Mr Lyell on the Loamij Deposit of the Rhine, 113 



Bonn ♦. The circumstance must, in part, be ascribed to the 

 rapid degradation of loess, which is constantly going on througli- 

 out the valleys drained by the Rhine and its tributaries, but it 

 also shews that the waste of other rocks in the same districts 

 produces a sediment very similar in its nature to loess. 



It is well known that the loess rests on the gravel of the plain 

 of the Rhine. This superposition is well seen on the left bank 

 of that river, about a mile above Bonn, where the loess fills up 

 hollows in the gravel, and presents the appearance represented 

 in the annexed sketch. 



y^Y\ 



I conceive, that in this instance, small rills or torijents must 

 first have furrowed the upper beds of gravel, leaving small 

 trenches with vertical and occasionally overhanging walls, and 

 then the waters holding loamy sediment in suspension must 

 tranquilly have overflowed the spot and thrown down the loess 

 until it first filled up the cavities, and then formed a continuous 

 overlying mass. 



The next subject to which my attention was called on my 

 way from Bonn to Mayence, was the relations of the loess to 

 some of the more modern volcanic formations of the Lower 

 Eifel. 

 ' The volcanic hill called the Roderberg, situated on the left 

 bank of the Rhine, about four miles above Bonn, and imme- 

 diately opposite the celebrated Drachenfels, is well known. From 

 the perfect form of the crater at its summit, and the appearance 

 of its scori^R, it has always been supposed to owe its origin to 

 one of the most modern eruptions of this country. In the mid- 



• See Proceedings of Geological Society 1834. 

 VOL. XVII. NO. XXXIII. JULY 1834. H 



