138 
MR. GLAISHER ON THE CORRECTIONS TO BE 
Therefore, there is a rapid increase of vapour and decrease of the degree of 
humidity during the day, and a rapid diminution of vapour and increase of the 
degree of humidity during the evening and night hours. These remarks are to be 
understood to apply to a point at the height of four feet only from the earth. 
At present I cannot give any information relative to the distribution of vapour at 
distances greater than four feet. However, from the fact, that whilst evaporation is 
the most rapid, the air at the height of four feet becomes relatively drier than it 
would be in consequence of the increase of temperature alone, it is plain that much 
vapour must pass upwards. 
In the higher strata of the atmosphere the changes of temperature are less than in 
the lower strata ; and at a point not very distant from the earth, but varying in dif- 
ferent seasons, the temperature must be stationary during the twenty-four hours of 
the day ; we may readily infer that at a certain point above the earth, the air be- 
comes relatively more moist during the course of the day whilst the ascending 
current continues, and less so at night whilst the vapour flows downwards with the 
descending current ; being exactly the reverse of the facts which take place at the 
height of four feet. At some certain point above the earth, the temperature of the 
dew-point, like that of the air, must be stationary during the twenty-four hours of 
the day. Observations to determine the absolute quantity of water mixed with the 
air, and the relative humidity at different distances from the earth, are much needed. 
Table XII. — Showing the corrections to be applied to the weight of a cubic foot of 
air, under the average temperature, humidity and pressure, at any hour, to deduce 
the true weight for the month from the observations taken at that hour. 
Local mean 
time. 
January. 
Feb. 
March. 
April. 
May. 
June. 
July. 
August. 
Sept. 
Oct. 
Nov. 
Dec. 
gr. 
gr- 
gr- 
gr. 
gr- 
gr. 
gr- 
gr- 
gr- 
gr. 
gr- 
gi-. 
Midnight. 
-0-5 
-1-7 
-2-7 
— 5-3 
-5-3 
— 
6-1 
— 3-1 
— 3-1 
— 4-2 
-2-9 
-1-8 
-1-0 
1 A.M. 
— M 
-2-0 
-3-0 
-6-0 
-3-9 
— 
7-7 
— 3-8 
—6-2 
-3-2 
— 3-1 
-1*7 
-1-4 
2 
-1*6 
— 2-0 
-3-2 
-6-6 
-6-5 
— 
9-0 
-6-4 
—6-3 
— 3-6 
— 3-3 
-1-8 
-1-3 
3 
— 1-8 
— 2-2 
— 3-5 
-7-1 
-7*1 
10-0 
-6-8 
-6-8 
-6-0 
— 3-8 
-1*8 
-1-7 
4 
— 2*0 
-2-3 
-3-7 
-7-6 
-7-1 
— 
10-1 
-7-0 
-7-0 
—6-2 
-4-0 
— 2-0 
-1-6 
5 
— 2-0 
-2-5 
-3-7 
-7-7 
-6-9 
— 
8-9 
-6-7 
-6-9 
-6-0 
-4-0 
-1-9 
-1-6 
6 
— 2-0 
-2-5 
-3-7 
— 6*5 
-5-5 
— 
6*5 
-3-0 
-3-9 
-4-9 
-3-8 
—2-0 
-1-6 
7 
-1*9 
— 2-5 
— 3-4 
— 4-5 
-30 
— 
3-5 
-2-7 
-3-9 
-3-0 
-3-4 
-2-0 
-1-6 
8 
-1*7 
—2-0 
-2-5 
— 2-3 
-0-7 
— 
0-0 
-0-3 
— 1-0 
-0-3 
-2-3 
-1-6 
-1-3 
9 
— M 
-0-9 
— 0-4 
+ 0-3 
+ 1*7 
+ 
2-4 
+ 1-9 
4-1-3 
+ 2-4 
-10 
-0-7 
-0-9 
10 
— 0-2 
+ 0-4 
+ 1-7 
+ 2'6 
+ 3-8 
+ 
4-5 
-f 4-0 
-f3-7 
+ 4-7 
+ 1-3 
+ 0-6 
+ 0-1 
11 
+ 1-3 
+ 1-8 
+ 3-6 
4- 5-4 
+ 5-7 
+ 
6-2 
+ 3-8 
-f5-9 
+ 6-4 
+ 4-0 
+ 2-0 
+ 1-3 
Noon. 
+ 2-4 
+ 3-3 
+ 5-2 
+ 7-8 
4-7-2 
4- 
7-7 
+ 7-3 
-f7-3 
+ 7-3 
+ 3-8 
+ 3-3 
+ 2-6 
1 P.M. 
+ 3-1 
+ 4-4 
+ 6-1 
+ 9-3 
+ 7-9 
+ 
8-7 
4-8-3 
■f8-l 
+ 8-0 
+ 6-6 
+ 4-3 
+ 3-1 
2 
+ 3-3 
+ 5*2 
+ 6-1 
+ 9-2 
+ 8-3 
+ 
8-8 
+ 8-4 
-1-8-3 
+ 7-8 
+ 6-6 
+ 4-3 
+ 3-1 
3 
+ 3-0 
+ 5-0 
+ 5-5 
+ 8-7 
+ 8-2 
+ 
8-8 
+ 8-3 
-f 8-0 
+ 6-9 
+ 6-1 
+ 3-8 
+ 2-7 
4 
+ 2-4 
+ 3-8 
+ 4-5 
+ 7-5 
+ 7-3 
+ 
8-2 
+ 7-4 
4-6-8 
+ 3-3 
+ 4-9 
+ 2-7 
+ 1-7 
5 
+ 1-6 
+ 2-5 
+ 3-2 
+ 5-8 
+ 5-5 
4- 
6-8 
+ 3-7 
+ 3-1 
+ 3-8 
+ 3-3 
+ 1-3 
+ 1-1 
6 
+ 0-8 
+ 1-2 
+ 1*7 
j +4-0 
+ .3-5 
+ 
4-5 
+ 3-0 
+ 3-0 
+ 1-8 
+ 1-7 
+ 0-6 
+ 0-6 
7 
+ 0-4 
+ 0-4 
0-0 
+ 1'8 
+ 1-1 
+ 
1-5 
+ 1-8 
+ 1-0 
— 0-2 
+ 0-4 
— 0-3 
+ 0-2 
8 
+ 0-1 
-0-4 
— M 
; -0-5 
- 1-0 
— 
0-5 
0-0 
-1-0 
— 1-3 
-0-7 
-1-0 
-0-2 
9 
0-0 
-1-2 
-1-7 
j -2-3 
-2-7 
— 
2-3 
— 1-8 
— 2-8 
-2-4 
— 1-3 
-1-4 
-0-3 
10 
— 0-1 
— 1-5 
— 2-4 
! -3-6 
— 4-3 
— 
4-0 
-3-3 
— 4-0 
— 3-3 
— 2-0 
-1-6 
-0-7 
11 
— 0-4 
-1-9 
— 2-8 
j -4-7 
— 5-2 
— 
3-0 
— 4-4 
— 3-0 
— 4-1 
-2-7 
-1-8 
-0-9 
The sign + denotes that the number is to be added, and the sign — denotes that the number is to be subtracted. 
