364 MR. RITCHIE'S EXAMINATION OF THE ELECTRIC 



containing the water alone. This agrees with the chemical theory. Again, 

 instead of the above acids use nitrous acid, and the needle will turn round in 

 the opposite direction. The same thing holds when discs of copper or iron are 

 employed. This is completely at variance with the chemical theory, since that 

 plate is negative, or corresponds with copper in the standard battery, on which 

 the greatest chemical action of the fluid takes place. The following experiment 

 is also hostile to the generally received theory. 



Experiment IV. 



Having taken two pieces of block tin, I cut the surface of one of them into 

 ridges by means of a three-cornered file, so that the surface was doubled. 

 With these two pieces I formed a binary combination, and immersed them 

 in diluted nitro-muriatic acid; a very considerable electro-magnetic effect was 

 produced, and the needle turned round in the same direction as it does when 

 a plate of zinc is substituted for the plane disc in the standard batteiy. It is 

 obvious that there must be a greater chemical action between the acid and the 

 furrowed plate than the other, and yet the furrowed plate corresponds with 

 copper in the standard battery, on which the least chemical action takes place. 

 The results obtained in the following experiment were also unexpected. 



Experiment V. 



Take equal pieces of soft zinc, copper, iron, or brass, beat one of each pair 

 on a smooth anvil till they are as hard as possible. Form a binary combina- 

 tion 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 tempered, a galvanic effect will be produced, but of a 

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

 with copper, in the battery of comparison. The result of the following expe- 

 riment seems also at variance with previous notions on the subject. 



Experiment 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 



