ill more and its brilliancy increased, but not to a
degree sufficient to compensate for the diminished surface. The light,
you are doubtless aware, comes from the incandescence of the carbon,
heated by the union of the hydrogen of the gas with a portion of the
oxygen of the air."

The chemist now read from his manuscript again: "Carburetted hydrogen of
a passably good quality requires two volumes of pure oxygen for its
complete combustion and conversion into carbonic acid and water.
Atmospheric air contains, in its pure state, about twenty per cent. of
oxygen; therefore, one cubic foot of gas requires for its perfect
combustion ten cubic feet of air. If less be admitted to the flame, a
quantity of free carbon will escape, and be deposited in the form of
black smoke. If an excess of air be admitted, we shall find that the
quantity of nitrogen accompanying this excess has a tendency to
extinguish the flame, while it takes no part in the elective affinity
constantly going on between the other elements--namely, hydrogen, oxygen
and the vapor of carbon.

"Again," said he, turning down the gas, "if the flame be reduced to a
consumption of two feet per hour, its light will be equal to that of one
candle only; but on raising the chimney, thus, about half an inch from
the gallery or support the light is greatly increased, or by simply
placing a disk on top of the chimney the light is increased ninefold;
both of which effects seem to result from a diminished current of air,
while at the same time there is an ample supply. Lastly, with the
ordinary glass moon-globe so generally used in dwellings with the
fishtail burner little difference can be perceived between the light
given from the flame by four feet and that from six feet of gas per
hour, in consequence of the strong current of air passing up through the
globe; but if the top of the glass be enclosed by a talc cover having an
orifice in the centre about an inch in diameter, then the conditions of
the burner are completely changed. The light is greatly increased,
because the highest economical advantage is then approached."[2]

"Smoke from the aperture and lamp-black on the cover must result from
such an arrangement," objected the old gentleman.

"There need be very little of either," responded the chemist. "From some
burners there is little light without smoke. A smoky flame may arise
from too much carbon, but the gas companies in this part of the country
are not apt to