658 REGNAULT’S HYGROMETRICAL RESEARCHES. 
TaBLe V.—Ewperiments in the Class-room of Physics, with the 
two opposite windows open. 
/ aor pe 
t. tl. ai eee: ho. Dp. = 
: 
A mm 5 
750-97 | 0382 | 0-444 | 0-469 
17-21 | 11:50 | 11-62 753-06 | 0394 | 0468 | 0-486 
17-45 | 11-60 | 11-71 752-56 | 0-389 | 0-454 | 0-478 
17-49 | 11-54 | 1160 | 5-92 
5-65 
5:80 
13-01 | 10-05 | 10:11 | 2-93 | 755-73 | 0-431 | 0665 | 0-683 
3-29 
4-28 
3-91 
14-05 10°72 10-80 755°68 | 0-440 0°636 0658 
16-19 11:88 11°95 75511 | 0-450 0570 0589 
16-20 12°25 12°33 754-70 | 0-474 0:598 0°623 
These experiments demonstrate in the most evident manner 
that the same formula is not applicable to these different cases. 
I have endeavoured to ascertain whether one and the same 
formula might be adopted in experiments made in the open air, 
but under very different pressures of the atmosphere. For this 
it was necessary to perform in very elevated localities the same 
experiments that I had made at Paris; not having time for these 
experiments myself, I requested M. Marié, one of my pupils, to 
perform them. 
This young savant made two series of experiments, one at 
Saint Etienne, in May and June 1843, under a mean barome- 
trical pressure of 705 millimetres; the other, on Mount Pila, 
under a pressure of 655 millimetres. 
The experiments of M. Marié were made by the same methods 
as my own, but they present much greater irregularities. These 
experiments were made under unfavourable circumstances; the 
thermometers often varied several degrees during the same ex- 
periment ; it then becomes very difficult to value by calculation 
the mean quantity of moisture, unless the observations of the 
thermometers are made at very close intervals of time, which 
unfortunately was not the case in the experiments of M. Marié. 
Lastly, M. Izarn has been kind enough to make some expe- 
riments in the Pyrenees during the month of July 1844. These 
last experiments were made by observing, on one hand, the in- 
dications of the psychrometer which was employed for the ob- 
servations in Tables No. I., second series, and No. III., and by 
determining, on the other hand, the point of saturation of the — 
air by means of my condensing hygrometer. 
