Part 27

That huge mass of waters impregnated with salt, which encompasses all parts of the globe, and by the means of which, in the present improved state of navigation, an easy intercourse subsists between the most distant nations, is denominated the ocean, and has three grand divisions assigned to it. First, that vast expanse of water which lies to the westward of the northern and southern continents of America, and by which those continents are divided from Asia. On account of the uniform and temperate gales which sweep its surface within the tropics, it is named the Pacific ocean; and has again been distinguished into the northern and southern Pacific, (the equator being considered as the dividing line,) and the Southern ocean, or South sea, being consequently that part of the general assemblage of waters which is contained between the fortieth degree of south latitude and the south pole. Its general width is estimated at about ten thousand miles. Secondly, the Atlantic ocean, which divides Europe and Africa from the two American continents, and has a general width of about three thousand miles; while the waters which occupy the polar regions are named the Northern sea. And, lastly, the Indian ocean, which extends from the eastern shores of Africa along the southern coasts of Asia, and has the same general width with the preceding one.

Among the chief of those less expansive sheets of water, properly called seas, may be mentioned the Baltic, the Mediterranean sea, and the Black and Red seas. The Caspian sea, being entirely encompassed by land, might, with more propriety, have been styled a lake; but as its water possesses the quality of saltness, it is ranked among the seas. It is, notwithstanding, certain that Lake Superior has a still greater circumference, extending around its shores at least fourteen hundred miles, while the extent of the Caspian does not exceed twelve hundred.

Of the origin of this division into different seas, and seas of different depths, little is known; but it is highly probable that many of the larger excavations and partitions now met with, have existed, without much change as to their extent, from the creation. Others have undoubtedly been the result of that conflict which is perpetually taking place between the elements of land and water, and which has, for the greater part, given rise to islands, isthmuses and peninsulas; while subterraneous volcanoes, and the truly surprising and indefatigable exertions of coral, madrepores, tubipores, and other restless and multitudinous zoöphytes, have laid, and are daily laying, the foundation of new islands and continents in the middle of the widest and deepest seas.

The quantity of water in the ocean, not only remains constantly the same, but, notwithstanding its most violent and incessant motion, continues stable within certain limits. This, however, can not be inferred from observation; for, although in the almost infinite variety of disturbances to which the ocean is liable, from the action of irregular causes, it may appear to return to its former state of equilibrium, still it may be apprehended that some extraordinary cause may communicate to it a shock, which, though inconsiderable at first, may augment continually, and elevate it above the highest mountains. It is, therefore, interesting to investigate the conditions which are necessary for the absolute stability of the ocean. This has been effected by the celebrated Laplace, who has demonstrated that the equilibrium of the ocean _must_ be stable, if the density be _less_ than the mean density of the earth, which is known to be the case. He has likewise determined, by means of his refined analysis, that this stability would cease to exist, if the mean density of the sea _were to exceed_ that of the earth; so that the stability of the equilibrium of the ocean, and the excess of the density of the terrestrial globe above that of the waters which cover it, are reciprocally connected with each other, and indicate infinite wisdom and contrivance in such an adjustment.

SALTNESS OF THE SEA.

Of the various phenomena of the sea, that of its _saltness_ is one of the most obvious. No questions concerning the natural history of our globe have been discussed with more attention, or decided with less satisfaction, than that concerning its primary cause, which had perplexed the philosophers before the time of Aristotle, and surpassed even the great genius of that profound inquirer into natural causes. Kircher, after having consulted not less than thirty-three authors on this subject, could not help remarking, that the fluctuations of the ocean itself were scarcely more various than the opinions concerning the origin of its saline impregnation.

This question does not seem capable of admitting an illustration from experiment; at least, not from any experiments hitherto made for that purpose: it is, therefore, not surprising, that it remains nearly as problematical in the present age, as it has been in any of the preceding. Had observations been made three or four centuries ago, to ascertain the saltness of the sea, then, at any particular time and place, we might now, by making similar observations at the same place, in the same season, have been able to know, whether the saltness, at that particular place, was increasing or decreasing, or an invariable quantity. This kind and degree of knowledge would have served as a clue to direct us to a full investigation of this matter in general. It is to be regretted, however, that observations of this nature have not, in former days, been made with any degree of precision.

