610 SCIENTIFIC RECORD FOR 1683. 



Eoiti has not succeeded in reproducing these phenomena in solutions, 

 either of zinc sulphate or ferric chloride, or even in a thin layer of 

 mercury. He suggests that the results may be due to the fact that the 

 conductor under the action of the magnet ceases to be electrically iso- 

 tropic, and has a different resistance in different directions. (Phil. Mag., 

 V, xn, 157; xv, 341; Atti Accad. Lincei, III, xn, 397 ; J. Phys., No- 

 vember, 1883, II, ii, 509, 512, 513.) 



Hamautoff has measured the electromotive force developed by the 

 contact of silver, silver nitrate, and the various developing agents. 

 Ferrous sulphate gives 0.01 Daniell, pyrogallic acid, 0.08 ; while the 

 rapid developers suggested by Boissonas for instantaneous plates give 

 0.12 to 0.16. This supports Lermantoff's view that development is a 

 galvanoplastic process, each molecule of metallic silver set free by the 

 light on the sensitive surface forming a voltaic couple with the silver 

 nitrate molecule and the ferrous sulphate molecule, resulting in a de- 

 posit of metallic silver. In order to demonstrate the currents produced 

 by the action of light on a silver plate coated with silver iodide, Borg- 

 mann has combined seven cells together and obtained, even with dif- 

 fused light, a notable deflection on Wiedemann's mirror galvanometer. 

 (J. Phys., December, 1883, II, n, 580, 581.) 



Preece has studied the effect of temperature on the electromotive 

 force and resistance of batteries, and concludes (1) that the electromotive 

 force is not materially affected by changes of temperature, (2) that the 

 internal resistance is affected materially according to a law special for 

 each form of cell, and (3) that the resistance of a liquid is greater on 

 a cooling than on a rising temperature. (Proc. Roy. 8oc, xxxv, 48; 

 J. Phys., October, 1883, II, n, 475 ; Nature, March, 1883, xxvn, 42G.) 



Trowbridge and Stevens have measured the electromotive force of 

 alloys, using mixtures of lead and tin and of copper and zinc. The 

 composition was determined by analysis and the electromotive force in 

 dilute sulphuric acid with a platinum plate for the positive pole. (Proc. 

 Am. Acad., xviii ; Phil. Mag., December, 1883, V, xvi, 435.) 



Hagahas concluded from his experiments that the currents produced 

 in amalgamation of metajs are thermoelectric currents due only to the 

 heat of combination. (Wied. Ann., XVII, 897; J. Phys., May, 1883, II, 

 II, 232.) 



If two electrodes of the same metal be plunged in a liquid, the move- 

 ment of either within the liquid produces a current. Krouchkoll has 

 investigated this phenomenon and has shown that currents are also 

 produced at the instant of immersion and of emersion, and that the 

 former is opposite to, and the latter in the same direction as, the current 

 which movement in the liquid produces. (J. Phys., November, 1883, II, 

 II, 505.) 



Bartoli and Papasogli have constructed a battery consisting of gold 

 or platinum for one plate and gas carbon for the other, immersed iu an 

 alkaline solution. The carbon is here negative and the electromotive 



