GEOGRAPHY AND EVOLUTION. 203 



is no indication of any adherent or prearranged disposition toward 

 the development of life in any particidar direction. It would rather 

 appear that the actual face of Nature is the result of a succession of 

 apparently trivial incidents, which by some very slight alteration of 

 local circumstances might often, it would seem, have been turned in 

 a different direction. Some otherwise unimportant difference in the 

 constitution or sequence of the substrata at any locality might have 

 determined the elevation of mountains where a hollow filled by the 

 sea was actually formed, and thereby the whole of the climatal and 

 other conditions of a large area would have been changed, and an 

 entirely different impulse given to the development of life locally, 

 which might have impressed a new character on the whole face of 

 Nature. 



But further, all that we see or know to have existed upon the earth 

 has been controlled to its most minute details by the original consti- 

 tution of the matter which was drawn together to form our planet. 

 The actual character of all inorganic substances, as of all living creat- 

 ures, is only consistent with the actual constitution and proportions 

 of the various substances of which the earth is composed. Other pro- 

 portions than the actual ones in the constituents of the atmosphere 

 would have required an entirely different organization in all air- 

 breathing animals, and probably in all plants. With any consider- 

 able diffei-ence in the quantity of water either in the sea or distributed 

 as vapor, vast changes in the constitution of living creatures must 

 have been involved. Without oxygen, hydrogen, nitrogen, or car- 

 bon, what we term life would have been impossible. But such specu- 

 lations need not be extended. 



The substances of which the earth is now composed are identical 

 with those of which it has always been made up ; so far as is known 

 it has lost nothing and has gained nothing, except what has been 

 added in extremely minute quantities by the fall of meteorites. All 

 that is or ever has been upon the earth is part of the earth, has sprung 

 from the earth, is sustained by the earth, and returns to the earth ; 

 taking back thither what it withdrew, making good the materials on 

 which life depends, without which it would cease, and which are des- 

 tined again to enter into new forms, and contribute to the ever-onward 

 flow of the great current of existence. 



The progress of knowledge has removed all doubt as to the rela- 

 tion in which the human race stands to this great stream of life. It is 

 now established that man existed on the earth at a period vastly an- 

 terior to any of which we have records in history or otherwise. He 

 was the contemporary of many extinct mammalia at a time when the 

 outlines of land and sea, and the conditions of climate over large 

 parts of the earth, were wholly different from what they nov^^ are, and 

 our race has been advancing toward its present condition during a 

 series of ages for the extent of which ordinary conceptions of time 



