308 Charles Maelaren, Esq., oh the 



P, Mountain Plan-y-Beuf — where traces exist at 5445 feet. 



d, Martigny — height 1480 feet above the sea. 



e. The bottom of the valley at Monthey. 



G, Lake of Geneva, 1150 feet above the sea. 



k, Hill where Chalet of Playau stands — traces at 3760 feet. 



N, Lake of Neuchatel 1340 feet. 



/, Mount Jura — traces at 3444 feet. 



The dotted outline from m to k indicates the position of the moun- 

 tains forming the eastern boundary of the valley d e ; m is the Dent 

 de Morcles, 8940 French feet in height ; n, the hills north-east from 

 Lausanne. 



The parallel lines in the figure indicate the position of the rock 

 formations. At/ on Mount Jura the limestone dips south-east at 

 a pretty high angle. From N to G the Molasse, a sandstone, varies 

 much, but has generally a slight dip to the south-east ; from G to 

 t the rocks consist of limestones and slates of different ages from the 

 chalk to the Palaeozoic series, with masses of granite or gneiss 

 (marked by closer lines) intercalated at P and d. The stratified 

 rocks here are highly inclined, and sometimes vertical. The figure 

 is intended merely to convey a general idea of the form of the sur- 

 face over which the glacier glided, and the lines of, P/, do not in- 

 dicate the true inclination of its surface, but one very much greater. 

 The line o / dips at an angle of 5°, while the true dip of a line 

 passing from the one position to the other is only 40'. 



Slope of the Ancient Glacier. 



Would the inclination before mentioned of 22' or one foot in 156, 

 suffice to generate progressive motion in a glacier ? — Positive data 

 for the solution of this question do not exist, but there are facts 

 from which inferences may be drawn by analogy. To any one who 

 knows nothing more of glaciers than what the eye tells, it may seem 

 strange to say that these masses of ice are plastic, and have a mo- 

 tion like that of a semi-fluid body, such as tar or wet mortar. The 

 lower end of a glacier is generally a precipice of ice, ten, twenty, 

 or thirty feet high ; and, in some cases, where it emerges from the 

 valley, and projects into the plain, it has the form of a mound, very 

 steep, both on the sides and front. On the upper surface are seen 

 fissures two or three yards wide, and fifty or a hundred long, with 

 vertical sides, and the lower end often presents galleries many yards 

 in length, with upright walls, and large enough to permit a man to 

 walk in thenu To admit the plasticity of a body of this description 

 seems somewhat like renouncing the testimony of our senses. That 

 such, however, is really the constitution of glacier ice, has been 

 proved in Professor Forbes's able and well-known " Travels in the 

 Alps," to which the reader is referred for ample details. He de- 

 scribes glacier ice as traversed by an infinity of capillary fissures, 

 and forming, in fact, a " congeries of tightly-wedged polyhedrons," 



