314 GEOLOGICAL KEFORM X 



the period recorded in the most ancient strata 

 now open to observation in the crust of the earth. 

 This is, for Hutton, " the point in which we can- 

 not see any farther " ; while Lyell tells us, 



" The astronomer may find good reasons for 

 ascribing the earth's form to the original fluidity 

 of the mass, in times long antecedent to the first 

 introduction of living beings into the planet ; but 

 the geologist must be content to regard the earliest 

 monuments which it is his task to interpret, as 

 belonging to a period when the crust had already 

 acquired great solidity and thickness, probably as 

 great as it now possesses, and when volcanic rocks, 

 not essentially differing from those now produced, 

 were formed from time to time, the intensity of 

 volcanic heat being neither greater nor less than 

 it is now." l 



And again, " As geologists, we learn that it is 

 not only the present condition of the globe which 

 has been suited to the accommodation of myriads 

 of living creatures, but that many former states 

 also have been adapted to the organisation and 

 habits of prior races of beings. The disposition of 

 the seas, continents and islands, and the climates, 

 have varied ; the species likewise have been 

 changed ; and yet they have all been so modelled, 

 on types analogous to those of existing plants and 

 animals, as to indicate, throughout, a perfect 

 harmony of design and unity of purpose. To 

 1 Principles of Geology, vol. ii. p. 211. 



