IN INCKEASING 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 phasnome- 

 non, since it appears to be produced by a lateral discharge, and it is 

 therefore imjiortant 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 sliould 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 



