Physical Geography Of The Sea 1855/12
CHAPTER XII. — THE BASIN OF THE ATLANTIC.
Plate XI., § 439. — Height of Chimborazo above the Bottom of the Sea, 440. — Orography of Oceanic Basins, 441. — The deepest Place in the Atlantic, 442. — THE BOTTOM OF THE ATLANTIC: The Utility of Deep-sea Soundings, 445. — A Telegraphic Plateau across the Atlantic, 446. — Specimens from it, 447. — A microscopic Examination of them, 448. — Brooke’s Deep-sea Lead presents the Sea in a new Light, 453. — The Agents at work upon the Bottom of the Sea, 454. — How the Ocean is prevented from growing salter, 458. — Knowledge of our Planet to be derived from the Bottom of the Sea, 460.
439. The Basin Of The Atlantic, according to the deep-sea soundings made by the American Navy, in the manner described in the foregoing chapter, is shown on Plate XI. This plate refers chiefly to that part of the Atlantic which is included within our hemisphere.
440. 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 reached 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 rugged, grand, 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 pearl and inestimable stones, which, in the poet’s eye, lie scattered in the bottom of the sea, making it hideous with sights of ugly death.
441. To measure the elevation of the mountain-top above the sea, and to lay down upon our maps the mountain ranges of the earth, is regarded in geography as an important thing, and rightly so. Equally important is it, in bringing the physical geography of the sea regularly within the domains of science, to present its orography, by mapping out the bottom of the ocean so as to show the depressions of the solid parts of the earth’s crust there below the sea-level.
442. Plate XI. presents the second attempt at such a map. It relates exclusively to the bottom of that part of the Atlantic Ocean which lies north of 10° south. It is stippled with four shades; the darkest (that which is nearest the shore-line) shows where the water is less than six thousand feet deep; the next, where it is less than twelve thousand feet; the third, where it is less than eighteen thousand; and the fourth, or lightest, where it is not over twenty-four thousand feet deep. The blank space south of Nova Scotia and the Grand Banks includes a district within which very deep water has been reported, but from casts of the deep-sea lead which upon discussion do not appear satisfactory. The deepest part of the North Atlantic (§ 438) is probably somewhere between the Bermudas and the Grand Banks, but how deep it may be yet remains for the cannon ball and sounding-twine to determine.
443. The waters of the Gulf of Mexico are held in a basin about a mile deep in the deepest part.
444. The Bottom Of The Atlantic, or its depressions below the sea-level, are given, perhaps, on this plate with as much accuracy as the best geographers have been enabled to show on a map the elevations above the sea-level of the interior either of Africa or Australia.
445. “What is to be the use of these deep-sea soundings?” is a question that often occurs; and it is as difficult to be answered in categorical terms as Franklin’s question, “What is the use of a new-born babe?” Every physical fact, every expression of nature, every feature of the earth, the work of any and all of those agents which make the face of the world what it is, and as we see it, is interesting and instructive. Until we get hold of a group of physical facts, we do not know what practical bearings they may have, though right-minded men know that they contain many precious jewels, which science or the expert hand of philosophy will not fail to bring out, polished, and bright, and beautifully adapted to man’s purposes. Already we are obtaining practical answers to this question as to the use of deep-sea soundings; for as soon as they were announced to the public, they forthwith assumed a practical bearing in the minds of men with regard to the question of a submarine telegraph across the Atlantic.
446. There is at the bottom of this sea, between Cape Race in Newfoundland and Cape Clear in Ireland, a remarkable steppe, which is already known as the telegraphic plateau. A company is now engaged with the project of a submarine telegraph across the Atlantic. It is proposed to carry the wires along this plateau from the eastern shores of Newfoundland to the western shores of Ireland. The great circle distance between these two shorelines is one thousand six hundred miles, and the sea along the route is probably nowhere more than ten thousand feet deep. This company, it is understood, consists of men of enterprise and wealth, who, should the inquiries that they are now making prove satisfactory, are prepared to undertake the establishment forth-with of a submarine telegraph across the Atlantic.
447. It was upon this plateau that Lt. John Mercer Brooke’s sounding apparatus (§ 437) brought up its first trophies from the bottom of the sea. These specimens Lieutenant Berryman and his officers judged to be clay; but as ordered they took the precaution to label them, carefully to preserve them, and, on their return to the United States, to send them to the proper bureau. They were divided: a part was sent for examination to Professor Ehrenberg, of Berlin, and a part to Professor Bailey, of West Point — eminent microscopists both. I have not heard from the former, but the latter, in November, 1853, thus responded:
448. “I am greatly obliged to you for the deep soundings you sent me last week, and I have looked at them with great interest. They are exactly what I have wanted to get hold of. The bottom of the ocean at the depth of more than two miles I hardly hoped ever to have a chance of examining; yet, thanks to Brooke’s contrivance, we have it clean and free from grease, so that it can at once be put under the microscope. I was greatly delighted to find that all these deep soundings are filled with microscopic shells; not a particle of sand or gravel exists in them. They are chiefly made up of perfect little calcareous shells (Foraminiferae) and contain, also, a small number of silicious shells (Diatomacæ).
