The fauna and flora of the Sea are as much the creatures of Climate, and are as dependent for their well-being upon temperature, as are the fauna and flora of the dry land. Were it not so, we should find the fish and the algæ, the marine insect and the coral, distributed equally and alike in all parts of the ocean; the polar whale would delight in the torrid zone; and the habitat of the pearl oyster would be also under the iceberg, or in frigid waters colder than the melting ice.
The coral islands, reefs, and beds with which the Pacific Ocean is studded and garnished, were built up of materials which a certain kind of insect quarried from the sea-water. The currents of the sea ministered to this little insect; they were itshod-carriers. When fresh supplies of solid matter were wanted for the coral rock upon which the foundations of the Polynesian Islands were laid, these hod-carriers brought them in unfailing streams of sea-water, loaded with food and building-materials for the coralline: the obedient currents thread the widest and the deepest sea. Now we know that its adaptations are suited to all the wants of every one of its inhabitants,—to the wants of the coral insect as well as those of the whale. Hencewe knowthat the sea has its system of circulation: for it transports materials for the coral rock from one part of the world to another; its currents receive them from rivers, and hand them over to the little mason for the structure of the most stupendous works of solid masonry that man has ever seen—the coral islands of the sea.
Between the hottest hour of the day and the coldest hour of the night there is frequently a change of four degrees in the Temperature of the Sea. Taking one-fifth of the Atlantic Ocean for the scene of operation, and the difference of fourdegrees to extend only ten feet below the surface, the total and absolute change made in such a mass of sea-water, by altering its temperature two degrees, is equivalent to a change in its volume of 390,000,000 cubic feet.
Captain Glynn, U.S.N., has made some interesting observations, ranging over 200° of latitude, in different oceans, in very high latitudes, and near the equator. His apparatus was simple: a common white dinner-plate, slung so as to lie in the water horizontally, and sunk by an iron pot with a line. Numbering the fathoms at which the plate was visible below the surface, Captain Glynn saw it on two occasions, at the maximum, twenty-five fathoms (150 feet) deep; the water was extraordinarily clear, and to lie in the boat and look down was like looking down from the mast-head; and the objects were clearly defined to a great depth.
In its entire length, the basin of this sea is a long trough, separating the Old World from the New, and extending probably from pole to pole.
This ocean-furrow was scored into the solid crust of our planet by the Almighty hand, that there the waters which “he called seas” might be gathered together so as to “let the dry land appear,” and fit the earth for the habitation of man.
From the top of Chimborazo to the bottom of the Atlantic, at the deepest place yet recognised by the plummet in the North Atlantic, the distance in a vertical line is nine miles.
Could the waters of the Atlantic be drawn off, so as to expose to view this great sea-gash, which separates continents, and extends from the Arctic to the Antarctic, it would present a scene the most grand, rugged, and imposing. The very ribs of the solid earth, with the foundations of the sea, would be brought to light; and we should have presented to us at one view, in the empty cradle of the ocean, “a thousand fearful wrecks,” with that dreadful array of dead men’s skulls, great anchors, heaps of pearls and inestimable stones, which, in the dreamer’s eye, lie scattered on the bottom of the sea, making it hideous with sights of ugly death.
Lieutenant Maury has, in a series of charts of the North and South Atlantic, exhibited, by means of colours, the prevalence of Gales over the more stormy parts of the oceans for each month in the year. One colour shows the region in whichthere is a gale every six days; another colour every six to ten days; another every ten to fourteen days: and there is a separate chart for each month and each ocean.
Between Humboldt’s Current of Peru and the great equatorial flow, there is “a desolate region,” rarely visited by the whale, either sperm or right. Formerly this part of the ocean was seldom whitened by the sails of a ship, or enlivened by the presence of man. Neither the industrial pursuits of the sea nor the highways of commerce called him into it. Now and then a roving cruiser or an enterprising whalesman passed that way; but to all else it was an unfrequented part of the ocean, and so remained until the gold-fields of Australia and the guano islands of Peru made it a thoroughfare. All vessels bound from Australia to South America now pass through it; and in the journals of some of them it is described as a region almost void of the signs of life in both sea and air. In the South-Pacific Ocean especially, where there is such a wide expanse of water, sea-birds often exhibit a companionship with a vessel, and will follow and keep company with it through storm and calm for weeks together. Even the albatross and Cape pigeon, that delight in the stormy regions of Cape Horn and the inhospitable climates of the Antarctic regions, not unfrequently accompany vessels into the perpetual summer of the tropics. The sea-birds that join the ship as she clears Australia will, it is said, follow her to this region, and then disappear. Even the chirp of the stormy petrel ceases to be heard here, and the sea itself is said to be singularly barren of “moving creatures that have life.”
