CHAPTER LVII

CHAPTER LVIITHE DEVELOPMENT OF SHIP BUILDING—NEW MODELS FOR SHIPS—STEAM SHIP NAVIGATION—MONITORS—IRON-PLATED FRIGATES—TIN CLADS—RAMS—TORPEDO BOATS—THEIR USE IN THE CONFEDERACY—LIFE RAFTS—YACHT BUILDING—OCEAN YACHT RACE—THE COST OF A YACHT.From the oars, which were the only means of propulsion used in the galleys of antiquity, to the sails of a subsequent period, by which only favoring winds could be made use of, the advance was great, but not as great as the discovery of steam, by which in modern times the sea is traversed with but little regard for the condition of the wind. To suit the different means used for the propulsion of these vessels, modifications have been made in the manner of their construction, in their form, and with sailing ships in the arrangement of sails. When, with the successful termination of the war of the Revolution, the United States first took its place in the world as an independent nation, the commercial activity which was the natural result of the greater political freedom resulting from the issue of that contest, found its expression first in our commerce; and the self-reliance, which is the inevitable result of liberty; the spirit of inquiry fostered by a departure from old methods, and the abandonment of old traditions, were displayed in the construction, the rig and the general air of the vessels then built, as much as in the construction of the political organization of the new republic.So much was this the case that American vessels became known the world over for their trim and neat appearance. The blunt, rounded prows and heavy sterns of the English orDutch vessels were replaced by American models, sharp, nothing superfluous, and riding the waters as easy as a bird. The American clipper ships became renowned for their quick passages, and in transporting teas from China made fortunes for their happy owners, by bringing to the markets the first cargoes of the new crops.The same thing occurred when steam-vessels first began to cross the ocean. The English in their first steamers followed the models of their largest sailing ships. They still preserved the heavy bowsprit, projecting twenty to thirty feet in advance of the prow, though it was not necessary, as in their sailing ships, for balancing the pressure of the other sails. Their steamers were therefore always heavy at the head, and when, in a rough sea, they were driven by the power of the engine, buried their bows in every large wave. Any one who has crossed the Atlantic in an English steamer of twenty years ago, must have noticed how heavily it labored in rough weather, and how the waves broke over her bow. To take in tons of salt water when the waves ran high, was usual; and in a passage across the Atlantic it was no rare thing to have the salt encrusted on the smoke-stack, from the waves which dashed over the bow and swept aft, reach a thickness of from one to two inches.PENNSYLVANIA AND OHIO ON THE STOCKS.The American ship-builder, however, early saw that the model of his craft, which was to be propelled by steam, should differ from that of a ship depending upon its sails alone, and governed himself accordingly. He made her sharp, for speed, and ended her prow straight up and down, as he built the steamboats for river navigation. The consequence was that she rode dry through waves which would pour tons of salt water upon the deck of an English model. George Steers, of New York, a genius in naval architecture, and whose early death was deeply regretted, was the person who did the most to bring into use the present form used in the best models for ocean steamers. One of his first steamers, the Adriatic, built for the Collins line, excited great attention in Liverpool, when she first appeared there. The LondonTimesspoke of her in leading articles, calling upon the English ship-builders to contrast her with ships of their own construction. It spoke of how she glided up the Mersey, making hardly a ripple from her bows, so evenly and quietly she parted the water, while an English steamer of her size so disturbed the stream as to bring up the mud from the bottom. TheTimeswas also specially struck with the ease with which she was handled, turning almost in her length, while for an English steamer turning was an operation requiring so much more space, andmaking so much more disturbance in the water. From that time to this the English have followed the American models in the construction and equipment of their steamers, and their example has been imitated by most other nations.The latest specimens of American ship building are shown in the cut representing the Pennsylvania and Ohio on the stocks. These vessels are the pioneers of the new line between Philadelphia and Liverpool.Nor is this the only change which naval architecture has undergone. The material for ship-building, especially for sea going steamers, has in modern times come to be chiefly iron. Livingstone, in his book of travels in Africa, tells how, when he was putting together on the banks of one of the rivers there the pieces of a small iron steamer which had been sent out to him from England, the natives gathered round, and inspecting the work going on, jeered at him for thinking that a boat built of such a material would float. Their whole experience with iron was that it would sink. When, however, the steamer was completed and launched, they could hardly express their astonishment at finding that she floated.Though every school-boy, from his text-books on natural philosophy, can explain the reasons why a ship built of iron will float, yet our ancestors would have considered, a proposition to construct a ship from this material very much as the native Africans did. Even in the construction of wooden ships, iron enters now much more than it did formerly. The knees, or bent oak beams, by which the form of the ship was made, have become so scarce and dear that they are now frequently made of iron. It takes so long for an oak tree to grow, and the demand was so great for limbs of such a natural bend as could be used for ship-building, that even before the use of iron for such portions of a ship, the process was in frequent use of bending the beams, or knees, by steaming then and then subjecting them to great pressure.Iron as a material for ships has some very great and material advantages. It is on the whole lighter, so that an iron ship weighs less, absolutely, than a wooden one of the same size. Then as the knees and other timbers take up less space when made of iron, than when made of wood, and as the thickness of the sides is much less, more space is secured in an iron ship than in a wooden one for carrying the cargo. Besides this, a vessel built of iron can be divided into water-tight compartments, so that an accidental leak will damage only that portion of the cargo contained in that compartment in which it occurs.This method of construction is also another factor of safety in case of accident by collision or in any other way. One compartment may be injured so as to fill with water, while the others, being uninjured, their buoyancy will still keep the ship afloat. An objection, however, to the use of compartments lies in the fact that, as they must be riveted to the sides, the rows of holes for the rivets necessarily weaken the strength of the sides, so that a ship with compartments, which touches on a rock or other obstacle, at one end, is more apt to break apart than one without compartments, as the sides, unsupported by the buoyancy of the water, have the less strength to support her weight in the length. Still, all things considered, iron has come so much in favor for the construction of large ships, that it is in much more general use for that purpose than wood.In the construction of an iron ship, the naval architect draws his plans, and sends his construction drawings to the iron rolling mill, where each plate is made of the exact curve and dimensions. The holes for the rivets are punched by machinery, and the plates are then ready to be put together. The hull of the vessel is made of iron bars riveted together, and the plates are riveted to the iron upright ribs, each plate overlapping the preceding. The ribs are placed from ten to eighteen inches apart, and the whole structure is of iron. The simplicity of the construction of an iron ship is such, that when the plates are ready, it can be put together with wonderful rapidity.MONITORS.PLANS OF THE MONITOR.ST. LOUIS.For constructing ships of war, iron is almost wholly used, and the experience of our late war has almost entirely changed the methods and theories of naval warfare. The enormous frigate, carrying a heavy armament of numerous guns, and manned by a thousand men, has been replaced by a small craft—so low in the water as to project above it only a few inches, carrying but a single gun, or at most only two, which are of very heavy calibre, and are mounted in a revolving tower in the middle of the craft. The general description of the Monitor, that it was a cheese-box on a raft, aptly describes their appearance.By the introduction of the monitor as a war vessel, a complete change was wrought in naval warfare. The large hulk of the old ships afforded only a better target for the heavy guns of this new craft, while its own slight projection above the water, and the fact that its engines and propeller were covered by the water, afforded it almost absolute security from the enemy's guns. Even if it was struck, the round shape of its iron clad deck, and its revolving tower caused the balls to glance off without affecting much injury. In October, 1861, forty-five days from the laying of her keel, the St. Louis was launched, being the first iron-clad ship owned by the United States. Other vessels of similar design were rapidly brought to completion, and these iron-clad river boats began their task of opening the navigation of the Mississippi. The St. Louis was built in the city of the same name, by Mr. James B. Eads, of that city.DOUBLE ENDER.The cuts represent the shape of some of the iron-clads built for service in the western rivers, where the shallowness of the stream made it necessary that the craft should not draw too much water.For the same reasons the "tin-clads," as they were called from the thinness of the plates with which they were covered, were built. The "double-enders" were also thus constructed, in order to navigate, as necessary, either way, in the narrow and crooked streams, where our navy performed such admirable work during the War.The use of heavy artillery in naval warfare has also caused great modifications to be made in the construction of other naval ships than the monitors. To avoid the injury caused by heavy artillery, the idea was suggested of plating them with iron. The most extensive experiments of this kind were made in England, but not with the most gratifying success. It was found that the iron plating rendered the ships too heavy, if it was made thick enough to be of effective service. In a rough sea the vessels rolled so heavily as to be nearly unmanageable, while the weight of the plating on the sides acted with a leverage to tear the ships in halves, so that they were considered almost unsafe. One of them, also, on her trial trip, having capsized and sunk with her entire crew, public confidence in them as serviceable vessels was entirely lost; and the advantage of iron-plating large ships of war may be still considered as an open question.MINNEHAHA, OR TIN-CLAD.It has also been suggested that ships of war should be furnished with a sharp beak of steel, and with such powerful engines as should secure for them great speed, and, without trusting at all to the use of their guns, should be used as rams to run into and crush their adversaries. This suggestion, which is practically returning to the practice of the ancients before the invention of either gunpowder or steam, has never yet, however, been carried out in fact. So far, therefore, the most serviceable modern ships of war are the monitors. The largest and most expensive of these, the Dunderberg, was not finished until after the war was over, and was sold, with the consent of the government, by her builder, to Russia for $1,000,000, and crossed the Atlantic safely, a feat which showed her to be sea-worthy, and more worthy of confidence than any of the armored vessels built by the English Government.In modern times attention has also been given to constructing vessels which should be navigated under the water. Fulton, whose name is so inseparably connected with the introduction of the steamboat, made an attempt, the first on record, in the harbor of Brest, on the west coast of France, in 1801, under the order of Napoleon I., to blow up an English ship with a torpedo, a weapon of warfare which is said to have been first suggested by Franklin, who experimented with them in the Revolution. Fulton used, in this attempt, a submarine boat of his own invention, the model and construction of which have never been made public. His attempt being unsuccessful the project was abandoned, as Napoleon withdrew his support from the scheme.THE RAM IRONSIDES.During our late civil war, while the harbor of Charleston, South Carolina, was blockaded by the ships of the national navy, and the bombardment of Fort Sumter continued, attempts were made by the besieged to destroy the blockading ships by torpedoes, which were to be fastened by a submarine craft. One of these boats, called a "cigar boat," though both ends were pointed, is thus described: She was thirty feet long and six feet broad, painted a lead color. Her propelling power consisted of a six-horse engine, geared to a shaft turning a propeller. At her bow was an iron bowsprit, so arranged that it could be lowered to the required depth, and at the end of this the torpedo was secured. When afloat only about fifteen feet of her length projected some fourteen inches above the water. For fuel she used anthracite coal, and attained a speed of about six miles an hour. Her tonnage was about seven or eight tons, and in this craft Lieutenant Glassells, of Virginia, volunteered to attack the iron-clad, the Ironsides, which was the most powerful ship at that time afloat in the navy, rated at from three to four thousand tons. The Ironsides was a very heavily armed ship, provided with eleven-inch guns, and capable of delivering the heaviest broadside ever fired from a single ship. On the night of the sixth of October, 1863, Lieutenant Glassells set out on his expedition from one of the wharves of Charleston. The sky was covered with clouds, and the night was very dark. His crew consisted of a fireman and a pilot, and his offensive armament of a torpedo, in position, and a double-barreled fowling-piece. Being asked why he carried a gun on such an expedition, he answered: "You know I have served in the United States navy, and I shall not attack my old comrades like an assassin. I shall hail and fire into them, with this, then let the torpedo do its work like an open and declared foe." This speech is a fair specimen of the singular mixture of honor and disloyalty which characterized the whole secession movement. This lieutenant could desert his navy, could take up arms against his country, but could not attack one of its ships without first giving its crew warning.TORPEDO EXPLOSION.The "cigar boat" steamed silently on its course until within about fifty yards of the Ironsides, without being discovered. Everything on the immense ship seemed as quiet as the grave. Suddenly, in the still night, the lieutenant cries, "Ship ahoy!" "Where away?" is the answer. "We have come to attack you," cries the lieutenant, at the same time firing his fowling-piece, checking the engine, and directing the torpedo. It struck, but before the "cigar boat" could retire, with a gurgling roar it exploded. The explosion sounded like the discharge of a submerged gun. Water mixed with flame was forced by the explosion far up above the gunwales of the ship, and bearing up the bows of the smaller craft, poured back intorrents through the chimney, put out the fires, and rendered the "cigar boat" helpless.For a moment everything on board the Ironsides was in confusion; but the discipline of the navy was equal to the emergency. The drums beat to quarters, the guns were manned, and the marines poured a steady fire upon the little craft, now floating helplessly on the sea. Lieutenant Glassells jumped into the water, to escape death from the shower of balls; the pilot followed him, but the fireman remained at his post, as the boat drifted away from danger. Glassells then called for help; the marines ceased firing, and a small boat from the Ironsides rescued him from the water. The pilot swam back to the "cigar boat" and he and the fireman bailed her out, rekindled the fire, and escaped to Charleston. Glassells was afterwards sent North, and under confinement his health broke down. The Ironsides was sufficiently injured by the explosion to be sent from her station for repairs. Had the torpedo struck her further below, it is thought to be probable that she would have been sunk.Another torpedo boat was also built in Charleston, upon a different model. This was called the "fish boat." It was built of boiler-iron, was thirty feet long by five feet eight inches deep, and about four and a half feet wide, amidships. Its middle section was an ellipse flattening to a wedge shape at both ends, which were alike. It was intended to rise or sink in the water, like a fish, and in order to do this its specific gravity had to be kept equal that of water. In navigating under water the boat had also to be kept upon an even keel. On her bowsprit, which projected ten feet, the torpedo was secured, and in order to balance the hundred and fifty pounds this weighed, an equal amount of ballast was stowed at the stern. Ten feet from her bow she had two iron fins, one on each side, about four feet long, seven inches wide and three-eighths of an inch thick. These fins were fastened to an inchrod of iron passing through water-tight fittings in her sides, and provided with a crank inside, so that the fins could be worked in any direction, or at any angle, forcing the craft to the surface, or below, or forward or backward. By working them also in opposite directions the vessel could be turned as a row-boat is by pulling with one oar and backing water with the other. At the stern, midway between the top and bottom, she was provided with a propeller, worked by a shaft, fitted water-tight, and propelled by hand-power inside the hold. On her deck were two round hatches, or man holes, about ten feet apart, and fitted with plates of such thick glass as is used in side-walks, for cellar lights, set in iron frames, working upon hinges, fastened on the inside, and fitting water-tight when closed. Between these hatches were two flexible air pipes, with air-tight valves, so that when within a foot of the surface, by opening the valves, fresh air could be drawn into the hold. The crew depended upon the violent action of their hats, when the valves were open, for making a current sufficient to displace the foul air, and bring in a supply of fresh.When the boat was finished, in the first experiment made with her, she carried a crew of eight men, and a shifting ballast of iron plates. She moved from the wharf, passed down the river, just showing the tops of the hatches, dove under a