1921.] Marsden and Fenton.—Coal, Gas, and Electricity. 263 
The figure given for coal involves a certain amount of storage, with 
consequent insulation losses ; but, on the other hand, the same coal would 
also serve for other purposes. It must be remembered also that the same 
efficiency would not be obtained for a single bath, for example, and when 
this and the labour are taken into account it would appear that a gas- 
califont is the most economical for heating bath-water, except where this 
is required in great quantity, when one of the special water-jacketed coal 
or coke furnaces used in heating buildings will certainly prove most 
economical. 
V. Comparison of. Fuels for Kitchen Cooking. 
Under this heading will be considered the heating of water in kettles 
.and pans for tea-making, stewing, washing dishes, &c. Gas is at present 
very generally used for this purpose, either by a single ring burner or 
Fig. 3.—The “ Magic ” kettle and “ Perfection ” oil-stove. 
on one of the ring burners on the top of an ordinary gas-stove. The 
efficiency of these burners varies somewhat according to the distance 
of the jets from the bottom of the kettle or pan, on the regulation of 
the air-supply, and on the size and nature of the base of the pan or 
kettle used. 
In the tests the burners were adjusted to approximate maximum 
efficiency, and a thin copper kettle was chosen, which gave a high 
efficiency, although experiments with thin aluminium pans of the same 
size of base gave practically identical figures. Experiments were also 
made with a special kettle recently placed on the market under the 
trade name of “ Magic.” This kettle is illustrated on its side in 
fig. 3 along with a “ Perfection ” stove. The essential feature of the 
kettle is that it gives a large heating-surface completely surrounding 
the hot gases from the flame, and also a brisk circulation of water 
past the heated surface. The kettle is somewhat . complicated in 
its construction, however, and repairs are likely to be much more 
