W. J. M. Rankine, Esq., on the Elasticity of Vapours. 



39 



The results of Dr Ure's experiments on the vapours of tur- 

 pentine and petroleum, are so irregular (as the diagram shews), 

 and the range of temperatures and pressures through which 

 they extend so limited, that the value of the constant 7 can-" 

 not'be determined from them with precision. I have, there- 

 fore, endeavoured to represent the elasticities of those two 

 vapours approximately by \}i\Q first two terms of the formula 

 only, calculating the constants from two experimental data 

 for each fluid. The equation thus obtained 



° t 



is similar in form to that of Professor Roche. 



The data, and the values of the constants, are as fol- 

 lows : — 



Although the temperatures are much higher than the boil- 

 ing point of water, I have not endeavoured to reduce them 

 to the scale of the air-thermometer, as it is impossible to do 

 80 correctly, without knowing the nature of the glass of 

 which the mercurial thei'mometer was made. 



