2l6 MY LIFE [Chap. 



(January 9) on "The Cause of the Ice Age," pointing out 

 the extreme complexity of the subject, and the fallacy 

 of discussing the problem as if it were merely one of the 

 amount of sun-heat received in different latitudes under 

 differing degrees of eccentricity, as several eminent mathe- 

 maticians had done. In the same issue Sir Robert Ball 

 pointed out the same fallacy ; and this affords a good illustra- 

 tion of the fact that specialists are usually not well fitted to 

 arrive at the true explanation of great natural phenomena 

 which are highly complex in their nature, and which require 

 the consideration of a great variety of physical forces and 

 laws in order to arrive at their causes. It is for this reason 

 that Mr. Croll's theory is so much more satisfactory than any 

 of the modern substitutes for it. His views were, however, 

 spread over many different periodicals, and are often rather 

 obscure and disconnected, while few of his recent critics 

 appear to have studied the whole of them. I venture to 

 think that my chapter viii. of "Island Life" gives the 

 best connected and systematic statement of Croll's views 

 which are to be found, and that the further explanations 

 of essential points, and some modifications in detail, render 

 it the completest and most rational theory which has yet 

 been set forth. Being myself a mere outsider, neither a 

 geologist nor a mathematician, and only an amateur physicist, 

 none of the writers on the subject appear to have read my 

 chapter, since I have never seen it referred to. Yet it 

 appeals throughout to astronomical, physical, geographical, 

 and meteorological facts, showing their actions and reactions 

 on each other, and how they co-operated to produce the 

 glacial epoch, as they now co-operate to bring about the 

 strikingly contrasted climates of the eastern and western 

 shores of the North Atlantic, and the still more striking 

 contrasts of the Arctic and Antarctic regions. 



During this summer I was invited by Dr. H. S. Lunn to 

 go with him and his party to Davos for a week early in 

 September, and to give them a lecture on Scientific Progress 

 in the Nineteenth Century. As I had never been in this part 



