408 Geological Society. 



bonifcrous limestone, and on the other into tlie upper Silurian rocks, 

 M'ithoiit interruption, it ibllov s, that the Devonian system, as above 

 defined, is contemporaneous with, and the representative of, this old 

 red sandstone. 



§ 3. Chain of the Hartz. — Fichtelgcbii-ge, c^c. — The general strike 

 of this chain is nearly the same as in the provinces before described 

 (/. e. east-north-east), and therefore almost at right angles to the 

 prevailing direction of the chain, as laid down on a geological map. 

 The mineral structure and the fossils are also nearly the same, and 

 the numerous contortions throAV the same difficulties in the way of 

 determining the true order of superposition ; and these difficulties 

 are greatly increased by protruding masses of granite, which have 

 not only altered the structure of all the neighbouring rocks, but 

 literally broken the chain into fragments, several of which are 

 thrown into a reversed position. 



The igneous rocks of the region are stated to be of four kinds : 

 (1.) Trappean rocks in beds and protruding masses, nearly on the 

 line of strike ; (2.) Granite, sending veins into the older slates and 

 trappean rocks ; (3.) Quartziferous porphyry in masses and dykes, 

 idejitical in structure, and apparently in relation with the Elvans of 

 Cornwall ; (4-.) Trappean rocks (jnelaphyre, <S-c.), associated with the 

 Tothe todte liegende and coal-nieasurts on the south-eastern skirts of 

 the chain. 



Silurian fossils are found in several parts of the Hartz, but the authors 

 saw no rocks which they could compare with the central slates of the 

 Ardennes, or the oldest slates of the Rhine; but they give two sec- 

 tions which ascend into a higher system. The first is from Huli- 

 genstein to the neighbourhood of Clausthal, and appears to give the 

 following ascending order : 



(1.) Devonian limestone, well characterized by its fossils. 



(2.) A series of psammites and shales, with one or two species of 

 Possidonia. 



(3.) A series of coarse sandstones and grits, surmounted by 

 shales and psammites highly charged with plants, and mineralo- 

 gically resembling the Devon culm-beds. 



Plants are, however, found below the Devonian limestone, and 

 even thin bands of culm ; and the section is obscure : but if the in- 

 terpretation given to it be correct, a part of the country near Claus- 

 thal rises into the carboniferous series. 



Their next section commences with the limestone of Ebingerode 

 (on the south side of the Brocken mountain). The limestone 

 abounds with Devonian corals and other fossils, and some parts of 

 it cannot be distinguished from the lower limestone of Westphalia. 

 Other parts of it are pierced with trappean rocks and are overlaid by 

 ferriferous deposits ; in which respects, as well as in its fossils, it is 

 strictly analogous to the Devonian limestones of Dillenburg and the 

 Lahn. Again, the ferriferous bands are overlaid by black shale, 

 containing Kicscl schiefer, and (if we are not misinformed) contain- 

 ing Possidonia schist. The analogy presented with the uppermost 

 part of the Devonian series in Westphalia seems, therefore, perfect. 