One of the principal opinions maintained on this subject by modern philosophers, and more particularly supported by Halley, is, that since river-water, in almost every part of the globe, is impregnated in a greater or less degree by sea-salt, the sea must have gradually acquired its present quantity of salt from the long continued influx of rivers. The water which is carried into the sea by these rivers, is again separated from it by evaporation, and being dispersed over the atmosphere by winds, soon descends in rain or vapor upon the surface of the earth, whence it hastens to pour into the bosom of the ocean the fresh tribute of salt it has collected in its inland progress. Thus the salt conveyed into the sea not being a volatile substance, nor performing an incessant circulation, must be a perpetually increasing quantity; and sufficient time, it is contended, has elapsed since the creation, for the sea to acquire, from this source, its present quantity of salt.

This opinion has been successfully combated; and it is denied that freshwater rivers could, in the course of thousands or even millions of years, have produced saltness in the sea. If this were the case, every sea, or great body of water, which receives rivers, must have been salt, and have possessed a degree of saltness in proportion to the quantity of water which these rivers discharge. But so far is this from being true, that the Palus Mæotis, and our great American lakes, do not contain salt water, but fresh. It may indeed be objected, that the quantity of salt which rivers carry along with them, and deposit in the sea, must depend on the nature of the soil through which they flow, which may in some places not contain any salt; and that this is the reason why the great lakes in America and the Palus Mæotis are fresh. But to this opinion, which is merely hypothetical, there are insurmountable objections. It is a curious fact, that the saltness of the sea is greatest under the equator, and diminishes gradually toward the poles; but it can not therefore be assumed that the earth contains more salt in the tropical regions than in the temperate zones, and more in these again than in the frigid zones. On the other hand, if it be allowed that the sea receives its saltness from the rivers, it must be equally salt, or nearly so, in every part of the earth; since, according to a simple and well-known principle in chemistry, _when any substance is dissolved in water with the assistance of agitation, at whatever part of the water it is introduced, it will be equally diffused through the whole liquid_. Now, though it were true that a greater quantity of salt should have been introduced into the sea under the equator, than toward the poles, from the constant agitation occasioned by the wind and tide, the salt must have soon pervaded the whole mass of water. Neither is this greater proportion of saltness owing to a superior degree of heat, since it is an established principle in chemistry, that cold water and hot water dissolve nearly the same proportion of salt.

The saltness of the sea has also been ascribed to the solution of subterraneous mines of salt, that are supposed to abound in the bottom of the sea, and along its shores. But this hypothesis can not be supported. If the sea were constantly dissolving salt, it would soon become saturated; for it can not be said that it is deprived of any portion of its salt by evaporation, since rain-water is fresh. If the sea were to become saturated, neither fishes nor vegetables could live in it. It may hence be inferred that the saltness of the sea can not be accounted for by secondary causes, and _that it has been salt since the beginning of time_. It is indeed impossible to suppose that the waters of the sea were at any time fresh since the formation of fishes and sea-plants; neither will they live in water which is fresh. It may hence be concluded that the saltness of the sea has, with some few exceptions, perhaps arising from mines of rock-salt dispersed near its shores, been nearly the same in all ages. This hypothesis, which is the simplest, and is involved in the fewest difficulties, best explains the various phenomena dependent on the saltness of the sea.

Although this saline property may be one of the causes by which the waters of the sea are preserved from putridity, still it can not be considered as the principal cause. The ocean has, like rivers, its currents, by which its contents are circulated round the globe; and these may be said to be the great agents which keep it sweet and wholesome. A very enlightened navigator, Sir John Hawkins, speaks of a calm, in which the sea, having continued for some time without motion, assumed a very formidable aspect. “Were it not,” he observes, “for the moving of the sea by the force of winds, tides and currents, it would corrupt all the world. The experiment of this I saw in the year 1590, lying with a fleet about the islands of the Azores, almost six months, the greater part of which time we were becalmed. Upon which, all the sea became so replenished with various sorts of gellies, and forms of serpents, adders and snakes, as seemed wonderful; some green, some black, some yellow, some white, some of divers colors, and many of them had life; and some there were a yard and a half, and two yards long; which, had I not seen, I could hardly have believed. And hereof are witnesses all the companies of the ships which were then present; so that hardly a man could draw a bucket of water clear of some corruption. In which voyage, toward the end thereof, many of every ship fell sick, and began to die apace. But the speedy passage into our country, was a remedy to the diseased, and a preservative to those who were not touched.”

