4.72 



same as that of air (steam =^y, air= i ), and so on in other cases. 

 The mean coefficient of expansion at zero of temperature from seven 

 experiments below the pressure of the atmosphere, and calculated 

 from a point several degrees above that of saturation, is -^J-g-, whereas 

 for air it is ^J-^. Hence it would appear that for some degrees 

 above the saturation point the steam is not decidedly in an aeriform 

 state, or, in other words, that it is watery, containing floating vesicles 

 of unvaporized water. 



Table of Results, showing the relation of density, pressure, and 

 temperature of saturated steam. 



Adopting the notation previously employed, and putting r for the 

 rate or coefficient of expansion of an elastic fluid at t l temperature, 

 we find V 2 p 2 



r=_L_=SI_, (4.) 



where = the rate of expansion at zero of temperature. In the case 



of air l = 459. 



The following Table gives the value of the coefficient of expansion 



