276 Professor Agassiz on the Glacier Theory, 



of June last "y ear to the glacier of Aletsch, taking with him 

 an ample provision of stakes, which he had caused to be pre- 

 pared in the Valais. He described, by means of these stakes, 

 planted at equal distances from one another, a triangle placed 

 in relation to several fixed points at the sides ; and he hoped 

 by this means to arrive at a knowledge of the movements of 

 the glacier, not only in the direction of the longitudinal, 

 but also in that of the transversal axis. In order that the 

 winds and storms might not knock over his stakes, he sank 

 all of them to a depth of four feet. What was his surprise 

 when, having gone about the middle of August to visit his 

 triangle, he found that most of the stakes were down, and that 

 those which were still erect did not penetrate more than half- 

 a-foot into the ice ! Twelve days afterwards (the 28th Au- 

 gust), when I ascended the same glacier on my route to the 

 Jungfrau, I found only one of the stakes erect. Thus two 

 months were sufficient to remove a bed of 3J feet in thickness 

 from the glacier of Aletsch ; and notwithstanding, M. Escher 

 assures us that no difference in the level of the surface was 

 perceptible. 



These experiments were so important that I resolved to 

 continue them. Foreseeing that, in the following year, the 

 bore which I had pierced to a depth of 140 feet would be 

 closed, or at least so much contracted as to be no longer of 

 any use to me, I determined to employ it for a similar expe- 

 riment. I therefore took fourteen wooden cylinders, each a 

 foot long, and having a somewhat smaller diameter than that 

 of the bore. I numbered them carefully, and having sunk 

 No. 1 to the bottom of the hole, I covered it with a bed of 

 gravel of 9 feet. I then introduced cylinder No. 2, which I 

 covered in the same manner with a column of gravel of 9 

 feet, and so on in succession ; so that in this manner the en- 

 tire bore contained all the fourteen cyhnders, separated from 

 one another by columns of gravel 9 feet long. The fourteenth 

 was li foot under the surface of the ice on the 6th September 

 1841. As the position of the hole was exactly determined 

 and easy to find, we can easily ascertain what has been the 

 amount of ablation in a given time. Supposing that this ablation 



