wer. The blower is well oiled, and as oil is gradually carried in
with the air, a small pet-cock at the bottom of the T following the
blower allows any accumulated oil to be drawn away from time to time.
The air entering the valve system at H enters through a cross, two arms
of which connect with two "white star" valves. The upper part of the
cross is connected to a small rubber tubing and to the mercury
manometer D, which also serves as a valve for passing a given amount of
air through a series of U-tubes for analysis of the air from time to
time. It is assumed that the air drawn at the point H is of
substantially the same composition as that inside the chamber, an
assumption that may not be strictly true, but doubtless the sample thus
obtained is constantly proportional to the average composition, which
fluctuates but slowly. Ordinarily the piping leading from the left-hand
arm of the tube D is left open to the air and consequently the
difference in the level of the mercury in the two arms of D indicates
the pressure on the system. This is ordinarily not far from 40 to 50
millimeters of mercury.

[Illustration: FIG. 30.--Diagram of absorber table. 1 and 2 contain
sulphuric acid; K contains potash-lime; G, sodium bicarbonate can; F,
rotary blower for maintaining air-current; H, valves for closing either
side; and D, mercury manometer and valve for diverting air to U-tubes on
table. Air leaves A, passes through the meter, and then through drying
tower B and through C to ingoing air-pipe. At the left is the regulating
rheostat and motor and snap-switch. General direction of ventilation is
indicated by arrows.]

The absorber table, with the U-tubes and meter for residual analyses, is
shown in the foreground in fig. 2. The two white porcelain vessels with
a silver-plated can between them are on the middle shelf. The sodium
bicarbonate can, for removing traces of acid fumes, is connected in an
upright position, while the motor, the controlling rheostat, and the
blower are supported by the legs near the floor. The two rubber pipes
leading from the table can be used to connect the apparatus either with
the bed or chair calorimeter. In fig. 4 the apparatus is shown connected
with the bed calorimeter, but just above the lowest point of the rubber
tubing can be seen in the rear the coupling for one of the pipes leading
from the chair calorimeter. The other is immediately below and to the
left of it.

OXYGEN SUPPLY.

The r