Electricity and Galvanism, 



239 



bubbles of hydrogen. Once more let me unite the wires, the electri- 

 city from the decomposing salt again traverses the solution ; again 

 chemical forces are paralysed, and we shall soon see the spongy 

 amalgam of ammonium and mercury reappear. 



Fig. 1. 

































A 



r° 







Ml 







1 * 



Fig. 2. 



Fig. 1, Battery. 



A, Vessel containing solution of common salt. 



B, Glass cylinder, closed with a plug of plaster of Paris, and containing 



a solution of sulphate of copper. 



C, Copper plate. 

 Z, Zinc plate. 



Fig. 2, Decomposing cell. 



A, Vessel containing solution of common salt, having a zinc plate, Z, 



immersed, and connected by a wire with the copper plate C of 

 the battery. 



B, Glass tube, closed with plaster of Paris, containing a solution of 



hydrochlorate of ammonia, the amalgamated platinum wire im- 

 mersed in it passing through the cork, and connected with plate Z 

 of the battery. 

 We have just noticed the fact, that under the influence of a weak 

 current, salts can be resolved into their component elements. In this 

 way a compound can be separated into its constituent acid and base. 

 Now it is a remarkable fact, that if an acid and electric solution be so 

 placed that their union be effected through the parietes of an animal 

 membrane, or indeed any other porous diaphragm, a current of elec- 

 tricity is evolved. This fact was first noticed by Becquerel, and has 

 since been found to be true, not only with nitric acid and potass, 

 during whose combination he observed this disturbance of electric 

 equilibrium, but with all other acids and soluble bases. I am anxious 

 to demonstrate the accuracy of this statement to you, although I 

 fear the test I shall use, the deviations of the needle of an astatic 



