Mr. Lubbock on the Heat of Vapours, Sfc. 



3 abo^ 

 Fahrenheit's scale 



511 



From the above I have deduced the following Table for 



Merc, therm. 



Air therm. 



Merc, therm. 



Air therm. 



2°12 



302 

 392 



212 



2997 

 386-7 



482 

 572 



680 



47°8-l 

 558-9 

 662-0 



I now proceed to determine for steam the constants y and E by 

 means of the observations of Dulong; and Arago which I have 

 quoted in the preceding page. 



For the air thermometer on Fahrenheit's scale the experiments 

 of Dulong and Arago (Mem. de V Institute vol. x.) give, 9 being 

 reckoned in Fahrenheit's scale and from the freezing point of water, 



2? = 1 9 = 180 



--=48C 

 a 



r 



p = 11-632 9' = 334-7 



a 



= 814-7 



p"= 23-934 0"= 396-4 



a. 



^ 876-4. 



find from these observations 







-i — ^ _ rno 1 /infiQQl 







y^ _ 1 •- 



the quantity within brackets being the logarithm of the corre- 

 sponding number ; and hence I find 



;S = -0134* y= -98677 — 



y 



£=1-17602 WjE; === -0704184 



1-0134 

 H=. 6-6809. 



The pressure at the boiling point of water (212°) being unity, 



1 



_ + i 



[2-0651059] 

 p-oi3i_ 1.17602' 



so that if T is the number of degrees on Fahrenheit's scale of the air 

 thermometer, and the pressure p be reckoned in atmospheres. 



This value of /3 appears to me to be the only one which will satisfy the equation. 



