Formerly all beer was fermented at a high temperature. The wort, after having been cooled in the backs, was run into a large vat, at a temperature of about 20° C. (68° F.). Yeast was then added to it, and when the fermentation began to show itself, in the formation of a light, white froth, upon the surface of the liquid, the wort was run into casks, having a capacity of from 50 to 100 litres (11 to 22 gallons)—75 litres being the commonest size. These casks were placed in cellars, having a temperature of from 18° C. to 20° C. (64° F. to 68° F.). The activity of fermentation soon produced a froth that grew thicker and more and more viscous in proportion to the quantity of yeast it contained. The yeast worked out of the bung-holes and dropped into a vessel placed under the casks; there it was gathered for subsequent operations. It always exceeded the quantity used in the first instance, the ferment increasing greatly during the process of fermentation. The increase in its weight varied with the weight of yeast used and the composition of the wort. Under the ordinary conditions of brewing, where the weight of the pitching yeast was about one thousandth part of the weight of the wort, the increase is said to have been from five to seven times the weight of the yeast; but such increase must naturally have been determined by the quality of the wort, the quantity of hops used, the action of oxygen, and the proportion of barm employed. The process of fermentation lasted from three to four days. By that time the beer was finished, and had become limpid, the fermentation having been completed. The bungs could then be placed in the casks, and the beer be delivered to the customer.[5] A certain amount of yeast still remained in the casks, and caused the beer to become thick, in transit; but a few days’ rest sufficed to restore its brilliancy, and render it fit for drinking or bottling. Here we have an explanation of the term “_high_ fermentation,” which has been applied to the foregoing process. This process is conducted at a high temperature, which, commencing at 19° C. or 20° C. (66° F. or 68° F.), is raised to 20° C. or 21° C. (68° or 70° F.) by the action of fermentation, which is always accompanied by an increase of heat.[6] This is not, however, the only reason for the use of the term “_high_ fermentation.” We have just seen that the fermenting casks were so arranged that most of the yeast produced during the process of fermentation would rise to the upper part of the casks and work out of the bung-holes. In this practical fact we have the actual origin of the expressions “_high fermentation_” and “_high beer_,” which are used to distinguish this peculiar fermentation and the quality of beer derived from it. As we have already observed, all beer was formerly produced by this mode of fermentation, which even at the present time is still practised in the breweries of Great Britain, where beer fermented at a low temperature is absolutely unknown.