42 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. 



THE ABUNDANCE OF ANIMAL LIFE; 



By M. ALBEET GAUDKY. 



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 algse, with- 

 drawing 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. Plan- 

 cus has calculated that three grammes of certain sands of the 

 Caribbean Sea contain 180,000 shells of foraminifera. M. Schlum- 

 berger found 116,000 foraminifera shells in a cubic centimetre of 

 the Atlantic mud which was brought up by the Travailleur expe- 

 dition. 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 Eiheria 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 Onatliodons 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 



