1921.] Marsden and Fenton.—Coal, Gas, and Electricity. 265 
3-7 times that of an ordinary kettle. This is an astonishing result, due to 
the largely increased heating-surface. 
Price per Unit. 
Efficiency. 
B.Th.U. 
for Id. 
Cost of heating 
2 Quarts Water 
from 66° F. to 
Boiling-point. 
Per Cent. 
d. 
Coal 
4s per hundred¬ 
weight 
8-5 
2,700 
0-28 
Gas 
8s. 4d. per 1,000 
feet 
50-0 
2,250 
0-34 
Electricity 
ljd. per unit 
75-0 
1.700 
0-45 
Kerosene (ordinary 
kettle) 
£1 9s. per case of 
8J gallons 
540 
1-40 
Kerosene (“ Magic ” 
kettle) 
Ditto .. 
• • 
1,950 
0-39 
As in the previous cases, the figures for coal are for continuous use over 
a few hours, although the same range is also fulfilling other functions. 
On the whole, when labour is taken into account, it would appear that 
with a well-designed stove gas is the most economical of the fuels for the 
above purposes. 
VI. Comparison of Fuels for Heating of Rooms. 
Although we made certain preparations for tests on the heating of rooms, 
such as sitting-rooms, these were discontinued, as the question has been 
very completely dealt with by Dr. Margaret White Fishenden* in a report, 
an advance copy of which we were fortunate enough to obtain. This report 
describes extensive tests of the radiant efficiency of coal burnt in various 
types of grates. Different grates gave efficiencies of from 20 to 24 per 
cent, for good cobble coal, and showed no advantage in favour of the 
modern grate. 
Different grates, however, were found to throw the maximum radiant 
heat in different directions, the most efficient grate from this point of view 
being shown in fig. 5, and the distribution of radiation from it in figs. 6 and 7. 
In the latter diagrams the radius vector drawn from the fire to the curve 
gives the amount of radiation in that direction. The various curves are 
for different orientations. 
The efficiencies of the grate shown in the figure for various fuels may 
be summarized as follows : Coal, 24 per cent, radiant efficiency ; slack 
•coal, 20 per cent. ; anthracite, 27 per cent. ; dry coke, 26 per cent. ; damp 
coke, 21 per cent. ; low-temperature carburization coke, 33 per cent. 
Three practical deductions arise from the tests, as follows : (1) Every 
grate should be provided with an easily adjustable register for controlling 
the draught, this being placed about 1 ft. above the opening of the chimney ; 
(2) grates should be as little recessed as possible ; and (3) fireplaces should 
always be placed against an inner wall. With proper draught-regulation 
.and a fireplace against an inner wall an additional 35 per cent, of the 
ieating-value of the fuel can be used for actual heating of the house. 
* The Coal Fire, Fuel Research Board of Great Britain Special Report No. 3, H.M. 
Stationery Office, 4s., 1920. 
