468 
Davy charged a Leyden battery with 2000 pairs of zine and 
copper plates, each plate exposing thirty-two superficial inches 
of metal to the exciting liquid ; the total surface being 128,000 
square inches. On making the proper connexions, with the 
Leyden battery, ‘either a shock or a spark could be per- 
ceived.” Thus the shock was barely perceptible ; and to this 
Mr. Donovan added his own testimony of the shock from a 
Leyden battery, charged by 1000 pairs of plates, which he re- 
presented as exceedingly feeble. 
In support of the inference drawn of the trifling nature of 
the shock, and the inconsiderable quantity of electricity which 
a Leyden battery is capable of communicating, when charged 
by a voltaic series, Mr. Donovan detailed an experiment made 
by Professor E. Davy and himself, in which twenty Wedg- 
wood ware troughs, each containing ten cells, were employed, 
with a total number of 200 pairs of plates excited by dilute 
acids. When charcoal points, fixed to the polar wires, were 
brought into contact, an instantaneous burst of light, of 
dazzling splendour, announced that the series was in high ac- 
tion. On attempting to charge a Leyden battery of twelve or 
thirteen square feet of coated surface with this voltaic series, 
neither shock nor spark could be obtained. Yet it was proved 
that the charge communicated to the Leyden battery by three 
turns of a very small electric machine was sufficient to enable 
the battery to give a spark visible in day-light, the three turns 
producing three weak sparks of one inch in length. Six turns 
of the cylinder, that is six one-inch sparks, enabled the Ley- 
den battery to give a sensible shock. ‘This failure was sup- 
posed to be explicable by the small size of the Leyden battery 
compared with that of Van Marum, the ratio being as 123 to 
1373. 
So far as all the experiments, whether these last, or those 
of Van Marum or Davy, are concerned, there seems to be no 
evidence of great quantity of electricity in the voltaic series. 
But, even if there were, it was stated that none of the fore- 