Seafaring people often throw a bottle overboard, with a paper stating the time and place at which it is done. In the absence of other information as to Currents, that afforded by these mute little navigators is of great value. They leave no track behind them, it is true, and their routes cannot be ascertained; but knowing where they are cast, and seeing where they are found, some idea may be formed as to their course. Straight lines may at least be drawn, showing the shortest distance from the beginning to the end of their voyage, with the time elapsed. Admiral Beechey has prepared a chart, representing, in this way, the tracks of more than 100 bottles. From this it appears that the waters from every quarter of the Atlantic tend towards the Gulf of Mexico and its stream. Bottles cast into the sea midway between the Old and the NewWorlds, near the coasts of Europe, Africa, and America at the extreme north or farthest south, have been found either in the West Indies, or the British Isles, or within the well-known range of Gulf-Stream waters.
are the belts of calms and light airs which border the polar edge of the north-east trade-winds. They are so called from the circumstance that vessels formerly bound from New England to the West Indies, with a deck-load of horses, were often so delayed in this calm belt of Cancer, that, from the want of water for their animals, they were compelled to throw a portion of them overboard.
Captain Kingman, of the American clipper-shipShooting Star, in lat. 8° 46′ S., long. 105° 30′ E., describes a patch ofwhite water, about twenty-three miles in length, making the whole ocean appear like a plain covered with snow. He filled a 60-gallon tub with the water, and found it to contain small luminous particles seeming to be alive with worms and insects, resembling a grand display of rockets and serpents seen at a great distance in a dark night; some of the serpents appearing to be six inches in length, and very luminous. On being taken up, they emitted light until brought within a few feet of a lamp, when nothing was visible; but by aid of a sextant’s magnifier they could be plainly seen—a jelly-like substance, without colour. A specimen two inches long was visible to the naked eye; it was about the size of a large hair, and tapered at the ends. By bringing one end within about one-fourth of an inch of a lighted lamp, the flame was attracted towards it, and burned with a red light; the substance crisped in burning, something like hair, or appeared of a red heat before being consumed. In a glass of the water there were several small round substances (say 1/16th of an inch in diameter) which had the power of expanding and contracting; when expanded, the outer rim appeared like a circular saw, the teeth turned inward.
The scene from the clipper’s deck was one of awful grandeur: the sea having turned to phosphorus, and the heavens being hung in blackness, and the stars going out, seemed to indicate that all nature was preparing for that last grand conflagration which we are taught to believe will annihilate this material world.
Long before the introduction of the Log, hour-glasses wereused to tell the distance in sailing. Columbus, Juan de la Cosa, Sebastian Cabot, and Vasco de Gama, were not acquainted with the Log and its mode of application; and they estimated the ship’s speed merely by the eye, while they found the distance they had made by the running-down of the sand in theampotellas, or hour-glasses. The Log for the measurement of the distance traversed is stated by writers on navigation not to have been invented until the end of the sixteenth or the beginning of the seventeenth century (seeEncyclopædia Britannica, 7th edition, 1842). The precise date is not known; but it is certain that Pigafetta, the companion of Magellan, speaks, in 1521, of the Log as a well-known means of finding the course passed over. Navarete places the use of the log-line in English ships in 1577.
The ocean teems with life, we know. Of the four elements of the old philosophers,—fire, earth, air, and water,—perhaps the sea most of all abounds with living creatures. The space occupied on the surface of our planet by the different families of animals and their remains is inversely as the size of the individual; the smaller the animal, generally speaking, the greater the space occupied by his remains. Take the elephant and his remains, and a microscopic animal and his, and compare them; the contrast as to space occupied is as striking as that of the coral reef or island with the dimensions of the whale. The graveyard that would hold the corallines, is larger than the graveyard that would hold the elephants.
At some few places under the tropics, no bottom has been found with soundings of 26,000 feet, or more than four miles; whilst in the air, if, according to Wollaston, we may assume that it has a limit from which waves of sound may be reverberated, the phenomenon of twilight would incline us to assume a height at least nine times as great. The aerial ocean rests partly on the solid earth, whose mountain-chains and elevated plateaus rise like green wooded shoals, and partly on the sea, whose surface forms a moving base, on which rest the lower, denser, and more saturated strata of air.—Humboldt’s Cosmos, vol. i.
