262 A. V. Jennings — The Landwasser and Landqiiart. 



the river which then occupied the Pratigau, and was eroding its 

 source more rapidly than the ancient Landwasser could deepen its 

 bed. The result was that the latter was cut into by the former, and 

 its waters, with those of its upper tributaries, diverted into the 

 channel of the pirate stream. 



This theory has, I believe, been accepted by geologists in general 

 both in Switzerland and elsewhere. It has been incorporated by 

 Professor Tarnuzzer in his revised edition of Theobald's " Natur- 

 bilder aus der Ehjitischen Alpen," and it has been made widely 

 known to English readers by its inclusion in Sir John Lubbock's 

 "Scenery of Switzerland."^ 



It may seem rash to question a view put forward by so high 

 an authority and so strongly supported ; but as I have already to 

 some extent committed myself to an opinion on the subject,- it is 

 perhaps both justifiable and advisable that I should point out the 

 considerations which, during several months' study of the district, 

 have seemed to me to weigh against its too ready acceptation. 



The conditions which, according to the hypothesis, existed before 

 the diversion of the ancient ' Landwasser ' are shown in Fig. 1. 

 Even at first sight there seems here something different from 

 the usual type of river origin. There is an absence of the 

 tree-like structure, of the oblique convergence of tributaries that one 

 associates with the upper waters of a drainage system, while the 

 northward trend of the main feeders from the east seems distinctly 

 exceptional. 



Leaving these difficulties aside, however, for the present, and 

 observing the sources from which the river would have been 

 supplied, it is evident that the ancient ' Landwasser ' must have 

 possessed a current of considerable volume and great erosive power. 

 The present Landwasser, fed from the mountains of the Scaletta and 

 Ducan districts, is no mean excavating; agent in the Frauenkirch- 

 Filisur valley, but its predecessor would have had in addition the 

 whole force of the ' Upper Landquart,' the drainage of the snow 

 and icefields of the great Silvretta group. We may therefore be 

 reasonably sure that such a river would be rapidly deepening its 

 channel and tending to add to the relative height of its western wall. 

 The question then arises as to the nature of the stream on the 

 other side of this barrier, and whether it is likely to have had the 

 erosive force requisite even to keep pace with its powerful neigh- 

 bour. It is difficult to imagine that such can have been the case. 

 The lower Landquart is supplied by numerous streams from the side 

 valleys of the Pratigau, but these enter it approximately at right 

 angles from north or south, and their representatives at that time 

 could have taken no part in the denudation of the transverse 

 cliff-like outcrops at the head of the system. When the rock ridge 

 stretched across from the Madrishorn to the Casanna the head waters 

 of the Landquart would have been only the little rivulets rising 

 on the western face of the ridge of itself. The Landquart between 

 Kloaters and Serneus owes its existence, according to the theory 



1 London, 1898, p. 190. 2 Quart, Journ. Geol. See, vol. liy ; August, 1898. 



