XLVI 



OBSERVATIONS ON THE STRUCTURE OF GLACIER 



ICE 



Phil. Mag., vol. xiv., \?>^'j, pp. 241-260 



The Government School of Mines, 

 Jermyn Street, 



September 14, 1857, 



My Dear Tyndall, 



In the following pages I have given you some account of the 

 experiments and observations upon the structure of glacier ice, which, 

 at your suggestion, I commenced during our sojourn at the Montan- 

 vert this autumn. No one knows better than yourself how much 

 these subjects grow under the hands of the inquirer, and how little 

 claim my brief investigations have to the character of completeness. 

 Nevertheless my conclusions, so far as they go, are based on such 

 clear and decisive evidence, and are so totally opposed to the views 

 entertained by the highest authorities, that I feel I shall be doing 

 more good by publishing than by withholding them. 



I will in the first place state what I have myself observed with 

 regard to the structure and the permeability of glacier ice, and after- 

 wards I will compare my results with those which have been arrived 

 at by others. 



Structure of Glacier Ice. — A mass of ice freshly extracted from 

 any part of the Mer de Glace, the Glacier du Geant, or the glacier of 

 La Brenva, at a depth of 8 or 10 inches from the surface, always 

 presented the following characters when examined either with the 

 naked eye, or with a lens of a magnifying power of thirty or forty 

 diameters. 



It broke with a vitreous fracture ; and when the surface was made 

 even, either with a sharp knife, or by rubbing on a warm surface, it 