The old Alexandrian mathematicians, on the testimony of Plutarch, believed the depth of the sea to depend on the height of the mountains. Mr. W. Darling has propounded to the British Association the theory, that as the sea covers three times the area of the land, so it is reasonable to suppose that the depth of the ocean, and that for a large portion, is threetimes as great as the height of the highest mountain. Recent soundings show depths in the sea much greater than any elevations on the surface of the earth; for a line has been veered to the extent of seven miles.—Dr. Scoresby.
In the dynamical theory of the tides, the ratio of the effects of the sun and moon depends, not only on the masses, distances, and periodic times of the two luminaries, but also on the Depth of the Sea; and this, accordingly, may be computed when the other quantities are known. In this manner Professor Haughton has deduced, from the solar and lunar coefficients of the diurnal tide, a mean depth of 5·12 miles; a result which accords in a remarkable manner with that inferred from the ratio of the semi-diurnal co-efficients as obtained by Laplace from the Brest observations. Professor Hennessey states, that from what is now known regarding the depth of the ocean, the continents would appear as plateaus elevated above the oceanic depressions to an amount which, although small compared to the earth’s radius, would be considerable when compared to its outswelling at the equator and its flattening towards the poles; and the surface thus presented would be the true surface of the earth.
The greatest depths at which the bottom of the sea has been reached with the plummet are in the North-Atlantic Ocean; and the places where it has been fathomed (by the United-States deep-sea sounding apparatus) do not show it to be deeper than 25,000 feet = 4 miles, 1293 yards, 1 foot. The deepest place in this ocean is probably between the parallels of 35° and 40° north latitude, and immediately to the southward of the Grand Banks of Newfoundland.
It appears that, with one exception, the bottom of the North-Atlantic Ocean, as far as examined, from the depth of about sixty fathoms to that of more than two miles (2000 fathoms), is literally nothing but a mass of microscopic shells. Not one of the animalcules from these shells has been found living in the surface-waters, nor in shallow water along the shore. Hence arises the question, Do they live on the bottom, at the immense depths where the shells are found; or are they borne by submarine currents from their real habitat?
It appears that, with one exception, the bottom of the North-Atlantic Ocean, as far as examined, from the depth of about sixty fathoms to that of more than two miles (2000 fathoms), is literally nothing but a mass of microscopic shells. Not one of the animalcules from these shells has been found living in the surface-waters, nor in shallow water along the shore. Hence arises the question, Do they live on the bottom, at the immense depths where the shells are found; or are they borne by submarine currents from their real habitat?
The French engineers, at the beginning of the present century, came to the conclusion that the Red Sea was about thirty feet above the Mediterranean: but the observations of Mr. Robert Stephenson, the English engineer, at Suez; of M. Negretti, the Austrian, at Tineh, near the ancient Pelusium; and the levellings of Messrs. Talabat, Bourdaloue, and their assistantsbetween the two seas;—have proved that the low-water mark of ordinary tides at Suez and Tineh is very nearly on the same levels, the difference being that at Suez it is rather more than one inch lower.—Leonard Horner;Proceedings of the Royal Society, 1855.
Soundings made in the Mediterranean suffice to indicate depths equal to the average height of the mountains girding round this great basin; and, if one particular experiment may be credited, reaching even to 15,000 feet—an equivalent to the elevation of the highest Alps. This sounding was made about ninety miles east of Malta. Between Cyprus and Egypt, 6000 feet of line had been let down without reaching the bottom. Other deep soundings have been made in other places with similar results. In the lines of sea between Egypt and the Archipelago, it is stated that one sounding made by theTartarusbetween Alexandria and Rhodes reached bottom at the depth of 9900 feet; another, between Alexandria and Candia, gave a depth of 300 feet beyond this. These single soundings, indeed, whether of ocean or sea, are always open to the certainty that greater as well as lesser depths must exist, to which no line has ever been sunk; a case coming under that general law of probabilities so largely applicable in every part of physics. In the Mediterranean especially, which has so many aspects of a sunken basin, there may be abysses of depth here and there which no plummet is ever destined to reach.—Edinburgh Review.
M. Ehrenberg, while navigating the Red Sea, observed that the red colour of its waters was owing to enormous quantities of a new animal, which has received the name ofoscillatoria rubescens, and which seems to be the same with what Haller has described as apurple confervaswimming in water; yet Dr. Bonar, in his work entitledThe Desert of Sinai, records:
Blue I have called the sea; yet not strictly so, save in the far distance. It is neither arednor abluesea, but emphatically green,—yes, green, of the most brilliant kind I ever saw. This is produced by the immense tracts of shallow water, with yellow sand beneath, which always gives this green to the sea, even in the absence of verdure on the shore or sea-weeds beneath. Theblueof the sky and theyellowof the sands meeting and intermingling in the water, form thegreenof the sea; the water being the medium in which the mixing or fusing of the colours takes place.
