METEOROLOGY
527
Bon the value of n is found to be 53 nearly; and m is nearly®c|ual to 84. The mean temperature of the equator, therefore, is84°, and that of the pole 31°. To lirnl the mean temperature forevery other latitude, we have only to find 8s arithmetical meansbetween 84 and 31.” In this manner Mr. Kirwan calculated thefollowing
TABLE
Of the Mean Annual Temperature of the Standard Situationin everv Latitude.
Lat.
Temper.
Lat.
Temper.
Lat.
Temper.
90
31.
61
43.5
32
69.1
89
31.04
60
44.3
31
69.9
88
31.10
59
45.09
30
70.7
87
31.14
5S
45.8
29
71.5
86
31.2
57
46.7
28
72.3
85
31.4 1
56
47.5
27
72.8
84
31.5 !
55
48.4
26
73.8
83
31.7 j
54
49.2
25
74.5
82
32. 1
53
50.2
24
75.4 .
81
32.2
52
51.1
23
75.9
80
32.6
51
52.4
22
76.5
79
32.9
50
52.9
21
77.2
78
33.2
49
53.8
20
77.8
77
33.7
48
54.7
19
78.3
76
34.1
47
55.6
18
78.9
75
34.5
46
56.4
17
79.4
74
35.
45
57.5
16
79.9
73
35.5
44
58.4
15
80.4
72
36.
43
59.4
14
80.8
71
36.6
42
60.3
13
81.3
' 70
37.2
41
61.2
12
81.7
69
37.8 |
40
62.
11
82.
68
3S.4 1
39
63.
10
82.3
67
39.1
38
63.9
9
82.7 '
66
39.7
37
64.8
8
82.9
65
40.4
36
65.7
7
83.2
64
41.2
35
66.6
6
83.4
63
41.9 i
34
67.4
5
83.6
62
42.7
33
68.3
0
84.
This table, however, only answers for the temperature of theatmosphere of the ocean. It was calculated for that part of the•Atlantic Ocean which lies between the 80th degree of northernJU'd the 45th of southern latitude, and extends westward as far asfj'e Gulf-stream, and to within a few leagues of the coast of Atne-J lc a; and for all that part of the Pacific Ocean reaching from lati-tude 45° north to latitude 40° south, from the 20th to the 275thc * e gree of longitude east of Loudon. This part of the ocean Mr.
Kirwan calls the standard ; the rest of the ocean is subject to ano-malies which will be afterwards mentioned. Mr. Kirwan has alsocalculated the mean monthly temperature of the standard ocean,on the following principles, viz. The mean temperature of Aprilseems to approach very nearly to the mean annual temperature;and as far as heat depends on the action of the solar rays, themean heat of every month is as the mean altitude of the sun, orrather as the sine of the sun's altitude. The mean heat of April,therefore, and the sine of the sun’s altitude, being given, themean heat of May is found in this manner: As the sine of thesun’s mean altitude in April, is to the mean heat of April, so is thesine of the sun’s mean altitude in May, to the mean heat of May.In the same manner the mean heats of June, July, and August,are found ; but the rule would give the temperature of the suc-ceeding months too low, because it does not take in the heat de-rived from the earth, which possesses a degree of heat nearly equalto the mean annual temperature. The real temperature of thesemonths, therefore, must be looked upon as an arithmetical meanbetween the astronomical and terrestrial heats. Thus, in latitude51°, the astronomical heat of the month of September is 44.6°, andthe mean annual heat is 52.4°; therefore the real heat of this44.6 4-52.4
month should be — : — -— = 48.5. But however accurate
the principles, on which these calculations are made, may ap-pear, and how well soever they may answer the expectations ofthe philosopher in particular cases, or at particular seasons andcertain latitudes; yet when the calculations are made and sub-mitted to the test of general and continual observations; a wide dif-'; ference will be manifest in the results; audit is not to be ex-S pected that any theory will ever be framed which will atford prin-ciples sufficiently fixed and certain, to determine the mean tem-perature of the atmosphere, in every case to answer to observationsand actual experiment. The least attention to the subject willshew at once, that, since the temperature of the atmosphere de-pends on so many circumstances, a great number of which aremerely casual, not being directed by any known laws whatever,the calculations founded on a regular procedure cannot in anymeasure be adequate to the purposes intended. For not only thevarious kinds of surface and soil as being wet or dry, as consistingof clay or gravel, as being an open champagne country or contain-ing extensive forests, as having many elevations or depressions, &c.which may be considered in some measure as constant; but alsothe various directions of the wind, and the effects of electricityfrom exhalation, evaporation, formation of mists and clouds withthe descent of rain, &c. greatly affect the temperature. Fromthese and similar considerations it is evident, that the most we canexpect from any settled principles or determinate rules is a slightapproximation to the truth ; and therefore as any one might havewith certainty predicted, it happened that Mr. Kirwan, after goingthrough a tedious calculation, found the results by no means toagree with observations; hence he drew up the following table, partlyfrom these principles, and partly from a variety of sea-journals inhis possession:
TABLE of the Monthly Mean Temperature of the Standard from Lat. 80° to Lat. 9°.
Lat.
80°
79°
78°
77°
76°
O
74"
73°
72“
71°
1
i O
1 o
69°
68°
67“
66°
65°
64°
63°
■January. .
^*brua r y..
March.
22.
22.5
23.
23.5
24.
24.5
25.
25.5
26.
26.5
27.
27.5
27.5
28.
28.
28.
29.
30.
23.
23.
23.5
24.
24.5
25.
25.5
26.
26.5
27.
27.5
28.
28.
28.5
29.
30.
3 b
32.
27.
27.5
28.
28.5
29.
29.5
30.
30.5
31.
31.5
32.
32.5
33.
33.5
34.
35.
36.
37.
April...
32.6
32.9
33.2
33.7
34.1
34.5
35.
35.5
36.
36.6
37.2
37.8
3S.4
39.1
39.7
40.4
41.2
41.9
.
June.
Jllly
August...'.’. .'
~upternber.....October .
£°vember.
Ue cember.
36.5
36.5
37.
37.5
38.
38.5
39.
39.5
40.
40.5
41.
41.5
42.
42.5
43.
44.
45.
46.
51.
51.
51.5
52.
52.
52.
52.5
53.
53.5
54.
54.
54.5
54.5
54.5
55.
55. '
55.5
55.5
50.
50.
50.5
51.
51.
51.
51.5
52.
52.5
53.
53.5
53.5
53.5
54.
54.5
54.5
55.
55.
39.5
40.
41.
41.5
42.
42.5
43.
43.5
44.
44.5
45.
45.5
46.
47.
48.
48.5
49.
50.
33.5
34.
34.5
35.
35.5
36.
36.5
37.
38.
3S.5
39.
39.5
40.
41.
42.
43.
44.
45.
28.5
29-
29.5
30.
30.5
31.
31.5
32.
32.5
33.
33.5
34.
34.
55.
36.
37.
37.5
38.
23.
23.5
24.
24.5
25.
25.5
26.
26.5
27,
27.5
28.
28.5
29.
ol).
31.
32.
32.5
33.
22.5
23.
23.5
24.
24.5
25.
25.5
26.
26.5
27.
27.5
28.
28.
29.
30.
30.5
31.
31.