SCIENTIFIC NE\V&. 373 



2. If a communication be opened between two equal 

 spaces, one a vacuum, the other filled Avith a gas, the vari- 

 ations of temperature, positive in one and negative in the 

 other, are equal in quantity, but not in intensity. 



3. In the same gas these variations are proportional to the 

 change of density it undergoes. 



4. The variations in different gases are so much greater, 

 in proportion as their specific gravities are less. 



5. The capacity of a gas for caloric in a given volume di- 

 minishes with the density. 



6. The capacities of gases for caloric, in equal volumes, 

 are so much greater, as their specific gravities are less. This 

 consequence will be evident to those who know the experi- 

 ments, by which Mr. Gay-Lussac had already proved, that 

 all gases are equally affected by equal elevations of temper- 

 ature. 



Mr. Cotte, correspondent of the Institute, has compared Progress of 

 the progress of several thermometers, both of mercury an d»co^p^eif bofli 

 alcohol, in various expositions, during the hottest days of mercurial and 

 the three memorable summers of 1802, 1803, and 1806. SJpim ' 



Two of these thermometers, one mercurial the other in doors and 



spirit, were placed out of doors in the shade, and facing the out ,\ in the stm 

 17 r »•■,•*. * and m tllc 



north; two others were exposed to the direct rays of the shade. 



sun ; and two were within doors. All of them were con- 

 structed with the greatest care, and under the inspection of 

 different members of the Academy of Sciences. Before 

 Mr. Cotte examined the effects of different exposures, he 

 determined, by taking the mean of a great number of ob- 

 servations, the comparative motions of these thermometers 

 in the same situation. 



It follows from these experiments, that the differences be- Differences be- 

 tween the mercurial and spirit thermometers are much more tw « ea mercury 

 r and spirit greai> 



considerable, when they are exposed directly to the rays of est in the sun 



the sun ; which Mr. Cotte ascribes chiefly to the red colour 

 of the spirit: and this difference is greater, the greater the 

 heat. 



The greatest hourly variation takes place from 6 to 7, Hourly varii- 

 and more especially from 7 to 8 in the morning ; it continues 

 diminishing till 11 ; thence it increases till 2 \ and between 

 % and 3 it diminishes a little. 



The 



