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THE GEOLOGIST. 



One of Sir Roderick's principal objects in exploring this region was to 

 convince himself, if possible, of the existence of a fundamental gneiss of as 

 high antiquity as the Laurentian rocks of Canada and Scotland, and of 

 the truth of M. Giimbel's view of the distinction of the gneiss into older 

 and younger ; but, after a survey of the whole district, he was unable to 

 distinguish any order of superposition between its two members, the so- 

 called younger gneiss, in one extensive tract near the Danube, dipping, 

 according to M. Giimbel, under the older ; and their variable strike ren- 

 dered it as difficult to judge by that character as by their dip, its direction 

 in some places being at right angles to what it is in others. For the pre- 

 sent, therefore, though with the greatest respect for the labours of M. 

 Giimbel, he considers the gneiss-rocks to constitute one great series, it 

 being certain that the two varieties are not separated by any different in- 

 tervening sediment, as in the north-west of Scotland. 



A clear illustration of the whole ascending succession is afforded by the 

 order of superposition exhibited in M. Giimbel's section from Hof to Selb, 

 a distance of about seven or eight miles. Gneiss is there seen resting 

 against granite, and passing up into mica-slate underlying concretionary, 

 quartzose, chloritic masses, which form the base of the Urthonschiefer. 

 This primary clay-slate is followed by quartzites and black roofing-slate, 

 in the latter of which the fossils of the Silurian primordial zone of Bar- 

 rande occur, and ultimately by other Silurian, Devonian, and Lower Car- 

 boniferous strata in conformable succession, the latter passing conformably 

 upwards into mountain limestone, which is shown to be quite unconform- 

 able to the Upper Carboniferous of Germany. In the remaining north- 

 west portion of the section the strata are repeated in inverted succession, 

 having been dislocated by the intrusion of igneous rocks. 



Sir Roderick next adverted to the question of the parallelism of the 

 Silurian rocks of Bohemia with those of Britain, pointing out that the 

 Austrian Geological Survey, whose new map he exhibited, had adopted, 

 for this occasion only, the colours used by the Geological Survey of Great 

 Britain ; and he stated his belief that too close a parallelism between the 

 subformations had been attempted, and that the parallelism of such large 

 groups only as Lower and Upper Silurian, as proposed by Barrande, with 

 a possible interpolation of " Middle Silurian," could be maintained. 



The author then contrasted the absence of Devonian and Lower Car- 

 boniferous rocks, coupled with the full development of Lower and Upper 

 Silurian life, in Bohemia with the fuller and unbroken succession in 

 Bavaria. He concluded by observing that the conformable succession of 

 strata in Bavaria and other tracts shows the existence of beds which 

 bridge over the gaps, represented by unconformities, that occur in the 

 British series ; and pointedly adverted to the two facts, that the enormous 

 thickness of clay-slate beneath the primordial zone, though unaltered 

 over large areas, had afforded no vestiges of life, and that the transitional 

 groups of strata uniting two great systems had not afforded in any country 

 a link connecting one class of animals with another. 



2. " Notice of a Section at Mocktree." By E. Lightbody, Esq. 



The lower portion of this section was stated to exhibit the Aymcshy 

 limestone, with its characteristic honeycomb structure, and showing at its 

 upper limit a basin-shaped depression containing beds of sandy clay depo- 

 sited parallel to its sides, ami unconformable to the Ayniestry limestone, 

 though at a little distance from the trough this unconformity disappears. 

 These argillaceous beds contain Lower Ludlow fossils, though they over- 

 lie the Aymestry limestone; the author consequently proposes that the 

 la Iter term should no longer be used as a separate subdivision. He also 



