149 



the people. I also sought in vain for subterra- 

 nean plants, those cryptogamous plants of the 

 family of the usneacece, which we sometimes 

 find fixed on the stalactites, as ivy on our walls, 

 at the moment when we penetrate for the first 

 time into a lateral grotto *. 



The caverns in the mountains of gypsum of- 

 ten contain mephitic emanations and deleteri- 

 ous gassesf\ It is not the sulphat of lime, that 

 acts on the atmospheric air, but the clay slight- 

 ly mixed with carbon, and the fetid limestone, 

 which are so often mingled with the gypsum. 

 We cannot yet decide, whether the swinestone 

 act as a hydrosulphuret, or by means of a bitu- 

 minous principle J. It's property of absorbing 



* Thus the lichen tophicola was discovered when the line 

 cavern of Roseninueller in Franconia was first opened. 

 (Humb., Ueber die Grubenwetter, p. 39.) The cavity con- 

 taining the lichen was closed on all sides by enormous 

 masses of stalactites. This example is not favorable to the 

 opinion of some natural philosophers, who think, that the 

 subterranean plants, described by Scopoli, Hoffmann, and 

 myself, are cryptogamiae of our forests, accidentally conveyed 

 into mines with the timber, employed in working them, and 

 disfigured by the effects of blanching. 



t Freiesleben, Vol. ii, p. 189. 



% lb., vol. ii, p. 16 — 22. The stinkstein is constantly of a 

 blackish brown colour ; it is only by decomposition that it 

 becomes white, after having acted on the surrounding air. 

 The stinkstein, which is of secondary formation, must not be 

 confounded with a primitive granular limestone, very white, 

 of the island of Thasos, which emits when scraped a smell 



