314 THEORY OF COAL FORMATION. 



the Himalayas,, equally with the less luxuriant vege- 

 tation of our temperate climes,, are directly dependent 

 upon man and the lower animals for their supply of 

 food. 



If all plants were removed from the earth, animals 

 could not exist. How would it be if the animal king- 

 dom was annihilated ? would it be possible for vege- 

 tation to continue? This question is not quite so 

 easily answered; but, if we suppose all the carbon- 

 producing machines the animals to be extinct, from 

 whence would the plants draw their supply? It has 

 been supposed that during the epoch of the coal for- 

 mation a luxuriant vegetation must have gone on over 

 the earth's surface, when the existence of animal life was 

 regarded as problematical. It is supposed that the air was 

 then charged with carbonic acid, and that the calamites, 

 lepidodendra, and sigilaria, were employed to remove it, 

 and fit the earth for the oxygen-breathing races. The 

 evidence upon these points is by no means satisfactory ; 

 and although at one time quite disposed to acquiesce in 

 a conjecture which appears to account so beautifully for 

 the observed geological phenomena of carboniferous 

 periods, we do not regard the necessities for such a 

 condition of the atmosphere as clearly made out.* 

 Geological research, too, has shown that the immense 

 forests from which our coal is formed teemed with life. 

 A frog as large as an ox existed in the swamps, and the 

 existence of insects proves the high order of organic 

 creation at this epoch. 



* At the request of the British Association, a committee under- 

 took the investigation of this suhject Experiments were carried 

 on by Dr. Daubeny, in the Botanic Gardens at Oxford, and by the 

 Author, at his residence, Stockwell. Dr. Daubeny, in his report 

 made at the meeting of the British Association at Birmingham, 

 appears disposed to consider ten per cent, of carbonic acid in ex- 

 cess as destructive to the growth of ferns. I found, however, that, 

 by gradually increasing the quantity, the ferns would live in an 

 atmosphere still more highly charged with carbonic acid. 



