as the Narenna oyster, from the name of the park in the Bay of Scudre.Natural oyster beds occur in every sea where the coast affords the proper conditions with a shelving and not too rocky bottom. In France the beds of Rochelle, Rochefort, the isles of Re and Oleron, the bay of St. Brieuc, Cancale and Granville are the most famous. On the Danish coast there are forty or fifty beds on the west coast of Schleswig, the best lying between the small islands of Sylt, Amzon, Fohr, Pelworm and Nordstrand. The oyster beds of England extendfrom Gravesend, in the estuary of the Thames and midway along the Kentish coast, and in the estuary of the Coluc and other small streams on the Essex coast. The Frith of Forth is also famous for its oyster beds. The product of these beds has diminished in recent times; according to some authorities from too improvident and persistent dredging, but Mr. Buckland attributes the decrease in the yield to sudden changes in the temperature at the critical period when the spat, or young oysters, are just formed, rather than to over-dredging.The United States is more abundantly furnished with oyster beds than any other country. They extend along almost the entire coast. Those of Virginia are estimated to comprise nearly 2,000,000 of acres. The sea-board of Georgia is famous for its immense supplies, while the whole 115 miles of Long Island is occupied with them.The oyster is one of the lowest forms of the mollusk. Its mouth opens right into its stomach, which is surrounded by its liver, permeated by a yellow liquid, the bile. It may thus be said that they have their stomach and intestine in the liver, the mouth upon the stomach and the opening of the intestine in the back. They have a heart which circulates a colorless blood. They breathe at the bottom of sea, having an organ which separates from the water the small amount of oxygen it contains. Their respiratory organs are two pair of gills, or branchiae, curved and formed by a double series of very delicate canals placed close together, resembling the teeth of a fine comb. This apparatus, like the mouth, is hidden under the fold of the mantle. They have no brain, but a ganglion of nerves, a whitish substance situated near their mouths. From this originate the nerves, which branch off to the region of the liver and stomach; here they re-unite in a second ganglion which is placed behind the liver. The nerves of the mouth and its tentacles originate in the first ganglion, those of the respiratory organs in the second. It has no sense of sightor hearing, the sense of touch is all that it has, and this resides in the tentacles of the mouth. Its taste, if it has any, must be very feeble. Its powers are most limited; imprisoned forever in its shell, it has no power of locomotion, and being without any distinction of sex, its wants or desires must be very few.Still the oyster appears to be a social animal, and loves to gather together in great numbers, so that despite their apparently low grade of intelligence, we cannot say that they have not sympathetic feelings. Uniting as they do both sexes in each individual, the oyster's organs of reproduction are visible only at the period they are in use. Their young are produced from eggs, which are produced between the folds of their mantle, and in the midst of their respiratory organs. The number of these eggs is prodigious. According to some authorities the number produced by a single oyster reaches 10,000,000. Naturalists, however, at present consider this estimate too high, and limit it at about 2,000,000 for each individual. The eggs are yellow, are hatched in the mantle, and when the embryo leaves its parent it can breathe. The spawning time is from June to September. The oyster differs from most shell-fish in that when the young leave the parent they can support themselves; ordinarily the shell-fish throw out their eggs committing them to chance for their protection. In the spawning season an oyster bed is the most interesting place; each oyster is throwing out a whole array of descendants, filling the water with a cloud of living dust, so that the sea is clouded with thespatas it is called.Under the microscope the spat is seen to be provided with a shell, and with vibratory cils which enable it to swim. When the current carries it against any stationary body, it immediately adheres to it, the cils disappear and the young oyster, becoming fixed, commences to develop. It takes three years for them to attain their full size. While the spat isswimming about, before becoming fixed, it is said that if anything alarm them they seek refuge again within the maternal shell. Such prolific production would soon stock the whole sea, were it not for the fact that the young are feeble swimmers, and that millions of them are annually swept away and lost by the current, or fall a prey to the numerous animals which feed upon them.FAGGOTS SUSPENDED TO RECEIVE OYSTER SPAT.The favorite place for the oyster is on the shore, in water not very deep and free from currents; here they are very prolific. The idea of breeding them is as old as the Romans, and to-day the planting of oyster beds, and fishing from them gives occupation to thousands. Some of the oyster beds of France which were nearly exhausted twenty years ago have been made again very productive by attention and care. The plan of suspending faggots upon which the spawn should adhere, has been found very successful. From the Bay of St. Brieuco two faggots, taken up at random, were found to contain about 20,000 young oysters, ranging in size from one to three inches in diameter. Their exhibition excited astonishment; they looked like leafy branches, each leaf being a living oyster.In the island of Re oyster farming is in full operation. It is calculated that the beds contain 600 oysters to the square yard, the majority of marketable condition, making a total of 378,000,000 in these beds alone. In the United States, theproductiveness of the beds is almost inestimable, and yet, despite the immense number of oysters yearly brought to market, the demand continually outstrips the supply. The modern methods of canning have opened a so much wider market, the whole inland country being thus opened to the supply, it is almost impossible to overstock the market.The peculiar green color of the oysters in France, which have been planted in beds, or claries, and which is thought to make their flavor better, arises from some cause, concerning which naturalists differ. It seems, however, to be some kind of disease, arising from the condition of the water in these beds.Oyster fishing is pursued in different ways, in different countries. Around Minorca the diver descends with a hammer in his hand to knock the oysters from the rocks, and brings up generally a dozen or more with each descent. On the English and French coasts the dredge is used. This method is very destructive, since it tears the large and small together from their native spot, and buries many also in the mud. Oysters, as we know them, are of convenient size for making a mouthful; the largest may have to be separated into parts before a delicate person can swallow them, but it is only the largest which have to be submitted to this process, and your real oyster lover has too tender a regard for his favorite mollusk to so maltreat it. On the coast of Coromandel, however, the oysters grow to be as big as soup plates, and larger, the shells of some of them measuring almost two feet across. These shells are frequently used in the Catholic churches of Europe to contain the holy water, placed near the door for the use of the faithful, and are quite as large as big hand basins. A half-dozen such oysters on the half-shell, would make a feast even for the most voracious oyster eater.The oyster beds on the coast of the United States are generally in so shallow water that they can be readily reached withrakes furnished with handles fifteen to twenty feet long. A pair of these are mounted like a gigantic pair of scissors, the pivot being nearer the rakes than the other end of the poles. Taking an end of one of these poles in each hand, the fisherman sinks it to the bottom, opens it, and moves the handles until a supply of oysters is scraped up between the rakes. Then pulling up the instrument, he empties the oysters into the bottom of his boat, and uses his rakes again. Millions of dollar's worth of oysters is thus fished every year, and fleets of small sailing ships are constantly engaged in the traffic along the coast.To an European, the American oyster at first appears enormous, compared with those he is accustomed to. Their flavor also is different; they have not a peculiar coppery taste to which he is accustomed, and which most Americans in Europe dislike at first. A little practice, however, soon enables the European to recognize the merit of our oysters, and they become very fond of them. Both Thackaray and Dickens, during their visits to this country, were loud in their praises of the excellence of the oysters.DREDGING FOR OYSTERS.The pearl oyster (Meleagrina margaritifera), is one of the most interesting and valuable of the varieties of the oyster. The pearls are formed of the same substance which lines the shells of so many shell-fish, and which as nacre, or mother of pearl, is so well known for its iridescent beauty. It is deposited by the animal in very thin layers, and it is the interference of the rays of light in their reflection from this varying surface which produces the phenomena of iridescence. It is easy for any one to satisfy himself of this. Press a piece of wax upon a piece of mother of pearl, or any other iridescent body, and the surface of the wax when removed will itself appear iridescent. It has reproduced the fine lines of the iridescent body. Soap bubbles, being formed of films of the soapy water, attain their brilliant coloring from the same cause. Brass buttons were once fashionable which showed the same colors. They were made by having the polished surface ruled with microscopically fine lines. It was, however, so costly to make them, they cost a guinea each, that they were soon abandoned.A SHELL CONTAINING CHINESE PEARLS.Pearls are the secretion of nacreous material, spread, it is supposed, over some foreign substance which has been introduced into the shell, under the mantle of the mollusk. When the pearls are deposited on the shells, they generally adhere to it, when they originate in the body of the animal they are free. As a rule some foreign body is found in their centre which served as the nucleus for the deposit of the secretion. It may be a sterile egg of the animal itself, or of a fish, or a grain of sand, which was washed in.The Chinese and other nations of the East, take advantage of this fact in natural history, for purposes of profit. They take up the living mollusk, and opening the shell introduce into it glass beads, or small metallic casts, representing some one of their gods, or other objects, and then returning the mollusk tothe water, in time the animal has coated them with mother of pearl. The illustration shows a shell into which small beads have been introduced, and converted into pearls, together with a dozen small figures of Buddha, the Hindoo divinity, seated, which have been covered over with nacre also.The pearls are at first very small, but they increase in size with the yearly deposit of a layer on the original centre. Sometimes they are diaphanous, semi-transparent, lustrous and more or less irridescent, at other times, however, they prove to be dull, obscure, and smoky even. The pearl fisheries are carried on in various places. They are found in the Persian Gulf, on the coast of Arabia, in Japan, on the shores of California, and in the islands of the South Sea. The most important ones are, however, those of the Bay of Bengal, the coast of Ceylon, and elsewhere in the Indian Ocean. Previous to 1795 most of the Indian fisheries were in the hands of the Dutch, but in 1802, after the treaty of Amiens, they passed into the possession of the English. Sometimes the Ceylon fisheries are undertaken by the Government, while at others they are sold to a contractor. In either case, before they begin, the coast is inspected by a Government official, in order to see that the banks are not exhausted by too frequent fishing.The chief supply of mother of pearl is obtained from the fishery in the Gulf of Manaar, a large bay on the northeast of the island of Ceylon. It commences in February or March, and lasts thirty days. Some two hundred and fifty boats are engaged in it, coming for the purpose from all parts of the coast. At ten at night a gun gives the signal for them to set sail, and reaching the ground they commence as soon as the dawn affords sufficient light. Each boat carries ten rowers and ten divers, five of whom rest while the others are engaged. A negro to attend to the odd jobs and chores accompanies each boat.PEARL FISHER IN DANGER.The divers descend from forty to fifty feet, seventy is the utmost they can stand. Thirty seconds is the time they usually remain under water, and the best cannot stay longer than a minute and a half. When the fishing ground is reached a staging, built of the oars, is rigged to project from the boat over the water, and to the edge of this the diving-stones are hung, weighing from fifty to sixty pounds. The diver stands in a stirrup upon this, or if this is wanting upon the stone itself, holding the cord attached to it between his toes, with his left foot he holds the net for the reception of the pearl-oysters. Then, pressing his nostrils firmly with his left hand, and with his right grasping the signal cord, he is let rapidly down to the bottom. As soon as he arrives there, he removes his foot from the stone which is immediately drawn up again. Then throwing himself flat upon the ground, he hastily gathers into his net all the oysters within his reach. When he feels he must return to the surface he pulls the signal cord with a jerk, and is pulled up as quickly as possible. A good diver seeks to avoid straining himself, and so stays under water only the shortest time, seldom more than half aminute, but he will repeat the operation sometimes as much as fifteen or twenty times. The work is very distressing, the increased pressure of the water affects the entire system, and frequently on rising to the surface the water which runs from their ears, nose and mouth is tinged with blood. The effect is also to induce pulmonary diseases, and the divers rarely attain old age. Sharks are also common in these waters, and the divers are not unfrequently destroyed by these rapacious monsters, who are the more attracted by the fact that the divers, for their own convenience, are naked.The work continues until noon, when a second gun gives notice for its cessation. The boats then return with the cargo they have gained, and are received by the proprietors on the shore, who personally superintend their discharge, which must be finished before dark, since anything left over night would most certainly be stolen.The fisheries of Ceylon were formerly very valuable, but at present the banks show signs of exhaustion, from over-fishing most probably. In 1798 they are said to have produced nearly a million dollars' worth of pearls, but now they seldom yield more than a hundred thousand dollars' worth. The inhabitants along the coast of the Bay of Bengal, the Chinese seas, and the islands of Japan, are also engaged in the pearl fishing. Together the yield is estimated at about four millions of dollars.Further