=Cooling the Mash.= Saccharification takes place at a temperature above 122∞ F., but the proper fermenting temperature is only about 63∞ F. to 68∞ F., and hence some means must be adopted for cooling the hot mash to this temperature and for so cooling it in a relatively short time. [Illustration: FIG. 3.--Mash Cooler, Air System.] =Cooling= may be accomplished by submitting the mash to currents of air; to contact with cold water coils or by the use of ice. One of the simplest coolers of the first class is shown in Fig. 3. This consists of a shallow panlike tank A having means for introducing and drawing off the mash. Rotating in the center of the tank is a vertical shaft _C_ carrying radiating stirrer arms _B_. Braces _M_ extend to the middle of these arms and the arms carry a number of blades or paddles _b_, which extend down into the mash. Above the arms, mounted loosely on the same shaft, but rotating in the opposite direction, are fans _H_ supported by arms _J_ which create air currents over the agitated mash. These fans move at a much faster rate than the stirrers _B_. A simple form of driving gear is shown. The main shaft _C_ is rotated by a large bevel gear _D_, meshing with a small pinion _E_ on the end of a driving shaft _F_, which is driven by a belt. This shaft also carries a bevel gear _L_, which meshes with a bevel gear _K_ mounted on a sleeve. This sleeve surrounds and rotates freely on the central shaft _C_, being supported at its lower end in ball bearings _m m_, mounted on the shaft. This combination gives opposite rotation to the faces and stirrer arms and at different speeds. The driving mechanism can be of course varied. Another simple method of air cooling would be to let the mash run down a series of enclosed steps or chutes, the casing being kept cool by an air blast. Mashes may be even cooled by mere stirring by paddles, but this takes a long time and much labor. The preparatory mash vats used to-day are almost all provided with stirrers formed of hollow blades capable of a rapid stirring movement through the mash. Through the hollow blades cold water is forced. Mash vats of this kind should have the following qualities. They should be strongly built, particularly as regards the stirrers so as to be used with thick mashes. They should thoroughly and uniformly stir and mix the mash and they should be capable of cooling the mash within an hour, and should be so constructed as to be easily cleaned. By using coils of pipe which may be inserted or withdrawn from the mash tub, and through which cold water is forced, the mash may be effectively cooled, but the best plan for quick cooling is to bring a comparatively thin layer of the mash in contact with the coils. This may be conveniently done by using a system of comparatively large water pipes enclosing small pipes for the passage of the mash. [Illustration: FIG. 4.--Mash Cooler, Water System.]