FRAGMENTS OF SCIENCE 



water, and determining the radiation from the two surfaces, 

 one of them is found to emit thirty-nine units of heat, while 

 the other emits seventy-four. This, surely, is a great dif- 

 ference. Here, however, is a second cube, having two of 

 its surfaces coated with the same powders, the only differ- 

 ence being that the powders are laid on by means of a 

 transparent gum. Both surfaces are now absolutely alike 

 in radiative power. Both of them emit somewhat more 

 than was emitted by either of the unvarnished powders, 

 simply because the gum employed is a better radiator than 

 either of them. Excluding all varnish, and comparing 

 white with white, vast differences are found; comparing 

 black with black, they are also different; and when black 

 and white are compared, in some cases the black radiates 

 far more than the white, while in other cases the white 

 radiates far more than the black. Determining, moreover s 

 the absorptive power of those powders, it is found to go 

 hand-in-hand with their radiative power. The good radi- 

 ator is a good absorber, and the bad radiator is a bad ab- 

 sorber. From all this it is evident that, as regards the 

 radiation and absorption of non-luminous heat, color teaches 

 us nothing; and that even as regards the radiation of the 

 sun, consisting as it does mainly of non-luminous rays, 

 conclusions as to the influence of color may be altogether 

 delusive. This is the strict scientific upshot of our re- 

 searches. But it is not the less true that in the case of 

 wearing apparel and this for reasons which I have given 

 in analyzing the experiment of Franklin black dresses are 

 more potent than white ones as absorbers of solar heat. 



Thus, in brief outline, have been brought before you a 

 few of the results of recent inquiry. If you ask me what 

 is the use of them, I can hardly answer you, unless you 



