82 Professor Hausmann ore Metallurgical Phenomena 



where they are penetrated by a basaltic mass, as happens, foi 

 instance, on the Blaue Kuppe, near Eschwege; on the Pflaster- 

 i<aute, not far from Eisenach ; and at Wildenstein, near Bii- 

 dingen. The change in the sandstone seldom progresses so far 

 as to form a crystalline structure, as was found by me to take 

 place in stones procured from the wall of an extinguished blast 

 furnace on the Harz. The change in the sandstone may be 

 traced from the point where it possesses a granular structure, and 

 a yellow tint, to where if becomes a completely compact altered 

 grey mass ; and thence into a cellular crystalline mass, whose ca- 

 vities are furnished with small crystalline tables of a pearl-grey 

 colour, with a pearly lustre, and a distinct cleavage, and which, 

 before the blowpipe, may easily be melted to glass, accompanied 

 by some effervescence. The crystalline laminae have a resem- 

 blance to mica. This phenomenon is, in a geological respect, of 

 deep interest, inasmuch as it seems greatly to favour the conjec- 

 ture that has been started in modern times, of the possibility of 

 crystalline rocks being produced from conglomerates and sand- 

 stones under the influence of heat. Whether sandstones alone 

 have contributed materials to effect that transformation, or 

 potash perhaps from the ashes of coal been superadded, by 

 which the fusibility was augmented, and the formation of a 

 crystalline silicate promoted ; at all events, this phenomenon 

 may be considered analogous to the process that is found in 

 many conglomerates, and in many sandstones, where the heat 

 of masses that have ascended in a fused state has had influence 

 upon them. 



It was incidentally observed in the former part of this treatise, 

 that bodies which have been transformed into vapours by the heat 

 of melting furnaces, sometimes penetrate in this form into stones 

 andother masseswith which they come in contact. Inconsequence 

 of this circumstance, the qualities of the masses are sometimes 

 completely changed. The following facts deserve to be men- 

 tioned, as illustrations of this kind of transformation : — The 

 basesofthemeltingfurnacesin the Upper Harz silver-mines, con- 

 sisting of variegated sandstone, are sometimesentirely penetrated 

 with vapours of the oxide of lead, which communicates to the 

 sandstone a lemon-yellow colour. The quartz grains may still be 

 partly distinguished ; a silicate of the oxide of lead, however, 



