Intelligence and Miscellaneous Articles. 75 



on the diffusion of cane-sugar, as well as the analogous experiments 

 of Voit, show such wide deviations from the theory that the cal- 

 culation of them according to the formulas derived from it has no 

 meaning. 



Further, the experiments instituted by Johannisjanz, after the 

 prism method described by Kundt, are considered, of which the 

 formal differences from the theory do not appear to be great ; yet 

 the coefficient of diffusion of common salt through water, calcu- 

 lated from them, • namely 0*45, is too little by more than half. 

 Erom the determinations made by Pick upon the same salt, the 

 values 094 for 15° and 1*13 for 20° temperature are deduced for 

 this coefficient ; and these values agree with Graham's experiments, 

 as well as with some to be subsequently published. 



The great errors by which the results obtained by optical methods 

 are affected proceed from the fact that the hypothesis on which 

 those methods are based, viz. that a horizontal beam of light which 

 falls upon a vertical plane bounding a diffusing liquid remains 

 horizontal during its passage through the liquid, is incorrect. 

 Such a liquid, bounded by two parallel sides whose density dimi- 

 nishes from below upwards, behaves like a prism whose refracting 

 edge is directed upwards ; or, inasmuch as the diminution of 

 density of the liquid is not uniform from below upwards, it ex- 

 hibits, together with the properties of a prism, also those of a 

 cylindrical lens. Several experiments are described in the memoir 

 by which these peculiarities of solution are proved. 



The author, in conclusion, refers to the analogous behaviour of 

 sound when it is propagated in or against the direction of a wind 

 the velocity of which increases upwards, from which behaviour 

 Stokes first explained the fact that in the former case a sound is 

 heard at very great, in the latter at only very short distances. — 

 Kaiserliche Akademie der Wissenschaften in Wien, mathem.-naturw. 

 Classe, Dec. 5, 1878. 



ON THE SPECIFIC HEATS AND HEAT OF FUSION OF GALLIUM. 

 BY M. BERTHELOT. 



1. M. Lecoq de Boisbaudran having had the kindness to place at 

 my disposal an ingot of gallium weighing 34 grams, I have deter- 

 mined its specific heat in both the liquid and the solid state, and its 

 heat of fusion. I worked according to my usual methods and with 

 the aid of my water calorimeter. It is known that gallium fuses at 

 -f 30°, but may be kept liquid, in the state of superfusion, down to 

 near zero. 



2. Two trials, one made between 119° and 13°, the other between 

 106° and 12 0, 5, gave 0*0802 as the value of the specific heat of 

 liquid gallium. 



3. The specific heat of solid gallium, between 23° and 12°, was 

 found to be equal to 0'079. 



This quantity must not be measured too near the melting-point. 

 Two trials made between 28° and 13°, great care being taken not 

 to heat the metal above 28 c , in order not to melt it, gave the ab- 

 normal values 0-275 and 0*352 ; but I perceived, at the same time, 