CONGELATION OF SEA-WATER.

Although the assertion that salt water never freezes, has been contradicted by repeated experience, it is still certain that it requires a much greater degree of cold to produce its congelation, than fresh water. It is, therefore, one of the greatest blessings which we derive from this element, that when we find all the stores of nature locked up to us on the land, the sea is, with few exceptions, ever open to our necessities. It is well known that at particular seasons, the mouth of the river St. Lawrence, the entrance into the Baltic sea, &c., are so much frozen over as to be impassable by ships; while the vast mountains and fields of ice in the polar regions, have for ages past been insurmountable obstructions to the daring researches of modern navigators. These exceptions, however, will appear of comparatively trifling importance to navigation, when the number of ports which are, in almost every region, open at all seasons of the year, are considered; and this facility of intercourse would certainly not have been afforded, if sea-water had admitted of as easy a congelation as that of water not impregnated with salt.

On the origin of ice in the frozen seas, different opinions have been entertained. The authority of Capt. Cook and Lord Mulgrave, has been cited by Bishop Watson, to show that good fresh water may be procured from ice found in those seas; but he observes that, notwithstanding the testimonies of these very able navigators, it may still be doubted whether the ice from which the water was obtained, had been formed in the sea, and, consequently, whether sea-water itself would, when frozen, yield fresh water. He thinks it probable that the ice had either been formed at the mouths of large fresh-water rivers, and had thence, by tides or torrents been drifted into the sea, or that it had been broken by its own weight, from the immense cliffs of ice and frozen snow which, in countries where there are few rivers, are found in high latitudes to project a great way into the sea. An early navigator, Fotherbye, in the relation of his voyage toward the south pole, in 1614, considers snow to be the original cause of the ice found at sea, he himself having observed it to lie an inch thick on the surface; and Captain Cook, from his own observation in the South sea, was disposed to think that the vast floats of ice he met with in the spring, were formed from the congelation of snow. It is certain that the snow which falls upon the surface of the sea, being in a solid state, and, bulk for bulk, lighter than sea-water, will not readily combine with it, but may, by a due degree of cold in the atmosphere, be speedily converted into a layer of ice. The upper layer of this first surface of ice being elevated above the surface of the sea, will receive all the fresh water which falls from the atmosphere in the form of snow, sleet, rain or dew, by the successive congelation of which, the largest fields of ice may at length be formed.

It is a matter of little consequence to a navigator, whence the ice which supplies him with fresh water is produced. Leaving, therefore, these hypotheses relative to the formation of ice in frozen seas, it should be observed that the question, whether congealed sea-water will, when thawed, yield fresh water, has been satisfactorily decided by experiments made with every suitable attention. A quantity of sea-water having been taken up off the English coast, was exposed to a freezing atmosphere, and afforded an ice perfectly free from any taste of salt; and it has likewise been found, that not only sea-water, but water containing double the proportion of salt commonly found in our sea-water, and more than is contained in the sea-water of any climate, may be frozen by the cold prevailing in our atmosphere.

[Illustration: ICEBERGS, OR ICE-ISLANDS.]

ICE-ISLANDS.

Ice-islands, or icebergs, as they are commonly called, is the name given by seamen to the huge, solid masses of ice which abound in the sea near or within the polar circles, and which often float down nearer to the equator, till they are gradually dissolved by the increasing warmth of the air and water. The cut gives a view of them as seen by Dr. Scoresby, who counted five hundred of them between latitude sixty-nine degrees and seventy degrees north, which were from one hundred to two hundred feet high, and from a few yards to a mile in circumference. Many of these fluctuating islands are met with on the coasts of Spitzbergen, to the great danger of the vessels employed in the Greenland fishery. In the midst of these tremendous masses, navigators have been arrested and frozen to death. In this manner the brave Sir Hugh Willoughby perished, with all his crew, in 1553; and in the year 1773, Lord Mulgrave, after every effort which the most accomplished seaman could make, to reach the termination of his voyage, was caught in the ice, and nearly experienced the same unhappy fate. The scene he describes, divested of the horrors attendant on the eventful expectation of change, was most beautiful and picturesque. Two large ships becalmed in a vast basin, surrounded on all sides by ice-islands of various forms; the weather clear; the sun gilding the circumambient ice, which was smooth, low, even, and covered with snow, except where pools of water, on a portion of the surface, shot forth new icy crystals, and on the smooth surface of the comparatively small space of sea in which they were hemmed. Such is the picture drawn by our navigator, amid the perils by which lie was surrounded.

