1885.] 



S. A. mil —Ohservatluns af lite Sular Thermometer. 



35 











Hours 



of observation, Mean Time. 







Date. 

























8 



9 



10 



11 



12 



13 



14 



15 



IG 



Jnno 



., 7th 



1-69 



1-31 



112 



1-03 



1-00 



103 



113 



1-32 



]'70 





14th 



1-70 



1-32 



112 



103 



1-00 



103 



112 



1-31 



1-69 





21st 



1-71 



1-33 



113 



103 



I'OO 



103 



112 



1-31 



1-63 





28th 



1-72 



1-33 



113 



1-03 



1-00 



1-03 



112 



130 



1-66 



September.... 



.. 7th 



2-02 



1-47 



1-22 



111 



1-06 



111 



1-23 



1-50 



2-06 





14th 



2-06 



1-50 



1-24 



113 



1-08 



113 



1-27 



1-56 



2-20 





21st 



211 



1-55 



1-27 



115 



rio 



116 



1-31 



1-63 



2-34 





28th 



217 



1-56 



1-29 



117 



113 



1-20 



136 



171 



2-53 



October ....... 



.. 7th 



2-32 



1-64 



1-36 



1-23 



119 



1-26 



1-45 



1-85 



2-86 





14th 



2-37 



1-68 



1-38 



1-25 



122 



1-30 



1-49 



1-92 



304. 





21st 



2-48 



1-63 



1-43 



1-29 



1-26 



1-34 



1-56 



2-02 



3-31 





28th 



2-60 



1-80 



1-47 



133 



1-30 



1-39 



1-62 



213 



3-60 



November .... 



.. 7th 



2-84 



1-92 



1-56 



1-40 



1-37 



1-47 



1-72 



230 



4-OS 





14th 



304 



2-01 



1-62 



1-4G 



1-42 



1-52 



1-79 



2-40 



4-33 





2l8t 



3-23 



2-04 



1-68 



1-50 



1-46 



1-56 



1-84 



2-48 



4-53 





28th 



3-45 



219 



173 



1-54 



1-50 



1-59 



1-88 



2-53 



4-69 



December .... 



.. 7th 



3-81 



2-32 



181 



1-59 



1-54 



1'63 



1-91 



2-57 



4-73 





14th 



4-06 



2-40 



185 



1-62 



1-56 



1-64 



1-92 



2-55 



4-64 





21st 



4-30 



2-47 



1-88 



1-63 



1-56 



1-64 



1-90 



2-50 



4-42 





28th 



4-45 



2-51 



1-89 



1-63 



1-56 



1'62 



1-87 



2-44 



419 



In making reductions of actinometric observations it soon becomes 

 evident that the atmospheric absorption varies not only from day to day, 

 but frequently from hour to hour. In nearly every month it seems to be 

 greater at Lucknow in the afternoons than in the forenoons, as might be 

 anticipated from the disturbances caused by diurnal heating, evaporation, 

 and the quantity of dust stirred up in dry weather by the diurnal winds. 

 Besides this general and regular increase from forenoon to afternoon, 

 there are numerous irregular changes from hour to hour, which render 

 it very difficult to estimate fairly the true absorbing power and the inci- 

 dent heat. For example, if the absorbing power happens to be greater 

 about noon than in the morning or evening, the curve representing the 

 variation of the observed heating effect will be flatter than it should be, 

 and the deduced value of the incident radiation will be too low ; whereas, 

 if the absorbing power be least about midday, the deduced solar constant 

 will be too high. 



To reduce errors of this kind to a minimum, I have, wherever the 

 series of observations for the several days of a month were complete or 

 nearly complete, taken the mean for each hour, and then deduced the 

 constants A and j^9 of the formula from these mean values. In other 



