Page:Popular Science Monthly Volume 50.djvu/54
THE POPULAR SCIENCE MONTHLY.
sideration what I know of these two Battak girls, I must say I have not infrequently met with types of negroes, both in the South as well as in Washington, that possessed features nearly the counterpart of these Battaks. In this connection we must remember, however, that the negroes in this country need not trace back so very far before their arrival at an ancestral stock that can hardly be considered above suspicion in the matter of cannibalism, and that, too, without having been the inventors of an alphabet and a written language to redeem the fact.
By M. ALBERT GAUDRY.
WE find in studying the past epochs of the earth's history that they have been marked by an abundance of life, even exceeding any which prevails in the present. Comparing the existing state with the past, we are struck with the immensity of the part played by the inferior organisms. Life is everywhere; the number of microbes is infinite. Rocks which at first seem to belong only to the domain of mineralogy are found to appertain very largely to that of biology. One of the grandest spectacles, for example, is offered by the travertines of the Mammoth Hot Springs, in the Rocky Mountain National Park, which Mr. Weed declares are formed chiefly through the agency of algæ, withdrawing the excess of carbonic acid from the water, and forcing the precipitation of the limestone. Going from the hot springs to the geysers, we find deposits of silica which have been formed in the same way; and what is called gelatinous silica is largely vegetable matter. The lower animals are also so numerous in some places that they contribute to the formation of rocks. Plancus has calculated that three grammes of certain sands of the Caribbean Sea contain 180,000 shells of foraminifera. M. Schlumberger found 116,000 foraminifera shells in a cubic centimetre of the Atlantic mud which was brought up by the Travailleur expedition. Polyps construct atolls, barrier reefs, and islands; and if the bottoms of the oceans were uncovered we should doubtless see coralline rocks no less extended than the Secondary formation called the coral rag. It is said that the shells of the Etheria form such large beds in the Senegal that they are quarried to be made into lime, and that on the shores of Lake Pontchartrain, near New Orleans, the Gnathodons form a bed four miles and a half long, nearly two hundred feet wide, and sixteen feet thick. I have been informed by M. Sauvage, to whom we owe many important works on marine animals, that the year's crop of oysters as entered in the