70 HISTORY OF GALVANISM. 



mitting amianthus, so as to cover it with a thin 

 metallic film. When a neutral salt was placed 

 in a vessel between two other vessels of water 

 connected by asbestos, the alkali passed to the ne- 

 gative, and the acid to the positive side : the de- 

 compostion in this case is complete, and the sub- 

 stances produced quite pure. A small vessel of 

 the infusion of litmus was interposed between 

 pure water and the solution of sulphate of potash, 

 and the latter was negatively electrified. The 

 acid passed across to the positive wire, and red- 

 dened the litmus, but the change of colour did 

 not extend beyond the centre ; so that the negative 

 side, although it was transmitting the acid, was 

 not affected by it. An experiment of precisely 

 an opposite kind was performed with the infusion 

 of turmeric, with a similar result ; and afterwards 

 the two operations were combined in the same 

 experiment, so that soda passed through tur- 

 meric, and muriatic acid through litmus, each 

 without changing their colour. 

 Passage of As it appeared that acids and alkalies could 



acids and * * 



alkalies be conveyed through water, without affecting co- 

 louring substances dissolved in it, Sir H. Davy 



next tried whether this power might not extend 

 to other bodies. He accordingly found, that 

 acids could be transmitted through alkalies, and 

 alkalies through acids, to their respective wires, 

 without neutralizing each other; and, in short, 

 that the electrical state which was induced upon 

 a substance, by the contact of the galvanic appa- 



