Method of increasing Shocks, &fc. 139 



maximum with this apparatus. It will be seen from this, that from 

 cup 4 to 6, the shock is inversely as the spark, while in the first half 

 of the coil, it is in the same ratio. It may be well to mention here, 

 that I found if the surface of the mercury, where the contact be brok- 

 en, be covered with water, the shock is very much increased. The 

 rationale I am unable to give, but such is the fact. This augmenta- 

 tion does not take place at every rupture of contact, but is best at- 

 tained by striking the connector against the bottom of the cup and 

 quickly raising it. The shock is also increased by covering the mer- 

 cury with naphtha and the mercury appeared to be oxidized, the 

 naphtha soon growing turbid. 



The next results to be stated, are still more curious, and accor- 

 ding to the received theories of electromotion, difficult to explain. 

 The pos. con. and right hand are still in cup 1. The neg. con. in 

 cup 2, and the left hand in cup 3, the shock is now stronger than 

 when the left hand was in cup 2 with the connector, and the shock 

 goes on increasing as the left hand is carried into cups 4, 5 and 6 in 

 succession.* Let now the pos. con. and right hand remain in cup 

 1, place the neg. con. in cup 3, and the left hand in cup 4; the shock 

 goes on increasing as before, and when the left hand arrives at cup 

 6, the shock is as strong as that obtained from the whole coil, (220 

 feet,) while the actual circuit from positive to negative, is only 80 

 feet. Let the pos. con. and right hand remain in cup 1, put the 

 neg. con. in cup 4 and the left hand in cup 5 ; the shock is now as 

 strong as when the whole coil is in the circuit, and when the left hand 

 is in cup 6, the shock is stronger than can be obtained from the 

 apparatus in any other way. These last results show that the real 

 maximum as indicated by the shock, is given by the direct circuit 

 from positive to negative, through half the coil, with the lateral co- 

 operation of the other half. 



Thus much being known, we might reasonably expect that while 

 the connectors are in the extreme cups 1 and 6, we should obtain 

 shocks from any two intermediate cups, and this I found to be the 

 case ; but contrary to expectation, I obtained shocks from cups en- 

 tirely without the actual circuit. For instance the pos. con. in cup 

 1, neg. in 3, right hand in 4, and left hand in 6. In this case the 

 shock was slight ; but by thrusting needles into the thumb and fore 

 finger of the left hand, and immersing the needles in cups 4 and 6, 

 the shock was extremely painful. 



* An assistant is necessary to make the immersion of the connectors. 



