1855.] MURCHISON AND MORRIS THURINGERWALD. 421 



coarser beds, the dominant features of the formation, particularly of 

 its middle and upper members, are the so-called conglomerates. 

 These great bands, often of vast thickness, ought, strictly speaking, 

 to be termed breccias, particularly near Eisenach. For, whatever be 

 the included material, whether quartz rock, mica schist, old por- 

 phyry, granite, or grey wacke slate, the fragments are usually angular ; 

 none of them presenting the aspect of having been rolled on a beach 

 or rounded by the action of the waves. However these angular or 

 subangular pieces were accumulated, the impression left on the mind 

 of the observer is, that they were got together in a very rapid and 

 tumultuous manner. 



The movements, however, by which they were aggregated were 

 clearly suspended and repeated many times ; the intervals of qui- 

 escence allowing of those deposits of finely triturated red sand and 

 mud which alternate with the coarse and subangular breccia. In 

 the granitic breccia under the Wartzburg, it is curious to remark (as 

 pointed out to us by Professor Senft of Eisenach), that the included 

 granite fragments in one of the several courses which we observed to 

 alternate with beds of sand and shale have been derived from a rock 

 no longer visible in the chain of the Thiiringerwald, but which was 

 doubtless a mass once near at hand — probably just beneath the very 

 breccia that has been made out of it. It is a granite containing 

 pericline and black mica. 



These angular breccias and conglomerates, with their associated 

 sandstones, are of gigantic dimensions, and have been bored into in 

 fruitless searches after coal to a depth of about 2500 English feet ! 

 Their chief mineral characteristic is their intimate association with 

 huge masses of porphyry, some of which have manifestly been 

 emitted coincidently with the formation of the breccias. So intimate, 

 indeed, is the association, that here, as in many tracts of Germany, it 

 is occasionally most difficult to disentangle that which may be termed 

 a true eruptive rock from bands of breccia in which other fragments 

 of altered schistose and the older sedimentary rocks are mixed up. 

 This is peculiarly the case where the porphyritic matter has over- 

 flowed and has been extended horizontally. 



An examination of this chain proves, that the northern Thiiringer- 

 wald has been penetrated at almost countless points by porphyries of 

 various characters, and of which M. Credner distinguishes about six 

 varieties in the red or quartziferous porphyry alone. True mela- 

 phyre (or the so-called black porphyry) is also abundant. 



It would appear that rocks of igneous origin have penetrated this 

 chain from a very early period. Thus, in the Lower Silurian slates 

 we meet with greenstone, granite, and an ancient red porphyry, the 

 last-mentioned being in fact the rock whose fragments are jfound in 

 the Coal-measures and Rothe-todte-liegende. These old eruptive 

 masses are said by M. Credner to be limited to the Silurian and not 

 to enter into the Devonian strata, — a point on which we have not yet 

 satisfied ourselves. 



Hypersthene rocks are seen to rise through the Upper Carboniferous 

 layers and to have greatly altered them : but it is only on ascending 



