=The Steamer.= One of the earliest forms of steamer was that of Hallefreund devised in 1871, and adapted for working on a large scale. A modified form of the apparatus known as Bohn's steamer and masher is illustrated in Fig. 45. This comprises a steaming cylinder _A_, having a securely closed opening _D_ for the introduction of the potatoes. Centrally through the cylinder passes a hollow shaft _B_, which is rotated by the power pulley _K_. Hollow arms _b_ project radially from the shaft _B_. These act as mixers of the mash and as coolers. The shaft _B_ at one end is connected to a cold water supply pipe _M_ as by a coupling _C_, the supply pipe being provided with a cock. _E_ designates a discharge opening for the mash. A pipe _F_ provides for the entrance of steam into the cylinder. _G_ is a pipe through which malt is put in to be mixed with the pulp. _L_ is a steam gauge and _J_ a safety valve. _H_ designates a water pipe. For the relation of the steamer to other apparatus, see Fig. 1. In operation the potatoes are placed in the cylinder _A_ and submitted to the action of steam at about 46 lbs. to the square inch, and at a temperature of from 266∞ F. to 275∞ F. When disintegrated, the steam is blown off, and the potatoes crushed by rotating the stirring shaft. As the pulp must be reduced from 275∞ F. to 149∞ F., the mashing temperature, cold water is forced into the stirrer which chills the blades and quickly cools the mass. In the vacuum mash cooker shown in Fig. 1, the steaming cylinder is partly filled with hot water at 140∞ F. to 150∞ F. The potatoes to be mashed are fed into the cylinder whole. The steamer is then closed and steam admitted while the mash is stirred until a pressure of 65 pounds is reached, when the dissolution of the starch is complete. The steam is then exhausted and the temperature reduced to 212∞ F. To reduce this temperature to the proper saccharifying point of 145∞ F., the hot air is exhausted. Barley malt meal in the proportion of 6 to 10 per cent. is used. This has been previously mixed with cold water in the small grain masher. The malt is admitted to the cylinder and thoroughly mixed with the potato, when the mixture is withdrawn into a drop tub, where it is still further stirred. It is then cooled as described on page 15 and then fermented. While the crushed potatoes are being cooled and stirred, a mixture of green malt with water is prepared in an adjacent vat, and when the pulp in the cylinder has been reduced to 149∞ F. the malt mixture is introduced into the cylinder through the pipe _G_, and thoroughly mixed with the crushed potatoes. The mass is now left to saccharify; the stirrer being operated at intervals throughout this period. This machine might be readily modified so that the steam should enter through the stirrers, by tubes attached to the arms, then the steam may be shut off and cold water sent into the arms themselves to cool the mash.