Voltaic Electricity	3
present not as philosophical, but merely as convenient The
effect of electricity of tension, at rest, is either attraction or
repulsion at sensible distances. The effects of electricity in
motion or electrical currents may be considered as ist, Evolu-
tion of heat; 2nd, Magnetism; 3rd, Chemical decomposition;
4th, Physiological phenomena; 5th, Spark. It will be my
object to compare electricities from _ different sources, and
especially common and voltaic electricities, by their power of
producing these effects.
I.  Voltaic Electricity
 4.	Tension.—When a voltaic battery of 100 pairs of plates
has its extremities examined by the ordinary electrometer, it is
well known that they are found positive and negative, the gold
leaves at the same extremity repelling each other, the gold
leaves at different extremities attracting each other, even when
half an inch or more of air intervenes.
 5.	That ordinary electricity is discharged by points  with
facility through air;   that it is readily transmitted through
highly rarefied air; and also through heated air, as for instance
a flame;   is due to its high tension.    I sought, therefore, for
similar effects in the discharge of voltaic electricity, using as
a test of the passage of the electricity either the galvanometer
or chemical action produced by the arrangement .hereafter to
be described (48, 52).
6.	The voltaic battery I had at my disposal consisted of jljo
pairs of plates four inches square, with double coppers.    11 was
insulated throughout, and diverged a gold leaf electrometer
about one-third of an inch.    On endeavouring to discharge this
battery by delicate points very nicely arranged and approxi-
mated, either in the air or in an exhausted receiver, I. could
obtain no indications of a current, either by magnetic or chemical
action.   In this, however, was found no point of discordance
between voltaic and common electricity;  for when a Leyden
battery (27) was charged so as to deflect the gold leaf electro-
meter to the same degree, the points wore found equally unable
to discharge it with such effect as to produce either magnetic
or chemical action.   This was not because common electricitA*
could not produce both these effects (43, 46), but because when
of such low intensity the quantity required to make the offerts
visible (being enormously great (107, m)) could not be trans
mitted in any reasonable time.   In conjunction with the other

I
I1
i
,ns
t
I
i
i
ii