west, on the Persian coast, the Arabian gulf and the Muscat shore, as well as in the Red sea, pearls are found.In these latter countries the pearl fishing commences in July, for during this and the next month the sea is usually calm. When the boats have arrived over the bed, they anchor, the water being eight or nine fathoms deep. The divers carry their bag tied around their waists, and plug their nostrils with cotton, then closing their mouths, are sunk by a stone rapidly to the bottom. The pearls obtained from thefisheries on the Arabian coast reach a value of over a million and a half of dollars.Pearl fishing is also carried on, on the coast of South America. Before the Spanish conquest of Mexico the fisheries were situated between Acapulco and the Gulf of Tehuantepec, but since that time other beds have been found near the islands of Cubagua, Margarita and Panama. The yield at first was so promising that flourishing cities grew up in the vicinity of these places, and during the reign of Charles V., pearls to the value of nearly a million of dollars were sent to Spain, but the present yield averages only about three hundred thousand dollars.When the oysters are taken from the boats, they are piled up on grass mats on the shore, and left in the sun. The mollusks soon die, and begin to decompose. In about ten days they are sufficiently putrified to become soft. Then they are thrown into tanks of sea water, opened and washed. The pearls which adhere to the shells are taken off with pinchers; those that are in the body of the animal are secured by passing its substance through a sieve, after boiling the flesh to make it soft. The shells furnish the nacre, which is split off from the rough outside with a sharp instrument, or the outside is dissolved from the mother of pearl by an acid. Three kinds of mother of pearl are known in commerce, as silver face, bastard white and bastard black; the first is the most valuable. The pearls are the most important part of the product. Those which adhere to the shell are always more or less irregular in their shape, and are sold by weight. They are calledbaroques. Those found in the body of the animal are calledvirgin pearls, orparagons, and are round, oval or pyramid shaped. These are sold generally singly; the price varying according to size, lustre, clearness, etc. Months after the shells have been examined, poor natives are seen diligently turning over the putrifying mass which has been cast aside, eagerly searching forsome pearl that has been overlooked; as in our cities the ashes, barrels and gutters are searched by the same wretched class for the refuse of luxury.The pearls are polished by shaking them together in a bag with nacre powder. By this process they are smoothed and polished. Then they are assorted according to sizes by being passed through a series of copper sieves, placed over each other, and pierced with an increasing number of holes, growing smaller. Thus, sieve number twenty has twenty holes in it; fifty, fifty holes, and the last of the series of twelve, one thousand holes. The pearls retained between twenty and eighty are called mill, and are considered to be of the first order. Those between one hundred and eight hundred are vivadoe, and class second. Those which pass through all but the thousand are tool, or seed pearls, and are third. The seed pearls are sold by measure or weight. The larger ones are drilled, strung on a white or blue silk thread, and exposed for sale.In the American fisheries the oysters are opened each separately with a knife, and the animal is pressed between the thumb and finger in the search for pearls. This process takes longer, and is not considered as certain to find them all as that followed in the East, but the nacre and the pearls thus taken from the live animal are fresher and more brilliant than from those oysters which have died and decayed. Other mollusks also furnish pearls, but not in a regular enough supply to justify their fishing. In fact pearls are often found in our common oysters.SHARK FISHING.Fishing for sharks is one of the most exciting kinds of sport, and has the further merit that its success is the destruction of the most destructive inhabitant of the sea; a predatory robber, who spares none that come in his way. The prey in which the shark most delights is, however, man himself. He even manifests, according to some authorities, a preference for Europeans over the Asiatic or the Negro races. A shark who has once enjoyed the luxury of human flesh is said to haunt the neighborhood where he obtained it. He follows a ship from some instinctive feeling, and has been known to leap into a fisherman's boat, or throw himself against a ship in an effort to reach a sailor who had shown himself over the bulwarks. The slave ships during their voyages were constantly followed by sharks, who battled eagerly for the corpses of the unhappy dead which were thrown overboard. In one case it is recorded that a corpse was hung from the yard arm, dangling twenty feet above the water, and was devoured, limb by limb, by a shark, who leaped that distance from the water to obtain his horrid repast.On the African coast the negroes boldly attack the shark in his own element. As his mouth is placed under his head, he has to turn round before he can seize anything, and taking advantage of this, the negro seizes the opportunity to rip him up with a sharp knife.Shark fishing is regularly followed off the coast of Nantucket, for their skins and the oil they furnish. The skins are used for various purposes in the arts. In Norway and Iceland portions of the flesh are dried, and serve as provision for the food of winter.The persistancy with which a shark will follow a vessel at sea leads to their frequently being caught. The hook is of iron, as thick as a man's finger, and six or eight inches long, the point made very sharp. It is fastened with a chain five or six feet long, to prevent the shark's teeth from severing it. Baited with a good sized piece of pork, and fastened to a long line, it is thrown over. Sometimes in his eagerness to catch it the shark will jump from the water, but oftener, having probably learned from experience something about the tricks of men, he is more cautious in taking it. Often he will examine it, swim round it, and manage to get it, without taking the hook also, as often as it is offered to him rebaited. If he, however, swallows the hook with the bait, it still requires some dexterity to catch him; the line must not be jerked prematurely; he must be given time enough to swallow it well, then a good jerk fixes the point of the hook, and the sport commences for everybody but the shark. In hauling him in it is not safe to trust only to the hook; his struggles are so violent and his strength is so great that he may break away. Being hauled therefore to the surface, the next thing is to get the noose of another rope round his body near the tail, or round one of his pectoral fins. This done he may be safely hauled on board, but even then he cannot be approached without danger, since a blow from his tail may prove fatal. In catching sharks off the coast of Nantucket, in smacks, the fishermen haul them to the surface at the side of the boat, and then kill them with blows on the head before taking them on board.CUTTLE FISH MAKING HIS CLOUD.Among the monsters of the deep, none is more terrific in appearance than the cuttle fish. Terrible stories have been told of the magnitude of these sea monsters. Under the name of the Kraken marvelous tales were told of its destruction of ships, one of them, it being said, embracing a three-masted ship in its gigantic arms. Our illustration, however, shows a well authenticated case of the capture of an enormous cuttle fish. An account of the capture was made to the French Academy of Sciences by Lieutenant Bayer, the commander of the French corvette Alecton, who made the capture, and M. Sabin Berthelot, the French Consul at the Canary Islands. While on her course between Teneriffe and Madeira, the Alecton fell in with a large cuttle fish measuring about fifty feet in length, without counting its eight arms, covered with suckers. Its head, its largest part, measured about twenty feet in circumference: its tail consisted of two fleshy lobes or fins. Its weight was estimated at 4,000 pounds. Its color was brickish red, and its flesh was soft and glutinous. The shots which were fired at it passed through it without apparently producing any injury. After it was thus wounded, however, the sea was observed to be covered with foam and blood, and a strong odor of musk was smelt. Harpoons were also cast into it, but they took no hold. Finally, however, one of the harpoons stuck fast, and the sailors succeeded in getting a running noose round the lower part of its body, near the tail. On attempting to haul it on board, the rope cut it in two, the head part disappearing and the tail portion being brought on deck.IDEAL SCENE.—MONSTERS OF THE GREAT DEEP BEFORE THE DELUGE.It is supposed that the animal was either sick, or exhausted from some cause, possibly a recent struggle with some other marine monster, and that on this account it had left its usual haunts on the rocks at the bottom of the sea, since otherwise it would have been more active than it was, or would have discharged the inky cloud, which the cuttle fish has always at its disposal for avoiding its enemies.RED CORAL.
STAR FISH.
STAR FISH.
STAR FISH.
THE OCEAN AS A FIELD—THE VARIOUS CROPS IT YIELDS—THE SPONGE—TRANSPLANTING SPONGES—CORAL FISHING—THE DISCOVERY OF THE NATURE OF CORAL—ITS RECEPTION BY NATURALISTS—OYSTER FISHERY—THE OYSTER A SOCIAL ANIMAL—THE YOUNG OYSTER—OYSTER CULTURE—DREDGING FOR OYSTERS—THE AMERICAN OYSTER FISHERY—PEARL OYSTERS—PEARL FISHERIES—THEIR VALUE—SHARK FISHING—CUTTLE FISHING.
Though the ocean may appear to be a barren waste of water to the farmer, it has by no means this aspect to the fisherman. To him it is the field in which he labors, and the crops he gathers from it are as diversified in character, and as important for satisfying the demands of the world, as those which the farmer raises. And further than this, the labors of the fisherman have helped to increase our knowledge of the composition and character of the sea, of the habits of the organized beings found in it, as the labors of the farmer have done the same thing for the soil, and the products which it bears.
In considering the various fisheries of the ocean, naturally that of the sponge, as one of the lowest forms of animal life, comes first in order. Science is hardly yet decided in its views concerning the organization and development of these obscure and complex creatures, and despite the investigations of modern naturalists, their position in the scale of animal life is still problematical, and their internal organization is still known only imperfectly. Dr. Bowerbank in his work on British Sponges, published in 1866, describes nearly 200 species, but this number by no means includes them all. They are of all sizes, and of all possible diversity of shape. At present the chief sponge fishing is carried on in the Grecian Archipelago and on the coast of Syria. The boat's crew consists of four or five men who, between June and October, seek the sponges under the cliffs and ledges of the rocks. Those obtained in shallow waters are considered inferior; the best are obtained at a depth ranging from twenty to thirty fathoms. The poorer sponges are taken from the shallow waters with harpoons, but are injured by this method of capture. The others are taken by hand. The diver descends to the bottom, and can stay there from a minute to a minute and a half, and carefully detaches the sponges from the rocks with a knife.
SPONGE FISHING.
SPONGE FISHING.
SPONGE FISHING.
Sponge fishing is also carried on in other parts of the Mediterranean, but without any foresight, so that the sponges will, in time, be exhausted. To guard against this contingency, it has been proposed to transplant and acclimatize the sponges upon the coast of France and Algeria, where the composition of the water is the same as that upon the coast of Syria, and where the difference of temperature would prove no impediment to their flourishing. In fact, the farther north the sponges grow, the finer and compacter are their tissue. By use of a submarine boat, supplied with air by a force-pump, it was proposed to collect such specimens, as were best suited for the purpose, removing the rocks with them; and also to collect the young sponges, during the months of April and May, shortly after they have commenced their independent existence, and before they have anchored themselves to some permanent abode, and transport them to a favorable locality. The French Acclimatization Society, in 1862, gave a commission to M. Lamiral, who had passed years in the study of sponges, and who has published an excellent work upon their habits, to collect the germs, and transplant them to the coast of France.Though up to this time, the attempts which have been made to do this have not met with perfect success, yet the results already gained, show that with further experience, perseverance will attain its desired end.
Sponges are also fished for in the Red Sea. On the Bahama Banks, and in the Gulf of Mexico, sponges are taken by Mexicans, Spaniards, and Americans, in shallow water. A mast is sunk at the side of the boat, and the diver descends this; gathering the sponges found near the bottom of the pole.
Next in order of fishing in deep sea, comes coral fishing. The ancients believed that the coral was a plant, but it is now known that the coral is constructed by a family of polyps living together, and constituting a polypidom. It abounds in the waters of the Mediterranean where upon rocky beds like a submarine forest, the red coral, the most brilliant and celebrated of all coral, grows at various depths, rarely less than five fathoms, or more than one hundred. Each polypidom resembles a red leafless shrub, bearing delicate little star-shaped white flowers. The branches and trunk of this little tree, are the parts common to the family, the flowers are the individual polyps. The branches show a soft, reticulated crust, or bark, full of small holes, which are the cells of the polyps and they are permeated by a milky juice. Beneath the crust is the coral, hard as marble, and remarkable for its striped surface, its red color, and the fine polish it will take. The fishing is chiefly carried on by sailors from Genoa, Leghorn, and Naples, and is a very laborious occupation. The barks engaged in it are small, ranging from ten to fifteen tons. The coral is fished with an apparatus called an engine, consisting of cross bars of wood tied and bolted together at the centre. Below this is a large stone with nets or bags attached. Each engine has a number of these nets, and when let down into the sea, they spread out. The coral grows on the tops of the rocks, and the object is to scrape it off into these bags. By experience, the fishermen come to learn the favorable places for capturing the coral. When such a spot is reached, the engine is thrown overboard, and as soon as it reaches the bottom, the speed of the vessel is slackened, and the capstan, for hauling it up is manned. In this way the engine is dragged over the bottom, becomes entangled with the rocks, and the nets catch the coral. Sometimes rocks of large size are brought on board.
CORAL FISHING OFF THE COAST OF SICILY.
CORAL FISHING OFF THE COAST OF SICILY.
CORAL FISHING OFF THE COAST OF SICILY.
