328 ON THE IGNEOUS METAMORPHOSIS [Oh. XIV. 



through in the line of section." * "I spent some weeks," says 

 Bakewell," almost close to the Jungfrau mountain, in the 

 canton of Berne, and studied its structure with particular 

 attention; and I have no hesitation in expressing a decided 

 opinion that the section of M. Studer, representing two cone- 

 shaped masses of limestone penetrating the granitic gneiss 

 near the summit, is fallacious. The part represented as 

 penetrated by the limestone is concealed by a covering of 

 eternal snow." f 



If we might be permitted to venture an opinion on the 

 appearances at the Jungfrau, founded on the descriptions of 

 the above-mentioned geologists, we should say that they are 

 perfectly analogous to the gneiss formations of Scotland, 

 Norway, and other countries. This gneiss abounds in mag- 

 nesian minerals belonging to the talcose formation, which is 

 often characterised by the peculiar granitic rock called 

 protogine : it is generally lamellar, but in some parts massive, 

 and there presents irregular concretions and veins of granite ; 

 so that, according to the proportion of these parts, the mass 

 oscillates between granite and gneiss, though the latter pre- 

 vails. The adjacent limestone abounds in talc and other 

 minerals of this nature, and sometimes, by the intimate union 

 of magnesia, it becomes dolomite ; but the latter is not always 

 in contact with the gneiss, so, as in the case of the dolomites 

 of the Tyrol in contact with augite porphyry ; it cannot be 

 attributed to the influence of the accompanying rock on 

 common limestone whilst in a state of ignition. Now, this 

 crystalline limestone is the same as often occurs within gneiss, 

 it only differs in position ; and is in like manner subject to 

 the same interference of veins or layers of gneiss, either 

 lamellar or granitic. That this limestone graduates into the 

 secondary rocks of a calcareous nature, so that it is difficult 

 to say where the one begins and the other ends, is only in 



* Geological Manual, 8vo. p. 457. 



f Introduction to Geology, fourth edition, p. J01. 



