and Chemical Theories of Galvanism' l^X 



states, This he conceives to be a new law of nature, a^i 

 claims to himself the honour of the discovery. He conceives 

 that its truth is proved by the following experiment : — 



Let a plate of zinc be soldered to a plate of copper at two 

 edges. Hold the plate of zinc in the hand, and touch th^ 

 under plate of a delicate electric condenser (le condensateur 4 

 lames d'or) with the copper plate, whilst a moistened finger i§ 

 applied to the upper plate of the instrument. Remove the 

 compound plate and the moistened finger, and then lift the 

 upper plate of the instrument by its insulating handle, ^nd the 

 shps of gold leaf will be found to diverge. Taking for granted 

 the truth of the experiment, the conclusion which Volta deduced 

 from it by no means follows as a legitimate inference. Dr 

 Wollaston has shown that a galvanic effect is produced by dis- 

 similar metals with the moist air of the atmosphere acting 4s 

 a chemical agent and an imperfect conductor. The same fact 

 is proved by the electric column of De Luc. The plate of 

 zinc becomes partially oxidized by the oxygen of the atmor 

 sphere, electricity is generated or set at liberty, and the film 

 of moist air in contact with the two metals, acts as the fluid 

 conductor in an ordinary voltaic arrangement. If the com- 

 pound plate be coated with electric cement to exclude the che- 

 mical action of the air on the zinc, I will venture to predict 

 that no decided electric effect will take place. Until the sup- 

 porters of the electric theory show by direct experiment that an 

 electric effect does take place with this modification of the ap- 

 paratus, we must view the whole of their reasoning as founded 

 on a gratuitous supposition. Having thus shown that Volta 

 and his followers have overlooked what appears to me to be 

 the very cause of the disturbance of electric equilibrium in the 

 two metals, I shall now demonstrate that the other principle 

 on which the theory js built is equally unfounded. This will 

 appear obvious from the two following experiments : — 



Exp. I. — Having poured into a watch glass a quantity of 

 diluted sulphuric acid, I placed 01? tlie surfaqe of the fluid a 

 piece of gold leaf, which was connected with one of the cups 

 of a delicate galvanometer I then placed a disc of platina foil 

 in the fluid below the gold leaf, and connected it with the 

 other fiwp of th^ instrument ; scarcely any electro-magnetic ef- 