Up to the last century the opinion of antiquity that coral was a vegetable product was accepted by all naturalists, though no one attempted an explanation how it grew. This opinion was confirmed when the Count de Marsigli announced his discovery of the flowers of the coral plant, and this announcement was considered the final proof of the vegetable origin of coral. In 1723, however, Jean André de Peyssonnel, a pupil of Marsigli's, and a student of medicine and natural history at Paris, was sent to Marseilles, his native place, by the Academy of Sciences, to study the coral in its living condition, and continued his studies on the northern coast of Africa, where he was sent by the French Government.
He soon discovered, by a series of careful and delicate experiments, that the coral was an animal product, and that the supposed flowers were the expanded little animals who build up the coral, and who form one of the lowest forms in the series of organized life on the globe. Peyssonnel says: "I put the flower of the coral in vases full of sea-water, and I saw that what had been taken for a flower of this pretended plant was, in truth, only an animal, like a sea nettle or polyp, I had the pleasure of seeing the feet of the creature move about, and having put the vase full of water, which contained the coral, in a gentle heat over the fire, all the small animals seemed to expand. The polyp extended his feet, and showed what M. de Marsigli and I had taken for the petals of a flower. The calyx of this pretended flower, in short, was the animal, which advanced and issued out of his cell."
This discovery was received by the naturalists of the time with contempt and ridicule; so much so that Peyssonnel, disgusted, retired into obscurity, leaving his manuscripts in the Museum of Natural History in Paris, where they still remain, unpublished. Before his death, however, in his retirement, he had the satisfaction of seeing his views accepted, and some of those who had most ridiculed them on their first presentation, become the most enthusiastic and effective advocates of them.
Besides the coral fished for as we have described, the coral polyp constructs islands, and carries on labors which very materially affect the condition of the ocean and the form of the land, concerning which we will have occasion to speak else where.
Another fishery which may be fitly mentioned here is the oyster fishery. There are several varieties of the oyster. Those usually eaten in France are the common oyster (Ostrea edulis), and the horse foot oyster (O. hippopus). The oysters of the Mediterranean are the rose-colored oyster (O. rosacea), and the milky oyster (O. lacteola), with the small and little known crested oyster (O. instata), and the folded oyster (O. plicata). On the Corsican coast the oysters are called foliate (Olamleosa). In France the Cancale and Ostend oysters are chiefly noted. When the first of these has been fed for some time in the parks or beds, and has assumed a greenish color, it is known as the Narenna oyster, from the name of the park in the Bay of Scudre.
Natural oyster beds occur in every sea where the coast affords the proper conditions with a shelving and not too rocky bottom. In France the beds of Rochelle, Rochefort, the isles of Re and Oleron, the bay of St. Brieuc, Cancale and Granville are the most famous. On the Danish coast there are forty or fifty beds on the west coast of Schleswig, the best lying between the small islands of Sylt, Amzon, Fohr, Pelworm and Nordstrand. The oyster beds of England extendfrom Gravesend, in the estuary of the Thames and midway along the Kentish coast, and in the estuary of the Coluc and other small streams on the Essex coast. The Frith of Forth is also famous for its oyster beds. The product of these beds has diminished in recent times; according to some authorities from too improvident and persistent dredging, but Mr. Buckland attributes the decrease in the yield to sudden changes in the temperature at the critical period when the spat, or young oysters, are just formed, rather than to over-dredging.
The United States is more abundantly furnished with oyster beds than any other country. They extend along almost the entire coast. Those of Virginia are estimated to comprise nearly 2,000,000 of acres. The sea-board of Georgia is famous for its immense supplies, while the whole 115 miles of Long Island is occupied with them.
The oyster is one of the lowest forms of the mollusk. Its mouth opens right into its stomach, which is surrounded by its liver, permeated by a yellow liquid, the bile. It may thus be said that they have their stomach and intestine in the liver, the mouth upon the stomach and the opening of the intestine in the back. They have a heart which circulates a colorless blood. They breathe at the bottom of sea, having an organ which separates from the water the small amount of oxygen it contains. Their respiratory organs are two pair of gills, or branchiae, curved and formed by a double series of very delicate canals placed close together, resembling the teeth of a fine comb. This apparatus, like the mouth, is hidden under the fold of the mantle. They have no brain, but a ganglion of nerves, a whitish substance situated near their mouths. From this originate the nerves, which branch off to the region of the liver and stomach; here they re-unite in a second ganglion which is placed behind the liver. The nerves of the mouth and its tentacles originate in the first ganglion, those of the respiratory organs in the second. It has no sense of sightor hearing, the sense of touch is all that it has, and this resides in the tentacles of the mouth. Its taste, if it has any, must be very feeble. Its powers are most limited; imprisoned forever in its shell, it has no power of locomotion, and being without any distinction of sex, its wants or desires must be very few.
Still the oyster appears to be a social animal, and loves to gather together in great numbers, so that despite their apparently low grade of intelligence, we cannot say that they have not sympathetic feelings. Uniting as they do both sexes in each individual, the oyster's organs of reproduction are visible only at the period they are in use. Their young are produced from eggs, which are produced between the folds of their mantle, and in the midst of their respiratory organs. The number of these eggs is prodigious. According to some authorities the number produced by a single oyster reaches 10,000,000. Naturalists, however, at present consider this estimate too high, and limit it at about 2,000,000 for each individual. The eggs are yellow, are hatched in the mantle, and when the embryo leaves its parent it can breathe. The spawning time is from June to September. The oyster differs from most shell-fish in that when the young leave the parent they can support themselves; ordinarily the shell-fish throw out their eggs committing them to chance for their protection. In the spawning season an oyster bed is the most interesting place; each oyster is throwing out a whole array of descendants, filling the water with a cloud of living dust, so that the sea is clouded with thespatas it is called.
Under the microscope the spat is seen to be provided with a shell, and with vibratory cils which enable it to swim. When the current carries it against any stationary body, it immediately adheres to it, the cils disappear and the young oyster, becoming fixed, commences to develop. It takes three years for them to attain their full size. While the spat isswimming about, before becoming fixed, it is said that if anything alarm them they seek refuge again within the maternal shell. Such prolific production would soon stock the whole sea, were it not for the fact that the young are feeble swimmers, and that millions of them are annually swept away and lost by the current, or fall a prey to the numerous animals which feed upon them.
FAGGOTS SUSPENDED TO RECEIVE OYSTER SPAT.
FAGGOTS SUSPENDED TO RECEIVE OYSTER SPAT.
FAGGOTS SUSPENDED TO RECEIVE OYSTER SPAT.
The favorite place for the oyster is on the shore, in water not very deep and free from currents; here they are very prolific. The idea of breeding them is as old as the Romans, and to-day the planting of oyster beds, and fishing from them gives occupation to thousands. Some of the oyster beds of France which were nearly exhausted twenty years ago have been made again very productive by attention and care. The plan of suspending faggots upon which the spawn should adhere, has been found very successful. From the Bay of St. Brieuco two faggots, taken up at random, were found to contain about 20,000 young oysters, ranging in size from one to three inches in diameter. Their exhibition excited astonishment; they looked like leafy branches, each leaf being a living oyster.
In the island of Re oyster farming is in full operation. It is calculated that the beds contain 600 oysters to the square yard, the majority of marketable condition, making a total of 378,000,000 in these beds alone. In the United States, theproductiveness of the beds is almost inestimable, and yet, despite the immense number of oysters yearly brought to market, the demand continually outstrips the supply. The modern methods of canning have opened a so much wider market, the whole inland country being thus opened to the supply, it is almost impossible to overstock the market.
The peculiar green color of the oysters in France, which have been planted in beds, or claries, and which is thought to make their flavor better, arises from some cause, concerning which naturalists differ. It seems, however, to be some kind of disease, arising from the condition of the water in these beds.
Oyster fishing is pursued in different ways, in different countries. Around Minorca the diver descends with a hammer in his hand to knock the oysters from the rocks, and brings up generally a dozen or more with each descent. On the English and French coasts the dredge is used. This method is very destructive, since it tears the large and small together from their native spot, and buries many also in the mud. Oysters, as we know them, are of convenient size for making a mouthful; the largest may have to be separated into parts before a delicate person can swallow them, but it is only the largest which have to be submitted to this process, and your real oyster lover has too tender a regard for his favorite mollusk to so maltreat it. On the coast of Coromandel, however, the oysters grow to be as big as soup plates, and larger, the shells of some of them measuring almost two feet across. These shells are frequently used in the Catholic churches of Europe to contain the holy water, placed near the door for the use of the faithful, and are quite as large as big hand basins. A half-dozen such oysters on the half-shell, would make a feast even for the most voracious oyster eater.
The oyster beds on the coast of the United States are generally in so shallow water that they can be readily reached withrakes furnished with handles fifteen to twenty feet long. A pair of these are mounted like a gigantic pair of scissors, the pivot being nearer the rakes than the other end of the poles. Taking an end of one of these poles in each hand, the fisherman sinks it to the bottom, opens it, and moves the handles until a supply of oysters is scraped up between the rakes. Then pulling up the instrument, he empties the oysters into the bottom of his boat, and uses his rakes again. Millions of dollar's worth of oysters is thus fished every year, and fleets of small sailing ships are constantly engaged in the traffic along the coast.
To an European, the American oyster at first appears enormous, compared with those he is accustomed to. Their flavor also is different; they have not a peculiar coppery taste to which he is accustomed, and which most Americans in Europe dislike at first. A little practice, however, soon enables the European to recognize the merit of our oysters, and they become very fond of them. Both Thackaray and Dickens, during their visits to this country, were loud in their praises of the excellence of the oysters.
DREDGING FOR OYSTERS.
DREDGING FOR OYSTERS.
DREDGING FOR OYSTERS.
The pearl oyster (Meleagrina margaritifera), is one of the most interesting and valuable of the varieties of the oyster. The pearls are formed of the same substance which lines the shells of so many shell-fish, and which as nacre, or mother of pearl, is so well known for its iridescent beauty. It is deposited by the animal in very thin layers, and it is the interference of the rays of light in their reflection from this varying surface which produces the phenomena of iridescence. It is easy for any one to satisfy himself of this. Press a piece of wax upon a piece of mother of pearl, or any other iridescent body, and the surface of the wax when removed will itself appear iridescent. It has reproduced the fine lines of the iridescent body. Soap bubbles, being formed of films of the soapy water, attain their brilliant coloring from the same cause. Brass buttons were once fashionable which showed the same colors. They were made by having the polished surface ruled with microscopically fine lines. It was, however, so costly to make them, they cost a guinea each, that they were soon abandoned.
A SHELL CONTAINING CHINESE PEARLS.
A SHELL CONTAINING CHINESE PEARLS.
A SHELL CONTAINING CHINESE PEARLS.
Pearls are the secretion of nacreous material, spread, it is supposed, over some foreign substance which has been introduced into the shell, under the mantle of the mollusk. When the pearls are deposited on the shells, they generally adhere to it, when they originate in the body of the animal they are free. As a rule some foreign body is found in their centre which served as the nucleus for the deposit of the secretion. It may be a sterile egg of the animal itself, or of a fish, or a grain of sand, which was washed in.
The Chinese and other nations of the East, take advantage of this fact in natural history, for purposes of profit. They take up the living mollusk, and opening the shell introduce into it glass beads, or small metallic casts, representing some one of their gods, or other objects, and then returning the mollusk tothe water, in time the animal has coated them with mother of pearl. The illustration shows a shell into which small beads have been introduced, and converted into pearls, together with a dozen small figures of Buddha, the Hindoo divinity, seated, which have been covered over with nacre also.
The pearls are at first very small, but they increase in size with the yearly deposit of a layer on the original centre. Sometimes they are diaphanous, semi-transparent, lustrous and more or less irridescent, at other times, however, they prove to be dull, obscure, and smoky even. The pearl fisheries are carried on in various places. They are found in the Persian Gulf, on the coast of Arabia, in Japan, on the shores of California, and in the islands of the South Sea. The most important ones are, however, those of the Bay of Bengal, the coast of Ceylon, and elsewhere in the Indian Ocean. Previous to 1795 most of the Indian fisheries were in the hands of the Dutch, but in 1802, after the treaty of Amiens, they passed into the possession of the English. Sometimes the Ceylon fisheries are undertaken by the Government, while at others they are sold to a contractor. In either case, before they begin, the coast is inspected by a Government official, in order to see that the banks are not exhausted by too frequent fishing.
The chief supply of mother of pearl is obtained from the fishery in the Gulf of Manaar, a large bay on the northeast of the island of Ceylon. It commences in February or March, and lasts thirty days. Some two hundred and fifty boats are engaged in it, coming for the purpose from all parts of the coast. At ten at night a gun gives the signal for them to set sail, and reaching the ground they commence as soon as the dawn affords sufficient light. Each boat carries ten rowers and ten divers, five of whom rest while the others are engaged. A negro to attend to the odd jobs and chores accompanies each boat.
