during the contraction and consolidation of the
originally soft substances of the rocks themselves ;
and more frequently into fissures produced by
the fracture and dislocation of the solid strata.
Segregation of this kind may have taken place
from electro-chemical agency, continued during
long periods of time.*
The total quantity o f all metals known to
ex ist near the surface o f the Earth (excepting
Iron,) being comparatively small, and their
value to mankind being o f the highest order,
as the main instruments b y the aid o f which he
emerges from the savage state, it was o f the
utmost importance, that they should be disposed
in a manner that would render them accessible
b y his industry ; and this object is admirably
attained through the machinery of metallic veins.
* The observations of Mr. Fox on the electro-magnetic properties
of metalliferous veins in Cornwall, (Phil. Trans. 1830, &c.)
seem to throw new light upon this obscure and difficult subject.
And the experiments of M. Becquerel on the artificial production
of crystallized insoluble compounds of Copper, Lead, Lime, &c.
by the slow and long continued reaction and transportation of
the elements of soluble compounds, (see Becquerel, Traité de
l’Electricité, T. i. c. 7, page 547, 1834,) appear to explain many
chemical changes that may have taken place under the influence
of feeble electrical currents in the interior of the earth, and more
especially in Veins.
I have been favoured by Professor Wheatstone with the following
brief explanation of the experiments here quoted.
“ When two bodies, one of which is liquid, react very feebly
on each other, the presence of a third body, which is either a
conductor of electricity, or in which capillary action supplies the
Had large quantities of metals existed throughout
Rocks of all formations, they might have
been noxious to vegetation; had small quantities
been disseminated through the Body of
the Strata, they would never have repaid the cost
of separation from the matrix. These inconveniences
are obviated by the actual arrangement,
under which these rare substances are occasionally
collected together in the natural Magazines
afforded by metallic veins.
In my Inaugural Lecture (page 12) I have
spoken of the evidences of design and benevolent
contrivance, which are apparent in the original
formation and disposition of the repositories of
minerals ; in the relative quantities in which they
are distributed ; in the provisions that are made
to render them accessible, at a certain expence
place of conductibility, opens a path to the electricity resulting
from the chemical action, and a voltaic current is formed which
serves to augment the energy of the chemical action of the two
bodies. In ordinary chemical actions, combinations are effected
by the direct reaction of bodies on each other, by which all their
constituents simultaneously concur to the general effect; but in
the mode considered by Becquerel the bodies in the nascent
state, and excessively feeble forces, are employed, by which the
molecules are produced, as it were, one by one, and are disposed
to assume regular forms, even when they are insoluble, because
the number of the molecules cannot occasion any disturbance in
their arrangement. By the application of these principles, that
is, by the long-continued action of very feeble electrical currents,
this author has shewn that many crystallized bodies, hitherto
found only in nature, may be artificially obtained.”