on the Hartz 273 



and Clapeyron have observed, numerous subordinate beds of 

 alum slate (ampelite), wlietstone slate, flinty slate, and 

 hornblende rocks of different kinds, as also numerous beds 

 of iron ore. Clay-stone porphyry (argilophyres) and other 

 porphyries are also known there, the relative position of 

 which does not always appear well determined ; yet some 

 certainly appear as beds included in the greywacke. We 

 should remark, among these last, one which is analogous to 

 the vert antique porphyry, and which occurs between Riibe- 

 land and Elbingerode, and another porphyritic rock, whose 

 paste is a mixture of compact whitish felspar and quartz, and 

 contains crystals of roseate felspar and hornblende. I have 

 observed this last rock forming the roof of the iron ore beds 

 of the environs of Elbingerode. The greywacke also con- 

 tains beds of limestone, many of which are altogether analo- 

 gous to the marbres campans. 



The transition limestone of the Hartz presents two con- 

 siderable independent masses. One situated at the western 

 extremity of the group, near the small town of Grund, con- 

 stitutes the Iberg and some neighbouring mountains. The 

 greywacke rests upon it, as may be seen by pits driven through 

 the greywacke to reach the iron ore worked in the lime- 

 stone. It should be remarked that the stratification of the 

 greywacke, round the limestone nucleus, is mantle shapedy 

 since the beds of greywacke and slate dip to the N.W., on 

 the western sides of the Iberg and the Bauerberg,^ striking 

 exception to the general dip of the Hartz. The other lime- 

 stone mass, situated in the environs of Riibeland, on the E. 

 of the Brocken, also occurs in some places beneath the 

 slates ; but it appears to form a very thick bed or parallel 

 mass, included between beds of greywacke. The limestone 

 of this formation appears almost exclusively composed of 

 madrepores, which only become visible from the decom- 

 position of the rock. Both masses contain caverns : two of 

 those in the environs of Riibeland are known by the names 

 of Baumanns hiihle and Biels hohle ; those of the Iberg, which 

 are less celebrated, but much more interesting, are partly 

 filled with iron ore. 



