'88 Mr. H. H. Howorth on 



penetrate the surface more than a moderate number of feet^ 

 and that of the night scarcely as many inches. Again, if his 

 theory be true, a glacier ought to progress at a rate propor- 

 tional to its length, which it does not. In winter glaciers 

 are covered with snow, which protects them against the 

 effect of radiant heat, but in winter, glaciers move on as 

 they do in summer, only at half the pace, How, again, by 

 such a theory, can we account for the differential motion 

 between the centre and the sides of a glacier ? (Ball, PhiL 

 Mag., XL. I — lo). 



After Canon Moseley's death his theory was revived by 

 Mr. Brown, in a paper read before the Royal Society {Pro- 

 ceedings, Vol. XXX.). In this he somewhat modified the 

 original view, in order to meet objections, and urged that 

 the contraction and expansion of the surface layers of a 

 glacier drag the lower layers after them, and cause the 

 upper layers to shear over those below them. To this par- 

 ticular argument it may be urged that the notion, that the 

 contraction and expansion caused by diurnal variation of 

 temperature on an Alpine glacier, which directly affects 

 only two or three feet of its surface, can influence its motion 

 for a thickness of several hundred feet, is assuredly ex- 

 travagant. Again the recurrence of crevasses must prevent 

 the contraction between portions of the surface layer at 

 any considerable distance from one another (Trotter^ 

 Proceedings Royal Society, XXXVIIL, 93). This concurrence 

 of evidence seems to put Mr. Moseley's theory, which a few 

 years ago was advocated with so much pertinacity and 

 success, out of court altogether, nor do I know that it 

 retains any supporters. Let us now turn to another theory^ 

 which still has some adherents. 



In the year 1845 Mr. Sutcliffe communicated to the 

 Philosophical Magazine a paper on a theory of glacier 

 movement. In this paper he proposed to reconcile the 

 apparent contradiction between the observed action of 



