Atmospheric Electricity	i 9
action (26), and the discharge made by platina spatulas through
the tongue or the gums, the effect upon the tongue and eyes was
exactly that of a momentary feeble voltaic circuit.
 69.	v. Spark.—The beautiful flash of   light attending the
discharge of common electricity is well known.    It rivals in
brilliancy, if it does not even very much surpass,, the light from
the discharge of voltaic electricity; but it endures for an instant
only, and is attended by a sharp noise like that of a small ex-
plosion.    Still no difficulty can arise in recognising it to be the
same spark as that from the voltaic battery, especially under
certain circumstances.    The eye cannot distinguish the differ-
ence between a voltaic and a common electricity spark, if they
be taken between amalgamated surfaces of metal, at intervals
only, and through the same distance of air.
 70.	When the Leyden battery (27) was discharged through
a wet string placed in some part of the circuit away from the
place where the spark was to pass, the spark was yellowish,
flamy, having a duration sensibly longer than if the water had
not been interposed, was about three-fourths of an inch in
length, was accompanied by little or no noise, and whilst losing
part of its usual character had approximated in some degree
to the voltaic spark.   When the electricity retarded by water
was discharged between pieces of charcoal, it was exceedingly
luminous and bright upon both surfaces of the charcoal, re-
sembling the brightness of the voltaic discharge on such surfaces.
When the discharge of the unretarded electricity was taken
upon »charcoal, it was bright upon both the surfaces (in that
respect resembling the voltaic spark), but the noise was loud,
sharp, and ringing.
71.1 have assumed, in accordance, I believe, with the opinion
of every other philosopher, that atmospheric electricity is of
the same nature with ordinary electricity (20), and I might
therefore refer to certain published statements of chemical
effects produced by the former as proofs that the latter enjoys
the power of decomposition in common with voltaic electricity.
But the comparison I am drawing is far too rigorous to allow
me to use these statements without being fully assured of their
accuracy; yet I have no right to suppress them, because, if
accurate, they establish what I am labouring to put on an
undoubted foundation, and have priority to my results.
72. M. Bonijol of Geneva 1 is said to have constructed very
delicate apparatus for the decomposition of water by common
1 Bibliotheque Universelle, 1830, tome xlv. p. 213.