Temperature of Evaporation. 
269 
TABLE VIII. — Hourly Means of the Temperature of Evaporation, as deduced from the Readings 
of the Wet Bulb Thermometer, at the Observation Hours for each month in 1843. 
Period. 
18 h . 
20 h . 
22 h . 
0 h . 
2 h . 
4 h . 
6 h . 
fth 
1 Ah 
Kange. 
January 
0 
36-30 
o 
3617 
o 
36-18 
o 
37-44 
o 
38-12 
o 
37-87 
o 
37-48 
o 
36-53 
o 
36-09 
0 
2-03 
February 
30-65 
30-65 
31-03 
32-78 
33-40 
33-20 
31-81 
30-92 
3110 
2-75 
• March 
33-76 
34-71 
37-40 
40-31 
41-31 
41-10 
39-48 
37-34 
36-46 
7-55 
April 
37-98 
40-72 
43-85 
44-83 
45-69 
45-20 
43-70 
41-80 
40-35 
7-71 
May 
41-14 
43-47 
45-51 
46-85 
47-11 
47-05 
46-09 
44-72 
43-07 
5.-97 
June 
46-41 
48-09 
49-40 
50-25 
51-17 
51-17 
50-90 
49-10 
47-05 
4-76 
July 
50-61 
53-66 
55-34 
56-20 
56-78 
55-86 
55-49 
53-79 
5212 
6-17 
August 
49-27 
52-71 
56-13 
58-47 
59-12 
58-80 
57-87 
55-90 
54 07 
9-85 
September 
46-82 
49-88 
53-87 
56-80 
57-93 
57-42 
56-41 
53-64 
51-50 
1111 
October 
37-99 
38-82 
41-33 
43-72 
43-83 
43-52 
41-23 
39-48 
38-80 
5-84 
November 
37-32 
37-80 
38-75 
40-24 
41-06 
39-95 
37-94 
37-55 
37-27 
3-79 
December 
42-81 
42-84 
43-70 
44-76 
45-03 
44-32 
43-27 
42-98 
42-88 
2-22 
Spring 
37-63 
39-63 
42-25 
44-00 
44-70 
44-45 
43-09 
41-29 
39-96 
7-07 
Summer 
48-76 
51-49 
53-62 
54-97 
55-69 
55-28 
54-75 
52-93 
51-08 
6-93 
Autumn 
40-71 
4217 
44-65 
46-92 
47-61 
46-96 
45-19 
43-56 
42-52 
6-90 
Winter 
36-59 
36-55 
36-97 
38-33 
38-85 
38-46 
37-52 
36-81 
36-69 
2-30 
The Year 
40-92 
42-46 
44-37 
46-05 
46-71 
46-29 
45-14 
43-64 
42-56 
5-79 
The observations in the first week of January were not made use of in obtaining the hourly means for 
that month. No observation having been made at 18 h in the second week, a correction was applied to the 
mean for that hour of — 3°T1, obtained from Table VII. as follows : — 
{Mean temp. Jan. 9—31 = 37°*99 minus mean temp. Jan. 16 — 31 = 41°-10} = - 3°-ll. 
The means were afterward corrected by — l o, 00, in order to render the mean for the month from these 
means equal to that obtained, Table VII., from all the daily observations. 
Diurnal Variation of the Temperature of Evaporation. — The maximum temperature of evaporation occurs 
rather later in the day than the maximum temperature of the air in Spring, and rather earlier in the day in 
Summer and Autumn. The hours of the maximum, Makerstoun mean time, for the four meteorological seasons, 
with their differences from the hours of the maximum temperature of the air (Table III.), are as follow : — 
Spring, l h 35 m , occurring later than max. temp, of air by 5 m . 
Summer, l h 20 m , earlier 25 m . 
Autumn, l h 10 m , • 25 m . 
Winter, l h 10 m , 0 m . 
The Year, l h 15 m , 15 m . 
The period of the minimum is not to be obtained from the nine daily observations. 
The mean temperature of evaporation for the year occurs at 8 h 18 m a.m. 
7 h 19 m P.M. 
The interval between the two periods is ll h l m . 
Range of the Diurnal Variation of the Temperature of Evaporation.- — The ranges in the previous Table 
are imperfect, on account of the minimum being awanting in the Summer months ; but it seems as evident here, 
as in the case of the temperature of the air, that the range is less in the Midsummer months than for the 
months immediately preceding and succeeding them. 
MAG. ANU MET. OBS. 1843. 3 Y 