“It is not probable that these animals lived at the depths where these shells are found, but I rather think that they inhabit the waters near the surface; and when they die, their shells settle to the bottom. With reference to this point, I shall be very glad to examine bottles of water from various depths which were brought home by the Dolphin, and any similar materials, either ‘bottom,’ or water from other localities. I shall study them carefully... The results already obtained are of very great interest, and have many important bearings on geology and zoology....
“I hope you will induce as many as possible to collect soundings with Brooke’s lead, in all parts of the world, so that we can map out the animalculæ as you have the whales. Get your whalers also to collect mud from pancake ice, &c., in the Polar regions: this is always full of interesting microscopic forms.”
449. These little mites of shells seem to form but a slender clew indeed by which the chambers of the deep are to be threaded, and mysteries of the ocean revealed; yet the results are suggestive; in right hands and to right minds, they are guides to both light and knowledge. The first noticeable thing the microscope gives of these specimens is, that all of them are of the animal, not one of the mineral kingdom.
450. 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, the greater the space occupied by his remains. Though not invariably the case, yet this rule, to a certain extent, is true, and will, therefore, answer our present purposes, which are simply those of illustration. Take the elephant and his remains, or 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 grave-yard that would hold the coral-lines is larger than the grave-yard that would hold the elephants.
451. We notice another practical bearing in this group of physical facts that Brooke’s apparatus fished up from the bottom of the deep sea. Bailey, with his microscope (§ 448), could not detect a single particle of sand or gravel among these little mites of shells. They were from the great telegraphic plateau (§ 446), and the inference is that there, if any where, the waters of the sea are at rest. There was not motion enough there to abrade these very delicate organisms, nor current enough to sweep them about and mix up with them a grain of the finest sand, nor the smallest particle of gravel torn from the loose beds of debris that here and there strew the bottom of the sea. This plateau is not too deep for the wire to sink down and rest upon, yet it is not so shallow that currents, or icebergs, or any abrading force can derange the wire after it is once lodged.
452. As Professor Bailey remarks, the animalculæ, whose remains Brooke’s lead has brought up from the bottom of the deep sea, probably did not live or die there. They would have had no light there, and, had they lived there, their frail little textures would have been subjected in their growth to a pressure upon them of a column of water twelve thousand feet high, equal to the weight of four hundred atmospheres. They probably lived and sported near the surface, where they could feel the genial influence of both light and heat, and were buried in the lichen caves below after death.
453. Brooke’s lead and the microscope, therefore, it would seems are about to teach us to regard the ocean in a new light. Its bosom, which so teems with animal life; its face, upon which time writes no wrinkles — makes no impression — are, it would now seem, as obedient to the great law of change as is any department whatever, either of the animal or the vegetable kingdom. It is now suggested that, henceforward, we should view the surface of the sea as a nursery teeming with nascent organisms, its depths as the cemetery for families of living creatures that outnumber the sands on the seashore 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 a cradle, and its bottom one vast burial place.
454. On those parts of the solid portions of the earth’s crust which are at the bottom of the atmosphere, various agents are at work, leveling both upward and downward. Heat and cold, rain and sunshine, the winds and the streams, all assisted by the forces of gravitation, are unceasingly wasting away the high places on the land, and as perpetually filling up the low.
But in contemplating the leveling agencies that are at work upon the solid portions of the crust of our planet which are at the bottom of the sea, one is led, at first thought, almost to the conclusion that these leveling agents are powerless there.
455. In the deep sea there are no abrading processes at work; neither frosts nor rains are felt there, and the force of gravitation is so paralyzed down there that it can not use half its power, as on the dry land, in tearing the overhanging rock from the precipice and casting it down into the valley below.
When considering the bottom of the ocean, we have, in the imagination, been disposed to regard the waters of the sea as a great cushion, placed between the air and the bottom of the ocean to protect and defend it from these abrading agencies of the atmosphere.
The geological clock may, we thought, strike new periods; its hands may point to era after era; but, so long as the ocean remains in its basin, so long as its bottom is covered with blue water, so long must the deep furrows and strong contrasts in the solid crust below stand out bold, ragged, and grand. Nothing can fill up the hollows there; no agent now at work, that we know of, can descend into its depths, and level off the floors of the sea.
456. But it now seems that we forgot these oceans of animalculæ, that make the surface of the sea sparkle and glow with life. They are secreting from its surface solid matter for the very purpose of filling up those cavities below. These little marine insects are building their habitations at the surface, and when they die, their remains, in vast multitudes, sink down and settle upon the bottom. They are the atoms of which mountains are formed — plains spread out. Our marl-beds, the clay in our river-bottoms, large portions of many of the great basins of the earth, are composed of the remains of just such little creatures as these, which the ingenuity of Brooke and the industry of Berryman have enabled us to fish up from the depth of more than two miles (twelve thousand feet) below the sea-level.
