348 SOCIETY OF PHYSICS AND NATURAL HISTORY, OF GENEVA. 



the pbenonienon is more intense when the water is clearest, and that the 

 polarization takes place for all parts of the spectrum equally. Dis- 

 turbed or muddy waters give no polarization. The same physi(;ist has 

 also given an account of some experiments he has made in order to verify 

 the results obtained by M. Christiansen and by M. Kundt, upon the ab- 

 normal dispersion of the light of bodies of superticial colors. The two 

 works which I have mentioned have been published in the Archives of 

 Science, and I refer you to them. M. liaoul Pictet has presented a paper 

 on the resistance a body experiences in its motion through the air, with a 

 uniform velocity. It would be difficult to give an analysis of it in a few 

 words. This resistance is expressed by the formula 11 = Kv-, which is 

 indicated by calculation, and experimentally verified. 



The same savant has repeated, at the meetings of the society, var- 

 ious experiments, having for their object to show the emissive and 

 absorbent powers of ice for heat, and the influence which they exercise 

 upon its formation and its fusion. In order to prove experimentally 

 the radiant power of ice for black heat, M. Pictet has made a piece of 

 ice contract rapidly by the action of this radiancy, in immersing it 

 at the level of the surface of water at 0°, and in exposing it to the 

 air under a serene sky. From another side he has shown that ice is 

 almost entirely diathermal for luminous heat, and altogether diathermal 

 for black heat. In i^rojecting a ray of luminous heat through a block of 

 ice inclosing specks of foreign bodies there is formed around each corpus- 

 cle a drop of water, resulting from the absorption of the black heat which 

 these bodies radiate under the luminous rays ; and when these foreign 

 bodies are sufficiently luimerous the ice is disintegrated through its 

 entire^ depth, and is melted. If, on the contrary, a ray of black heat is 

 projected upon the block of ice, as this does not penetrate into the sub- 

 stance of the ice, it produces a fusion of the superficial stratum only, 

 and does not attect the interior parts. 



Professor ^larignac has communicated to us the result of his researches 

 upon the specific heat of saline solutions. (Inserted in the Archives, 

 vol. XXXIX, page 217.) 



M. Morin read a memoir upon the azotized substances found in the 

 embryos of herbivorous animals, and especially in their eggs. 



Our emeritus member, M. Dumas, has laid before the society various 

 important questions, which were discussed by the Academy of Sciences 

 at Paris during the siege of that capital. The necessity of having re- 

 course to balloons for carrying on correspondence led to various improve- 

 nu'uts in the art of a'ronautics. It was necessary, on account of economy, 

 to construct the balloons of cotton material, and in order to render this 

 im])ermeable, a varnish of India rubber was used. But M. Dumas showed 

 that India rubber is permeable to gas, and proposed to superimpose on it 

 some substances soluble in water, especially gelatine. By superposing 

 the two substances, a varnish was obtained impermeable both to gas 

 and the moisture of the air. It was also observed that it was best to 



