ON GASEOUS EXPLOSIONS. 



225 



There cannot be any question that the whole of the heat recorded by 

 this platinum bolometer is radiated heat, and I do not think that there 

 is much doubt that, subject to any reflection from the surface of the 

 platinum (which has not been allowed for), the above figures represent 

 the amount of radiation coming through the fluorite window. Fluorite 

 is said to absorb about 5 per cent, of the radiation falling upon it, but 

 no allowance has been made for this. It will be seen that the radiation 



Fig. 7. 



here recorded exceeds by about 50 per cent, the difference between the 

 heat absorption with the blackened and polished surfaces. When a 

 plate of glass is substituted for the fluorite plate the heat absorbed by 

 the bolometer is reduced to about one-third of the above amounts, and 

 if the platinum surface is polished instead of blackened, the heat recorded 

 is only 20 per cent. The latter figure agrees fairly well with the result 

 given by Hagen and Rubens for the reflecting power of polished 

 platinum. 1 



APPENDIX C. 



Abstracts from various Papers relating to the Application of Heat Radiation 

 from Luminous Flames to Siemens' Regenerating Furnaces. 

 In September 1884 Mr. Fr. Siemens read a paper before the 

 Iron and Steel Institute in which he described the application of radiant 



1 Z. filr Instr. Kunde, 22, p. 52 (1902). 



