264 PROFESSOR JAMES GEIKIE, LL.D., D.C.L., F.R.S., ETC. 



a Glacial Period in one hemisphere there was an inter-glacial period 

 in the other ; during the continuance of great eccentricity in the 

 earth's orbit, glacial and inter-glacial periods alternated with each 

 other in the opposite hemispheres. 



My theory on this subject has been suggested by Mr. Croll's, but 

 it is not the same. Mr. Croll, for reasons which I fail to under- 

 stand, though I have read them carefully, places the glacial climate 

 in the hemisphere which has its summer when the earth is nearest 

 the sun, and consequently, as it seems to me, when the heat of 

 summer is greatest, and the snow of the previous winter is most 

 completely melted away. It is certain that at the present time, 

 the nearest approach to a glacial climate, as shown in the greatest 

 extent and the lowest descent of glaciers, is not to be found in 

 countries of intense winter cold like Siberia, but in regions of 

 cold summer and abundant snowfall, like the shores of the Straits 

 of Magellan. Practically these remaz'ks summarise my views as 

 given to the Geological Society {on the Nature and Cause of the 

 Glacial Climate), and the Belfast Natural History Society. 



NOTE. 



Professor Geikie has seen the foregoing letters. He offers no further 

 remarks. —Ed. 



