th of the acid, and the extent of
the pressure at which the starch is converted. In England the materials
from which glucose is manufactured are generally sago, rice and purified
maize. In Germany potatoes form the most common raw material, and in
America purified Indian corn is ordinarily employed.

_Hop substitutes_, as a rule, are very little used. They mostly consist of
quassia, gentian and camomile, and these substitutes are quite harmless
_per se_, but impart an unpleasantly rough and bitter taste to the beer.

_Preservatives_.--These are generally, in fact almost universally, employed
nowadays for draught ales; to a smaller extent for stock ales. The light
beers in vogue to-day are less alcoholic, more lightly hopped, and more
quickly brewed than the beers of the last generation, and in this respect
are somewhat less stable and more likely to deteriorate than the latter
were. The preservative in part replaces the alcohol and the hop extract,
and shortens the brewing time. The preservatives mostly used are the
bisulphites of lime and potash, and these, when employed in small
quantities, are generally held to be harmless.

BREWING OPERATIONS.--The general scheme of operations in an English brewery
will be readily understood if reference be made to fig. 1, which represents
an 8-quarter brewery on the _gravitation system_, the principle of which is
that all materials to be employed are pumped or hoisted to the highest
point required, to start with, and that subsequently no further pumping or
hoisting is required, the materials (in the shape of water, malt, wort or
hops, &c.) being conveyed from one point to another by the force of
gravity.

The malt, which is hoisted to the top floor, after cleaning and grading is
conveyed to the _Malt Mill_, where it is crushed. Thence the ground malt,
or "grist" as it is now called, passes to the _Grist Hopper_, and from the
latter to the _Mashing Machine_, in which it is intimately mixed with hot
water from the _Hot Liquor Vessel_. From the mashing machine the mixed
grist and "liquor" pass to the _Mash-Tun_, where the starch of the malt is
rendered soluble. From the mash-tun the clear wort passes to the _Copper_,
where it is boiled with hops. From the copper the boiled wort passes to the
_Hop Back_, where the insoluble hop constituents are separated from the
wort. From the hop back the wort passes to the _Cooler_, from the latter to
the _Refrigerator_, thence (for the purpose of