266 The N.Z. Journal of Science and Technology. [Jan, 
With regard to gas-fires a great variation is shown in the results of 
various experimenters, depending on the type of fire used. A good modern 
gas-fire, however, properly regulated gives 45 per cent.* radiant efficiency 
and 5 to 10 per cent, convection heat. An electric radiator, on the other 
hand, gives up the whole of its heat-energy to the room as radiant and 
convection heat in proportions depending on the type of radiator employed. 
We may summarize as follows for the sum of radiant and convection 
heats :— 
— 
Efficiency. 
B.Th.U. for Id. 
* 
Coal .. . 
25 
8,000 
Gas 
52* 
2,350 
Electricity 
100 
2,280 
2; 
o 
c n 
Fig. 6. 
Fig. 5.—An efficient type of open grate. 
Fig. 6. —This and fig. 7 show the distribution of the radiation from coal-fires in the 
grate shown in fig. 5 over the surface of an imaginary hemisphere of radius 34 - 4 in., 
with its centre at the centre front of the fire. Fig. 6, vertical distribution. 
Fig. 7. — Horizontal distribution (see explanation of fig. G). 
" See Bone, Callendar, and Yates, Proc. Roy. Soc., Ser. A, vol. 91, pp. 245-54, 1915. 
