STUDY OV THE EFFECT OF TROPICAL SUNLIGHT. 109 



in the shade when the sun is near the zenith and is almost com- 

 pletely shaded throughout the heat of the day. In many local- 

 ities this article with the exception of short trousers con.stitutes 

 the entire costume of the wearer, during work in the fields, in 

 others, a loin cloth is worn. Workers in the rice fields and 

 gardens most frequently use this attire. (Plates I and II.) 



The large-brimmed helmet which will cast a shadow over the 

 back, shoulders, and chest is the best substitute for the umbrella 

 or the hats of crude native workmanship and design. It should 

 be white in color, light in weight to avoid fatigue, and should 

 be fixed up and away from the head to allow a circulation of air. 

 The heavy helmets commonly seen in the Tropics appear to me 

 to be without justification. They are very fatiguing to the head 

 and neck of the wearer and answer no purpose which will not 

 be fulfilled by the lighter variety. The idea that there are inju- 

 rious rays emitted from the sun, which find their way through 

 the earth's atmosphere and which can not be stopped by ordinary 

 opaque material, is also without justification. 



Custom prescribes that the white man shall cover his body, 

 and, moreover, his insufficient skin pigmentation probably 

 demands it. The most favorable covering should be as thin a 

 material, pervious to air currents, as is consistent with decency. 

 White will generally absorb the smallest amount of radiated 

 energy." 



Rubner * gives the comparative absorption of different colored clothinp: 

 materials as follows: 



White 1.00 



Light yellow 1.02 



Light green 1.40 



Dark yellow 1.40 



Dark green 1.61 



Red 1.68 



Light brown 1.98 



Black 2.08 



Thus black is seen to absorb more than twice the quantity of heat 

 taken up by white, and the experiments with rabbits are strikingly con- 

 clusive upon the superiority in this respect of the protective value of 

 white over dark colors. The white rabbits, it is to be remembered live 

 much longer in the sunlight than those of the darker hues. 

 t 



' R. W. Wood has shown that ultra-violet light is not reflected from 

 all white surfaces. For example zinc oxide, or Chinese white, completely 

 absorbs the ultra-violet and when photographed by this light appears 

 absolutely black. Johns Hopkins University Circular (1910), 2. 9; and 

 Centurij Magazine (1910), February. 



'Schilling, Tropenhygiene. Leipzig (1909), 159. 



