Page:Popular Science Monthly Volume 7.djvu/39
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EXPEDITION OF THE CHALLENGER.
most universally present, generally eludes the search of the naturalist; except when its species are congregated among that mucous scum which is sometimes seen floating on the waves, and of whose real nature we are ignorant; or when the colored contents of the marine animals who feed on these algæ are examined. To the south, however, of the belt of ice which encircles the globe, between the parallels of 50° and 70° south, and in the waters comprised between that belt and the highest latitude ever attained by man, this vegetation is very conspicuous, from the contrast between its color and the white snow and ice in which it is embedded. Insomuch, that in the eightieth degree, all the surface-ice carried along by the currents, the sides of every berg, and the base of the great Victoria Barrier itself, within reach of the swell, were tinged brown, as if the polar waters were charged with oxide of iron.
"As the majority of these plants consist of very simple vegetable cells, inclosed in the indestructible silex (as other algæ are in carbonate of lime), it is obvious that the death and decomposition of such multitudes must form sedimentary deposits, proportionate in their extent to the length and exposure of the coast against which they are washed, in thickness to the power of such agents as the winds, currents, and sea, which sweep them more energetically to certain positions, and in purity, to the depth of the water and nature of ^he bottom. Hence we detected their remains along every ice-bound shore, in the depths of the adjacent ocean, between 80 and 400 fathoms. Off Victoria Barrier (a perpendicular wall of ice between 100 and 200 feet above the level of the sea) the bottom of the ocean was covered with a stratum of pure white or green mud, composed principally of the silicious shells of the Diatomaceæ. These, on being put into water, rendered it cloudy like milk, and took many hours to subside. In the very deep water off Victoria and Graham's Land, this mud was particularly pure and fine; but toward the shallow shores there existed a greater or less admixture of disintegrated rock and sand; so that the organic compounds of the bottom frequently bore but a small proportion to the inorganic...."
"The universal existence of such an invisible vegetation as that of the Antarctic Ocean is a truly wonderful fact, and the more from its not being accompanied by plants of a high order. During the years we spent there, I had been accustomed to regard the phenomena of life as differing totally from what obtains throughout all other latitudes, for every thing living appeared to be of animal origin. The ocean swarmed with Mollusca, and particularly entomostratous Crustacea small whales, and porpoises; the sea abounded with penguins and seals, and the air with birds; the animal kingdom was ever present, the larger creatures preying on the smaller, and these again on smaller still; all seemed carnivorous. Thewere not recognized, because feeding on a microscopic herbage, of whose true nature I had formed an erroneous impression. It is, therefore, with no little satisfaction that I now class the Diatomaceæ with plants, probably maintaining in the South Polar Ocean that balance between the vegetable and animal kingdoms which prevails over the surface of our globe. Nor is the sustenance and nutrition of the animal kingdom the only function these minute productions may perform; they may also be the purifiers of the vitiated atmosphere, and thus execute in the antarctic latitudes the office of our trees and grass-turf in the temperate regions, and the broad leaves of the palm, etc., in the tropics...."
With respect to the distribution of the Diatomaceæ, Dr. Hooker remarks: