88 THE CANADIAN NATURALIST. [Dec. 



replaced by those belts of gneiss which accompany the quartz 

 ridge of the Pfahl; and belong to the red variety or Bojian 

 gneiss. The grey gneiss strata of the Danube might therefore be 

 supposed to be older than this red gneiss, which from its relations 

 in the district to the N.W., between Cham and Weiden, I had 

 regarded as itself the more ancient formation. But the litholooical 

 characters of the grey Danubian gneiss are opposed to this view, 

 since this rock not only presents a general resemblance to the 

 gneiss formation of Bodenmais, which without doubt is directly 

 overlaid by the mica-schist of the mountains of Ossa, thus shewing 

 it to be the newer gneiss ; but exhibits a repetition of the minor 

 features which characterize the gneiss district of Bodenmais. We 

 find in the Danubian gneiss that same abundant dissemination of 

 dichroite, which gives rise to the typical dichroite-gneiss of 

 Bodenmais, with nearly the same mineral associations in both 

 cases. On the Danube, also, interstratified beds of hornblende- 

 rock (at Hals near Passau), of serpentine (at Steinhag), and of 

 pyrites (at Kelberg, and many points along the Danube), occur, as 

 in the north. On the other hand, the graphite which abounds in 

 the gneiss of Passau is not wanting at Bodenmais or Tischenreuth. 

 The interstratified syenites and syenitic granites are, in like manner, 

 common to all these districts ; those near Passau being, however, 

 richer in easily decomposed minerals, such as porcelain-spar 

 (scapolite) and calcspar, are more subject to decomposition, and 

 form the parent rock of the famous porcelain clays of the region. 



These resemblances lead me to refer the Danubian gneiss, 

 notwithstanding its apparent stratigraphical inferiority to the red 

 gneiss, to the newer or Hercynian formation ; and to explain its 

 apparently abnormal relations by assuming a fault running along 

 the strike from N.W. to S.E., through which the older gneiss of 

 the Pf hal is brought up, and seems to overlie the younger. 



We shall then regard the whole of the gneissic strata character- 

 ized by dichroite, which extend on the Danube from Passau to 

 Linz, as equivalent to the Hercynian gneiss of Bodenmais, and 

 designate it as the Danubian gneiss. We may here call attention 

 to the abundance of graphitic beds in it, as also to the occurrence 

 of porcelain clay, and of beds of iron pyrites and magnetic pyrites. 

 If it is true (as maintained by Dr. Sterry Hunt) that all graphite 

 owes its origin to organic matters, we must suppose the existence 

 of a primordial region peculiarly rich in organic life ; since 

 graphite occurs here in almost all the strata, and in some places in 



