M. Fournet's Besearchea on the Geology of the Alps. 99 



perature, is, no doubt, most remarkable. The author, how- 

 ever, does not stop here ; because this transformation has 

 been for a long time demonstrated geologically and chemi- 

 cally; but he considers the formation of garnets, and ido- 

 crases, which are developed in the same circumstances as 

 the saccharoidal limestone. In truth, according to the nu- 

 merous indications given by M. Fournet, almost everywhere 

 this limestone is accompanied with idocrase, and the forma- 

 tion at Martigny is only one proof more of the law to which 

 the formation of this latter mineral is subject. 



We know that M. Mitscherlich has obtained garnet arti- 

 ficially, and that idocrase, as well as another crystallization 

 of the same kind, has been found by MM. Hausmann and 

 Bertheir, in sm el ting-houses. The garnet and idocrase are 

 nothing else, according to many mineralogists, than the same 

 substance appearing under two different forms. However 

 this may be, there is no ground for separating these two 

 species, in respect to their formation. It is evident that they 

 are formed when there are siliceous rocks in presence of 

 calcareous rocks, in suitable circumstances of temperature 

 and pressure. 



These considerations, according to M. Fournet, are of in- 

 terest in regard to [the study of metalliferous deposits, by 

 establishing the influence of matalliferous veins on their walls, 

 a study which is of the highest importance with respect to 

 its practical and industrial bearings.* 



^ome Bemarks on the High Temperature in the United Mines, 

 By Robert Were Fox.t 



The temperature of some of the deeper parts of the United 

 Mines has long been observed to be remarkably high ; and it 

 has greatly increased with the increasing depth of the ex- 

 cavations. 



* Biblioth. Univers. de Genev. Supplement, No. 6, p. 203. 



t Read, 3d Septembei* 1846, to the Royal Cornwall Polytechnic Society. 



