104 DISCUSSIONS IN CLIMATOLOGY. 



mainly brought about, and term them the causes of 

 the event, and the others the necessary conditions. 



I cannot help thinking that the way in which 

 geographical conditions are spoken of as causes of the 

 glacial epoch has tended to confusion. 



During the glacial epoch there were frequent sub- 

 mergences and elevations of the land, or rather oscilla- 

 tions of sea-level, and these, it is true, would produce 

 a change in the relative extent of sea and land. But 

 whether we suppose it to have been the sea which rose 

 and fell in relation to the land, or the land in relation 

 to the sea, it equally follows that the geographical 

 change resulting therefrom could not possibly have 

 been a cause of the glacial epoch. It is now a well- 

 established fact that submergence accompanied glacia- 

 tion ; the glaciation may have been that which led to 

 the submergence ; but it could not possibly have been 

 the submergence which led to the glaciation. An 

 elevation of the land would have favoured glaciation, 

 but submergence would not. Its tendency would 

 rather be in the opposite direction. It is now also 

 established, that during the continental period, or 

 period of elevation, the climate was warm and 

 equable ; for it was then, as has been remarked, that 

 this country was invaded by tropical and subtropical 

 animals. Now, it is equally plain that the elevation 

 could not have been the cause of the heat. Elevation 

 of the land might produce cold, but it could not have 

 been a cause of the heat. It follows, therefore, that 

 the geographical change resulting from submergence 

 or elevation of the land cannot be regarded as a cause 

 of the glacial epoch ; for its effect on climate, if it 

 had any, was in opposition to that of the astronomical 

 and physical agencies. It would prove a hindrance, 

 not a help. 



