1855.] SHARPE — ELEVATION OF THE ALPS. 107 



I feel that my best observations may, with one or two exceptions, 

 be 100 or perhaps 200 feet wrong, while the worst can, I think, 

 never have an error exceeding 500 feet. The admission of the pro- 

 bability of such errors may stagger the faith of my readers, but the 

 want of absolute accuracy will be found to be compensated by the 

 number of observations which harmonize sufficiently to restore confi- 

 dence in them. 



There are many mountains in the Alps on which I failed to trace 

 any distinct line of erosion : but, when we recollect how long a period 

 has elapsed since the ocean reached to the flanks of the Alps, during 

 which time the surface of the rocks has been crumbling away from 

 the action of the atmosphere, I think it more remarkable that the 

 sea-levels are still to be traced at all on their sides, than that these 

 traces should have been frequently obliterated. 



In pointing out the various lines of erosion which I was able to 

 trace on the sides of the Alps, I will begin with the highest, and 

 describe them in order from above downwards. The heights are all 

 reduced to English feet. 



First Line of JErosioriy 9000 to 9300 feet above the sea. — In 

 taking a general view of Mont Blanc from the Croix de Flegere, I 

 estimated the line of erosion to be above 9000 feet. From the Col 

 de Balme, I estimated it at somewhat above 9000 feet ; and from the 

 Col de la Seigne, which, being higher, brought me within a distance 

 in which the eye may be trusted, I placed it between 8900 and 9400 

 feet. The average between these observations is about 9000 feet. 



On the Riffelberg, a good observation already mentioned, p. 106, 

 fixed the line of erosion at between 9000 and 9100 feet. 



The top of the Stilvio Pass, 2814 metres above the sea, is about 

 200 feet above the upper limit of erosion, which gives us 9000 feet 

 for the height of the line of erosion : this measure may be trusted, as 

 in ascending to above the line I had a good opportunity of noting it 

 with tolerable accuracy. The rocks are limestone and dolomite, 

 belonging to the triassic series. 



In all the three districts mentioned above, the effects of the erosion 

 are very strongly marked on the sides of the mountains, producing a 

 deeply indented line round them ; this indentation represents the 

 amount of rock which has been removed by the waves, and proves to 

 us the great length of time that the sea must have stood at the level 

 in question. 



A second and less-strongly marked line of erosion may be traced 

 round the lower shoulders of the Mont Blanc Range, a little above 

 the Col de Balme : I did not find it sufficiently well defined to note 

 its altitude accurately ; but it probably coincides with the Second 

 Line which I am about to mention. 



Second Line of Erosion^ about 7500 feet above the sea. — This 

 line may be traced over a great part of the centre of Switzerland, as 

 strongly marked on the mountain sides as the First Line, and in- 

 dicating an equally long period of the action of the waves at its level. 

 It attracted the attention of Professor J. Forbes, and led to his 



