474 POPULAR LECTURES AND ADDRESSES. 



Lyell l and other followers of Hutton, on as sound 

 principles as those of the humblest mechanical 

 perpetual-motionist, tried to find that the earth can 

 go on for ever as it is, illuminated by the sun from 

 infinity of time past to infinity of time future, al- 

 ways a habitation for race after race of plants and 

 animals, built on the ruins of the habitations of 

 preceding races of plants and animals. The 

 doctrine of the " Dissipation of Energy " forces 

 upon us the conclusion that within a finite period 

 of time past the earth must have been, and 

 within a finite period of time to come must 

 again be, unfit for the habitation of man as at 

 present constituted, unless operations have been 

 and are to be, performed which are impossible 

 under the laws governing the known operations 

 going on at present in the material world. 



1 ]*rinciplcs of Geology, vol. ii., edition 1868, p. 213 and pp. 

 40 243 (recapitulation of Chapters xxxi. and xxxiii., I, 10, 15). 



