20 Fowler, Chemical Action of Tropical Sunlight. 



Red lead, Pb304 and yellow oxide of mercury, HgO 

 were exposed to light in sealed tubes, but no well-defined 

 change took place. 



A selection of different coloured silk ribbons, such as 

 are ordinarily sold in Calcutta, was exposed to light for 

 varying periods. It was found that light green ribbon 

 rapidly faded, the effect being appreciable after a few 

 hours bright sunshine, light blue was also very sensitive, 

 orange yellow darkened somewhat on exposure, while red 

 altered only very slowly. 



Summing up the results of the scattered observations 

 in this paper, it may be said that the photo-chemical 

 effects of tropical sunlight do not differ in kind from 

 those observed under European conditions, and that even 

 in certain favoured European localities equally striking 

 effects may be obtained. 



The method of observation introduced by Dr. Angus 

 Smith and employed as suggested by Dr. Bailey, 

 has proved simple to carry out and trustworthy in its 

 results, and it may be hoped that other observers will 

 take up the subject as opportunity offers, and thus 

 extend our quantitative knowledge of photo-chemical 

 activity in various parts of the world. 