ship lying in the stream, rose on the other side, and returned to the wharf. This was done successfully a second time, when the chief of the crew left her for some purpose, and the rest of the men, though unaccustomed to the work, undertook to perform the experiment alone. She moved out, dove down, but never came up. About a fortnight afterward she was found, raised, the dead removed, and the whole inside disinfected, cleaned and painted white. On the second trial she filled just as the crew had manned her, and sunk. The captain and one other saved themselves, but the rest of the crew, consisting of five, were drowned in her. Another crew volunteered to man her, andon the night of the 17th of February, 1864, she set out from Sullivan's Island, to which place she had run from her anchorage, to attack the blockading fleet, carrying a torpedo affixed to her bowsprit.During the whole night the bombardment of the city was kept up, and nothing was heard of the fish boat. The next morning a heavy fog hung over the coast, clearing up about eight in the morning, and the sloop-of-war Housatonic was discovered to be sunk in about six fathoms of water, her crew swarming in her rigging for safety. The fish boat had destroyed her, and destroyed herself in doing so. This was the first time that she had ever been used in exploding a torpedo, and the cause of her destruction is supposed to have been as follows: The weight of the torpedo, on her bowsprit, was balanced by the shifting ballast in her stern, and thus she was kept on an even keel. As soon, however, as the torpedo struck and exploded, the balance was destroyed, her bows were lifted by the weight in the stern, control was lost of her, and the Housatonic, sinking from the damage done her by the explosion, settled upon the "fish boat" and carried her and her crew to the bottom.Disastrous as these attempts at submarine navigation were, yet they are the most successful yet made. We have seen else where that men have, for other purposes than war, been able to descend under the surface of the sea, and stay there quite a time without injury; but their appliances are not vessels intended for navigation.Let us turn, then, from this record of how human ingenuity has been taxed to devise means to destroy men, to the consideration of the new devices made for their comfort or safety in crossing the sea. One of the most useful of these is a life raft or bolsa, one of which is represented in our cut. This consists of three elastic cylinders, made of india-rubber cloth, each twenty-five feet long. When empty they are easily packedin a very small compass. For use they are blown up, and fastened to a prepared staging. The cut represents one which crossed the Atlantic in 1867, arriving at Southampton July 25, having started from New York forty-three days before. She was rigged with two masts secured to the staging, and her crew consisted of three men, John Wilkes, George Miller and Jerry Mallene. A bellows to fill the cylinders, should they require it, was an important item in her cargo. The crew kept alternate watch, sleeping, by turns, in a tent spread on the staging. Their supply of water they carried in casks. The experiment of crossing the Atlantic was made to show the safety of a raft thus constructed.LIFE RAFT.For attaining speed, and thus diminishing the tedium and the risk of an Atlantic voyage, Mr. Wynans, of Baltimore, has invented a cigar-shaped boat, as it is called, though it is pointed at both ends. Various causes have hitherto prevented his final experiment with his boat, but he hopes to be able tomake with it an average speed of at least eighteen miles an hour.Crossing the Atlantic has become so common, and sea-sickness making the trip so disagreeable and dangerous to many people, attention has been turned to inventing a method of construction which shall destroy the cause for this malady, by keeping the saloon always on a level, notwithstanding the pitching and rolling of the ship in a high sea. Mr. Bessemer, the inventor of the new process for making steel, has invented a boat, which he is now constructing, and which he thinks will make it perfectly feasible to cross the Atlantic without the necessity of paying the usual tribute to old Neptune. The general idea of his ship may be thus described: The saloon for passengers is to be balanced upon a frame work similar in principle to that by which the lamps on ship-board are supported. An outer circle swings upon pivots at each end of its diameter, and within another circle supports the lamp, which is swung upon pivots at right angles with those in the first. However, then, the ship may pitch or roll, the lamp remains perpendicular, the circles adjusting themselves to meet the motion of the ship. This idea is to be applied in the construction of the saloon, so that it will remain constantly on a level, and as Mr. Bessemer has a plenty of money to construct a dozen of ships for an experiment, the public may expect before long to hear of a trial. The first ship of the kind is reported as on the stocks, and to be rapidly approaching completion. Nor is this the only style of ship suggested to obviate sea-sickness. A Russian, M. Alexandroiski, proposes a new form of stationary ship-saloon, which differs from that of Mr. Bessemer in having the cabin float in kind of a tank placed between the engines, instead of being hung on pivots. This invention, it is stated, has been tested by the Russian Naval Department, and is reported to have been found entirely satisfactory, the rolling motion of the vessel being completelycounteracted. With the success of one or the other of these plans, an ocean voyage, even in a rough sea, will become a pleasure trip, like sailing in a painted ship upon a painted ocean; the wildness of a storm even may become merely an exciting spectacle, like looking at the representation of a hurricane in a theatre, with the further advantage of having it real and life-like.Perhaps the change which has been brought about in our feeling with regard to the ocean is shown more in the yachting of modern times than in anything else. The idea of making a trip across the Atlantic is no longer considered an almost foolhardy undertaking, but even our yachts have made it a field for their races, and a match across the Atlantic has become not an unusual thing. The owning of yachts has become so general among our rich men, that yacht-building has become a regular branch of naval architecture, and constant improvements are being made in their models, and greater luxury displayed in their fitting up. George Steers, who has been mentioned before for his improvements in the model of the steamship, made his first reputation by the construction of the yacht America, which was sent over to England, and proved the fastest vessel in the regatta on the occasion of the first World's Fair in London. This yacht, after her victory, was bought by an Englishman, and never used again, being left to rot at her moorings. However, she changed the yacht models of Europe.OCEAN YACHT RACE.—THE HENRIETTA, VISTA AND FLEETWING.A yacht race across the Atlantic was one of the sensations of the year 1866. Three yachts entered the contest, the Henrietta, the Fleetwing and the Vista. They started from Sandy Hook one day in December, and though the season had been unusually stormy, and they encountered gales almost all the way, so that frequently they were forced to sail under bare poles, and the Fleetwing lost several of her sailors, who were washed overboard, yet they arrived safe at Cowes on the same day, after a fourteen days' voyage, the Henrietta winning the race by a couple of hours. This yacht was the property of James Gordon Bennett, Jr., the son of the owner of the New York Herald. During the war her owner freely offered her to the government, and she has done good service. After the victory Mr. Bennett sold her for $15,000, and purchased the Fleetwing for $65,000, re-christening her the Dauntless. This yacht, in another ocean race in 1870, was beaten by the Cambria, an English yacht. These prices show the cost of seeking one's pleasure in a yacht, and yet it is only one item of the expense. To keep one of the vessels costs more than the expenses of the majority of the households in the country. A crew of five men is needed, and it is a question whether, all things considered, more real substantial interest and enjoyment is not taken by a lover of the sea and of sailing in an ordinary sail-boat, which he and a friend or two are amply competent to man and manage, than is taken by the owners of the most luxuriantly furnished yachts in the world. As pleasure ships, however, the yacht is all that can be desired. Many of them contain spacious saloons; their cabins are almost always paneled in costly woods, and most luxuriantly furnished, and even gas has been provided for them. It is estimated that the yachts of the New York club alone have cost more than $2,000,000, and those of the whole country about $5,000,000. Much of this is the mere luxury of ostentation; but as the real pleasures there are in thus visiting distant lands come to be better appreciated, much of this foolish expenditure will be abandoned.CHAPTER LVIII.OUR KNOWLEDGE OF THE EARTH AND SEA—HOW IT HAS INCREASED—THE EARTH THE DAUGHTER OF THE OCEAN—THE OPINION OF SCIENCE—THE MEAN DEPTH OF THE OCEAN—THE EXTENT OF THE OCEAN—ITS VOLUME—SPECIFIC GRAVITY OF SEA-WATER—CONSTITUTION OF SALT-WATER—THE SILVER IN THE SEA—THE WAVES OF THE SEA—THE CURRENTS OF THE OCEAN—THE TIDES—THE AQUARIUM—THE COMMERCE OF MODERN TIMES—THE SPREAD OF PEACE.In the preceding pages the facts have been given in a comprehensive though succinct form, which enable us to see how, step by step, each one of which became possible only when those preceding had been taken. Mankind has gained a knowledge of the outlines of the sea; of the form of the earth itself; of the relative positions occupied by the water and the land; of their action upon each other, and thus the way has been prepared by the enterprise of preceding generations for the scientific methods of study which characterize the modern era. The adventurous voyagers of the early times, who, daring as they were, hardly were bold enough to venture in their open boats, propelled only by oars, out of the sight of land, could not be expected to conceive that it could be possible for men, like themselves, to ever become able to construct ships such as modern nations construct, in which, propelled by steam, voyages should be taken across oceans, and out of sight of land, their course over the trackless waters be guided with accuracy and certainty, to any desired point, by the compass and the observations of the motions of the stars.By experiment and observation the entire aspect and conception of the ocean has been changed in modern times from that which prevailed in antiquity, or even more recently, until within the few past generations. Though much has been done, in the study of the ocean, toward obtaining a proper conception of its influence in the general economy of the globe, yet thereis still much to be learned. Among the ancients it was generally declared in their cosmogonies that the solid portions of the world were produced by the ocean. "Water is the chief of all," says Pindar; "the earth is the daughter of ocean," is the mythological statement common to the primitive nations. Though this poetical expression was merely based upon a vague tradition, and can hardly be taken as the result of any methodical study of the earth, yet modern science tends to show that it is really true. The ocean has produced the solid land. The study of geology, the skilled inspection of the various strata of the land—the rocks, sand, clay, chalk, conglomerates—proves that the materials of the continents have been chiefly deposited at the bottom of the sea, and raised to their present position by the chemical or mechanical agencies which are constantly at work in the vast laboratory of nature.Many rocks, as for instance the granites of Scandinavia, which were previously believed to have been projected in a molten and plastic state from the interior of the earth, where they had been subjected to the action of the intense heat supposed to exist in the centre of the earth, are now supposed to be in reality ancient sedimentary strata, slowly deposited by the sea, and upheaved by the contraction of the crust, or by some other force of upheaval acting from the centre. Upon the sides of mountains, or on their summits, now thousands of feet above the level of the ocean, unquestionable traces of the action of the sea can be found. And the scientific observer of to-day sees all about him evidences that the immense work of the creation of continents, commenced by the sea in the earliest periods of time, is to-day continuing without relaxation or intermission, and with such energy that even during the short course of a single life great changes can be seen to have been produced. Here and there a coast, subject to the beating of the serf, is seen to be slowly undermined, disintegrated, worn down and carried away, while in another place the material is depositedby the sea, and sandy beaches or promontories are built up. New rocks also, differing in appearance and constitution from those worn away, are formed. But beside this action of the sea upon the coasts, in constantly changing the configuration of the land, modern observation has shown us that animal life is an agent constantly at work within the sea itself, in the formation of new lands. The innumerable minute forms of life with which the sea swarms; the coral polyps, the shells, the sponges, and the animalculæ of all kinds, are constantly engaged in consuming the food they find, in reproducing themselves, and in dying. From the various matters brought down to the ocean by the rivers of the land, they secrete their shells or other coverings; and as generation after generation they die, these falling to the bottom form immense banks, or plains, which some future action of upheaval will bring above the surface to form the material for new continents or islands.Thus while the ocean prepares the materials for the future continents in its bosom, it also furnishes the waters which wash away the lands already existing. To the thought of modern science the granite peaks, the snow-clad mountains, immovable and eternal as they seem, are constantly disintegrating, and partake, with every thing else in creation, the eternal round of change which is constantly going on. From the sea, by evaporation, rise the vapors which, condensing against the sides of the mountains, form the glaciers; and these, slowly sliding down toward the plains, are such efficient agents in wearing away the mountains, grinding up their solid rocks and preparing the gravel which the mountain streams distribute over the plains. From the sea the atmosphere receives the moisture destined to return in rain from the clouds; to feed the brooks whose union forms the rivers, destined again to return to the sea the waters it provided, and thus keep up, in a single, mighty and endless circulation, the waters of the globe.Thus to the agency of the ocean we are indebted for our rivers, which have played such an important part in the geological history of the earth, in the distribution of the flora and fauna of various countries, and on the life of man himself. In the study also of the climates of the earth, and their effects upon life, we find the ocean bears a most important part. As the circulation of the atmosphere mingles the heated air from the equator with that of the frozen regions of the poles, so the currents of the ocean circulate about the earth, blending the contrasts of climate, and making a harmonious whole of all the different portions. Thus, instead of considering the ocean as the barren waste of desolation it appeared to the ancients, to the modern thinker the ocean has, layer by layer, deposited the land from its bosom, and now by its vapors provides the rains which support its vegetable life, upon which all other life depends, and creates the rivers and the springs, which play such an important part in the modification of the interior of continents, at the greatest distance from the sea.The mean depth of the whole mass of the ocean waters of the globe is estimated at about three miles, since measurements have shown that the basins of the Atlantic and Northern Pacific are deeper than this by hundreds of thousands of fathoms. The extent covered by the surface of the ocean has been estimated at more than 145,000,000 of square miles, and with this estimate, the sea is calculated to form a volume of about two and one-half million billions of cubic yards, or about the five hundred and sixtieth part of the planet itself. The highest point of the land raised above the level of the sea is much less elevated than the bottom of the sea is depressed from the same level, so that the mass of the land above this level can be estimated only at about a fortieth part of the mass of the waters.The specific gravity of sea water is greater than that offresh. This comes from the various matters which it holds in solution. This difference varies with different seas; with the quantity of matters held in solution; with the amount of evaporation; the size and number of rivers flowing into the various seas; the ice melting into them; the currents, and various other causes. The average quantity of salts held in solution in sea water is estimated at 34.40 parts in 1,000, and this average is the same in all seas. The quantity of common salt held in solution is always a little more than three-quarters (75.786) of the total mineral matter held in solution. The salt of the sea averages, if the water is evaporated, about two inches to every fathom; so that, were the ocean dried up, a layer of salt about two hundred and thirty feet thick would remain on the bottom, or the whole salt of the sea would measure more than a thousand millions of cubic miles. This vast quantity of salt in the sea explains how the enormous beds of rock salt were formed, when the lands now exposed were covered by the waters.Beside the oxygen and hydrogen which constitute its waters, the sea contains chlorine, nitrogen, carbon, bromine, iodine, fluorine, sulphur, phosphorus, silicon, sodium, potassium, boron, aluminium, magnesium, calcium, strontium, barium. From the various sea-weeds most of these substances can be obtained. Copper, lead, zinc, cobalt, nickel and manganese have also been found in their ashes. Iron has also been obtained from sea water, and a trace of silver also is often deposited by the magnetic current established between the sheeting of ships and the salt water. Though only a trace is thus found, yet it has been estimated that the whole waters of the ocean contain in solution two million tons of silver. In the boilers of ocean steamships, which use sea water, arsenic has also been found.Sea water also retains dissolved air better than fresh water, and the bulk of this in ocean water is generally greater by athird than that found in river water. It varies from a fifth to a thirtieth, and gradually increases from the surface to a depth of about three hundred and twenty-five to three hundred and eighty fathoms. The uniformity in the constitution of the waters of the sea is chiefly caused by the action of the waves, which finally mix and mingle