For thick washes, which tends to obstruct the slits of the cap, Barbet has devised the cap shown at the right in Fig. 25. This cap extends down to the plate itself, and has very narrow slits in its periphery. With such a cap as shown in Fig. 24, the bran, sediments, etc., would tend to settle upon the top of the cap, enter beneath it and through the slits. The cone-shape of the top of this cap prevents the deposit of dregs thereon and the very narrow slits oppose the entrance of bran or sediment. While, for the sake of clearness, an old form of concentrator, _G_, has been shown, the concentrator, preheater for the wash, and condensers, to-day, are usually composed of bundles of tubes through which the vapors pass surrounded by water or the cool wash. These should be of bronze or copper and made without solder. The tubes should be capable of being taken out for cleaning or repairing. In many distilling apparatuses the distilling column and the rectifying column are in two parts, one beside the other. This overcomes the objection of having a very high column and also prevents the low wines, _i.e._, the weak alcoholic liquor after its first concentration, from passing into the wash as it would do with the continuous column. [Illustration: FIG. 26.--Steam Regulator.] In order that the amount of steam entering the column may be regulated, the column is usually provided with a steam regulator (Fig. 26); whose principle of operation may be easily under stood by referring to Fig. 22. It comprises an upper and a lower chamber _Z Z¥_ connected by a central tube _K_ which projects down nearly to the bottom of the lower chamber. A pipe _W_ communicates with the steam chamber _R_ of the column and enters the chamber _Z_ above the level of the water contained therein. In the upper chamber _Z¥_, is a float _X_, connected to the differential lever _T_ of a steam valve _T¥_ which controls the inlet of steam passing through pipe _S_ to the steam chest _R_. The principle of operation is very simple. When the pressure in the steam chest _R_ becomes too great, steam in the pipe _W_ and chamber _Z_ forces the water therein up in tube _K_, thus lifting the float _X_ and closing the steam entrance valve _T¥_. When the pressure of steam is low, the level of the liquid in _Z_ rises and liquid in _Z¥_ runs into _Z_, the float _X_ falls opening valve _T¥_ and allowing a greater flow of steam. As it is often desirable to change the pressure of steam in the column at various points in the operation, the best regulators are usually provided with means to that end. [Illustration: FIG. 27.--Gauge Glass for Regulatur.]