The coils of the cooling worm are made octangular: the worm itself is made flat, and of considerable breadth; a transverse section of it is exhibited in the separate figure k, which shows it to be in the form of a parallelogram, whose longest sides are four inches, and its shortest half an inch wide. This octangular worm, after making six complete turns, assumes a circular shape, and diverges off to pass through the side of the tub; at its end outside the tub, which is made a little tapering, is fitted, and is to be occasionally applied, a crane-necked pipe l, which pipe may be elevated or depressed at pleasure, for the purpose of keeping three or more of the coils of the worm full of liquid. This crane-necked pipe is intended to be applied in hot weather, or hot climates, to cool the spirits more effectually, and prevent their evaporation, by subjecting the same in a greater degree to the effect of the cold water in the worm tub. An additional apparatus, to be used in hot climates, of undoubted utility, is likewise recommended by the patentee, and claimed by him as his invention.
It consists of another pipe m, into which the discharging end of the crane-necked pipe is made to enter; and which pipe, after passing the end of the trough n, is made of a very bread, flat shape, and running the whole length of the trough (which may be of any extent); it is then to return by a very slight descent, so as to run back very gently into the funnel of the pipe which conveys it into the receiver. The trough n is to be filled with Glauber's salts and nitre, or any saline mixture capable of producing intense cold, for the more effectual cooling of the spirit. The trough may be placed upon wheels and axles, for the convenience of bringing it to and conveying it from its required situation.
Distillation is very commonly practised in India; and although the apparatus is of the most simple (not to say rude) description, the products are generally of such excellent quality as to render the process deserving of the consideration of the British manufacturer to discover the cause. The still commonly used by the natives of Ceylon is represented in the above cut. It is constructed wholly of earthenware, excepting the tube of communication between the alembic and the refrigeratory, which is of bamboo, b is the body (or boiler) of the still; a is the capital, luted with clay to b; c is the bamboo tube, which conducts the vapour into the receiver d, where it is condensed by being immersed in the vessel of cold water e. It is with this rude apparatus, (according to Dr. Davy,) that the Singalese distil in the open air that fine spirit arrack, which is obtained from toddy, the fermented juice of the cocoa nut.
The editor of the present work, having a few years back had his attention called to the state of the arts and manufactures in Ceylon, and of the implements connected therewith, with a view to the improvement of the same, published a series of papers on the subject, in a periodical work which he at that time conducted, suggesting such alterations as seemed to him practicable with the simple means and resources at the disposal of the natives; and the Ceylonese still, just described, appearing to him to possess considerable merit, he proposed the following modification of it, in which, whilst the best features of it are retained, it is rendered in some respects more efficient, fuel and labour are economized, and by a simple method of combining several small stills, an apparatus is constructed adapted to operations on a more extended scale, a a a a are the heads of a series of earthen boilers, of the kind described above, but instead of being exposed to the air, they are set in a close furnace b b, built of clay, or of the same materials with which their pottery is formed.
This furnace is proposed to be built in a circular form, to any convenient extent, so as to surround wholly or partially the other parts of the apparatus; it is for this reason shown in the drawing as broken away, after being extended sufficiently to allow of five vessels being fixed therein. The curved figure of the furnace is given to it chiefly with the view of affording a convenient means of connecting the bamboo tubes which conduct all the vapours from the several stills into the cylinder d. This cylinder is fixed firmly in a closed vessel e, which serves both as a recipient for the condensed liquid, and as an enlarged chamber for the vapours. On one side of the cylinder d there is an oblong aperture, made longitudinally for the egression of the vapours, which is covered by a light piston, so that when the vapours have attained but a very little more elastic force than is sufficient to overcome the pressure of the atmosphere, this piston is lifted, which uncovers the aperture to a certain extent, and permits the vapours to pass through a large bamboo tube of communication into a thin metal refrigerating box l; this metal box is supported by a strong tube o, fixed into the close recipient p, the tube being open to both.
On the top of the cylinder is fixed a vertical standard, the upper end of which becomes the fulcrum to a lever crank i. To one end of this crank is jointed a rod or stout wire, which connects it to the handle of the water valve k; the other arm of the crank lever passes between antifriction rollers on the piston rod h. It will be manifest by this arrangement, that in exact proportion to the volume of vapour that escapes from the cylinder, will the precise quantity of water necessary to condense it be showered down upon the refrigeratory; and this is done uniformly and according to circumstances, without any attention on the part of the distiller. By the elevation and depression of the piston rod It also, the long arm r of the lever crank may, by means of a cord s, be made to open a sliding door or damper to the furnace, by an arrangement for this purpose omitted in the rough sketch. As it is objectionable to leave the still-heads exposed to the air, by which a portion of the vapour becomes condensed and runs back into the still, it is proposed to enclose them with a cap of wood or pottery, like that delineated in the margin above, which will envelope them in a heated atmosphere.
To prevent the escape of the heat through the clay walls of the furnace, they are made double, with a stratum of charcoal between, as represented in the annexed sectional view, in which a a represents the strata of charcoal imbedded in the surrounding clay; b the boiler; c the head, luted to the boiler enclosed in the box d, through an aperture in which the neck e passes, that conducts the vapour to the cylinder; the cavities round the boiler f f are for the heated air, and g the hearth, on which the wood is thrown at one end of the furnace.