1863.] MURCHISON BAVARIA AND BOHEMIA. 359 



and N.E., and seem fairly to pass under the other gneiss. My im- 

 pression, therefore, is that, on the Danube, the masses of gneiss are 

 in their normal position, and form simply one of the lower members 

 of the great gneissic series of Bohemia, the diversified mineral struc- 

 ture of which requires no detailed description by me. 



M. Giimbel shows that a remarkable band of quartz-rock, seven- 

 teen German miles in length, called the " Pfahl" (C, fig. 1), is asso- 

 ciated with his lower gneiss. But, again, this rock, as well as the 

 gneiss to which it is subordinate, strikes from E.S.E. to W.N.W., 

 and is perfectly parallel to the associated gneiss of the Danube. 



I am the more disposed to view all the gneissose rocks of Bohemia 

 and Bavaria as belonging to one great series, by examining M. Giim- 

 bel's sketch-map, by which it appears that, where his older gneiss 

 folds round and strikes to the north, there are signs of great distor- 

 tion of the strike where the strata meet the southern end of the 

 granitic masses of the Eichtelgebirge. There, both his varieties of 

 gneiss bend round with very devious strikes, but each more or less 

 conforming to the granitic nucleus. It appears to me, therefore, that 

 the older and newer gneiss of this region form, as before said, one 

 great series only, and are not to be distinguished, like the fundamental 

 or Laurentian gneiss and the younger or micaceous gneiss of the 

 Highlands of Scotland, by a total unconformity, and by being sepa- 

 rated from each other by a great intervening deposit, as is the case in 

 Scotland. In point of fact, the so-called younger gneiss of Scotland 

 is simply altered Silurian, whilst in Bohemia and Bavaria the one 

 gneiss is followed by another gneiss without any separating deposit. 



In Bohemia and Bavaria we have, as before shown, many proofs 

 that the age of the old slaty and crystalline rocks cannot be deter- 

 mined by any partial examination of their strike ; for in one tract we 

 find the very same rocks ranging N.W. to S.E., and in another 

 trending from N.E. to S.W. 



In viewing these gneiss-rocks for the present as one great series, 

 I do so with some hesitation, and with every respect for the labours 

 of M. Giimbel, who has with infinite pains followed these crystalline 

 rocks into all their sinuosities, and may have better reason than my- 

 self for distinguishing the lower or, what he calls, the Bavarian gneiss 

 from that named by him Hercynian gneiss. I must also here re- 

 mark, that if all the true gneissic rocks of Bavaria be united, they 

 may well, from their colossal dimensions, stand in the place of the 

 Laurentian gneiss of Canada and of the north-west of Scotland. The 

 clear evidence which exists of the interpolation of a vast thickness 

 of sedimentary formations in which no fossils have been found, be- 

 tween the great gneissose series and the lowest Silurian rock, is a 

 good reason for believing that the gneiss of Bohemia and Bavaria is 

 truly the representative of the Laurentian or fundamental gneiss. 



General ascending order of the Mocks. — A clear illustration of the 

 inference previously arrived at as regards the fundamental gneiss is 

 afforded, indeed, by the regular ascending series of rocks from the 

 gneiss of the Fichtelgebirge at Selb to Hof in Bavaria, as drawn by 

 M. Giimbel in the annexed instructive sections. One of these sec- 



2b2 



