Page:Scientific Memoirs, Vol. 2 (1841).djvu/25

 Rh causing it to pass through 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 galvanometer, 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 analogy 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 will perhaps be the proper place to relate the following experiment which I performed. Every one is well acquainted with the remarkable arrangement, presented by M. Becquerel to the French Academy of Sciences, in its meeting of the 7th December, 1835 (L'Institut, No. 135). Assisted by Professor Göbel, I constructed a similar battery, which developed a considerable quantity of gas at the platina plate immersed in an alkaline solution. When the galvanometer had been interposed, there was a deviation 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 secondary circuit, the tongue, or any flaying of the skin. To institute a comparison, I constructed a very small pile of copper, of zinc, and very diluted sulphuric acid, of which I set only sufficient 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 was visible, and a very feeble discharge 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 proceeding from the combination of bodies, it possesses very different properties from that which takes place during the decomposition of an electrolyte.

During my late stay in Berlin, in September of last year, (1834), Professor Dove, Member of the Royal Academy of