266 A. V. Jennings — The Landicasser and Landquart. 



(1) That tlie Landwasser was not running as at present when the 

 detrital fan opposite Frauenkirch accumulated, since a portion of. 

 that fan still exists on the west side of the valley, separated from 

 the main mass by a subsequent down-cutting. 



(2) That as the whole bed of the Upper Landwasser lies on 

 alluvial and detrital material its present course gives no indication of 

 the real contour of the rook-floor ; and the latter may, and probably 

 does, slope northward. 



(3) That a comparison of the slopes of the mountain sides at 

 a series of points along the Davos area also gives support to this 

 suggestion. 



(4) That the ice-movement in the district was certainly northward. 



(5) That solid rock in situ cannot be found on the Wolfgang- 

 Drusatch ridge, and that this feature in the landscape probably 

 consists entirely of moraine material, mainly ice-borne from the 

 Todtalp. 



The conclusions which I based on these observations were as 

 follows: — (1) That in Pre-Glacial times the Muela, the Dischma, 

 and perhaps the Sertig, flowed northward into the Landquart. 

 (2) That in Post -Glacial times the presence of the Wolfgang- 

 Drusatch mass and the detrital accumulation round Clavadel and 

 Frauenkirch — then, as I have shown, far greater than now — caused 

 the formation of a lake between these two points, probably with 

 an outflow over Wolfgang. (3) That in time the work of the 

 Landwasser below Fx-auenkirch, and perhaps of the Sertig also, so 

 weakened the southern dam as to cause an outflow of the lake in 

 that direction, carrying with it the waters of the Fluela and Dischma. 



In making these suggestions I did not fully realize the extent to 

 which they were connected with the whole question of the past 

 history of the rivers ; nor did it occur to me that some geologists 

 would be willing to accept the idea of the former northward flow of 

 the eastern tributaries, while still holding not only to Professor 

 Heim's view but also to a belief in a solid rock ridge between 

 Wolfgang and Drusatcha. I may, therefore, perhaps be allowed to 

 say something in support of the conclusions I then arrived at before 

 pointing out their bearing on the main question under consideration. 



It has been objected by some that the detrital accumulations 

 opposite Frauenkirch are mainly of a fluviatile character, and as 

 a whole are not of sufiiciently compact and massive character to 

 have held up the waters of a great lake. We have exposed here, 

 however, only what is pi-obably a fringe of lighter material round 

 the edges of a mass of coarser detritus. There are abundant 

 examples near Clavadel of large rock-fragments ice-borne down the 

 Sertig valley. It is also by no means necessary to suppose that the 

 southern dam was merely a transverse barrier at this point. It is very 

 probable that the whole valley was choked with debris as far south 

 as Monstein. The enormous thickness of detritus full of ice-borne 

 blocks which occurs at that village doubtless once crossed the 

 Landwasser valley and abutted against the western cliffs of the 

 Ziige. In the same way the banks and terraces of the Langmatter 



