76 
LIFE AS A GEOLOGICAL AGENCY. 
products found with them, and, in rare cases, in the stomachs 
of some of them, are those of yet extant plants; and besides 
this evidence, the recent discovery of works of human art, 
wild horses on the plains, and of tamed 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 170,000,000 
domestic quadrupeds belonging to species introduced by European coloni¬ 
zation, 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 destruc¬ 
tible 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. It is true that 
the actual mass of solid matter, left by the decay of dead domestic quadru¬ 
peds 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 do¬ 
mestic animals, and even of the bones, is soon decomposed, through direct 
consumption by man and other carnivora, industrial use, and employment 
as manure, and 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 earthy coating that covers the 
face of the globe. The human bodies deposited in the catacombs during 
the long, long ages of Egyptian history, would perhaps build as large a 
pile as one generation of the quadrupeds of the United States. In the 
barbarous days of old Moslem warfare, the conquerors erected large pyra¬ 
mids of human skulls. The soil of cemeteries in the great cities of Europe 
has sometimes been raised several feet by the deposit of the dead during a 
few generations. In the East, Turks and Christians alike bury bodies but 
a couple of feet beneath the surface. The grave is respected as long as the 
tombstone remains, but the sepultures of the ignoble poor, and of those 
whose monuments time or accident has removed, are opened again and 
again to receive fresh occupants. Hence the ground in Oriental cemeteries 
is pervaded with relics of humanity, if not wholly composed of them; and 
an examination of the soil of the lower part of the Petit Champ cles Marts 