the waters into a homogeneous mass. The waves of the sea are caused chiefly by the action of the wind, and the effect continues even after the wind has ceased. One of the grandest spectacles at sea is offered by the regular movement of the waves in perfectly calm weather, when not a breath of air stirs the sails. During to the Autumnal calm under the Tropic of Cancer, these waves appear with astonishing regularity at intervals of two hundred to three hundred yards, sweep under the ship, and as far as the eye can reach, are seen advancing and passing away, as regularly as the furrows in a field. Such waves are caused by the regularity of the trade winds. The height of the waves is not the same in all seas. It is greater where the basin is deeper in proportion to the surface, and also as the water is fresher and yields easier to the impulses of the wind.The height of waves has been variously measured. Some observers have claimed to see them over one hundred feet high, but from twenty to fifty feet is about the average of observations on the Atlantic. The breadth of a wave is calculated as fifteen times its height. Thus, a wave four feet high is sixty feet broad. The inclination of the sides of the waves varies however with the force of the wind, and with the strength of the secondary vibrations in the water, which may interfere with the primary ones. The speed of the waves is only apparent like the motion in a length of cloth shaken up and down. Floating objects do not change their relative positions, but slowly, except in rising and falling with the wave. The real movement of the sea is that of a drifting current, which is slowly formed under the action of the wind, and thisis not rapid, but slow. The astronomer Airey says that every wave 100 feet wide, traversing a sea 164 fathoms in average depth, has a velocity of nearly 2,100 feet a second, or about fifteen and one-half miles an hour; a wave 674 feet, moving over a sea 1,640 fathoms deep, travels more than 69 feet a second, or nearly fifty miles an hour, and this last calculation may be taken as the average speed of storm waves in great seas. As, therefore, we can calculate the velocity of waves from their width and the known depth of the sea, we can calculate the depth of the sea from the known size and velocity of the waves. By this method the depth of the Pacific between Japan and California has been calculated from the size and speed of an earthquake wave, which was set in motion by an eruption in Japan. The accuracy of the calculation was afterward established by actual soundings.It was formerly supposed that the disturbance of the waves did not penetrate the depth of the water, below four or six fathoms, but this has been found, on further observation, erroneous. Sand and mud have been brought up from a depth of a hundred fathoms below the surface, and experiments have shown that waves have a vertical influence 350 times their height. Thus a wave a foot high influences the bottom at a depth of 50 fathoms, and a billow of the ocean 33 feet high is felt below at a distance of 1 3/43/4 miles. At these great depths the action of the wave is perhaps imaginary, but to this reason we can ascribe the heavy swells which are often so dangerous. A hidden rock, far below the surface, arrests some moving wave and causes an eddy, which, rising to the surface, produces the "ground swells" which suddenly rise in the neighborhood of submarine banks and endanger ships. This cause also explains the tide races, which, coming from the depths of the ocean, advance suddenly upon the beaches, destroying all that opposes them. It is this cause which makes the position of light-houses upon certain reefs so dangerous. The Bell Rock house,on the Scottish coast, stands 112 feet above the rock, and yet it is often covered with the waves and foam, even after the tempest has ceased to rage. Such light-houses are often washed away; as that at Minot's Ledge, on the coast of Massachusetts, has often been. In consequence the modern method of building these structures differs from that formerly in use. The custom was to build them of solid masonry, hoping to make them strong enough to resist the waves. Now they are generally built of iron lattice open work, making the bars as slender as is consistent with the proper strength, so as to offer the least resisting surface to the rushing water. This open frame work is raised up high enough, if possible, to place the house and lantern above the reach of the body of the wave.The force of the water in such positions is prodigious. Stephenson calculated that the sea dashed against the Bell Rock light-house with a force of 17 tons for every square yard. At breakwaters in exposed situations the sea has been known to seize blocks of stone weighing tons, and hurl them as a child would pebbles. At Cherbourg, in France, the heaviest cannon have been displaced; and at Barra Head, in the Hebrides, Stephenson states that a block of stone weighing 43 tons was driven by the breakers about two yards. At Plymouth, England, a vessel weighing 200 tons was thrown up on the top of the dike, and left there uninjured. At Dunkirk it has been found that from the dash of the breakers the ground trembles for more than a mile from the shore. Results of this kind, to which our attention is specially directed, since they affect man's work, show us what must be the effect produced by the sea, in constantly eating away the shore; altering the coast lines; changing continents, and building them up elsewhere; and suggest how much greater than what we see must have been the effects of the sea upon the land during the countless ages in which it has been at work.The currents in the ocean, which constitute the real motionof its waters, are very important in the study of the influence of the sea upon the land. By these the circulation of the waters of the globe is carried on. The warm water of the equatorial regions seeking the poles, and a counter movement from the poles to the equator, is established. By their means a constant mingling of the waters on the face of the whole earth is maintained, and the wonderful similarity of its different portions, in their composition, appearance, and the substances held in solution, is produced. The chief causes of this grand circulation are found in the heat of the sun and in the rotation of the earth upon its axis. By the evaporation of the waters in the tropics the surface of that portion of the ocean is estimated to be lowered more than fourteen feet yearly. By this means not only is the atmosphere provided with its store of vapor, to be dispensed in rain upon the land, and thus returned again to the sea, but this lowering of the surface of the ocean, in one part, leads to the currents flowing from the others to restore the equilibrium. The same cause leading also to the circulation of the atmosphere, produces the trade winds, which aid in producing the currents in the ocean.Now that by study and observation mankind have arrived at the conception of the form of the earth, at its general features, and can, in idea, grasp it as a whole, the opportunity is prepared for the methodical study of its parts, and their relation to each other; and this is the subject which for the first time in the history of mankind is offered to the physical geographer, with the certainty that none of his observations can be lost, but that they all are important, and can each be referred to its proper place. Another movement of the ocean is the tides. To the ancients, unacquainted with the form of the earth, its position in space, or its relations with the other bodies of the solar system, the tides were naturally inexplicable. It has been possible, only in modern times to attempt their explanation. Kepler first indicated the course to be followed; andDescartes and Newton each gave a theory; the first that of the pressure of the waters; the last, that of the attraction of the sun and moon upon the waters. This last theory is the one generally accepted, since it has been found satisfactory in most respects; yet it still has its opponents. Now, however, that the telegraph has been discovered, and a means thus afforded for instantaneous communication between observers at distant points, it has become possible to organize a simultaneous observation of the tides at various places, and eventually this will be done, so that the theory that the tides are caused by the attraction of the sun and moon will be entirely proved or rejected according as it will be found consistent with the facts observed.In this connection an interesting instance of the different manner in which the ancients regarded natural phenomena, from that in which the moderns regard the same occurrences, is found in the fear the ancients had of the two monsters Scylla and Charybdis, which were the fabled guardians of the Straits of Messina. At present there are no straits in the Mediterranean more frequented than those of Messina. By the soundings which have been made there, these monsters had been effectually destroyed, and the whirlpools are known to be produced by the ebb and flow of the tide, causing a greater flow of water than can be accommodated by the narrow channel. The width of the channel is hardly two miles, and at low tide it has often been crossed on horseback, by swimming. The rising tide tends toward the north, from the Ionian to the Tyrrhenian sea, and the falling tide in the opposite direction. There is a strife between these currents, and on their confines eddies are formed which ships avoid, but there is no danger unless the wind blows strongly against the tide.Besides the influence of the currents and the tides of the ocean in altering the configuration of the land, the sea is the home of innumerable forms of animal life, which are constantly laboring in the same direction. It has been truly said, thata beef bone, thrown overboard by a sailor on a ship, may form the nucleus of a new continent. The entire chalk cliffs of England were formed from the minute shells deposited by the small animals which secreted them. At their death these fell to the bottom, and thus slowly through the ages the deposit was formed. The recent deep sea dredgings have shown the sea, at all depths, is full of animal life; and as the steady fall of snow-flakes in a winter's storm, piled up by currents of wind, form the drifts, or falling quietly, cover the ground uniformly, so the sea is full of the minute shells, which, carried by currents, form banks, or, falling evenly, prepare the plains which in the future will appear, in some upheaval, to form new continents.In the United States the peninsula of Florida is an evidence of the land produced by the labor of the coral polyp. Florida has now ceased to increase toward the east, for on this side it touches the deep waters of the gulf, and the polyps can live only in shallow water. The peninsula increases only on its southern and western coasts. The cut at the end of this chapter represents the appearance of coral islands as they first rise to the surface, before the gathering soil provides the conditions for covering them with the luxuriant vegetation of the tropics.The cut at the head of this chapter, of an aquarium, represents a new appliance of modern times, which is a most valuable aid in our obtaining a knowledge of the habits of the animals living in the sea. In fresh water, as well as in salt, the mutual relations of the vegetable and animal life serve to keep the water from becoming stagnant. The plants secrete the carbonic acid gas, which the animals give to the water by breathing, and in so doing free the oxygen which the animals require. In keeping therefore an aquarium, the desired point is to provide such a natural proportion of vegetable and animal life as shall preserve this balance. In many of the largermuseums of Europe, large aquariums have been built, and an opportunity thus afforded for the study of the various animal forms, the habits of the vegetable growths, and their relations. Some of these structures are so arranged that they surround a room which receives its light only through the water in the aquaria, and thus the spectator, without disturbing the fish, can watch them feeding and performing all their actions.From this arrangement of the aquaria, as the light passes from the water to the eye, the spectator is not disturbed in his vision, as he is by trying to look into the water from above, by the refraction of the light. A great deal that has been learned in modern times concerning the growth of the vegetation of the sea, of the habits of the animals, of their manner of life, their food and their growth, has been obtained from the chance of observation afforded by the various aquaria. Beside the positive benefits which have thus resulted from the public aquaria, those in smaller form afford for the lover of natural history a new and interesting way of carrying on his studies. In this way also the habits of observation are formed in the young, and it is fair to believe that the spirit of inquiry thus excited will tend to increase the knowledge of the phenomena of life, and its relations to the conditions of existence.It has been by this course that the race itself has risen from barbarism to its present degree of civilization, and with the new appliances of modern times, it is evidently impossible to limit the probabilities of advance in the future.A few facts about the extent of our commerce will show the difference of the spirit with which the ocean is regarded in modern times, compared with that prevailing in antiquity; and the different use we have learned to make of it, from the time when the exchanges of the world were confined to a few coasters, who hardly ventured out of the sight of land. To give even the most condensed summary of the world's commerce to-day would require a series of volumes; but afew figures taken from our own will enable the reader to judge of that which is now going on all over the world, uniting the most distantly separated nations; enabling them to become acquainted with each other; and impressing them with the fact that by industry alone are the material comforts of life to be attained, and that the task before humanity is to become acquainted with the products of the world, with the forces of which it is the theatre, and learn to control them for our own benefit.From the report of the Bureau of Statistics, for a portion of 1873, we learn that the imports and exports of the United States during eight months, ending with February, 1873, amounted to the following totals: Imported in American vessels, $104,891,248; imported in foreign vessels, $317,043,490; imported in land vehicles, $12,356,325. During the same period the domestic exports in American vessels amounted to a total of $108,246,698; in foreign vessels, $311,816,048; and in land vehicles, $5,282,949. At the same time the re-exportation of foreign products amounted in American vessels to $5,147,805; in foreign vessels to $10,938,300; and in land vehicles to $1,693,795.The number and tonnage of American and foreign vessels engaged in the foreign trade, which entered and cleared during the twelve months ending with February, 1873, was as follows: American vessels, 10,928, carrying 3,597,474 tons; foreign vessels, 19,220, carrying 7,622,416 tons. The report of the Bureau for 1872, gives the following totals of the number of vessels and their tonnage engaged in the commerce of the United States. Upon the Atlantic and Gulf coasts, 21,940 vessels carrying 2,916,001,058 tons. On the Western rivers, 1,476 vessels carrying 354,938,052 tons. On the Northern lakes 5,339 vessels, carrying 726,105,051 tons. On the Pacific coast, 1,094 vessels carrying 161,987,050.From the port of New York alone there are now thirteenlines of steamships plying to Europe. Of these the Anchor line has 15 steamers, with a tonnage of 36,127 tons; the Baltic Lloyds has 4 vessels of 9,200 tons; the Cardiff (a Welsh) line has three vessels of 8,000 tons; the Cunard has 23 vessels of 59,308 tons; the Holland (direct) line has two vessels of 4,000 tons; the General Transatlantic (a French line) has 5 vessels of 17,000 tons; the Hamburg has 15 vessels of 45,000 tons; the Inman line has 12 vessels of 34,811; the Liverpool and Great Western line has 7 vessels of 23,573 tons; the North German line has 20 vessels of 60,000 tons; the National line has 12 vessels of 50,062 tons; the State line has 3 vessels of 7,500 tons; and the White Star line has 6 vessels of 23,064 tons. Beside these ships, the thirteen companies are building from 30 to 40 more steamers to meet the demand for freight.The ocean has thus become almost a steam ferry; almost every day a steamer leaves for Europe. With this knowledge of how far we have progressed in becoming acquainted with the ocean, it will be well to consider for a moment how much still remains for us to explore. In the middle ages, and even down to modern times, the maps of the world represented all unknown lands as inhabited by monsters; but every voyage made by discoverers has contracted the limits of these fables, until they have finally about disappeared. Still at the North Pole and in the Antarctic regions areas extending over a space of 2,900,000 and 8,700,000 square miles, respectively, have been, up to this time, unvisited. The icebergs and mountains of ice have kept them from our accurate investigations. The difficulties of such a sea are well shown in the adjoining illustration.Discoveries have also to be made in the interiors of Africa, Asia, South America and Australia before the civilized portions of the race can claim a complete knowledge of the earth, their common dwelling-place. Every year, however, the portionsunexplored grow smaller and smaller, so that we are justified in believing that eventually the whole world will be known to us, from actual observation.APPEARANCE OF ICE.LIGHT SHIP AND INCOMING VESSEL.Another difference which our extended knowledge of the world has produced is this: The mariner now approaching an unknown coast does not fear to meet monsters, but looks out for the light-house, the light-ships, the buoys, and other evidences of civilization, by which the dangers of the coast are pointed out to the voyager. As a contrast with some of the pictures already given, representing the approach to the land of the early explorers, the illustration of the light-ship will show how differently to-day a voyage approaches its termination. Instead of looking out for enemies, and preparing weapons for use, a package of newspapers and letters is got ready, and the news boat, which lies ready at hand, is prompt to seize them, and hasten with these to spread the news of another safe arrival. It is thus that science, which is gradually preparing the means for converting the globe into one great organism for the benefit of mankind, points out the way for making it the abode of that harmony, peace and plenty which has been dreamed of by the poets of all time. For this it is only necessary that our moral progress should keep pace with our advance in knowledge. The globe will never become the abode of perfect harmony until men are united in a universal league of justice and peace. And in aiding toward the production of this most desirable consummation, what has been here written will show how important has been the part taken by the ocean.A CORAL ISLAND.

