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by experience. These effects are as manifold as the causes 
which produce electricity, or as the circumstances under which 
it is set free and propagated. Considering the results obtained 
by means of electro- chemical action from the time that Nichol- 
son and Carlisle decomposed water, and Davy extracted potas- 
sium and sodium by means of the voltaic pile, up to the time 
when Despretz obtained real crystals of diamond with the 
Buhmkorff coil ; and considering further the numerous crys- 
tallized substances, identical with natural ones, artificially pro- 
duced by Becquerel and Crosse ; it would be unreasonable to 
reject the idea of establishing a theory of metamorphism based 
upon electrochemical and electrodynamical actions. All the 
effects due to metamorphism can also be produced by electro- 
telluric action. Thus Alcide d’Orbigny, when treating of fossili- 
zation in his well-known Cours Elementaire de Paleordologie, says 
that electrical actions and chemical affinities furnish excellent 
means for explaining substitution in fossils ; and he adds at the 
same time, that the action of these occult forces is more general 
than has hitherto been believed. Becquerel succeeded in re- 
producing by electrochemical processes epigenies of petref ac- 
tions, which cannot be produced artificially in any other way ; 
and when enumerating the causes to which metalliferous lodes 
are due, Fox and Fournet speak of electrochemical actions 
resulting from the contact of a number of various rocks. 
The author’s attention always has been drawn to certain 
geological phenomena which can be reproduced artificially in 
the laboratory of the chemist, but only by employing much 
more powerful means than nature apparently makes use of for 
the same purpose. Although we are able to perceive in both 
cases the effects, it is different as regards the modus operandi , 
because our senses are only capable of distinguishing and appre- 
ciating phenomena within a limited scale ; and as soon as we 
have to consider something very great or very small, very quick 
or very slow, we require the use of instruments which increase 
the faculty of perception : but in the greater number of cases we 
can thus realize, by our imagination only, the nevertheless well- 
established facts. As already mentioned in the artificial pro- 
duction of the minerals found at Plombieres, a much higher 
temperature and pressure had to be used than nature apparently 
employed in their formation. Thus, Wohler had to make use 
of a temperature of 180°-190° C., and of a pressure of from 
ten to twelve atmospheres to produce artificially those minerals 
which nature had formed in the Bom an aqueducts of Plom- 
bieres at a temperature of 70° C., and under ordinary atmosphe- 
rical pressure. Is it possible that nature, operating by infinites- 
imally small actions, but during an unlimited time, can achieve 
results astonishing by their magnitude, just as in the higher 
