406 



Mil. \\. T. DAVID ON THE RADIATION IN 



The chain-dotted curves in the same figure give the intrinsic radiance from thick- 

 nesses of gas inversely proportional to the density. The thicknesses are 60 cm. at 

 ^ atmosphere, 40 cm. at f^ atmosphere, 30 cm. at atmospheric density, and 24 cm. at 

 l atmospheres. In the calculation of the intrinsic radiance from these lengths the 

 formula on p. 401 has been used. The equations to these curves are of the form 



where 



R = k . D * 



R is the intrinsic radiance in calories per second from a thickness of 

 gas = 30/D cm., 



D the density of the gaseous mixtures in atmospheres, and 

 k a constant for each curve. 



The following table gives the value of k at various temperatures : 



TABLE XX. 



The following table gives the values which the intrinsic radiance from 1/D cm. 

 (where D is the density in atmospheres) would have were the gaseous mixtures 

 perfectly transparent. The intrinsic radiance corrected for absorption from 1 cm. is 

 the limit of R z /x when x = in the formula R, = RO. (l <T Kl ) ; this is equal to KB,,. 



TABLE XXI. 15-per-cent. Mixtures of Coal-gas and Air. Walls Black. 



Fluorite Window. 



