ANIMAL LIFE AS A GEOLOGICAL AGENCY. 79 



portion, of the bones and tusks of elephants, mastodons, and other 

 huge pachyderms ; and many extensive caves in various parts of 

 the world are half filled with the skeletons of quadrupeds, some- 

 times lying loose in the earth, sometimes cemented together into 

 an osseous breccia by a calcareous deposit or other binding material. 

 These remains of large animals, though found in compai-atively ' 

 late formations, generally belong to extinct species, and their 

 modern congeners or representatives do not exist in sufiicient 

 numbers to be of sensible importance in geology or in geography 

 by the mere mass of their skeletons.* But the vegetable products 



* Could the bones and other relics of the domestic quadrupeds destroyed by 

 disease or slaughtered for human use in civilized countries be collected into 

 large deposits, as obscure causes have gathered together those of extinct ani- 

 mals, they would soon form aggregations which might almost be called moun- 

 tains. There were in the United States, in 1870, as we shall see hereafter, 

 nearly one hundred millions of horses, black cattle, sheep, and svrine. There 

 are great numbers of all the same animals in the British American Provinces 

 and in Mexico, and there are large herds of wild horses on the plains, and of 

 tamed horses among the independent Indian tribes of North America. It would 

 perhaps not be extravagant to suppose that all these cattle may amount to 

 two-thirds as many as those of the United States, and thus we have in North 

 America a total of 160,000,000 domestic quadrupeds belonging to species intro- 

 duced by European colonization, besides dogs, cats, and other four-footed 

 household pets and pests, also of foreign origin. 



If we allow half a solid foot to the skeleton and other slowly destructible 

 parts of each animal, the remains of these herds would form a cubical mass 

 measuring not much short of four hundred and fifty feet to the side, or a 

 pyramid equal in dimensions to that of Cheops, and as the average life of these 

 animals does not exceed six or seven years, the accumulations of their bones, 

 horns, hoofs, and other durable remains, would amount to at least fifteen 

 times as great a volume in a single century. If the statistics of 1880 were 

 taken as the basis of the above calculation, the figures would be raised in a 

 surprising ratio, and the accumulation of a century would be shown to be 

 far greater than is here claimed. It is true that the actual mass of solid mat- 

 ter, left by the decay of dead domestic quadrupeds and permanently added to 

 the crust of the earth, is not so great as this calculation makes it. The greatest 

 proportion of the soft parts of domestic animals, and even of the bones, is 

 soon decomposed through direct consumption by man and other caniivora, in- 

 dustrial use, and employment as manure, and thus enters into new combinations 

 in which its animal origin is scarcely traceable. There is, nevertheless, a large 

 annual residuum, which, like decayed vegetable matter, becomes a part of the 

 superficial mould ; and in any event, brute life immensely changes the form 

 and character of the superficial strata, if it does not sensibly augment the 

 quantity of the matter composing them. 



The remains of man, too, add to the earthly coatmg that covers the face of 



