10 



[.'KEEK. 



ACTINIC AND NONACTINIC DAYS. 



The differences between various days apparently similar in every 

 respect as regards insolation is very remarkable, and what is still more 

 striking, hazy days seem often to bring about greater decomposition of the 

 oxalic acid than those which are perfectly clear; conditions which had 

 previously been noted by other authors referred to in this paper. 



A table will make this more evident. 



■ Table I. — Decomposition of oxalic acid in the presence of uranium acetaie. 



No. 



1910. 



Decom- 

 position, 

 grams of 



oxalic 

 acid. 



Day. 



1 



Jan. 17 



0.084 



Bright sun. 



2 



Jan. 18 



0.083 



Hazy. 



3 



Jan. 19 



0.049 



Partly cloudy. 



4 



Feb. 4 



0.080 



Partly cloudy, but on the whole fair: 



5 



Feb. 5 



0.050 



Bright sunlight. 



6 



Feb. 7 



0.035 



Sun intermittent but still partly bright. 



7 



Feb. 8 



0. 045 



Hazy and cloudy. 



8 



Feb. 9 



0.075 



Hazy and cloudy. 



9 



Feb. 14 



1.000 



Bright sunlight. 



10 



Feb. 16 



0.085 



Partly cloudy. 



11 



Feb. 17 



1.120 



Bright sunlight. 



12 



Feb. 18 



0.041 



Cloudy. 



13 



Feb. 21 



0.047 



Cloudy. 



14 



Feb. 22 



0.073 



Bright sunlight. 



15 



Feb. 23 



1.500 



Bright sunlight. 



It is feasible, therefore, to divide even the days of bright sunshine into 

 those which are "actinic" and others which are "nonactinic." Thus, 

 numbers 9, 11, and 15 are distinctly actinic, whereas number 5 and 14 are 

 nonactinic; undoubtedly the effect of insolation in the Tropics during 

 the former would be much greater than during the latter; indeed, some 

 of the nonactinic days are very nearly like those of temperate climates. 



THE EFFECT OF TROPICAL SUNLIGHT ON THE ATMOSPHERE. 



Another phenomenon to be observed in Manila in a marked degree, and 

 which, so far as I am aware, has not been recorded in the literature from 

 other climates, is the extensive ionization of the air when exposed to the 

 sunlight. Doctor Bacon, using a modern electroscope, has been able to 

 show that our atmosphere, when exposed to the direct rays of the sun, 

 rapidly discharges the instrument, the loss of potential being 46 volts 

 per hour, whereas, in the diffused light of a room it is only 15, and during 

 the night 6, for the same volume of air. This is certainly a remarkable 

 result, which deserves further study. The only comparative data on hand 



