following year. Gas-lighting became popular in London by 1816 and in the
course of the next few years it was adopted by the chief cities and
towns in the United Kingdom and on the Continent. It found its way into
the houses rather slowly at first, owing to apprehension of the
attendant dangers, to the lack of purification of the gas, and to the
indifferent service. It was not until the latter half of the nineteenth
century that it was generally used in residences.

The gas-burner first employed by Murdock received the name "cockspur"
from the shape of the flame. This had an illuminating value equivalent
to about one candle for each cubic foot of gas burned per hour. The next
step was to flatten the welded end of the gas-pipe and to bore a series
of holes in a line. From the shape of the flames this form of burner
received the name "cockscomb." It was somewhat more efficient than the
cockspur burner. The next obvious step was to slit the end of the pipe
by means of a fine saw. From this slit the gas was burned as a sheet of
flame called the "bats-wing." In 1820 Nielson made a burner which
allowed two small jets to collide and thus form a flat flame. The
efficiency of this "fish-tail" burner was somewhat higher than that of
the earlier ones. Its flame was steadier because it was less influenced
by drafts of air. In 1853 Frankland showed an Argand burner consisting
of a metal ring containing a series of holes from which jets of gas
issued. The glass chimney surrounded these, another chimney, extending
somewhat lower, surrounded the whole, and a glass plate closed the
bottom. The air to be fed to the gas-jets came downward between the two
chimneys and was heated before it reached the burner. This increased the
efficiency by reducing the amount of cooling at the burner by the air
required for combustion. This improvement was in reality the forerunner
of the regenerative lamps which were developed later.

In 1854 Bowditch brought out a regenerative lamp and, owing to the
excessive publicity which this lamp obtained, he is generally credited
with the inception of the regenerative burner. This principle was
adopted in several lamps which came into use later. They were all based
upon the principle of heating both the gas and the air required for
combustion prior to their reaching the burner. The burner is something
like an inverted Argand arranged to produce a circular flame projecting
downward with a central cusp. The air- and