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 rises and
falls and causes a continuous production of gas proportionate with the
suction of the pump.

The consumption of soda and acid is about 2 kilogrammes each for
charging 100 siphons or 150 bottles. The bicarbonate is known to be used
up when the liquid in the generator is seen to descend to the bottom of
the water level, n, fixed to the vessel, D.

_The Washer_ (Figs 1 and 4)--The gas, on leaving the generator, enters
the washer through a bent copper pipe, R. The washer is formed of two
ovoid glass flasks G G, mounted on a bronze piece, L, to which they are
fixed by screw rings, l, of the same metal. The two flasks, G G,
communicate with each other only through the tinned-copper tube q,
which is held in the mounting q, of the same metal. This latter is
screwed into the piece, L, and contains numerous apertures, through
which the gas coming in from the pipe, R, passes to reach the upper
flask, G. The gas is washed by bubbling up through water that has been
introduced through the cock, R. After it has traversed both flasks, it
escapes through the copper pipe, p, into which it is sucked by the
pump, P.

_The Pump_ (Figs 1, 5 and 6)--This consists of a cylindrical chamber, P,