26	Faraday's Researches
glass, and a line distant from each other." x I cannot,, how-
ever, find any record of such an observation by either Walsh
or Ingenhousz, and do not know where to refer to that by
M. Fahlberg. M. Humboldt could not himself perceive any
luminous effect.
Again, Sir John Leslie, in his dissertation on the progress of
mathematical and physical science, prefixed to the seventh
edition of the Encyclopedia Britannica, Edinburgh, 1830, p. 622,
says, " From a healthy specimen " of the Silurus electricus,
meaning rather the gymnotus, " exhibited in London, vivid
sparks were drawn in a darkened room; " but he does not say he
saw them himself, nor state who did see them; nor can I find
any account of such a phenomenon; so that the statement is
doubtful.2
 95.	In concluding this summary of the powers of torpedinal
electricity, I cannot refrain from pointing out the enormous
absolute quantity of electricity which the animal must put in
circulation at each effort.    It is doubtful whether any common
electrical machine has as yet been able to supply electricity
sufficient in a reasonable time to cause true electro-chemical
decomposition of water (66,  75),  yet the current from the
torpedo has done it.   The same high proportion is shown by
the magnetic effects (32, 107).   These circumstances indicate
that the torpedo has power (in the way probably that Caven-
dish describes) to continue the evolution for a sensible time,
so that its successive discharges rather resemble those of a
voltaic arrangement, intermitting in its action, than those of a
Leyden apparatus, charged and discharged many times in suc-
cession.    In reality, however, there is no philosophical difference
between these two cases.
 96.	The general conclusion which must, I think, be drawn
from this collection of facts is, that electricity, whatever may
be its source, is identical in its nature.    The phenomena in the
five kinds of species quoted, differ, not in their character but
only in degree;  and in that respect vary in proportion to the
variable circumstances of quantity and intensity 3 which can at
pleasure be made to change in almost any one of the kinds of
electricity, as much as it does between one kind and another.
1	Edinburgh Phil. Journal, ii. p. 249.
2	Mr. Brayley, who referred me to these statements, and has extensive
knowledge of recorded facts, is unacquainted with any further account
relating to them.
3	The term quantity in electricity is perhaps sufficiently definite as to
sense;  the term intensity is more difficult to define strictly.    I am using
the terms in their ordinary and accepted meaning.