76 Major W. T. David on the Calculation of 



and probably will lie rather nearer the latter *. The other 

 for Z = 15 will in all probability lie between R imaX . from 

 15 cm. in the blackened vessel (which is 4*7) and half that 

 from 30 cm. in the blackened vessel (which amounts to 

 .3-3) f. 



Fiir. 4. 



15 30 4-5 60 



Cy//'n</er cf/m ens ions — L - cn7. 



F The thick line then is a fair curve drawn through the two 

 -definite points (0, 0) and (30, 6'6) and between the two pairs 

 of points (15, 3-3-4-7) and (59, 8-4-10-9). 



* There seems little doubt that the radiation from a layer of gas 

 increases not only with its thickness but with its lateral dimensions as 

 well. The radiation from a cylindrical mass of gas 59 cm. X 59 cm. will 

 therefore be greater than that from a cylindrical mass 59 cm. long and 

 30 cm. in diameter. On the other hand, the radiation from 59 cm. in 

 the polished vessel approximates to that from a mass of gas 59 cm. 

 in thickness but of infinite lateral dimensions. 



t Ri max. from 15 cm. in the blackened vessel will be greater than that 

 'from a cylindrical mass 15 cm. by 15 cm., because in the former case 

 the lateral dimensions are greater than in the latter. 



