154 Mr Ritchie's examination of Galvanic Theories. 



brass, beat one of each pair on a smooth anvil till they are as 

 hard as possible. Form a binary combination with pairs of 

 the same metal, and use diluted sulphuric acid, and it will be 

 found by the galvanometer that the hard metal in each case 

 corresponds with zinc in the standard battery. If two pieces 

 of steel be employed, one of them soft, and the other temper- 

 ed, a galvanic effect will be produced, but of a contrary cha- 

 racter. The soft steel will correspond with zinc, and the hard 

 with copper, in the battery of comparison. The result of the 

 following experiment seems also at variance with previous no- 

 tions on the subject : — 



Exp. VI.— Having procured two small iron bars, with the 

 ends made bright with a file, and copper wires connected with 

 the other ends, I heated the end of one of 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 re- 

 ceived 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. 



Exp. VII. — Let a cylinder of copper, about an inch in 

 diameter, and two inches long, have a small copper tube 

 soldered in one end, whilst the other end is left open. Let a 

 small cylinder of zinc having a copper wire soldered to the 

 lower end, be placed within the copper cylinder. 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 cop- 

 per 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 completely 

 filled with water, and a solid screw dipped in electric cetnent, 

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



