Temper ature of the Air. 
2G7 
Diurnal Range of Temperature. — The diurnal ranges deduced from the means, Table III., are imperfect, 
as the hours of the minima are not included in the Summer months. Making every allowance for this defi- 
ciency, there is little difficulty in perceiving that the ranges are greater, on the whole, for the months near the 
Equinoxes than for the Summer months. This fact will-be seen more distinctly in the means at the foot of 
Table V. From this Table, we find that the smallest mean of the diurnal ranges occurs in Februai-y and 
December, the mean of the ranges increases till April, diminishes in May and June, and again increases till 
August and September, when it is a maximum.* 
From Table III., the range of the mean diurnal curve for the year must be about 9°. 
From Table V., the mean of all the diurnal ranges for the year =13°- 7. 
TABLE VI. — Extremes of Temperature for each Month from the Register Thei'mometers ; Extremes 
of Daily Mean Temperature for each Month, deduced from the Daily Observations ; and Extreme 
Diurnal Ranges for each Month from the Register Thei'mometers. 
Month. 
Extreme Temperatures. 
Extremes of Mean Daily Temperature. 
Extreme Diurnal Ranges. 
Highest. 
Lowest. 
Range. 
Mean. 
Hi 
ghest. 
Lowest. 
Range. 
Mean. 
Greatest. 
Least. 
d. 
d. 
0 
d. 
d. 
d. 
d. 
January 
27 
55-1 
15 
19-9 
35-2 
37-5 
27 
51-1 
3 
30-1 
21-0 
41-0 
3 
24-1 
30 
1 
2 
February 
1 
44-8 
18 
6-9 
37-9 
25-8 
1 
40-6 
18 
18-6 
22-0 
29-6 
18 
29-5 
2 
1 
1 
March 
18 
61-5 
4 
20-2 
41-3 
40-8 
22 
49-9 
4 
30-1 
19-8 
40-0 
30 
27-6 
27 
3 
/ 
April 
19 
64-4 
12 
23-8 
40-6 
44-1 
19 
53-3 
11 
33-6 
19-7 
43-4 
24 
25-9 
22 
6 
5 
May 
14 
62-8 
19 
30-4 
32-4 
46-6 
13 
52-5 
29 
42-6 
9-9 
47-5 
1 
28-5 
16 
1 
8 
June 
23 
72-7 
6 
41-3 
31-4 
57-0 
21 
57-7 
5 
42-7 
15-0 
50-2 
23 
27-4 
5 
1 
2 
July 
14 
69-5 
25 
36-4 
33-1 
52-9 
26 
61-5 
20 
51-7 
9-8 
56-6 
25 
31-2 
3 
9 
6 
August 
18 
78-7 
24 
36-5 
42-2 
57-6 
19 
65-2 
30 
51-8 
13-4 
58-5 
24 
33-4 
22 
9 
9 
September 
8 
77-0 
29 
30-6 
46-4 
53-8 
2 
64-4 
{2} 
44-1 
20-3 
54-2 
8 
36-5 
25 
6 
0 
October 
1 
65-4 
19 
21-6 
43-8 
43-5 
6 
57-2 
16 
32-7 
24-5 
44-9 
16 
24-9 
29 
4 
5 
November 
4 
54-5 
26 
26-5 
28-0 
40-5 
27 
48-9 
25 
30-8 
18-1 
39-8 
26 
26-1 
29 
3 
4 
December 
24 
54-6 
2 
25-3 
29-3 
39-9 
23 
49-8 
1 
31-8 
18-0 
40-8 
2 
22-8 
5 
2 
0 
Extremes of Temperature, 1843. 
= 7° -7 
Highest temperature occurred • August 18, 
Lowest February 18, 
Highest daily mean temperature occurred August 19, 
Lowest February 18, 
Highest weekly mean temperature occurred August 14 — 19, 
Lowest Februaiw 13 — 18, 
Highest monthly mean temperature occurred August, 
Lowest February, 
^ | range = 71 0, 8, mean 
'21 
q > range = 46 *6, mean 
^4 0, 9 } ran S e = 36°-6, mean 
65°2 
18 
57 c 
33° 
■3 1 
o.q > range = 24°-3, mean 
In each case, the interval between the highest and lowest is exactly six months. 
The greatest diurnal range of temperature occurred September 8, = 
The lowest February 2, = 
The greatest range of temperature for a month occurred February 18 — March 18, = 
The greatest range of daily mean temperature for a month occurred February 18 — March 18, = 
42 c -8. 
41°-9. 
43°-2. 
45°-l. 
86°- 5 
1°1 
54°-6 
28°-2 
* In this volume, I have followed the practice of meteorologists, and have grouped the months into the meteorological seasons. 
As far as the results for the year 1843 go, the value of this mode of grouping seems very questionable. With the single exception 
of the mean temperature, the facts (diurnal range, critical intervals, and periods of maxima) are more directly related to the astro- 
nomical seasons. Even for the mean temperature each year would require a particular mode of grouping ; it is only on the average 
of a number of years that June, July, and August are entitled to be called Summer. In 1843, it will be seen that July, August, and 
September are the three months with the highest mean temperature. 
The cause of the diminished diurnal range in the midsummer months is obviously due to the sun's approach to perpetual appari- 
tion, as has been pointed out elsewhere. — See Professor Forbes's Supplementary Report on Meteorology, Report Brit. Assoc. 1840. 
page 52. 
