98 Prof. Sedgwick and Mr. Murchison on the 



sensibly, and become of earthy texture. — This system is sur- 

 mounted by the great, gray, bare precipices of lower Alpine 

 limestone many thousand feet in thickness. It appears, there- 

 fore, that in the structure of the lowest beds of the Alpine 

 limestone there is, to say the least of it, a very strong analogy 

 between certain parts- of the great northern and southern 

 zones. 



Dark, bituminous, slaty beds are not, however, confined to 

 the base of the series, but in some instances, for example in 

 the Seefeld pass, compose whole mountain masses. In con- 

 sequence of the very complex dislocations of that part of the 

 calcareous zone, it is difficult to ascertain the exact place of 

 the bituminous ichthyolites of Seefeld. But placing the do- 

 lomites of Mittenwald as the mineralogical centre, we think 

 that the Seefeld schist is considerably inferior to the salife- 

 rous deposits of Hall, and that some of the beds of the 

 system descend far down into the lower Alpine limestone. 



It would be useless for us, after all that has been written 

 on the subject, to attempt any general description of the do- 

 lomites of the Alps. The metalliferous hills of Bleiberg are 

 chiefly composed of this variety of rock, arranged in great 

 irregular beds dipping south at an angle of 70°. The lead 

 ore of these hills is arranged in masses which appeared to us 

 parallel to the beds of limestone: but our persevering and 

 skilful young friends, Messrs. J. and 11. Taylor (who had 

 previously visited the mines and examined them with great 

 care) have since convinced us that the ore is deposited in true 

 veins; which, though they for considerable spaces range 

 parallel to the strata, cut obliquely through them at certain 

 intervals. In the dolomitic beds of the hill above the village, 

 are a few casts of shells and other obscure fossils; and we 

 were happy to recognize among them two or three specimens 

 of the Gryphaea incurva. Immediately behind the village are 

 some beds of shale and limestone (fire-marble), with many 

 fossils; among which are the celebrated iridescent Ammonites, 

 which Dr. Buckland, we believe, identified with the fossils of 

 the lias. Considering, then, that in this single locality we 

 have grauwacke with beds of limestone containing transition 

 fossils,, surmounted by red sandstone and gypseous marls; 

 and this latter series again surmounted by fetid limestone, do- 

 lomites, &c. containing the Gryphaea incurva, and by other 

 beds containing Ammonites and Belemnites — there can, we 

 think, be no doubt to what part of the secondary series we 

 should refer the lowest division of the lower Alpine limestone 

 as it is developed in the Bleiberg Hills. 



Notwithstanding the magnificent scale of the sections in the 



Salzburg 



