ABSTRACTS 



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 this issue. 



RADIATION. — The calculation of the constants of Planck's radiation 



equation; an extension of the theory of least squares. Harry M. 



Roeser. Bureau of Standards Scientific Paper No. 204 (Bull. 



Bur. Stds. ; 14: 31-77). 1917. 



The problem of computing from experimental data the constants, 



ci and c 2 , of Planck's radiation equation for the distribution of energy 



in the spectrum of a black body is attacked by the method of least 



squares. The data were furnished by Dr. W. W. Coblentz. The 



observation equations were reduced by taking logarithms of both 



sides and assigning proper weights to the -equations so transformed. 



The method of assigning weights is given in a general form that can 



be adapted to any scheme of transformation. TT , r _ 



H. M. R. 



PHYSIOLOGICAL OPTICS.— The luminous radiation from a black 

 body, and the mechanical equivalent of light. W. W. Coblentz 

 and W. B. Emerson. Bureau of Standards Scientific Paper No. 

 305 (Bull. Bur. Stds., 14: 255-268). 1917. 

 In this paper the visibility of radiation by the average eye is applied 

 to radiation problems, including the luminous energy emitted by a black 

 body at various temperatures, the luminous efficiency, the Crova wave- 

 length, and the mechanical equivalent of light. The visibility curve 

 of the average eye (125 observers) gives a mechanical equivalent of 1 

 lumen = 0.00161 watt of radiant energy of maximum visibility. 

 Various other determinations give values varying from 0.00157 to 

 0.00160 watt. The most reliable data now available indicate a value 

 of 1 lumen = 0.0016 watt of radiant energy of maximum visibility, or 

 1 watt = 625 lumens = 49.8 candles of radiant energy of maximum 

 luminous efficiency. W. W. C. 



542 



