HISTORY OF GALVANISM. 



where the wire came in contact with the fluid. 

 This gas was thought to have the odour of hy- 

 drogen ; and it led them to notice, with more 

 attention, the effect produced by causing the 

 electricity to pass through a tube of water, into 

 the two ends of which wires were inserted, 

 which communicated with the extremities of the 

 pile. I shall relate this very important experi- 

 ment in Mr. Nicholson's own words. " On the 

 2d of May we inserted a brass wire through each 

 of two cocks, inserted in a glass tube of half an 

 inch internal diameter. The tube was filled with 

 New River water, and the distance between the 

 points of the wires in the water was one inch and 

 three quarters. This compound discharger was 

 applied, so that the external ends of its wire were 

 in contact with the two extreme plates of a pile 

 of thirty-six half-crowns, with the correspondent 

 pieces of zinc and pasteboard. A fine stream of 

 minute bubbles immediately began to flow from 

 the point of the lower wire in the tube, which 

 communicated with the silver, and the opposite 

 point of the upper wire became tarnished, first 

 deep orange, and then black. On reversing the 

 tube, the gas came from the other point, which 

 was now lowest, while the upper, in its turn, be- 

 came tarnished and black." " The product of 

 gas, during two hours and a half, was two- 

 thirtieths of a cubic inch. It was then mixed with 

 an equal quantity of common air, and exploded 

 by the application of a lighted waxed thread." 