Blue I have called the sea; yet not strictly so, save in the far distance. It is neither arednor abluesea, but emphatically green,—yes, green, of the most brilliant kind I ever saw. This is produced by the immense tracts of shallow water, with yellow sand beneath, which always gives this green to the sea, even in the absence of verdure on the shore or sea-weeds beneath. Theblueof the sky and theyellowof the sands meeting and intermingling in the water, form thegreenof the sea; the water being the medium in which the mixing or fusing of the colours takes place.
The phenomena with this name and that of “Squid” are occasioned by the presence of phosphorescent animalcules. Theyare especially produced in the intertropical seas, and they appear to be chiefly abundant in the Gulf of Guinea and in the Arabian Gulf. In the latter, the phenomenon was known to the ancients more than a century before the Christian era, as may be seen from a curious passage from the geography of Agatharcides: “Along this country (the coast of Arabia) the sea has a white aspect like a river: the cause of this phenomenon is a subject of astonishment to us.” M. Quatrefages has discovered that theNoctilucæwhich produce this phenomenon do not always give out clear and brilliant sparks, but that under certain circumstances this light is replaced by a steady clearness, which gives in these animalcules a white colour. The waters in which they have been observed do not change their place to any sensible degree.
Among the minute shells which have been fished up from the great telegraphic plateau at the bottom of the sea between Newfoundland and Ireland, the microscope has failed to detect a single particle of sand or gravel; and the inference is, that there, if any where, the waters of the sea are at rest. There is not motion enough there to abrade these very delicate organisms, nor current enough to sweep them about and mix them up with a grain of the finest sand, nor the smallest particle of gravel from the loose beds ofdébristhat here and there strew the bottom of the sea. The animalculæ probably do not live or die there. They would have had no light there; and, if they lived there, their frail textures would be subjected in their growth to a pressure upon them of a column of water 12,000 feet high, equal to the weight of 400 atmospheres. They probably live and sport near the surface, where they can feel the genial influence of both light and heat, and are buried in the lichen caves below after death.
It is now suggested, that henceforward we should view the surface of the sea as a nursery teeming with nascent organisms, and its depths as the cemetery for families of living creatures that outnumber the sands on the sea-shore for multitude.
Where there is a nursery, hard by there will be found also a graveyard,—such is the condition of the animal world. But it never occurred to us before to consider the surface of the sea as one wide nursery, its every ripple as a cradle, and its bottom one vast burial-place.—Lieut. Maury.
It has been replied, In order to preserve it in a state of purity; which is, however, untenable, mainly from the fact thatorganic impurities in a vast body of moving water, whether fresh or salt, become rapidly lost, so as apparently to have called forth a special agency to arrest the total organised matter in its final oscillation between the organic and inorganic worlds. Thus countless hosts of microscopic creatures swarm in most waters, their principal function being, as Professor Owen surmises, to feed upon and thus restore to the living chain the almost unorganised matter of various zones. These creatures preying upon one another, and being preyed upon by others in their turn, the circulation of organic matter is kept up. If we do not adopt this view, we must at least look upon the Infusoria and Foraminifera as scavenger agents to prevent an undue accumulation of decaying matter; and thus the salt condition of the sea is not a necessity.
Nor is the amount of saline matter in the sea sufficient to arrest decomposition. That the sea is salt to render it of greater density, and by lowering its freezing point to preserve it from congelation to within a shorter distance of the poles, though admissible, scarcely meets the entire solution of the question. The freezing point of sea-water, for instance, is only 3½° F. lower than that of fresh water; hence, with the present distribution of land and sea—and still less, probably, with that which obtained in former geological epochs—no very important effects would have resulted had the ocean been fresh instead of salt.
Now Professor Chapman, of Toronto, suggests that the salt condition of the sea is mainly intended to regulate evaporation, and to prevent an undue excess of that phenomenon; saturated solutions evaporating more slowly than weak ones, and these latter more slowly again than pure water.
Here, then, we have a self-adjusting phenomenon and admirable contrivance in the balance of forces. If from any temporary cause there be an unusual amount of saline matter in the sea, evaporation goes on the more and more slowly; and, on the other hand, if this proportion be reduced by the addition of fresh water in undue excess, the evaporating power is the more and more increased—thus aiding time, in either instance, to restore the balance. The perfect system of oceanic circulation may be ascribed, in a great degree at least, if not wholly, to the effect produced by the salts of the sea upon the mobility and circulation of its waters.
