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 AprU, 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 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. 









""& — 











— t)- 























Month. 





Extreme 



Temperatures. 





Extremes of Mean Daily Temperature. 



Extreme Diurnal Ranges. 









































Highest. 



Lowest. 



Range. 



Mean. 



Highest. 



Lowest. 



Range. 



Mean. 



Greatest. 



Least. 







d. 







(3. 



o 



o 



, 



d. 







d. 



o 



= 



o 



d. 



o 



d. 



» 





January 



27 



55-1 



15 



19-9 



35-2 



37-5 



27 



5M 



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 



11 





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 



331 



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 



{S} 



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. 



Highest temperature occurred August 18, = 7°"71 17100 ^noo 



Loiest ...^. February 18; = ^..^^r^ng^ = 11 ■^, m.^n = ^2 -B. 



Highest daily mean temperature occurred August 19, = 65°"2 



Lowest February 18, = 18°-6 



Highest weekly mean temperature occurred August 14 — 19, = 61°- 5 



Lowest February 13—18, = 24°-9 



Highest monthly mean temperature occurred August, = 57°'3 



Lowest February, = 33° 



range = 46°'6, mean = 41°-9. 



range = 36°-6, mean = 43°-2. 

 jo.'o I range = 24°-3, mean = 45°-L 



In each case, the interval between the highest and lowest is exactly six months. 



The greatest diurnal range of temperature occurred September 8, = ^ 6"* 5 



The lowest February 2, = l°'l 



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, 1 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 moi'e 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 Foebes's Supplementary Report on Meteorology, Report Brit. Assoc. 1840, 

 page 52. 



