511 
Mr. Lubbock on the Heat of Vapours^ %c. 
From the above I have deduced the following Table for 
Fahrenheit’s scale : 
Merc, therm. 
Air therm. 
Merc, therm. 
Air therm. 
212 
212 
482 
478-1 
302 
2997 
572 
558-9 
392 
3867 
680 
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, 0 being 
reckoned in Fahrenheit’s scale and from the freezing point of water, 
0=1 0 = 180 ” =480° 
^ u 
p = 11-632 Sf = 334-7 
p" = 23-934 0" = 396-4 
I find from these observations 
^ =[0-1140623], 
P' — 1 
i- + 6' = 814-7 
cc 
i- + r = 876-4. 
a 
the quantity within brackets being the logarithm of the corre- 
sponding number ; and hence I find 
j3 = -0134* -98677 —= 1-0134 
' r 
1-17602 log jS = -0704184 JI= 6-6809. 
The pressure at the boiling point of water (212°) being unity, 
Jl [2-0651059] 
^ + p *0134 _ 1.1^002’ 
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 iue to be the only one which w ill satisfy the equation. 
