gas-passages are directly
above the flame and are heated by it. In 1879 Friedrich Siemens brought
out a lamp of this type which was adapted from a device originally
designed for heating purposes, owing to the superior light which was
produced. This was the best gas-lamp up to that time. Later, Wenham,
Cromartie, and others patented lamps operating on this same principle.

Murdock early modified the Argand burner to meet the requirements of
burning gas and by using the chimney obtained better combustion and a
steadier flame than from the open burners. He and others recognized that
the temperature of the flame had a considerable effect upon the amount
of light emitted and non-conducting material such as steatite was
substituted for the metal, which cooled the flame by conducting heat
from it. These were the early steps which led finally to the
regenerative burner.

The increasing efficiency of the various gas-burners is indicated by the
following, which are approximately the candle-power based upon equal
rates of consumption, namely, one cubic foot of gas per hour:

Candle-power
per cubic foot of
gas per hour

Fish-tail flames, depending upon size 0.6 to 2.5
Argand, depending upon improvements 2.9 to 3.5
Regenerative 7 to 10

It is seen that the possibilities of gas lighting were recognized in
several countries, all of which contributed to its development. Some of
the earlier accounts have been drawn chiefly from England, but these are
intended merely to serve as examples of the difficulties encountered.
Doubtless, similar controversies arose in other countries in which
pioneers were also nursing gas-lighting to maturity. However, it is
certain that much of the early progress of lighting of this character
was fathered in England. Gas-lighting was destined to become a thriving
industry, and is of such importance in lighting that another chapter is
given its modern developments.

VII

THE SCIENCE OF LIGHT-PRODUCTION

In previous chapters much of the historical development of artificial
lighting has been presented and several subjects have been traced to the
modern period which marks the beginning of an intensive attack by
scientists upon the problems pertaining to the production of efficient
and adequate light