189 



PROCEEDINGS 



ROYAL SOCIETY OF EDINBURGH. 



VOL. II. 1848-9. No. 33. 



Sixty-Seventh Session. 



Monday, -it/i December 1848. 



Sir T. MAKDOUGALL BRISBANE, Bart., in the Chair. 



The following Communications were read : — 



I. Geological Notes on the Valleys of the Rhine and Rhone. 

 By Robert Chambers, F.R.S.E. 



The principal part of this paper was devoted to a description of 

 alluvial terraces, as seen along the banks of the Rhine at Bonn, 

 Mainz, and Basle, and in the valley of the Arve, the well-known tri- 

 butary of the Rhone. These terraces, which rise high above the 

 reach of the present river, yet slope in the same direction. The in- 

 termediate hollow or trough in which the river runs, has evidently been 

 cut out of what was at first an entire sloping sheet of detrital matter, 

 fiUbg the valley from side to side up to a certain height. At the 

 lower part of the Arve valley, the detrital matter has been discharged 

 across the valley of the Rhone, so as to form a barrier for the Lake 

 of Geneva. 



At Vevay, on this lake, there is a short side valley, containing 

 tiers of sloping terraces, which have been called ancient moraines, 

 but are set down in this paper as deltas or river alluvia, marking the 

 stages of the subsidence of a recipient body of water. The chief of 

 these terraces are respectively about 165 and 442 feet above the 

 present level of the lake. 



To illustrate the formation of these terraces and deltas, reference 

 was made to the recently-drained Lake of Lungern, in Unterwalden 

 The inpour of mountain-streamlets into such lakes is over a slop- 

 ing sheet of detritus, extending from the base of the mountains to 



VOL. II. .>} 



