156 Mr. R. Mountford Deeley's Theory 



explanation of why Sir W. Thomson did not introduce self- 

 induction into his theory. There were presumably more ways than 

 one of doing it, as regards the measure of the electric force of 

 induction. When we follow Maxwell's equations, there is but one 

 way of doing it, which is quite definite, and leads to a speed 

 which cannot possibly exceed that of light, since it is the speed 

 (fxc)~i through the dielectric, and cannot be sensibly greater than 

 3 x 10 10 centim., though it may be less. Kirchhoff 's result is there- 

 fore in conflict with Maxwell's statement that the German methods 

 lead to the same results as his. Besides that, Wheatstone's clas- 

 sical result has not been supported by any later results, which are 

 always less than the speed of light, as is to be expected (even in a 

 non-distortional circuit). But a reference to Wheatstone's paper 

 on the subject will show, first, that there was confessedly a good 

 deal of guesswork ; and, next, that the repeated doubling of the 

 wire on itself made the experiment, from a modern point of view, 

 of too complex a theory to be examined in detail, and unsuitable as 

 a test. 



XVI. A Theory of Glacier Motion. 

 By R. Mountford Deeley, F. G.S* 



SOME years have now elapsed since the question of glacier 

 motion was brought prominently before the scientific 

 world by the publication of a number of valuable treatises 

 and letters on the glaciers of the Swiss Alps. Each new 

 theory of glacier-motion, as it was given to the world, neces- 

 sitated further observation of the phenomena presented by 

 glaciers, or gave increased interest to the many interesting 

 properties of ice. In this way a vast amount of information 

 has been collected by numerous trained observers, about 

 which there is little dispute; but to the simple question, " Why 

 does a glacier move ?" a great variety of answers would still 

 be given. Indeed, it cannot be said that any substantial pro- 

 gress has been made, for though, as we have seen, a con- 

 siderable number of theories have been framed, no one of 

 them has yet been anything like generally accepted. Prin- 

 cipal J. D. Forbes insisted upon the problem being treated 

 as one of pure mechanics; and to him we largely owe that 

 knowledge of glacier phenomena which Professor Tviulall 

 and others have so ably worked out. Still the old question 

 remains unanswered. We know how the glacier moves, but 

 cannot say why it moves. To add another theory to the 

 already long list may be regarded as tending to make matters 



* Communicated by the Author. 