CHAPTER LVIITHE DEVELOPMENT OF SHIP BUILDING—NEW MODELS FOR SHIPS—STEAM SHIP NAVIGATION—MONITORS—IRON-PLATED FRIGATES—TIN CLADS—RAMS—TORPEDO BOATS—THEIR USE IN THE CONFEDERACY—LIFE RAFTS—YACHT BUILDING—OCEAN YACHT RACE—THE COST OF A YACHT.From the oars, which were the only means of propulsion used in the galleys of antiquity, to the sails of a subsequent period, by which only favoring winds could be made use of, the advance was great, but not as great as the discovery of steam, by which in modern times the sea is traversed with but little regard for the condition of the wind. To suit the different means used for the propulsion of these vessels, modifications have been made in the manner of their construction, in their form, and with sailing ships in the arrangement of sails. When, with the successful termination of the war of the Revolution, the United States first took its place in the world as an independent nation, the commercial activity which was the natural result of the greater political freedom resulting from the issue of that contest, found its expression first in our commerce; and the self-reliance, which is the inevitable result of liberty; the spirit of inquiry fostered by a departure from old methods, and the abandonment of old traditions, were displayed in the construction, the rig and the general air of the vessels then built, as much as in the construction of the political organization of the new republic.So much was this the case that American vessels became known the world over for their trim and neat appearance. The blunt, rounded prows and heavy sterns of the English orDutch vessels were replaced by American models, sharp, nothing superfluous, and riding the waters as easy as a bird. The American clipper ships became renowned for their quick passages, and in transporting teas from China made fortunes for their happy owners, by bringing to the markets the first cargoes of the new crops.The same thing occurred when steam-vessels first began to cross the ocean. The English in their first steamers followed the models of their largest sailing ships. They still preserved the heavy bowsprit, projecting twenty to thirty feet in advance of the prow, though it was not necessary, as in their sailing ships, for balancing the pressure of the other sails. Their steamers were therefore always heavy at the head, and when, in a rough sea, they were driven by the power of the engine, buried their bows in every large wave. Any one who has crossed the Atlantic in an English steamer of twenty years ago, must have noticed how heavily it labored in rough weather, and how the waves broke over her bow. To take in tons of salt water when the waves ran high, was usual; and in a passage across the Atlantic it was no rare thing to have the salt encrusted on the smoke-stack, from the waves which dashed over the bow and swept aft, reach a thickness of from one to two inches.PENNSYLVANIA AND OHIO ON THE STOCKS.The American ship-builder, however, early saw that the model of his craft, which was to be propelled by steam, should differ from that of a ship depending upon its sails alone, and governed himself accordingly. He made her sharp, for speed, and ended her prow straight up and down, as he built the steamboats for river navigation. The consequence was that she rode dry through waves which would pour tons of salt water upon the deck of an English model. George Steers, of New York, a genius in naval architecture, and whose early death was deeply regretted, was the person who did the most to bring into use the present form used in the best models for ocean steamers. One of his first steamers, the Adriatic, built for the Collins line, excited great attention in Liverpool, when she first appeared there. The LondonTimesspoke of her in leading articles, calling upon the English ship-builders to contrast her with ships of their own construction. It spoke of how she glided up the Mersey, making hardly a ripple from her bows, so evenly and quietly she parted the water, while an English steamer of her size so disturbed the stream as to bring up the mud from the bottom. TheTimeswas also specially struck with the ease with which she was handled, turning almost in her length, while for an English steamer turning was an operation requiring so much more space, andmaking so much more disturbance in the water. From that time to this the English have followed the American models in the construction and equipment of their steamers, and their example has been imitated by most other nations.The latest specimens of American ship building are shown in the cut representing the Pennsylvania and Ohio on the stocks. These vessels are the pioneers of the new line between Philadelphia and Liverpool.Nor is this the only change which naval architecture has undergone. The material for ship-building, especially for sea going steamers, has in modern times come to be chiefly iron. Livingstone, in his book of travels in Africa, tells how, when he was putting together on the banks of one of the rivers there the pieces of a small iron steamer which had been sent out to him from England, the natives gathered round, and inspecting the work going on, jeered at him for thinking that a boat built of such a material would float. Their whole experience with iron was that it would sink. When, however, the steamer was completed and launched, they could hardly express their astonishment at finding that she floated.Though every school-boy, from his text-books on natural philosophy, can explain the reasons why a ship built of iron will float, yet our ancestors would have considered, a proposition to construct a ship from this material very much as the native Africans did. Even in the construction of wooden ships, iron enters now much more than it did formerly. The knees, or bent oak beams, by which the form of the ship was made, have become so scarce and dear that they are now frequently made of iron. It takes so long for an oak tree to grow, and the demand was so great for limbs of such a natural bend as could be used for ship-building, that even before the use of iron for such portions of a ship, the process was in frequent use of bending the beams, or knees, by steaming then and then subjecting them to great pressure.Iron as a material for ships has some very great and material advantages. It is on the whole lighter, so that an iron ship weighs less, absolutely, than a wooden one of the same size. Then as the knees and other timbers take up less space when made of iron, than when made of wood, and as the thickness of the sides is much less, more space is secured in an iron ship than in a wooden one for carrying the cargo. Besides this, a vessel built of iron can be divided into water-tight compartments, so that an accidental leak will damage only that portion of the cargo contained in that compartment in which it occurs.This method of construction is also another factor of safety in case of accident by collision or in any other way. One compartment may be injured so as to fill with water, while the others, being uninjured, their buoyancy will still keep the ship afloat. An objection, however, to the use of compartments lies in the fact that, as they must be riveted to the sides, the rows of holes for the rivets necessarily weaken the strength of the sides, so that a ship with compartments, which touches on a rock or other obstacle, at one end, is more apt to break apart than one without compartments, as the sides, unsupported by the buoyancy of the water, have the less strength to support her weight in the length. Still, all things considered, iron has come so much in favor for the construction of large ships, that it is in much more general use for that purpose than wood.In the construction of an iron ship, the naval architect draws his plans, and sends his construction drawings to the iron rolling mill, where each plate is made of the exact curve and dimensions. The holes for the rivets are punched by machinery, and the plates are then ready to be put together. The hull of the vessel is made of iron bars riveted together, and the plates are riveted to the iron upright ribs, each plate overlapping the preceding. The ribs are placed from ten to eighteen inches apart, and the whole structure is of iron. The simplicity of the construction of an iron ship is such, that when the plates are ready, it can be put together with wonderful rapidity.MONITORS.PLANS OF THE MONITOR.ST. LOUIS.For constructing ships of war, iron is almost wholly used, and the experience of our late war has almost entirely changed the methods and theories of naval warfare. The enormous frigate, carrying a heavy armament of numerous guns, and manned by a thousand men, has been replaced by a small craft—so low in the water as to project above it only a few inches, carrying but a single gun, or at most only two, which are of very heavy calibre, and are mounted in a revolving tower in the middle of the craft. The general description of the Monitor, that it was a cheese-box on a raft, aptly describes their appearance.By the introduction of the monitor as a war vessel, a complete change was wrought in naval warfare. The large hulk of the old ships afforded only a better target for the heavy guns of this new craft, while its own slight projection above the water, and the fact that its engines and propeller were covered by the water, afforded it almost absolute security from the enemy's guns. Even if it was struck, the round shape of its iron clad deck, and its revolving tower caused the balls to glance off without affecting much injury. In October, 1861, forty-five days from the laying of her keel, the St. Louis was launched, being the first iron-clad ship owned by the United States. Other vessels of similar design were rapidly brought to completion, and these iron-clad river boats began their task of opening the navigation of the Mississippi. The St. Louis was built in the city of the same name, by Mr. James B. Eads, of that city.DOUBLE ENDER.The cuts represent the shape of some of the iron-clads built for service in the western rivers, where the shallowness of the stream made it necessary that the craft should not draw too much water.For the same reasons the "tin-clads," as they were called from the thinness of the plates with which they were covered, were built. The "double-enders" were also thus constructed, in order to navigate, as necessary, either way, in the narrow and crooked streams, where our navy performed such admirable work during the War.The use of heavy artillery in naval warfare has also caused great modifications to be made in the construction of other naval ships than the monitors. To avoid the injury caused by heavy artillery, the idea was suggested of plating them with iron. The most extensive experiments of this kind were made in England, but not with the most gratifying success. It was found that the iron plating rendered the ships too heavy, if it was made thick enough to be of effective service. In a rough sea the vessels rolled so heavily as to be nearly unmanageable, while the weight of the plating on the sides acted with a leverage to tear the ships in halves, so that they were considered almost unsafe. One of them, also, on her trial trip, having capsized and sunk with her entire crew, public confidence in them as serviceable vessels was entirely lost; and the advantage of iron-plating large ships of war may be still considered as an open question.MINNEHAHA, OR TIN-CLAD.It has also been suggested that ships of war should be furnished with a sharp beak of steel, and with such powerful engines as should secure for them great speed, and, without trusting at all to the use of their guns, should be used as rams to run into and crush their adversaries. This suggestion, which is practically returning to the practice of the ancients before the invention of either gunpowder or steam, has never yet, however, been carried out in fact. So far, therefore, the most serviceable modern ships of war are the monitors. The largest and most expensive of these, the Dunderberg, was not finished until after the war was over, and was sold, with the consent of the government, by her builder, to Russia for $1,000,000, and crossed the Atlantic safely, a feat which showed her to be sea-worthy, and more worthy of confidence than any of the armored vessels built by the English Government.In modern times attention has also been given to constructing vessels which should be navigated under the water. Fulton, whose name is so inseparably connected with the introduction of the steamboat, made an attempt, the first on record, in the harbor of Brest, on the west coast of France, in 1801, under the order of Napoleon I., to blow up an English ship with a torpedo, a weapon of warfare which is said to have been first suggested by Franklin, who experimented with them in the Revolution. Fulton used, in this attempt, a submarine boat of his own invention, the model and construction of which have never been made public. His attempt being unsuccessful the project was abandoned, as Napoleon withdrew his support from the scheme.THE RAM IRONSIDES.During our late civil war, while the harbor of Charleston, South Carolina, was blockaded by the ships of the national navy, and the bombardment of Fort Sumter continued, attempts were made by the besieged to destroy the blockading ships by torpedoes, which were to be fastened by a submarine craft. One of these boats, called a "cigar boat," though both ends were pointed, is thus described: She was thirty feet long and six feet broad, painted a lead color. Her propelling power consisted of a six-horse engine, geared to a shaft turning a propeller. At her bow was an iron bowsprit, so arranged that it could be lowered to the required depth, and at the end of this the torpedo was secured. When afloat only about fifteen feet of her length projected some fourteen inches above the water. For fuel she used anthracite coal, and attained a speed of about six miles an hour. Her tonnage was about seven or eight tons, and in this craft Lieutenant Glassells, of Virginia, volunteered to attack the iron-clad, the Ironsides, which was the most powerful ship at that time afloat in the navy, rated at from three to four thousand tons. The Ironsides was a very heavily armed ship, provided with eleven-inch guns, and capable of delivering the heaviest broadside ever fired from a single ship. On the night of the sixth of October, 1863, Lieutenant Glassells set out on his expedition from one of the wharves of Charleston. The sky was covered with clouds, and the night was very dark. His crew consisted of a fireman and a pilot, and his offensive armament of a torpedo, in position, and a double-barreled fowling-piece. Being asked why he carried a gun on such an expedition, he answered: "You know I have served in the United States navy, and I shall not attack my old comrades like an assassin. I shall hail and fire into them, with this, then let the torpedo do its work like an open and declared foe." This speech is a fair specimen of the singular mixture of honor and disloyalty which characterized the whole secession movement. This lieutenant could desert his navy, could take up arms against his country, but could not attack one of its ships without first giving its crew warning.TORPEDO EXPLOSION.The "cigar boat" steamed silently on its course until within about fifty yards of the Ironsides, without being discovered. Everything on the immense ship seemed as quiet as the grave. Suddenly, in the still night, the lieutenant cries, "Ship ahoy!" "Where away?" is the answer. "We have come to attack you," cries the lieutenant, at the same time firing his fowling-piece, checking the engine, and directing the torpedo. It struck, but before the "cigar boat" could retire, with a gurgling roar it exploded. The explosion sounded like the discharge of a submerged gun. Water mixed with flame was forced by the explosion far up above the gunwales of the ship, and bearing up the bows of the smaller craft, poured back intorrents through the chimney, put out the fires, and rendered the "cigar boat" helpless.For a moment everything on board the Ironsides was in confusion; but the discipline of the navy was equal to the emergency. The drums beat to quarters, the guns were manned, and the marines poured a steady fire upon the little craft, now floating helplessly on the sea. Lieutenant Glassells jumped into the water, to escape death from the shower of balls; the pilot followed him, but the fireman remained at his post, as the boat drifted away from danger. Glassells then called for help; the marines ceased firing, and a small boat from the Ironsides rescued him from the water. The pilot swam back to the "cigar boat" and he and the fireman bailed her out, rekindled the fire, and escaped to Charleston. Glassells was afterwards sent North, and under confinement his health broke down. The Ironsides was sufficiently injured by the explosion to be sent from her station for repairs. Had the torpedo struck her further below, it is thought to be probable that she would have been sunk.Another torpedo boat was also built in Charleston, upon a different model. This was called the "fish boat." It was built of boiler-iron, was thirty feet long by five feet eight inches deep, and about four and a half feet wide, amidships. Its middle section was an ellipse flattening to a wedge shape at both ends, which were alike. It was intended to rise or sink in the water, like a fish, and in order to do this its specific gravity had to be kept equal that of water. In navigating under water the boat had also to be kept upon an even keel. On her bowsprit, which projected ten feet, the torpedo was secured, and in order to balance the hundred and fifty pounds this weighed, an equal amount of ballast was stowed at the stern. Ten feet from her bow she had two iron fins, one on each side, about four feet long, seven inches wide and three-eighths of an inch thick. These fins were fastened to an inchrod of iron passing through water-tight fittings in her sides, and provided with a crank inside, so that the fins could be worked in any direction, or at any angle, forcing the craft to the surface, or below, or forward or backward. By working them also in opposite directions the vessel could be turned as a row-boat is by pulling with one oar and backing water with the other. At the stern, midway between the top and bottom, she was provided with a propeller, worked by a shaft, fitted water-tight, and propelled by hand-power inside the hold. On her deck were two round hatches, or man holes, about ten feet apart, and fitted with plates of such thick glass as is used in side-walks, for cellar lights, set in iron frames, working upon hinges, fastened on the inside, and fitting water-tight when closed. Between these hatches were two flexible air pipes, with air-tight valves, so that when within a foot of the surface, by opening the valves, fresh air could be drawn into the hold. The crew depended upon the violent action of their hats, when the valves were open, for making a current sufficient to displace the foul air, and bring in a supply of fresh.When the boat was finished, in the first experiment made with her, she carried a crew of eight men, and a shifting ballast of iron plates. She moved from the wharf, passed down the river, just showing the tops of the hatches, dove under a ship lying in the stream, rose on the other side, and returned to the wharf. This was done successfully a second time, when the chief of the crew left her for some purpose, and the rest of the men, though unaccustomed to the work, undertook to perform the experiment alone. She moved out, dove down, but never came up. About a fortnight afterward she was found, raised, the dead removed, and the whole inside disinfected, cleaned and painted white. On the second trial she filled just as the crew had manned her, and sunk. The captain and one other saved themselves, but the rest of the crew, consisting of five, were drowned in her. Another crew volunteered to man her, andon the night of the 17th of February, 1864, she set out from Sullivan's Island, to which place she had run from her anchorage, to attack the blockading fleet, carrying a torpedo affixed to her bowsprit.During the whole night the bombardment of the city was kept up, and nothing was heard of the fish boat. The next morning a heavy fog hung over the coast, clearing up about eight in the morning, and the sloop-of-war Housatonic was discovered to be sunk in about six fathoms of water, her crew swarming in her rigging for safety. The fish boat had destroyed her, and destroyed herself in doing so. This was the first time that she had ever been used in exploding a torpedo, and the cause of her destruction is supposed to have been as follows: The weight of the torpedo, on her bowsprit, was balanced by the shifting ballast in her stern, and thus she was kept on an even keel. As soon, however, as the torpedo struck and exploded, the balance was destroyed, her bows were lifted by the weight in the stern, control was lost of her, and the Housatonic, sinking from the damage done her by the explosion, settled upon the "fish boat" and carried her and her crew to the bottom.Disastrous as these attempts at submarine navigation were, yet they are the most successful yet made. We have seen else where that men have, for other purposes than war, been able to descend under the surface of the sea, and stay there quite a time without injury; but their appliances are not vessels intended for navigation.Let us turn, then, from this record of how human ingenuity has been taxed to devise means to destroy men, to the consideration of the new devices made for their comfort or safety in crossing the sea. One of the most useful of these is a life raft or bolsa, one of which is represented in our cut. This consists of three elastic cylinders, made of india-rubber cloth, each twenty-five feet long. When empty they are easily packedin a very small compass. For use they are blown up, and fastened to a prepared staging. The cut represents one which crossed the Atlantic in 1867, arriving at Southampton July 25, having started from New York forty-three days before. She was rigged with two masts secured to the staging, and her crew consisted of three men, John Wilkes, George Miller and Jerry Mallene. A bellows to fill the cylinders, should they require it, was an important item in her cargo. The crew kept alternate watch, sleeping, by turns, in a tent spread on the staging. Their supply of water they carried in casks. The experiment of crossing the Atlantic was made to show the safety of a raft thus constructed.LIFE RAFT.For attaining speed, and thus diminishing the tedium and the risk of an Atlantic voyage, Mr. Wynans, of Baltimore, has invented a cigar-shaped boat, as it is called, though it is pointed at both ends. Various causes have hitherto prevented his final experiment with his boat, but he hopes to be able tomake with it an average speed of at least eighteen miles an hour.Crossing the Atlantic has become so common, and sea-sickness making the trip so disagreeable and dangerous to many people, attention has been turned to inventing a method of construction which shall destroy the cause for this malady, by keeping the saloon always on a level, notwithstanding the pitching and rolling of the ship in a high sea. Mr. Bessemer, the inventor of the new process for making steel, has invented a boat, which he is now constructing, and which he thinks will make it perfectly feasible to cross the Atlantic without the necessity of paying the usual tribute to old Neptune. The general idea of his ship may be thus described: The saloon for passengers is to be balanced upon a frame work similar in principle to that by which the lamps on ship-board are supported. An outer circle swings upon pivots at each end of its diameter, and within another circle supports the lamp, which is swung upon pivots at right angles with those in the first. However, then, the ship may pitch or roll, the lamp remains perpendicular, the circles adjusting themselves to meet the motion of the ship. This idea is to be applied in the construction of the saloon, so that it will remain constantly on a level, and as Mr. Bessemer has a plenty of money to construct a dozen of ships for an experiment, the public may expect before long to hear of a trial. The first ship of the kind is reported as on the stocks, and to be rapidly approaching completion. Nor is this the only style of ship suggested to obviate sea-sickness. A Russian, M. Alexandroiski, proposes a new form of stationary ship-saloon, which differs from that of Mr. Bessemer in having the cabin float in kind of a tank placed between the engines, instead of being hung on pivots. This invention, it is stated, has been tested by the Russian Naval Department, and is reported to have been found entirely satisfactory, the rolling motion of the vessel being completelycounteracted. With the success of one or the other of these plans, an ocean voyage, even in a rough sea, will become a pleasure trip, like sailing in a painted ship upon a painted ocean; the wildness of a storm even may become merely an exciting spectacle, like looking at the representation of a hurricane in a theatre, with the further advantage of having it real and life-like.Perhaps the change which has been brought about in our feeling with regard to the ocean is shown more in the yachting of modern times than in anything else. The idea of making a trip across the Atlantic is no longer considered an almost foolhardy undertaking, but even our yachts have made it a field for their races, and a match across the Atlantic has become not an unusual thing. The owning of yachts has become so general among our rich men, that yacht-building has become a regular branch of naval architecture, and constant improvements are being made in their models, and greater luxury displayed in their fitting up. George Steers, who has been mentioned before for his improvements in the model of the steamship, made his first reputation by the construction of the yacht America, which was sent over to England, and proved the fastest vessel in the regatta on the occasion of the first World's Fair in London. This yacht, after her victory, was bought by an Englishman, and never used again, being left to rot at her moorings. However, she changed the yacht models of Europe.OCEAN YACHT RACE.—THE HENRIETTA, VISTA AND FLEETWING.A yacht race across the Atlantic was one of the sensations of the year 1866. Three yachts entered the contest, the Henrietta, the Fleetwing and the Vista. They started from Sandy Hook one day in December, and though the season had been unusually stormy, and they encountered gales almost all the way, so that frequently they were forced to sail under bare poles, and the Fleetwing lost several of her sailors, who were washed overboard, yet they arrived safe at Cowes on the same day, after a fourteen days' voyage, the Henrietta winning the race by a couple of hours. This yacht was the property of James Gordon Bennett, Jr., the son of the owner of the New York Herald. During the war her owner freely offered her to the government, and she has done good service. After the victory Mr. Bennett sold her for $15,000, and purchased the Fleetwing for $65,000, re-christening her the Dauntless. This yacht, in another ocean race in 1870, was beaten by the Cambria, an English yacht. These prices show the cost of seeking one's pleasure in a yacht, and yet it is only one item of the expense. To keep one of the vessels costs more than the expenses of the majority of the households in the country. A crew of five men is needed, and it is a question whether, all things considered, more real substantial interest and enjoyment is not taken by a lover of the sea and of sailing in an ordinary sail-boat, which he and a friend or two are amply competent to man and manage, than is taken by the owners of the most luxuriantly furnished yachts in the world. As pleasure ships, however, the yacht is all that can be desired. Many of them contain spacious saloons; their cabins are almost always paneled in costly woods, and most luxuriantly furnished, and even gas has been provided for them. It is estimated that the yachts of the New York club alone have cost more than $2,000,000, and those of the whole country about $5,000,000. Much of this is the mere luxury of ostentation; but as the real pleasures there are in thus visiting distant lands come to be better appreciated, much of this foolish expenditure will be abandoned.

