The discoveries of the geologist may be inferior in grandeur, but are they practically less illustrative in their bearings on existing arrangements? He sees the past in the present, the near and the distant in time brought together. A charm is thereby thrown over studies and speculations which would otherwise be useless. Thus, in the mineral structures resulting from the agencies of these invisible organic bodies, the mind is struck with the resemblance to similar processes that may be now going forward in the ocean: it sees in the discoloration of the waves, as the voyager steers his vessel over the main, a light by which to decipher the story of an age; and, while no voice issues from the countless myriads of animals which thicken the waters, rocks are elaborating and depositions made that will yet be raised into islands or continents. “On the coast of Chili, a few leagues north of Conception, the Beagle,” says Dr. Darwin, “one day passed through great bands of muddy water, which, when taken up in a glass, was found to be slightly stained as if by red dust, and after leaving it for some time quiet, a cloud collected at the bottom. With a lens of one-fourth of an inch focal distance, small hyaline points could be seen, darting about with great rapidity, and frequently exploding. Examined with a much higher power, their shape was found to be oval, and contracted by a ring round the middle, from which line curved little setæ proceeded on all sides; and these were the organs of motion. The animals move with the narrow apex forward, by the aid of their vibratory cilia, and generally by rapid starts. Their numbers were infinite, and in one day we passed through two spaces of water thus stained, one of which alone must have extended over several square miles. The color of the water, as seen at some distance, was like that of a river which has flowed through a red clay district; but under the shade of the vessel’s side, it was quite as dark as chocolate.”