The heater _C_ is filled through funnel _Y_ and the mash is admitted to the still through pipe _b_ having cock _a_. The pipe _P_ extends to the upper part of the water tub _W_ and then downward to the bottom, where it again enters the still. An opening in the partition _d_ is controlled by a valve _G_ which allows liquid in the upper compartment of the still to flow into the lower. Spent mash may be drawn off through _c_ and the height of the water in tub _W_ be regulated by pipe _Z_. [Illustration: FIG. 13.--Compound Still.] The operation of this still is similar to Dorn's still. Mash is put into _C_ and a quantity of it is let into the upper compartment of the still and into the lower compartment by valve _G_. This valve is closed and the fire started. The vapors pass upward through _t_. If they are quite highly vaporized they pass onward up _P_, are condensed in their passage through the cool water tub and return as liquid to the upper compartment where they are further heated. The liquid in the upper compartment is thus constantly enriched and the vapor therefrom passes out through pipe _T_ into condensing coils _f_ where it is condensed into spirit and passes off by _F_. The funnel tube _Y_ acts also as a means of warning the attendant as to the condition of the mash. If it is too high in level and the pressure of vapor in the heater _C_ too great, liquid will be forced out of _Y_; if on the contrary, the mash sinks below the level of the pipe then vapor will escape and the heater needs refilling. [Illustration: FIG. 14.--Compound Direct Fire Still.] Fig. 14 shows a simple form of compound direct fire still as manufactured by the Geo. L. Squier Mfg. Co., of Buffalo, N. Y. Cellier-Blumenthal carrying this principle further devised an apparatus which has become the basis of all subsequent improvements; indeed, every successive invention has differed from this arrangement merely in detail, the general principles being in every case the same. The chief defect in the simple stills was that they were intermittent that is required the operations to be suspended when they were recharged, while that of Cellier-Blumenthal is continuous; that is to say, the liquid for distillation is introduced at one end of the arrangement, and the alcoholic products are received continuously, and of a constant degree of concentration, at the other. The saving of time and fuel resulting from the use of his still is enormous. In the case of the simple stills, the fuel consumed amounted to a weight nearly three times that of the spirit yielded by it; whereas, the Cellier-Blumenthal apparatus reduces the amount to one-quarter of the weight of alcohol produced. Fig. 15 shows the whole arrangement, and Figs. 16 to 17 represent different parts of it in detail. [Illustration: FIG. 15.--Cellier-Blumenthal Still.]