212 Mr. M. Donovan on the supposed Identity of the Agent 



above all, why should frictional electricity be affirmed to be siif- 

 ficient in point of quantity in this special case, when universally 

 it is declared that it is inadequate to produce voltaic effects on 

 account of the smallness of its quantity ? 



I do not foresee what answer can be given to these questions, 

 or how the facts are reconcileable, while the opinion is entertained 

 that it is electricity, taken in the common acceptation of the 

 word, which causes deflections. But if we distinguish the agent 

 excited in the common electrical machine from that which is 

 effective in the voltaic series, the difference consisting in the 

 ratio of the constituent elements of the two fluids, then the de- 

 flection in one case and non-deflection in the other become more 

 intelligible. 



I will now state a few of my experiments : but it is necessary 

 to premise, that in most of them the action was so transitory, 

 owing to the peculiar circumstances, that there was no perma- 

 nent deflection, and the number of degrees to which the swing 

 of the needle extended, at its first start, was the only measure 

 which could be observed for comparison. 



A glass tray being half-filled with concentrated commercial 

 sulphuric acid, a plate of platinum was laid in it, and connected 

 with one of the binding-screws of a galvanometer by means of a 

 platinum wire. A stick of caustic potash was fastened to the 

 end of another platinum wire by several coils carried round it ; 

 the other end of this wire was connected with the other binding- 

 screw of the galvanometer. In a few moments the potash had 

 attracted sufficient humidity to become a conductor ; its end was 

 plunged into the sulphuric acid, but not so deeply as to touch 

 the platinum plate lying in the bottom. The needle whirled 

 completely round, and with great velocity. A second dip had 

 no effect ; but perceiving that this was caused by a coating of 

 bisulphate of potash, and having washed it off by a plunge into 

 water, a repetition of the dip into the sulphuric acid produced a 

 new deflection. After again washing it, the whole stick of pot- 

 ash was plunged on its side ; the needle again whirled round with 

 great force. 



In order to discover how much of the effect was due to the 

 platinum plate and wire, I removed the stick of potash, and 

 dipped the platinum coil to which it had been fastened into the 

 sulphuric acid ; the deflection amounted to 3° ; and in another 

 trial it did not stir. 



Becquerel made experiments with acid and alkaline solutions 

 by a different method, and produced deflections which he attri- 

 buted to electricity. How, in my experiment, the infinitesimal 

 quantity of electricity generated could whirl the same needle 

 round with violence, which refused to stir when a most powerful 



