94 THE JOURNAL OF GEOLOGY. 



Outside the area of the European continental ice sheet, facts are 

 adduced in striking confirmation of the multiple ice epoch theory. 

 These facts are found in Switzerland, where evidences of multiple 

 glaciation have been recognized, and in the Pyrenees where evidences 

 of three separate ice epochs have been found. In France, evidences 

 of an inter-glacial interval have been found in the region of the Puy 

 de Dome of such duration as to allow the excavation of valleys to a 

 depth of 900 feet. The length of time which would be required for 

 such stupendous erosion must certainly be regarded as sufficient to 

 allow the preceding and succeeding glaciations to be considered as 

 belonging to two distinct epochs. 



Another point of great significance and interest which Prof. 

 Geikie's essay brings out, is the correlation in Britain between epochs 

 of glaciation and epochs of subsidence on the one hand, and 

 between interglacial intervals and epochs of elevation on the other. 

 If Prof. Geikie's interpretation be well founded, and so far as we are 

 able to judge from the facts presented this is the case, his conclusions 

 would seem to be fatal to the hypothesis that glacial climate was pro- 

 duced by northern elevation. 



The map which Prof. Geikie gives, showing the limit of ice 

 advance during the fourth glacial epoch, seems to us open to criticism. 

 On the ground of personal observation, the writer believes that the ice 

 sheet of the glacial epoch here represented did not extend notably, if 

 at all, beyond the Baltic Ridge. ^ 



Prof. Geikie is an advocate of Dr. Croll's astronomical theory of 

 glacial climate, and thinks that even five is not the full number of 

 glacial epochs belonging to the Pleistocene period. He believes there 

 may have been a series of glacial epochs increasing in severity to a maxi- 

 mum represented by what is now designated as the second glacial epoch. 

 This maximum was followed by a series of epochs of diminishing severity, 

 represented by what he designates the third, fourth and fifth epochs. The 

 essay is a timely contribution to glacial geology. Rollin D. Salisbury. 



' See American Journal of Science, May, 1887. In a recent letter, Prof. Geikie 

 indicates that he is convinced, from subsequent personal observation, that his map is 

 erroneous so far as the limit of the ice of this epoch is concerned. The mapping 

 given was based on the opinion of others. 



