Beneath the grain floor a fire is maintained. In the beginning the temperature of the drying floor should be about 85∞ F., but this is increased gradually to about 104∞ F. until most of the moisture has been removed. The heat is then raised to from 120∞ F. to 130∞ F., thus completely drying the grain. The germinated green or dried barley is called malt. It is of good quality when the grain is round and flowery; when it crumbles easily and when its taste is sweetish and agreeable. Pale malt or that which has been hardly altered from its original color is the best for distillation. Before the malt can be used it should be screened so as to remove the rootlets. Two hundred and twenty lbs. of barley should yield from 275 to 350 lbs. of green malt, about 200 lbs. of air dried malt, and from 175 to 190 lbs. of kiln dried malt. In large plants malting is now so carried on that the steeping germination and drying are all accomplished in one vessel or container, by one continuous operation. This vessel is commonly in the form of a drum of sheet iron, revolving at a very slow speed. Moist air is introduced and the carbonic acid laden air withdrawn. After germination the malt is dried by passing in dry air at the proper temperature. As these systems are only adopted to large distilleries, using expensive machinery, further reference to them is not considered necessary in this volume. Previous to use the malt must be finely ground or crushed either before or after mixing with the materials to be mashed. It is not necessary or advisable that the malt be reduced to flour. The use of malt with other materials in order to form a fermentible mash, will be considered in the chapters on specific mashes. CHAPTER VII. ALCOHOL FROM POTATOES. In certain countries, as for instance Germany and France, potatoes form the greatest source of alcohol, particularly for industrial purposes. With the possible exception of corn and beets they will probably be most used in America. The best potatoes for distilling are those which are most farinaceous when boiled. In other words, those which are "mealy" and most appetizing. These give the largest yield of alcohol per bushel. The best season of the year in which to use potatoes is from October to March, when they germinate. The potatoes should be kept in dry cellars, and at even temperatures, warm enough to prevent freezing and yet not so warm that they will rot or sprout. Diseased potatoes may however be used, if they have not been attacked by dry rot, though they are not so easily worked. Frosted potatoes may be also used, but they must not have been completely frozen. Before being steamed, the potatoes should be washed, either by hand or by a machine, care being taken to remove all stones, clods of earth, and other foreign substances which might impede the subsequent operations.