230 
ON THE INFLUENCE WHICH A MOLECULAR MOVE- 
MENT DUE TO ELECTRICITY MAY HAVE EX- 
ERTED IN CERTAIN GEOLOGICAL PHENOMENA, 
NAMELY, THE METAMORPHISM OF ROCKS 
AND THE FORMATION OF METALLIFEROUS 
DEPOSITS.* 
By MANUEL FERNANDEZ DE CASTRO. 
G EOLOGISTS of the present day admit three distinct 
theories concerning the formation of metalliferous 
deposits : 1. One theory for metalliferous deposits, such as 
pockets, veins, stockwerks, and segregated lodes, the grouping 
or concentration of which is ascribed to molecular action, but 
without explaining the origin of the latter. 2. Another theory 
for true plutonic deposits, including also almost all lodes of 
contact and often showing molecular grouping. 3. A third 
theory for the true or concretionary lodes, the component parts 
of which are believed by some geologists to have been brought, 
dissolved by thermal waters, from the interior of the earth. Some 
geologists, however, consider these lodes due to segregation. 
The question arises : Is there no possibility of establishing 
a closer relation between these three classes of deposits ? 
Although many of the phenomena observed in mineral 
deposits could be more satisfactorily explained by the hydrother- 
mal than by the plutonic theory, the former left many dif- 
ficulties. Amongst others, as pointed out by De la Beche, the 
difference noted in the composition or structure of the lodes 
according to the nature and character of the rock traversed ; 
and further, the fact that we may find in the mass of the 
deposit, close to substances due to the agency of water, others 
which could be produced artificially only in the dry way, and 
at very high temperatures. The last-mentioned difficulty has 
been overcome to a certain extent by Senarmont, who succeeded 
in producing, by the agency of water, at a temperature varying 
* Extract from a pamphlet, Discursos leidos ante la Real Academia de 
Ciencias , etc. en la recepcion publica del JExmo. Sr. Don Manuel Fernandez 
de Castro. Madrid, 1878. 
