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



lignite deposit is separable. Professor Noggerath mentions* two instances 

 at Friesdorf ; in the one the tree was seven feet in diameter, and from the 

 beds it penetrated must have been about ten feet high ; in the other the tree 

 was eleven feet thick, but how high could not be ascertained. At Zisselsmaar, 

 on the western side of the plateau, an upright mass of root and stem, of four 

 feet in length, was found f. 1 do not, however, mention these instances as 

 any proof of the trees being in the situation in which they grew, for if they 

 were floated, the heavy root might keep them in an erect position, and the 

 rarity of the occurrence is a strong presumption against the idea. 



The wood is sometimes so fresh, so little changed, as to have been used at 

 Viernich for timbers in the mines|. Pyrites is of frequent occurrence in all 

 the beds; and sometimes, as at Friesdorf and Holtorf, wood, in which the 

 texture is preserved, is highly charged with a granular carbonate of iron. A 

 specimen which accompanies this paper is a portion of a tree which I found 

 in a thick bed of lignite at Friesdorf; it was about four feet long, and a foot 

 and a half in diameter. The interior was converted into carbonate of iron 

 to the almost total disappearance of the woody texture, but this last was still 

 entire on the outside, where the iron was in the state of a yellow oxide. I 

 have mentioned, p. 446, that I found a portion of wood highly charged with 

 oxide of iron in the basaltic tuff of Siegburg; and it is important to remark, 

 with reference to the relative age of the brown-coal formation, and the vol- 

 canic eruption of Siegburg, that in addition to this fact I found a specimen of 

 bituminized wood in the basaltic tuff identical in appearance with a specimen 

 which I obtained from the brown-coal beds at Geistinger Busch. 



M. Von Dechen mentions that at Lieblar a lignite is found with a thin 

 powdery coating of amber. From the smell which this coal gives out when 

 burnt, the workmen call it edeler Weihrauch, frankincense. 



D. Organic Remains of the Brown-Coal Formation. 



These consist of vegetables, fish, insects, and reptiles : no shells of any sort 

 have ever been found, except in one particular spot, which I shall afterwards 

 notice; and no remains of quadrupeds, except in two very doubtful cases§. 



a. Remains of Vegetables. 



The brown-coal or lignite beds consist of wood and of leaves, and wood and impressions of leaves 

 are also found in the siliceous and argillaceous beds of the formation. As the woods occur in 



* Beschreihung der Braunkohlen Ablagerung auf dem Putzberge, in Von Moll's Jahrbuch, 

 vol. iii. Nuremberg, 1815. 



t Von Dechen, uti supra. + Ibid. ' § See Appendix V. p. 473. 



