456 Prof. Buckhmd on the Structure of the Alps, [June, 



III. Elder Alpine Limestone. 



Magnesian IJmestone of England. — The thickness of this 

 formation in the Alps is very considerable, and we must refer to 

 it a large class of rocks which are placed by Brocchi, Charpen- 

 tier, and other writers, among transition limestones. Mr. Ebel 

 has lately proposed to call them by the name of Hochgebirgs 

 Kalkstein (high mountain limestone) from the great elevation 

 they usually attain. The limestone is here and there precisely of 

 the same character with the English magnesian limestone ; but 

 in general it is less abundantly charged with that earth than it is 

 with us, though it presents at intervals nearly all the varieties 

 that attend this formation in England and Germany. Its pre- 

 vailing character in the Alps is a dark compact limestone, not 

 easily distinguishable from the compact younger alpine lime- 

 stone without the aid of its occasional metallic contents, and of 

 the subordinate beds that occur in it : the latter are referrible to 

 the following strata of the magnesian hmestone formation that 

 are well-known in Germany. 



1. Zechstein. — Dark compact stratified limestone sometimes 

 much charged with silex, alumine, or bitumen. Localities : Ax- 

 enburg, on Lake Lucern, north border of Lake Wallenstadt, 

 Ischell salt mine in Saltzburg. 



2. Asche. — Dark grey limestone, of minute sandy grain, 

 rough to the touch, and decomposing to loose powder, resem- 

 bling ashes. Its most compact varieties are often split into 

 small angular fragments, which are reunited into an irregular 

 breccia. 



Localities : Pass of Guncles under Galanda Berg on the west 

 of Coire, in Switzerland. Keichenhall salt springs in Saltzburg. 



3. llouhwacke. — A brecciated limestone composed of an 

 agglutination of angular fragments of dolomite, not rolled, but 

 formed apparently during the consolidation of the compound 

 rock in which they are inclosed. The fragments are more 

 loaded with magnesia than the matrix in which they lie; they vary 

 in colour from yellow to red, have a pearly glimmering aspect, 

 and decompose spontaneously to a yellow powder, leaving small 

 angular cells ; the intercellular substance forms a hollow rugged 

 mass, to which the term rouhwache (roughstone) has been 

 applied in Germany. 



This variety is usually found near the deposits of salt and 

 gypsum, and also in the beds of asche and zechstein. 



Locahties : Bex Salt Mine. Leisigen on LakeThun. Weiss- 

 tannen, near Lake Wallenstadt. Mischell, near Trent, on the 

 Adige. All the Rock Salt Mines of Tyrol and Saltzburg. 



4. Rogenstein (Roestone). — An oolitic form of magnesian 

 limestone, well-known in the Thuringervald, and which has 

 often been mistaken for the English oolite, or Jura limestone, 

 but differs from it in being of much higher antiquity as well as 



