apparatus I employ for this purpose is composed of a large jar or
pitcher A, Pl. XII. Fig. 4. surrounded at its upper edge by a rim of
iron properly cemented at DE, and receding from the jar at BC, so as to
leave a furrow or gutter xx, between it and the outside of the jar,
somewhat more than two inches deep. The cover or lid of the jar, Fig. 5.
is likewise surrounded by an iron rim f g, which adjusts into the
gutter xx, Fig. 4. which being filled with mercury, has the effect of
closing the jar hermetically in an instant, without using any lute; and,
as the gutter will hold about two inches of mercury, the air in the jar
may be made to sustain the pressure of more than two feet of water,
without danger of its escaping.

The lid has four holes, T h i k, for the passage of an equal
number of tubes. The opening T is furnished with a leather box, through
which passes the rod, Fig. 3. intended for raising and lowering the wick
of the lamp, as will be afterwards directed. The three other holes are
intended for the passage of three several tubes, one of which conveys
the oil to the lamp, a second conveys air for keeping up the combustion,
and the third carries off the air, after it has served for combustion.
The lamp in which the oil is burnt is represented Fig. 2; a is the
reservoir of oil, having a funnel by which it is filled; b c d e f g h
is a syphon which conveys the oil to the lamp 11; 7, 8, 9, 10, is the
tube which conveys the air for combustion from the gazometer to the same
lamp. The tube b c is formed externally, at its lower end b, into a
male screw, which turns in a female screw in the lid of the reservoir of
oil a; so that, by turning the reservoir one way or the other, it is
made to rise or fall, by which the oil is kept at the necessary level.

When the syphon is to be filled, and the communication formed between
the reservoir of oil and the lamp, the stop-cock c is shut, and that
at e opened, oil is poured in by the opening f at the top of the
syphon, till it rises within three or four lines of the upper edge of
the lamp, the stop-cock k is then shut, and that at c opened; the
oil is then poured in at f, till the branch b c d of the syphon is
filled, and then the stop-cock e is closed. The two branches of the
syphon being now completely filled, a communication is fully established
between the reservoir and the lamp.

In Pl. XII. Fig. 1. all the parts of the lamp 11, Fig. 2. are
represented magnified, to sho