PROBABLY many a Malthusian, on glancing at a terrestrial globe and observing the vast space which is allotted to the ocean, has testily exclaimed: "For what purpose does all this fluid exist? Here are we, poor mortals, with insatiable stomachs our numbers increasing with frightful rapidity-our acres incapable of expansion our agriculturists unable to make two blades of corn grow in the room originally required for one- our prospects, in fact, becoming so melancholy, that sooner or later people must make up their minds to eat little boys and girls in *The Physical Geography of the Sea. By M. F. MAURY, LL.D., U.S.N., Superintendent of the National Observatory. London: Sampson Low. New-York: Harpers. 1847. VOL. XLIX-No. 1. order to obtain food and keep the population within manageable bounds; yet, wanting all the accommodation we can get, not less than three fourths of the planet have been laid under water-some of its finest plains are swamped, and its most fertile valleys converted into liquid wastes !" Not so fast, however, good Mr. Malthusian! No one can explain why this particular proportion between the land and the ocean has been prescribed. It is precisely one of those points in the Divine arithmetic with which we are incompetent to deal. But sufficient may be inferred from the exquisite working of the great physical machinery of creation to satisfy us that he who weigheth the waters in the 1 hollow of his hand, and who fixeth bounds | whether its atmosphere could be moderately refreshed and its meadows adequately irrigated, if the surface of the great nursery of vapor were seriously curtailed? for the sea that it shall not pass, has adjusted the fluid and solid surfaces of our globe with as much care as he has mixed the chemical constituents of the atmosphere, or settled the relative numbers of the two sexes. Grant that our mournful friend, who looks with such a jealous eye upon those liquid expanses, could brush them from their beds, and convert the whole earth into dry ground, what would be the result? Why, the world would wither at once with drought. The fair face of nature, still as fresh and blooming as in her infant days, would contract in ghastly wrinkles, and the comeliest landscapes grow cadaverous with premature age. our maritime operations; for how could vessels float in a thin liquid like naphtha, or cruise in a heavy one like quicksilver, or plow their way through a viscid one like tar or treacle? Ransack the whole list of existing fluids, and not another could be found to supply the place and perform the multifarious duties of water. Such, then, being the primary objeot of the ocean, see how beautifully its composition qualifies it for this end. What other fluid could be substituted with the smallest success? Would any of our acids answer the purpose required? Clouds dropping oil of vitriol, or showers consisting of muriatic acid, would soon burn up all vegetation and blister every landscape on the globe. With Atlantics of turpentine or Pacifics of train oil, not an herb would grow for the nourishment of cattle, nor a tree for the use of the carAs matters now stand, have we not penter. For many reasons, too, a change numerous deserts dispersed over the sur- in the character of the ocean fluid would face of the globe-spots of barrenness be highly detrimental to the interests of and death, where the pulse of the planet man. Considering the sea simply as a can not be felt, and where its life-blood highway for our ships, any alteration in apparently ceases to circulate? These its specific gravity, or in the cohesive reseem to show that the earth is not over-lationship of its particles, would affect all done with water, and that, spite of the vast acreage of the ocean, there are tracts of land which its vapor can not reach, and certainly can not drench. When a wind, charged with moisture, sets out on its travels over a continent, it gradually deposits its freight as it proceeds; and should it encounter a range of tall mountains, the cold at their chilly tops extracts the hu- But the liquid which fills the vast ocean midity in the shape of snow, leaving the tanks is not pure. It contains, in general, breeze to pursue its course beggared of from three to three and a half per cent the fatness which the soil demands. of saline ingredients. To these, latterly, There are countries where showers rarely philosophers have begun to assign very fall, because the intervening regions steal considerable importance in the economy all the vapor which the prevailing winds of the great deep. They are not chance obtain from the ocean exchequer. Peru items in its waters, but elements of prois notoriously in this predicament. Jup- found significance, seeing that they reguiter Pluvius is unknown in that locality. late its issues of vapor and guide its The south-east trades, which at first movements from the equator to the poles. sprinkle the shores of Brazil, and then The saline materials consist of chloride of feed the large streams of South-America, sodium, cloride of magnesium, sulphate