on the Motion of Glaciers. 



MB 



mouth or outlet A B, by which it pours forth the mass of ice 

 which it is annually unable to contain within its circuit. The 

 breadth of the outlet is about 700 yards, whilst the greater 

 diameter of the basin which it discharges is more than 4200 



Glacier of Talefre. Scale tt^tto* 

 yards, or at least six times greater. Can it for one moment 

 be imagined that any degree of lubrication of the bed of this 

 cake of ice could drag it through the strait in question, even 

 if its adhesion to the soil were absolutely nothing? The thing 

 is impossible; it speaks for itself; the ice is compact and al- 

 most without fissures or open cracks ; in the neighbourhood 

 of the point of issue, structural bands of sliding discontinuity, 

 a a a, are observed, pointing to the outlet, and corresponding 

 to the directions in which the less retarded parts must slide 

 over the lateral and most retarded ; and which recall at once 

 the analogous phaenomena in a stream rushing through an 

 orifice. The open crevasses, which commence a little above 

 A B, are curved upwards towards the basin, or are perpendi- 

 cular to the converging lines. 



It appears to me that from the point of view to which Mr, 

 Hopkins has studiously confined himself in attempting to 

 compare his theoretical deductions and the phaenomena of 

 glaciers, he has suffered himself to be led to results irrecon- 

 cileable with such facts as those just mentioned, as well as with 

 common and notorious experience. I have already declined 

 the task of reconciling them. I shall be better pleased if 

 Mr. Hopkins, leaving for awhile glaciers, and the peculiar set 

 of ideas which by long cogitation have inseparably connected 

 themselves in his mind along with them, will take up the con- 



