396 



MR. W T. DAVID ON THE RADIATION IN 



On comparing Curves A and B we find that when the walls are reflecting, the 

 radiation emitted by 59 cm. is over 30 per cent, greater than that emitted by 30 cm. 

 From Curves C and D we find that when the walls are black, 59 cms. radiate well 

 over 20 per cent, more heat than 30 cm. do until the temperature falls to about 

 2200 C. (abs.) (i.e., for about -Q second after the attainment of maximum pressure). 



2500 



zzoe 

 ffas 



neo 



tyoo /700 

 "C absolute . 



f6co 



/3OC 



Fig. 14. 



After this temperature the radiation from these two thicknesses becomes more and 

 more nearly the same until a temperature of about 1500 C. (abs.) is reached, when it 

 becomes the same. Thus it will be seen that when the walls are reflecting, the 

 gaseous mixture after explosion is highly transparent to its own radiation even after 

 the temperature has fallen below 1500 C. (abs.). It is also very transparent when 

 the walls are black in the initial stages of cooling, although later on, after the 

 temperature has fallen to about 1500 C. (abs.), it has become fairly opaque. 



The following table has been prepared from the curves in this figure. The second 

 column compares the radiation emitted from 30 cm. of the hot gaseous mixture when 

 the walls of the vessel are reflecting with that from the same thickness of gas at the 

 same temperature when the walls are black. The third column shows the same ratio 

 for 59 cm. effective length. 



