"Researches on Existing Glaciers, 277 



is on an average only 5 feet in the year, and that the glacier 

 continues to advance in the same proportion — that is to say, 

 about 200 feet annually — the cylinder No. 1 ought to reach 

 the surface in about 28 years, and at a distance of 5600 feet 

 from the place where it was inserted. In this calculation the 

 inequality of the rapidity of the beds is certainly not taken 

 into account, and which, according to the most recent re- 

 searches, must be less considerable than I at first supposed. 



The second bore, having a depth of 30 feet, was employed 

 for an experiment from which I expect still more important 

 results. We have seen, from the general view I have already 

 given of the temperature of the interior of the glacier, that 

 this temperature varied but little during the whole period of 

 our residence on the glacier. It was important to ascertain 

 if this was also the case during the colds of winter, when the 

 glacier is covered with a thick bed of snow. I therefore re- 

 solved, with this view, to make use of my three minimum 

 thermometers. I placed two in the bore, and suspended the 

 third freely in the air at the top of the trepied. In order to 

 preserve these instruments from the influence of the water, 

 and that I might not have difficulty in raising them after- 

 wards, I had a tin-case made, which was 2^ inches in diame- 

 ter and 24 feet in length, and which I sank in such a manner 

 that its upper end was a foot below the surface of the ice. I 

 introduced the first thermometer into the bottom of the case, 

 and placed the second at 12 feet higher up ; so that the latter 

 was at a depth of 13 feet, and the first at a depth of 25 feet, 

 in the glacier. In order, moreover, to protect my instruments 

 from the possibility of being pressed by the walls of the gla- 

 cier, I took care to include each of them in a thick sheath of 

 brass. Each instrument is coated with tallow in its sheath, 

 and the tin case which contains both is also equally well 

 closed, so as to prevent the access of water. By this means 

 I hope this year to obtain in these lofty regions the minimum 

 temperature of the glacier, at depths of 25 and 13 feet, and 

 that of the air at 12 feet above the surface. I intend going 

 to ascertain the results whenever the snow has disappeared 

 from the surface of the glacier. 



