260 Professor Agassiz on the Glacier Theory. 



proceed with renewed ardour ; but what was our surprise, 

 when we were about to introduce the piercer into the hole, 

 to find that it would no longer enter. We then remarked 

 that the hole had become contracted by half an inch, and we 

 had no other course left but to recommence anew. We re- 

 quired three days to reach the depth of 70 feet, at which we 

 had left the bore. For my own part, instead of regretting; 

 this loss of time, I rejoiced at the circumstance, for I had 

 thus obtained the most manifest proof of the dilatation of the 

 glacier to a considerable depth. The contraction was not 

 merely superficial, but extended as far as the bore did ; and 

 it could not be the result of the water congealed along its 

 walls, for care had been taken to remove the little stream- 

 lets, and I had caused the few inches of water which accu- 

 mulated at the bottom of the hole, in consequence of transu- 

 dation, to be taken out every evening. 



One day the workmen felt the piercer escape from their 

 hands, and fall down two feet. They were then at a depth 

 of 110 feet. It was evidently an internal cavity which had 

 been encountered, and a certain quantity of air-bubbles were 

 soon seen arriving at the surface, after having traversed the 

 column of water which filled the bore. Unfortunately I was 

 not near at the time, and the bubbles of air, whose nature it 

 would have been interesting to ascertain, could not be col- 

 lected. But the fact is of itself not the less important, be- 

 cause it furnishes us with the proof that there are cavities in 

 the interior of glaciers at very considerable depths, and in 

 places where the surface does not exhibit any trace of a large 

 and deep crevasse. The splinters which were detached by 

 the piercer, and which ascended to the surface, had the same 

 appearance and the same hardness as if they had been de- 

 tached from the wall of a crevasse. In two other cases, bub- 

 bles of air rose from the bore, without, however, the piercer 

 descending suddenly. I have also seen them frequently ascend 

 to the surface of hollows in the ice (baignoires\ filled with 

 water. 



I was provided with three of Bun ten's thermometrograi)hs, 

 which I placed every evening in the following manner : one 

 in the great bore ; a second in the hole less deep, generally at 



