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. 



18h. 



20''. 



SSi. 



Oh. 



2'>. 



4''. 



eh. 



8h. 



10''. 



Range. 



January 



.36-30 



O 



36-17 



36-18 



37-44 



38-12 



37-87 



37-48 



36-53 



3609 



2-03 



February 



30-65 



30-65 



31-03 



32-78 



33-40 



33-20 



31-81 



30-92 



31-10 



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 



52-12 



6-17 



August 



49-27 



52-71 



56-13 



58-47 



59-12 



58-80 



57-87 



55-90 



5407 



9-85 



September 



46-82 



49-88 



53-87 



56-80 



57-93 



57-42 



56-41 



53-64 



51-50 



11-11 



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 



42-17 



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 



Tlie 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°-ll, 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 — 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 tiine, for the four meteorological seasons, 

 with their differences from the hours of the maximum temperature of the air (Table III.), are as follow : — 



Spring, I'* 35"^, occurring later than max. temp, of air by 5™. 



Summer, 1*^20°^, earlier 25°*. 



Autumn, 1^10% 25°'. 



Winter, I'' lO'", 0™. 



The Year, I*' 15° 



15™. 



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. 

 7^ IQ-^p.M. 



The interval between the two periods is 



ll*- 1' 



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. OBS. 1843. 



3 Y 



