HISTORY OF GALVANISM. 31 



liberated. When fluids contain no oxygen, they Fluids 

 appear to be incapable of transmitting the galvanic oxygen 

 influence; while, on the contrary, it would seem ^Jt! " 

 that it may be transmitted by every one which 

 contains this element.* These views of Cruick- 

 shanks respecting the action of the pile were 

 confirmed by some experiments that were per- 

 formed, about the same time, by Colonel Haldane. 

 He found that the apparatus ceased to act when Haidane's 

 it was immersed in water, or if it was placed in " e nt"~ 

 the vacuum of an air-pump. He found, on the Pile will 

 contrary, that it acted more powerfully in oxygen 



gas, than when confined in an equal bulk of at- 

 mospheric air, while azote had the same effect 

 as a vacuum. These circumstances led him to 

 conceive that its action depended essentially upon 

 the combination of oxygen, which it derives from 

 the atmosphere.f He also made some experi- 

 ments on the series of metals which are the best 

 adapted for producing the galvanic effects, and the 

 relative power which they possess in this respect. 



In the early part of his experiments, Cruick- Trough ap - 

 shanks invented a new manner of disposing the Fig. 5, ' 

 apparatus, which has proved scarcely less im- 

 portant to the interests of science, than its ori- 

 ginal discovery by Volta. I allude to the method 

 of placing the metals horizontally in a frame or 

 trough, with proper intervals for containing the 

 fluid which is intended to act upon them. 



* Nicholson's Journ. 4to. iv. 254. t Ibid, 241, 313. 



