Between these simple beginnings and the elaborate plants of big distilleries there is a wide range, so wide that it is impossible within the limits of this book to go into detail. The makers of distilling apparatus furnish all grades of stills and to those contemplating erecting a plant it is suggested that their best course is to communicate with such manufacturers, giving the circumstances of the case, the particular product to be worked and the capacity desired. The object of this book is to give an understanding of the processes of distillation and of this chapter to give a general idea of the arrangement of a number of typical distilling plants, suitable for various kinds of work. That the simple, direct-heated pot still such as referred to above, used for fifteen hundred years and over, is still used is largely due to the simplicity of its construction and operation, but its capacity is small, and its operating expense relatively heavy. It is still used for making liquors, but for industrial purposes it has been entirely superceded by concentrating and rectifying stills. A simple form of the latter is found in the still shown in Fig. 11 and in the distilling apparatus of Adam (Fig. 9). Originally all stills were heated by direct contact with fire. This was open to a serious objection, namely, that the mash if thick was liable to be scorched. Stirring devices were used by Pistorious but these required constant attention. As a consequence, direct firing gave place to heating by steam, by which not only was scorching of the wash avoided but much greater certainty of operation was attained. The steam may be used to simply heat the boiler, thus taking the place of the direct heat of the fire, but it is far better in every way to admit the steam directly to the mash as in the Coffey still, Fig. 18, and all modern stills. It is possible to apply this principle to all compound stills, but the best results with greatest economy of fuel are, of course, gotten from the plate or column stills especially constructed for steam. In order to get the best results it is necessary that the entry of steam be regulated so that there may be absolute uniformity of flow. A convenient form of regulator is that invented by Savalle, and described on page 70, hut there are a number of other forms on the market each one having its special advantages. It will be seen then that while the simple pot still, fire-heated, may be used, the practical plant for the fermentation of industrial alcohol should have a modern continuous still and rectifier and a boiler for generating the necessary steam for it and for the operations of mashing and fermenting. THE FERMENTING ROOM.