Mr. D. Sharpe on the last Elevation of the Alps. 85 



2. " On the last Elevation of the Alps, with notices of the Heights 

 at which the Sea has left traces of its action on their sides." By 

 Daniel Sharpe, Esq., F.R.S. & F.G.S. 



The object of this paper is to show that after the Alps had 

 assumed their present form, the whole region was submerged below 

 the sea, and stood 9000 feet lower than at present ; and that it then 

 rose out of the sea by a succession of unequal steps, separated by 

 long intervals of time, during which the waves produced impressions 

 on the sides of the Alps which are still visible. These effects are 

 traced out under three heads : 1st. The erosion of the sides of the 

 mountains, producing rounded forms which extend up to definite 

 lines, above which the mountains rise into rugged peaks, in striking 

 contrast with the smoother forms below. This change of form had 

 been observed by Hugi, who referred it to different composition of 

 the rocks ; by Agassiz and Desor, who seeing that Hugi's view was 

 incorrect, explained it b)'^ the action of moving ice, to which they 

 arbitrarily assigned a definite upper limit; and lastly by Prof. J. 

 Forbes, who has pointed out similar phsenomena in Norway at 1500 

 or 2000 feet elevation. Mr. Sharpe shows that throughout Switzer- 

 land these lines of erosion occur at three definite levels of 4800, 

 7500, and 9000 English feet above the sea, and he argues that no 

 action but that of water could have produced a uniformity of level 

 over so large an area, and that it required a long period of time to 

 have formed such deep indentations of the mountain sides. 



2nd. The sudden change of steepness which occurs at the head of 

 every Alpine valley is assumed to be due to the excavating action of 

 water, standing for a long period at that height : and a table is given 

 of the elevation above the sea of the heads of between forty and 

 fifty valleys, at various altitudes, which shows a correspondence of 

 level between valleys on the opposite sides of the Alps, and between 

 the excavation of several valleys and the lines of erosion at 4800 and 

 7500 feet; while the ice and snow in the higher valleys prevent a 

 comparison with the highest line at 9000 feet. 



3rd. The terraces of alluvium in the valleys are considered, in 

 accordance with the opinion of Mr. Darwin, Mr. Yates, and others, 

 to have been formed by detritus carried down into water standing at 

 the level of the head of the terrace. The elevation of many of these 

 terraces is given, and a correspondence is shown of the height above 

 the sea of terraces in valleys which have no connexion with one 

 another, and of terraces in some valleys with the heads of other 

 valleys. 



All these effects might be produced by a sea surrounding the 

 Alps, and cannot be otherwise explained ; and the level of this sea 

 being assumed to have been constant, the Alps must have been rising 

 out of the waters while these operations were going on. The period 

 of this, their last elevation, is stated to have been after the Tertiary 

 epoch ; and a great part of the vast accumulations of sand, gravel, 

 and rounded blocks which are seen in the valleys of the Alps and 

 covering the lowlands of Switzerland are considered to have been 



