the flame, so that with a small flame the total effect is very great,
and with a very large flame almost _nil_.

The first point, therefore, to attend to is that the burner shall be
made of a good non-conductor. In the next place, the flow of the gas
must be regulated to the burner, as, if you have a pressure higher
than that for which the burner is constructed, you at once obtain a
roaring flame and a loss of illuminating power, as the too rapid rush
of gas from the burner causes a mingling of gas and air and a
consequent cooling of the flame. The tap also which regulates the
flame is better at a distance from the burner than close to it, as any
constriction near the burner causes eddies, which give an unsteady
flame.

These general principles govern all burners, and we will now take the
ordinary forms in detail. In the ordinary flat flame burner, given a
good non-conducting material, and a well regulated gas supply, little
more can be done, while burning it in the ordinary way, to increase
its luminosity; and it is the large surface of flame exposed to the
cooling action of the air which causes this form of burner to give the
lowest service of any per cubic foot of gas consumed. Much is done,
moreover, by faulty fittings and shades, to reduce the already poor
light given out, because the light-yielding power of the flame largely
depends upon its having a well rounded base and broad, luminous zone;
and when a globe with a narrow opening is used with such a flame--as
is done in 99 out of 100 cases--the updraught drags the flame out of
shape, and seriously impairs its light-giving powers, a trouble which
can be got over by having the globe with an opening at the bottom not
less than 4 inches in diameter, and having small shoulders fixed to
the burner, which draw out the flame and protect the base from the