These foraminiferæ, therefore, when living, may have been preparing the ingredients for the fruitful soil of a land that some earthquake or upheaval, in ages far away in the future, may be sent to cast up from the bottom of the sea for man’s use. The study of these “sunless treasures,” recovered with so much ingenuity from the rich bottom of the sea, suggests new views concerning the physical economy of the ocean.
457. In the chapter on the “Salts of the Sea,” I endeavored to show how sea-shells and marine insects may, by reason of the offices which they perform, be regarded as compensations in that exquisite system of physical machinery by which the harmonies of nature are preserved. But the treasures of the lead and revelations of the microscope present the insects of the sea in a new and still more striking light. We behold them now serving not only as compensations by which the motions of the water in its channels of circulation are regulated and climates softened, but acting also as checks and balances by which the equipoise between the solid and the fluid matter of the earth is preserved. Should it be established that these microscopic creatures live at the surface, and are only buried at the bottom of the sea, we may then view them as conservators of the ocean; for, in the offices which they perform, they assist to preserve its status by maintaining the purity of its waters. It is admitted (§ 343) that the salts of the sea come from the land, and that they consist of the soluble matter which the rains wash out from the fields, and which the rivers bring down to the sea. The waters of the Mississippi and the Amazon, together with all the streams and rivers of the world, both great and small, hold in solution large quantities of lime, soda, iron, and other matter. They discharge annually into the sea an amount of this soluble matter which, if precipitated and collected into one solid mass, would no doubt surprise and astonish the boldest speculator with its magnitude.
458. This soluble matte can not be evaporated. Once in the ocean, there it must remain; and as the rivers are continually pouring in fresh supplies of it, the sea, it has been argued, must continue to become more and more salt. Now the rivers convey to the sea this solid matter mixed with fresh water, which, being lighter than that of the ocean, remains for a considerable time at or near the surface. Here the microscopic organisms of the deep-sea lead are continually at work, secreting this same lime and soda, &c., and extracting from the sea water all this solid matter as fast as the rivers bring it down and empty it into the sea. Thus we haul up from the deep sea specimens of dead animals, and recognize in them the remains of creatures which, though invisible to the naked eye, have nevertheless assigned to them a most important office in the physical economy of the universe, viz., that of regulating the saltness of the sea (§ 342). This view suggests many contemplations. Among them, one in which the ocean is presented as a vast chemical bath, in which the solid parts of the earth are washed, filtered, and precipitated again as solid matter, but in a new form, and with fresh properties. Doubtless it is only a re-adaptation, though it may be in an improved form, of old, and, perhaps, effete matter, to the uses and well-being of man. These are speculations merely; they may be fancies without foundation, but idle they are not, I am sure; for when we come to consider the agents by which the physical economy of this our earth is regulated, by which this or that result is brought about and accomplished in this beautiful system of terrestrial arrangements, we are utterly amazed at the offices which have been performed, the work which has been done, by the animalcule of the water.
459. But whence come the little calcareous shells which Brooke’s lead has brought up, in proof of its sounding, from the depth of two miles and a quarter? Did they live in the surface waters immediately above? or is their habitat in some remote part of the sea, whence, at their death, the currents were sent forth as pall-bearers, with the command to deposit their remains where the plummet found them?
460. In this view, these little organisms become doubly interesting. When dead, the descent of the shell to its final resting place would not, it may be supposed, be very rapid. It would partake of the motion of the sea water in which it lived and died, and probably be carried along with it in its channels of circular tion for many a long mile.
THE MICROSCOPE, under the eye of Ehrenberg, has enabled us (§ 158) to put tallies on the wings of the wind, to learn of them somewhat concerning its “circuits.” Now, may not these shells, which were so fine and impalpable that the officers of the Dolphin took them to be a mass of unctuous clay — may not, I say, these, with other specimens of soundings yet to be collected, be all converted by the microscope into tallies for the waters of the different parts of the sea, by which the channels through which the circulation of the ocean is carried on are to be revealed? Suppose, for instance, that the dwelling place of the little shells which compose this specimen from that part of the ocean be ascertained, by referring to living types, to be the Gulf of Mexico or some other remote region; that the habitat and the burial place, in every instance, be far removed from each other — by what agency, except through that of currents, can we suppose these little creatures — themselves not having the powers of locomotion — to come from the place of their birth, or to travel to that of their burial? Man can never see — he can only touch the bottom of the deep sea, and then only with the plummet. Whatever it brings up thence is to the philosopher matter of powerful interest; for by such information alone as he may gather from a most careful examination of such matter, the amount of human knowledge concerning nearly all that portion of our planet which is covered by the sea must depend. Every specimen of bottom from the deep sea is, therefore, to be regarded as probably containing something precious in the way of contribution to the sources of human knowledge.