1846.] OBSERVATIONS OF M. GUICHABDA. 179 



condition of the Mer de Glace of Chamouni in 1846 was 

 shewn by the fact, that, in spite of the intense and continued 

 heat, it was much higher opposite to the Angle in the middle 

 of August, than it was in June 1842, most of the marks 

 which I then made, for the purpose of estimating the progress 

 of the glacier, being covered by the moraine at the latter 

 period. The extremity of all the glaciers of which I have 

 obtained information, was advancing towards the valley during 

 the summer of 1846 ; and this was even accelerated by the great 

 heat of the season. For though it mast increase the ablation 

 of the surface, and the melting of the terminal face, and thus 

 diminish the mass of ice, its immediate effect is to fuse the 

 glacier into a state of pliancy, such as to increase its motion in 

 a very perceptible manner (as I have established by direct 

 experiment), and thus discharging its icy burden into the valley 

 faster than even the increased atmospheric heat is capable of 

 dissolving it, it spreads with a velocity which, if it could be 

 supposed continual, could not fail to be alarming. Thus it 

 appears, from certain observations made at the desire of M. 

 Carrel, by M. Guicharda, vicar at Courmayeur, that the snout 

 or extremity of the glacier of La Brenva, has protruded into 

 the valley no less than 22 metres, or about 60 [70] feet during 

 the two months of summer, being at the rate of a foot a day. 

 The result of this advance is, that the glacier is rapidly attaining 

 the old moraine of 1818 in the bottom of the valley, from 

 which it is now only about 100 yards distant (see the plan, 

 Plate VIII. fig. 1), whilst it is tearing or ploughing up the soil 

 on the southern bank, marked in Plate VII. fig. 2, on the left- 

 hand side. 



The same gentleman, M. Guicharda, has himself made, with 

 considerable labour, observations intended to test the reality of 

 the movement of the glacier during winter, which confirm, in 

 every particular, those which I have already published regarding 

 the glaciers of Chamouni. The movement appears to be very 

 regular; but, from the position selected for the measurement 

 (the terminal face of the glacier), where the friction is most 