Now this is an office which the sea performs in the economy of the universe by virtue of its saltness, and which it could not perform were its waters altogether fresh. And thus philosophers have a clue placed in their hands which will probably guide to one of the many hidden reasons that are embraced in the true answer to the question, “Why is the sea salt?”
Dry a towel in the sun, weigh it carefully, and note its weight. Then dip it into sea-water, wring it sufficiently to prevent its dripping, and weigh it again; the increase of the weight being that of the water imbibed by the cloth. It should then be thoroughly dried, and once more weighed; and the excess of this weight above the original weight of the cloth shows the quantity of the salt retained by it; then, by comparing the weight of this salt with that of the sea-water imbibed by the cloth, we shall find what proportion of salt was contained in the water.
The amount of common Salt in all the oceans is estimated by Schafhäutl at 3,051,342 cubic geographical miles. This would be about five times more than the mass of the Alps, and only one-third less than that of the Himalaya. The sulphate of soda equals 633,644·36 cubic miles, or is equal to the mass of the Alps; the chloride of magnesium, 441,811·80 cubic miles; the lime salts, 109,339·44 cubic miles. The above supposes the mean depth to be but 300 metres, as estimated by Humboldt. Admitting, with Laplace, that the mean depth is 1000 metres, which is more probable, the mass of marine salt will be more than double the mass of the Himalaya.—Silliman’s Journal, No. 16.
Taking the average depth of the ocean at two miles, and its average saltness at 3½ per cent, it appears that there is salt enough in the sea to cover to the thickness of one mile an area of 7,000,000 of square miles. Admit a transfer of such a quantity of matter from an average of half a mile above to one mile below the sea-level, and astronomers will show by calculation that it would alter the length of the day.
These 7,000,000 of cubic miles of crystal salt have not made the sea any fuller.
The solid constituents of sea-water amount to about 3½ per cent of its weight, or nearly half an ounce to the pound. Its saltness is caused as follows: Rivers which are constantly flowing into the ocean contain salts varying from 10 to 50, and even 100, grains per gallon. They are chiefly common salt, sulphate and carbonate of lime, magnesia,41soda, potash, and iron; and these are found to constitute the distinguishing characteristics of sea-water. The water which evaporates from thesea is nearly pure, containing but very minute traces of salts. Falling as rain upon the land, it washes the soil, percolates through the rocky layers, and becomes charged with saline substances, which are borne seaward by the returning currents. The ocean, therefore, is the great depository of every thing that water can dissolve and carry down from the surface of the continents; and as there is no channel for their escape, they consequently accumulate (Youmans’ Chemistry). They would constantly accumulate, as this very shrewd author remarks, were it not for the shells and insects of the sea and other agents.
The late Dr. Scoresby, from personal observations made in the course of twenty-one voyages to the Arctic Regions, thus describes these striking characteristics:
The coast scenes of Greenland are generally of an abrupt character, the mountains frequently rising in triangular profile; so much so, that it is sometimes not possible to effect their ascent. One of the most notable characteristics of the Arctic lands is the deception to which travellers are liable in regard to distances. The occasion of this is the quantity of light reflected from the snow, contrasted with the dark colour of the rocks. Several persons of considerable experience have been deceived in this way, imagining, for example, that they were close to the shore when in fact they were more than twenty miles off. The trees of these lands are not more than three inches above ground.Many of the icebergs are five miles in extent, and some are to be seen running along the shore measuring as much as thirteen miles. Dr. Scoresby has seen a cliff of ice supported on those floating masses 402 feet in height. There is no place in the world where animal life is to be found in greater profusion than in Greenland, Spitzbergen, Baffin’s Bay, and other portions of the Arctic regions. This is to be accounted for by the abundance and richness of the food supplied by the sea. The number of birds is especially remarkable. On one occasion, no less than a million of little hawks came in sight of Dr. Scoresby’s ship within a single hour.The various phenomena of the Greenland sea are very interesting. The different colours of the sea-water—olive or bottle-green, reddish-brown, and mustard—have, by the aid of the microscope, been found to be owing to animalculæ of these various colours: in a single drop of mustard-coloured water have been counted 26,450 animals. Another remarkable characteristic of the Greenland sea-water is its warm temperature—one, two, and three degrees above the freezing-point even in the cold season. This Dr. Scoresby accounts for by supposing the flow in that direction of warm currents from the south. The polar fields of ice are to be found from eight or nine to thirty or forty feet in thickness. By fastening a hook twelve or twenty inches in these masses of ice, a ship could ride out in safety the heaviest gales.
