GEOLOGY. 215 



the time, as if the entire face of a cliff had fallen outwards, producing 

 the first great crash, and had afterwards rolled over as I have described. 

 This action of the frost does not cease in winter, inasmuch as it is im- 

 possible for the Matterhorn to be entirely covered with snow. Less 

 precipitous mountains may be entirely covered during winter, and if 

 they do not then actually gain height, the wear and tear at least is sus- 

 pended in their case. It is impossible that agencies so powerful as 

 these can be continually at work without producing some visible alter- 

 ation in the form of the mountain, and I was not surprised on the last 

 attempt to find many places very much changed. The ledges, for in- 

 stance, which are traversed below the Col are becoming difficult from 

 breaking away, and in many other places I noticed great alterations. 

 We arrive, therefore, at the conclusion that, although such snow peaks 

 as Mont Blanc may in the course of ages grow higher, the Matterhorn 

 must decrease in height. Whether the action of frost is sufficient to 

 account entirely for the separation of the peak of the Matterhorn from 

 the ranges of which it is part, may be doubtful ; it is, however, a fact 

 worthy of notice, that the southern aretes of the mountain, those on 

 which the combined action of the sun in melting and cold in freezing 

 is most powerful, are crenellated in a most extraordinary manner, 

 while the northern faces are comparatively smooth and unworn. Not 

 only is it so in the case of the Matterhorn, but also in that of the Dent 

 d'Erron, and many other rocky peaks among the first-class mountains 

 of the Alps. 



CONFORMATION OF THE ALPS. 



Prof. Tyndall, in a paper in the Philosophical Magazine, No. 161, 

 arrives at the following conclusions, after having, during the last seven 

 summers, viewed the Alps from many commanding points : 



It is, then, perfectly certain that all this mountain region was held 

 by ice, enormous as to mass, and in incessant motion. That such an 

 agent was competent to plough out the Alpine valleys cannot, I think, 

 be doubted ; while the fact that during the ages which must have elapsed 

 since its disappearance the ordinary denuding action of the atmosphere 

 has been unable, in most cases, to obliterate even the superficial traces 

 of the glaciers, suggests the incompetence of that action to produce the 

 same effect. That the glaciers have been the real excavators, seems 

 to me far more probable than the supposition that they merely filled 

 valleys which had been previously formed by water denudation. In- 

 deed, the choice lies between these two suppositions : shall we assume 

 that the glaciers filled valleys which were previously formed by what 

 would undoubtedly be a weaker agent ? or shall we conclude that they 

 have been the excavators which have furrowed the uplifted land with 

 the valleys which now intersect it ? I do not hesitate to accept the 

 latter view ; and this view will carry us still further. According to it 

 the glacier is essentially self-destructive. The more deeply it ploughs 

 the surface of the earth, the more must it retreat. Let the present 

 Alpine valleys be filled to the level of the adjacent ridges, and vast 

 glaciers would again start into existence ; but every one of these val- 

 leys is a kind of furnace which sends draughts of hot air up to the 

 heights, and thus effectually prevents the formation of ice. While 

 standing on the summit of the Grauhaupt a week or two ago, I was 



