the solutions of salt and sugar, necessary in the manufacture of those articles; for generating steam for motive engines; for the acetifying of vinegar; and for the manufacture of verdigris.

"First, as to distillation; a, fig. 1, is a tall cylindrical vessel containing the fermented wash to be distilled, which vessel is supposed to be regularly supplied by means of a pipe from the brewhouse. By turning the cock in the pipe b, the wash flows upon the exterior surface of the conical evaporator c; the liquid is first discharged into a small basin fixed round the cone near to its apex; which basin, having numerous minute perforations at the bottom, distributes the liquid equally over the whole surface of the evaporator in the thinnest possible stratum. The quantity of wash allowed to flow, may of course be regulated by the turning of the cock, and its uniform distribution may be assisted, if necessary, by spreading thin linen cloth, or wire gauze, (each has its peculiar advantages) over the surface of the cone, which would quickly absorb, or prevent the liquid running off too freely; i. e. before the required degree of vaporization was accomplished.

The evaporating cone, I propose to be made of thin copper, and to be heated in that way which may be found the most convenient and economical; the means depending upou the circumstances of its locality. In the drawing, I have broken away the front of the cone, to show that it is hollow, and equally adapted to the application of heat to its surface, whether by direct fire, by heated air, or by steam. If by direct fire, a very small stove may be placed on the centre of its circular floor, and immediately over it, an aperture, or tube, for the supply of atmospheric air; the flue should descend, or an aperture should be made at the lower part of the side of the cone, in order that the upper part may be constantly preserved at the necessary temperature; the heated air having no tendency to descend and to pass off by the flue, nearly the whole of its caloric, would be usefully applied. If the tube which supplies the air were to pass through the brewhouse furnace, there would probably be no occasion for employing the stove before mentioned, when the furnace was in use, as hot air of sufficient intensity would occupy the upper part of the cone; the heat requisite being below that of boiling water. Should steam heat be desired, which is preferable on account of its easy regulation, it might be brought on from the brewhouse copper, by means similar to those described, and the condensed portion might run back into the boiler through the same pipe which conveyed the steam. whatever may be the medium by which the heat is introduced, I apprehend that its application by this contrivance, will be more economical and effective for the purpose of vaporization, than any which has preceded it.

But

I propose that the evaporating cone, be not heated to a higher temperature than 180° Faht.; to ascertain which, I would have a thermometer fixed in a convenient situation; and I would regulate the temperature by the turning of a cock, which would admit a greater or less quantity of steam. At the temperature mentioned, but a very small portion of aqueous vapour would be raised along with the

spirituous; and by that means I would also separate the spirit, at the commencement of the process, from those matters which usually contaminate spirits of home manufacture. That portion of the wash that, owing to the low heat, escapes evaporation, (which would consist chiefly of water and extractive matter,) will run off at the bottom of the cone, along a circular gutter, and from thence pass out by an aperture or pipe, as at e; while the more spirituous, rises between the inner and outer cone ff, enters the neck g, and from thence procoeding through the spiral worm shown in the wash vat a,* is received into the recipient h, partly in the form of vapour, and partly in the liquid state.

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This

The more volatile portion of the vapour passes onward through the open tube i, into the great refrigeratory . This is a large cylindrical vessel or vat, with a strong false bottom at 1; on this rests a metallic apparatus, consisting of a great number of small tubes tt, open at each end, and fixed parallel to each other in a vertical position; their lower ends being soldered into a metallic bottom, and passing through it: the upper ends of the tubes, in like manner, are soldered and pass through the concave plate in the chamber m. metallic apparatus being luted or soldered to the false bottom round its lower edge, all the vat above the false bottom is kept filled with cold water by a service pipe inserted at the lower part. The vapour therefore passing through perforations in the false botton, rises up the numerous small metal tubes, by which it is separated into very narrow columns (into wires of vapour, if the term may be allowed,) and being thus exposed in metallic conductors to the powerful influence of the mass of surrounding cold water, its caloric will be very rapidly abstracted; the condensed liquid, which then runs back down the pipes, meets with the rising vapour in its progress, and by that means condenses a further portion at a higher temperature than would otherwise have been accomplished. I mention this circumstance here, to explain the reason, why I allow the vapour to proceed upwards, instead of forcing it downwards, according to the ordinary practice, which alteration I think may be deemed an improvement. By these arrangements I expect that very little vapour will reach the upper chamber m, if the temperature of the water is not allowed to get above 80°; but if the supply of cold water should be insufficient for the purpose, the vapour must of course proceed from the tube n to another refrigeratory.

