REGNAULT’S HYGROMETRICAL RESEARCHES. 659 
Psychrometer. Gundersen! & Fraction of saturation. 
t. v. t—t!. . Condenser. | Psychrometer. 
° °o ° ° mm 
20:12 17°37 2°75 15°39 700 0:7437 0°7632 
20°68 16°77 3°91 15°34 Bae 0°7157 06746 
20°56 16°91 3°65 14:99 sina 0-7047 06987 
20°92 18-45 2-47 16°62 585 0°7651 0°7903 
20°55 18-29 2:26 1670 ode 0:7864 0°8055 
20°32 18-22 2:10 16°63 of 0-7942 0°8177 
13°50 11-53 1:97 9:22 Bae 0°7542 0:7937 
13°60 11:56 2-04 9:32 ae 0:7548 0:7871 
13°44 11-51 1:93 9:37 acc 0°7652 07975 
1413 11-97 2°16 9:43 | Bet 6°7350 07786 
x 
f 
than those deduced from the observation of the temperature of 
the dew-point on the condenser. The experiments of M. Marié 
give, in general, the same result. These determinations show, 
that by adopting, for the observations made in the open air, the 
numerical formula 
The experiments of M. Izarn give for = rather greater values 
0-429 (t — #) 
ai alia CS Alama 
we obtain elastic forces x a little too high ; it would consequently 
suffice, to approach more to the real values, to replace the co- 
efficient 0429 by rather a greater coefficient. The coefficient 
0°480 gives an almost perfect coincidence between the calculated 
results and those found by direct observation, in the fractions of 
saturation which exceed 0°40; but it produces a difference 
greater than the coefficient 0°429, and in an inverse direction 
for weaker fractions of saturation. It appears hence to result 
that the coefficient B of the formula (4) depends on (f — 7’); 
this evidently results from the fact that the air carries off pro- 
portionally more vapour when it is very dry than when it ap- 
proaches saturation. 
To represent the determinations made in enclosed spaces, like 
those in Tables III. and IV., it would be necessary to adopt a 
much higher coefficient. 
I shall abstain for the present from establishing a new for- 
mula of the psychrometer; I do not consider the elements at 
my disposal as sufficient; I am engaged on determining by di- 
rect experiments the value of a, that is to say, the latent heat 
which water absorbs on evaporation in air at a determined tem- 
VOL. 1V. PART XVI. 3A 
