the feeding mechanism to drop the proper amount of carbide into the water
as required by the demands of the torches. The charge of carbide is of one
of the smaller sizes, usually "nut" or "quarter."

_Feed Mechanisms._--The device for dropping the carbide into the water
is the only part of the machine that is at all complicated. This
complication is brought about by the necessity of controlling the mass of
carbide so that it can never be discharged into the water at an excessive
rate, feeding it at a regular rate and in definite amounts, feeding it
positively whenever required and shutting off the feed just as positively
when the supply of gas in the holder is enough for the immediate needs.

[Illustration: Figure 10.--Carbide to Water Generator. A. Feed motor weight;
B. Carbide feed motor; C. Carbide hopper; D. Water for gas generation;
E. Agitator for loosening residuum; F. Water seal in gas bell; G. Filter;
H. Hydraulic Valve; J. Motor control levers.]

The charge of carbide is unavoidably acted upon by the water vapor in the
generator and will in time become more or less pasty and sticky. This is
more noticeable if the generator stands idle for a considerable length of
time This condition imposes another duty on the feeding mechanism; that is,
the necessity of self-cleaning so that the carbide, no matter in what
condition, cannot prevent the positive action of this part of the device,
especially so that it cannot prevent the supply from being stopped at the
proper time.

The gas holder is usually made in the bell form so that the upper portion
rises and falls with the addition to or withdrawal from the supply of gas
in the holder. The rise and fall of this bell is often used to control the
feed mechanism because this movement indicates positively whether enough