THE DEVELOPMENT OF SHIP BUILDING—NEW MODELS FOR SHIPS—STEAM SHIP NAVIGATION—MONITORS—IRON-PLATED FRIGATES—TIN CLADS—RAMS—TORPEDO BOATS—THEIR USE IN THE CONFEDERACY—LIFE RAFTS—YACHT BUILDING—OCEAN YACHT RACE—THE COST OF A YACHT.

From the oars, which were the only means of propulsion used in the galleys of antiquity, to the sails of a subsequent period, by which only favoring winds could be made use of, the advance was great, but not as great as the discovery of steam, by which in modern times the sea is traversed with but little regard for the condition of the wind. To suit the different means used for the propulsion of these vessels, modifications have been made in the manner of their construction, in their form, and with sailing ships in the arrangement of sails. When, with the successful termination of the war of the Revolution, the United States first took its place in the world as an independent nation, the commercial activity which was the natural result of the greater political freedom resulting from the issue of that contest, found its expression first in our commerce; and the self-reliance, which is the inevitable result of liberty; the spirit of inquiry fostered by a departure from old methods, and the abandonment of old traditions, were displayed in the construction, the rig and the general air of the vessels then built, as much as in the construction of the political organization of the new republic.

So much was this the case that American vessels became known the world over for their trim and neat appearance. The blunt, rounded prows and heavy sterns of the English orDutch vessels were replaced by American models, sharp, nothing superfluous, and riding the waters as easy as a bird. The American clipper ships became renowned for their quick passages, and in transporting teas from China made fortunes for their happy owners, by bringing to the markets the first cargoes of the new crops.

The same thing occurred when steam-vessels first began to cross the ocean. The English in their first steamers followed the models of their largest sailing ships. They still preserved the heavy bowsprit, projecting twenty to thirty feet in advance of the prow, though it was not necessary, as in their sailing ships, for balancing the pressure of the other sails. Their steamers were therefore always heavy at the head, and when, in a rough sea, they were driven by the power of the engine, buried their bows in every large wave. Any one who has crossed the Atlantic in an English steamer of twenty years ago, must have noticed how heavily it labored in rough weather, and how the waves broke over her bow. To take in tons of salt water when the waves ran high, was usual; and in a passage across the Atlantic it was no rare thing to have the salt encrusted on the smoke-stack, from the waves which dashed over the bow and swept aft, reach a thickness of from one to two inches.

PENNSYLVANIA AND OHIO ON THE STOCKS.

PENNSYLVANIA AND OHIO ON THE STOCKS.

PENNSYLVANIA AND OHIO ON THE STOCKS.

The American ship-builder, however, early saw that the model of his craft, which was to be propelled by steam, should differ from that of a ship depending upon its sails alone, and governed himself accordingly. He made her sharp, for speed, and ended her prow straight up and down, as he built the steamboats for river navigation. The consequence was that she rode dry through waves which would pour tons of salt water upon the deck of an English model. George Steers, of New York, a genius in naval architecture, and whose early death was deeply regretted, was the person who did the most to bring into use the present form used in the best models for ocean steamers. One of his first steamers, the Adriatic, built for the Collins line, excited great attention in Liverpool, when she first appeared there. The LondonTimesspoke of her in leading articles, calling upon the English ship-builders to contrast her with ships of their own construction. It spoke of how she glided up the Mersey, making hardly a ripple from her bows, so evenly and quietly she parted the water, while an English steamer of her size so disturbed the stream as to bring up the mud from the bottom. TheTimeswas also specially struck with the ease with which she was handled, turning almost in her length, while for an English steamer turning was an operation requiring so much more space, andmaking so much more disturbance in the water. From that time to this the English have followed the American models in the construction and equipment of their steamers, and their example has been imitated by most other nations.

The latest specimens of American ship building are shown in the cut representing the Pennsylvania and Ohio on the stocks. These vessels are the pioneers of the new line between Philadelphia and Liverpool.

Nor is this the only change which naval architecture has undergone. The material for ship-building, especially for sea going steamers, has in modern times come to be chiefly iron. Livingstone, in his book of travels in Africa, tells how, when he was putting together on the banks of one of the rivers there the pieces of a small iron steamer which had been sent out to him from England, the natives gathered round, and inspecting the work going on, jeered at him for thinking that a boat built of such a material would float. Their whole experience with iron was that it would sink. When, however, the steamer was completed and launched, they could hardly express their astonishment at finding that she floated.

Though every school-boy, from his text-books on natural philosophy, can explain the reasons why a ship built of iron will float, yet our ancestors would have considered, a proposition to construct a ship from this material very much as the native Africans did. Even in the construction of wooden ships, iron enters now much more than it did formerly. The knees, or bent oak beams, by which the form of the ship was made, have become so scarce and dear that they are now frequently made of iron. It takes so long for an oak tree to grow, and the demand was so great for limbs of such a natural bend as could be used for ship-building, that even before the use of iron for such portions of a ship, the process was in frequent use of bending the beams, or knees, by steaming then and then subjecting them to great pressure.

Iron as a material for ships has some very great and material advantages. It is on the whole lighter, so that an iron ship weighs less, absolutely, than a wooden one of the same size. Then as the knees and other timbers take up less space when made of iron, than when made of wood, and as the thickness of the sides is much less, more space is secured in an iron ship than in a wooden one for carrying the cargo. Besides this, a vessel built of iron can be divided into water-tight compartments, so that an accidental leak will damage only that portion of the cargo contained in that compartment in which it occurs.

This method of construction is also another factor of safety in case of accident by collision or in any other way. One compartment may be injured so as to fill with water, while the others, being uninjured, their buoyancy will still keep the ship afloat. An objection, however, to the use of compartments lies in the fact that, as they must be riveted to the sides, the rows of holes for the rivets necessarily weaken the strength of the sides, so that a ship with compartments, which touches on a rock or other obstacle, at one end, is more apt to break apart than one without compartments, as the sides, unsupported by the buoyancy of the water, have the less strength to support her weight in the length. Still, all things considered, iron has come so much in favor for the construction of large ships, that it is in much more general use for that purpose than wood.

In the construction of an iron ship, the naval architect draws his plans, and sends his construction drawings to the iron rolling mill, where each plate is made of the exact curve and dimensions. The holes for the rivets are punched by machinery, and the plates are then ready to be put together. The hull of the vessel is made of iron bars riveted together, and the plates are riveted to the iron upright ribs, each plate overlapping the preceding. The ribs are placed from ten to eighteen inches apart, and the whole structure is of iron. The simplicity of the construction of an iron ship is such, that when the plates are ready, it can be put together with wonderful rapidity.

MONITORS.

MONITORS.

MONITORS.

PLANS OF THE MONITOR.

PLANS OF THE MONITOR.

PLANS OF THE MONITOR.

ST. LOUIS.

ST. LOUIS.

ST. LOUIS.

For constructing ships of war, iron is almost wholly used, and the experience of our late war has almost entirely changed the methods and theories of naval warfare. The enormous frigate, carrying a heavy armament of numerous guns, and manned by a thousand men, has been replaced by a small craft—so low in the water as to project above it only a few inches, carrying but a single gun, or at most only two, which are of very heavy calibre, and are mounted in a revolving tower in the middle of the craft. The general description of the Monitor, that it was a cheese-box on a raft, aptly describes their appearance.

By the introduction of the monitor as a war vessel, a complete change was wrought in naval warfare. The large hulk of the old ships afforded only a better target for the heavy guns of this new craft, while its own slight projection above the water, and the fact that its engines and propeller were covered by the water, afforded it almost absolute security from the enemy's guns. Even if it was struck, the round shape of its iron clad deck, and its revolving tower caused the balls to glance off without affecting much injury. In October, 1861, forty-five days from the laying of her keel, the St. Louis was launched, being the first iron-clad ship owned by the United States. Other vessels of similar design were rapidly brought to completion, and these iron-clad river boats began their task of opening the navigation of the Mississippi. The St. Louis was built in the city of the same name, by Mr. James B. Eads, of that city.

DOUBLE ENDER.

DOUBLE ENDER.

DOUBLE ENDER.

The cuts represent the shape of some of the iron-clads built for service in the western rivers, where the shallowness of the stream made it necessary that the craft should not draw too much water.

For the same reasons the "tin-clads," as they were called from the thinness of the plates with which they were covered, were built. The "double-enders" were also thus constructed, in order to navigate, as necessary, either way, in the narrow and crooked streams, where our navy performed such admirable work during the War.

The use of heavy artillery in naval warfare has also caused great modifications to be made in the construction of other naval ships than the monitors. To avoid the injury caused by heavy artillery, the idea was suggested of plating them with iron. The most extensive experiments of this kind were made in England, but not with the most gratifying success. It was found that the iron plating rendered the ships too heavy, if it was made thick enough to be of effective service. In a rough sea the vessels rolled so heavily as to be nearly unmanageable, while the weight of the plating on the sides acted with a leverage to tear the ships in halves, so that they were considered almost unsafe. One of them, also, on her trial trip, having capsized and sunk with her entire crew, public confidence in them as serviceable vessels was entirely lost; and the advantage of iron-plating large ships of war may be still considered as an open question.

MINNEHAHA, OR TIN-CLAD.

MINNEHAHA, OR TIN-CLAD.

MINNEHAHA, OR TIN-CLAD.

It has also been suggested that ships of war should be furnished with a sharp beak of steel, and with such powerful engines as should secure for them great speed, and, without trusting at all to the use of their guns, should be used as rams to run into and crush their adversaries. This suggestion, which is practically returning to the practice of the ancients before the invention of either gunpowder or steam, has never yet, however, been carried out in fact. So far, therefore, the most serviceable modern ships of war are the monitors. The largest and most expensive of these, the Dunderberg, was not finished until after the war was over, and was sold, with the consent of the government, by her builder, to Russia for $1,000,000, and crossed the Atlantic safely, a feat which showed her to be sea-worthy, and more worthy of confidence than any of the armored vessels built by the English Government.

In modern times attention has also been given to constructing vessels which should be navigated under the water. Fulton, whose name is so inseparably connected with the introduction of the steamboat, made an attempt, the first on record, in the harbor of Brest, on the west coast of France, in 1801, under the order of Napoleon I., to blow up an English ship with a torpedo, a weapon of warfare which is said to have been first suggested by Franklin, who experimented with them in the Revolution. Fulton used, in this attempt, a submarine boat of his own invention, the model and construction of which have never been made public. His attempt being unsuccessful the project was abandoned, as Napoleon withdrew his support from the scheme.

THE RAM IRONSIDES.

THE RAM IRONSIDES.

THE RAM IRONSIDES.

During our late civil war, while the harbor of Charleston, South Carolina, was blockaded by the ships of the national navy, and the bombardment of Fort Sumter continued, attempts were made by the besieged to destroy the blockading ships by torpedoes, which were to be fastened by a submarine craft. One of these boats, called a "cigar boat," though both ends were pointed, is thus described: She was thirty feet long and six feet broad, painted a lead color. Her propelling power consisted of a six-horse engine, geared to a shaft turning a propeller. At her bow was an iron bowsprit, so arranged that it could be lowered to the required depth, and at the end of this the torpedo was secured. When afloat only about fifteen feet of her length projected some fourteen inches above the water. For fuel she used anthracite coal, and attained a speed of about six miles an hour. Her tonnage was about seven or eight tons, and in this craft Lieutenant Glassells, of Virginia, volunteered to attack the iron-clad, the Ironsides, which was the most powerful ship at that time afloat in the navy, rated at from three to four thousand tons. The Ironsides was a very heavily armed ship, provided with eleven-inch guns, and capable of delivering the heaviest broadside ever fired from a single ship. On the night of the sixth of October, 1863, Lieutenant Glassells set out on his expedition from one of the wharves of Charleston. The sky was covered with clouds, and the night was very dark. His crew consisted of a fireman and a pilot, and his offensive armament of a torpedo, in position, and a double-barreled fowling-piece. Being asked why he carried a gun on such an expedition, he answered: "You know I have served in the United States navy, and I shall not attack my old comrades like an assassin. I shall hail and fire into them, with this, then let the torpedo do its work like an open and declared foe." This speech is a fair specimen of the singular mixture of honor and disloyalty which characterized the whole secession movement. This lieutenant could desert his navy, could take up arms against his country, but could not attack one of its ships without first giving its crew warning.

TORPEDO EXPLOSION.

TORPEDO EXPLOSION.

TORPEDO EXPLOSION.

The "cigar boat" steamed silently on its course until within about fifty yards of the Ironsides, without being discovered. Everything on the immense ship seemed as quiet as the grave. Suddenly, in the still night, the lieutenant cries, "Ship ahoy!" "Where away?" is the answer. "We have come to attack you," cries the lieutenant, at the same time firing his fowling-piece, checking the engine, and directing the torpedo. It struck, but before the "cigar boat" could retire, with a gurgling roar it exploded. The explosion sounded like the discharge of a submerged gun. Water mixed with flame was forced by the explosion far up above the gunwales of the ship, and bearing up the bows of the smaller craft, poured back intorrents through the chimney, put out the fires, and rendered the "cigar boat" helpless.

For a moment everything on board the Ironsides was in confusion; but the discipline of the navy was equal to the emergency. The drums beat to quarters, the guns were manned, and the marines poured a steady fire upon the little craft, now floating helplessly on the sea. Lieutenant Glassells jumped into the water, to escape death from the shower of balls; the pilot followed him, but the fireman remained at his post, as the boat drifted away from danger. Glassells then called for help; the marines ceased firing, and a small boat from the Ironsides rescued him from the water. The pilot swam back to the "cigar boat" and he and the fireman bailed her out, rekindled the fire, and escaped to Charleston. Glassells was afterwards sent North, and under confinement his health broke down. The Ironsides was sufficiently injured by the explosion to be sent from her station for repairs. Had the torpedo struck her further below, it is thought to be probable that she would have been sunk.

Another torpedo boat was also built in Charleston, upon a different model. This was called the "fish boat." It was built of boiler-iron, was thirty feet long by five feet eight inches deep, and about four and a half feet wide, amidships. Its middle section was an ellipse flattening to a wedge shape at both ends, which were alike. It was intended to rise or sink in the water, like a fish, and in order to do this its specific gravity had to be kept equal that of water. In navigating under water the boat had also to be kept upon an even keel. On her bowsprit, which projected ten feet, the torpedo was secured, and in order to balance the hundred and fifty pounds this weighed, an equal amount of ballast was stowed at the stern. Ten feet from her bow she had two iron fins, one on each side, about four feet long, seven inches wide and three-eighths of an inch thick. These fins were fastened to an inchrod of iron passing through water-tight fittings in her sides, and provided with a crank inside, so that the fins could be worked in any direction, or at any angle, forcing the craft to the surface, or below, or forward or backward. By working them also in opposite directions the vessel could be turned as a row-boat is by pulling with one oar and backing water with the other. At the stern, midway between the top and bottom, she was provided with a propeller, worked by a shaft, fitted water-tight, and propelled by hand-power inside the hold. On her deck were two round hatches, or man holes, about ten feet apart, and fitted with plates of such thick glass as is used in side-walks, for cellar lights, set in iron frames, working upon hinges, fastened on the inside, and fitting water-tight when closed. Between these hatches were two flexible air pipes, with air-tight valves, so that when within a foot of the surface, by opening the valves, fresh air could be drawn into the hold. The crew depended upon the violent action of their hats, when the valves were open, for making a current sufficient to displace the foul air, and bring in a supply of fresh.

When the boat was finished, in the first experiment made with her, she carried a crew of eight men, and a shifting ballast of iron plates. She moved from the wharf, passed down the river, just showing the tops of the hatches, dove under a ship lying in the stream, rose on the other side, and returned to the wharf. This was done successfully a second time, when the chief of the crew left her for some purpose, and the rest of the men, though unaccustomed to the work, undertook to perform the experiment alone. She moved out, dove down, but never came up. About a fortnight afterward she was found, raised, the dead removed, and the whole inside disinfected, cleaned and painted white. On the second trial she filled just as the crew had manned her, and sunk. The captain and one other saved themselves, but the rest of the crew, consisting of five, were drowned in her. Another crew volunteered to man her, andon the night of the 17th of February, 1864, she set out from Sullivan's Island, to which place she had run from her anchorage, to attack the blockading fleet, carrying a torpedo affixed to her bowsprit.

During the whole night the bombardment of the city was kept up, and nothing was heard of the fish boat. The next morning a heavy fog hung over the coast, clearing up about eight in the morning, and the sloop-of-war Housatonic was discovered to be sunk in about six fathoms of water, her crew swarming in her rigging for safety. The fish boat had destroyed her, and destroyed herself in doing so. This was the first time that she had ever been used in exploding a torpedo, and the cause of her destruction is supposed to have been as follows: The weight of the torpedo, on her bowsprit, was balanced by the shifting ballast in her stern, and thus she was kept on an even keel. As soon, however, as the torpedo struck and exploded, the balance was destroyed, her bows were lifted by the weight in the stern, control was lost of her, and the Housatonic, sinking from the damage done her by the explosion, settled upon the "fish boat" and carried her and her crew to the bottom.

Disastrous as these attempts at submarine navigation were, yet they are the most successful yet made. We have seen else where that men have, for other purposes than war, been able to descend under the surface of the sea, and stay there quite a time without injury; but their appliances are not vessels intended for navigation.

Let us turn, then, from this record of how human ingenuity has been taxed to devise means to destroy men, to the consideration of the new devices made for their comfort or safety in crossing the sea. One of the most useful of these is a life raft or bolsa, one of which is represented in our cut. This consists of three elastic cylinders, made of india-rubber cloth, each twenty-five feet long. When empty they are easily packedin a very small compass. For use they are blown up, and fastened to a prepared staging. The cut represents one which crossed the Atlantic in 1867, arriving at Southampton July 25, having started from New York forty-three days before. She was rigged with two masts secured to the staging, and her crew consisted of three men, John Wilkes, George Miller and Jerry Mallene. A bellows to fill the cylinders, should they require it, was an important item in her cargo. The crew kept alternate watch, sleeping, by turns, in a tent spread on the staging. Their supply of water they carried in casks. The experiment of crossing the Atlantic was made to show the safety of a raft thus constructed.

