1863.] MFRCHISON' BAVARIA AND BOHEMIA. 361 



tions, fig. 2, exhibits, in the space of about 7 or 8 miles, the 

 following ascending order of strata, arranged in conformable super- 

 position : — 



Gneiss (s) resting against granite (t), and, in this spot, near Selb, 

 having a superficial width of 3000 metres only, or about 10,000 

 English feet, though in Bohemia this thickness, as before 

 stated, is enormously increased. These strata of gneiss pass 

 upwards into 

 Mica-slate (r), occupying a surface of about 20,000 feet wide, and 

 all at very high angles of inclination. These beds, after one 

 or two undulations, plunge at an angle of 45° under 

 Chloritic, quartzose, concretionary masses (q), which form the 

 natural base of the vast thickness of the great mudstone 

 series to which the Germans assign the name of Urthon- 

 Schiefer (p), and which, with the underlying chloritic beds, has 

 here (to the S.E. of Behau) a thickness of 36,000 French 

 feet. 

 It is this grand and massive accumulation of primary clay-slate 

 (in which no fossils have yet been found, and to which M. Giimbel 

 assigns, in other tracts, a thickness of about 80,000 English feet) 

 which, with the underlying and more metamorphosed portions of it, 

 may be viewed as the German equivalent of the Cambrian rocks of 

 North Wales, as laid down in the maps executed by my predecessor 

 Sir Henry De la Beche and his associates. In some places this great 

 series of the " roches azoiques " of Barrande is a micaceous grey- 

 wacke, in others it contains quartzose and even pebbly beds, and is 

 often charged with lead-veins in quartzose matrices. In traversing 

 the wide tract around the town of Mies* in Bohemia, which is 

 occupied by this Thon-Schiefer, I was so much struck with its re- 

 semblance to those ordinary Silurian mudstones, or " rotch " of 

 South Wales, which have been affected by an imperfect cleavage, 

 that I could not avoid the reflection that, if fossils are ever to be 

 found in the strata which underlie the Primordial Silurian zone of 

 Barrande, this is a tract singularly favourable for an endeavour to 

 find them; for I can assert that much of this Urthon-Schiefer is 

 less altered or crystalline than many Silurian rocks of younger 

 age, which are charged with fossils f. Not wishing, however, to 

 dogmatize on this point, or to adhere blindly to my title-page of 

 ' Siluria,' in calling attention to what I still consider to be un- 

 assailed, " the oldest fossiliferous rocks and their foundations," I 

 simply invite all those who sustain theories against facts, hitherto 

 uncontradicted, to travel into the region now described, and many 

 others to which I could refer them, and try to discover fossils in 

 these quasi unaltered primary strata of mudstone. If they succeed, 



* This tract was described, in 1791, by Lindacher (see Barrande, Systeme 

 Silurien clu Centre de la Boheme, vol. i. p. 10). 



f On this head see a valuable memoir by Dr. Bigsby, " On the Organic Con- 

 tents of the Older Metamorphic Rocks," Edin. New Phil. Journ., Aprd 1863. 

 The author, citing well-known authorities, refers to sixty-four cases where or- 

 ganic remains have been observed in altered Palaeozoic rocks of different countries. 



