8 GLACIAL AND SURFACE GEOLOGY OF THE PACIFIC COAST. 



the glacier is the joint result of ice and water action, and much of that which 

 is done under the ice by water could be done, and is so, on an immense 

 scale, equally well without the ice. There are, it is true, some geologists so 

 prejudiced in flivor of glacial erosion, if the expression may be allowed, as to 

 claim that all fine detrital material is the result of ice-action. Some even 

 go so far as to say that without glaciers we could have had no soil, an idea 

 which leads to the inference that the entire earth must at some former time 

 have been covered with ice, since there is no zone or region where deep 

 deposits of finely coniminuted material are not found. Indeed, the mass 

 of facts which oppose any such theory as this is so great, that it is not 

 necessary to occupy time in discussing the matter. 



Ice, per se, has no erosive power. If the glacier were frozen to its bottom, 

 find could then be made to move, it would, no doubt, tear away the project- 

 ing edges of the rock masses on which it was resting; but it is a joerfectly 

 well established fact that glaciers are not frozen to their beds. The glacier 

 is snow which has been converted into ice by water, and without the latter 

 the former cannot come into existence. The ice being permeated with 

 water acts as a flexible body, taken as a whole, although in its parts it is 

 not. By virtue of this condition it adapts itself to the channel through 

 which it has to pass, bends ai'ound angular projections, rises over elevations, 

 turns sharp corners, narrows and widens again and again, and comports itself, 

 in short, just as we should expect a soft flexible body to do in passing over a 

 hard inflexible one. The proof of this statement is to be found in the ex- 

 amination of any extensive mountain chain which has been formerly jiartly 

 occupied by glaciers and from which they have since disappeared. No chain 

 offers a better chance for an investigation of this kind than does the Sierra 

 Nevada, as will be seen further on in this chapter. The recent shrinking of 

 the Alpine glaciers has laid bare large surfaces which but a few years ago 

 were covered with ice, and where the condition of the surface imder the 

 former glacier may be studied with the greatest fiicility. Nowhere, in any 

 such region denuded of its former icy covering, will it be found that the 

 glacier has had any power to cut through an obstacle so as to form a channel 

 with vertical, or nearly vertical sides, as water often does. The whole form 

 of the Alpine valleys is proof of this, for all will admit that if the ice which 

 once filled many of these up to a higher level than it now does had such an 

 erosive energy as is attributed to it by some geologists the section of those 

 valleys must have been quite different from what it is at present. Had ice 



