434 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 4, 



and that again by finer schists (fig. 5, c). As, however, we could hear 

 of no Hmestone nor fossils in those masses, and had little time at our 

 disposal, we did not explore them to the edge of the chain, where 

 they are overlapped unconformably by some Upper Carboniferous 

 strata, the latter being covered by conglomerates of the Rothe-todte- 

 liegende. (See Trans. Geol. Soc. 2 ser. vol. vi. p. 295.) 



But whilst we thus recognized the existence of an Upper Silurian 

 rock in the limestone near Miigdesprung, we were unable to follow 

 it upwards to a junction with strata unequivocally Devonian, or 

 downwards to any other Silurian rocks. 



In fact, no sooner do we issue from that portion of the Selke 

 valley, in which for a very short space there is a connected and 

 ascending series, and proceed towards Gernrode and Blankenburg 

 on the north and west, and Alexis Baden on the west, than we meet 

 with much eruptive rock (fig. 5, g), principally " gabbro," green- 

 stone, hypersthene, and granite, all of which rising to considerable 

 heights cut off the sequence and exhibit on their flanks many ex- 

 amples of altered strata. (See Section fig. 5, a^.) 



Penetrated as the tract is by such eruptive rocks, and obscured in 

 great parts by wild woodlands, it is manifestly impracticable with 

 our present knowledge to affirm that the strata near Miigdesprung, 

 as exhibited in the Section fig. 5, are not overturned. The large 

 plants found in the flagstones are unlike anything ever detected in 

 Silurian rocks, and resemble Devonian, if not Lower Carboniferous 

 forms. Again, whilst the animal relics of the limestone are said to 

 approach most in character to Barrande's uppermost Silurian of 

 Bohemia, they make (according to Mr. Salter, who has examined 

 the specimens we have collected) a very near approach to Devonian, 

 and contain some species which are certainly of that age. 



Seeing the amount of protruded igneous rock to the west of these 

 strata of Miigdesprung, we must leave it to be ascertained by future 

 researches in this most dislocated tract, whether the flagstones of 

 Magdesprung are not of younger age than the limestone, and that 

 the whole series has been inverted. Such inversion would indeed 

 surprise no geologist who knows the Harz ; for on the northern flank 

 of the chain the Permian and Secondary rocks are occasionally seen 

 in overturned positions ; the younger strata underlying the older. 



If M. Adolf Roemer's first map be appealed to, we see in it a con- 

 firmation of this idea ; for, according to his view, the culm or Carbo- 

 niferous masses are usually interpolated between the chief eruptive 

 rocks and the Devonian and Silurian groups ! 



Other rocks containing Upper Silurian fossils have been discovered 

 in a very small patch or two only on the northern flank of the gra- 

 nitic axis of the Ross-Trappe near Ilsenburg, and particularly by 

 M. Jasche of the latter place. We visited one of the localities, called 

 Klosterholz, accompanied by that gentleman, and found there a small 

 portion of dark limestone, which had been formerly quarried for 

 mining purposes, on the side of a rivulet in the woodlands which 

 there slope rapidly from the chain. But no physical features of 

 other rocks are there visible. It is simply a boss of hard lime- 



