1842.] DILATATION THEORY REFUTED. 33 



Montanvert, and three times as much in the higher part. It 

 was snowing at the time, and for a week the glacier had been 

 in the same state nearly, the thermometer having fallen in the 

 meanwhile to 20 Fahr. Yet I had abundant evidence that 

 the effect of the frost had not penetrated farther into the ice 

 than it might be expected to have done into the earth under 

 the same circumstances. All the superficial rills were indeed 

 frozen over; there were no cascades in the "moulins;" all 

 was as still as it could be in mid-winter; yet even on the 

 Glacier de Lechaud, my wooden poles, sunk to a depth of less 

 than a foot in the ice, were quite wet, literally standing in 

 water, and consequently unfrozen to the walls; and in the 

 hollows beneath the stones of the moraines, by breaking the 

 crust of ice, pools of unfrozen water might be found almost on 

 the surface. Is it possible, then, that the mere passing chill of a 

 summer night, or the mere cold of the ice itself at all times, can 

 produce the congelation which has been so much insisted on ? 



But (3.) What was the effect of the congelation, trifling as 

 it was, upon the motion of the glacier ? So sharp and sudden 

 a cold succeeding summer weather, must inevitably, it seems to 

 me, were this theory true, have produced an instantaneous 

 acceleration of the mean motion of the glacier. But the con- 

 trary was the fact ; the diurnal motion fell rather short of its 

 previous value, and [no sooner was] the severe weather past, 

 and the little congelation which had taken place thawed, and 

 the snow reduced to water, than the glacier, saturated in all 

 its pores, resumed its march nearly as in the height of summer. 



(4.) It has been inferred from the dilatation theory, that 

 whilst the surface of the glacier continually wastes, it [is] at the 

 same time heaved bodily upwards from beneath, so that its 

 absolute level is unchanged. My experiments, as well as the 

 most ordinary observation (as has been already remarked), 

 disprove this hypothesis. I find that, between the 26th June 

 and the 16th September, the surface of the ice near the side of 

 the Mer de Glace had lowered absolutely TWENTY-FIVE feet 1/5 

 inches, and the centre had undoubtedly fallen more. The 



D 



