his gas, through the action
of the air upon the fuel, is called "air gas," in order to distinguish
it from the "water gas" formed in the second period of the process.

The air gas, on issuing from the generator through the pipe, M', in
order to pass into the chamber, F', meets in the latter a second current
of air coming in through the pipe, N', and which burns it and produces,
in doing so, considerable heat. The strongly heated gases resulting from
the combustion traverse the regenerators, B', and give up to the bricks
therein the greater part of their heat, and finally make their exit,
relatively cool, through the pipe, R', which leads them to the chimney.
When the operation has been continued for a sufficient length of time to
give the refractory bricks in the chamber, B', next the regenerator a
high temperature, the valve, I, is closed, thus shutting off the
entrance of air through the pipe, Q. The valve, F, of the flue, E, is
also closed, and that of the pipe, M, is opened. The valves, G', H', L',
of the pipes, M', N', R', are closed, and that, F', of the flue, E', is
opened. The valve, J', of the pipe, P', is then opened, and a jet of
steam is introduced through the latter.

The steam becomes superheated in traversing the regenerators, B', and in
this state enters the bottom of the generator through the flue, E'. In
passing into the incandescent fuel that fills the generator, the steam
is decomposed, and there forms carbonic oxide, while hydrogen is
liberated. The mixture of these two gases with the hydrocarburets
furnished by the fuel constitutes water gas. This gas on making its exit
from the generator through the pipe, M', passes through the chambers, B,
and abandons therein the greater part of its heat, and enters the pipe,
R, whence it passes through Q into the purifiers, and then into the
gasometer.

As the production of water gas implies the absorption of a large
quantity of sensible heat, it is accompanied with a rapid fall of
temperature in the chambers, B', and eventually also in the generator,
A, while at the same time the chambers, B, are but moderately heated by
the sensible heat of the current of gas produced. When this cooling has
continued so long that the temperature in the generator, A, is no longer
high enough to allow the fuel to decompose the steam with ease, the
valve, J', of the pipe, P', that leads the steam is closed, as is also
the valve, K, of the pipe, Q, while the valves, L and H, of