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may have also existed, which are now denuded. In connexion with the 

 occurrence of this chalk flint, I may notice an interesting lode at the 

 Brenessel Stockwerk, in the same district. The lode in question lies 

 at a considerable depth in dolomitic limestone, and consists — first, of a 

 band of blackish clay ; then of a band of reddish clay, from one to 

 two feet thick, containing small pieces of galena and cerussite. The 

 blackish clay appears to be merely this clay mixed with brown coal or 

 dense peat mud, like the substance found at Albertsgrube. On the 

 reddish clay lies a layer of white quartz sand. This lode resembles in 

 many ways the dykes of clay and white sand, sometimes associated with 

 a band of hematite of considerable thickness, which are found in the 

 carboniferous limestone of Ireland. There seems very little doubt that 

 the sand and clay were washed into a fissure in the same manner as the 

 brown coal, chalk, flint, and bones of the Albertsgrube. 



The occurrence of pebbles, and other evidence of aqueous ac- 

 tion in veins, have not attracted the attention they ought, chiefly 

 because, on the one hand, the pebbles were found by practical 

 miners, who did not see their value, and next, because the sub- 

 limation theory so affected the views of geologists, that they 

 heeded not the evidence around them in every mine of aqueous 

 action. Among the specimens which are exhibited to the Aca- 

 demy is a rolled pebble, found at the depth of about forty metres 

 in the Dreikonigszug mine, on the Potzberg, near Kussel, in Rhe- 

 nish Bavaria. This mine, which is worked in a kind of sandstone, 

 permeated by cinnabar or mercuric sulphide, and yielding from 0*005 to 

 O'Ol of mercury, has been carried down to a considerable depth. More 

 than forty years ago, when M. Brard visited it, it had attained a depth 

 of two hundred metres. The pebble is quartz, and is coated with 

 crystallized cinnabar, so that the mineral was formed after the pebble 

 had fallen, or been washed into the fissure in the sandstone. 