After fruitless attempts to force their way through the fields of ice, the limits of these became at length so contracted, that the ships were immovably fixed. The smooth extent of surface was soon lost; the pressure of the pieces of ice, by the violence of the swell, caused them to pack; and fragment rose upon fragment, until they were in many places higher than the main-yard. The movements of the ships were tremendous and involuntary, in conjunction with the surrounding ice, actuated by the currents. The water having shoaled to fourteen fathoms, great apprehensions were entertained, as the grounding of the ice, or of the ships, would have been equally fatal: the force of the ice might have crushed them to atoms, or have lifted them out of the water, and have overset them; or, again, have left them suspended on the summits of the pieces of ice, at a tremendous hight, exposed to the fury of the winds, or to the risk of being dashed to pieces by the failure of their frozen dock. An attempt was made to cut a passage through the ice; but after a perseverance truly worthy of Britons, it proved ineffectual. The commander, who was at all times master of himself, directed the boats to be made ready to be hauled over the ice, till they should reach navigable water, proposing in them to make the voyage to England; but after they had thus been drawn over the ice, for three progressive days, a wind having sprung up, the ice separated sufficiently to yield to the pressure of the ships in full sail. After having labored against the resisting fields of ice, they at length reached the harbor of Smeerinberg, at the west end of Spitzbergen.

The vast islands of floating ice which abound in the high southern latitudes, are a proof that they are visited by a much severer degree of cold than equal latitudes toward the north pole. Captain Cook, in his second voyage, fell in with one of these islands in latitude fifty degrees, forty minutes, south. It was about fifty feet high, and half a mile in circuit, being flat on the top, while its sides, against which the sea broke exceedingly high, rose in a perpendicular direction. In the afternoon of the same day, the tenth of December, 1773, he fell in with another large cubical mass of ice, about two thousand feet in length, four hundred feet in breadth, and in hight two hundred feet. Mr. Foster, the naturalist of the voyage, remarks that, according to the experiments of Boyle and Marian, the volume of ice is to that of sea-water as ten to nine: consequently, by the known rules of hydrostatics, the volume of ice which rises above the surface of the water, is to that which sinks below it as one to nine. Supposing, therefore, this mass of ice to have been of a regular figure, its depth under water must have been eighteen hundred feet, and its whole hight, twenty hundred feet: estimating its length, as above, at twenty hundred feet, and its breadth at four hundred feet, the entire mass must have contained sixteen hundred millions of cubic feet of ice.

Two days after, several other ice-islands were seen, some of them nearly two miles in circuit, and six hundred feet high; and yet such was the force of the waves, that the sea broke quite over them. They exhibited for a few moments a view very pleasing to the eye; but a sense of danger soon filled the mind with horror; for had the ship struck against the weather-side of one of these islands, when the sea ran high, she must in an instant have been dashed to pieces. The route to the southward was afterward impeded by an immense field of low ice, the termination of which could not be seen, either to the east, west or south. In different parts of this field were islands, or hills of ice, like those which had before been found floating in the sea.

At length these ice-islands became as familiar to those on board as the clouds and the sea. Whenever a strong reflection of white was seen on the skirts of the sky, near the horizon, then ice was sure to be encountered; notwithstanding which, that substance itself was not entirely white, but often tinged, especially near the surface of the sea, with a most beautiful sapphirine, or rather berylline blue, evidently reflected from the water. This blue color sometimes appeared twenty or thirty feet above the surface, and was probably produced by

## particles of sea-water which had been dashed against the mass in

tempestuous weather, and had penetrated into its interstices. In the evening, the sun setting just behind one of these masses, tinged its edges with gold, and reflected on the entire mass a beautiful suffusion of purple. In the larger masses, were frequently observed shades or casts of white, lying above each other in strata, sometimes of six inches, and at other times of a foot in hight. This appearance seemed to confirm the opinion entertained relative to the increase and accumulation of such huge masses of ice, by heavy falls of snow at different intervals; for snow being of various kinds, small-grained, large-grained, in light feathery locks, &c., the various degrees of its compactness may account for the different colors of the strata.