PHYSICS. 463 



of the least stable hydride, and its reduction by oxygen, both processes 

 evolving heat. {Comptes Bendus, May, xciv, p. 1377.) 



D.ebray has examined certain alloys of zinc with the platinum met- 

 als which are peculiar. That with osmium takes fire almost explo- 

 sively on heating to 300° C. The alloys of rhodium and ruthenium, but 

 especially iridium, suddenly evolve a large amount of heat when 

 raised to the same temperature. The author regards these changes as 

 physical, isomeric modifications being produced with the evolution of 

 heat. {Comptes Bendus, June, xciv, p. 1557.) 



2. 0/ Liquids. 



Koch has determined the influence of temperature upon the constant 

 of internal friction of mercury, measuring the time required by a given 

 quantity of mercury to pass through a capillary tube from one reservoir 

 to another under a known pressure and at a determined temperature 

 The result shows that this constant, like that of other liquids, dimin- 

 ishes as the temperature rises, at first rapidly, then more slowly, accord- 

 ing to an equation given in the memoir. The numerical values agree 

 with those previously obtained by Warburg. {Wied. Ann., xiv, p. 1; 

 J. Phys., April, II, i, p. 186.) 



In the report for 1881, Bjerknes's hydrodynamic apparatus was men- 

 tioned. Bertin has given a much fuller account of it, illustrated with 

 woodcuts. {Ann. Chim. Phys., February, Y, xxv, p. 257.) 



Decharme has repeated these experiments and has extended them, 

 using in place of pulsating or vibrating bodies currents in air or water, 

 either continuous or interrupted. Modifying the old experiment of 

 Clement Desormes, in which a disk is attracted when placed close to a 

 jet of gas thrown normally against it, by employing a jet of water, the 

 author finds a tin plate a square decimeter in area strongly attracted 

 when placed 2 or 3"°™ from the aperture. "With liquids only one disk 

 is required, and this is fixed, the jet being movable. When held 4 or 

 5imn from the plate the attraction is very decided. This the author 

 calls a hydro-electro magnet. Using two tubes, one with a thick edge 

 and the other with a thin one, the phenomenon of an electro-magnet 

 with two unlike poles is obtained. Hydro-induction the author has 

 also produced. {Ann. 'Chim. Phys., April, V, xxv, pp. 554, 570.) 



The extremely discordant results of experiments to measure the co- 

 efficient of difiiisibility of liquids has led to new determinations by 

 Wroblewsky, using a photometric method. Using solutions of chemi- 

 cally pure salt, of three different densities, he finds that for a given 

 time and within the limits of concentration indicated, the coefficient of 

 diflfusibility diminishes proportionally to the quantity of salt in solu- 

 tion. {Wied. Ann., xvi, p. 606; J. Phys., January, II, i, p. 39.) 



Martini j)roduces diffusion figures by the following means: In a glass 

 vessel two liquids are placed, of nearly the same density; as, for ex- 

 ample, water and a solution of salt or sugar. They are left at rest for 



