IN INCREASING THE INTENSITY OF ELECTRICITY. 543 
The effect was increased, until one of ninety-six feet long, an inch and 
a half wide, and weighing fifteen pounds, was used. The snap from 
this was so loud that it could be distinctly heard in an adjoining room 
with the intervening door closed. Want of materials has prevented me 
from trying a larger spiral conductor than this ; but it is probable that 
there is a length which, with a given quantity and intensity of galvanism, 
would produce a maximum effect. When the size of the battery is 
increased, a much greater effect is produced with the same spiral. 
Thus when the galvanic apparatus described in the first article is ar- 
ranged as a calorimotor of eight pairs, the snap produced on breaking 
contact with the spiral last described resembled the discharge of a 
small Leyden jar highly charged. 
8. A handle of thick copper was soldered on each end of the large 
spiral at right angles to the ribbon, similar to those attached to the 
wires in Pixii’s magneto-electric machine for giving shocks. When one 
of these was grasped by each hand and the contact broken, a shock was 
received which was felt at the elbows; and this was repeated as often 
as the contact was broken. This shock is rather a singular phenome- 
non, since it appears to be produced by a lateral discharge, and it is 
therefore important to determine its direction in reference to the pri- 
mary current. 
9. A shock is also received when the copper of the battery is grasped 
by one hand, and the handle attached to the copper pole of the ribbon 
with the other. This may be called the direct shock, since it is pro- 
duced by a part of the direct current. It is, however, far less intense 
than that produced by the lateral discharge. 
10. When the poles were joined by two coils connected by a cup of 
mercury between them, a spark was produced by breaking the circuit 
at the middle point; and when a pair of platina wires was introduced 
into the circuit with the large coil and immersed in a solution of acid, 
decomposition took place in the liquid at each rupture of contact, as 
was shown by a bubble of gas given off at each wire. It must be re- 
collected that the shocks and the decomposition here described were 
produced by the electricity from a single pair of plates. 
11. The contact with the poles of the battery and the large spiral 
being broken in a vessel containing a mixture of hydrogen and atmo- 
spheric air, an explosion was produced. 
I should also mention that the spark is generally attended with a de- 
flagration of the mercury, and that when the end of the spiral is brought 
in contact with the edge of the copper cup or the plate of the battery, 
a vivid deflagration of the metal takes place. The sides of the cup 
sometimes give a spark when none can be drawn from the surface of 
the mercury. This circumstance requires to be guarded against when 
experimenting on the comparative intensities of sparks from different 
