150 Geological Notes on the 



The valley of the Rhine is composed, in the neighbourhood 

 of Cologne and Bonn, of a wide alluvial plain, bordered by 

 low eminences. The plain is composed of sand chiefly, but 

 partly of a small gravel. A little way back, it is bounded by 

 a low cliff, at the top of which commences a second alluvial 

 plain, also of considerable breadth. At Bonn, the plain 

 nearest the river is more elevated above it, — probably not 

 less than 45 feet ; and the rise to the second plain is also 

 greater, perhaps 20 feet. These objects are conspicuous from 

 the railway, which, on leaving the upper plain, has to pro- 

 ceed for some way along a high embankment. 



On emerging from the contracted part of the valley, where 

 the Rhinegau terminates, we see great benches of ground 

 a little Avay back, much like those terraces which have else- 

 where been set down as ancient sea-margins. The chateau 

 of Johannisberg is seated upon one of these. Similar terraces 

 appe§,r between Bieberich and Wiesbaden, and behind Mainz ; 

 one behind Mainz is exceedingly well defined, and, perhaps, 

 may be found to correspond in level with one on the opposite 

 side of the river, which I observed, near Cassel, to be com- 

 posed of nearly pure sand. 



At Basle, where the surface of the river (if I rightly un- 

 derstand Keller's map), is 863 English feet above the level 

 of the sea, the usual low plain adjacent to the river is backed 

 by a higher alluvial plain, with a steep cliff intervening. 

 This is well seen to the east of the city, on the road to Lu- 

 cerne. The upper plain may be 70 feet above the lower. 

 The arrangement has an unusually interesting appearance at 

 the confluence of the Birs with the Rhine, the side river 

 having made a transverse cut in the upper plain, so as to 

 form in it a little valley bounded by flat-topped cliffs. 



In ascending the eminent ground which intervenes between 

 Basle and Schliengen, in the grand duchy of Baden, we pass 

 over terraces of considerably greater height. These are the 

 highest alluvial terraces which I have had an opportunity of 

 seeing in the immediate valley of the Rhine. 



Passing to the valley of the Rhone, the side vale of the 

 Arve presents such alluvia on a very great scale. This tur- 

 bulent stream, as is well known, descends from the skirts of 