LIFE RAFT.

LIFE RAFT.

LIFE RAFT.

For attaining speed, and thus diminishing the tedium and the risk of an Atlantic voyage, Mr. Wynans, of Baltimore, has invented a cigar-shaped boat, as it is called, though it is pointed at both ends. Various causes have hitherto prevented his final experiment with his boat, but he hopes to be able tomake with it an average speed of at least eighteen miles an hour.

Crossing the Atlantic has become so common, and sea-sickness making the trip so disagreeable and dangerous to many people, attention has been turned to inventing a method of construction which shall destroy the cause for this malady, by keeping the saloon always on a level, notwithstanding the pitching and rolling of the ship in a high sea. Mr. Bessemer, the inventor of the new process for making steel, has invented a boat, which he is now constructing, and which he thinks will make it perfectly feasible to cross the Atlantic without the necessity of paying the usual tribute to old Neptune. The general idea of his ship may be thus described: The saloon for passengers is to be balanced upon a frame work similar in principle to that by which the lamps on ship-board are supported. An outer circle swings upon pivots at each end of its diameter, and within another circle supports the lamp, which is swung upon pivots at right angles with those in the first. However, then, the ship may pitch or roll, the lamp remains perpendicular, the circles adjusting themselves to meet the motion of the ship. This idea is to be applied in the construction of the saloon, so that it will remain constantly on a level, and as Mr. Bessemer has a plenty of money to construct a dozen of ships for an experiment, the public may expect before long to hear of a trial. The first ship of the kind is reported as on the stocks, and to be rapidly approaching completion. Nor is this the only style of ship suggested to obviate sea-sickness. A Russian, M. Alexandroiski, proposes a new form of stationary ship-saloon, which differs from that of Mr. Bessemer in having the cabin float in kind of a tank placed between the engines, instead of being hung on pivots. This invention, it is stated, has been tested by the Russian Naval Department, and is reported to have been found entirely satisfactory, the rolling motion of the vessel being completelycounteracted. With the success of one or the other of these plans, an ocean voyage, even in a rough sea, will become a pleasure trip, like sailing in a painted ship upon a painted ocean; the wildness of a storm even may become merely an exciting spectacle, like looking at the representation of a hurricane in a theatre, with the further advantage of having it real and life-like.

Perhaps the change which has been brought about in our feeling with regard to the ocean is shown more in the yachting of modern times than in anything else. The idea of making a trip across the Atlantic is no longer considered an almost foolhardy undertaking, but even our yachts have made it a field for their races, and a match across the Atlantic has become not an unusual thing. The owning of yachts has become so general among our rich men, that yacht-building has become a regular branch of naval architecture, and constant improvements are being made in their models, and greater luxury displayed in their fitting up. George Steers, who has been mentioned before for his improvements in the model of the steamship, made his first reputation by the construction of the yacht America, which was sent over to England, and proved the fastest vessel in the regatta on the occasion of the first World's Fair in London. This yacht, after her victory, was bought by an Englishman, and never used again, being left to rot at her moorings. However, she changed the yacht models of Europe.

OCEAN YACHT RACE.—THE HENRIETTA, VISTA AND FLEETWING.

OCEAN YACHT RACE.—THE HENRIETTA, VISTA AND FLEETWING.

OCEAN YACHT RACE.—THE HENRIETTA, VISTA AND FLEETWING.

A yacht race across the Atlantic was one of the sensations of the year 1866. Three yachts entered the contest, the Henrietta, the Fleetwing and the Vista. They started from Sandy Hook one day in December, and though the season had been unusually stormy, and they encountered gales almost all the way, so that frequently they were forced to sail under bare poles, and the Fleetwing lost several of her sailors, who were washed overboard, yet they arrived safe at Cowes on the same day, after a fourteen days' voyage, the Henrietta winning the race by a couple of hours. This yacht was the property of James Gordon Bennett, Jr., the son of the owner of the New York Herald. During the war her owner freely offered her to the government, and she has done good service. After the victory Mr. Bennett sold her for $15,000, and purchased the Fleetwing for $65,000, re-christening her the Dauntless. This yacht, in another ocean race in 1870, was beaten by the Cambria, an English yacht. These prices show the cost of seeking one's pleasure in a yacht, and yet it is only one item of the expense. To keep one of the vessels costs more than the expenses of the majority of the households in the country. A crew of five men is needed, and it is a question whether, all things considered, more real substantial interest and enjoyment is not taken by a lover of the sea and of sailing in an ordinary sail-boat, which he and a friend or two are amply competent to man and manage, than is taken by the owners of the most luxuriantly furnished yachts in the world. As pleasure ships, however, the yacht is all that can be desired. Many of them contain spacious saloons; their cabins are almost always paneled in costly woods, and most luxuriantly furnished, and even gas has been provided for them. It is estimated that the yachts of the New York club alone have cost more than $2,000,000, and those of the whole country about $5,000,000. Much of this is the mere luxury of ostentation; but as the real pleasures there are in thus visiting distant lands come to be better appreciated, much of this foolish expenditure will be abandoned.

CHAPTER LVIII.OUR KNOWLEDGE OF THE EARTH AND SEA—HOW IT HAS INCREASED—THE EARTH THE DAUGHTER OF THE OCEAN—THE OPINION OF SCIENCE—THE MEAN DEPTH OF THE OCEAN—THE EXTENT OF THE OCEAN—ITS VOLUME—SPECIFIC GRAVITY OF SEA-WATER—CONSTITUTION OF SALT-WATER—THE SILVER IN THE SEA—THE WAVES OF THE SEA—THE CURRENTS OF THE OCEAN—THE TIDES—THE AQUARIUM—THE COMMERCE OF MODERN TIMES—THE SPREAD OF PEACE.In the preceding pages the facts have been given in a comprehensive though succinct form, which enable us to see how, step by step, each one of which became possible only when those preceding had been taken. Mankind has gained a knowledge of the outlines of the sea; of the form of the earth itself; of the relative positions occupied by the water and the land; of their action upon each other, and thus the way has been prepared by the enterprise of preceding generations for the scientific methods of study which characterize the modern era. The adventurous voyagers of the early times, who, daring as they were, hardly were bold enough to venture in their open boats, propelled only by oars, out of the sight of land, could not be expected to conceive that it could be possible for men, like themselves, to ever become able to construct ships such as modern nations construct, in which, propelled by steam, voyages should be taken across oceans, and out of sight of land, their course over the trackless waters be guided with accuracy and certainty, to any desired point, by the compass and the observations of the motions of the stars.By experiment and observation the entire aspect and conception of the ocean has been changed in modern times from that which prevailed in antiquity, or even more recently, until within the few past generations. Though much has been done, in the study of the ocean, toward obtaining a proper conception of its influence in the general economy of the globe, yet thereis still much to be learned. Among the ancients it was generally declared in their cosmogonies that the solid portions of the world were produced by the ocean. "Water is the chief of all," says Pindar; "the earth is the daughter of ocean," is the mythological statement common to the primitive nations. Though this poetical expression was merely based upon a vague tradition, and can hardly be taken as the result of any methodical study of the earth, yet modern science tends to show that it is really true. The ocean has produced the solid land. The study of geology, the skilled inspection of the various strata of the land—the rocks, sand, clay, chalk, conglomerates—proves that the materials of the continents have been chiefly deposited at the bottom of the sea, and raised to their present position by the chemical or mechanical agencies which are constantly at work in the vast laboratory of nature.Many rocks, as for instance the granites of Scandinavia, which were previously believed to have been projected in a molten and plastic state from the interior of the earth, where they had been subjected to the action of the intense heat supposed to exist in the centre of the earth, are now supposed to be in reality ancient sedimentary strata, slowly deposited by the sea, and upheaved by the contraction of the crust, or by some other force of upheaval acting from the centre. Upon the sides of mountains, or on their summits, now thousands of feet above the level of the ocean, unquestionable traces of the action of the sea can be found. And the scientific observer of to-day sees all about him evidences that the immense work of the creation of continents, commenced by the sea in the earliest periods of time, is to-day continuing without relaxation or intermission, and with such energy that even during the short course of a single life great changes can be seen to have been produced. Here and there a coast, subject to the beating of the serf, is seen to be slowly undermined, disintegrated, worn down and carried away, while in another place the material is depositedby the sea, and sandy beaches or promontories are built up. New rocks also, differing in appearance and constitution from those worn away, are formed. But beside this action of the sea upon the coasts, in constantly changing the configuration of the land, modern observation has shown us that animal life is an agent constantly at work within the sea itself, in the formation of new lands. The innumerable minute forms of life with which the sea swarms; the coral polyps, the shells, the sponges, and the animalculæ of all kinds, are constantly engaged in consuming the food they find, in reproducing themselves, and in dying. From the various matters brought down to the ocean by the rivers of the land, they secrete their shells or other coverings; and as generation after generation they die, these falling to the bottom form immense banks, or plains, which some future action of upheaval will bring above the surface to form the material for new continents or islands.Thus while the ocean prepares the materials for the future continents in its bosom, it also furnishes the waters which wash away the lands already existing. To the thought of modern science the granite peaks, the snow-clad mountains, immovable and eternal as they seem, are constantly disintegrating, and partake, with every thing else in creation, the eternal round of change which is constantly going on. From the sea, by evaporation, rise the vapors which, condensing against the sides of the mountains, form the glaciers; and these, slowly sliding down toward the plains, are such efficient agents in wearing away the mountains, grinding up their solid rocks and preparing the gravel which the mountain streams distribute over the plains. From the sea the atmosphere receives the moisture destined to return in rain from the clouds; to feed the brooks whose union forms the rivers, destined again to return to the sea the waters it provided, and thus keep up, in a single, mighty and endless circulation, the waters of the globe.Thus to the agency of the ocean we are indebted for our rivers, which have played such an important part in the geological history of the earth, in the distribution of the flora and fauna of various countries, and on the life of man himself. In the study also of the climates of the earth, and their effects upon life, we find the ocean bears a most important part. As the circulation of the atmosphere mingles the heated air from the equator with that of the frozen regions of the poles, so the currents of the ocean circulate about the earth, blending the contrasts of climate, and making a harmonious whole of all the different portions. Thus, instead of considering the ocean as the barren waste of desolation it appeared to the ancients, to the modern thinker the ocean has, layer by layer, deposited the land from its bosom, and now by its vapors provides the rains which support its vegetable life, upon which all other life depends, and creates the rivers and the springs, which play such an important part in the modification of the interior of continents, at the greatest distance from the sea.The mean depth of the whole mass of the ocean waters of the globe is estimated at about three miles, since measurements have shown that the basins of the Atlantic and Northern Pacific are deeper than this by hundreds of thousands of fathoms. The extent covered by the surface of the ocean has been estimated at more than 145,000,000 of square miles, and with this estimate, the sea is calculated to form a volume of about two and one-half million billions of cubic yards, or about the five hundred and sixtieth part of the planet itself. The highest point of the land raised above the level of the sea is much less elevated than the bottom of the sea is depressed from the same level, so that the mass of the land above this level can be estimated only at about a fortieth part of the mass of the waters.The specific gravity of sea water is greater than that offresh. This comes from the various matters which it holds in solution. This difference varies with different seas; with the quantity of matters held in solution; with the amount of evaporation; the size and number of rivers flowing into the various seas; the ice melting into them; the currents, and various other causes. The average quantity of salts held in solution in sea water is estimated at 34.40 parts in 1,000, and this average is the same in all seas. The quantity of common salt held in solution is always a little more than three-quarters (75.786) of the total mineral matter held in solution. The salt of the sea averages, if the water is evaporated, about two inches to every fathom; so that, were the ocean dried up, a layer of salt about two hundred and thirty feet thick would remain on the bottom, or the whole salt of the sea would measure more than a thousand millions of cubic miles. This vast quantity of salt in the sea explains how the enormous beds of rock salt were formed, when the lands now exposed were covered by the waters.Beside the oxygen and hydrogen which constitute its waters, the sea contains chlorine, nitrogen, carbon, bromine, iodine, fluorine, sulphur, phosphorus, silicon, sodium, potassium, boron, aluminium, magnesium, calcium, strontium, barium. From the various sea-weeds most of these substances can be obtained. Copper, lead, zinc, cobalt, nickel and manganese have also been found in their ashes. Iron has also been obtained from sea water, and a trace of silver also is often deposited by the magnetic current established between the sheeting of ships and the salt water. Though only a trace is thus found, yet it has been estimated that the whole waters of the ocean contain in solution two million tons of silver. In the boilers of ocean steamships, which use sea water, arsenic has also been found.Sea water also retains dissolved air better than fresh water, and the bulk of this in ocean water is generally greater by athird than that found in river water. It varies from a fifth to a thirtieth, and gradually increases from the surface to a depth of about three hundred and twenty-five to three hundred and eighty fathoms. The uniformity in the constitution of the waters of the sea is chiefly caused by the action of the waves, which finally mix and mingle the waters into a homogeneous mass. The waves of the sea are caused chiefly by the action of the wind, and the effect continues even after the wind has ceased. One of the grandest spectacles at sea is offered by the regular movement of the waves in perfectly calm weather, when not a breath of air stirs the sails. During to the Autumnal calm under the Tropic of Cancer, these waves appear with astonishing regularity at intervals of two hundred to three hundred yards, sweep under the ship, and as far as the eye can reach, are seen advancing and passing away, as regularly as the furrows in a field. Such waves are caused by the regularity of the trade winds. The height of the waves is not the same in all seas. It is greater where the basin is deeper in proportion to the surface, and also as the water is fresher and yields easier to the impulses of the wind.The height of waves has been variously measured. Some observers have claimed to see them over one hundred feet high, but from twenty to fifty feet is about the average of observations on the Atlantic. The breadth of a wave is calculated as fifteen times its height. Thus, a wave four feet high is sixty feet broad. The inclination of the sides of the waves varies however with the force of the wind, and with the strength of the secondary vibrations in the water, which may interfere with the primary ones. The speed of the waves is only apparent like the motion in a length of cloth shaken up and down. Floating objects do not change their relative positions, but slowly, except in rising and falling with the wave. The real movement of the sea is that of a drifting current, which is slowly formed under the action of the wind, and thisis not rapid, but slow. The astronomer Airey says that every wave 100 feet wide, traversing a sea 164 fathoms in average depth, has a velocity of nearly 2,100 feet a second, or about fifteen and one-half miles an hour; a wave 674 feet, moving over a sea 1,640 fathoms deep, travels more than 69 feet a second, or nearly fifty miles an hour, and this last calculation may be taken as the average speed of storm waves in great seas. As, therefore, we can calculate the velocity of waves from their width and the known depth of the sea, we can calculate the depth of the sea from the known size and velocity of the waves. By this method the depth of the Pacific between Japan and California has been calculated from the size and speed of an earthquake wave, which was set in motion by an eruption in Japan. The accuracy of the calculation was afterward established by actual soundings.It was formerly supposed that the disturbance of the waves did not penetrate the depth of the water, below four or six fathoms, but this has been found, on further observation, erroneous. Sand and mud have been brought up from a depth of a hundred fathoms below the surface, and experiments have shown that waves have a vertical influence 350 times their height. Thus a wave a foot high influences the bottom at a depth of 50 fathoms, and a billow of the ocean 33 feet high is felt below at a distance of 1 3/43/4 miles. At these great depths the action of the wave is perhaps imaginary, but to this reason we can ascribe the heavy swells which are often so dangerous. A hidden rock, far below the surface, arrests some moving wave and causes an eddy, which, rising to the surface, produces the "ground swells" which suddenly rise in the neighborhood of submarine banks and endanger ships. This cause also explains the tide races, which, coming from the depths of the ocean, advance suddenly upon the beaches, destroying all that opposes them. It is this cause which makes the position of light-houses upon certain reefs so dangerous. The Bell Rock house,on the Scottish coast, stands 112 feet above the rock, and yet it is often covered with the waves and foam, even after the tempest has ceased to rage. Such light-houses are often washed away; as that at Minot's Ledge, on the coast of Massachusetts, has often been. In consequence the modern method of building these structures differs from that formerly in use. The custom was to build them of solid masonry, hoping to make them strong enough to resist the waves. Now they are generally built of iron lattice open work, making the bars as slender as is consistent with the proper strength, so as to offer the least resisting surface to the rushing water. This open frame work is raised up high enough, if possible, to place the house and lantern above the reach of the body of the wave.The force of the water in such positions is prodigious. Stephenson calculated that the sea dashed against the Bell Rock light-house with a force of 17 tons for every square yard. At breakwaters in exposed situations the sea has been known to seize blocks of stone weighing tons, and hurl them as a child would pebbles. At Cherbourg, in France, the heaviest cannon have been displaced; and at Barra Head, in the Hebrides, Stephenson states that a block of stone weighing 43 tons was driven by the breakers about two yards. At Plymouth, England, a vessel weighing 200 tons was thrown up on the top of the dike, and left there uninjured. At Dunkirk it has been found that from the dash of the breakers the ground trembles for more than a mile from the shore. Results of this kind, to which our attention is specially directed, since they affect man's work, show us what must be the effect produced by the sea, in constantly eating away the shore; altering the coast lines; changing continents, and building them up elsewhere; and suggest how much greater than what we see must have been the effects of the sea upon the land during the countless ages in which it has been at work.The currents in the ocean, which constitute the real motionof its waters, are very important in the study of the influence of the sea upon the land. By these the circulation of the waters of the globe is carried on. The warm water of the equatorial regions seeking the poles, and a counter movement from the poles to the equator, is established. By their means a constant mingling of the waters on the face of the whole earth is maintained, and the wonderful similarity of its different portions, in their composition, appearance, and the substances held in solution, is produced. The chief causes of this grand circulation are found in the heat of the sun and in the rotation of the earth upon its axis. By the evaporation of the waters in the tropics the surface of that portion of the ocean is estimated to be lowered more than fourteen feet yearly. By this means not only is the atmosphere provided with its store of vapor, to be dispensed in rain upon the land, and thus returned again to the sea, but this lowering of the surface of the ocean, in one part, leads to the currents flowing from the others to restore the equilibrium. The same cause leading also to the circulation of the atmosphere, produces the trade winds, which aid in producing the currents in the ocean.Now that by study and observation mankind have arrived at the conception of the form of the earth, at its general features, and can, in idea, grasp it as a whole, the opportunity is prepared for the methodical study of its parts, and their relation to each other; and this is the subject which for the first time in the history of mankind is offered to the physical geographer, with the certainty that none of his observations can be lost, but that they all are important, and can each be referred to its proper place. Another movement of the ocean is the tides. To the ancients, unacquainted with the form of the earth, its position in space, or its relations with the other bodies of the solar system, the tides were naturally inexplicable. It has been possible, only in modern times to attempt their explanation. Kepler first indicated the course to be followed; andDescartes and Newton each gave a theory; the first that of the pressure of the waters; the last, that of the attraction of the sun and moon upon the waters. This last theory is the one generally accepted, since it has been found satisfactory in most respects; yet it still has its opponents. Now, however, that the telegraph has been discovered, and a means thus afforded for instantaneous communication between observers at distant points, it has become possible to organize a simultaneous observation of the tides at various places, and eventually this will be done, so that the theory that the tides are caused by the attraction of the sun and moon will be entirely proved or rejected according as it will be found consistent with the facts observed.In this connection an interesting instance of the different manner in which the ancients regarded natural phenomena, from that in which the moderns regard the same occurrences, is found in the fear the ancients had of the two monsters Scylla and Charybdis, which were the fabled guardians of the Straits of Messina. At present there are no straits in the Mediterranean more frequented than those of Messina. By the soundings which have been made there, these monsters had been effectually destroyed, and the whirlpools are known to be produced by the ebb and flow of the tide, causing a greater flow of water than can be accommodated by the narrow channel. The width of the channel is hardly two miles, and at low tide it has often been crossed on horseback, by swimming. The rising tide tends toward the north, from the Ionian to the Tyrrhenian sea, and the falling tide in the opposite direction. There is a strife between these currents, and on their confines eddies are formed which ships avoid, but there is no danger unless the wind blows strongly against the tide.Besides the influence of the currents and the tides of the ocean in altering the configuration of the land, the sea is the home of innumerable forms of animal life, which are constantly laboring in the same direction. It has been truly said, thata beef bone, thrown overboard by a sailor on a ship, may form the nucleus of a new continent. The entire chalk cliffs of England were formed from the minute shells deposited by the small animals which secreted them. At their death these fell to the bottom, and thus slowly through the ages the deposit was formed. The recent deep sea dredgings have shown the sea, at all depths, is full of animal life; and as the steady fall of snow-flakes in a winter's storm, piled up by currents of wind, form the drifts, or falling quietly, cover the ground uniformly, so the sea is full of the minute shells, which, carried by currents, form banks, or, falling evenly, prepare the plains which in the future will appear, in some upheaval, to form new continents.In the United States the peninsula of Florida is an evidence of the land produced by the labor of the coral polyp. Florida has now ceased to increase toward the east, for on this side it touches the deep waters of the gulf, and the polyps can live only in shallow water. The peninsula increases only on its southern and western coasts. The cut at the end of this chapter represents the appearance of coral islands as they first rise to the surface, before the gathering soil provides the conditions for covering them with the luxuriant vegetation of the tropics.The cut at the head of this chapter, of an aquarium, represents a new appliance of modern times, which is a most valuable aid in our obtaining a knowledge of the habits of the animals living in the sea. In fresh water, as well as in salt, the mutual relations of the vegetable and animal life serve to keep the water from becoming stagnant. The plants secrete the carbonic acid gas, which the animals give to the water by breathing, and in so doing free the oxygen which the animals require. In keeping therefore an aquarium, the desired point is to provide such a natural proportion of vegetable and animal life as shall preserve this balance. In many of the largermuseums of Europe, large aquariums have been built, and an opportunity thus afforded for the study of the various animal forms, the habits of the vegetable growths, and their relations. Some of these structures are so arranged that they surround a room which receives its light only through the water in the aquaria, and thus the spectator, without disturbing the fish, can watch them feeding and performing all their actions.From this arrangement of the aquaria, as the light passes from the water to the eye, the spectator is not disturbed in his vision, as he is by trying to look into the water from above, by the refraction of the light. A great deal that has been learned in modern times concerning the growth of the vegetation of the sea, of the habits of the animals, of their manner of life, their food and their growth, has been obtained from the chance of observation afforded by the various aquaria. Beside the positive benefits which have thus resulted from the public aquaria, those in smaller form afford for the lover of natural history a new and interesting way of carrying on his studies. In this way also the habits of observation are formed in the young, and it is fair to believe that the spirit of inquiry thus excited will tend to increase the knowledge of the phenomena of life, and its relations to the conditions of existence.It has been by this course that the race itself has risen from barbarism to its present degree of civilization, and with the new appliances of modern times, it is evidently impossible to limit the probabilities of advance in the future.A few facts about the extent of our commerce will show the difference of the spirit with which the ocean is regarded in modern times, compared with that prevailing in antiquity; and the different use we have learned to make of it, from the time when the exchanges of the world were confined to a few coasters, who hardly ventured out of the sight of land. To give even the most condensed summary of the world's commerce to-day would require a series of volumes; but afew figures taken from our own will enable the reader to judge of that which is now going on all over the world, uniting the most distantly separated nations; enabling them to become acquainted with each other; and impressing them with the fact that by industry alone are the material comforts of life to be attained, and that the task before humanity is to become acquainted with the products of the world, with the forces of which it is the theatre, and learn to control them for our own benefit.From the report of the Bureau of Statistics, for a portion of 1873, we learn that the imports and exports of the United States during eight months, ending with February, 1873, amounted to the following totals: Imported in American vessels, $104,891,248; imported in foreign vessels, $317,043,490; imported in land vehicles, $12,356,325. During the same period the domestic exports in American vessels amounted to a total of $108,246,698; in foreign vessels, $311,816,048; and in land vehicles, $5,282,949. At the same time the re-exportation of foreign products amounted in American vessels to $5,147,805; in foreign vessels to $10,938,300; and in land vehicles to $1,693,795.The number and tonnage of American and foreign vessels engaged in the foreign trade, which entered and cleared during the twelve months ending with February, 1873, was as follows: American vessels, 10,928, carrying 3,597,474 tons; foreign vessels, 19,220, carrying 7,622,416 tons. The report of the Bureau for 1872, gives the following totals of the number of vessels and their tonnage engaged in the commerce of the United States. Upon the Atlantic and Gulf coasts, 21,940 vessels carrying 2,916,001,058 tons. On the Western rivers, 1,476 vessels carrying 354,938,052 tons. On the Northern lakes 5,339 vessels, carrying 726,105,051 tons. On the Pacific coast, 1,094 vessels carrying 161,987,050.From the port of New York alone there are now thirteenlines of steamships plying to Europe. Of these the Anchor line has 15 steamers, with a tonnage of 36,127 tons; the Baltic Lloyds has 4 vessels of 9,200 tons; the Cardiff (a Welsh) line has three vessels of 8,000 tons; the Cunard has 23 vessels of 59,308 tons; the Holland (direct) line has two vessels of 4,000 tons; the General Transatlantic (a French line) has 5 vessels of 17,000 tons; the Hamburg has 15 vessels of 45,000 tons; the Inman line has 12 vessels of 34,811; the Liverpool and Great Western line has 7 vessels of 23,573 tons; the North German line has 20 vessels of 60,000 tons; the National line has 12 vessels of 50,062 tons; the State line has 3 vessels of 7,500 tons; and the White Star line has 6 vessels of 23,064 tons. Beside these ships, the thirteen companies are building from 30 to 40 more steamers to meet the demand for freight.The ocean has thus become almost a steam ferry; almost every day a steamer leaves for Europe. With this knowledge of how far we have progressed in becoming acquainted with the ocean, it will be well to consider for a moment how much still remains for us to explore. In the middle ages, and even down to modern times, the maps of the world represented all unknown lands as inhabited by monsters; but every voyage made by discoverers has contracted the limits of these fables, until they have finally about disappeared. Still at the North Pole and in the Antarctic regions areas extending over a space of 2,900,000 and 8,700,000 square miles, respectively, have been, up to this time, unvisited. The icebergs and mountains of ice have kept them from our accurate investigations. The difficulties of such a sea are well shown in the adjoining illustration.Discoveries have also to be made in the interiors of Africa, Asia, South America and Australia before the civilized portions of the race can claim a complete knowledge of the earth, their common dwelling-place. Every year, however, the portionsunexplored grow smaller and smaller, so that we are justified in believing that eventually the whole world will be known to us, from actual observation.APPEARANCE OF ICE.LIGHT SHIP AND INCOMING VESSEL.Another difference which our extended knowledge of the world has produced is this: The mariner now approaching an unknown coast does not fear to meet monsters, but looks out for the light-house, the light-ships, the buoys, and other evidences of civilization, by which the dangers of the coast are pointed out to the voyager. As a contrast with some of the pictures already given, representing the approach to the land of the early explorers, the illustration of the light-ship will show how differently to-day a voyage approaches its termination. Instead of looking out for enemies, and preparing weapons for use, a package of newspapers and letters is got ready, and the news boat, which lies ready at hand, is prompt to seize them, and hasten with these to spread the news of another safe arrival. It is thus that science, which is gradually preparing the means for converting the globe into one great organism for the benefit of mankind, points out the way for making it the abode of that harmony, peace and plenty which has been dreamed of by the poets of all time. For this it is only necessary that our moral progress should keep pace with our advance in knowledge. The globe will never become the abode of perfect harmony until men are united in a universal league of justice and peace. And in aiding toward the production of this most desirable consummation, what has been here written will show how important has been the part taken by the ocean.A CORAL ISLAND.

