402 SCIENTIFIC RECORD FOR 1882. 



theory of Exner, and fouud it in error. {J. Pliys., December, II, i, p. 

 574.) 



Ewing and Jenkin liave observed that a wire of iron or steel sub- 

 mitted to the action of a magnetizing helix yields, when twisted, an 

 instantaneous longitudinal current directed from the north to the south 

 end when the torsion is in the direction of an ordinai'y screw, and from 

 south to north when the torsion is in the other direction. On reversing 

 the longitudinal magnetization of a wire submitted to torsion, a moment- 

 ary energetic current is produced ; but the interruption or re-establish- 

 ment of the current produces only a trilling effect. A magnetized wire 

 not under the action of an external magnetizing force also gives a cur- 

 rent when twisted, in the same direction as before. The authors give 

 the name "polarization" to the state produced in a wire by the super- 

 position of a torsion and a longitudinal magnetization, a state which 

 persists after the magnetizing force ceases; it is measured by the mo- 

 mentary current which accompanies its production. The molecular 

 condition opposing magnetization, ordinarily called coercitive force, the 

 authors call hysteresis. {Froc. Roy. Soc, xxxiii, p. 21; J. Fhys., July, 

 II, I, p. 332.) 



Felice shows to an audience the fundamental fact that in the interior 

 of a battery the current goes from the zinc to the copper by using a 

 cell of considerable length and suspending a needle just above the 

 liquid. ('/. Phys., December, II, i, p. 571.) 



Bennet has constructed a cheap form of battery which can be made for 

 sixpence. An iron meat or milk can forms at the same time the nega- 

 tive plate and the containing vessel. In it is a porous cup containing 

 a zinc plate passing through a paraffined cork as cover. The liquid 

 used is caustic soda, which is electronegative to zinc, and in which iron 

 does not rust. Its electromotive force is 1.23 volts. Iron filings round 

 the i)orous cup facilitate depolarization. At a subsequent meeting of 

 the London Physical Society, Lecky stated that the electromotive force 

 of the Bennet cell as determined by Guthrie was 1.14 volts, the internal 

 resistance being 0.8 ohm; both quantities varying somewhat. McLeod 

 also gave the results of his tests. On charging, the electromotive force 

 was 1.005 volts, but on standing three days it rose to 1.213 volts. The 

 internal resistance was 1.007 ohms. {Nature, May, June, xxvi, ])p. 71, 

 119.) 



Wright, in a paper presented to the London Physical Society, gives 

 the results of his investigations on the Daniell cell, as a ])art of his more 

 extended research on the determination of chemical affinity in terms of 

 electromotive force. He concludes that when a Daniell cell is made 

 with equal-sized plates of pure zinc and j)ure copper, immersed re- 

 spectively in solutions of pure zinc and copper sulphates of the same 

 density, and is made to generate a current not exceeding in density 8 

 microamperes i)er square centimeter, an electromotive force is set up 

 always lying iairly close to 1.115 volts, and practically identical with 



