Ixxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



valleys and on the mountain-sides, which appeared to indicate the 

 action of the sea at a comparatively recent period. The object of 

 his paper, " On the last elevation of the Alps, with notices of the 

 height at which the sea has left traces of its action on their sides," 

 is to describe the phsenomena themselves, and to explain the probable 

 causes by which they have been produced. Mr. Sharpe endeavours 

 to show, that after the alpine region had assumed its present form, 

 and the existing valleys had been excavated, the whole country was 

 submerged below the level of 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 mountain-sides, which are 

 still visible. The effects thus produced are described under three 

 heads. 1st. — The erosion of the mountain -sides in certain regular 

 and definite lines, above which they rise into rugged peaks in striking 

 contrast with the smoother forms below. This physical feature 

 had already been observed by Hugi and others, although attributed 

 to a different agency. Mr. Sharpe shows that throughout Switzer- 

 land these lines of erosion occur at three distinct levels, viz. 4500, 

 7500, and 9000 English feet above the sea ; he points out their 

 occurrence in different valleys having no regular communication with 

 each other, and argues that no action but that of water could have 

 produced a uniformity of level over such an extensive area, and that 

 a long period of time was necessary to form such deep indentations 

 on the mountain-sides. 



2nd. — The sudden increase 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 time at that height. A table was given 

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

 valleys, at various altitudes ; this shows a remarkable correspond- 

 ence of level between the excavation of the valleys and the lines of 

 erosion at 4500 and 7500 feet, but the ice and snow in the upper 

 valleys prevent all observations with regard to the highest line at 

 9000 feet. 



3rd. — Mr. Sharpe considers the terraces of alluvium in the 

 valleys, 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 remarkable correspondence 

 is shown to have existed between the height above the sea of terraces 

 in valleys which have no connection with each other, and of terraces 

 in some valleys with the heads of other valleys. 



All these effects might have been produced by a sea surrounding 

 the Alps, but cannot be explained by any other means ; 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 described by Mr. Sharpe 

 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 



