132 



THE FORMS OF WATER 



many cases that have come before us, where 

 the value of au observation Is to be balanced 

 against the danger which it involves. 



464. We do nothing rashly ; but scanning 

 the ledges and selecting a point of attack, 

 we conclude that the danger is not too great 

 to be incurred. We advance to the wall, 

 remove the surface, and are rewarded by the 

 discovery underneath it of the true blue 

 veins. They, moreover, are vertical, while 

 the bedding is horizontal . Bruce, as you 

 know, was defeated in many a battle, but he 

 persisted and won at last. Hero, upon the 

 Furgge glacier, you also have fought and 

 won your little Bannockburn. 



465. But let us not use the language of 

 victory too soon. The stratification theory 

 has been removed out of the field of expla- 

 nation, but nothing has as yet been offered 

 in its place. 



05. RELATION OF STRUCTURE TO 

 PRESSURE. 



460. This veined structure was first de- 

 scribed by the distinguished Swiss naturalist, 

 Guyot, now a resident in the United States. 

 From *he Grimsel Pass I have already 

 pointed out to you the Giles glacier over- 

 spreading the mountains at Ihe opposite side 

 of the valley of the Rhone. It was on this 

 glacier that M. Guyot made his observation. 



467. "I saw," he said, "under my feet 

 the surface of Ihe entire glacier covered with 

 regular furrows, from one to two inches 

 wide, hollowed out in a half-snowy mass, 

 and separated by protruding plates of harder 

 and more transparent ice. It was evident 

 that the glacier here was composed of two 

 kinds of ice, one that of the furrows, snowy 

 and more easily melted ; the other of the 

 plates, more perfect, crystalline, glassy, and 

 resistant ; and that the unequal resistance 

 which the two kinds of ice presented to the 

 atmosphere was the cause of the ridges. 



468. " After having followed them for sev- 

 eral hundred yards, I reached a crevasse 

 twenty or thirty feet wide, which, as it cut 

 the plates and furrows at right angles, ex- 

 posed the interior of the glacier to a depth of 

 thirty or forty feet, and gave a beautiful 

 transverse section of the structure. As far as 

 my eyes could reach, I saw the mass of the 

 glacier composed of layers of snowy ice, each 

 two of which were separated by one of the 

 hard plates of which 1 have spoken, the 

 whole forming a regularly laminated mass, 

 which resembled certain calcareous slates." 



469. I have not failed to point out to you 

 upon all the glaciers that we have visited the 

 little superficial furrows here described ; and 

 you have, moreover, noticed that in the fur- 

 rows mainly is lodged the finer dirt which is 

 scattered over the glacier. They suggest the 

 passage of a rake over the ice. And when- 

 ever these furrows were interrupted by a cre- 

 vasse, the veined structure invariably re- 

 vealed itself upon the walls of the fissure. 

 The surface grooving is indeed an infallible 

 indication of the interior lamination of Has 

 ice. 



