170 Prof. Tyndall on the Conformation of the Alps, 



example, the ridge from Monte Rosa over the Lyskamm and 

 Breithorn to the Matterhorn ; the upheaval of that ridge could 

 not possibly produce rents in the position now occupied by the 

 Val Tournanche, the Val d'Ayas, and the Val du Lys. The line 

 of strain would be parallel to these valleys, and hence the line 

 of fracture, if fracture at all occurred, across them. 



A sufficient consideration of the subject must, I think, result 

 in the conclusion already expressed, that a general elevation of 

 the land formerly existed, and must limit us to the question, " By 

 what agency has this land been scarred so as to exhibit the valleys 

 by which it is now intersected V These valleys are the tracks of 

 rivers, and have been manifestly formed with reference to the 

 discharge of the aqueous precipitations which occurred on the 

 heights. An eminent Swiss geologist, with whom I had an op- 

 portunity of conversing a week or two ago, called the Alpine 

 valleys " Auswaschungsthaler," valleys cut out by the action of 

 water. For some years an opposite conclusion has been gradu- 

 ally forcing itself upon me ; and this year I completed a chain of 

 evidence which leaves little doubt upon my mind that a mightier 

 excavator than mere water has been at work among the Alps, 

 and that the country owes its present conformation mainly to 

 the action of its ancient glaciers. 



It requires some time to realize the stupendous scale on which 

 the ancient ice has operated ; and were its traces less indubitable, 

 the judgment would halt before accepting a conclusion invol- 

 ving operations so vast as almost to appear fabulous. This year 

 I walked for the fifth time up the valley of Hasli, observing the 

 action of the ancient glacier upon its boundaries. A million 

 winters may have acted upon these scarred and fluted rocks, 

 and still the scars and the flutings are as distinct as if they had 

 been executed last year. We trace them down to the banks of 

 the Aar, a river which has been rushing for these ages through 

 the valley ; and the smallness of its operations must impress us 

 with the comparative feebleness of denudation by water. A 

 mighty glacier occupied the valley of the Rhone. I traced it all 

 along the valley to Martigny, a distance of more than 60 miles 

 from the end of the present Rhone glacier. Here, reinforced 

 from Mont Blanc, it ploughed its way towards the Lake of Geneva. 

 Near a station called D'Evionnaz, the roches moutonnees rise 

 above each other in heaps, and here, as in Haslithal, the polish- 

 ing comes down close to the level of the present Rhone, — thus 

 suggesting how comparatively small has been the action of the 

 river from the disappearance of the glacier to the present day. 



The same thought is continually forced upon the traveller on 

 the south side of the Alps, where the traces of ancient glacier 

 action are, if anything, more astonishing than on the north. Two 