PEARL FISHER IN DANGER.
PEARL FISHER IN DANGER.
PEARL FISHER IN DANGER.
The divers descend from forty to fifty feet, seventy is the utmost they can stand. Thirty seconds is the time they usually remain under water, and the best cannot stay longer than a minute and a half. When the fishing ground is reached a staging, built of the oars, is rigged to project from the boat over the water, and to the edge of this the diving-stones are hung, weighing from fifty to sixty pounds. The diver stands in a stirrup upon this, or if this is wanting upon the stone itself, holding the cord attached to it between his toes, with his left foot he holds the net for the reception of the pearl-oysters. Then, pressing his nostrils firmly with his left hand, and with his right grasping the signal cord, he is let rapidly down to the bottom. As soon as he arrives there, he removes his foot from the stone which is immediately drawn up again. Then throwing himself flat upon the ground, he hastily gathers into his net all the oysters within his reach. When he feels he must return to the surface he pulls the signal cord with a jerk, and is pulled up as quickly as possible. A good diver seeks to avoid straining himself, and so stays under water only the shortest time, seldom more than half aminute, but he will repeat the operation sometimes as much as fifteen or twenty times. The work is very distressing, the increased pressure of the water affects the entire system, and frequently on rising to the surface the water which runs from their ears, nose and mouth is tinged with blood. The effect is also to induce pulmonary diseases, and the divers rarely attain old age. Sharks are also common in these waters, and the divers are not unfrequently destroyed by these rapacious monsters, who are the more attracted by the fact that the divers, for their own convenience, are naked.
The work continues until noon, when a second gun gives notice for its cessation. The boats then return with the cargo they have gained, and are received by the proprietors on the shore, who personally superintend their discharge, which must be finished before dark, since anything left over night would most certainly be stolen.
The fisheries of Ceylon were formerly very valuable, but at present the banks show signs of exhaustion, from over-fishing most probably. In 1798 they are said to have produced nearly a million dollars' worth of pearls, but now they seldom yield more than a hundred thousand dollars' worth. The inhabitants along the coast of the Bay of Bengal, the Chinese seas, and the islands of Japan, are also engaged in the pearl fishing. Together the yield is estimated at about four millions of dollars.
Further west, on the Persian coast, the Arabian gulf and the Muscat shore, as well as in the Red sea, pearls are found.
In these latter countries the pearl fishing commences in July, for during this and the next month the sea is usually calm. When the boats have arrived over the bed, they anchor, the water being eight or nine fathoms deep. The divers carry their bag tied around their waists, and plug their nostrils with cotton, then closing their mouths, are sunk by a stone rapidly to the bottom. The pearls obtained from thefisheries on the Arabian coast reach a value of over a million and a half of dollars.
Pearl fishing is also carried on, on the coast of South America. Before the Spanish conquest of Mexico the fisheries were situated between Acapulco and the Gulf of Tehuantepec, but since that time other beds have been found near the islands of Cubagua, Margarita and Panama. The yield at first was so promising that flourishing cities grew up in the vicinity of these places, and during the reign of Charles V., pearls to the value of nearly a million of dollars were sent to Spain, but the present yield averages only about three hundred thousand dollars.
When the oysters are taken from the boats, they are piled up on grass mats on the shore, and left in the sun. The mollusks soon die, and begin to decompose. In about ten days they are sufficiently putrified to become soft. Then they are thrown into tanks of sea water, opened and washed. The pearls which adhere to the shells are taken off with pinchers; those that are in the body of the animal are secured by passing its substance through a sieve, after boiling the flesh to make it soft. The shells furnish the nacre, which is split off from the rough outside with a sharp instrument, or the outside is dissolved from the mother of pearl by an acid. Three kinds of mother of pearl are known in commerce, as silver face, bastard white and bastard black; the first is the most valuable. The pearls are the most important part of the product. Those which adhere to the shell are always more or less irregular in their shape, and are sold by weight. They are calledbaroques. Those found in the body of the animal are calledvirgin pearls, orparagons, and are round, oval or pyramid shaped. These are sold generally singly; the price varying according to size, lustre, clearness, etc. Months after the shells have been examined, poor natives are seen diligently turning over the putrifying mass which has been cast aside, eagerly searching forsome pearl that has been overlooked; as in our cities the ashes, barrels and gutters are searched by the same wretched class for the refuse of luxury.
The pearls are polished by shaking them together in a bag with nacre powder. By this process they are smoothed and polished. Then they are assorted according to sizes by being passed through a series of copper sieves, placed over each other, and pierced with an increasing number of holes, growing smaller. Thus, sieve number twenty has twenty holes in it; fifty, fifty holes, and the last of the series of twelve, one thousand holes. The pearls retained between twenty and eighty are called mill, and are considered to be of the first order. Those between one hundred and eight hundred are vivadoe, and class second. Those which pass through all but the thousand are tool, or seed pearls, and are third. The seed pearls are sold by measure or weight. The larger ones are drilled, strung on a white or blue silk thread, and exposed for sale.
In the American fisheries the oysters are opened each separately with a knife, and the animal is pressed between the thumb and finger in the search for pearls. This process takes longer, and is not considered as certain to find them all as that followed in the East, but the nacre and the pearls thus taken from the live animal are fresher and more brilliant than from those oysters which have died and decayed. Other mollusks also furnish pearls, but not in a regular enough supply to justify their fishing. In fact pearls are often found in our common oysters.
SHARK FISHING.
SHARK FISHING.
SHARK FISHING.
Fishing for sharks is one of the most exciting kinds of sport, and has the further merit that its success is the destruction of the most destructive inhabitant of the sea; a predatory robber, who spares none that come in his way. The prey in which the shark most delights is, however, man himself. He even manifests, according to some authorities, a preference for Europeans over the Asiatic or the Negro races. A shark who has once enjoyed the luxury of human flesh is said to haunt the neighborhood where he obtained it. He follows a ship from some instinctive feeling, and has been known to leap into a fisherman's boat, or throw himself against a ship in an effort to reach a sailor who had shown himself over the bulwarks. The slave ships during their voyages were constantly followed by sharks, who battled eagerly for the corpses of the unhappy dead which were thrown overboard. In one case it is recorded that a corpse was hung from the yard arm, dangling twenty feet above the water, and was devoured, limb by limb, by a shark, who leaped that distance from the water to obtain his horrid repast.
On the African coast the negroes boldly attack the shark in his own element. As his mouth is placed under his head, he has to turn round before he can seize anything, and taking advantage of this, the negro seizes the opportunity to rip him up with a sharp knife.
Shark fishing is regularly followed off the coast of Nantucket, for their skins and the oil they furnish. The skins are used for various purposes in the arts. In Norway and Iceland portions of the flesh are dried, and serve as provision for the food of winter.
The persistancy with which a shark will follow a vessel at sea leads to their frequently being caught. The hook is of iron, as thick as a man's finger, and six or eight inches long, the point made very sharp. It is fastened with a chain five or six feet long, to prevent the shark's teeth from severing it. Baited with a good sized piece of pork, and fastened to a long line, it is thrown over. Sometimes in his eagerness to catch it the shark will jump from the water, but oftener, having probably learned from experience something about the tricks of men, he is more cautious in taking it. Often he will examine it, swim round it, and manage to get it, without taking the hook also, as often as it is offered to him rebaited. If he, however, swallows the hook with the bait, it still requires some dexterity to catch him; the line must not be jerked prematurely; he must be given time enough to swallow it well, then a good jerk fixes the point of the hook, and the sport commences for everybody but the shark. In hauling him in it is not safe to trust only to the hook; his struggles are so violent and his strength is so great that he may break away. Being hauled therefore to the surface, the next thing is to get the noose of another rope round his body near the tail, or round one of his pectoral fins. This done he may be safely hauled on board, but even then he cannot be approached without danger, since a blow from his tail may prove fatal. In catching sharks off the coast of Nantucket, in smacks, the fishermen haul them to the surface at the side of the boat, and then kill them with blows on the head before taking them on board.
CUTTLE FISH MAKING HIS CLOUD.
CUTTLE FISH MAKING HIS CLOUD.
CUTTLE FISH MAKING HIS CLOUD.
Among the monsters of the deep, none is more terrific in appearance than the cuttle fish. Terrible stories have been told of the magnitude of these sea monsters. Under the name of the Kraken marvelous tales were told of its destruction of ships, one of them, it being said, embracing a three-masted ship in its gigantic arms. Our illustration, however, shows a well authenticated case of the capture of an enormous cuttle fish. An account of the capture was made to the French Academy of Sciences by Lieutenant Bayer, the commander of the French corvette Alecton, who made the capture, and M. Sabin Berthelot, the French Consul at the Canary Islands. While on her course between Teneriffe and Madeira, the Alecton fell in with a large cuttle fish measuring about fifty feet in length, without counting its eight arms, covered with suckers. Its head, its largest part, measured about twenty feet in circumference: its tail consisted of two fleshy lobes or fins. Its weight was estimated at 4,000 pounds. Its color was brickish red, and its flesh was soft and glutinous. The shots which were fired at it passed through it without apparently producing any injury. After it was thus wounded, however, the sea was observed to be covered with foam and blood, and a strong odor of musk was smelt. Harpoons were also cast into it, but they took no hold. Finally, however, one of the harpoons stuck fast, and the sailors succeeded in getting a running noose round the lower part of its body, near the tail. On attempting to haul it on board, the rope cut it in two, the head part disappearing and the tail portion being brought on deck.
IDEAL SCENE.—MONSTERS OF THE GREAT DEEP BEFORE THE DELUGE.
IDEAL SCENE.—MONSTERS OF THE GREAT DEEP BEFORE THE DELUGE.
IDEAL SCENE.—MONSTERS OF THE GREAT DEEP BEFORE THE DELUGE.
It is supposed that the animal was either sick, or exhausted from some cause, possibly a recent struggle with some other marine monster, and that on this account it had left its usual haunts on the rocks at the bottom of the sea, since otherwise it would have been more active than it was, or would have discharged the inky cloud, which the cuttle fish has always at its disposal for avoiding its enemies.
RED CORAL.
RED CORAL.
RED CORAL.