afterwards rush up the slopes of the of lime, sulphate of magnesia, and other Andes in a state of comparative poverty, mineral compounds, the first of these preand finally tumble over into the land of ponderating to such a degree, that for the Incas in a condition of real hygromet- most purposes we are content to regard ric insolvency. Upon similar grounds the the ocean simply as a reservoir of common existence of Saharas in Africa, Asia, Aus- salt. Nor should we forget to remark, tralia, and North-America may be ex- en passant, for it is certainly worthy of plained. Looking, indeed, at these barren being ranked amongst the noticeable harpatches, and assuming that other physical monies of nature-that the substance circumstances continued the same, we which is most largely diffused through the may well ask whether the world could be sea is precisely the condiment which kept in working order-whether its rivers man's instinct has taught him to employ and lakes could be sufficiently supplied-most extensively on land. The quantity varies according to circumstances and locality. It is less in inland seas, for example, than in the main ocean, because the rush of river water into these basins serves to keep them in a fresher condition, particularly if the outlets are few and contracted. Exception, however, must be made in favor of the Mediterranean, but the superior temperature of that splendid sheet, and consequently the greater concentration which is given to its brine, will explain the result. It is less, again, towards the poles, where snow and ice are such chronic phenomena; and the same observation applies to those humid portions of the tropics where umbrellas and mackintosh capes are peculiarly required. Humboldt ascertained that the charge of salt was greatest between the fifteenth and the twenty-fifth degrees of north and south latitude. Forchhammer discovered that the ocean became softer in this particular as land was approached -a circumstance, indeed, which we might expect, considering that the river gods are always pouring large contributions into the main. Marcet concluded that the seas of the southern hemisphere are fresher than those of the northern, and that if necessity compelled you to choose between the Atlantic and Pacific in regard to their potable qualities, you would find the latter much more to your taste than the former. There are certain landlocked expanses which receive as much fresh liquid as the streams will supply, but make it a point never to disgorge; and consequently-true emblems of niggardly, selfish souls-their waters become bitter and unblessed. The saline elements are left to accumulate as the vapor is carried off by the winds; and thus we have surly and inhospitable seas like the Aral and Caspian, or that still more ill-omened mere, the Lake Asphaltites. If, however, the quantity of these ingredients varies, their quality and relative proportions are singularly uniform. Bearing in mind that the soluble matters of the land are constantly washed into the ocean, and that each river carries its own particular contingent to the deep, we might expect that a more mongrel fluid would result. But every where the water seems to yield the same species of salts when dissected by the chemist's art. Their origin is still a question of much mystery. Whether the existing ocean was produced in a brackish condition, or has gradually acquired its present charge, is a point which may be yet open to discussion; but there are many reasons which appear to intimate that what it is now, such it has been throughout the whole historic period at least. We can scarcely suppose that the entire amount of salt has been wrung out of the land, for, taking the average depth of the waters at two miles only, it is calculated that there is enough chloride of sodium in the sea to cover a continent measuring seven millions of square miles to the depth of one mile. Shafhäut computed that the mineral matter suspended in the ocean was equal to double the Himalayas in bulk. Yet this mass is diffused throughout the abyss without increasing its volume, for soluble substances pack into the interstices of fluids, as odds and ends of luggage do into the crevices of a carpet-bag until the mysterious point of saturation is reached. And what is the use of so much salt? The answer to this question has generally been that it is intended to preserve the Great Profound from putrefaction. The sea is a huge pickle. But this explanation is by no means satisfactory. For, in the first place, stagnant sea-water is subject to corruption, and when voyagers have been caught in a calm and forced to lie idle on the ocean for weeks together, they have seen all sorts of "slimy things" crawl forth from the abyss, or, as Sir Richard Hawkins relates, "the sea was so replenished with several sorts of gellyes, and forms of serpents, adders, and snakes as seemed wonderfull; some greene, some blacke, some yellow, some white, some of divers colours, and many of them had life. So much so," continues that ancient mariner, "that a man