300 



Mr. Dugald Clerk 



[Jan. 29, 



bridge coal gas, first with the vessel polished as highly as possible, 

 and, second, with the surface blackened over. Precautions were taken 

 to ensure that the mixture in the comparative experiments should be 

 of identical composition. Fig. 26 shows superposed the pressure 

 records obtained bv an optical indicator with one such comparison. 

 From this it wilT be seen that there is an increased maximum 



045 0-55 



SECONDS 



Fig. 26. 



pressure of between 3 and 4 lb. per square inch in the record with 

 the polished surface ; and further, the blackened surface cools the 

 hot gaseous contents more quickly. The gas temperature is higher 

 with the polished surface bv about 70^ C, near the temperature of 

 2000° C, which, at the high volumetric heat at that temperature, 

 amounts to about 5 per cent of the whole heat value of the inflam- 

 mable gas. 



5 t/j ii* <o 



1600 



1200 -6 



800 -^ 



400 -2 







3 ^^ -5 -6 



Time after Ignition -sec. 



Fig. 27. 



•a 



1-0 



Other experiments were made with a platinum strip bolometer, 

 which measured the radiation passing from the explosion vessel 

 through a fluorite window, which clearly proved that in 0*05 second 

 taken to attain maximum temperature and pressure, this mixture 

 lost nearly five per cent of the total heat in radiation. 



Fig. 27 shows the results of experiments by David with the 



