TO THE MOVEMENT OF MACHINES. 13 



causing it to pass througli a wire bent back on itself; this 

 however, is not the case. For this purpose I employed a helix 

 formed of two distinct wires, each of 400 feet in length (22) ; 

 the extremities of the one wire being designated a a', and those 

 of the other b b', I could not observe any notable difference 

 in the deviation of the needle of the interposed gahanometer, 

 whether the magneto-electric current was caused to pass through 

 these two wires in the direction a a' b' b, or in that of a a' b b'. 

 In this relation, the magneto-electric current of short duration 

 appears to have more analog)^ with the voltaic current, which 

 possesses the property, as has been proved by Professor Faraday, 

 of not being affected, either by the manner in which the wire is 

 bent, or by the presence of soft iron serving as nucleus. 



This Avill perhaps be the proper place to relate the following ex- 

 periment w hich I performed. Eveiy one is well acquainted with 

 the remarkable arrangement, presented by M. Becquerel to the 

 French Academy of Sciences, in its meeting of the /th December, 

 1835 {Ulnstitiit, No. 135). Assisted by Professor Gobel, I 

 constinicted a similar battery, which developed a considerable 

 quantity of gas at the platina plate immersed in an alkaline solu- 

 tion. When the galvanometer had been interposed, there was a 

 dexiation of 22°, which lasted for 6 to 7 hours, and which was not 

 much diminished by the interposition of a helix of 800 feet ; but 

 on breaking the circuit I observed neither discharge nor spark. 

 Nor was even the least sensation felt on interposing, as a se- 

 condarjr circuit, the tongue, or any flaying of the skin. To in- 

 stitute a comparison, I constructed a very small pile of copper, 

 of zinc, and very diluted sulphuric acid, of which I set only suf- 

 ficient surface in action to obtain the same deviation of the needle 

 as with Becquerel's arrangement. With this very small battery of 

 ordinary construction, the spark w^as visible, and a very feeble dis- 

 charge was felt by the hands when moistened with acidulated water. 

 I repeated several times the first experiment, and do not believe 

 that there was any error in the mode of experimenting ; so that 

 we may conclude that, if there exist an electric current proceed- 

 ing from the combination of bodies, it possesses very different 

 properties from that which takes place during the decomposition 

 of an electrolyte. 



33. 



During my late stay in Berlin, in September of last year, 

 (1834), Professor Dove, Member of the Royal Academy of 



