ee 
Geological Society of London. 93 
MINERAL VEINS. 
Your attention has been called to the origin of mineral veins by 
Mr. Fox, who has endeavored to explain why so large a proportion 
of the metalliferous veins in England and other parts of the world 
should have an east and west direction. He supposes fissures filled 
with water, containing sulphurets and muriates of copper, tin, iron, 
and zinc in solution, through which currents of voltaic electricity 
are transmitted. The metals separated from their solvents by this 
action are deposited in the veins, and most abundantly in veins run- 
ning at right angles to the direction of the earth’s magnetism ; for as 
the magnetic currents of the earth pass from north to south, they 
cause those of electricity to move east and west, although considera- 
ble deviations from this direction must be occasioned in the course 
of geological epochs by variations in the magnetic meridian. 
Since Mr. Fox first ascertained the existence of electric currents 
in some of the metalliferous veins in Cornwall,* Mr. Henwood has 
made many experiments on the same subject, together with obser- 
vations on the distribution of metallic and earthy minerals in veins. 
He considers the results obtained by him to be in a great degree op- 
posed to the theory of Mr. 
Mr. Fox conceives the fissures in which metalliferous substances 
occur, to have been at first smal] and narrow, and to have increased 
gradually in their dimensions. This doctrine has also been pro- 
pounded in a work with which you are probably familiar, and from 
which I have derived much instruction, I mean M. Fournet’s Essa 
on Metalliferous Deposits. This Essay was originally included in 
the third volume of M. Burat’s continuation of D’ Aubuisson’s Trea- 
tise on Geology, (1835,) but it is now published separately, and 
gives the clearest general view which I have seen of the application 
of geological theories to phenomena observed in mining. It is writ- 
ten by one who has acquired much practical knowledge as a miner, 
and who is well versed in chemistry and mineralogy.t 
Werner, when he published his justly celebrated Essay on Mine- 
ral Veins, had come to the conclusion that the same rent, after being 
* Phil. Trans. 1830, p: 399. 
+ See Mining Journal, Supplement 9. p. 34, December, 1836, and Annals of 
Electricity, No. 2. vol. i. on Electric Currents, &c. wb T. Henwood, Esq. 
t Etudes sur les Dépots Métalliféres, par M. I. Fournet 
