400 



the amount of the mud mixed up with it. Small stems of herbaceous 

 plants or grass are sometimes found through this sinter. Where the 

 sand predominates the black mass looks like the fine quartz sand and 

 peat mud which may be seen mingled in the bed of a mountain 

 stream. In some cases the sand is consolidated into a very friable sand- 

 stone-like mass. On a specimen of the latter exhibited to the Academy 

 are a number of cubical crystals of galena, the upper faces of which are 

 nearly one square centimetre in size. These crystals consist of thin 

 shells of galena filled up with the brown coal. The galena on the 

 surface of the calc sinter found in the neighbourhood of the brown coal 

 is also intimately mixed up with that substance. The formation of 

 crystals of galena around the brown coal proves beyond all doubt that 

 the deposition of this part of the galena was posterior to the brown 

 coal. The whole vein is clearly of very modern origin, and formed by 

 the filling in of a fissure by matters borne mechanically, as well as 

 in solution, by water into it. But what makes this perfectly certain is, 

 the occurrence of small pieces of wood in the brown coal band. One 

 of the proprietors of the mine, himself a practical miner, and who 

 obligingly conducted me during three or four hours through the work- 

 ings, showed me a piece of coniferous wood several inches long which 

 he found in it. The bits which I observed here end there were 

 extremely small. But more important still is the occurrence of Mam- 

 malian bones in it, of which I am fortunately able to exhibit a piece of 

 one to the Academy. This bone is quite black from the action of the car- 

 boniferous matter, and contains some lead, due, no doubt, to the water 

 containing lead in solution, and by which the vein was mineralized. 

 The quantity of lead is very small, however — there not having been the 

 same favourable conditions for effecting an interchange between the 

 lead and the calcium of the bone, as in the case of the bones con- 

 taining zincic phosphate from the Dolores cave in the valley of Udias 

 in Spain above alluded to. 



Some time before my visit a good many bones had been found at 

 the Albertsgrube ; they were presented to the University of Bonn. 

 Herr von Dechen mentions this fact, as well as the occurrence of the 

 brown coal, in his " Orographisch Geognostische Uebersicht des Begie- 

 rungs Bezirks Aachen," which is a model of what a geological 

 account of a district, written for practical purposes, ought to be. He 

 there states that the bones belonged to a small species of Hippopotamos. 

 I have not seen any other account of those important fossils. 



Among the specimens from the same mine exhibited to the Aca- 

 demy are two others of considerable interest. One is a specimen 

 of stalactitic pyrites, which is as truly the result of deposition from 

 solution as any stalactite of a carbonate I have ever seen. The other is 

 a rolled chalk flint found in the yellow clay forming the principal ma- 

 trix or material of the lode. This chalk flint, and perhaps a good deal 

 of the clay, comes from the denudation of the cretaceous rocks to the 

 north and west. It may be worth mentioning that there is a considerable 

 deposit of soft brown coal to the eastward ; others of the same kind 



