On the Paragenetic Relations of Minerals. 345 



The phenomena of the rock veins in the masses of granite 

 are rather complicated. 



These veins appear generally to have formed at the time 

 of crystallization of the granite ; their great richness in quartz 

 favours this opinion, it being the last mineral of the rock to 

 remain in a fluid state. 



The granite of the Vosges forms smaller eminences around 

 the bosses of the Ballons, and is itself covered by stratified 

 rocks, into which it graduates by insensible degrees. The 

 granite of the Ballons has evidently penetrated with violence 

 into the granite of the Vosges ; this is well seen at Meha- 

 champ. In some places the junction of the two is not dis- 

 coverable. 



Of these rocks, then, that containing the smaller propor- 

 tion of silica and the greater of alumina is the more recent. 



The distinction of two granites in the chain of the Vosges 

 is not of mere local interest ; the remark may be extended 

 to most granitic regions, of which I will only mention the 

 right bank of the Rhine, Normandy, Brittany, Auvergne, Ire- 

 land, &c. 



The general application of the above observations shews 

 that the same geological phenomena are reproduced after 

 long intervals of time and in widely separated districts. It 

 is not then surprising that we should find in most granitic 

 regions two granites : the one porphyritic, and containing 

 but one mica ; the other granular (grenu), and containing 

 two micas ; the former being the more recent, and generally 

 poorer in silica. 



On the Paragenetic Relations of Minerals. 



(Continued from vol. lv., page 106.) 



(A.) Congeneration Lodes are those which bear only the 

 same kind of minerals as constitute the adjoining rock. The 

 most remarkable are those of granite, and some quartz veins 

 in mica and clay slates. It is very probable that such lodes 

 or veins do not differ much in date from the rocks which they 

 traverse. They do not possess any great importance. 



(B.) Lodes or Veins formed by Lateral Secretion. — The 