OUR KNOWLEDGE OF THE EARTH AND SEA—HOW IT HAS INCREASED—THE EARTH THE DAUGHTER OF THE OCEAN—THE OPINION OF SCIENCE—THE MEAN DEPTH OF THE OCEAN—THE EXTENT OF THE OCEAN—ITS VOLUME—SPECIFIC GRAVITY OF SEA-WATER—CONSTITUTION OF SALT-WATER—THE SILVER IN THE SEA—THE WAVES OF THE SEA—THE CURRENTS OF THE OCEAN—THE TIDES—THE AQUARIUM—THE COMMERCE OF MODERN TIMES—THE SPREAD OF PEACE.

In the preceding pages the facts have been given in a comprehensive though succinct form, which enable us to see how, step by step, each one of which became possible only when those preceding had been taken. Mankind has gained a knowledge of the outlines of the sea; of the form of the earth itself; of the relative positions occupied by the water and the land; of their action upon each other, and thus the way has been prepared by the enterprise of preceding generations for the scientific methods of study which characterize the modern era. The adventurous voyagers of the early times, who, daring as they were, hardly were bold enough to venture in their open boats, propelled only by oars, out of the sight of land, could not be expected to conceive that it could be possible for men, like themselves, to ever become able to construct ships such as modern nations construct, in which, propelled by steam, voyages should be taken across oceans, and out of sight of land, their course over the trackless waters be guided with accuracy and certainty, to any desired point, by the compass and the observations of the motions of the stars.

By experiment and observation the entire aspect and conception of the ocean has been changed in modern times from that which prevailed in antiquity, or even more recently, until within the few past generations. Though much has been done, in the study of the ocean, toward obtaining a proper conception of its influence in the general economy of the globe, yet thereis still much to be learned. Among the ancients it was generally declared in their cosmogonies that the solid portions of the world were produced by the ocean. "Water is the chief of all," says Pindar; "the earth is the daughter of ocean," is the mythological statement common to the primitive nations. Though this poetical expression was merely based upon a vague tradition, and can hardly be taken as the result of any methodical study of the earth, yet modern science tends to show that it is really true. The ocean has produced the solid land. The study of geology, the skilled inspection of the various strata of the land—the rocks, sand, clay, chalk, conglomerates—proves that the materials of the continents have been chiefly deposited at the bottom of the sea, and raised to their present position by the chemical or mechanical agencies which are constantly at work in the vast laboratory of nature.

Many rocks, as for instance the granites of Scandinavia, which were previously believed to have been projected in a molten and plastic state from the interior of the earth, where they had been subjected to the action of the intense heat supposed to exist in the centre of the earth, are now supposed to be in reality ancient sedimentary strata, slowly deposited by the sea, and upheaved by the contraction of the crust, or by some other force of upheaval acting from the centre. Upon the sides of mountains, or on their summits, now thousands of feet above the level of the ocean, unquestionable traces of the action of the sea can be found. And the scientific observer of to-day sees all about him evidences that the immense work of the creation of continents, commenced by the sea in the earliest periods of time, is to-day continuing without relaxation or intermission, and with such energy that even during the short course of a single life great changes can be seen to have been produced. Here and there a coast, subject to the beating of the serf, is seen to be slowly undermined, disintegrated, worn down and carried away, while in another place the material is depositedby the sea, and sandy beaches or promontories are built up. New rocks also, differing in appearance and constitution from those worn away, are formed. But beside this action of the sea upon the coasts, in constantly changing the configuration of the land, modern observation has shown us that animal life is an agent constantly at work within the sea itself, in the formation of new lands. The innumerable minute forms of life with which the sea swarms; the coral polyps, the shells, the sponges, and the animalculæ of all kinds, are constantly engaged in consuming the food they find, in reproducing themselves, and in dying. From the various matters brought down to the ocean by the rivers of the land, they secrete their shells or other coverings; and as generation after generation they die, these falling to the bottom form immense banks, or plains, which some future action of upheaval will bring above the surface to form the material for new continents or islands.

Thus while the ocean prepares the materials for the future continents in its bosom, it also furnishes the waters which wash away the lands already existing. To the thought of modern science the granite peaks, the snow-clad mountains, immovable and eternal as they seem, are constantly disintegrating, and partake, with every thing else in creation, the eternal round of change which is constantly going on. From the sea, by evaporation, rise the vapors which, condensing against the sides of the mountains, form the glaciers; and these, slowly sliding down toward the plains, are such efficient agents in wearing away the mountains, grinding up their solid rocks and preparing the gravel which the mountain streams distribute over the plains. From the sea the atmosphere receives the moisture destined to return in rain from the clouds; to feed the brooks whose union forms the rivers, destined again to return to the sea the waters it provided, and thus keep up, in a single, mighty and endless circulation, the waters of the globe.

Thus to the agency of the ocean we are indebted for our rivers, which have played such an important part in the geological history of the earth, in the distribution of the flora and fauna of various countries, and on the life of man himself. In the study also of the climates of the earth, and their effects upon life, we find the ocean bears a most important part. As the circulation of the atmosphere mingles the heated air from the equator with that of the frozen regions of the poles, so the currents of the ocean circulate about the earth, blending the contrasts of climate, and making a harmonious whole of all the different portions. Thus, instead of considering the ocean as the barren waste of desolation it appeared to the ancients, to the modern thinker the ocean has, layer by layer, deposited the land from its bosom, and now by its vapors provides the rains which support its vegetable life, upon which all other life depends, and creates the rivers and the springs, which play such an important part in the modification of the interior of continents, at the greatest distance from the sea.

The mean depth of the whole mass of the ocean waters of the globe is estimated at about three miles, since measurements have shown that the basins of the Atlantic and Northern Pacific are deeper than this by hundreds of thousands of fathoms. The extent covered by the surface of the ocean has been estimated at more than 145,000,000 of square miles, and with this estimate, the sea is calculated to form a volume of about two and one-half million billions of cubic yards, or about the five hundred and sixtieth part of the planet itself. The highest point of the land raised above the level of the sea is much less elevated than the bottom of the sea is depressed from the same level, so that the mass of the land above this level can be estimated only at about a fortieth part of the mass of the waters.