"It is deserving of notice, that in this apparatus the process may be continued without stopping, as long as the fermented wash is sup

• The passing of the vapour through the vat a, has three advantages; the first, that of condensing a portion of the spirituous vapour; the second, the raising the temperature of the wash to about 160 degrees, so that it is discharged upon the still already in a heated state, and a very slight increase of temperature is suffi cient to separate all its alcoholic constituents: the third results from the second; as the temperature will thus be raised to 160°, a very strong spirituous vapour will slowly collect in the upper part of the vat a, which may be conducted off by the tube o, mto a separate recipient or refrigeratory, as the spirits thus pro duced will be of superior parity.

plied from the brewhouse, which is not the case with any other still. If it be required at any time to have access to the inner cone, a door made on the outer one (which should be kept luted during distillation,) will answer this purpose effectually.

"I have proposed to cover the inner cone with cloth of some kind; this might be laid on in longitudinal sections, each piece forming an isosceles triangle, and stretched out to that figure by a stiff wire, which should also be curved to fit the convexity of the cone. These pieces might then be readily taken out at any time, and the deposit washed away, or others put in their places. If these triangular cloths were made of metallic gauze, it is probable the evaporation would be much expedited. It would, however, be desirable to do without these appendages, entirely; if the surface of the cone was slightly indented or grooved, the liquid might then be distributed evenly without the cloth, and be detained a sufficient time to complete the operations. There are several obvious modes of treating these points, which it would be tedious to describe, or to read. I shall, therefore, conclude the subject, as regards distillation, by explaining the use of the apparatus attached to the winch p. This winch is fixed upon the axis of a small bevelled pinion; this pinion turns a bevelled wheel q, which revolves round the upper part of the cone (against friction rollers,) and carries with it two long bars rr, the edges of which scrape or brush against the surface of the cone, to clear it of sediment or incrustations, which will then fall to the bottom: the bars rr are connected by a ring at s. Such an apparatus will be useful in the distillation of liquids that contain much extractive matter.

"Having concluded my observations upon the apparatus as a still, I proceed to notice its application to other purposes. For evaporation simply, the refrigeratory part of the apparatus is of course to be entirely dispensed with. In evaporating brine for obtaining salt, the double cones appear to me to be infinitely preferable to the immense open pans generally used in Cheshire and other parts. The salt makers proceed upon the improved plan of exposing an extended surface; accordingly, each of their pans measures several hundred superficial feet, and they are filled with the briny liquid to the depth of a foot or more. Now if the principle of extension of surface be right, which appears to be acknowledged by all scientific men, the greatest extent to which the principle can be carried must have the preference. Again, it is a most erroneous plan to expose the evaporating surface to the air, which of itself produces a considerable condensation, causing a portion of the vapour to fall down again into the pans, in the state of fine rain. Reason tells us that this must be the case: but the French have done more for us; they proved, many years ago, by direct experiment, that evaporation does not proceed so rapidly in uncovered vessels, as in those which are covered, with a pipe to convey off the steam. To complete the apparatus for the preparation of salt, the scrapers rr, already described, would be found particularly efficient and convenient.

In the concentration of vegetable solutions generally, but in particular that of sugar, my evaporating cones appear to me to have a

decided preference over the open pans, commonly used in the West Indies and elsewhere. In the successive evaporations which the sirop undergoes, previous to the crystallizing process, the liquid is ladled from one vessel to another: in my apparatus this trouble is entirely dispensed with, the liquid continually running off, of itself. In the consumption of fuel, I conceive, there would be a considerable saving, as the caloric is applied with greater effect, and more economically, than by the usual furnaces; and the condensation of the vapour back into the sirop is prevented, by my external cone or covering, which excludes the evaporating surfaces from the air. My scrapers would also be applied very effectually in removing any incrustations that might form on the surface of the inner cone. The cones might be made of any magnitude, or several might be arranged a little above one another.

