A PRELIMINARY STUDY OF THE EFFECT OF TROPICAL 



SUNLIGHT ON THE ATMOSPHERE, WITH SOME 



NOTES ON RADIOACTIVE PHENOMENA 



IN THE PHILIPPINES. 1 



By Raymond F. Bacon. 

 (From the Chemical Laboratory, Bureau of Science, Manila, P. I. 



Early in 1906 I stated 2 that the tropical sunlight seemed to ionize 

 the air so that it would discharge an electroscope at a more rapid rate 

 than noninsolated air. Recently, in connection with the general study of 

 the effects of tropical sunlight undertaken in this Bureau, I have again 

 taken up this question and confirmed my earlier results. 



The apparatus used was a Fontaktoscope according to C. Engler and H. 

 Sieveking, the instrument being accompanied by a table of voltages corresponding 

 to the various positions of the aluminium leaves. With the diffusion cylinder 

 hanging in the 10-liter can and attached to the rod carrying the aluminium 

 leaves, the normal rate of fall of the electroscope corresponded to a loss of 

 potential of 4.3 volts per hour, and, under the conditions given, this was fairly 

 constant for a large number of measurements extending over about four months, 

 the extreme values being 4 and 5.5 volts per hour. 



To measure the effect of light on the ionization of the air, the latter was 

 drawn at a definite rate through the can in which the diffusion cylinder was 

 suspended, the amount of air being measured by a gas meter. 



Comparative measurements of the rate of fall of the aluminium leaves 

 were then made at night in the laboratory, in the daytime in the diffuse 

 light of the laboratory and in the sunlight. When the apparatus was 

 placed in the sunlight, the electroscope proper was always covered, 

 although this seemed to make practically no difference. Even if the 

 apparatus were uncovered, no direct sunlight could penetrate to the 



1 Owing to the fact that Doctor Bacon has left the Philippines, the data so far 

 obtained by him are now published, although the work as yet is very incomplete 

 and is being continued by the Bureau of Science. (P. C. F.) 



2 This Journal (1906), 1, 433. 



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