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Electro-Magnetism: new Experiments. 117 
On examining the path left by the spark, it is seen to consist of a white 
and opake fillet extremely slender, the whole length of which presents 
bright places of two or three millimetres directed successively like a spi- 
ral in different azimuths. It shows no metallic deposit. In the thicker 
plate this track bifurcates at a depth of about one-third of the thickness. 
Almost at the opposite face it again subdivides into many fillets, very 
fine and almost destitute of the bright places. 
the experiment, Ruhmkorff demonstrated, by the appearance 
Hlectro-Magnetism ; Ni 
ew Hxperiments.—Mr. Le 
€ssor at the Polytechnic School, has recently made some very curious 
twenty centimetres, and there was required for this purpose only a dozen 
elements of Bunsen’s battery. When it is desired to avoid incandescence 
and to have a very long conducting wire, it is better to employ silver, 
Which offering less resistance causes less diminution of the current. With 
4 silver wire of one-fifteenth of a millimetre in diameter, ten elements of 
unsen’s battery are sufficient to produce through a length of forty or 
fifty centimetres the interesting results we are about to consider. 
©quatorial position. Such a conducting wire is attracted by a mass of 
"ton: this is the counterpart of the original experiment of Arago that 
® conjunctive wire attracted iron filings when it was traversed by a cur- 
rent. The experiment of Leroux generally succeeded best when the mass 
a tly, Leroux showed how a fine conjunctive wire could be made to 
Coil itself spontaneously around the pole of a magnet when it was placed 
ition. : 
Same Magnetism which it alread For the more convenient 
7 y . e 
Performance of this experiment, and to render it, so to speak, more gen- 
* Aimant bifurqué; this Journal, [2] xv, p. 381. 
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