The coast scenes of Greenland are generally of an abrupt character, the mountains frequently rising in triangular profile; so much so, that it is sometimes not possible to effect their ascent. One of the most notable characteristics of the Arctic lands is the deception to which travellers are liable in regard to distances. The occasion of this is the quantity of light reflected from the snow, contrasted with the dark colour of the rocks. Several persons of considerable experience have been deceived in this way, imagining, for example, that they were close to the shore when in fact they were more than twenty miles off. The trees of these lands are not more than three inches above ground.
Many of the icebergs are five miles in extent, and some are to be seen running along the shore measuring as much as thirteen miles. Dr. Scoresby has seen a cliff of ice supported on those floating masses 402 feet in height. There is no place in the world where animal life is to be found in greater profusion than in Greenland, Spitzbergen, Baffin’s Bay, and other portions of the Arctic regions. This is to be accounted for by the abundance and richness of the food supplied by the sea. The number of birds is especially remarkable. On one occasion, no less than a million of little hawks came in sight of Dr. Scoresby’s ship within a single hour.
The various phenomena of the Greenland sea are very interesting. The different colours of the sea-water—olive or bottle-green, reddish-brown, and mustard—have, by the aid of the microscope, been found to be owing to animalculæ of these various colours: in a single drop of mustard-coloured water have been counted 26,450 animals. Another remarkable characteristic of the Greenland sea-water is its warm temperature—one, two, and three degrees above the freezing-point even in the cold season. This Dr. Scoresby accounts for by supposing the flow in that direction of warm currents from the south. The polar fields of ice are to be found from eight or nine to thirty or forty feet in thickness. By fastening a hook twelve or twenty inches in these masses of ice, a ship could ride out in safety the heaviest gales.
The ice of this berg, although opaque and vascular, is true glacier ice, having the fracture, lustre, and other external charactersof a nearly homogeneous growth. The iceberg is true ice, and is always dreaded by ships. Indeed, though modified by climate, and especially by the alternation of day and night, the polar glacier must be regarded as strictly atmospheric in its increments, and not essentially differing from the glacier of the Alps. The general appearance of a berg may be compared to frosted silver; but when its fractures are very extensive, the exposed faces have a very brilliant lustre. Nothing can be more exquisite than a fresh, cleanly fractured berg surface: it reminds one of the recent cleavage of sulphate of strontian—a resemblance more striking from the slightly lazulitic tinge of each.—U. S. Grinnel Expedition in Search of Sir J. Franklin.
The quantity of solid matter that is drifted out of the Polar Seas through one opening—Davis’s Straits—alone, and during a part of the year only, covers to the depth of seven feet an area of 300,000 square miles, and weighs not less than 18,000,000,000 tons. The quantity of water required to float and drive out this solid matter is probably many times greater than this. A quantity of water equal in weight to these two masses has to go in. The basin to receive these inflowing waters,i. e.the unexplored basin about the North Pole, includes an area of 1,500,000 square miles; and as the outflowing ice and water are at the surface, the return current must be submarine.
These two currents, therefore, it may be perceived, keep in motion between the temperate and polar regions of the earth a volume of water, in comparison with which the mighty Mississippi in its greatest floods sinks down to a mere rill.—Maury.
The following fact is striking: In 1662–3, Mr. Oldenburg, Secretary to the Royal Society, was ordered to register a paper entitled “Several Inquiries concerning Greenland, answered by Mr. Gray, who had visited those parts.” The nineteenth query was, “How near any one hath been known to approach the Pole.Answer.I once met upon the coast of Greenland a Hollander, that swore he had been but half a degree from the Pole, showing me his journal, which was also attested by his mate; wherethey had seen no ice or land, but all water.” Boyle mentions a similar account, which he received from an old Greenland master, on April 5, 1765.
Captain Sabine found discoloured water, supposed to be that of the Amazon, 300 miles distant in the ocean from theembouchure of that river. It was about 126 feet deep. Its specific gravity was = 1·0204, and the specific gravity of the sea-water = 1·0262. This appears to be the greatest distance from land at which river-water has been detected on the surface of the ocean. It was estimated to be moving at the rate of three miles an hour, and had been turned aside by an ocean-current. “It is not a little curious to reflect,” says Sir Henry de la Beche, “that the agitation and resistance of its particles should be sufficient to keep finely comminuted solid matter mechanically suspended, so that it would not be disposed freely to part with it except at its junction with the sea-water over which it flows, and where, from friction, it is sufficiently retarded.”
The Thames below Woolwich, in place of flowing upon a solid bottom, really flows upon the liquid bottom formed by the water of the sea. At the flow of the tide, the fresh water is raised, as it were, in a single mass by the salt water which flows in, and which ascends the bed of the river, while the fresh water continues to flow towards the sea.—Mr. Stevenson, in Jameson’s Journal.
