76 Professor Favre on the Geology of the German Tyrol. 



These slates, so varied in character, are evidently mineral 

 masses which have been more or less altered by different 

 agents, among which we must rank an elevated temperature. 

 The proof of this action of heat is the following. These 

 slates, as we have mentioned, ai'e more or less crystal- 

 line ; now, it is in the most crystalline part that we find tlie 

 greatest number of those masses of saccaroidal or granu- 

 lar limestone, which, according to Hall's experiments, in- 

 dicate a powerful action of heat. These masses are dis- 

 posed in the argillo-talcose slate formations in large lenti- 

 cular masses and beds, parallel to the stratification.* In 

 general, these limestones are found at the lower part of 

 the stratified rocks, as, for example, at the northern ex- 

 tremity of Zemm-Thal, where the saccaroidal limestone is 

 slaty in contact with the gneiss, but compact, sonorous, and 

 breaking like glass, at a distance of ten or fifteen yai'ds. 



Other masses of saccaroidal limestone may be observed in 

 the Ziller-Thal. We have found the continuation of them, 

 first, to the west of the Brenner road, where the sections, pub- 

 lished in the Comptes rendus of the Montanistitche Verein 

 (1843), indicate that their beds have anon-conformable stra- 

 tification with the mica slate ; and, secondly, twenty leagues 

 more to the east of the same chain, at the picturesque pass 

 called Klam, at the entrance of the valley of Gastein, near 

 Lend. This section, narrow and deep, through which, not- 

 withstanding, the waters of this valley are discharged, has 

 not always existed, for the valley of Gastein presents all the 

 characters of an ancient lake. 



The rocks which form the Klam are white or greyish sacca- 

 roidal limestones, more or less charged with mica (talc V). 

 This limestone presents three very distinct appearances ; 

 l*^, Homogeneous or compact, although saccaroidal ; 2d, 

 Slaty and slightly grooved, the surface of the slates be- 

 ing faintly undulated ; ^d, Bacillary, that is to say, formed 



la Societe helvetique des Sciences- Natur., tome 1, p. 241, 1833.) Studer. (Me- 

 inoires de la Societe geologique de France, 2me Serie, t. i., p. 308.) 



* The saccaro'.d.'J limestones of Meran, which are so skilfully employed in 

 the workshops of it. Schwanthaler, at Munich, are probably found in the same 

 gcolOjjical position. 



