Page:Popular Science Monthly Volume 8.djvu/188

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Palæozoic ocean; while the formation of those beds of vast area, in which few or no traces of animal life are found, may be fairly referred to the agency of minute forms, essentially similar to those of the Old Chalk and of its existing representative (Globigerina-mud), whose habitation is the deep sea.

No inconsiderable proportion of the calcareous material of some of the local beds seems to have been furnished by the stems and bodies of the Crinoids (lily-like animals), which abounded in the Palæozoic seas, and of which the representatives at the present time have been proved by recent deep-sea exploration to be much more numerous and widely diffused than was previously supposed. I remember to have seen these very conspicuous in polished sections of the old "black rock;" and certain beds in the limestone of Derbyshire, which are worked for marble chimney-pieces, seem almost entirely composed of their remains. The stems of the Crinoids of the Carboniferous period were not beaded like those of the Dudley (Silurian) limestone, but were cylindrical in form; they had, however, the same jointed structure and central canal; and you will thus readily recognize them when cut either longitudinally, transversely, or obliquely.

It has been further recently shown that Polyzoa essentially resembling those of our modern "coralline crag" existed at this epoch, and had a share in the formation of certain beds of the carboniferous limestone. There is a particular bed in St. Vincent's rocks, which has been found by Mr. Stoddart to be composed of fragments of their delicate calcareous fabrics, with Foraminifera, and other small forms of animal life; and he has appropriately named it the microzoic bed. And Prof. Young, of Glasgow, has been fortunate enough to find, in a clay-seam of the carboniferous limestone in his neighborhood, a collection of these fabrics preserved entire in the fullest perfection.

Thus we seem justified in the conclusion that the vast strata of carboniferous limestone, which in England alone must cover tens of thousands of square miles, and has a thickness of more than two thousand feet, had their sole origin in the continuous life of innumerable generations of humble animals, which, in times long past, did the work that is still being performed in the depths of our own seas by animals of similar types, which we may believe to be their lineal descendants. I have shown you how we are indebted to their agency for the abundant supplies they have provided of a material most useful—I may say indispensable—to us. Let us take care that, with our larger capacities and higher aims, we strive to promote the welfare of those who come after us, by doing well, each in his station, that which our powers and opportunities best fit us to accomplish.—Author's advance-sheets.