630 REGNAULT’S HYGROMETRICAL RESEARCHES. 
A second series of observations was made on three other hy- 
grometers of M. Bunten and on the same hygrometer of Paul, 
placing the four hygrometers in a cylindrical glass vessel, closed 
hermetically, and containing a layer of sulphuric acid more or 
less diluted. The results contained in Table II. were thus ob- 
tained :— 
TaBLe II. 
Hygrometers of Bunten. Berane 
merits) he ele Be of Paul. 
4, 5. 6. 
102 12:0 113 10-4 
23:0 23°9 23°6 17°5 
35°9 381 36:2 27°4 
55°6 57°6 55°6 42-6 
67:3 69°5 66°8 52°0 
75'8 776 751 60°3 
82:4 83°6 818 66°9 
84:8 86:2 84-1 70:0 
92-6 93°8 92-4 81:8 
98-4 99°5 98-4 92°6 
Lastly, five hygrometers of M. Bunten, differing from the 
preceding, but constructed with the same kind of hairs, were 
placed simultaneously in the same glass vessel, into which were 
successively poured mixtures of sulphuric acid and water in va- 
riable proportions. The numbers given in Table III. were 
obtained. 
Taste III. 
Hygrometers of Bunten. 
He 8. 9. 10. LIL 
211 19:9 18°7 21°3 20°7 
41°] 41°3 3974 42-2 41°] 
58:4 58:3 56-2 59-5 58°6 
66:3 67°3 65:1 68:7 67:9 
79'3 80:7 735 82-2 $14 
89-1 90°9 88-6 91:5 91-1 
94:2 95°8 94:2 - 96:0 95-6 
It is seen by these tables that the hygrometers of M. Bunten 
kept pace in a satisfactory manner in all the observations; the 
greatest difference in fact amounts to only 3°. It will be also 
observed, that when one of the hygrometers indicates a higher 
degree than another, a difference in the same direction is main- 
tained in all the other observations. 
I conclude from this, that hygrometers constructed with hairs 