On the southern coast of the island of Cuba, at a few miles from land, Springs of Fresh Water gush from the bed of the Ocean, probably under the influence of hydrostatic pressure, and rise through the midst of the salt water. They issue forth with such force that boats are cautious in approaching this locality, which has an ill repute on account of the high cross sea thus caused. Trading vessels sometimes visit these springs to take in a supply of fresh water, which is thus obtained in the open sea. The greater the depth from which the water is taken, the fresher it is found to be.
In the upper portion of the basin of the Orinoco and its tributaries, Nature has several times repeated the enigmatical phenomenon of the so-called “Black Waters.” The Atabapo, whose banks are adorned with Carolinias and arborescent Melastomas, is a river of a coffee-brown colour. In the shade of the palm-groves this colour seems about to pass into ink-black. When placed in transparent vessels, the water appears of a golden yellow. The image of the Southern Constellation is reflected with wonderful clearness in these black streams. When their waters flow gently, they afford to the observer, when taking astronomical observations with reflecting instruments, a most excellent artificial horizon. These waters probably owe theirpeculiar colour to a solution of carburetted hydrogen, to the luxuriance of the tropical vegetation, and to the quantity of plants and herbs on the ground over which they flow.—Humboldt’s Aspects of Nature, vol. i.
Where the river Shirhawti, between Bombay and Cape Comorin, falls into the Gulf of Arabia, it is about one-fourth of a mile in width, and in the rainy season some thirty feet in depth. This immense body of water rushes down a rocky slope 300 feet, at an angle of 45°, at the bottom of which it makes a perpendicular plunge of 850 feet into a black and dismal abyss, with a noise like the loudest thunder. The whole descent is therefore 1150 feet, or several times that of Niagara; but the volume of water in the latter is somewhat larger than in the former.
The friction of the wind combines with the tide in agitating the surface of the ocean, and, according to the theory of undulations, each produces its effect independently of the other. Wind, however, not only raises waves, but causes a transfer of superficial water also. Attraction between the particles of air and water, as well as the pressure of the atmosphere, brings its lower stratum into adhesive contact with the surface of the sea. If the motion of the wind be parallel to the surface, there will still be friction, but the water will be smooth as a mirror; but if it be inclined, in however small a degree, a ripple will appear. The friction raises a minute wave, whose elevation protects the water beyond it from the wind, which consequently impinges on the surface at a small angle: thus each impulse, combining with the other, produces an undulation which continually advances.—Mrs. Somerville’s Physical Geography.
Professor Bache states, as one of the effects of an earthquake at Simoda, on the island of Niphon, in Japan, that the harbour was first emptied of water, and then came in an enormous wave, which again receded and left the harbour dry. This occurred several times. The United-States self-acting tide-gauge at San Francisco, which records the rise of the tide upon cylinders turned by clocks, showed that at San Francisco, 4800 miles from the scene of the earthquake, the first wave arrived twelve hours and sixteen minutes after it had receded from the harbour of Simoda. It had travelled across the broad bosom of the Pacific Ocean at the rate of six miles and a half a minute, and arrived on the shores of California: the first wave being seven-tenths ofa foot in height, and lasting for about half an hour, followed by seven lesser waves, at intervals of half an hour each.
The velocity with which a wave travels depends on the depth of the ocean. The latest calculations for the Pacific Ocean give a depth of from 14,000 to 18,000 fathoms. It is remarkable how the estimates of the ocean’s depth have grown less. Laplace assumed it at ten miles, Whewell at 3·5, while the above estimate brings it down to two miles.
Mr. Findlay states, that the dynamic force exerted by Sea-Waves is greatest at the crest of the wave before it breaks; and its power in raising itself is measured by various facts. At Wasburg, in Norway, in 1820, it rose 400 feet; and on the coast of Cornwall, in 1843, 300 feet. The author shows that waves have sometimes raised a column of water equivalent to a pressure of from three to five tons the square foot. He also proves that the velocity of the waves depends on their length, and that waves of from 300 to 400 feet in length from crest to crest travel from twenty to twenty-seven and a half miles an hour. Waves travel great distances, and are often raised by distant hurricanes, having been felt simultaneously at St. Helena and Ascension, though 600 miles apart; and it is probable that ground-swells often originate at the Cape of Good Hope, 3000 miles distant. Dr. Scoresby found the travelling rate of the Atlantic waves to be 32·67 English statute miles per hour.