DREDGING.CHAPTER LVI.DREDGING IN MODERN TIMES—WHAT IT HAS TAUGHT US—DEEP SEA SOUNDINGS—FIRST ATTEMPTS—IMPLEMENTS USED FOR IT—THE CHANCE FOR INVENTORS.In modern times we have learned a great deal more of the ocean than the ancients knew, from dredging. By this means we have become acquainted not only with the outline of the bottom, but have also become acquainted with the temperature of deep seas, with the varied forms of animal and vegetable life which are present there, and have come to know, with far greater certainty and completeness than ever before, the part which the ocean has played and is still playing in the preparation of the land.By sounding, the ancients, of course, knew the depths of the shallow waters along their coasts. It would be the most natural thing for a sailor to tie a stone to a string, and let it down into the water, when he wanted to know whether it was deep enough to float his vessel, and the same means would also be used to discover whether there were any sunken rocksin such harbors as he was frequenting. But the ocean, to all antiquity, was unfathomable; they dared not attempt to cross it, and of course did not think they could measure its depth. Long after the ocean had been crossed by ships the belief was still current that it was impossible to measure its depth, and this belief was made the stronger by the unsuccessful attempts made in mid ocean to obtain soundings with the ordinary lead and line.Before we arrived at a positive knowledge of the depth of the ocean, scientific men attempted to calculate it by various methods. Laplace, calculating the mean elevation of the land, supposed the sea must be of about equal depth. Young, drawing his deductions from the tides, calculated the depth of the sea. This method has been recently used to calculate the depth of the Pacific. A wave of a certain velocity indicates water of such a depth. In the case of the earthquake of 1854, in Japan, which caused a wave that extended to California, the rate of its progress afforded an indication of the mean depth of the sea it passed over, and authentic soundings taken since have confirmed the general accuracy of the calculation.The ordinary lead used for soundings is a pyramid of lead, the bottom of which has a depression in it, which is filled with tallow; on striking the bottom a little of the sand or mud adheres to this tallow and is brought up to the surface. In this way something is learned about the depth and bottom of the sea, but not enough to satisfy the naturalists, who inquired whether it might not be possible to dredge the bottom of the sea in the ordinary way, and to send down water bottles and registering instruments to settle finally the conditions of the deep waters, and determine with precision the composition and temperature at great depths.An investigation of this kind is beyond the powers of private enterprise. It requires more power and sea skill than naturalists usually have. It is a work for governments. Thatof the United States has contributed fully its share. The coast survey has added a great deal to our knowledge of the deep sea, and the ships of the navy took part in the soundings by which the existence of the plateau across the bed of the North Atlantic, which has been used for the ocean telegraphic cable, was proved.In 1868 the English government provided the vessels and crews for the purpose of conducting deep sea dredgings, under the direction of Dr. Carpenter and Mr. Wyville Thompson. These expeditions have found that it is quite possible to work with certainty, though not with such ease, at the depth of 600 fathoms, as at a depth of 100; and in 1869 it carried on deep sea dredging at a depth of 2,435 fathoms, 14,610 feet, or very nearly three miles, with perfect success. Dredging in such deep water is very trying. Each haul occupied seven or eight hours, and during the whole of this time the constant attention of the commander was necessary, who stood with his hand on the regulator of the accumulator, ready at any moment to ease an undue strain, by a turn of the ship's paddles. The men, stimulated and encouraged by the cordial interest taken by the officers in the operations, worked with a willing spirit; but the labor of taking up three miles of rope, coming up with a heavy strain, was very severe. The rope itself, of the very best Italian hemp, 2 1/2 inches in circumference, with a breaking strain of 2 1/4 tons, looked frayed out and worn, as if it could not have been trusted to stand such an extraordinary ordeal much longer.The ordinary deep sea lead used for soundings weighs from 80 to 120 pounds. The samples of the bottom which it brings up are marked upon the charts as mud, shells, gravel, ooze or sand, thus 2,000 m. sh. s. means mud, shells and sand at 2,000 fathoms; 2,050 oz. st. means ooze and stones at 2,050 fathoms; 2,200 m. s. sh. sc. means mud, sand, shells, and scoriæ, at 2,200 fathoms, and so on. When no bottom is found with the leadit is entered on the chart thus:——3,200, meaning no bottom was reached at that depth.This method of sounding answers very well for comparatively shallow water, but it is useless for depths much over 1,000 fathoms, or six thousand feet. The weight is not sufficient to carry the line rapidly and vertically to the bottom; and if a heavier weight is used, the ordinary sounding line is not strong enough to draw up its own weight, and that of the lead from a great depth, and so breaks. No impulse is felt when the lead touches the bottom, and so the line continues running out, and any attempt to stop it breaks it. In some cases the slack of the line is carried along by currents, and in others it is found that the line has been running out by its own weight and coiling in a tangled mass on top of the lead.These sources of error vitiate the results of very deep soundings. Thus Lieutenant Walsh, of the U.S. schooner Taney, reported 34,000 feet without touching bottom; and the U.S. brig Dolphin used a line 39,000 feet long without reaching bottom. An English ship reported 46,000 feet in the South Atlantic and the U.S. ship Congress 50,000 feet without touching bottom. These are, however, known to be errors, so that no soundings are entered on charts over 4,000 feet, and few over 3,000. The U.S. Navy introduced the first great improvement in deep soundings. This consisted in using a heavy weight and a small line. The weight, a 32 or 68-pound shot, was rapidly run down, and when it touched bottom, which was shown by the sudden change in the rapidity with which the line was run out, the line was cut and the depth estimated from the length of cord remaining on the reel. This, however, cost the loss of the shot and the line for each sounding.One of the first attempts at deep sea dredging was made in 1818, by Sir John Ross, in command of the English navy vessel Isabella, on a voyage for the exploration of Baffin's Bay with a machine of his own invention, which he called a "deepsea clamm." It consisted of a pair of forceps, kept apart by a bolt, and so contrived that when the bolt struck the ground a heavy iron weight slipped down a spindle and closed the forceps, which retained a portion of the mud, sand, or small stones, from the bottom. With this instrument he sounded in 1,050 fathoms, and brought up six pounds of very soft mud, using a whale line, made of the best hemp, and measuring 2 1/2 inches in circumference.The cup lead is another invention. With this there is a pointed cup at the bottom of the lead, fastened to it with a rod upon which a circular plate of leather plays, serving as a cover to the cup. As it strikes the bottom, the cup is driven in the mud, and on hauling up the cover is pressed into the cup by the water, and brings up the mud it contains. The objection to this is that it is too crude; in its passage up, the water washes away the mud, so that only on an average of once in three times does the cup come up with anything in it; and deep sea soundings take too much time, and are too valuable, to admit so large an average of loss.About 1854 Mr. J. M. Brooke, of the U.S. Navy, who was at the time associated with Prof. Maury, so well known for his labor in gathering and diffusing a knowledge of the currents of the ocean, invented a deep sea sounding apparatus, which is known by his name. It is still in use, and all the more recent contrivances have been, to a great extent, only modifications and improvements upon the original idea, that of detatching the weight. The instrument is very simple. A 64-pound shot is cast with a hole in it. An iron rod, with a cavity in its end, fits loosely in the hole in the shot. Two movable arms at the top of the rod are furnished with eyes holding ends of a sling in which the ball hangs. The cavity at the end of the rod is furnished with tallow, and the apparatus is let down. On reaching the bottom, the rod is forced into the mud, the cavity becomes filled with it, and there being no more tension, on the rope holding up the movable arms, they fall, disengage the ends of the sling, and allow the ball to slide down the rod. The rod is then withdrawn, carrying up the portion of the bottom secured in the cavity at its foot, and leaving the ball on the bottom. This apparatus costs a ball each time it is used, and brings up but a small portion of the bottom, which is also apt to be diminished on its way to the top, by the water it passes through.STRIKING THE SEA BOTTOM. BROOK'S DEEP SEA SOUNDING APPARATUS.Commander Dayman, of the English Navy, in 1857 invented an improvement upon Mr. Brooke's original invention. He used iron wire braces to support the sinker, as these detach more easily than slings of rope. The shot he replaced by a cylinder of lead, as offering less surface to the water in its descent, and he fitted the cavity in the bottom of the rod with a valve opening inward. Commander Dayman used the apparatus, with these modifications, in the important series of soundings he made in the North Atlantic, while engaged in surveying the plateau for the ocean telegraphic cable, and reports that it worked well.THE BULLDOG SOUNDING MACHINE.The apparatus known as the bull-dog machine is an adaptation of Sir John Ross' deep-sea clamms, together with Brooke's idea of disengaging the weight. It was invented during the cruise of the English Navy vessel, the Bull-dog, in 1860, and the chief credit for it belongs to the assistant engineer during that cruise, Mr. Steil. A pair of scoops are hinged together like a pair of scissors, the handles represented by B. These are permanently fastened to the sounding rope, F, which is here represented as hanging loose, by the spindle of the scoops. Attached to this spindle is the rope, D, ending in a ring. E represents a pair of tumbler hooks, like those used so generally. C is a heavy weight, of iron or lead, hollow, with a hole large enough for the ring upon D to pass through. B is an elastic ring of India rubber, fitted to the handles of the scoops, and designed to shut them together as soon as theweight, C, which now holds them apart, is removed. When the bottom is reached, the scoops, open, are driven into the ground, the tension on the rope ceases, the tumbler hooks open and release the weight, which falls on its side, and allows the elastic ring to shut the scoops, inclosing a portion of the bottom in which they have been forced. The trouble with this apparatus is its complicated character; pebbles may get in the hinge and prevent the scoops from closing. In all apparatus to be used for such a purpose the greater the simplicity the better, and an invention, which shall at once be simple and effective, capable of bringing up a pound or two from the bottom at a depth of 2,000 fathoms or more, without fail, and without too much trouble, is still a desideratum, and its invention is well worth the attention of the ingenious.Another arrangement, called the Hydra sounding machine, is intended to bring up portions of the bottom and water from the lowest strata reached. It consists of a strong brass tube, which unscrews into four chambers, closed with valves, opening upward, so that in the descent the water passes through them, freely; but when it is commenced to haul up, the pressure of the water closes the valves. This apparatus is also furnished with weights to sink it, which are released, on reaching the bottom, by a similar method to those described. This instrument was used during the deep sea sounding cruise of the Porcupine, and never once failed. Its faults are its complication, and that it brings up only small samples of the bottom. Captain Calver, who used it, could always, when at the greatest depths, distinctly feel the shock of the arrest of the weight upon the bottom communicated to his hand.MASSEY'S SOUNDING MACHINE.Various attempts have been made to construct instruments which should accurately determine the amount of the vertical descent of the lead by self-registering machinery. The most successful and the one most commonly used is Massey's sounding machine. This instrument, in its most improved form, is shown in the accompanying cut. It consists of a heavy oval brass shield, furnished with a ring at each end of its longer axis. To one of these a sounding rope is attached, and to the other, the weight is fastened at about a half fathom below the shield. A set of four brass wings or vanes are set obliquely to an axis, so that, like a windmill or propeller wheels, it shall turn by the force of the water as it descends. This axis communicates its motion to the indicator, which marks the number of revolutions on the dial plate. One of these dials marks every fathom, and the other every fifteen fathoms of descent. This sounding machine answers very well in moderately deep water, and is very valuable for correcting soundings by the lead alone, where deep currents are suspected, as it is designed to register vertical descent alone. In very deep water it is not satisfactory, from some reason which it is difficult to determine. The most probable explanation is that it shares the uncertainty inherent in all instruments using metal wheel work. Their machinery seems to get jammed in some way, under the enormous pressure of the water, at great depths.To ascertain the surface temperature of the water of the sea is simple enough. A bucket of water is drawn up, and a thermometer is placed in it. With an observation of this kind the height of the thermometer in the air should be always noted. Until very recently, however, very little or nothing was known with any certainty about the temperature of the sea at depths below the surface. Yet this is a field of inquiry of very greatimportance in physical geography, since an accurate determination of the temperature at different depths is certainly the best, and frequently the only means, for determining the depth, the width, the direction and general path of the warm ocean currents, which are the chief agents in diffusing the equatorial heat; and more especially of those deeper currents of cold water which return from the poles to supply their places, and complete the watery circulation of the globe. The main cause of this want of accurate knowledge of deep sea temperatures is undoubtedly the defective character of the instruments which have been hitherto employed.The thermometer which has been generally used for making observations on the temperature of deep water is that known as Six's self-regulating thermometer, inclosed in a strong copper case, with valves or apertures above and below, to allow a free passage of the water through the case and over the face of the instrument. This registering thermometer, consists of a glass tube, bent in the form of a U. One arm terminates in a large bulb, entirely filled with a mixture of creosote and water. The bend in the tube contains a column of mercury, and the other arm ends in a small bulb, partly filled with creosote and water, but with a large space empty, or rather filled with the vapor of the mixture and compressed air. A small steel index with a hair tied round it, so as to act like a spring against the side of the tube, and keep the index at any point it may assume, lies free in either arm, among the creosote, floating on the mercury. This thermometer gives its indications only from the expansions and contractions of the liquid in the large full bulb, and consequently is liable to some slight error, from the variations of temperature upon the liquids in other parts of the tube. When the liquid in the large bulb expands, the column of mercury is driven upward toward the half-empty bulb, and the limb of the tube in which it rises is graduated from below, upward, for increasing heat. When the liquidcontracts in the bulb, the mercury rises in this arm of the tube, which is graduated from above downward, but falls in the other arm. When the thermometer is going to be used, the steel indices are drawn down in each limb of the tube, by a strong magnet, till they rest, in each arm, upon the surface of the mercury. When the thermometer is drawn up from deep water, the height at which the lower end of the index stands in each tube indicates the limit to which the index has been driven by the mercury, the extreme