The Theory of Glacier motion. 69 



The History and present position of the Theory of 

 Glacier motion. By H. H. Howorth, M.P., F.S.A. 



(Received December 12th, i8go.) 



It is not usual to read papers before this Society which 

 contain neither new facts nor new inferences. I neverthe- 

 less hope that the following memoir, which embodies the 

 results of considerable labour, may be acceptable on 

 grounds which I will state. 



The theory of Glacier motion has involved a long and 

 difficult polemic, in which nearly all the distinguished 

 physicists of the last century have taken part, and in the 

 course of which many hypotheses have been forthcoming and 

 been in turn discarded. In this it shares the fate of many 

 other theories. Where it differs from the rest is in that, 

 whereas at one time opinion gradually converged upon one 

 explanation, namely, that of Forbes, as alone meeting the 

 facts, that explanation was in turn sharply challenged on 

 empirical and a priori grounds, and for many years it had to 

 give place to other theories which seemed more plausible. 

 Quite recently again, more accurate and careful experiments 

 have shown that Forbes was substantially, if not entirely, 

 right. This fact has scarcely yet permeated scientific 

 opinion, and is certainly hardly yet appreciated, and as it is 

 of the first moment in settling questions of far-reaching im- 

 portance in general physics, and especially in theoretical 

 geology, and as it forms the basis of an attack which I have 

 long been preparing upon what I venture to style the Glacial 

 Nightmare of modern geology, I trust I may claim your 

 considerate attention for what I have to say. I have tried 

 to make the paper as complete a monograph as possible, 



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