The specific gravity of sea water is greater than that offresh. This comes from the various matters which it holds in solution. This difference varies with different seas; with the quantity of matters held in solution; with the amount of evaporation; the size and number of rivers flowing into the various seas; the ice melting into them; the currents, and various other causes. The average quantity of salts held in solution in sea water is estimated at 34.40 parts in 1,000, and this average is the same in all seas. The quantity of common salt held in solution is always a little more than three-quarters (75.786) of the total mineral matter held in solution. The salt of the sea averages, if the water is evaporated, about two inches to every fathom; so that, were the ocean dried up, a layer of salt about two hundred and thirty feet thick would remain on the bottom, or the whole salt of the sea would measure more than a thousand millions of cubic miles. This vast quantity of salt in the sea explains how the enormous beds of rock salt were formed, when the lands now exposed were covered by the waters.

Beside the oxygen and hydrogen which constitute its waters, the sea contains chlorine, nitrogen, carbon, bromine, iodine, fluorine, sulphur, phosphorus, silicon, sodium, potassium, boron, aluminium, magnesium, calcium, strontium, barium. From the various sea-weeds most of these substances can be obtained. Copper, lead, zinc, cobalt, nickel and manganese have also been found in their ashes. Iron has also been obtained from sea water, and a trace of silver also is often deposited by the magnetic current established between the sheeting of ships and the salt water. Though only a trace is thus found, yet it has been estimated that the whole waters of the ocean contain in solution two million tons of silver. In the boilers of ocean steamships, which use sea water, arsenic has also been found.

Sea water also retains dissolved air better than fresh water, and the bulk of this in ocean water is generally greater by athird than that found in river water. It varies from a fifth to a thirtieth, and gradually increases from the surface to a depth of about three hundred and twenty-five to three hundred and eighty fathoms. The uniformity in the constitution of the waters of the sea is chiefly caused by the action of the waves, which finally mix and mingle the waters into a homogeneous mass. The waves of the sea are caused chiefly by the action of the wind, and the effect continues even after the wind has ceased. One of the grandest spectacles at sea is offered by the regular movement of the waves in perfectly calm weather, when not a breath of air stirs the sails. During to the Autumnal calm under the Tropic of Cancer, these waves appear with astonishing regularity at intervals of two hundred to three hundred yards, sweep under the ship, and as far as the eye can reach, are seen advancing and passing away, as regularly as the furrows in a field. Such waves are caused by the regularity of the trade winds. The height of the waves is not the same in all seas. It is greater where the basin is deeper in proportion to the surface, and also as the water is fresher and yields easier to the impulses of the wind.

The height of waves has been variously measured. Some observers have claimed to see them over one hundred feet high, but from twenty to fifty feet is about the average of observations on the Atlantic. The breadth of a wave is calculated as fifteen times its height. Thus, a wave four feet high is sixty feet broad. The inclination of the sides of the waves varies however with the force of the wind, and with the strength of the secondary vibrations in the water, which may interfere with the primary ones. The speed of the waves is only apparent like the motion in a length of cloth shaken up and down. Floating objects do not change their relative positions, but slowly, except in rising and falling with the wave. The real movement of the sea is that of a drifting current, which is slowly formed under the action of the wind, and thisis not rapid, but slow. The astronomer Airey says that every wave 100 feet wide, traversing a sea 164 fathoms in average depth, has a velocity of nearly 2,100 feet a second, or about fifteen and one-half miles an hour; a wave 674 feet, moving over a sea 1,640 fathoms deep, travels more than 69 feet a second, or nearly fifty miles an hour, and this last calculation may be taken as the average speed of storm waves in great seas. As, therefore, we can calculate the velocity of waves from their width and the known depth of the sea, we can calculate the depth of the sea from the known size and velocity of the waves. By this method the depth of the Pacific between Japan and California has been calculated from the size and speed of an earthquake wave, which was set in motion by an eruption in Japan. The accuracy of the calculation was afterward established by actual soundings.

It was formerly supposed that the disturbance of the waves did not penetrate the depth of the water, below four or six fathoms, but this has been found, on further observation, erroneous. Sand and mud have been brought up from a depth of a hundred fathoms below the surface, and experiments have shown that waves have a vertical influence 350 times their height. Thus a wave a foot high influences the bottom at a depth of 50 fathoms, and a billow of the ocean 33 feet high is felt below at a distance of 1 3/43/4 miles. At these great depths the action of the wave is perhaps imaginary, but to this reason we can ascribe the heavy swells which are often so dangerous. A hidden rock, far below the surface, arrests some moving wave and causes an eddy, which, rising to the surface, produces the "ground swells" which suddenly rise in the neighborhood of submarine banks and endanger ships. This cause also explains the tide races, which, coming from the depths of the ocean, advance suddenly upon the beaches, destroying all that opposes them. It is this cause which makes the position of light-houses upon certain reefs so dangerous. The Bell Rock house,on the Scottish coast, stands 112 feet above the rock, and yet it is often covered with the waves and foam, even after the tempest has ceased to rage. Such light-houses are often washed away; as that at Minot's Ledge, on the coast of Massachusetts, has often been. In consequence the modern method of building these structures differs from that formerly in use. The custom was to build them of solid masonry, hoping to make them strong enough to resist the waves. Now they are generally built of iron lattice open work, making the bars as slender as is consistent with the proper strength, so as to offer the least resisting surface to the rushing water. This open frame work is raised up high enough, if possible, to place the house and lantern above the reach of the body of the wave.

The force of the water in such positions is prodigious. Stephenson calculated that the sea dashed against the Bell Rock light-house with a force of 17 tons for every square yard. At breakwaters in exposed situations the sea has been known to seize blocks of stone weighing tons, and hurl them as a child would pebbles. At Cherbourg, in France, the heaviest cannon have been displaced; and at Barra Head, in the Hebrides, Stephenson states that a block of stone weighing 43 tons was driven by the breakers about two yards. At Plymouth, England, a vessel weighing 200 tons was thrown up on the top of the dike, and left there uninjured. At Dunkirk it has been found that from the dash of the breakers the ground trembles for more than a mile from the shore. Results of this kind, to which our attention is specially directed, since they affect man's work, show us what must be the effect produced by the sea, in constantly eating away the shore; altering the coast lines; changing continents, and building them up elsewhere; and suggest how much greater than what we see must have been the effects of the sea upon the land during the countless ages in which it has been at work.

The currents in the ocean, which constitute the real motionof its waters, are very important in the study of the influence of the sea upon the land. By these the circulation of the waters of the globe is carried on. The warm water of the equatorial regions seeking the poles, and a counter movement from the poles to the equator, is established. By their means a constant mingling of the waters on the face of the whole earth is maintained, and the wonderful similarity of its different portions, in their composition, appearance, and the substances held in solution, is produced. The chief causes of this grand circulation are found in the heat of the sun and in the rotation of the earth upon its axis. By the evaporation of the waters in the tropics the surface of that portion of the ocean is estimated to be lowered more than fourteen feet yearly. By this means not only is the atmosphere provided with its store of vapor, to be dispensed in rain upon the land, and thus returned again to the sea, but this lowering of the surface of the ocean, in one part, leads to the currents flowing from the others to restore the equilibrium. The same cause leading also to the circulation of the atmosphere, produces the trade winds, which aid in producing the currents in the ocean.

Now that by study and observation mankind have arrived at the conception of the form of the earth, at its general features, and can, in idea, grasp it as a whole, the opportunity is prepared for the methodical study of its parts, and their relation to each other; and this is the subject which for the first time in the history of mankind is offered to the physical geographer, with the certainty that none of his observations can be lost, but that they all are important, and can each be referred to its proper place. Another movement of the ocean is the tides. To the ancients, unacquainted with the form of the earth, its position in space, or its relations with the other bodies of the solar system, the tides were naturally inexplicable. It has been possible, only in modern times to attempt their explanation. Kepler first indicated the course to be followed; andDescartes and Newton each gave a theory; the first that of the pressure of the waters; the last, that of the attraction of the sun and moon upon the waters. This last theory is the one generally accepted, since it has been found satisfactory in most respects; yet it still has its opponents. Now, however, that the telegraph has been discovered, and a means thus afforded for instantaneous communication between observers at distant points, it has become possible to organize a simultaneous observation of the tides at various places, and eventually this will be done, so that the theory that the tides are caused by the attraction of the sun and moon will be entirely proved or rejected according as it will be found consistent with the facts observed.

In this connection an interesting instance of the different manner in which the ancients regarded natural phenomena, from that in which the moderns regard the same occurrences, is found in the fear the ancients had of the two monsters Scylla and Charybdis, which were the fabled guardians of the Straits of Messina. At present there are no straits in the Mediterranean more frequented than those of Messina. By the soundings which have been made there, these monsters had been effectually destroyed, and the whirlpools are known to be produced by the ebb and flow of the tide, causing a greater flow of water than can be accommodated by the narrow channel. The width of the channel is hardly two miles, and at low tide it has often been crossed on horseback, by swimming. The rising tide tends toward the north, from the Ionian to the Tyrrhenian sea, and the falling tide in the opposite direction. There is a strife between these currents, and on their confines eddies are formed which ships avoid, but there is no danger unless the wind blows strongly against the tide.

Besides the influence of the currents and the tides of the ocean in altering the configuration of the land, the sea is the home of innumerable forms of animal life, which are constantly laboring in the same direction. It has been truly said, thata beef bone, thrown overboard by a sailor on a ship, may form the nucleus of a new continent. The entire chalk cliffs of England were formed from the minute shells deposited by the small animals which secreted them. At their death these fell to the bottom, and thus slowly through the ages the deposit was formed. The recent deep sea dredgings have shown the sea, at all depths, is full of animal life; and as the steady fall of snow-flakes in a winter's storm, piled up by currents of wind, form the drifts, or falling quietly, cover the ground uniformly, so the sea is full of the minute shells, which, carried by currents, form banks, or, falling evenly, prepare the plains which in the future will appear, in some upheaval, to form new continents.

In the United States the peninsula of Florida is an evidence of the land produced by the labor of the coral polyp. Florida has now ceased to increase toward the east, for on this side it touches the deep waters of the gulf, and the polyps can live only in shallow water. The peninsula increases only on its southern and western coasts. The cut at the end of this chapter represents the appearance of coral islands as they first rise to the surface, before the gathering soil provides the conditions for covering them with the luxuriant vegetation of the tropics.

The cut at the head of this chapter, of an aquarium, represents a new appliance of modern times, which is a most valuable aid in our obtaining a knowledge of the habits of the animals living in the sea. In fresh water, as well as in salt, the mutual relations of the vegetable and animal life serve to keep the water from becoming stagnant. The plants secrete the carbonic acid gas, which the animals give to the water by breathing, and in so doing free the oxygen which the animals require. In keeping therefore an aquarium, the desired point is to provide such a natural proportion of vegetable and animal life as shall preserve this balance. In many of the largermuseums of Europe, large aquariums have been built, and an opportunity thus afforded for the study of the various animal forms, the habits of the vegetable growths, and their relations. Some of these structures are so arranged that they surround a room which receives its light only through the water in the aquaria, and thus the spectator, without disturbing the fish, can watch them feeding and performing all their actions.

From this arrangement of the aquaria, as the light passes from the water to the eye, the spectator is not disturbed in his vision, as he is by trying to look into the water from above, by the refraction of the light. A great deal that has been learned in modern times concerning the growth of the vegetation of the sea, of the habits of the animals, of their manner of life, their food and their growth, has been obtained from the chance of observation afforded by the various aquaria. Beside the positive benefits which have thus resulted from the public aquaria, those in smaller form afford for the lover of natural history a new and interesting way of carrying on his studies. In this way also the habits of observation are formed in the young, and it is fair to believe that the spirit of inquiry thus excited will tend to increase the knowledge of the phenomena of life, and its relations to the conditions of existence.

It has been by this course that the race itself has risen from barbarism to its present degree of civilization, and with the new appliances of modern times, it is evidently impossible to limit the probabilities of advance in the future.

A few facts about the extent of our commerce will show the difference of the spirit with which the ocean is regarded in modern times, compared with that prevailing in antiquity; and the different use we have learned to make of it, from the time when the exchanges of the world were confined to a few coasters, who hardly ventured out of the sight of land. To give even the most condensed summary of the world's commerce to-day would require a series of volumes; but afew figures taken from our own will enable the reader to judge of that which is now going on all over the world, uniting the most distantly separated nations; enabling them to become acquainted with each other; and impressing them with the fact that by industry alone are the material comforts of life to be attained, and that the task before humanity is to become acquainted with the products of the world, with the forces of which it is the theatre, and learn to control them for our own benefit.

From the report of the Bureau of Statistics, for a portion of 1873, we learn that the imports and exports of the United States during eight months, ending with February, 1873, amounted to the following totals: Imported in American vessels, $104,891,248; imported in foreign vessels, $317,043,490; imported in land vehicles, $12,356,325. During the same period the domestic exports in American vessels amounted to a total of $108,246,698; in foreign vessels, $311,816,048; and in land vehicles, $5,282,949. At the same time the re-exportation of foreign products amounted in American vessels to $5,147,805; in foreign vessels to $10,938,300; and in land vehicles to $1,693,795.

The number and tonnage of American and foreign vessels engaged in the foreign trade, which entered and cleared during the twelve months ending with February, 1873, was as follows: American vessels, 10,928, carrying 3,597,474 tons; foreign vessels, 19,220, carrying 7,622,416 tons. The report of the Bureau for 1872, gives the following totals of the number of vessels and their tonnage engaged in the commerce of the United States. Upon the Atlantic and Gulf coasts, 21,940 vessels carrying 2,916,001,058 tons. On the Western rivers, 1,476 vessels carrying 354,938,052 tons. On the Northern lakes 5,339 vessels, carrying 726,105,051 tons. On the Pacific coast, 1,094 vessels carrying 161,987,050.

From the port of New York alone there are now thirteenlines of steamships plying to Europe. Of these the Anchor line has 15 steamers, with a tonnage of 36,127 tons; the Baltic Lloyds has 4 vessels of 9,200 tons; the Cardiff (a Welsh) line has three vessels of 8,000 tons; the Cunard has 23 vessels of 59,308 tons; the Holland (direct) line has two vessels of 4,000 tons; the General Transatlantic (a French line) has 5 vessels of 17,000 tons; the Hamburg has 15 vessels of 45,000 tons; the Inman line has 12 vessels of 34,811; the Liverpool and Great Western line has 7 vessels of 23,573 tons; the North German line has 20 vessels of 60,000 tons; the National line has 12 vessels of 50,062 tons; the State line has 3 vessels of 7,500 tons; and the White Star line has 6 vessels of 23,064 tons. Beside these ships, the thirteen companies are building from 30 to 40 more steamers to meet the demand for freight.

The ocean has thus become almost a steam ferry; almost every day a steamer leaves for Europe. With this knowledge of how far we have progressed in becoming acquainted with the ocean, it will be well to consider for a moment how much still remains for us to explore. In the middle ages, and even down to modern times, the maps of the world represented all unknown lands as inhabited by monsters; but every voyage made by discoverers has contracted the limits of these fables, until they have finally about disappeared. Still at the North Pole and in the Antarctic regions areas extending over a space of 2,900,000 and 8,700,000 square miles, respectively, have been, up to this time, unvisited. The icebergs and mountains of ice have kept them from our accurate investigations. The difficulties of such a sea are well shown in the adjoining illustration.

Discoveries have also to be made in the interiors of Africa, Asia, South America and Australia before the civilized portions of the race can claim a complete knowledge of the earth, their common dwelling-place. Every year, however, the portionsunexplored grow smaller and smaller, so that we are justified in believing that eventually the whole world will be known to us, from actual observation.

APPEARANCE OF ICE.

APPEARANCE OF ICE.

APPEARANCE OF ICE.

LIGHT SHIP AND INCOMING VESSEL.

LIGHT SHIP AND INCOMING VESSEL.

LIGHT SHIP AND INCOMING VESSEL.

Another difference which our extended knowledge of the world has produced is this: The mariner now approaching an unknown coast does not fear to meet monsters, but looks out for the light-house, the light-ships, the buoys, and other evidences of civilization, by which the dangers of the coast are pointed out to the voyager. As a contrast with some of the pictures already given, representing the approach to the land of the early explorers, the illustration of the light-ship will show how differently to-day a voyage approaches its termination. Instead of looking out for enemies, and preparing weapons for use, a package of newspapers and letters is got ready, and the news boat, which lies ready at hand, is prompt to seize them, and hasten with these to spread the news of another safe arrival. It is thus that science, which is gradually preparing the means for converting the globe into one great organism for the benefit of mankind, points out the way for making it the abode of that harmony, peace and plenty which has been dreamed of by the poets of all time. For this it is only necessary that our moral progress should keep pace with our advance in knowledge. The globe will never become the abode of perfect harmony until men are united in a universal league of justice and peace. And in aiding toward the production of this most desirable consummation, what has been here written will show how important has been the part taken by the ocean.

A CORAL ISLAND.

A CORAL ISLAND.

A CORAL ISLAND.

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