ith, are not without some defects, for the gas is
produced in them intermittingly and at intervals, and more rapidly than
it is used, thus necessitating the use of a gasometer, numerous and
large washers, complicated piping, and, besides, of an acid cock.

To get rid of such drawbacks, it became necessary to seek a means of
rendering the production of the gas continuous, and of regulating it
automatically without the aid of the operator. Mr. Mondollot has
obtained such a result through a happy modification of the primitive
system of the English engineer Bramah. He preserves the suction and
force pump but, while applying it to the same uses, he likewise employs
it, by the aid of a special arrangement, so as to distribute the
sulphuric acid automatically over the chalk in the generator, and to
thus obtain a regular and continuous disengagement of carbonic acid gas.
The dangers and difficulties in the maneuver of an acid cock are
obviated, the gasometer and its cumbersome accessories are dispensed
with, and the purification is more certain, owing to the regularity with
which the gas traverses the washers.

In the accompanying plate we have figured three types of these
apparatus. The first that we shall describe is arranged for the use of
bicarbonate of soda. This apparatus consists (1) of a _generator_, C D,
(2) of a double _washer_ G G, (3) of a _suction pump_, P, and (4) of a
_saturator_, S (See Figs 1 to 9).

_The Generator._--This consists of a cylindrical leaden receptacle, D,
on the bottom of which rests a leaden bell containing apertures, c, at
its base. A partition, c, into which is screwed a leaden tube, C,
containing apertures divides the interior of the bell into two
compartments. The upper of these latter is surmounted by a mouth, B,
closed by a clamp, and through which the bicarbonate of soda is
introduced. A definite quantity of water and sulphuric acid having been
poured into the receptacle, D, a level tends to take place between the
latter and the bell, C, the liquid passing through the apertures. But
the acidulated water, coming in contact with the soda, sets free
carbonic acid gas, which, having no exit, forces the water back and
stops the production of gas until the apparatus is set in motion. At
this moment, the suction of the pump causes a new inflow of acidulated
water upon the soda, from whence another disengagement of gas, and then
a momentary forcing of the water, whose level thus alternately ris