Professor Forbes' s Fifteenth Letter on Glaciers. 143 



the settling of the more fluid pai*t in slight depressions ex- 

 isting between " the rough bands, which were raised from a 

 foot-and-a-half to two feet, so as to form ridges^ or waves, or 

 wrinkles, swelling and falling over." The sketch given of 

 these *' wrinkles" is shewn in Fig. 2. Mr Milward was not 

 aware that the analogous phenomenon was discovered by me 

 in glaciers as far back as 1843, and described in my Fifth 

 Letter on Glaciers,* where I have given the accompanying 

 plan and section representing them. It must be as satisfac- 



Rocks. 



.'.'} Gl. '//••' iu ':-:yf-:(reant :, 



Rocks. 



tory to Mr Milward as it is pleasing to me, to find that his 

 shrewd conjectures as to the probability of their discovery, 

 although based solely on the analogy of viscous fluids, are 

 thus perfectly confirmed. They were, in fact, discovered in 

 the place and at the time that Mr Milward supposed they 

 would be, and they were already designated by the very term 

 he uses, "wrinkles," years before he wrote of them. " It 

 will be useless," he observes, " to look for them at the lower 

 parts of glaciers, as they will have disappeared under the 



* Edin. New Phil. Journal, 1844, p. 117, and Appendix to Travels, 2d edit, 

 p. 419. 



