Soil Motion here and in the Falklands, 77 



Sir Wyville Thompson (vide " Voyage of Challenger," vol. ii., 

 p. 245) attributes the origin of the celebrated "Stone Runs" of 

 the Falkland Islands to the transporting action of the soilcap, 

 which among other causes derives its motion from alternate 

 expansion and contraction of the spongy mass of peat, due to 

 varying conditions of moisture and comparative dryness ; and 

 this hypothesis is to a certain extent supported by the occur- 

 rences which I now endeavour to describe. Here, in Western 

 Patagonia, an evergreen arboreal forest, rising through a dense 

 undergrowth of brushwood and mosses, clothes the hill-sides to 

 a height of about 1,000 feet, and this mass of vegetation, with 

 its subjacent peaty, swampy soil, resting — as it frequently does 

 — upon a hill-side already planed by old ice action, naturally 

 tends, under the influence of gravitation, combined with that of 

 expansion and contraction of the soil, to slide gradually down- 

 wards until it meets the sea, lake, or valley, as the case may 

 be. In the two former cases the free edge of the mass is 

 removed by the action of the water, in a manner somewhat 

 analogous to the wasting of the submerged snout of a "com- 

 plete glacier " in the summer time ; whereas in the last instance 

 a chaotic accumulation of all the constituents of the transported 

 mass gradually takes place, thereby tending to an eventual ob- 

 literation of the valley. It appears to me that the conditions 

 which are said to have resulted in the formation of the " Stone 

 Runs " of the Falklands here exist in equal if not greater 

 force. There is a thick spongy vegetable mass covering the 

 hill-sides, and acted on by varying conditions of extreme 

 moisture and comparative dryness ; there are the loose blocks 

 of disintegrating syenite to be transported ; and there are moun- 

 tain torrents, lakes, and sea- channels to remove the soil. That 

 motion of the soilcap does actually take place we have at least 

 strong presumptive evidence ; but anything resembling a " stone 

 run " remains yet to be discovered. It would naturally suggest 

 itself to the reader that the above phenomenon attributed to 



