SECT; XXIX. ELECTRO-CHEMICAL ACTION. 307 



resisting medium, for even with the best air-pumps it is impossible 

 to make a perfect void ; he is still occupied with experiments on 

 this new subject, and no doubt will obtain very remarkable 

 results, of which none can be more extraordinary than his dis- 

 covery of the powerful influence of the magnet on this electric 

 light. The stratifications are formed in rapid succession in the 

 tube with platinum wires and are turned different ways, but they 

 can be separated at any part of the tube by the pole of a magnet 

 round which the whole stratifications have a tendency to revolve. 

 In the second experiment, where the tinfoil was used, the discharge 

 was divided in two by the pole of a magnet, and the two parts had 

 a tendency to rotate round the magnet in opposite directions. 



Voltaic electricity is a powerful agent in chemical analysis. 

 When transmitted through conducting fluids, it separates them 

 into their constituent parts, which it conveys in an invisible 

 state through a considerable space or quantity of liquid to the 

 poles, where they come into evidence. Numerous instances 

 might be given, but the decomposition of water is perhaps the 

 most simple and elegant. Suppose a glass tube filled with water, 

 and corked at both ends ; if one of the wires of an active Voltaic 

 battery be made to pass through one cork, and the other through 

 the other cork, into the water, so that the extremities of the two 

 wires shall be opposite and about a quarter of an inch asunder, 

 chemical action will immediately take place, and gas will con- 

 tinue to rise from the extremities of both wires till the water has 

 vanished. If an electric spark be then sent through the tube, 

 the water will reappear. By arranging the experiment so as to 

 have the gas given out by each wire separately, it is found that 

 water consists of two volumes of hydrogen and one of oxygen. 

 The hydrogen is given out at the positive wire of the battery, 

 and the oxygen at the negative. The oxides are also decomposed ; 

 the oxygen appears at the positive pole, and the metal at the 

 negative. The decomposition of the alkalies and earths by Sir 

 Humphry Davy formed a remarkable era in the history of science. 

 Soda, potass, lime, magnesia, and other substances heretofore 

 considered to be simple bodies incapable of decomposition, were 

 resolved by electric agency into their constituent parts, and 

 proved to be metallic oxides, by that illustrious philosopher. All 

 chemical changes produced by electricity are accomplished on 

 the same principle ; and it appears that, in general, combustible 



