Apparent objections to the Glacial Theory. 285 



have become such as to give rise to glaciers, and then again re- 

 turned to a higher state and destroyed them ; but this is like build- 

 ing up a structure with one hand, for the sole pleasure of destroying 

 it with the other. Lyell seems to have taught himself to believe in 

 the truth of this hyphothesis, from the occurrence in a fossil state 

 of certain species of shells, still living in temperate climates, but 

 surely this fact instead of proving that the former condition was 

 colder, merely shows that some of the present living forms were 

 capable of existing during the tertiary period likewise, and we 

 know that even in the secondary series, there are some species 

 which occur in more than one member of the system, without 

 proving that the earlier deposit was made during a colder period. 



Nor if we agree with this author, that changes in physical geo- 

 graphy have always affected the temperatur of climates, could the 

 former temperature ever have been colder than in our days ? for we 

 are taught by him, " that since the commencement of the tertiary 

 period, the dry land in the northern hemisphere has been continually 

 on the increase, both because it is now greatly in excess beyond 

 the average proportion which land generally bears to water on the 

 globe, and because a comparison of the secondary and tertiary strata 

 affords indications of a passage from the condition of an ocean inter- 

 spersed with islands, to that of a large continent." — LyelVs Prin. 

 Geol.p. 215. 



Now, that increase of land in northern latitudes must necessarily 

 operate in reducing the temperature, and rendering climates colder, 

 is perhaps one of the surest propositions of the author's theory, and 

 as he shows us from the appearances of the present northern con- 

 tinents, that land has been continually on the increase in the northern 

 hemisphere ever since the commencement of the tertiary period, so 

 he proves to us also most conclusively, that the cold of our climates 

 has been, from the commencement of the same period, continually 

 on the increase likewise. 



It has been urged, that the particular degree of cold which the 

 glacial theory requires, occurred between the conclusion of the 

 tertiary, and the commencement of the modern eras ; but even in 

 this case we fail most signally to prove the truth of the doctrine, 

 for if land in northern latitudes has been continually on the increase 



