EESUME AND GENERAL DISCUSSION. 389 



conclusion from an entirely different starting-point and not following the 

 same route as that taken by the French geologist. Having come to 

 occupy the same ground with him, the writer has, as he believes, been able 

 to fortify himself more strongly in his position than his predecessor in this 

 line of investigation, but simply because the activity -with which glacial 

 phenomena have been observed during the five-and-thirty years since Lecoq 

 wrote places at the command of present investigators a larger body of ma- 

 terial than was available at that early date. 



Ideas very similar to those of Lecoq were advocated, in 1864, by the 

 eminent English chemist and physicist, Frankland, the gist of whose views 

 may be gathered from the following quotation : '• The sole cause of the phenom- 

 ena of the glacial epoch was a higher temperature of the ocean than tlmt which obtains 

 at present. 



" This hypothesis rests chiefly on the two following propositions : — 



" 1st. That a higher oceanic temperature would give rise to an increased 

 evaporation, and consequently to an augmented atmospheric precipitation. 



" 2d. That this increased atmospheric precipitation would augment the 

 average depth of permanent snow upon the ice-bearers, and would, within 

 certain limits, depress the snow-line."* 



When we pass in review the various portions of the earth where ice and 

 snow once covered a greater area than they now do, we are struck by the 

 fact that, with one exception, these are regions where glaciers still exist, so 

 that the phenomena of the Glacial epoch were but a magnified form of 

 present conditions. As illustrations of the various stages of complexity thus 

 exhibited in different regions, we can indeed trace all the intermediate stages 

 between the slight and hardly perceptible increase, as in the case of the 

 glaciers around the volcanic cones of South America, to that of the formerly 

 g-laciated region of Northeastern North America, where we find almost 

 nothing to guide us in connecting the conditions of the present with the 

 phenomena of the past. We may take, first, the Caucasus, where the 

 ancient glaciers existed vmder precisely similar topograjjhical conditions to 



of tlie Alpine erratic blocks, with which the attention of geologists in these later days has been so much occupied, 

 depends entirely on a cause which has not yet been sufficiently appreciated, and which one at first naturally 

 liesitates in accepting. It does not depend on a cold period [periode frigorifique], as some geologists suppose, but, 

 on the contraiy, on an elevated temperature." (1. c. p. 315.) 



* On the Physical Cause of the Glacial Epoch, Philosophical Magazine, Vol. XXVll., 1864, p. 328. Professor 

 Frankland seems to have changed his views somewhat after tlie publication of this paper ; but he still thought 

 "a high temperature of the surface of the sea a necessary condition of the glacial epoch." (See E.xperimental 

 Researches in Pure, Applied, and Physical Chemistry, by E. Frankland, London, 1877, p. 960.) 



