14 Rev. W. D.Conybeare on a Geological Map of [Jan. 



In this map also a double zone of primitive limestone is repre- 

 sented pursuing its course with undeviating regularity on either 

 side the axis of the chain. In the Tyrol, the secondary lime- 

 stones encroach more on the primitive chains, which, though 

 still of considerable height, are tame in their features, and are 

 more than rivalled in elevation, and far surpassed in grandeur, 

 by the oolitic ranges. 



The steepest escarpment of the Alps is uniformly towards the 

 Italian side. 



(K.) Chains surrounding the Basin of Bohemia, including the 

 Bohemer Wa/d, the Thuringer Wald, the Erzegebirge, the 

 Reisengeberge, and the Sudeleugeberge. 



The central line of the Alps may, perhaps, be considered as 

 prolonged by the primitive chain, which passes from Presburg to 

 join the Carpathians ; but on the NW of this line is a vast group 

 of ancient chains, extending between Vienna and Dresden, com- 

 pletely enclosing the sources of the Elbe, or the great basin of 

 Bohemia, and thus forming, as it were, a detached ring in front 

 of the general system. The Bohemer Wald, or branches con- 

 nected with it, closes this basin on the SW and SE, ranging 

 round the sources of the Elbe. On the NW border, clayslate 

 alternating with greenstone rocks prevails ; but in the rest of 

 the chain, granitic rocks predominate. 



The Fichtelgeberge connects this side of the Boherner Wald 

 with the Thuringer Wald : it exhibits granitic summits skirted 

 by clayslate and greenstone. The slate district is very extensive 

 on the N. 



The Thuringerwald (a branch extending from the NW of this 

 primitive circle) exhibits granite, gneiss, and micaslate, skirted 

 on the S by the overlying deposits of rothe todteliegende and 

 cupriferous slaty limestone (our new red conglomerate, and 

 magnesian limestone series). On the N, porphyritic rocks over- 

 lying those of the coal formation occur. 



que le gneis meme, entre Martigny et Saint-Maurice, que tons les singuliers poudingues 

 de la vallee de Trient jusqu'a. Valorsine, que les rochers de gneis entre Martigny et Saint- 

 Branchiez, appartiennent au terrain &e gratvwacke, et ne sontpas primitifs. Ces roches 

 se retrouvent dans tout le Valais, quoique sans poudingues." 



The slate of Glaris, containing fish and turtles, which has sometimes been considered 

 as transition, appears rather to belong to the secondary rocks. 



I am desirous to avail myself of this opportunity to correct an error I have inadver- 

 tently committed in quoting a statement of Dr. Mac Culloch's on a subject nearly con- 

 nected with this. In noticing his discovery of a calcareous formation containing organic 

 remains underlying the gneiss, I have hastily used the term gryphite limestone, but the 

 fossils observed were really orthoceratites: the whole sentence is also expressed too gene- 

 rally, and without sufficient precision. Instead of the brief clause " a gryphite lime- 

 stone underlying gneiss in one of the Hebrides," I ought to have written '• a limestone 

 formation underlying gneiss in Garvagh, the most northerly of the Hebrides, and in 

 the shores of Loch Eribol on the adjoining mainland, which at Eribol contains a subor- 

 dinate bed of calcareous sandstone, exhibiting traces of orthoceratites." The Doctor has 

 lit'le doubt that the associated beds of the limestone will also be found to contain similar 

 remains both at Eribol and in Garragh Island. 



