SECRETARY'S REPORT. 181 



owing to another series of facts, to which I will now call your 

 attention, I have measured the depth and thickness of the 

 mass of ice in the chain of mountains to which I have referred. 

 I have been under it ; I have been in it ; I have seen it in every 

 possible way ; I have let myself down into the crevasses to the 

 depth of several hundred feet ; I have walked up the streams 

 which flow out from below, so that I can speak from personal 

 observation of the character of the facts to which I am now 

 alluding. In some parts, this mass of ice is about a thousand 

 feet thick ; in some parts, it is three or four miles wide ; at its 

 lower end, it is about one mile wide, and the length is about 

 seventeen miles. This, however, is not one of the great glaciers. 

 It is a dwarf in comparison with some of the Arctic glaciers 

 observed by Dr. Kane. The Humboldt glacier is one hundred 

 times larger than that. And yet you have here a surface of 

 ice seventeen miles in length, with an average width of over 

 two miles, an average thickness of many hundred feet, and at 

 least a thousand feet high. You will conceive, therefore, that 

 this mass of ice, moving down that valley, will produce some 

 mechanical effect ; and it will be evident that it will produce 

 the more mechanical effect, when you consider that there are 

 constantly particles of rock disengaged from the sides of the 

 valley and falling upon the surface of the ice and penetrating 

 under the ice, and finally down to the rock over which the ice 

 moves, so that the under surface of the ice, which rests upon 

 the rock, is in the end changed into a rasp, — studded all over 

 with pebbles of all sizes, which are immovably set in the ice. 

 When under the glacier, I have seen fragments of rock one, 

 two, and three feet thick, set in the ice, immovably, and pebbles, 

 of the size of your fist down to small grains of sand, all set in 

 the ice. These fragments would form, then, a part of the under 

 surface of the glacier. Now, the whole mass moves forward, 

 and conceive what a rasp it is ! Passing over rocks of the 

 greatest hardness, there will be, among these fragments of rock 

 set in the ice, some fragment or other which will be at least as 

 hard, if not harder than the rocks over which it moves, and the 

 result is, that in the end the whole surface of the rock is 

 abraded to an extraordinary extent, and while the minor parti- 

 cles polish these surfaces which are abraded by the larger 

 materials, the larger materials make scratches, grooves, and 



