E. W. COPPINGER ON SOILCAP-MOTION. 



349 



of the name either on the western islands or abutting on the main- 

 land shores of Patagonian channels, although they undoubtedly 

 exist further eastward, and discharge icebergs at the head of some 

 of the deep fiords. In the main straits of Magellan there are fine 

 examples of complete and incomplete glaciers, where one may ob- 

 serve in all its grandeur the wonderful denuding power which these 

 ponderous masses of ice exercise as they move silently along their 

 rocky beds. 



Sir Wyville Thomson (vide ' Voyage of the Challenger,' the 

 " Atlantic," vol. ii. p. 245) attributes the celebrated " stone rivers " 

 of the Falkland Islands to the transporting action of the soilcap, 

 which, among other causes, derives its motion from expansion and 

 contraction of the spongy mass, due to varying conditions of moisture 

 and comparative dryness ; and this hypothesis is to a certain extent 

 supported by the occurrences which I am now endeavouring to de- 

 scribe. Here, in Western Patagonia, are evergreen forests, and a 

 dense undergrowth of brushwood and mosses clothes the hillsides 

 to a height of about 1000 feet ; and this mass of vegetation, with 

 its subjacent soil, resting as it frequently does upon a hillside 

 already planed by ice-action, naturally tends, under the influence 

 of gravitation, combined with that of expansion and contraction, to 

 slide gradually downwards until it meets the sea or a Lake or valley. 

 In the first two cases its free edge is then removed by the action of 

 the water, in a manner somewhat analogous to the wasting of the 

 submerged snout of a Greenland glacier in the summer time ; and 

 in the last case the valley becomes converted into a deep morass. 



It appears to me that the conditions which are said to have 

 resulted in the production of the " stone rivers " of the Falklands 

 here exist in equal if not greater force. There is the thick spongy 

 vegetable mass covering the hillsides and acted on by varying con- 

 ditions of extreme moisture and comparative dryness ; there are 

 the loose blocks of disintegrating syenite to be transported; and 

 there are the mountain-torrents, lakes, and sea- channels to remove 

 the soil. Of actual motion of the soilcap we have at least strong 

 presumptive evidence ; but nowhere in the valleys have I found 

 any thing resembling a " stone river." 



It might perhaps be thought that a slow and gradual depression 

 of the land would account for some of the above phenomena ; but 

 I have seen no reliable sign whatever of subsidence, and have, on the 

 contrary, the evidence of numerous raised beaches and the work of 

 stone-boring mollusca at heights above the present sea-level to prove 

 that elevation of the land has taken place. 



The subject is one full of interest ; and feeling confident that it 

 will repay further investigation, I take this opportunity of bringing 

 the foregoing observations to your notice. 



Discussion. 



The President said the theory brought forward in this paper 

 would very well account for some cases of the infilling of valleys, 