could hardly draw a bucket of water clear of corruption." Salt, therefore, will not prevent decomposition, if the waves are permitted to sleep. Further, provision appears to be made in other ways for the removal of the decaying matter which may be poured into the great marine cesspools. To say nothing of chemical operations, the sea is peopled by crowds of microscopic animals, which banquet in a great measure upon the refuse organisms of the land; and these become food in their turn for the bulkier denizens of the deep. Whole legions of infusoria go down into the caverns of the whale at a single gulp. Patches of white or colored water, stretch ing as far as the eye could reach, and thronged to the depth of more than a thousand feet with animalcules, have been traversed by navigators in various parts of the world. In the Indian Ocean especially they hang like red, green, brown, or crimson clouds upon the surface of the main. Captain Kingman passed through a shoal of gelatinous creatures extending twenty-three miles in length, breadth unknown, and whitening the sea so completely that it looked like a plain covered with snow. When a tub was filled with the water, little luminous particles were seen dancing to and fro, and the vessel appeared to be alive with tiny worms and insects. In the Northern Seas, the medusæ are so prodigiously developed, and at the same time so densely packed, that, according to Scoresby, it would require 84,000 persons, calculating as if for their lives or perhaps, more stimulating still, as if for their fortunes-and continuing their labors from the Creation up to the present period, to reckon up the quantity contained in two square miles alone. To these, and similar little scavengers, therefore, is probably committed the task of ridding the ocean of much of the decomposing matter which is brushed from the land, and which might otherwise dispose it to putrescence. Other and equally interesting functions have latterly been ascribed to the salts of the sea. Professor Chapman, of Toronto, has ingeniously suggested that their purpose is to regulate the rate of evaporation, and thus keep those two old champions, Moist and Dry, on terms of tolerable amity. Water charged with salt will give off vapor more slowly than water when perfectly pure. Balance two dishes in a pair of scales, fill the one with brine, the other with liquid from the rain-tub, and the latter will beat the former hollow in the rate at which its contents exhale; indeed, in proportion as the saline solution becomes more and more concentrated will the rise of the water in an aëriform shape appear to be retarded. This, in fact, is just what we might expect; for the salt will naturally cling to the fluid with greater tenacity the less it has to lose. Other circumstances, therefore, being the same such, for example, as the fervor of the sun's rays, the pressure of the atmosphere, the amount of humidity already in the air -it follows that whenever the quantity of salt in the ocean is relatively diminished by the influx of fresh water in any particular locality, evaporation advances with greater volubility; whereas, if that quan tity be augmented, it proceeds at a tardier rate. If this view be correct-and we fancy the propounder has seized upon one of the secrets of the deep-what a splendid automaton the ocean becomes ! Like the governor of a steam-engine, it contracts its own issues of vapor when the sun begins to fall upon its waters with unwarrantable freedom, and increases them when the land has been unduly drained, or the moisture in the atmosphere inordinately precipitated. As the winds whistle over Neptune's domain he seems to say: "I feel that I am growing too saline to-day; you can't, therefore, want much humidity on shore; send me back the surplus either in river or in shower, and when the accounts between sea and land are balanced, you shall receive your usual freight with pleasure. Unless our books are duly squared, and sun and ocean, and wind and stream settle their mutual transactions with punctuality, it would soon be all over with the world." The great business of these saline matters, however, according to Lieutenant Maury, whose ocean studies preeminently entitle him to the appellation of the Philosopher of the Sea, is to keep the abyss of waters in constant motion. To him these humble ingredients are vast dynamie powers. Sea-water is heavier than river in the proportion of 1028 to 1010. A man feels more buoyant whilst swimming off Ramsgate than he does when bathing in the fish-pond at home. Rain-water will float on brackish water; and sailors sometimes take advantage of this fact, as was the case in the expedition of the Adventure and Beagle, where the crews, on one occasion, obtained a potable fluid from the surface of the ocean by inserting the hose of their pumps into the supernatant liquid, whereas, had they gone a few inches deep, they would have drawn up a beverage fit only for naiads and mermen. Now, suppose that evaporation is proceeding rapidly from any tropical tract in the