1870.] T. S. HUNT — ON GRANITIC ROCKS. 393 



ed the penumbra of the granite. {Bull. Soc. Geol. de France, (2) 

 iv, 1249. See particularly pages 1295, 1321 and 1323). 



§ 10. While Fournet, Durocber and Riviere conceived the 

 granitic magma to have been purely anhydrous, and in a state of 

 simple igneous fusion, Elie de Beaumont maintained with Poulett- 

 Scrope and Schcerer that water had in all cases intervened, and 

 that a few hundredths of water might, at a low red heat, have 

 given rise to the condition of imperfect liquidity which he imagin- 

 ed for the material of the injected granites. The coarsely crystal- 

 line granitic veins were, according to him, veins of injection, and 

 he speaks of them as examples in which " the phenomena essential 

 to the formation of granite had been manifested with the great- 

 est intensity." The granitic emanations, which are supposed to 

 have furnished the material of these veins, appear to be regarded 

 by him as the result of a process of eliquation from the congealing 

 granitic mass. De Beaumont is careful to distinguish between 

 them and those emanations which are dissolved in mineral waters 

 or are exhaled as volcanic vapors (page 1324). To the agency of 

 such waters he ascribes the formation of concretionary veins, which 

 are generally characterized by their symmetrically banded struc- 

 ture. He further adds that granites, as to their mode of forma- 

 tion, offer a character intermediate between ordinary veins and 

 volcanic and basic rocks. This is conceivable as regards granitic 

 veins, since these, according to him, although formed by injec- 

 tion, and not by concretion, result from a process of emanation 

 from the parent granitic mass, which may be described as a kind 

 of segregation. 



I have thus endeavored to give, for the most part in his own 

 words, the views on the origin of granites enunciated by the great 

 French geologist in his classic essay on Volcanic and Metalliferous 

 Emanations, published in 1847. They belong to the hisiory of 

 our subject, and are remarkable as a clear and complete exf ris>i(.n 

 of those modified plutonic views which are piobably h< hi by .i 

 great number of enlightened geo'ogists at the present time. My 

 reason for dissenting from them, and the theories which I offer in 

 their stead will be shown in the sequel, 



§ 11. Elie de Beaumont, while regarding the formation of 

 granitic veins as a process in which water intervened to give 

 fluidity to the magma, was careful to distinguish the process from 



that of the production of concretionary veins from aqueous solution, 

 and supposed the fissures to have been filled by the injection of a 



