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iriiilions of square miles, and ignoring sparser vegetation^ 

 to arrive at a definite period of exhaustion, even taking 

 liberally into account the apparently inadequate sources of 

 replenishment through the animal kingdom, which would 

 simply extend such period in inverse ratio to its inadequacy. 

 Anyway, we arrive at the conclusion that within a quite 

 conceivable period the supply would be exhausted, and the 

 atmosphere be deprived of its present small proportion of 

 about I in 3,000 parts of carbonic acid gas, or i in 9,000- 

 parts of solid carbon. 



On the other hand, however, we have abundant evidence 

 that active vegetation has been going on from the begin- 

 ning of the carboniferous epoch, when the immense 

 amount of carbon locked up in the coal seams was with- 

 drawn, as I have said, from circulation, and undoubtedly 

 the same process is going en now on a very large scale in 

 many parts of the world. Yet despite this continual draft 

 on the aerial resources, vegetation is presumably as active 

 as ever, and the inevitable question arises. How is the 

 supply maintained ? The oceans are locking up carbon in 

 their future chalk deposits — carbonate of lime, the sea- 

 weeds are like land plants in their structural needs, though 

 possibly unlike in their locking-up capacity, and as 

 animal life is entirely dependent on vegetation, there can 

 be no preponderence there to make up a deficiency. 

 Where, then, is the source of renewal of material to the 

 requisite enormous extent ? Decomposition doubtless con- 

 tributes sornething, animal exhalations something, man 

 himself is returning some of the long locked-up carbon of 

 the coal to the atmosphere, but what is all this as com- 

 pared to the drain of vegetation large and small, wild and 

 cultivated, which, except in arid deserts, clothes the land 

 with verdure, every living cell of which draws in and 

 breaks up its modicum of atmospheric carbonic acid, a 

 good proportion of which is solidified permanently. 



Chas. T. Druery, F.L.S., V.M.H. 



