TEMPERATURE OF THE AIR. 267 
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 February 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 =18°7. 
TABLE VI.—Extremes of Temperature for each Month from the Register Thermometers ; Extremes 
of Daily Mean Temperature for each Month, deduced from the Daily Observations; and Extreme 
Diurnal Ranges for each Month from the Register Thermometers. 
Extreme Temperatures. Extremes of Mean Daily Temperature. Extreme Diurnal Ranges. 
Month. 
Highest. Lowest. Range.| Mean. Highest. Lowest. Range. | Mean. Greatest. Least. 
d. e d. a e 2 d. 2 d. fa 2 8 da. 2 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 3-7 
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 {oat 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 | 245 | 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) 228) 5 2-0 
Extremes of Temperature, 1843. 
Highest temperature occurred -----+--+-.---- August 18, =i — #0, ick 
Lowest «+ -1- eee see eee cee see see cee eeeseeeeeeee February 18, = 6°9 Te 71°-8, mean = 42°8, 
Highest daily mean temperature occurred August 19 = 65°2 au Ae 
GG ESE asic cle axis natal walsis's's ewslensjsbs\eiesleveince February 18, = 18°6 range = 46° 6, mean = 41 
Highest weekly mean ee ada occurred August 14—19, = 61°5 mie ae 
MGW EAE ve cceetea a Spree eps Cas (peas ae) i alieeaeiaaiina ioe tet 
Highest monthly m mean mn temper: ature ae August, = 57°:3 i Wayor Le aie 
Wowest  -+-.-..- ceo cc Tae bed cee seo Segees February, = 33°:0 yee 2s "Sy mean — fai 
In each case, the interval between the highest and lowest is exactly six months. 
The greatest diurnal range of temperature occurred ...............++- September 8, = 36°5 
The lowest ........< PEE te Neen cicic aa ntdseedas sane ehareee aeenesee February 2, = 11 
The greatest range of temperature for a month occurred ............ February 18—March 18, = 54°-6 
The greatest range of daily mean temperature for a month occurred February 18—March 18, = 28°2 
* In this volume, | 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. Hyen 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. 
