404 



MR. W. T. DAVID ON THE RADIATION IN 



30 cm. (walls reflecting) are somewhat too low on account of the reduced radiating 

 power of the gas at the end of the cone owing to its being near the blackened patch 

 opposite the bolometer. 



Table XVII. gives the ratio of the intrinsic radiance from 59 cm. to that from 

 30 cm. of the gaseous mixtures of the various densities when the walls of the 

 explosion vessel were black. 



The second column in the following table shows the ratio of the intrinsic radiance 

 from (x59) cm. of the gaseous mixture at atmospheric density to that from 

 ( x 30) cm. The third column shows the same ratio for (f x 59) cm. and (f x 30) cm. ; 

 the fourth (which is the same as the fourth column in Table XVII. above) for 59 cm. 



TABLE XVIII. 15-per-cent. Mixtures of Coal-gas and Air at Atmosphere Density. 



Fluorite Window. 



and 30 cm.; and the fifth for (l^x 59) cm. and (l^x 30) cm. These ratios have been 

 calculated from Curves C, D, and S, fig. 15, by means of the formula given on p. 401. 



Were the absorption and transparency of a column of gas whose length is inversely 

 proportional to the density independent of the density the ratios given in the 

 corresponding columns of Tables XVII. and XVIII. should be the same. There is, 

 however, a considerable difference between them. Those in the second and third 

 columns of Table XVIII. are distinctly greater than those in the corresponding 

 columns of Table XVII., while those in the last column of the former table are less 

 than those in the last column of the latter table. This shows that the transparency 

 of a column of gas whose length is inversely proportional to the density increases as 

 the density increases, at least, when the gaseous mixtures are enclosed in vessels of 

 the same dimensions. 



The curves in fig. 16 give the intrinsic radiance from the gaseous mixtures of the 

 same strength but of various densities at the same mean gas temperatures. The 

 dotted curves give the intrinsic radiance from a thickness of 59 cm. and the full 

 curves that from 30 cm. It will be seen that the emission from a definite thickness 





