On the Reciprocal Dependence of Animals and Vegetables. 91 



now, must have lived and died untouched by quadrupeds ; and 

 even though a certain portion of the carbon taken by them 

 from the atmosphere was again restored to it in the process 

 of decomposition, by far the greater bulk seems to have re- 

 mained in its uncombined form. Even after the creation of 

 the higher orders of vertebra ta, when the forests were inha- 

 bited by the Mylodon with its congeners, and subsequently by 

 the elephant and others of the Pachydermata, it cannot be sup- 

 posed that there was ever by their instrumentality an equili- 

 brium produced between those antagonist agencies — the vege- 

 table and animal creations. For although herds of such crea- 

 tures would doubtless commit extensive ravages upon the ve- 

 getation amid which they existed, it must be remembered that 

 they could only consume the young and comparatively suc- 

 culent portions of the trees upon which they fed, whilst the 

 whole of the carbon contained in the trunks and older branches 

 would remain untouched. That the same preponderance in 

 the assimilative power of the vegetable organisms over the 

 consuming power of the animal ones exists at the present day 

 is abundantly evident. 



The fact of there having been a larger abstraction of carbon 

 from the atmosphere by the decomposition of its carbonic acid 

 gas than has ever been returned to it, will, however, be most 

 distinctly proved by a reference to purely geological data. 

 The vast accumulations of carbonaceous matter contained in 

 the numerous coal basins distributed over the surface of the 

 globe — the large proportion of bitumen existing in many of 

 the secondary deposits, to say nothing of the uncombined 

 carbon which must be diffused through a great part of the 

 strata composing the earth's crust, bear palpable witness to 

 the truth of the position. All such combustible material has 

 been originally derived from the air, and the fact of its re- 

 maining to the present day unoxidized and bidding fair to con- 

 tinue in the same condition (setting aside human agency) for 

 an indefinite period, strongly favours the conclusion that the 

 carbon of which it is composed has been permanently reduced 

 from the gaseous combination in which it previously appeared. 



If then it be conceded that the carbonic acid which during 

 past teras escaped out of the earth has been continually under- 

 going the process of de-carbonization, it follows as an appa- 

 rently legitimate consequence, that its remaining constituent, 

 the oxygen, being thus constantly liberated and effused into 

 the atmosphere, now exists in that medium in a larger propor- 

 tion than it originally did, and that it has from the com- 

 mencement of vegetable life to the present day been ever on 

 the increase. 