of heat or cold to which the instrument has been exposed. Unfortunately, the accuracy of the ordinary Six's thermometer cannot be depended upon beyond a very limited depth, for the glass bulb which contains the expanding fluid yields to the pressure of the water, and compressing the contained fluid, gives an indication higher than is due to temperature alone. This cause of error is not constant, since the amount to which the bulb is compressed depends upon the thickness and quality of the glass. Yet, as in thoroughly well-made thermometers, the error from pressure is pretty constant, it has been proposed to make a scale, from an extended series of observations, which might be used to correct the observations, and thus closely approximate the truth.A better plan has been proposed, and being practically applied, has been found to work very well. This consists in incasing the full bulb in an outer covering of glass, so that there shall be a coating of air between the bulb and the outside coating, and that this air being compressed by the pressure of the water outside, shall thus protect the inside bulb. Observations taken in 1869 with thermometers constructed in this way, as deep as 2,435 fathoms, in no instance gave the least reason to doubt their accuracy. A modification of the metallic thermometer, invented by Mr. Joseph Saxton, of the United States office of weights and measures, for the use of the coast survey, may be thus described. A ribbon of platinum and oneof silver are soldered with silver solder to an intermediate plate of gold, and this compound ribbon is coiled round a central axis of brass, with the silver inside. Silver is the most expansible of the metals under the influence of heat, and platinum nearly the least. Gold holds an intermediate place, and its intervention between the platinum and silver moderates the strain and prevents the coil from cracking. The lower end of the coil is fixed to the brazen axis, while the upper end is fastened to the base of a short cylinder. Any variation of temperature causes the coil to wind or unwind and its motion rotates the axial stem. This motion is increased by multiplying wheels, and is registered upon the dial of the instrument by an index, which pushes before it a registering hand, moving with sufficient friction to retain its place, when pushed forward. The instrument is graduated by experiment. The brass and silver parts are thickly gilt by the electrotype process, so as to prevent their being acted upon by the salt water.The box in which the instrument is protected is open to admit the free passage of the water. This instrument seems to answer very well for moderate depths. Up to six hundred fathoms its error does not exceed a half degree, centigrade; at 1,500 fathoms it rises however to five degrees, quite as much as an unprotected Six thermometer, and the error is not so constant. Instruments which depend for their accuracy upon the working of metal machinery cannot be depended upon when subjected to the great pressure of deep soundings.For taking bottom temperatures at great depths, two or more of the thermometers are lashed to the sounding line at a little distance from each other, a few feet above the sounding instrument. The lead is rapidly run down, and after the bottom is reached an interval of five or ten minutes is allowed before hauling in. In taking serial temperature soundings, which are to determine the temperature at certain intervals of depth the thermometers are lashed to an ordinary deep sealead, the required quantity of line for each observation of the series ran out, and the thermometers and lead are hove each time. The operation is very tedious; a series of such observations in the Bay of Biscay, where the depth was 850 fathoms and the temperature taken for every fifty fathoms, occupied a whole day. In taking bottom temperatures with a self-registering thermometer, the instrument of course simply indicates the lowest temperature to which it has been subjected, so that if the bottom stratum is warmer than any other through which the thermometer has passed, the result would be erroneous. This is only to be tested by serial observations; but from these it appears, wherever they have been made, that the temperature sinks gradually, sometimes very steadily, sometimes irregularly from the surface to the bottom, the bottom water being always the coldest.Several important facts of very general application in physical geography have been settled by the deep sea temperature soundings which have been recently made, and the theories formerly held on this subject shown to be erroneous. It has been shown that in nature, as in the experiments of M. Despretz, sea water does not share in the peculiarities of fresh water, which, as has been long known, attains its maximum density at four degrees, centigrade; but like most other liquids increases in density to its freezing point; and it has also been shown that, owing to the movement of great bodies of water at different temperatures in different directions, we may have in close proximity two ocean areas with totally different bottom climates, a fact which, taken along with the discovery of abundant animal life at all depths, has most important bearings upon the distribution of marine life, and upon the interpretation of palaeontological data.Mr. Wyville Thompson, who conducted the series of important deep sea soundings undertaken in the Porcupine, says very truly, "It had a strange interest to see these little instruments,upon whose construction so much skilled labor and consideration had been lavished, consigned to their long and hazardous journey, and their return eagerly watched for by a knot of thoughtful men, standing, note-book in hand, ready to register this first message, which should throw so much light upon the physical conditions of a hitherto unknown world."Up to the middle of the last century the little that was known of the inhabitants of the bottom of the sea beyond low water mark, appears to have been gathered almost entirely from the few objects thrown up on the beaches after storms or from chance specimens brought up on sounding lines, or by fishermen engaged in sea fishing or dredging for oysters. From this last source, however, it was almost impossible to obtain specimens, since the fishermen were superstitious concerning bringing home anything but the regular objects of their industry, and from a fear that the singular things which sometimes they drew up might be devils in disguise, with possibly the power to injure the success of their business, threw them again, as soon as caught, back into the sea. Such superstitions are dying out, and in fact so singular are many of the animals hid in the depths of the sea; their forms and general air are so different from anything which the fishermen were used to see, that we can hardly wonder at the fear they excited. When, however, the attention of naturalists was turned toward the sea, they used the dredge such as was used by the oyster fishermen, and all the dredges now in use are simply modifications of this.The dredge for deep sea operations is made with two scrapers, so that it shall always present a scraping surface to the bottom, however it may fall. The iron work should be of the very best, and weighing about twenty pounds. The bag is about two feet deep, and is a hand-made net of very strong twine, the meshes half an inch to the side. As so open a net-work wouldlet many small things through, the bottom of the bag, to the height of about nine inches, is lined with a light open kind of canvas, called by the sailors "bread-bag." Raw hides have been used for making the dredge bag, but, though very strong, they are apt to become too much so to another sense than touch. It is bad economy to use too light a rope in such operations, and best to fasten it to only one arm of the dredge, the eyes of the two arms being tied together with a thinner cord. In case, then, the dredge becomes entangled at the bottom, this cord will break first, and thus releasing one of the arms of the dredge, may so change the direction of the strain upon the rope as to free the dredge itself.Dredging in deep water, that is, at depths beyond 200 fathoms, is a matter of some difficulty, and can hardly be done with the ordinary machinery at the disposal of amateurs. The description of the apparatus used in the Porcupine, in 1869 and '70, on her dredging cruise in the Bay of Biscay, will show what is necessary. These arrangements are also shown in the cut. This vessel, a gun-boat of the English navy, of 382 tons, was fitted out specially for this work. Amidships she was furnished with a double cylinder donkey-engine, of about twelve horse-power, with drums of various sizes, large and small. The large drum was generally used, except when the cord was too heavy, and brought up the rope at a uniform rate of more than a foot a second. A powerful derrick projected over the port bow, and another, not so strong, over the stern. Either of these was used for dredging, but the one at the stern was generally used for soundings. The arrangement for stowing away the dredge rope was such as made its manipulation singularly easy, notwithstanding its great weight, about 5,500 pounds. A row of some twenty large pins of iron, about two feet and a half long, projected over one side of the quarterdeck, rising obliquely from the top of the bulwark. Each of these held a coil of from two to three hundred fathoms, and the rope was coiled continuously along the whole row. When the dredge was going down, the rope was taken rapidly by the men from these pins in succession, beginning from the one nearest the dredging derrick, and in hauling up a relay of men carried the rope from the drum of the donkey-engine and laid it in coils on the pins, in reverse order. The length of the dredge rope was 3,000 fathoms, nearly three and a half miles. Of this, 2,000 fathoms were hawser-laid, of the best Russian hemp, 2 1/2 inches in circumference, with a breaking strain of 2 1/4 tons. The 1,000 fathoms next the dredge were hawser laid, 2 inches in circumference. Russia hemp seems to be the best material for such a purpose. Manilla is considerably stronger for a steady pull, but is more likely to break at a kink.THE STERN OF THE PORCUPINE.The frame of the largest dredge used weighed 225 pounds. The bag was double, the outside of strong twine netting, lined with canvass. Three sinkers, one of 100 pounds, and two of 56 pounds each, were attached to the dredge rope at 500 fathoms from the dredge. A description of the sounding made in the Bay of Biscay on the 22d of July, 1869, will give an idea of the process. When the depth had been ascertained, the dredge was let go about 4:45 p.m., the vessel drifting slowly before a moderate breeze. At 5:50 p.m. the whole 3,000 fathoms of rope were out. While the dredge is going down the vessel drifts gradually to leeward; and when the whole 3,000 fathoms of rope are out, she has moved so as to make the line from the dredge slant. The vessel now steams slowly to windward, and is then allowed to drift again before the wind. The tension of the vessel's motion, thus instead of acting immediately on the dredge, now drags forward the weight, so that the dredging is carried on from the weight and not directly from the vessel The dredge is thus quietly pulled along, with the lip scraping the bottom, in the position it naturally assumes from the center of weight of its iron frame and arms. If, on the contrary, the weights were hung close tothe dredge, and the dredge was dragged directly from the vessel, owing to the great weight and spring of the rope the arms would be continually lifted up, and the lip of the dredge be prevented from scraping. In very deep water this operation of steaming up to windward until the dredge rope is nearly perpendicular, after drifting for half an hour or so to leeward, is usually repeated three or four times. At 8:50 p.m. hauling-in is commenced, and the donkey-engine delivers the rope at a little more than a foot a second. A few moments before 1 o'clock in the morning the weights appear, and a little after one, eight hours after it was cast, the dredge appears and is safely landed on deck, having in the meantime made a journey of over eight miles. The dredge, as the result of this haul, contained 1 1/2 hundred weight of characteristic pale grey Atlantic ooze. The total weight brought up by the engine was as follows:2,000 fathoms of rope,4,0001,000 " "1,5005,500Weight of rope reduced to 1/4 in water1,375Dredge and bag275Ooze168Weight attached2242,042pounds.In many of the dredgings at all depths it was found that while few objects of interest were brought up within the dredge, many echinoderms, corals and sponges came to the surface sticking to the outside of the dredge bag, and even to the first few fathoms of the rope. The experiment was therefore tried of fastening to a rod attached to the bottom of the dredge bag, a half dozen swabs, such bundles of hemp as are used on ship-board for washing the decks. The result was marvelous; the tangled hemp brought up everything rough and movable that came in its way, and swept the bottom of the ocean as it would have swept the deck. So successful was this experiment, that the hempen tangles are now regarded asan essential adjunct to the dredge, and nearly as important as the dredge itself, and when the ground is too rough for using the dredge, the tangles alone are used.The mollusca have the best chance of being caught in the dredge; their shells are comparatively small bodies mixed with the stones on the bottom, and they enter the dredge with these. Echinoderms, corals and sponges, on the contrary, are bulky objects, and are frequently partially buried in the mud, or more or less firmly attached, so that the dredge generally misses them. With the tangles it is the reverse, the smooth heavy shells are rarely brought up, while the tangles are frequently loaded with specimens; on one occasion not less than 20,000 examples came up on the tangles in a single haul.In the Porcupine both derricks were furnished with accumulators, which were found of great value. The block through which the sounding line or dredging rope passed was not attached directly to the derrick, but to a rope which passed through an eye at the end of the spar, and was fixed to a bitt on the deck. On a bight of this rope, between the block and the bitt, the accumulator was lashed. This consists of thirty or forty, or more, vulcanized india-rubber springs, fastened together at the two extremities, and kept free from each other by being passed through holes in two wooden ends like barrel heads. The loop of the rope is made long enough to permit the accumulator to stretch to double or treble its length, but it is arrested far within its breaking point. The accumulator is valuable in the first place as indicating roughly the amount of strain upon the line; and in order that it may do so with some degree of accuracy it is so arranged as to play along the derrick, which is graduated, from trial, to the number of hundred weights of strain indicated by the greater or less extension of the accumulator; but its more important function is to take off the suddenness of the strain on the line when the vessel is pitching. The friction of one or two milesof cord in the water is so great as to prevent its yielding to a sudden jerk, such as is given to the attached end when the vessel rises to a sea, and the line is apt to snap.The results which have been gained by deep sea dredging are so important that the English Government recently fitted out another vessel, the Challenger, for such a cruise, with every appliance. This vessel is now due in New York.AQUARIUM.
DREDGING.
DREDGING.
DREDGING.
DREDGING IN MODERN TIMES—WHAT IT HAS TAUGHT US—DEEP SEA SOUNDINGS—FIRST ATTEMPTS—IMPLEMENTS USED FOR IT—THE CHANCE FOR INVENTORS.
In modern times we have learned a great deal more of the ocean than the ancients knew, from dredging. By this means we have become acquainted not only with the outline of the bottom, but have also become acquainted with the temperature of deep seas, with the varied forms of animal and vegetable life which are present there, and have come to know, with far greater certainty and completeness than ever before, the part which the ocean has played and is still playing in the preparation of the land.
By sounding, the ancients, of course, knew the depths of the shallow waters along their coasts. It would be the most natural thing for a sailor to tie a stone to a string, and let it down into the water, when he wanted to know whether it was deep enough to float his vessel, and the same means would also be used to discover whether there were any sunken rocksin such harbors as he was frequenting. But the ocean, to all antiquity, was unfathomable; they dared not attempt to cross it, and of course did not think they could measure its depth. Long after the ocean had been crossed by ships the belief was still current that it was impossible to measure its depth, and this belief was made the stronger by the unsuccessful attempts made in mid ocean to obtain soundings with the ordinary lead and line.