Atlantic or Pacific; of course the consequence will be a lowering of the level, and water must necessarily press in from all sides to fill up the great dimple. Since, however, the vapor which is exhaled is fresh, the fluid left behind must increase in gravity proportionately to the legacy of salt it has just received. What follows? A flow of liquid being determined to the excavat-, this question by referring to those armies ed spot, a current of denser water will of creatures which are employed in exalso be established in a contrary direction. tracting saline materials from the water, For as the fresh water scooped out from some for their shells, some for their skelthe sea in the region of evaporation is etons, some for their habitations. Beds only borrowed for a time, and must de- of marl, banks of shell, and deposits of scend in some other spot, which may be infusoria have been formed in the ancient called the region of precipitation, it will oceans, and the same processes are on foot lessen the specific gravity of the upper in our existing seas. The coralline archistratum of the ocean where it alights, and tects are ever busy in the warmer waters then draining off towards the original of our globe, and huge masses of masonry point of disturbance, the equilibrium must are slowly rising, compared with which be restored by the transfer of the weigh- our human erections are mere card-houses. tier, because saliner, liquid to the compen- To these animals must evidently belong sating parts. Thus, speaking generally, the power of extracting the carbonate of the sea is kept in wholesome excitement lime and other mineral substances they by a wonderful system of circulation, in may require from the transparent wave. which the chloride of sodium and other ingredients figure as important ministering forces. "We have a surface-current of saltish water from the poles towards the equator, and an under-current of water, salter and heavier, from the equator to the poles. This under-current supplies in a great measure the salt which the upper-current, freighted with fresh water from the clouds and rivers, carries back." How beautifully are the equities of the great abyss maintained! Further, it will be seen that in an ocean of salt water a system of vertical circulation must prevail which could not obtain in an ocean of fresh; for, as the surface layer is robbed by evaporation, and its density is consequently augmented, it must sink, whilst the less briny layer beneath will ascend. In the fact, therefore, that a drop of water overdosed with salt will give place to the lighter molecule beneath, we discover another exquisite provision for a perpetual "turn-over" in the liquid mass. But this is not all; the salts not only serve to keep the pulses of the ocean in play, but they are essential to the existence of myriads of living things. With out adverting to the fact that the finny inhabitants of the deep would mostly perish in a fresh-water medium, let us point to the peculiar relationship which subsists between the saline ingredients and one class of marine laborers. Why does not the ocean grow salter every day? Why does it not threaten to become as briny as the Dead Sea and other imprisoned sheets? There must be some means by which the perpetual additions from the shores are neutralized, or at any rate kept in subjection. Maury solves What amount is thus quarried from the waters it would be impossible to surmise; but, considering the number of the workmen, and the magnitude of the piles they have completed, their influence must tell with some power upon the composition of the sea. That it constitutes the sole agency by which the saline additions are held in check can not be admitted, because some of these elements only are required for the purposes of the little operatives. But it is singular to observe how each pigmy mason assists in the great task, which must on no account be neglected, of keeping the waters in ceaseless circulation. Down in the deep the coral insect is at work on the huge edifice which he and his companions have been bidden by instinct to construct. He wants stone: he obtains it from the water around him. How, no one can say: it is one of the mysteries of vital chemistry we are unable to explain. But in extracting the material he requires from any particular drop, that drop necessarily becomes lighter than those above, and therefore ascends to the surface; another, of course, descends to take its place, and suffer a similar loss in turn. Thus, rising and falling like the corves in a pit, the watery atoms are kept in action by the submarine artificers; and though the depth at which they toil is limited, being confined to some thirty fathoms, yet within that range they move the whole mass of fluid overhead, though apparently unmoved and unmoving themselves. And, as if to show that all the powers of nature, whether great or small, play into each other's hands, let it be observed that the sun and winds seem to take thought for the builders of these sunken piles. Do they not, by abstract |