392 THE CANADIAN NATURALIST. [Dec. 



express their supposed mode of formation, endogenous granites. 

 They are to the gneisses and mica-schists, in which they are 

 generally enclosed, what calcite veins are to stratified limestones, 

 and although long known, and objects of interest from their mineral 

 contents, have generally been confounded with intrusive granites. 



§ 8. Scheerer, in his famous essay on granitic rocks, which 

 appeared in the Bulletin of the Geological Society of France in 

 1847, (vol. iv, p. 468), conceives the congealing granitic rocks 

 to have been impregnated with '''a juice" which was nothing else 

 than a highly heated aqueous solution of certain mineral matters. 

 Thi-, unJcr great pressure, oozed out, penetrating even the 

 str itiiieJ I'ocks in contact with the granite, filling cavities and 

 fis-ui-es in the latter, and depositing therein crystals of quartz and 

 of hornblende, the arrangement of which shows them to have been 

 of successive growth. Neither Scheerer nor Virlet d'Aout, who 

 supported his views, however (ihid., iv. p. 493) extended them to 

 feldspathic veins, though Daubree, at an earlier date, had described 

 certain g-rauitic reins in Scandinavia as havino; been formed bv 

 secretion rather than by igneous injection as maintained by 

 Durocher. 



§ 9. Elie de Beaumont, starting from the hypothesis of a 

 cooling liquid globe, imagined " a bath of molten matter on the 

 surface of which the first granites crystallized." From the ruins 

 of these were formed the first sedimentary deposits, but directly 

 beneath were other granitic masses, which became fixed immedia- 

 tely afterward. "Some parts of these masses, coagulated from 

 the commencement of the cooling process, but not completely 

 solidified, were then erupted through the sedimentary deposits" 

 just mentioned. " In these jets of pasty matter" were contained 

 many of the rarer elements of the granitic magma, which were 

 thus concentrated in the outermost portions of the granitic crust, 

 and in the ramifications formed by these portions in the masses 

 through which they were forced by the eruptive agents. Those 

 portions of the granitic masses and their ramifications in which 

 these rarer elements are concentrated, are distinguished from the 

 rest of the masses alike by their exterior position and their pecu- 

 liar structure. They are often coarse-grained, and include the 

 pegmatites, tourmaline-granites, and veins carrying cassiterite and 

 columbite often aboundmg in quartz. These mineral products 

 are to be regarded as emanations from the granite, and are de- 

 scribed as a granitic aura, constituting what Humboldt has call- 



