_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 enabling the revenue officers to assess the duty) to the _Collecting Vessel_,[4] and finally to the _Fermenting Vessels_, in which the wort is transformed into "green" beer. The latter is then cleansed, and finally racked and stored.