In the winter of 1856, a heavy ground-swell, brought on by five hours’ gale, scoured away in fourteen hours 3,900,000 tons of pebbles from the coast near Dover; but in three days, without any shift of wind, upwards of 3,000,000 tons were thrown back again. These figures are to a certain extent conjectural; but the quantities have been derived from careful measurement of the profile of the beach.
When one looks seaward from the shore, and sees a ship disappear in the horizon as she gains an offing on a voyage to India, or the Antipodes perhaps, the common idea is that she is bound over a trackless waste; and the chances of another ship sailing with the same destination the next day, or the next week, coming up and speaking with her on the “pathless ocean,” would to most minds seem slender indeed. Yet the truth is, the winds and the currents are now becoming so well understood, that the navigator, like the backwoodsman in the wilderness, is enabled literally to “blaze his way” across the ocean; not, indeed, upon trees, as in the wilderness, but upon the wings of the wind. The results of scientific inquiryhave so taught him how to use these invisible couriers, that they, with the calm belts of the air, serve as sign-boards to indicate to him the turnings and forks and crossings by the way.
Let a ship sail from New York to California, and the next week let a faster one follow; they will cross each other’s path many times, and are almost sure to see each other by the way, as in the voyage of two fine clipper-ships from New York to California. On the ninth day after theArcherhad sailed, theFlying Cloudput to sea. Both ships were running against time, but without reference to each other. TheArcher, with wind and current charts in hand, went blazing her way across the calms of Cancer, and along the new route down through the north-east trades to the equator; theCloudfollowed, crossing the equator upon the trail of Thomas of theArcher. Off Cape Horn she came up with him, spoke him, and handed him the latest New York dates. TheFlying Cloudfinally ranged ahead, made her adieus, and disappeared among the clouds that lowered upon the western horizon, being destined to reach her port a week or more in advance of her Cape Horn consort. Though sighting no land from the time of their separation until they gained the offing of San Francisco,—some six or eight thousand miles off,—the tracks of the two vessels were so nearly the same, that being projected upon the chart, they appear almost as one.This is the great course of the ocean: it is 15,000 miles in length. Some of the most glorious trials of speed and of prowess that the world ever witnessed among ships that “walk the waters” have taken place over it. Here the modern clipper-ship—the noblest work that has ever come from the hands of man—has been sent, guided by the lights of science, to contend with the elements, to outstrip steam, and astonish the world.—Maury.
Let a ship sail from New York to California, and the next week let a faster one follow; they will cross each other’s path many times, and are almost sure to see each other by the way, as in the voyage of two fine clipper-ships from New York to California. On the ninth day after theArcherhad sailed, theFlying Cloudput to sea. Both ships were running against time, but without reference to each other. TheArcher, with wind and current charts in hand, went blazing her way across the calms of Cancer, and along the new route down through the north-east trades to the equator; theCloudfollowed, crossing the equator upon the trail of Thomas of theArcher. Off Cape Horn she came up with him, spoke him, and handed him the latest New York dates. TheFlying Cloudfinally ranged ahead, made her adieus, and disappeared among the clouds that lowered upon the western horizon, being destined to reach her port a week or more in advance of her Cape Horn consort. Though sighting no land from the time of their separation until they gained the offing of San Francisco,—some six or eight thousand miles off,—the tracks of the two vessels were so nearly the same, that being projected upon the chart, they appear almost as one.
This is the great course of the ocean: it is 15,000 miles in length. Some of the most glorious trials of speed and of prowess that the world ever witnessed among ships that “walk the waters” have taken place over it. Here the modern clipper-ship—the noblest work that has ever come from the hands of man—has been sent, guided by the lights of science, to contend with the elements, to outstrip steam, and astonish the world.—Maury.
The great inducement to Mr. Babbage, some years since, to attempt the construction of a machine by which astronomical tables could be calculated and even printed by mechanical means, and with entire accuracy, was the errors in the requisite tables. Nineteen such errors, in point of fact, were discovered in an edition of Taylor’sLogarithmsprinted in 1796; some of which might have led to the most dangerous results in calculating a ship’s place. These nineteen errors (of which one only was an error of the press) were pointed out in theNautical Almanacfor 1832. In one of theseerrata, the seat of the error was stated to be in cosine of 14° 18′ 3″. Subsequent examination showed that there was an error of one second in this correction, and accordingly, in theNautical Almanacof the next year a new correction was necessary. But in making the new correction of one second, a new error was committed of ten degrees, making it still necessary, in some future edition of theNautical Almanac, to insert anerratumin anerratumof theerratain Taylor’sLogarithms.—Edinburgh Review, vol. 59.