, is
emphatically the more desirable position of affairs. But it in quite
simple to have carbide present in large excess of the water introduced
when the whole generator is contemplated, and yet to have the water
always in chemical excess in the desired manner; because to realise the
advantages of having water in excess, it is only necessary to subdivide
the total charge of carbide into a number of separate charges which are
each so small that more than sufficient water to decompose and flood one
of them is permitted to enter every time the feed mechanism comes into
play, or (in a non-automatic apparatus) every time the water-cock is
opened; so arranging the charges that each one is protected from the
water till its predecessor, or its predecessor, have been wholly
decomposed. Thus it is possible to regard either the carbide or the water
as the substance which has to be brought into contact with the other in
specified quantity. It is perhaps permissible to repeat that in the
construction of an automatic generator there is no advantage to be gained
from regulating the supply of both carbide and water, because just as the
mutual decomposition will begin immediately any quantity of the one meets
any quantity of the other, so the reaction will cease (except in one case
owing to "after-generation") directly the whole of that material which is
not in chemical excess has been consumed-quite independently of the
amount of the other material left unattacked.
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