372 SCIENTIFIC NEWS. 



another well known, which is, that a volume of air inclu- 

 ded in the receiver of an air-pump continually absorbs ca- 

 loric as it dilates under the rising piston. It may be said, 

 that the vacuum in the second globe was not sufficiently per- 

 fect, and that the air remaining in it, being compressed by 

 the additional quantity admitted, was obliged to give out 

 part of the air it contained : but this explanation Mr. Gay- 

 Lussac refutes, first by reasoning, and afterward by a di- 

 rect experiment. 

 and this in pro- If the alcohol ascend in the second thermometer, it de- 

 Sensit" t0 tS ? cends nearl 7 illc same quantity in the first. Now if, after 

 having exhausted the second globe, the communication be- 

 tween them be opened, the gas, equally distributed, will be 

 reduced to half the density it had before; and one of the 

 thermometers will be seen to rise, and the other fall, each 

 in an equal degree, but less than before, in consequence of 

 the diminution of density. And if, by repeating the ex- 

 haustion, the density be reduced to half M r hat it was in the 

 second trial, and consequently to £ what it was in its origi- 

 nal state, Ave shall find the equal and opposite variations of 

 the two thermometers still following the ratio of the density. 

 Other Rases Similar experiments, made with particular attention, on hi- 

 pioducec tie d r0 g en? oxigen, and carbonic acid gas, produced similar 

 mena. results • that is to say, the quantities of caloric absorbed 



in the first globe, and evolved in the second, were always 

 equal to each other, and proportional to the density. 

 Contrivance for To render the experiments comparable with each other, 



equalizing the j t was nC cessarv, that the time occupied by all the different 



time of trans- J 7 r J 



mission of the gases in their transmission from one globe to the other should 



S as - be the same. This Mr. Gay-Lussac effected by a contriv- 



ance equally simple and ingenious, which diminished the ori- 

 fice of the connecting tube in the ratio of the square, root 

 of the densities : and thus the time of transmission for all 

 the gases was found to be eleven seconds. 



Of these experiments, which deserve the attention of the 

 natural philosopher, and which Mr. Gay-Lussac purposes 

 to verify and extend by farther observations, the following 

 are the results, which however he offers with some diffidence. 



feenteral results 1. When a vacuum comes to be occupied by a gas, the 



d{ the experi- caloric evolved is not owing to the Utile air that might be 

 ments. , ; . ; 



left in it. 



2. If 



