The Theory of Glacier motion, 133 



cient to account for its descent" {Phil.Mag.y^^yi.VU. 233-235). 

 These experiments had a very great effect on the scientific 

 mind of Europe. They seemed conclusive against Forbes's 

 views. As Mr. Trotter says, "granting that the shearing 

 strength of ice as deduced from his (Moseley's) experi- 

 ments represents even approximately the resistance 

 to shearing under the actual circumstances of glacier 

 motion, his objection to Forbes's view is fatal." 



Mr. Moseley did not fail to use the weapon he had dis- 

 covered, and pressed with great persistency the view that 

 his experiments had proved the viscous theory to be 

 untenable. On Mr. Moseley's death, Mr. W. R. Brown, who 

 championed his views, {Proceedings of the Royal Society, 

 vol. XXXIV.) adduced fresh arguments against Forbes, 

 from more general considerations. He urged that the 

 existence of ice cliffs, such as those in the crevasses 

 in South America, 300 feet thick, which ought to flow 

 over if Forbes's view be right, seem to militate against 

 it. Putting aside Forbes's own experiments about crevasses 

 themselves being short-lived, the argument of Mr. Brown 

 had been already answered by anticipation by Dr. WhewelL 

 He says : " Soft pitch will stand on cliffs some inches high, 

 soft clay will stand on cliffs many feet high ; clay may 

 stand on cliffs hundreds of feet high, and yet be plastic, if 

 the mass be very large, and the pressure distributed 

 through it be powerful enough to make one part move past 

 another. We cannot doubt that clay might be hard enough 

 to stand on such cliffs, and yet soft enough to slide down a 

 sloping valley as a plastic substance, if the valley were 

 filled with it for many miles long and hundreds of feet 

 thick ; and still more if there were streams of water running 

 through all parts of the mass " {F^hil. Mag., XXVI. 172 and 3). 



Again, as Mr. Trotter says, "the spreading out of a 

 glacier like the Rhone glacier when It emerges from a gorge 

 on to a comparatively open space, is in itself a convincing 

 I 