Before we arrived at a positive knowledge of the depth of the ocean, scientific men attempted to calculate it by various methods. Laplace, calculating the mean elevation of the land, supposed the sea must be of about equal depth. Young, drawing his deductions from the tides, calculated the depth of the sea. This method has been recently used to calculate the depth of the Pacific. A wave of a certain velocity indicates water of such a depth. In the case of the earthquake of 1854, in Japan, which caused a wave that extended to California, the rate of its progress afforded an indication of the mean depth of the sea it passed over, and authentic soundings taken since have confirmed the general accuracy of the calculation.
The ordinary lead used for soundings is a pyramid of lead, the bottom of which has a depression in it, which is filled with tallow; on striking the bottom a little of the sand or mud adheres to this tallow and is brought up to the surface. In this way something is learned about the depth and bottom of the sea, but not enough to satisfy the naturalists, who inquired whether it might not be possible to dredge the bottom of the sea in the ordinary way, and to send down water bottles and registering instruments to settle finally the conditions of the deep waters, and determine with precision the composition and temperature at great depths.
An investigation of this kind is beyond the powers of private enterprise. It requires more power and sea skill than naturalists usually have. It is a work for governments. Thatof the United States has contributed fully its share. The coast survey has added a great deal to our knowledge of the deep sea, and the ships of the navy took part in the soundings by which the existence of the plateau across the bed of the North Atlantic, which has been used for the ocean telegraphic cable, was proved.
In 1868 the English government provided the vessels and crews for the purpose of conducting deep sea dredgings, under the direction of Dr. Carpenter and Mr. Wyville Thompson. These expeditions have found that it is quite possible to work with certainty, though not with such ease, at the depth of 600 fathoms, as at a depth of 100; and in 1869 it carried on deep sea dredging at a depth of 2,435 fathoms, 14,610 feet, or very nearly three miles, with perfect success. Dredging in such deep water is very trying. Each haul occupied seven or eight hours, and during the whole of this time the constant attention of the commander was necessary, who stood with his hand on the regulator of the accumulator, ready at any moment to ease an undue strain, by a turn of the ship's paddles. The men, stimulated and encouraged by the cordial interest taken by the officers in the operations, worked with a willing spirit; but the labor of taking up three miles of rope, coming up with a heavy strain, was very severe. The rope itself, of the very best Italian hemp, 2 1/2 inches in circumference, with a breaking strain of 2 1/4 tons, looked frayed out and worn, as if it could not have been trusted to stand such an extraordinary ordeal much longer.
The ordinary deep sea lead used for soundings weighs from 80 to 120 pounds. The samples of the bottom which it brings up are marked upon the charts as mud, shells, gravel, ooze or sand, thus 2,000 m. sh. s. means mud, shells and sand at 2,000 fathoms; 2,050 oz. st. means ooze and stones at 2,050 fathoms; 2,200 m. s. sh. sc. means mud, sand, shells, and scoriæ, at 2,200 fathoms, and so on. When no bottom is found with the leadit is entered on the chart thus:——3,200, meaning no bottom was reached at that depth.
This method of sounding answers very well for comparatively shallow water, but it is useless for depths much over 1,000 fathoms, or six thousand feet. The weight is not sufficient to carry the line rapidly and vertically to the bottom; and if a heavier weight is used, the ordinary sounding line is not strong enough to draw up its own weight, and that of the lead from a great depth, and so breaks. No impulse is felt when the lead touches the bottom, and so the line continues running out, and any attempt to stop it breaks it. In some cases the slack of the line is carried along by currents, and in others it is found that the line has been running out by its own weight and coiling in a tangled mass on top of the lead.
These sources of error vitiate the results of very deep soundings. Thus Lieutenant Walsh, of the U.S. schooner Taney, reported 34,000 feet without touching bottom; and the U.S. brig Dolphin used a line 39,000 feet long without reaching bottom. An English ship reported 46,000 feet in the South Atlantic and the U.S. ship Congress 50,000 feet without touching bottom. These are, however, known to be errors, so that no soundings are entered on charts over 4,000 feet, and few over 3,000. The U.S. Navy introduced the first great improvement in deep soundings. This consisted in using a heavy weight and a small line. The weight, a 32 or 68-pound shot, was rapidly run down, and when it touched bottom, which was shown by the sudden change in the rapidity with which the line was run out, the line was cut and the depth estimated from the length of cord remaining on the reel. This, however, cost the loss of the shot and the line for each sounding.
One of the first attempts at deep sea dredging was made in 1818, by Sir John Ross, in command of the English navy vessel Isabella, on a voyage for the exploration of Baffin's Bay with a machine of his own invention, which he called a "deepsea clamm." It consisted of a pair of forceps, kept apart by a bolt, and so contrived that when the bolt struck the ground a heavy iron weight slipped down a spindle and closed the forceps, which retained a portion of the mud, sand, or small stones, from the bottom. With this instrument he sounded in 1,050 fathoms, and brought up six pounds of very soft mud, using a whale line, made of the best hemp, and measuring 2 1/2 inches in circumference.
The cup lead is another invention. With this there is a pointed cup at the bottom of the lead, fastened to it with a rod upon which a circular plate of leather plays, serving as a cover to the cup. As it strikes the bottom, the cup is driven in the mud, and on hauling up the cover is pressed into the cup by the water, and brings up the mud it contains. The objection to this is that it is too crude; in its passage up, the water washes away the mud, so that only on an average of once in three times does the cup come up with anything in it; and deep sea soundings take too much time, and are too valuable, to admit so large an average of loss.
About 1854 Mr. J. M. Brooke, of the U.S. Navy, who was at the time associated with Prof. Maury, so well known for his labor in gathering and diffusing a knowledge of the currents of the ocean, invented a deep sea sounding apparatus, which is known by his name. It is still in use, and all the more recent contrivances have been, to a great extent, only modifications and improvements upon the original idea, that of detatching the weight. The instrument is very simple. A 64-pound shot is cast with a hole in it. An iron rod, with a cavity in its end, fits loosely in the hole in the shot. Two movable arms at the top of the rod are furnished with eyes holding ends of a sling in which the ball hangs. The cavity at the end of the rod is furnished with tallow, and the apparatus is let down. On reaching the bottom, the rod is forced into the mud, the cavity becomes filled with it, and there being no more tension, on the rope holding up the movable arms, they fall, disengage the ends of the sling, and allow the ball to slide down the rod. The rod is then withdrawn, carrying up the portion of the bottom secured in the cavity at its foot, and leaving the ball on the bottom. This apparatus costs a ball each time it is used, and brings up but a small portion of the bottom, which is also apt to be diminished on its way to the top, by the water it passes through.
STRIKING THE SEA BOTTOM. BROOK'S DEEP SEA SOUNDING APPARATUS.
STRIKING THE SEA BOTTOM. BROOK'S DEEP SEA SOUNDING APPARATUS.
STRIKING THE SEA BOTTOM. BROOK'S DEEP SEA SOUNDING APPARATUS.
Commander Dayman, of the English Navy, in 1857 invented an improvement upon Mr. Brooke's original invention. He used iron wire braces to support the sinker, as these detach more easily than slings of rope. The shot he replaced by a cylinder of lead, as offering less surface to the water in its descent, and he fitted the cavity in the bottom of the rod with a valve opening inward. Commander Dayman used the apparatus, with these modifications, in the important series of soundings he made in the North Atlantic, while engaged in surveying the plateau for the ocean telegraphic cable, and reports that it worked well.
THE BULLDOG SOUNDING MACHINE.
THE BULLDOG SOUNDING MACHINE.
THE BULLDOG SOUNDING MACHINE.
The apparatus known as the bull-dog machine is an adaptation of Sir John Ross' deep-sea clamms, together with Brooke's idea of disengaging the weight. It was invented during the cruise of the English Navy vessel, the Bull-dog, in 1860, and the chief credit for it belongs to the assistant engineer during that cruise, Mr. Steil. A pair of scoops are hinged together like a pair of scissors, the handles represented by B. These are permanently fastened to the sounding rope, F, which is here represented as hanging loose, by the spindle of the scoops. Attached to this spindle is the rope, D, ending in a ring. E represents a pair of tumbler hooks, like those used so generally. C is a heavy weight, of iron or lead, hollow, with a hole large enough for the ring upon D to pass through. B is an elastic ring of India rubber, fitted to the handles of the scoops, and designed to shut them together as soon as theweight, C, which now holds them apart, is removed. When the bottom is reached, the scoops, open, are driven into the ground, the tension on the rope ceases, the tumbler hooks open and release the weight, which falls on its side, and allows the elastic ring to shut the scoops, inclosing a portion of the bottom in which they have been forced. The trouble with this apparatus is its complicated character; pebbles may get in the hinge and prevent the scoops from closing. In all apparatus to be used for such a purpose the greater the simplicity the better, and an invention, which shall at once be simple and effective, capable of bringing up a pound or two from the bottom at a depth of 2,000 fathoms or more, without fail, and without too much trouble, is still a desideratum, and its invention is well worth the attention of the ingenious.
Another arrangement, called the Hydra sounding machine, is intended to bring up portions of the bottom and water from the lowest strata reached. It consists of a strong brass tube, which unscrews into four chambers, closed with valves, opening upward, so that in the descent the water passes through them, freely; but when it is commenced to haul up, the pressure of the water closes the valves. This apparatus is also furnished with weights to sink it, which are released, on reaching the bottom, by a similar method to those described. This instrument was used during the deep sea sounding cruise of the Porcupine, and never once failed. Its faults are its complication, and that it brings up only small samples of the bottom. Captain Calver, who used it, could always, when at the greatest depths, distinctly feel the shock of the arrest of the weight upon the bottom communicated to his hand.
MASSEY'S SOUNDING MACHINE.
MASSEY'S SOUNDING MACHINE.
MASSEY'S SOUNDING MACHINE.
Various attempts have been made to construct instruments which should accurately determine the amount of the vertical descent of the lead by self-registering machinery. The most successful and the one most commonly used is Massey's sounding machine. This instrument, in its most improved form, is shown in the accompanying cut. It consists of a heavy oval brass shield, furnished with a ring at each end of its longer axis. To one of these a sounding rope is attached, and to the other, the weight is fastened at about a half fathom below the shield. A set of four brass wings or vanes are set obliquely to an axis, so that, like a windmill or propeller wheels, it shall turn by the force of the water as it descends. This axis communicates its motion to the indicator, which marks the number of revolutions on the dial plate. One of these dials marks every fathom, and the other every fifteen fathoms of descent. This sounding machine answers very well in moderately deep water, and is very valuable for correcting soundings by the lead alone, where deep currents are suspected, as it is designed to register vertical descent alone. In very deep water it is not satisfactory, from some reason which it is difficult to determine. The most probable explanation is that it shares the uncertainty inherent in all instruments using metal wheel work. Their machinery seems to get jammed in some way, under the enormous pressure of the water, at great depths.
To ascertain the surface temperature of the water of the sea is simple enough. A bucket of water is drawn up, and a thermometer is placed in it. With an observation of this kind the height of the thermometer in the air should be always noted. Until very recently, however, very little or nothing was known with any certainty about the temperature of the sea at depths below the surface. Yet this is a field of inquiry of very greatimportance in physical geography, since an accurate determination of the temperature at different depths is certainly the best, and frequently the only means, for determining the depth, the width, the direction and general path of the warm ocean currents, which are the chief agents in diffusing the equatorial heat; and more especially of those deeper currents of cold water which return from the poles to supply their places, and complete the watery circulation of the globe. The main cause of this want of accurate knowledge of deep sea temperatures is undoubtedly the defective character of the instruments which have been hitherto employed.
The thermometer which has been generally used for making observations on the temperature of deep water is that known as Six's self-regulating thermometer, inclosed in a strong copper case, with valves or apertures above and below, to allow a free passage of the water through the case and over the face of the instrument. This registering thermometer, consists of a glass tube, bent in the form of a U. One arm terminates in a large bulb, entirely filled with a mixture of creosote and water. The bend in the tube contains a column of mercury, and the other arm ends in a small bulb, partly filled with creosote and water, but with a large space empty, or rather filled with the vapor of the mixture and compressed air. A small steel index with a hair tied round it, so as to act like a spring against the side of the tube, and keep the index at any point it may assume, lies free in either arm, among the creosote, floating on the mercury. This thermometer gives its indications only from the expansions and contractions of the liquid in the large full bulb, and consequently is liable to some slight error, from the variations of temperature upon the liquids in other parts of the tube. When the liquid in the large bulb expands, the column of mercury is driven upward toward the half-empty bulb, and the limb of the tube in which it rises is graduated from below, upward, for increasing heat. When the liquidcontracts in the bulb, the mercury rises in this arm of the tube, which is graduated from above downward, but falls in the other arm. When the thermometer is going to be used, the steel indices are drawn down in each limb of the tube, by a strong magnet, till they rest, in each arm, upon the surface of the mercury. When the thermometer is drawn up from deep water, the height at which the lower end of the index stands in each tube indicates the limit to which the index has been driven by the mercury, the extreme of heat or cold to which the instrument has been exposed. Unfortunately, the accuracy of the ordinary Six's thermometer cannot be depended upon beyond a very limited depth, for the glass bulb which contains the expanding fluid yields to the pressure of the water, and compressing the contained fluid, gives an indication higher than is due to temperature alone. This cause of error is not constant, since the amount to which the bulb is compressed depends upon the thickness and quality of the glass. Yet, as in thoroughly well-made thermometers, the error from pressure is pretty constant, it has been proposed to make a scale, from an extended series of observations, which might be used to correct the observations, and thus closely approximate the truth.
