GALVANISM. 



flving out hydrogen gas, on the contact 

 eing made, the metal in solution became 

 reduced. Thus, when iron and silver were 

 placed in a solution of copper, the iron 

 immediately began to reduce the copper 

 in solution, while the silver had not the 

 slightest action, Upon bringing the two 

 metals in contact, however, the silver be- 

 came coated with copper. Dr. Wallaston 

 attributes the curious phenomon, above 

 described, to a change of states in the elec- 

 tricity of the metals ; and in order to con- 

 firm this idea, he attempted the s.one by 

 means of common electricity, in which he 

 succeeded to his utmost satisfaction. He 

 supposes, that the chemical affinities are 

 so altered by the presence or absence of 

 electricity, as to induce the anomalous 

 appearances which took place in the 

 above experiments. The silver wire be- 

 came coated with copper, and at the same 

 time appeared to have the power of de- 

 composing water. 



The only mystery we observe in these 

 experiments is the liberation of the hy- 

 drogen, in a situation where no oxygen 

 is manifested, either in the form of gas, or 

 in any other state. Nor does the new 

 doctrine, lately advanced by Mr. Davy, 

 throw much light on this subject. The 

 zinc, in this experiment, is said to be po- 

 sitively electrified, and the copper or sil- 

 ver to be negative. That the zinc, on that 

 account, attracts the oxygen of the water, 

 and the silver the hydrogen. That the 

 constituent parts of water are by the same 

 law made to appear in situations where 

 the decomposition did not take place, is 

 very evident; hence it would appear that 

 the hydrogen is carried by some means 

 from the zinc to the silver; or that the 

 oxygen passes from the silver to the zinc; 

 or, according to Mr. Davy's hypothesis, 

 the decomposition ofthe watertakes place 

 between the metals, the oxygen passing 

 inevitably to the zinc, and the hydrogen 

 in a similar way to the silver. To the 

 latter there are several objections, which 

 will appear from the following experi- 

 ments. 



Let a tube of three feet in length be 

 filled with dilute muriatic acid, and cork- 

 ed at both ends, having a wire of zinc 

 inserted in one end, and one of silver or 

 platina in the other. The zinc will im- 

 mediately begin to give out hydrogen, 

 but no effect will be observed at the sil- 

 ver wire. Let a communication be esta- 

 blished between the wires on the outside 

 ofthe tube. The silver does not imme- 

 diately give out bubbles, as was the case 

 in the experiments of Dr. Wollaston, nor 

 does that effect take place till a few se- 



conds after the contact of the metals. 

 Can we for a moment suppose that the 

 slight negative and positive electricity 

 produced by the contact of two small 

 wires, which would not affect the most 

 delicate electrometer, can have the pow- 

 er, the one of attracting oxygen, and the 

 other hydrogen, at the distance of eigh- 

 teen inches, reckoning from the middle 

 of the tube? 



If the same tube be bent in the middle 

 to an acute angle, like the letter V, ac- 

 cording to Mr. Davy's hypothesis, the 

 appearance ofthe hydrogen at the silver 

 wire ought to take place as soon after the 

 contact, as with the straight tube ; but 

 what is very singular, it will not take 

 place at all. This experiment would 

 seem to prove, that one of the constitu- 

 ents of the water is carried through the 

 whole length of the tube ; and that by 

 some law which differs from those of elec- 

 tricity, since the angle ofthe tube appear- 

 ed to interrupt its passage. The interrup- 

 tion is still greater, even with a shorter 

 tube, when the tube is bent in different 

 places, forming a sort of zig-zag. 



The idea that hydrogen is carried from 

 the zinc to the copper-wire, is strongly 

 favoured by another experiment. Take 

 the glass tube A B, fig. 2, filled with di- 

 lute muriatic acid, having a cork at B, 

 through which the wires, z and c are 

 passed, z being a wire of zinc, and c a wire 

 of platina, silver, or copper. So long as 

 the wires remain unconnected at z, the 

 platina- wire appears unchanged ; but as 

 soon as the contact is formed, bubbles of 

 hydrogen are first seen ate/; they then 

 very slowly begin to appear in the lower 

 parts of the wire ; but what is singular, 

 the moment they begin to appear at/, 

 they are also seen at s, and some seconds 

 are elapsed before any bubbles are seen 

 at g. If the hydrogen in the last experi- 

 ment were attracted by the negative 

 state ofthe platina-wire, since the metal 

 is the best conductor, it would seem, that 

 the point s would be the last part to 

 have parted with its electricity ; and, of 

 course, the bubbles of hydrogen ought to 

 have appeared the last at that point, 

 whicn is contrary to fact. It therefore 

 appears more likely that the hydrogen 

 has been held in combination by the elec- 

 tricity, the latter of which is taken by the 

 nearest metallic conducter in the circuit, 

 leaving the hydrogen in its gaseous form: 

 the law, however, by which it moves 

 along the liquid, does not appear to agree 

 with any known properties of electricity, 

 since the hydrogen is some seconds in 

 reaching the point i?. 



