Ch. V.] PRIMARY SCHISTOSE ROCKS. 89 



and, according to M. Brochant, never contains talc : he 

 states, however, that in some places its felspar is decomposed, 

 producing kaolin, or china-clay; and it is, therefore, very 

 possible, that these masses of granite are traversed by beds 

 or layers of protogine, as in Cornwall. This circumstance 

 was, probably, overlooked by this geologist ; for he does not 

 appear to have been aware, that granitic masses, as we have 

 already seen, are made up of various distinct rocks : as he 

 states, that the granite of other countries is almost without 

 any intermixture, and does not contain any subordinate rock. 



M. Brochant was not able to discover the junction of the 

 true granite with the talcose rocks of the Alps ; but in Cor- 

 sica, which appears to be a continuation of this talcose form- 

 ation, the nature of this connection is better developed. 



M. Gueymard's * account of this island is accompanied by 

 a section, drawn from Ajaccio, through Corte, to Ponte di 

 Golo. The lowest part of the range next Ajaccio is an 

 alternation of granite and eurite : proceeding towards the 

 interior, granite next predominates ; but the highest part of 

 the range is composed of eurite, protogine, and hornblende 

 rocks, alternating with gneiss and mica-slate, which gradually 

 give place to protogine, associated with talc-schist and lime- 

 stone ; and these are lastly succeeded by serpentine, talc-schist, 

 and similar rocks in which magnesian minerals prevail. 



The details furnished on this subject are not so copious or 

 particular, as the interesting nature of this section seemed to 

 demand. It may, however, be gathered from them, that the 

 beds of granite and eurite are contemporaneous. The 

 granite is also intersected by hornblende-rock and green- 

 stone, in the form both of beds and of veins. These rocks 

 are sometimes disposed in certain directions ; but, at other 

 times, they traverse the rock without any regular order. 

 The substance of these veins is often so intimately connected 

 with the rock which encloses them, that they both appear to 

 be of the same age. The granite of the ridge is associated 



* Annales des Mines, tome 9. p. 123. 



