ON SOLAR RADIATION. 



153 



These data and the results thus derived from them are 

 shown in the following Table : — 





Mean 



temperature 



of air. 



Mean 

 temperature 



of 

 dew-point. 



Difference. 



Mean 

 amount of 



solar 

 radiation. 



Ratio. 



1862 



1863 



1864 



1865 



1866 





 47*3 

 48-3 

 47 'o 

 48-6 



48-3 







42"3 

 42"3 

 40-5 

 43*3 



42-3 







5-0 

 6'o 

 6-5 



5-3 

 6-0 



10-90 



11-47 



ri'5o 



972 



8-25 



2-1 8 

 1-91 



177 

 1-83 

 1*37 



The mean ratio for the two years 1865-66 is i'60j while 

 that for the years 1862-64 amounts to i'95. It appears, 

 therefore, that the calorific intensity of the sun^s rays 

 continued to diminish for two years after the termination 

 of the Oxford series ; and as the observations of Schwabe, 

 Wolf, Balfour Stewart, and others have shown that the 

 frequency of solar spots also diminished during these two 

 years, the probability that a close connexion exists be- 

 tween the two phenomena is considerably increased by 

 the results of Mr. Mackereth^s short but valuable series of 

 observations. 



On comparing the Oxford and the Eccles series of re- 

 sults it will be seen that the values for the years which 

 are common to both (1862-64) are greater at Eccles than 

 at Oxford in the ratio of 1*17 to i*oo, thus indicating 

 that the blackened bulb of the thermometer at Eccles 

 absorbs radiant heat more readily than that at Oxford. 

 Dividing the Eccles mean annual values by 1*17 in order 

 to reduce them to the Oxford scale, and calculating the 

 ratios, we have, — 





Reduced values 

 of solar radiation. 



Ratios 



1862 



9-33 

 9-82 

 9-84 

 8-32 

 7"o6 



1-82 

 1-63 

 1-51 



i'57 

 117 



1863 



1864 



i86< 



1866 





