434 Mr. Horner on the Geology of the Environs of Bonn. 



work by Nose*, which was published in 1789, and, considering the time when 

 it was written, it possesses great merit, and evinces minuteness of obser- 

 vation. Professor Noggerathf of Bonn has described some of the more 

 remarkable features of the district, and Messrs. Von Oeynhausen and Von 

 DechenJ have given, in a periodical Journal, a general view of what Nose, 

 Noggerath, Steininger§, and others had written, adding many original ob- 

 servations ||. But to the geologists of England this remarkable district is little 

 known ; it is, however, particularly deserving of their attention, for, diver- 

 sified as is the mineral structure of the British isles, nothing analogous to 

 it occurs in them ; and it affords this further attraction, that the Siebenge- 

 birge and the neighbouring country of the Eifel are the nearest points to 

 England where volcanic phaenomena, at all approaching in character to those 

 of modern times, can be seen. Those who are desirous of studying, on the 

 spot, the effects of volcanic action, by availing themselves of the facilities of 

 steam navigation, may, with great ease, in six days from leaving London, 

 reach the Mosenberg in the Upper Eifel, and there stand by the side of a 

 stream of lava, and, although the fires have been long extinguished, on the 

 edge of a crater covered with cinders. Nor is it to be forgotten, that these 

 numerous objects of geological interest present themselves in a country 

 renowned for the charms of its natural scenery and historical associations. 



I have deposited in the museum of the Society a suite of 277 specimens in 

 illustration of this paper, with a descriptive catalogue. The accompanying 

 Map has been coloured in part from my own observations ; but as far as the 

 Siebengebirge are concerned, it is, with a few alterations which I have seen 

 occasion to introduce, a copy of one communicated to me by Professor 

 Noggerath, and which he kindly permitted me to make use of. In a coun- 

 try so covered with a luxuriant vegetation as this is, one cannot say that the 

 boundary linesof the different formations are exact1[,or that all the phaenomena 

 which bear upon the geological history of the country have been discovered ; 

 future observers will probably see reason to make alterations in these boun- 

 daries, and I have no doubt that much remains to reward further researches. 



From my learned friends Professors Goldfuss and Noggerath I derived 



* Orographische Briefe uher das Siebengebirge, &c., 2 vols. 4to, 

 y Das Gebirge in Rheinland-Westphalen, 4 vols., 1822 — 1826. 

 + Hertha, 12th vol., 1828. 



§ Die erloschenen Vulkane in der Eifel, und am Niederrheine, 1 vol. 8vo, 1820 ; and Neue Bei- 

 trdge zur Geschichte der Rheinischen Vulkane, 1821. 



Ij Professor Noggerath is now engaged in preparing a full account of the Siebengebirge. 

 ^ See Appendix II. p. 472. 



