io6 POPULAR LECTURES AND ADDRESSES. 



" whole regions. The theorist in vain endeavours 

 " to explain such operations by processes so slow 

 " in their action, as to be almost imperceptible. If 

 " it be argued that the strata constituting lofty 

 " mountains were metamorphosed in parts by such 

 " a slow process, let any one who sustains that 

 " view explain how it is that every stratum in a 

 " lofty range of mountains, composed of carbon- 

 " ate of lime, should, in some cases, all at once 

 " change into sulphate of lime, and in others into 

 " dolomite." 



24. Sir Charles Lyell himself admits a warmer 

 climate in the earliest geological periods. Thus 

 considering " a general * refrigeration of climate ; " 

 (from the more ancient times understood) " and 

 " several oscillations of temperature during the 

 " glacial epoch ;" to be proved by palaeontological 

 evidence ; he endeavours to explain those past 

 changes chiefly if not solely by hypothetical alter- 

 ations in the distribution of land and sea over the 

 globe. Kvcry reader of the Principles of Geology 

 must admire the ingenuity, and admit the import- 

 1 Principles of Geology i Vol. I., page 387. 1867 Edition. 



