380 



MR. W. T. DAVID ON THE RADIATION IN 



of surface, in the three positions A, B, and C, as ordinates with times from ignition 

 as abscissae in explosions of approximately 9'8-per-cent. mixtures. These curves were 

 taken from those on the films traced by the recording galvanometer after allowing for 

 a small loss of heat from the bolometer. This loss was determined for each film in 

 the manner shown previously. The curves marked B, b were taken from the record, 

 a print of which is shown in fig. 3. 



T/me offer 



Fig. 4. 



Gas-temperature curves are also shown in the same figure, corresponding to the 

 radiation curves. These curves were deduced from the pressure curves on the films 

 by means of the equation pv = R0, after allowing for a 2'4-per-cent. contraction of 

 volume (which occurs in the combination of a 9'8-per-cent. mixture of Cambridge 

 coal-gas and air). They give the mean absolute temperatures of the gaseous mixture, 

 assuming it to be a perfect gas, or, at any rate, having the difference of its specific 

 heats at constant pressure and constant volume independent of the density and 

 temperature. 



Fig. 5 shows the rates at which the walls are receiving heat by radiation in calories 

 per sq. cm. per second at the three places A, B, and C, plotted against the mean 

 absolute temperatures of the gas. These curves have been obtained from the 

 radiation curves in fig. 4 by differentiation. It will be noted that the top parts of 

 the end cover receive more heat by radiation than the bottom parts, or, in other 

 words, the hot gas at the top of the vessel radiates more strongly than the colder gas 

 at the bottom. 