For the generation of steam for motive engines, I see no difficulty in its application; for that purpose, the rapid and economical production of vapour in strong vessels appears to me all that is required. I need not repeat that my extended surface and mode of applying heat would produce vapour with great rapidity; and it is obvious that the conical form offers great strength. For low pressure steam, a very thin internal cone would do; and for high pressure, a very thick one would not be necessary; as the expansive force would be exerted in that direction where the vessel was strongest: the exterior cone should however be of greater strength than the interior one, yet of a less substance than boilers in ordinary use; and it would be attended with this further advantage, that in case of the exterior cone bursting, very little damage would result; there would be no hot water to scald, nor any masonry to be blown up, or building destroyed in consequence.

In the preparation of VINEGAR, it is a commonly received opinion, and I presume a correct one, that the acid property of the liquid is derived from its absorption of oxygen; the operation usually consists in exposing the liquid under fermentation, in open, or imperfectly closed, vessels, to the atmosphere. Now it has been found, that the oftener the surfaces of the liquid are changed, by agitation, or by Jadling or pumping it out of one vessel into another, the sooner the vinegar is formed. The acidifying principle being thus obtained, it appears to me to follow, that that apparatus must be the best for the purpose, by which the most extended surface of liquid can be conveniently exposed to the influence of the atmosphere; accordingly I venture to propose my cones, before described, for this purpose also, but under certain modifications. First, I would have made a series of cones (of the cheapest materials) and of such relative dimensions, that they may be enclosed concentrically one within another, a few inches apart: the liquid in the thinnest possible strata, might then be allowed to flow over them, by similar means to that described in the first part of my letter. The effect of this arrangement would I think be a very rapid absorption of oxygen, or in other words, the speedy forming of the vinegar. By the plan described, I have supposed the cones to be open at top and bottom, for the air to circulate between them. It might possibly be an improvement to let all these cones

terminate or open into one common tube; the air in which tube might be exhausted, by any convenient means, so as to increase the draft. An obvious and an inexpensive mode of producing this effect would be to supply the furnace with air for the combustion, from this tube, by which means a rapid current of air between the cones would be promoted. In vinegar manufactories a large furnace is almost always employed, whether in distilling the acid from wood, or in making a solution of malt.

VERDIGRIS, as is well known, is a combination of the acetic acid with the oxide of copper: it is usually prepared by frequently wetting the surfaces of copper plates with vinegar, by various media, and when the copper becomes sufficiently coated with the green oxide, it is scraped off, and put into bags for sale. This operation is usually performed by removing the copper plates, (which are about 12 inches square,) from the racks in which they are laid, and the plates are, one by one, scraped with an instrument made for the purpose. The copper plates used are generally very light, weighing about 16 ounces to the superficial foot; I would use copper of much greater thickness, in constructing my cones, and place several of them concentrically one within the other; each of the cones should be provided with a pair of scrapers, and the bevelled wheel and pinion before mentioned, so that I might act upon them all by the turning round of one spindle; thus the verdigris, covering several very extended surfaces, might be scraped off in a few seconds. The cones would last a considerable time, as the metallic portion of verdigris is but a small component part of it.

ENGLISH PATENTS.

Account and description of Evans's patent distilling apparatus.

WE shall introduce our description of Mr. Evans's New Apparatus, by which he proposes to remedy the defects of the old system, by inserting some observations made upon it, by the intelligent Editor of the Monthly Magazine, which appeared in July last; the invention is there announced in the following terms.

"Mr. Evans has constructed the model of a still, upon a new principle, which, if it answer on a large scale, will altogether supersede the old alembic. The theory of the machine is such, that it may, without hesitation, be pronounced the most decided improvement hitherto effected; for, if we mistake not, the still at present in use, remains in principle precisely the same, through the operation of the excise laws, that it was a century ago. Whatever improvements have been attempted, apply only to the rectification, while the first formation of the spirit is conducted in the same rude manner as in the infancy of science. We forbear entering into a more particular description, until the design be carried into execution upon a large scale. We should be extremely sorry, by premature publicity, to afford the continental distillers an opportunity of maintaining the superiority they have hitherto enjoyed, and we feel convinced, that