476 SCIENTIFIC RECORD FOR 1884. 



product of the magnetic moment by the magnetizing force multiplied 

 by a constant, increasing with the frequency of interruption of the cur- 

 rent, and still more when the current is alternated. {Nature^ Jidy, 1884, 

 XXX, 223.) 



Warburg and Honig have also experimented in the same direction, 

 and have come to the conclusion that a large proportion of the heat 

 observed, nearly 75 per cent., is due to magnetic friction. {Am. J. 8ci., 

 March, 1884, III, xxix, 238.) 



2. Electric Generators. 



Kalischer has tested the hypothesis that the condensation of steam 

 may be a source of electrification, using twelve largo glass vases covered 

 with tin foil and filled with ice, placed on a sheet of tinned iron, insu- 

 lated by a block of glass ; the whole being placed within a large insu- 

 lated metallic box, the metallic cover of which was perforated to allow 

 the access of air. An insulated wire connected the sheet of iron on 

 which the vases rested with one of the pairs of quadrants of a Kirchhofl 

 electrometer, the other pair being put to earth. The atmos|)heric 

 moisture condensed on the outside of the vases. The observed devia- 

 tions of the electrometer were of the same order of magnitude whether 

 the vases were empty t)r full of ice, being sometimes in one direction, 

 sometimes in the other. The best results were obtained, however, by 

 compressing air into a glass reservoir, connecting the metallic rod pass- 

 ing into its interior with the electrometer. During the expansion the 

 moisture condensed on the rod, but the needle showed no deviation. 

 It cannot, consequently, be affirmed that condensation of aqueous vapor 

 is a source of atmospheric electricity. ( Wied. Ann.., xx, 614 ; J. Phys., 

 May, 1884, II, iii, 219.) 



It is generally assumed that ordinary zinc is i^ositive to amalgamated 

 zinc in a solution of zinc sulphate. But Eobb has shown that if care 

 be taken to employ pure zinc, and solutions of sulphate free from acid, 

 the couple shows no sensible electro-motive force. Lippmann has 

 discussed this result, and shows that the contrary result is in direct 

 contradiction to the second law of therrao-dynamics, since the action of 

 the current developed would cause the deposition of zinc on the pure 

 zinc, which could then be amalgamated again, and so on; a finite quan- 

 tity of work being done at the expense of the amalgamation only. With 

 cadmium in cadmium sulphate, however, the polarity is reversed, and 

 hence there is no conflict, with the above law. {J. Phys., September, 

 1884, II, III, 388.) 



Carhart has determined the relation between the electro-motive force 

 of a Daniell cell and the strength of the zinc sulphate solution, employ- 

 ing for the purpose the compensation method of Poggendorft". With 

 a 1 per cent, solution the electro-motive force was 1.125 volts ; 3 per cent., 

 1.133; 5 percent., 1.142; 7^ per cent, 1.120; 10 per cent., 1.118; 15 per 

 cent, 1.115; 20 per cent., 1.111 ; and 25 per cent,,. 1.111; the mean of 



