the pipes, R
and N, are opened. After this the valve, I', is opened, and a current of
air is let in through the pipe, O'. This air, upon traversing the
chambers, B' and T', is raised to a high temperature through the heat
remaining in these chambers, and then enters at the bottom of the
generator, through the flue, E'. The air gas that now makes its exit
from the pipe, M, in the chamber, T, meets another current of air coming
from the pipe, N, and is thus burned. The products resulting from such
combustion pass into the chambers, B, and then into the chimney, through
the pipe, R. The temperature then rapidly lowers in the chambers, B',
and rises no less rapidly in the generator, A, while the chambers, B,
are soon heated to the same temperature that first existed in the
chambers, B'. As soon as the desired temperature is obtained in the
generator, A, and the chambers, B, the air is shut off by closing the
valve, I', of the pipe, O'; the valve, F', of the flue, E', is also
closed, the valves, G' and K', of the pipes, M' and Q', are opened, the
valves, G, H, and L, of the pipes, M, N, and R, are closed, and the
valve, F, of the flue, E, and the valve, J, of the pipe, P, are opened.
A current of steam enters the apparatus through the pipe, P, traverses
the chambers, B, and enters the generator through the flue, E. The gas
produced makes its exit from the generator, passes through the pipe, M',
and the chambers, T' and B', and the pipe, R, and enters the gasometer
through the pipe, Q'.

[Illustration: WATER-GAS APPARATUS.]

When the chamber, B, and the generator, A, are again in so cool a state
that the fuel no longer decomposes the steam easily, the valves are so
maneuvered as to stop the entrance of the latter, and to send a current
of air into the apparatus in the same direction that the steam had just
been taking. The temperature thereupon quickly rises in the generator,
A, while, at the same time, the combustion of the air gas produced soon
reheats the chambers, B'. The cooled products of combustion go, as
before, to the chimney. The position of the valves is then changed again
so as to send a current of steam into the apparatus in a direction
contrary to that which the air took in the last place, and the water gas
obtained again is sent to the gasometer.

As will be seen, the process is entirely continuous, each current of air
following the same direction in the apparatus (from left to right, or
right to left) that