are obvious
now, but Argand for his achievements is entitled to a place among the
great men who have borne the torch of civilization. He took the first
step toward adequate artificial light and opened a new era in lighting.

The various improvements of the oil-lamp achieved by Argand combined to
effect complete combustion, with the result that a steady, smokeless
lamp of considerable luminous intensity was for the first time
available. Many developments followed, among which was a combination of
reservoir and gravity feed which maintained the oil at a constant level.
In later lamps, upon the adoption of mineral oil, this was found
unnecessary, perhaps owing to the construction of the wick and to the
physical characteristics of the oil which favored capillary action in
the wick. However, the height of the oil in the reservoir of modern
oil-lamps makes some difference in the amount of light emitted.

The Carcel lamp, which appeared in 1800, consisted of a double piston
operated by clockwork. This forced the oil through a tube to the burner.
Franchot invented the moderator lamp in 1836, which, because of its
simplicity and efficiency soon superseded many other lamps designed for
burning animal and vegetable oils. The chief feature of the moderator
lamp is a spiral spring which forces the oil upward through a vertical
tube to the burner. These are still used to some extent in France, but
owing to the fact that "mechanical" lamps eventually were very generally
replaced by more simple ones, it does not appear necessary to describe
these complex mechanisms in detail.

When coal is distilled at moderate temperatures, volatile liquids are
obtained. These hydrocarbons, being inflammable, naturally attracted
attention when first known, and in 1781 their use as fuel for lamps was
suggested. However, it was not until 1820 that the light oils obtained
by distilling coal-tar, a by-product of the coal-gas industry which was
then in its early stage of development, were burned to some extent in
the Holliday lamp. In this lamp the oil is contained in a reservoir from
the bottom of which a fine metal tube carries the oil down to a
rose-burner. The oil is heated by the flame and the vaporized mineral
oil which escapes through small orifices is burned. This type of lamp
has undergone many physical changes, but its principle survives to the
present time in the gasolene and kerosene burners hanging on a pole by
the side of the street-peddle