16 DR. THOMAS STERRY HUNT ON THE 



sary to recall the fact that serpentines, and great deposits of magnetite and specular iron, 

 are still by some authorities considered as eruptive rocks, and that the hypothesis of the 

 io-neous origin of metalliferous lodes, taught by Hutton, is not yet wholly obsolete. In 

 1858, H. D. Rogers spoke of " the great dykes and A-^eins of auriferous quartz " supposed to 

 haA^e issued " in a melted condition through rents and fissures in the earth's crust. Out- 

 o-ushin"- bodies of this quartz," chilled by contact with the cold waters of the ocean, were 

 supposed by him to have furnished the material for the Primal quartzites of Pennsylva- 

 nia. -" Still later, in 18*74, we find Belt maintaining with learned ingen^^ity the igneous 

 ori"-in and the injection of auriferous quartz veins. He insists, as I have elsewhere done,^ 

 on the transition from veins of pure quartz, often metalliferous, to others containing feld- 

 spar, and thence to true granitic veins ; but instead of regarding these as aqueous and 

 concretionary, assumes them to be igneous, and thence concludes that the gold-bearing 

 quartz lodes were filled with liquid quartz by " igneous injection," though admitting that 

 in these, as in granites, water helped to impart liquidity. '^ 



& 33. In farther illustration of the extension of the plutonic doctrine to other rock- 

 masses than those already mentioned, I quote from an essay by Daubrée, published in 18Yl.^ 

 " The hypothesis advanced by Lazzaro Moro, in 1*740, attributing an eruptive origin to rock- 

 salt as well as to sulphur and bitumen, was again taken up and applied by de Charpentier 

 (1823) to the salt-mass at Bex, which is associated with anhydrite ; and d'Alberti, in the 

 classic study made by him of this terrane, maintained the same hyjjothesis for all the rock- 

 salt found in the trias. Moreover, the examination of the deposits of pisolitic iron ore had, 

 in 1828, conducted Alexandre Brongniart to a similar conclusion, which was soon after 

 applied to the silicious deposits which constitvate the buhrstone of the tertiary. A like 

 origin was by d'Omalius (1841 and 1855) ascribed to other substances, particularly to 

 certain clays and to certain sands, which, especially in Belgium, appear to be connected 

 with the formation of calamine, and which Dumont in 1854 called geyserian deposits." 

 " It was thus," adds Daubrée, " that various substances belonging to sedimentary strata 

 were recognized as coming, or at least were supposed to come, from the lower regions 

 {étaient reconnues ou au moins étaient supposées provenir des régions profondes.)" 



§ 34. The presence of water in ignited and molten rocks was shown by Poulett 

 Scrope in 1825 in his studies of volcanoes.^' Subsequently, Scheerer, conceived that a small 

 portion of water, probably five or ten hundredths, might, at a low red heat, giA^e rise to a 

 condition of imperfect liquidity such as he imagined for the material of eruptive granites. 

 Similar ideas as to the aqueo-igueous fusion of granite were at the same time adopted by 

 Élie de Beaumont, and are now generally admitted, the more so, as they are in accordance 

 with the results of microscopic study. From the presence in granitic rocks of what he 

 called pyrognomic minerals, like allanite and gadolinite AAi^hich, by exposure to ignition» 



" Geology of Pennsylvania. II. 780. 



2« Chemical and Geological Essays, pp. 192-208, and infra Part II. 



'■^Belt, The Naturalist in Nicaragua, 1874, pp. 97-100. In the pages here referred to, my friend, whose premature 

 death was a great loss to science, has set forth with clearness the Huttonian theory of metalliferous veins. 



'" Daubrée, Des terrains stratifiés considérés au point de vue de l'origine des substances qui les constituent, 

 etc. Bull. Soc. Géol. de France (2) xxviii, p. 307. 



^' Scrojje, Considerations on Volcanoes, p. 25. 



