436 TRANSACTIONS OF SECTION B. 
maximum possible, with consequent decrease in the amount of ‘ convected’ 
heat. 
The known advantage of radiant heat being that it warms the walls, the 
furniture, and the occupants of the room rather than its atmosphere, the 
problem was how to increase efficiency in the direction of radiation so as to 
compensate, both in heating power and in economy, for the reduction in the 
temperature of the convection currents. The gas fire, which hitherto had been 
a haphazard evolution from the coal fire, now became the subject of a reasoned 
and drastic revolution. The convection chambers were dispensed with. The 
deep fire-chambers became a shallow space in the front of the apparatus, its 
depth only that of one piece of refractory material. The erratic arrangement 
of fireclay lumps was superseded by placing two or three such pieces one above 
the other exactly over the flame so as to form an envelope for it. A little later 
a more marked step in the evolution of the new radiating fire consisted in 
joining the two or three fireclay pieces into one, and thus making the firefront 
consist of a series of hollow fireclay columns (now known as radiants) per- 
forated in a design expressly contrived to promote uniform heating of the 
column throughout, and with each flame rising into the cavity of its radiant. 
Care was taken to prevent any impingement on the inner cone of the flame; by 
this means, and also by using a correctly designed burner, and by making due 
provision for the proportionment of the gas and air supplies, perfect combustion 
was ensured. A further important improvement was the dispensing with the 
cast-iron front bars hitherto used to retain the loose fireclay lumps, and the 
replacing of these bars by one slight horizontal rod. This arrangement not only 
left no obstruction in the path of the radiation, but vastly improved the appear- 
ance of the fire. The effect of these radical changes has been that the greater 
proportion of the energy developed by the combustion of the gas around and in 
contact with the radiants is transmitted into the apartment as radiant heat. 
This radiant heat quickly makes its warming effect felt by the occupants; yet, 
inasmuch as it passes through the air without sensibly warming it, the discom- 
forts formerly occasioned by the now discarded ‘convection’ methods are at an 
end. The walls and the objects in the room, becoming warmed by absorbed 
radiant heat, no longer abstract heat from the occupants, and further they 
gradually warm the air to a moderate degree by convection currents which, being 
necessarily at a low temperature, do not reproduce the former excessive moisture- 
absorbing condition in the air. 
This gradual warming of the air by contact with the objects in the room 
naturally cannot begin for some little time after the fire has been lighted—not 
indeed until the radiant heat of the fire has warmed the walls and furniture. 
From the outset, however, there is a certain proportion of convected heat from 
the stove (but at a low temperature, owing to the absence of the old special 
heating chambers), and this primary or direct low-temperature convection at 
once begins to gently raise the temperature of the air, thus anticipating—and 
later on co-operating with—the secondary low-temperature convection from the 
walls and furniture, in suitably warming—but not overheating—the air. It 
will thus be seen that although the earlier types of gas fire may have made 
their heating effect more quickly apparent, yet in the gas fires of to-day the 
primary convection is also doing its work from the first, though in a less conspi- 
cuous and more healthful way. In this way radiation has taken the place of con- 
vection as the mode of heat-transference principally aimed at in gas-fire design. 
Having thus traced the evolution of the modern gas fire, I come next to that 
on which the modern gas fire so largely depends—viz., radiation—to the problem 
of increasing which much research has been devoted. Progress towards higher 
radiant efficiency in a fire can be measured only when a reliable method of 
estimating the latter is available. The present accepted method is that adopted 
by the Joint Committee appointed in 1907 by the Institution of Gas Engineers 
and the University of Leeds, for the Investigation of Gas Fires; this method, 
which was originally suggested to the Committee by Professors W. A. Bone 
and William Stroud, is essentially a radiometer-cwm-thermopile method. Part 
of the radiant energy is directly determined (in kilogram centigrade units) by 
using a radiation calorimeter (or radiometer), and the remainder by means of 
a thermopile and galvanometer, standardised against the radiometer for each 
experiment. 
