AND CHEMICAL THEORIES OF GALVANISM. 



365 



them, connected the wires with the galvanometer, and then immersed the hot 

 and cold ends in water ; a considerable action took place, and the cold iron 

 was found to correspond with zinc in the standard battery. Since oxygen 

 combines more rapidly with hot than with cold iron, positive electricity ought, 

 according to the received opinions, to have appeared at the hot iron, whereas the 

 contrary was actually the case. The following experiment is not only at 

 variance with the theory of Dr. Wollaston, but seems also hostile to some of 

 the generally received notions of chemists. 



A 



Experiment VII. 



Let C be a cylinder of copper, about an inch in diameter, and two 

 inches long, having a small copper tube t soldered in one end, whilst 

 the other end is left open. Let Z be a small cylinder of zinc, having 

 a copper wire w soldered to the lower end. The wire, being covered 

 with a thread and passed through the tube, is firmly cemented with 

 electric cement, metallic contact being carefully avoided. Another 

 end having a strong brass tube with an internal screw is now soldered 

 in the top of the copper cylinder. The interior surface of the cylinder of zinc 

 is covered with electric cement to prevent the acid acting on it. The whole is 

 now nearly filled with water, and a little sulphuric acid is introduced into the 

 zinc cylinder by means of a very slender glass funnel. The whole is now com- 

 pletely filled with water, and a solid screw dipped in electric cement, and 

 screwed into the top of the brass tube, whilst it is heated, renders the whole 

 completely air-tight. The acid is now to be mixed with the water by fre- 

 quently inverting and shaking the cylinder. If the copper and zinc cylinders 

 be connected with the galvanometer, the battery will continue to act for a day 

 or two with the same energy as if the whole had been left exposed to the air. 

 As there is no room for the disengagement of hydrogen, the oxygen of the 

 water cannot combine with the zinc to convert it into an oxide ; nevertheless 

 chemical action goes on, and the zinc is dissolved in the acid. From this 

 experiment it is obvious that the oxidation of the zinc and the combination of 

 nascent hydrogen with the electric fluid, as Dr. Bostock supposes, has nothing 

 to do with the production or transfer of the electricity which appears at the 

 surface of the zinc. The metal is still, however, dissolved or reduced from 



