Mr. Horner on the Geology of the Environs of Bonn. 461 



argillaceous earth, nearly 32 of carbonate of lime, a trace of magnesia, and it was coloured by iron 

 and manganese. 



In the immediate vicinity of the primary mountains it has a somewhat different character, being 

 more sandy, and containing mica. 



The loess does not contain what can properly be called petrifactions, but a vast number of cal- 

 cined land-shells of living species, more usually in the ujiper than in the lower parts of the deposit, 

 and they seem to belong to particular horizontal beds. There have been found near Heidelberg 

 the following species : Helix pomatia, H. nemoralis, H. hortensis, H. hispida, H. ericetorum, Bu- 

 limus radiatus, B. luhrkus, Lymneus ovatus. Some years ago, the lower part of an elephant's tusk 

 was found near Weinheim, at an elevation of 100 feet above the Rhine, and some fragments of 

 elephants' grinders had been previously found at a little distance from the same spot. 



It is found lying on granite, porphyry, red sandstone, muschelkalk, keuper, and lias, and near 

 Oppenheim on grobkalk (calcaire grossier). 



The greatest elevation at which I have seen loess in the district described 

 in this paper is near Erpel^ above Orsberg, where it lies upon the brown-coal 

 formation, a height which is fully 400 feet above the Rhine* ; and it occurs, 

 at about 200 feet high, near Steinsbusch, above Honnef. 



A very extensive deposit of it may be seen at the Bruckersberg, near Rhondorf, immediately south 

 of the Drachenfels, where it forms an irregular mass from three to twenty-five feet thick, and covers 

 trachyte and grauwacke, as represented in the wood-cut, p. 440. It is found at Quegstein in the 

 valley of Konigswinter, covering trachyte tuff, and near Paffroth and Ober DoUendorf, on the slope 

 of the Petersberg, covering grauwacke. Between Ober DoUendorf and Haisterbach it lies upon 

 grauwacke, covering the summit of a ridge over which the road passes, in the side of the valley 

 leading to the Stenzelberg, and at Roth Kreuz, covering trachyte tuff. It is found in the narrow 

 valley which opens at Ober Cassel, and covering basalt at a considerable elevation on the Raben- 

 lei. It occurs also, to the depth of fourteen feet, near Utweiler, covering basalt. These are the 

 places where I have seen it on the right bank of the Rhine ; but it is met with, no doubt, in many 

 others. On the left bank a narrow ridge of it runs in a south-east direction from Bonn for about 

 three miles ; and it is seen in the high bank of the river, covering the gravel of the Rhine plain, 

 the surface of which is deeply channelled, the loess filling up the furrows. It is seen on the north- 

 western slope of the Kreuzberg, in the valley between the Kreuzberg and Venusberg; in a valley 

 behind Godesberg, near Marienforst ; to a considerable extent near Lannesdorf, where very deep 

 clefts are cut in it ; and it skirts the northern and eastern sides of the volcano of the Roderberg. 

 Above Rolandseck there is a quarry of grauwacke, and upon the ends of the elevated strata of 

 that rock lies gravel covered by loess. The basaltic columns in the quarry opposite to Unkel are 

 covered by it at a very great height above the river, and where it is nearest to the basalt it con- 

 tains rounded fragments of that rock. It is here, as elsewhere, an unstratified mass, which seems 

 to have filled up deep furrows and irregularities of the preexisting surface. The absence of all 

 signs of stratification is universal in this district. At Unkel it contains a considerable quantity of 

 calcareous concretions. 



* Dr. Hibbert says that at Monrepos, in the neighbourhood of Neuwied, about ten miles south 

 of this spot, and on the same side of the river, loess occurs at a height of 600 feet above the Rhine ; 

 — History of Extinct Volcanos, &c., p. 205. 



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