356 Proceedings of Societies. 



are invariably brought by a low creeping fog, which comes up from Lal- 

 lan ches. It seldom overtops the Col de Voza, and the Aiguilles appear 

 bright and sunny in the gaps of the cloud. It is in spring and autumn 

 that these high peaks are powdered by every storm ; now the dispersing 

 clouds leave them as dark as before they gathered. I fancy this winter is 

 unusually cold ; every one is crying out, and complaining that the po- 

 tatoes are frozen in deep cellars. I have seen Reaumur's thermometer at 

 -25° at 5 £ in the afternoon, and I think it may reasonably be supposed 

 that it may have fallen to — 30° during the night ; wine has frozen on my 

 table before a fire. In the woods the trees crack with the intense frost 

 and there is from 2£ to 3 feet of snow in the valley without drifts ; on the 

 glacier of Blatiere there is only from 1 to 2 feet. 



In spite of all this cold the glaciers advance steadily. The glacier de 

 Blatiere, terminating above the line of trees, pushes its moraine in front 

 of it, and seems to be on the increase. Now this is a very shallow glacier, 

 and, as I have said, covered with but little snow. Is it possible that in- 

 filtrated water can have any action whatever under such circumstances ? 



I will here state a few results of careful observation, and I hope that, 

 even should they appear strange, you will yet consider them worthy of 

 confidence. I have no theodolite, but I have a prismatic compass, and 

 will take the bearings of various points from my stations should you deem 

 it advisable. 



The torrent of Bossons has been quite dry ever since the beginning of 

 November, and I have profited by this circumstance to endeavour to de- 

 termine the motion of the ice within the vault, nearly in contact with the 

 ground. I believe it is usually supposed that the reason why the termi- 

 nation of a glacier seems stationary in summer, is that there the waste 

 predominates over the supply. It seemed to me therefore, that in winter, 

 when there is actually no waste — the torrent being perfectly dry, and 

 its subglacial bed even dusty — the end of the glacier ought to be thrust 

 forward into the valley by the pressure behind. I accordingly with some 

 little difficulty, fixed a station on the ridge or back of the glacier, near 

 the lower extremity ; the result is, that the ice there is nearly sta- 

 tionary. This is doubtless a clue to the assertions of some authors, ' that 

 the glacier is stationary in winter;'' — they only looked at the end. 

 "What becomes, then, of the ice continually descending from above? 

 Does it not go to thicken the whole mass, accumulating behind the more 

 rigid portion below, as water behind a dam ? I have no space to add 

 more at present, but will write again if I have your approval of my pro- 

 ceedings. Meanwhile I have fixed (yesterday) an intermediate station, 

 for the purpose of determining where this comparative immobility begins. 

 I have noted my observations, and kept a register of weather, &c. I 

 give one observation to show the difference between the middle and lower 

 glaciers : — 



From December 28 to January 11 — 14 days. 



Middle glacier (somewhat above where it is usually crossed). 

 Centre, 14 ft. 7 in. (fourteen feet, seven inches). 

 Side, 11 ft. 6 in. (eleven feet, six inches). 



Lower glacier in the same period. 

 Ridge, 1 ft. 7 in. (one foot, seven inches). 

 Interior of vault, ft. 2 in. (two inches). 



Observations on Mr BlackwelV s Letter. By Professor Forbes. 

 The cold described ( - 25° to - 30° of Reamur ~ 24 J° to - 35£° of Fahren- 



