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



sand containing much iron, so that the general colour of the gravel is yellow, 

 very like that round London. I have never found any other fragments than 

 those above named in the places where I have examined the gravel, but 

 Professor Noggerath informs me that he has found in it trachyte, transition 

 limestone, and hunter sandstein. To trace the history of this vast accumu- 

 lation of gravel would be an interesting inquiry ; but it would require a 

 very extensive series of observations, a minute acquaintance with the rocks 

 of the Upper Rhine and the adjoining lands, and an accurate knowledge of 

 the forms and levels of the country, before any satisfactory conclusions could 

 be attained. 



The gravel often lies immediately upon the lignite deposit, but frequently 

 a bed of clay is interposed. The following section is constructed from the 

 description given by Professor Noggerath of the beds at Putzber^ 



.•g. 



Ft. In. 



1 . Loam and marl (loess) of an average depth of 2 



2. Gravel 13 



3. Sandy loam 6 



4. Earthy lignite and bituminized wood, lower part mixed with clay 3 



5. Gray bituminous clay, bituminized wood, and clay iron stone. . . 4 



6. Earthy lignite and bituminized wood 6 



7. Bituminous brown clay 1 



8. Earthy lignite and bituminized wood 6 



9. Gray plastic clay '6 



10. Earthy lignite and bituminized wood 8 '> 



1 1 . Highly bituminous and pyritous clay 5 



12. Leafy mass ; chiefly bituminized stems, branches and leaves . . 16 



13. Bituminized wood 1 6 



14. Same as No. 10 3 



15. Same as No. 12 2 6 



16. Same as No. 10. and 14 1 6 



17. Same as No. 12. and 15 2 6 



18. Same as No. 9., bored into to the depth of 24 



79 6 

 Of which the lignite beds constitute 24 6 



In most places the lignite rests upon clay, and below that come the sand- 

 stone and loose sand, the latter being generally the lowest. At Roisdorf, near 

 Bonn, the sandstone is covered by bituminous clay ; and at Prechem, near 

 Briihl, thick beds of clay and lignite lie upon loose sand. In many places 

 the sandstone occupies the surface, so that the clay and lignite have 

 either never been deposited upon it, or have been carried away by sub- 



