Lights of high intensity, such as powerful gas-burners or oil-
lamps, must give a higher degree of illumination in their immediate
vicinity than is really necessary, if they are to illuminate adequately
the more distant objects. The dissemination and diffusion of their light
can be greatly aided by suitable colouring of ceilings, walls and
drapings; but unless the illumination by means of lights of relatively
high intensity is made almost wholly indirect, candles or other lights of
low intensity, such as small electric glow-lamps, can, by proper
distribution, be made to give more uniform or more suitably apportioned
illumination. In this respect candles have an economical and, in some
measure, a material advantage over acetylene also. (But when the method
of lighting is by flames--candle or other--the multiplication of the
number of units which is involved when they are of low intensity,
seriously increases the risk of fire through accidental contact of
inflammable material with any one of the flames. This risk is much
greater with naked flames, such as candles, than with, say, inverted
incandescent gas flames, which are to all intents and purposes fully
protected by a closed glass globe.
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