1880.] On Actinometrical Observations, made in India. 161 



13. Table VIII. — Table V supplies the materials also for this table, 

 which presents the mean facts of the hourly or long series, taken on 

 the 12th and 14th November, simultaneously, at both the stations of 

 observation. Each series furnishes nine mean results, of which the 

 middle value is at noon. By comparing the radiation at noon with 

 the hourly results for each day, we obtain the defect of radiation from 

 noon corresponding to the change in the sun's zenith distance. 



14. Now, collecting the results from Table VI for Mussooree, we 

 find the mean sub-time- range values to be — 











No. of 



Mean 



h. 



m. 



h. 



m. 



results. 



group. 



11 



30 to 



11 



40 



42 ... 



. 957 



11 



40 „ 



11 



48 



40 



. 958 



11 



48 „ 







, 



55 ... 



. 957 mean 957. 







„ 







12 



61 .. 



.. 953 







12 „ 







20 .... 



. 40 .. 



. . 952 







20 „ 







30 



.. 38 .. 



. . 949 mean 951 



from which it appears : — 



(1.) The radiation is sensibly constant for each half -hour. 



(2.) The radiation, during the half- hour before noon, exceeds that 

 prevailing during the half-hour after noon ; in the present instance, 

 the excess is only six-tenths of a millimetre, but notwithstanding the 

 smallness of this quantity, it appears to be real, not accidental. 



(3.) Apart from constants, it may be inferred from the accordance 

 of the results that the instrument is susceptible of a high degree of 

 accuracy. 



Again, the above conclusion (2) is very decidedly confirmed by the 

 results for Mussooree, from Table VIII, where the sums of the defects 

 of radiation from the noon value furnish large test-measures of the 

 point in question, and are as follows : — 



Nov. 12. Nov. 14. 



Sums for the four hours before noon 287 .... 332 



,, ,, after noon 386 . . . , 392 



5? 



After noon — Before noon 99 .... 60 



Mean (indicating excess of radiation before noon) .... 79 



15. The Delira results in Table VI are not sufficiently numerous or 

 symmetrical to test the conclusions (1) to (3) of Article 14 ; in fact, 

 they present but three complete series of groups ; nor may incomplete 

 series be admitted in this test, because of the undeniable presence of 

 variable daily constants. And with regard to Dehra evidence, in 



