66 RegnauWs Researches upon the Dilatation of Gases. 



" Thus I adopt for the coefficient of the dilatation of dry air, 

 for every degree of the Centigrade scale between the two fixed 

 points of the thermometer, 0.003665."* 



To this part there is a note, which is as follows: "M. Babinet 

 has remarked to me, that in adopting for the coefficient of the di- 

 latation of the air 0.366666 . . . this coefficient is represented by 

 the fraction ii, which is very convenient to employ in calculation." 



" The former coefficient admitted for the dilatation of air be- 

 ing found inexact, it is evident that we cannot regard as demon- 

 strated, that it is the same for all gases, and new experiments are 

 necessary to decide whether this law be rigorously true or only 

 approximative. 



"I have made experiments upon nitrogen, hydrogen, oxide of 

 carbon, carbonic acid, sulphurous acid, cyanogen, protoxide of 

 nitrogen, hydrochloric acid and ammonia." 



The following are the results of his experiments compared 

 with air, dilatation between 0° and 100° Cent. 



Regnault has just published a second series of experiments, 

 and the coefficients for some of the gases have been changed ; 

 the reason for it will be seen in what he says. 



" In all the experiments that have been as yet described, the 

 dilatation of the gases have been determined in an indirect man- 

 ner. The increase of the elastic force of a certain volume of 

 the gas under an elevation of temperature was measured, and 

 from this the dilatation deduced, supposing Marriotte's law to be 

 correct. But, one can object by saying that this law is not de- 

 monstrated to be absolutely exact even for air." 



" To leave no doubt as regards this mechanical theory of gas, 

 I have made a new series of experiments, by means of a process 



* This would be for every degree of Fahrenheit's scale 0.002036. 



