1855.] SHARPE ELEVATION OF THE ALPS. Ill 



de Talefre, in which the Jardin stands, is also more than 9000 feet 

 above the sea. But the ice prevents our ascertaining with any 

 accuracy the exact height at which the change in the steepness of 

 the rocks takes place. 



These deep indentations at the heads of valleys are not due to the 

 streams which flow down them, for their action tends to equalize the 

 slope of their beds : they must owe their origin to the action of 

 waves beating for a long period against the rock. To ascertain 

 whether the waters producing such effects were those of lakes or of 

 the sea, we have only to compare the levels to which they reached in 

 different valleys : if the same levels were only found in lateral valleys 

 connected with one main valley, we might attribute their production 

 to the waters of a lake : but when the same levels are found in 

 valleys which have no connexion with one another, or which lie on 

 the opposite sides of mountain-chains, we must refer their excavation 

 to the waves of the sea. 



The latter is the case with the valleys of the Alps : the head of 

 the valley of Urnerboden, which is connected by the Linth with the 

 Rhine, is 4730 feet above the sea : Hauderes at the head of the 

 Valley of Herens stands at 4763 feet, and Ayer at the head of the 

 Valley of Annivier at 4776 feet ; these two latter valleys drain into the 

 Rhone : the Valley of Visp on the north side of Monte Rosa ends at 

 Zermatt, at 5410 feet; that of Gressonay on the south of Monte 

 Rosa ends near La Trinite at 5455 feet above the sea. From these 

 and other instances, which will be given in a Table, we learn with 

 certainty that the final excavation of these alpine valleys to their 

 present levels was done by the sea. It is not at present necessary to 

 consider what causes produced the cracks which enabled the sea to 

 penetrate so deeply into the flanks of the mountains, nor what 

 was their condition in the earlier geological periods, as I am only 

 treating of those later agencies to which the valleys owe their pre- 

 sent forms. 



Coupling the conclusion, that the sea was the agent of excavation 

 of the alpine valleys, with the sudden changes of level previously 

 mentioned at p. 110, and with the different elevations above the sea 

 at which we find the valleys terminate, we learn a similar result to 

 that which we have already obtained from observing the lines of 

 erosion on the mountain sides, — that the elevation of the Alps out of 

 the sea has taken place by numerous steps or comparative starts, 

 after each of which was a period of rest long enough to allow the 

 waves to leave a permanent record of their action ; and that through- 

 out Switzerland the whole chain was equally elevated, or as nearly so 

 as this method of observation will allow us to judge of. 



The measurements on which my comparisons are founded are 

 principally derived either from the *' Hypsometric de la Suisse " of 

 my friend M. Ziegler, or from the figures on the Map of Switzerland 

 published by the Federal Government, under the direction of General 

 Dufour ; a few are reduced from my own observations by the ane- 



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