Professor Favre oti the Geology of the German Tyrol. 85 



have counted more than ten beds of dolomitic limestone, se- 

 parated by as many strata of pyroxenic tufa. Has there not 

 evidently been a contemporaneous formation between the 

 plutonic and sedimentary I'ock ? 



On a geological inspection of the country, it seems as if we 

 had left the Alps, and have been suddenly transported into 

 the region of extinct volcanoes in the centre of Sicily. Ana- 

 logous alternations are seen above Colfosco. 



The ravines which intersect the great plateau of the Seis- 

 ser-Alp, disclose to our view spilites with beautiful zeolites, 

 and the surface of this plateau is strewed with masses of true 

 dolomites containing oysters (j), beautiful remains of polypi 

 and stalks of encrinites.* The position of these dolomites 

 indicates that they are the remains of the denudation which 

 has formed the plain of the Seisser-Alp. 



These pyi'oxenous porphyries, and the rocks depending on 

 them, appear to be completely wanting to the north of the 

 central chain. 



The dolomite of the Tyrol, like that of Switzerland, occurs 

 in two positions ; \st, It is found in the mass accompanying 

 rocks more or less crystalline, such as the argillo-talcose 

 slates of which we have spoken ; in general this dolomite is 

 in the neighbourhood of rocks really plutonic. 2d, It consti- 

 tutes great masses, and forms almost of itself the two latei'al 

 chains of the Austrian Alps. These mountains are distinctly 

 stratified. It is sufficient to have seen the great mass of the 

 Schlerns, from Castelruth or the cemetery of Layen, or still 

 better, the more imposing mass of Kreuzkogl from Colfosco, 

 to be convinced that their stratification is very nearly hori- 

 zontal. However, in the chain of the north, as in that of the 

 south, the beds are more or less turned up against the cen- 

 tral chain, a circumstance which confirms what we have said 

 respecting the coi*respondence of these two chains. 



I know not at what period in the history of the globe the 

 eruptions of melaphyres have ceased to take place. Some 



* M. Morlot points out corals in the dolomite of the Seisser-Alp; M. lior- 

 trand Geslin has found other fossils in the volcanic tufa of this locality (Jiullc- 

 tin de la Societi Ocoloiji'jue de France, First .Scries, iv., p. 8.) 



