E. Greenly — Difiision of Granite into Schists. 207 



Under these circumstances some at least of the skeletons of 

 drowned animals would be buried in the sediment at the bottom 

 of the flood ; while any accumulation of bones lying on the plain 

 would be rapidly entombed. That great accumulations of this kind 

 often do occur near water, is indicated by Mr. Hesketh Brichard's 

 observations recorded in his recent book on Patagonia.' On the 

 bank of one small muddy lake he found a heap of at least 500 

 skeletons of guanaco, which had perished during the severities of 

 the previous winter. " Their long necks were outstretched, the 

 rime of weather upon their decaying hides, and their bone-joints 

 glistening through the wounds made by the beaks of carrion-birds." 

 A desolate plain adjoining Lake Viedma is also described as covered 

 with the bones of guanaco and other mammals in great profusion. 

 In fact, in winter the animals seem to congregate near drinking- 

 places where the water is likely to be free from ice, and there they 

 die of starvation in immense numbers. 



According to an observation communicated to me by Professor 

 McKenny Hughes, when bones are exposed to the vicissitudes of 

 ordinary weathering they often disintegrate into sharp flakes. 

 He has noticed this phenomenon especially in the case of bones 

 of rabbits scattered on the ground. It is therefore quite likely that 

 the sharp splinters found mingled with the complete bones in many 

 of the bone-beds are not the result of any physical violence, but 

 merely of prolonged exposure to the elements. 



IV. — The Diffusion of Granite into Crystalline Schists. 



By Edward Greenly, F.G.S. 



(PLATE XIII.) 



1. Boberts- Austen's Experiments on the Diffusion of Metals. 



ABOUT a year ago my friend Professor Dobbie, of the University 

 College of North Wales, drew my attention to the remarkable 

 experiments of Sir W. Eoberts- Austen (whose premature death we 

 must lament as a very great loss to science) on the diifusion of solid 

 metals, suggesting that they might have some geological application. 

 The phenomena referred to in this paper, in which I have been very 

 keenly interested ever since my work as a Geological Surveyor in 

 Eastern Sutherland, occurred to my mind at the time as a probable 

 case ; but after some reflection certain difficulties began to appear, 

 and I put the subject aside for awhile. The very suggestive address 

 of General McMahon to the Geological Section of the British 

 Association at Belfast has reawakened my interest ; and it seems to 

 me worth while to put forward some considerations on the matter, 

 somewhat speculative indeed, but which may perhaps be of service 

 in stimulating research on a fascinating though difficult subject. 



Sir W. Eoberts- Austen- showed that certain selected substances, 

 especially gold and lead, were able to diffuse into each other in the 

 solid state, and at temperatures far below the fusion-point of either. 



1 H. H. Prichard : " Through the Heart of Patagonia " (1902), pp. 189, 203, 254. 

 - Roberts-Austen: Bakeriau Lecture, Phil. Trans., 1896, vol. clxxxvii ; Proc. 

 Eoy. Soc, Oct. 1900, p. 436. 



