394 Foreign Literature and Science. 



with iodine of a purple, while on the contrary, the insoluble 

 part acquires a blue color. — Idem. 



3. Specific heat of the gases. — A memoir on this subject, 

 so important in all theoretical discussions upon the physiology 

 of respiration and animal heat, by Aug. De La Rive and F. 

 Marcet, was read before the " Soci-te de physique et d'his- 

 toire naturelle"' of Geneva, on the 19th of May, 1327. After 

 a statement of the difficulties attendant on the practical inves- 

 tigation of the question, and the sources of fallacy which they 

 conceive interfered with the results of their predecessors, and 

 especially with those of De La Roche and Bfrard, the au- 

 thors explain their procedure, and arrive at the following con- 

 clusions. 



" 1. That under the same pressure, and in equal and con- 

 stant volumes, all gases have the same specific heat. 



2. That all other circumstances being the same, the spe- 

 cific heat diminishes, cotemporaneousiy with the pressure, 

 and in an equal degree in all the gases, following a progres- 

 sion slightly convergent and in a ratio much less than that of 

 the pressure. 



3. That each gas has a different conducting power ; in 

 other words, all gases have not the same power to commu- 

 nicate heat." 



" We are of opinion (say the authors) that it is to the want 

 of attending to this last property, that we are to attribute 

 the great difference which is found in the result of different 

 experiments on this subject. In fact, a simple variation in 

 the volume of the gases, may, in many cases, totally change 

 the result ; thus M. M. Clement and Desormes, who endeav- 

 oured to determine the specific heat of the gases, by the 

 sudden cooling of large masses, found a very considerable 

 difference for the expression of the capacity of caloric in 

 each gas. In the same manner M. Gay Lussac, in employ- 

 ing considerable volumes, did not find that equality of spe- 

 cific heat, which he had obtained with smaller volumes, and 

 what proves that this remark is well founded, is that the re- 

 sults have always varied in the precise manner in which a 

 difference of conductibility ought necessarily to cause them 

 to vary. 



Theoretically considered, it was not improbable that the 

 gases, which have all an equal dilatation, and in which this 

 dilatation remains uniform at all temperatures, should have 



