Slowly, imperceptibly, but incessantly, are the vital energies of the feeblest and minutest animal and vegetable existences separating from the element in which they live, the most enduring of mineral substances, silex--fabricating it into structures of the most exquisite forms and sculpturing, and thus adding to the accumulations of countless ages, which make up the sedimentary strata of the crust of the globe. In the "Medals of Creation"[123] will be found a summary of what was then known as to the formation and composition of many tertiary deposits which the indefatigable Ehrenberg, Dr. Bailey, and other eminent observers, had carefully investigated and described. The five years that have since elapsed have been fruitful in results of the most important and interesting character; from every quarter of the world, from the loftiest mountain peaks, and from the deepest recesses of the ocean which the plummet can reach, from the ashes of volcanoes and from the snow of the glaciers, the durable remains of Infusoria have been obtained. That excellent scientific periodical, Silliman's American Journal, contains numerous interesting communications on this subject from the eminent chemical professor of the Military College at West Point, Dr. J. W. Bailey; and the labours of Mr. Bowerbank, Williamson, and other active members of the Microscopical Society of London, have yielded much interesting information on the infusorial deposits of our own country. [Footnote 123: Medals of Creation, vol. i. p. 211.]