1921.] 
Marsden and Fenton.—Coal, Gas, and Electricity. 
257 
THE RELATIVE EFFICIENCY OF COAL, GAS, AND 
ELECTRICITY FOR DOMESTIC PURPOSES. 
By Professor E. Marsden, M.C., D.Sc., and Miss E. W. J. Fenton, M.Sc. 
Contents. 
I. Introduction. 
II. Tests with a Shaddock Range. 
III. Comparison of Fuels for Oven Cooking. 
IV. Comparison of Fuels for heating Water for Baths, &c. 
V. Comparison of Fuels for Kitchen Cooking. 
VI. Comparison of Fuels for Heating of Rooms. 
VII. Efficiency of various Methods of Lighting. 
VIII. Efficiency of Power-production. 
IX. Summary and General Considerations. 
I. Introduction. 
The most fundamental problem affecting our comfort, health, and well-being 
is fuel. There is at present a serious shortage of coal, with an increasing 
demand for it, and it appears unlikely that the situation in this respect 
will ever become wholly satisfactory, since, as time goes on, New Zealand 
will become less self-supporting in coal. These facts, together with the 
slow development of our hydro-electric power, have made it incumbent 
that we shall take stock of our fuel and energy resources with a view to 
economy and prevention of waste, so that the fullest use may be made of 
such fuel as is available. The economic aspect of the question has so far 
almost entirely been neglected in the Dominion—so much so that, for 
example, there is no legislation governing the thermal value of the gas 
supplied by the different gas companies. 
The investigation to be described in the present paper had for its object 
the obtaining of data relative to the efficiency of different fuels when used 
for various domestic purposes. The question will be treated mainly from 
the consumer’s point of view, since the steady increase in the price of fuel 
has made necessary a consideration of how economies may be effected. It 
is also hoped that the information may be useful for architects when 
deciding on methods of heating, for example, or the correct placing of fire¬ 
places. 
It may perhaps be of interest at the outset to recapitulate a few of the 
more elementary terms and facts concerning heat and energy. Heat is 
generally measured either in British thermal units (B.Th.U.) or in calories. 
A British thermal unit is the amount of heat required to raise the temperature 
of 1 pound of water by 1° Fahrenheit, while a calorie is the amount of heat 
required to raise 1 gramme of water through a range of temperature of 1° 
centigrade. Since 1 lb. = 454 grm., and 180° F. = 100° C., it follows that 
1 B.Th.U. = 100 = 252 calories. 
loO 
Heat is transferred from one point to another by three chief methods— 
(L) conduction, in which heat-energy is handed on mechanically from one 
part of a body to another ; (2) convection, which is the transfer of heated 
fluids by motion due to differences of density caused by heat; (3) radiation, 
