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. 
January 
February 
March 
April 
May 
June 
July 
August 
September 
October 
November 
December 
Spring 
Summer 
Autumn 
Winter 
The Year 
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" in the second week, a correction was applied to the 
mean for that hour of — 3°11, obtained from Table VII. as follows :— 
{Mean temp. Jan. 9—31 = 37°99 minus mean temp. Jan. 16—31 = 41°-10}= —3"11. 
The means were afterward corrected by —1°-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, 1" 35™, occurring later than max. temp. of air by 5™. 
Summer, 14 QO™, wes eee eee CALTLET coc ccc cce snc senvecveeseeoee QF. 
Autumn, 12 10m, ee cee eee see cee eee eee eee aee cee eee eee ceeeee 95m, 
Winter, LP 10, cee eeeseneeeseecee cee eee cee eee eee nee eee ee 0, 
The Year, 12 15™,  ccsccccceceeeee cee eeeceecteseeseeereeeeeeeres 15m, 
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 18™ a.m. 
JOBS KoaDSddShonse ea peUdOGRBBEmNDag aMderbaahoAsBoEbaseBedkbobspooctic 72 19™ p.m. 
The interval between the two periods is TTR 
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. AND MET. oss. 1843. 3yY 
