At the top of the column are three rectifying chambers fitted with boiling pipes and traps _T_, which distribute the ascending vapor and boil out the low wines returned from the wash-heater or fore-warmer. [Illustration: FIG. 29.--Detail of Chamber, Continuous Still.] The heater consists of a shell enclosing a series of tubes extending into an upper and lower chamber. The wash or "beer," is pumped into the lower chamber of the heater, and passes upward through the tubes to the upper chamber from which is it carried by a pipe to the plate _A_ next below the rectifying plates. [Illustration: FIG. 30.--Detail of Perforated Plate _A_.] The vapor from the column passes into the middle compartment of the heater and surrounds the beer tubes. The vapors give their heat to the beer and are thus cooled, the low wines being condensed and flowing back onto the uppermost rectifying plate, while the highly vaporized portions pass out to the condenser. This is of the same general construction as the heater, the vapor being cooled and condensed to liquid by the tubes through which a constant current of cool water is passed. This enters at _U_ and passes out at _V_. These tubular condensers are particularly good as they may be easily cleaned. From the condenser the spirit passes to a discharge box _W_. A portion of the flow passes into a test tube _X_, provided with a hydrometer. A trap _Y_ and an air pipe _Z_ provide means for the escape of gas. As before stated, the form of perforations in the plates of a column through which the vapor pass upward through the beer or wash is particularly important. The steam must be thoroughly diffused through the beer, or else particles of mash are carried up, accumulate around the perforations, baking there and clogging them up. The clogging and eventual stoppage of the perforations prevent the agitation of the mash carried on the plate, and a layer of mash accumulates and bakes on the head, or plate, above. Thus the operating capacity of the still is reduced and a larger quantity and greater pressure of steam is necessary with consequent waste of fuel. [Illustration: FIG. 31.--Detail of Perforated Plate _A_.] It is necessary then that the form of perforation or trap through which the vapor ascends should be such that agitation of the beer shall be enforced in its movement across the plate, and that the steam shall be thoroughly diffused through the beer. In the Vulcan still above referred to, these results are accomplished by forming each perforation with a tongue, as shown in the fragmentary view of a plate, Figs. 30 and 31, the tongues of all the holes being directed towards the periphery of the plate. It is claimed that by this construction the steam is diverted forward and injected into the beer, throwing the beer into vigorous motion, completely diffusing the steam and accelerating the motion of the beer from the seal _C_ to the drop pipe _B_.