XI.] GRANITES AND GRANITIC VEIN-STONES. 191 



the history of our subject, and are remarkable as a clear and 

 complete expression of those modified plutonic views which 

 are probably held by a great number of enlightened geologists 

 at the present time. My reasons 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 aque- 

 uous solution, and supposed the fissures to have been filled by 

 the injection of a jet of pasty matter derived from a consolidat- 

 ing granitic mass. Daubree and Scheerer, in describing the 

 granitic veins of Scandinavia, conceive the material filling 

 them to have been derived from the enclosing crystalline strata, 

 instead of from an un stratified granitic nucleus, but do not, so 

 far as I am aware, compare their formation to that of concre- 

 tionary veins. Their publications on this subject, it should 

 be said, are both anterior to the essay of De Beaumont. 



12. The notion that all granitic veins are the result of 

 some process of injection, and not to be confounded with con- 

 cretionary veins, seems indeed to have been general up to the 

 present time. Even Von Cotta, while strongly maintaining the 

 aqueous and concretionary origin of metalliferous veins in gen- 

 eral, when describing those consisting of quartz, mica, feldspar, 

 tourmaline, garnet, and apatite, with cassiterite, wolfram, etc., 

 which occur at Zinnwald and at Johanngeorgenstadt, is at a 

 loss whether to regard these veins, from their granitic character, 

 as igneous-fluid injections or as concretionary lodes. In sup- 

 port of the latter view he refers to their more or less regular 

 and symmetrically banded structure, and while recalling the 

 fact that mica and feldspar may both be formed in the humid 

 way, considers the nature of these veins to be very problemati- 

 cal, and the question of their origin a difficult one. (Ore De- 

 posits, Prime's translation, 1870,. pages 110- 124.) 



1 3. I have for several years taughj^that granitic veins of 

 the kind just referred to are concretionary and of aqueous 



