62 Observations on some Experiments in Electricity. 
with a dew-point in spring at 39.41°, we have an excess of .tempe- 
rature of 124°, whereas in autumn with a dew-point at 46.46°, we 
have a mean excess of only 8.54° ;—hence, both causes conspire 
in favor of spring and against the autumn. The mean quantit 
of moisture in the cubic inch of air in spritig, is .00174764 while 
that in autumn is .00220070, or about twenty-five per cent. more 
moisture, and one-third less excess of temperature in the latter than 
in the former. If we suppose experiments to be made in winter in 
an apartment artificially heated to 70° while its dew-point remains at 
23.25°, we shall have an excess of 46.25°, and as before, a quantity 
of moisture expressed by .00103359. If under these circumstances, 
the dryness could be maintained constant, electrical experiments 
might be performed with great satisfaction, but as lecture rooms are 
sometimes furnished with: pneumatic cisterns, and other sources of 
vapor, as well as occupied by numerous classes, the dew-point rises, 
more or less rapidly, far above that of the surrounding air without. 
‘The truth of this statement may have often been perceived by 
persons who wear spectacles, on which the moisture was: con- 
densed as they entered, from a cold atmosphere, an apartment at 
a high temperature, crowded with company, or furnished with other 
sources of moisture. It may also have.been observed that a machine 
will sometimes work well soon after a fire has been lighted, but will 
lose its power rapidly as the company before whom it was to be ex- 
hibited, come together, and further, that it will temporarily regain its 
activity by opening a door for a short time and edmitting a supply of 
dry though cold air. 
The substance of the foregoing remarks tal calculations may be 
presented in a tabular form, exhibiting moreover the ratios for the se- 
veral seasons between the moisture at the dew-points and the excess 
of temperature by which it is accompanied. The seasons are arrang- 
ed in the order of the ratios, beginning with the least favorable. 
e | g bsiel 7eoe,. | 323. 
ae a2 2 | 222) Estas | sake 
Seasons. es & 2 ae #33 5 BE 23 of 
a a {Mss| gess= | gees 
° ° ° grs. 
Summer, . .°. ~ -|72.17|61.10|11.07|.00350707) 315 
Autumn, . . . . -|55. |46.46| 8.54|.00220070| 388 
Winter,. .-. . - . {380.75 !23.75/| 7.00|.00103359! 677 
Spring,- - + «© + + 51.66 |39.41 |12.25 |.00174764| 701 
Artificial temperature of 2 |, aq loa we 
peep 70.00 .75 46.25 |.00103359! 4170 
