290 Professor Apsoun on the Theory 
In the experiments which I performed on this plan the air was saturated with 
moisture, by forcing it from a bellows through a succession of four Wolfe’s bottles, con- 
nected in the usual way so as to cause the air to pass in each bottle through about two 
inches of water, and the air thus saturated was heated by being made to pass through 
a coil of copper tubing, immersed in a tub of warm water, the thermometer and 
hygrometer being placed with their bulbs within a quarter of an inch of each other 
in a narrow glass tube, attached to the farther extremity of the copper worm. The 
following are the results thus obtained :-— 
t’ ob. | t’ cale. Diff. 
t t d 
7s | 62.2 | 15.8 | 3030 | 51.3 | 50.47 | —. 83 
WWenmaes 76 | 61.5 | 14.5 | 30.30 | 51.3 | 50.26 | —1.04 
Agel | 73 | 60.3 | 12.7 | 30.30 | 51.3 | 51.58 | + .28 
Meat 12 60 | 12 | 30.30 | 52.3 | 50.81 | — .49 | 
69 | 58.6 | 10.4 | 30.30 | 51.3 | 50.40 | — .90 
f 90.5 | 67 23.5 Be 50.8 | 50.17 | — .63 
, 82.2 | 64.3 | 17.9 | 30.15 | 50.9 | 51 S50 
eee | 79 | 62 | 16.4 | 30.15 | 50.9 | 50.23 | — .67 
| 24M.) 71.7 | 60 | 11.7 | 30.15 | 51.2 | 50.66 | — .54 
69 | 58.9 | 10.1 | 30.15 | 51.5 | 50.70 | — .80 | 
(92 | 69 | 23 3942 | 541 | 54.40 | + .30 | 
| April 20, 1835, | 83 | 65.8 | 17.2 | 30.42 | 54.5 | 54.36 | — .14 
11 o'clock, A.M. | 76 | 63.3 | 12.7 | 30.42 | 54.9 | 54.54 | — .36 
| 6s | 60.3 | 7.7 | 30.42 | 55 | 54.74 | — .26 
98.5 | 71.5 | 27 | 30.36 | 55.5 | 55.51 | + .O1 
April 21, 1835, } 84.6 | 67 | 17.6 | 30.36 | 56 | 55.79 | — .21 | 
11 o'clock, A.M. ] 77.5 | 64.5 | 13 | 30.36 | 56.3 | 55.97 | — .33 | 
s1_ | 62.2| 8.8 | 30.36 | 56.5 | 56.18 | — 32 | 
83 | 66.5 | 16.5 | 30.51 | 56.8 | 55.87 | — .93 | 
pert ia Hone a | 77 |65 | 12 | 30.51 | 57.2 | 57.23 | + .03 | 
epte cata atl 70 Sa 6S 8.3 a B50) o74dt 0s | 
Hee 91.8 | 68.6 | 23.2 | 30.51 | 54.1 | 53.70 | — .40 | 
| Rte ee | 75.2 | 63.2! 12 | 30.51 | 55 | 54.94 | — .06 | 
7AM. | 72 | 62 | 10 | 30.51 | 55.1 | 54.98 | — .12 | 
| | — -35=mean.| 
By a glance at the preceding table, which includes twenty-four distinct observations, 
we will perceive, Ist. that in the case of seven of them, the observed and calculated 
dew-points are almost coincident ; 2d. that the difference in no instance exceeds, 
and in but a single instance reaches, one degree; and 3d. that the mean difference, 
deducible from the whole, is but .35, or about one-third of a degree Fahrenheit. It 
will also be noted that the difference is negative, or that the mean calculated dew- 
point is lower than the observed, and not vice versa. If we were justified in consi- 
dering this latter result as any thing more than accidental, it might certainly be 
urged as an argument against the strict accuracy either of our experiments, or our 
theoretical views ; for the corrections for the influence of pressure and aqueous 
vapour on the specific heat of air being neglected in the preceding calculations, the 
