ON THE STRUCTURE OF GLACIER ICE 495 



perfectly transparent so long as it is saturated ; but so soon as one 

 leaves off watering, the fissures reappear where they last appeared 

 when the block was reversed." — P. i6i. 



(ii) " The angular fragments are the consequence and the product 

 ■of the capillary fissures. When a morsel of compact ice is exposed 

 for some time to the air, it becomes decomposed into a certain number 

 of angular fragments, which are the smaller the more numerous the 

 fissures. The same thing would happen to the glacier if its thickness 

 were less, and if the external heat had access to it on all sides. 

 Nevertheless its surface decomposes more or less, the fissures dilate in 

 consequence of the circulation, and the fragments are so dislocated as 

 to be movable on one another without however becoming detached." 

 -P. 163. 



(12) " The angular fragments and the capillary fissures seem to 

 •disappear the moment the ice is covered. Thus on sweeping clean a 

 part of a moraine, or the side of a gravel cone, the ice beneath is 

 found to be perfectly smooth, and apparently without a trace of a 

 fracture. But it is sufficient to leave these same surfaces uncovered 

 for some instants, and the capillary fissures immediately show them- 

 selves, and, in consequence, the angular fragments. They appear 

 with such regularity, that one might be tempted to believe that they 

 are formed spontaneously at the very moment of their appearance. 

 But on examining them with a little attention, one becomes convinced 

 that they are of older date. 



" I by no means pretend to deny that heat, acting suddenly at the 

 moment the moraine is uncovered, may not develope some cracks. I 

 have myself seen such cracks form suddenly (par eclat), but 1 conceive 

 they are but few. If it were otherwise, and if the fissures were formed 

 as they appear, it would be necessary to suppose that there are none 

 in the ice of the moraine before it is uncovered, which would be 

 •contrary to all we know of the transformations of the ice." — P. 165. 



(13) " Let us now make the opposite experiment, and cover with 

 sand and gravel a portion of the surface of the glacier. However 

 fissured and disaggregated it may be, the fissures and angular frag- 

 ments will disappear at the end of some time so completely, that on 

 removing the gravel the surface will be found as compact and trans- 

 parent as that of a portion of moraine which has never been uncovered. 

 And yet it is not probable that the fissures have reunited during the 

 interval. It is, on the contrary, the gravel, which, intercepting the 

 air and keeping the fissures full of water, renders them invisible, and 

 gives to the whole mass a false appearance of compactness, which 

 ceases the moment the air again has access to the fissures." — P. 166. 



