Barkett — Amount of Light Scattered from Rough Surfaces. 197 



liquid through whioli tlie light passes reduces the intensity of the transmitted 

 light by a given ratio, it follows that as the depth of the absorbing liquid 

 increases in arithmetical progression, the intensity of the light is diminished 

 in geometrical progression, and accordingly the law is expressed by an 

 exponential function. This law, however, only holds true if no light were 

 lost by internal reflection and scattering within the liquid, and if the light is 

 of a given wave-length. By employing the revolving sector, fig. 1, which 

 can be adjusted to reduce by definite amounts the incident light, the coefficient 

 of transmission of white, or of monochromatic, light through a neutral tinted 

 or coloured liquid can be experimentally determined ; and thus the actual law 

 of absorption in any given case can be found. To this I hope to return in 

 a subsequent paper. 



