288 Professor Apsoun on the Theory 
t t Pp d ob. d cale. Diff. 
March 11 | 48.5 | 31.5 | 29.37 | 17 17.4 — A 
15 | 50.5 | 33.5 | 30.00 | 17 18.2 —1.2 
20 | 54.5 | 35.5 | 30.25 | 19 19.4 — .4 
21 | 57.5 | 37.5 | 30.27 | 20 20.8 — 8 
22 | 54.5 | 36 30.35 | 18.5 19.7 —1.2 
Now, as in all these instances, the observed depression differs from ‘the true ; this 
difference, though small, being always on the same side, must be ascribed either to the 
co-efficient m being assumed too great, or to the method of experiment employed not 
being calculated to afford the extreme depression. That this latter was the real 
cause of the discrepancy I was disposed to believe, from having observed that 
when the hygrometer, in the course of an experiment, became stationary, it could be 
made to sink a little further by pressing with great force upon the bag of air. In 
fact, this observation rendered it probable that the tube, between the lower and middle 
bottle of the Nooth, did not afford sufficient air-way; and that, therefore, there was 
not a sufficient current from behind to propel forward, and immediately remove, from 
contact with the moistened bulb, the air which had become saturated with its humi- 
dity. To bring this conjecture to the criterion of experiment, it was obviously 
necessary to operate so, that while the air underwent perfect desiccation, it was, at 
the same time, made to pass over the thermometers in a strong and continuous 
current ; and, after some trials, I found that both objects were secured by substi- 
tuting for the Nooth a series of three Wolfe’s bottles, containing oil of vitriol, and 
connected, as in the process for preparing the water of ammonia, by glass tubes and 
caoutchouc collars, the bag of air being attached to a tube passing to the bottom of 
the first bottle, and the thermometers being placed in the axis of a tube perforating 
a cork inserted into one of the tubulures of the last bottle. ‘The experiments re- 
corded in the following table were made with this apparatus. 
t t P d ob. d cale. | Diff. 
March 26 | 51 33.5 | 30.55 | 17.5 | 17.94 | +.44 
27 | 53 34.5 | 80.385 | 18.5 | 17.73 | —.77 
28 | 52 34 80.21 | 18 17.62 | —.38 
29 | 51 33 30.05 | 18 17.97 | —.03 
30 | 52 33.4 | 29.75 | 18.6 | 18.387 | —.23 
31 | 53 84.3 | 29.50 | 18.7 | 19.14 | +.44 
April 1 | 56.5| 35.8 | 29.70 | 20.7 | 20.04 | —.66 
2 | 58 387 29.72 | 21 20.88 | —.12 
° 3 | 58.2| 37 29.77 | 21.2 | 20.84 | —.36 
4 | 58 37 30.03 | 21 20.68 | —.32 
5 | 58 37 30.15 | 21 20.59 | —.41 
6 | 59 37.5 | 30.25 | 21.5 | 20.88 | —.62 
7 | 59 38 30.26 | 21 21.24 | +.24 
8 | 61 38.7 | 30.21 | 22.3 | 21.80 | —.60 
10 | 58.3| 387.7 | 30.85 | 20.6 | 20.96 | ++.36| 
1l | 58 37.5 | 30.45 | 20.5 | 20.75 | +.35 
12 | 56.3] 36.5 | 30.30 | 19.8 | 20.12 | +.32| 
USF S725) enor 30.20 | 20.5 | 20.55 | +.05 
14 | 57.5 | 87 30.15 | 20.5 | 20.59 | +.09 
