474 



Correspondence — Mr. B. G. Symes. 



coie,ia:Es:po3^X)E3^0E. 



THE MOTION OF GLACIERS. 



Sir, — As tlie motion of glaciers at the present time is by no 

 means a decided point, perhaps the following extracts from my note- 

 book may not be inopportune, more especially as such was observed 

 by me for the first time, and wants corroborative evidence : — " On 

 the 20th July, 1870, when crossing the Mer de Glace, where its 

 breadth is reduced above Montanvert, a distinct fault was observed 

 running N. 20 E., while the general motion of the glacier was N, 

 This fault was observed to extend throughout the glacier, and to be 

 a lateral fault, evidently due to contraction. The exact measurement 

 of the throw was 2 feet 6 inches, and was measured from the veinous 

 structure, which, along the fault, exactly corresponded with the twists 

 peculiar to faults in shaly beds, viz., that the veinous structure was 

 drawn in the direction of the throw. The fault line was plainly 

 visible, but sealed as it were by pressure, and having no unevenness 

 on the surface." 



Plan of a Fault observed in the Mer de Glace, July 20, 1870. 



MONTANVEt^ 



The only conclusions I could come to were, that such fault was a 

 very recent one, produced probably by the very uneven rate of 

 motion, through the action of the Sun, which for that month was 

 most intense. If not a recent fault, the veinous structure would 

 have assumed its normal position. 



ElOHARD G. SyBIES. 

 Baluna, Co. Mayo, Ireland, August 14, 1871. 