A better plan has been proposed, and being practically applied, has been found to work very well. This consists in incasing the full bulb in an outer covering of glass, so that there shall be a coating of air between the bulb and the outside coating, and that this air being compressed by the pressure of the water outside, shall thus protect the inside bulb. Observations taken in 1869 with thermometers constructed in this way, as deep as 2,435 fathoms, in no instance gave the least reason to doubt their accuracy. A modification of the metallic thermometer, invented by Mr. Joseph Saxton, of the United States office of weights and measures, for the use of the coast survey, may be thus described. A ribbon of platinum and oneof silver are soldered with silver solder to an intermediate plate of gold, and this compound ribbon is coiled round a central axis of brass, with the silver inside. Silver is the most expansible of the metals under the influence of heat, and platinum nearly the least. Gold holds an intermediate place, and its intervention between the platinum and silver moderates the strain and prevents the coil from cracking. The lower end of the coil is fixed to the brazen axis, while the upper end is fastened to the base of a short cylinder. Any variation of temperature causes the coil to wind or unwind and its motion rotates the axial stem. This motion is increased by multiplying wheels, and is registered upon the dial of the instrument by an index, which pushes before it a registering hand, moving with sufficient friction to retain its place, when pushed forward. The instrument is graduated by experiment. The brass and silver parts are thickly gilt by the electrotype process, so as to prevent their being acted upon by the salt water.
The box in which the instrument is protected is open to admit the free passage of the water. This instrument seems to answer very well for moderate depths. Up to six hundred fathoms its error does not exceed a half degree, centigrade; at 1,500 fathoms it rises however to five degrees, quite as much as an unprotected Six thermometer, and the error is not so constant. Instruments which depend for their accuracy upon the working of metal machinery cannot be depended upon when subjected to the great pressure of deep soundings.
For taking bottom temperatures at great depths, two or more of the thermometers are lashed to the sounding line at a little distance from each other, a few feet above the sounding instrument. The lead is rapidly run down, and after the bottom is reached an interval of five or ten minutes is allowed before hauling in. In taking serial temperature soundings, which are to determine the temperature at certain intervals of depth the thermometers are lashed to an ordinary deep sealead, the required quantity of line for each observation of the series ran out, and the thermometers and lead are hove each time. The operation is very tedious; a series of such observations in the Bay of Biscay, where the depth was 850 fathoms and the temperature taken for every fifty fathoms, occupied a whole day. In taking bottom temperatures with a self-registering thermometer, the instrument of course simply indicates the lowest temperature to which it has been subjected, so that if the bottom stratum is warmer than any other through which the thermometer has passed, the result would be erroneous. This is only to be tested by serial observations; but from these it appears, wherever they have been made, that the temperature sinks gradually, sometimes very steadily, sometimes irregularly from the surface to the bottom, the bottom water being always the coldest.
Several important facts of very general application in physical geography have been settled by the deep sea temperature soundings which have been recently made, and the theories formerly held on this subject shown to be erroneous. It has been shown that in nature, as in the experiments of M. Despretz, sea water does not share in the peculiarities of fresh water, which, as has been long known, attains its maximum density at four degrees, centigrade; but like most other liquids increases in density to its freezing point; and it has also been shown that, owing to the movement of great bodies of water at different temperatures in different directions, we may have in close proximity two ocean areas with totally different bottom climates, a fact which, taken along with the discovery of abundant animal life at all depths, has most important bearings upon the distribution of marine life, and upon the interpretation of palaeontological data.
Mr. Wyville Thompson, who conducted the series of important deep sea soundings undertaken in the Porcupine, says very truly, "It had a strange interest to see these little instruments,upon whose construction so much skilled labor and consideration had been lavished, consigned to their long and hazardous journey, and their return eagerly watched for by a knot of thoughtful men, standing, note-book in hand, ready to register this first message, which should throw so much light upon the physical conditions of a hitherto unknown world."
Up to the middle of the last century the little that was known of the inhabitants of the bottom of the sea beyond low water mark, appears to have been gathered almost entirely from the few objects thrown up on the beaches after storms or from chance specimens brought up on sounding lines, or by fishermen engaged in sea fishing or dredging for oysters. From this last source, however, it was almost impossible to obtain specimens, since the fishermen were superstitious concerning bringing home anything but the regular objects of their industry, and from a fear that the singular things which sometimes they drew up might be devils in disguise, with possibly the power to injure the success of their business, threw them again, as soon as caught, back into the sea. Such superstitions are dying out, and in fact so singular are many of the animals hid in the depths of the sea; their forms and general air are so different from anything which the fishermen were used to see, that we can hardly wonder at the fear they excited. When, however, the attention of naturalists was turned toward the sea, they used the dredge such as was used by the oyster fishermen, and all the dredges now in use are simply modifications of this.
The dredge for deep sea operations is made with two scrapers, so that it shall always present a scraping surface to the bottom, however it may fall. The iron work should be of the very best, and weighing about twenty pounds. The bag is about two feet deep, and is a hand-made net of very strong twine, the meshes half an inch to the side. As so open a net-work wouldlet many small things through, the bottom of the bag, to the height of about nine inches, is lined with a light open kind of canvas, called by the sailors "bread-bag." Raw hides have been used for making the dredge bag, but, though very strong, they are apt to become too much so to another sense than touch. It is bad economy to use too light a rope in such operations, and best to fasten it to only one arm of the dredge, the eyes of the two arms being tied together with a thinner cord. In case, then, the dredge becomes entangled at the bottom, this cord will break first, and thus releasing one of the arms of the dredge, may so change the direction of the strain upon the rope as to free the dredge itself.
Dredging in deep water, that is, at depths beyond 200 fathoms, is a matter of some difficulty, and can hardly be done with the ordinary machinery at the disposal of amateurs. The description of the apparatus used in the Porcupine, in 1869 and '70, on her dredging cruise in the Bay of Biscay, will show what is necessary. These arrangements are also shown in the cut. This vessel, a gun-boat of the English navy, of 382 tons, was fitted out specially for this work. Amidships she was furnished with a double cylinder donkey-engine, of about twelve horse-power, with drums of various sizes, large and small. The large drum was generally used, except when the cord was too heavy, and brought up the rope at a uniform rate of more than a foot a second. A powerful derrick projected over the port bow, and another, not so strong, over the stern. Either of these was used for dredging, but the one at the stern was generally used for soundings. The arrangement for stowing away the dredge rope was such as made its manipulation singularly easy, notwithstanding its great weight, about 5,500 pounds. A row of some twenty large pins of iron, about two feet and a half long, projected over one side of the quarterdeck, rising obliquely from the top of the bulwark. Each of these held a coil of from two to three hundred fathoms, and the rope was coiled continuously along the whole row. When the dredge was going down, the rope was taken rapidly by the men from these pins in succession, beginning from the one nearest the dredging derrick, and in hauling up a relay of men carried the rope from the drum of the donkey-engine and laid it in coils on the pins, in reverse order. The length of the dredge rope was 3,000 fathoms, nearly three and a half miles. Of this, 2,000 fathoms were hawser-laid, of the best Russian hemp, 2 1/2 inches in circumference, with a breaking strain of 2 1/4 tons. The 1,000 fathoms next the dredge were hawser laid, 2 inches in circumference. Russia hemp seems to be the best material for such a purpose. Manilla is considerably stronger for a steady pull, but is more likely to break at a kink.
THE STERN OF THE PORCUPINE.
THE STERN OF THE PORCUPINE.
THE STERN OF THE PORCUPINE.
The frame of the largest dredge used weighed 225 pounds. The bag was double, the outside of strong twine netting, lined with canvass. Three sinkers, one of 100 pounds, and two of 56 pounds each, were attached to the dredge rope at 500 fathoms from the dredge. A description of the sounding made in the Bay of Biscay on the 22d of July, 1869, will give an idea of the process. When the depth had been ascertained, the dredge was let go about 4:45 p.m., the vessel drifting slowly before a moderate breeze. At 5:50 p.m. the whole 3,000 fathoms of rope were out. While the dredge is going down the vessel drifts gradually to leeward; and when the whole 3,000 fathoms of rope are out, she has moved so as to make the line from the dredge slant. The vessel now steams slowly to windward, and is then allowed to drift again before the wind. The tension of the vessel's motion, thus instead of acting immediately on the dredge, now drags forward the weight, so that the dredging is carried on from the weight and not directly from the vessel The dredge is thus quietly pulled along, with the lip scraping the bottom, in the position it naturally assumes from the center of weight of its iron frame and arms. If, on the contrary, the weights were hung close tothe dredge, and the dredge was dragged directly from the vessel, owing to the great weight and spring of the rope the arms would be continually lifted up, and the lip of the dredge be prevented from scraping. In very deep water this operation of steaming up to windward until the dredge rope is nearly perpendicular, after drifting for half an hour or so to leeward, is usually repeated three or four times. At 8:50 p.m. hauling-in is commenced, and the donkey-engine delivers the rope at a little more than a foot a second. A few moments before 1 o'clock in the morning the weights appear, and a little after one, eight hours after it was cast, the dredge appears and is safely landed on deck, having in the meantime made a journey of over eight miles. The dredge, as the result of this haul, contained 1 1/2 hundred weight of characteristic pale grey Atlantic ooze. The total weight brought up by the engine was as follows:
In many of the dredgings at all depths it was found that while few objects of interest were brought up within the dredge, many echinoderms, corals and sponges came to the surface sticking to the outside of the dredge bag, and even to the first few fathoms of the rope. The experiment was therefore tried of fastening to a rod attached to the bottom of the dredge bag, a half dozen swabs, such bundles of hemp as are used on ship-board for washing the decks. The result was marvelous; the tangled hemp brought up everything rough and movable that came in its way, and swept the bottom of the ocean as it would have swept the deck. So successful was this experiment, that the hempen tangles are now regarded asan essential adjunct to the dredge, and nearly as important as the dredge itself, and when the ground is too rough for using the dredge, the tangles alone are used.
The mollusca have the best chance of being caught in the dredge; their shells are comparatively small bodies mixed with the stones on the bottom, and they enter the dredge with these. Echinoderms, corals and sponges, on the contrary, are bulky objects, and are frequently partially buried in the mud, or more or less firmly attached, so that the dredge generally misses them. With the tangles it is the reverse, the smooth heavy shells are rarely brought up, while the tangles are frequently loaded with specimens; on one occasion not less than 20,000 examples came up on the tangles in a single haul.
In the Porcupine both derricks were furnished with accumulators, which were found of great value. The block through which the sounding line or dredging rope passed was not attached directly to the derrick, but to a rope which passed through an eye at the end of the spar, and was fixed to a bitt on the deck. On a bight of this rope, between the block and the bitt, the accumulator was lashed. This consists of thirty or forty, or more, vulcanized india-rubber springs, fastened together at the two extremities, and kept free from each other by being passed through holes in two wooden ends like barrel heads. The loop of the rope is made long enough to permit the accumulator to stretch to double or treble its length, but it is arrested far within its breaking point. The accumulator is valuable in the first place as indicating roughly the amount of strain upon the line; and in order that it may do so with some degree of accuracy it is so arranged as to play along the derrick, which is graduated, from trial, to the number of hundred weights of strain indicated by the greater or less extension of the accumulator; but its more important function is to take off the suddenness of the strain on the line when the vessel is pitching. The friction of one or two milesof cord in the water is so great as to prevent its yielding to a sudden jerk, such as is given to the attached end when the vessel rises to a sea, and the line is apt to snap.
The results which have been gained by deep sea dredging are so important that the English Government recently fitted out another vessel, the Challenger, for such a cruise, with every appliance. This vessel is now due in New York.
AQUARIUM.
AQUARIUM.
AQUARIUM.