596 PROCEEDINGS OP THE AMERICAN ACADEMY. 



0.46 per cent. On this account the energy E of the standard radiation 

 must be reduced by the above percentages. Applying these corrections * 

 and the corrections due to the diffused radiation from the black coating 

 on the silver disc, the energy of the standard radiation becomes 



1. ■ E. ' 986 



(a) through air, E„ X ^^ ; 



,ix , ,- .i i r- °- 986 



(h) through red glass, E g X ^^ ; 



/N , E* -" 5 



(c) through water, E w X ^-^ . 



Hence the pressure produced by standard radiation calculated by Max- 



well's formula, j? = ^ , since p = 0.848, becomes 



o X 10 



, . . _, 1.848 0.986 



(«) through air = A. X ^-^5 X ^^ 



1.848 0.986 * , 



= L108 x 3^10^ x om x 10 dynes 



= (7.05 ± 0.03) X 10~ 5 dynes ; 



/IN ,. U * 1 E> J' 848 ' 986 



(6) through red glass = ^ g X g ^ 1Q10 X ^^ 



1.848 0.986 nrtfi , 



= L078 X 5xIoS X 0954 X 10 d ^ S 



= (6.86 ± 0.03) X 10- 5 dynes; 



, N , ' _ 1.848 0.995 



( C ) through water = E w X ^^ X ^ 



1.848 0.995 



= 1 - 008X sino* x 0^54 >< 106d y- s 



= (6.48 ± 0.04) X 10- 5 dynes. 



* As the average pitch of the cone of the incident beam was about one part in 

 forty, no correction need be applied for inclination. Furthermore, the inside of 

 the bell-jar was blackened and the zero of the balance was so chosen that energy 

 reflected from the window admitting the beam could produce no pressure effects. 



