REGNAULT’S HYGROMETRICAL RESEARCHES. 615 
the pressure of 760 millimetres, was determined by direct ex- 
periments. 
The density @ of the vapour with relation to the air taken 
under the same circumstances of temperature and pressure will 
be expressed by the formula 
py id pbc ay bia 
a 1+kT A 
The following are some numbers obtained in this manner :— 
== 1 ers O03 7 
p =28"Ms-959 ; 
hp =378™72 alee petite Ge) 
T =99°91. 
Weight of the vapour at 0°, and under a pressure of 760™™, 
P =828"™s-0965. 
p= 2e"802 
| EE EY facet | 
T —99°14 Sins ecebteeahe: banka 
P =8s"ms-1052. 
p =—1e™ 261 
hy =161™™'32 
T —99°-63 a, Jee 
P =8stms-0941, 
p =2e™s-696 
f= 340" 20 
e . ° e e I . 
T =99°-78 GYa 
Poe Osas. 
We deduce from these four experiments,— 
Weight of vapour. Density. 
J sctias> fs Q20oeTms. 0°62311 
RR th a 0°62377 
A in oh too OAL ave 0°62292 
TN a sik ies Se UD. and 0°62229 
These densities differ little from the theoretical density 0°622, 
and from the density 12 given by M. Gay-Lussac. 
By applying the same method to the determination of the 
density of aqueous vapour taken under pressures approaching 
760 millimetres, we obtain perceptibly higher numbers. This 
may result from the vapour being, in this case, at a tempera- 
