On the Hintereis Glacier. 153» 



exerted, whereas in employing the above formula we have 

 up to the present only suggested an empirical correction to 

 accepted equations. 



There is an imaginary experiment worth noting which 

 would give different results according as we adopted the 

 present theory or the theory of Relativity, and which might 

 therefore serve as an eocperimentum cruris, could the experi- 

 mental difficulties be removed. If we were to detach 

 Michelson and Morley, together with their apparatus, from 

 the earth and send them travelling along at the rate 

 of 19 miles a second in the free aether, the absence of the 

 earth would make no difference according to the theory 

 of Relativity, but would cause a displacement of the fringes 

 according to the present theory (provided that the mass of 

 the experimenters and apparatus is not by itself sufficiently 

 great to introduce a considerable effect of the kind here 

 suggested). There are, however, very grave difficulties to the 

 actual carrying out of this experiment, and it will certainly 

 be some time before they are successfully overcome. 



XVI. The Bintereis Glacier. By R. M. Deeley, 

 M.Inst. C.E., F.G.S., and P. H. Parr*. 



IN a previous communication to this Journal f we have 

 shown that the ellipse is a very unsuitable form of curve 

 to use for the purpose of studying the flow of such a glacier 

 as the Hintereis, for it makes the edges of the ice-stream 

 vertical instead of inclined. Some sections of glaciated 

 valleys were plotted, and it was found that they approximate 

 more closely to parabolas than to ellipses. The conditions of 

 flow down parabolic channels have, however, not yet been 

 ascertained. An attempt was, consequently, made to dis- 

 cover a form of channel which, while approximating to a 

 typically glaciated valley, at the same time was one which 

 could be used for ascertaining: the conditions of flow in the 

 Hintereis Glacier. 



We have already discussed the curve which was found to 

 be suitable and called it Parr's curve for convenience. 



Since writing our paper on " The Viscosit}^ of Glacier Ice," 

 we have still further considered the question, especially as 

 regards the cause of glacier slip and its probable amount ; 

 the conditions of shear stress and temperature within the 

 glacier ; crevassing and viscosity. 



* Communicated bv the Authors, 

 f Phil. Mag-. July 1913, p. 85. 



