transparent, and ready for boiling. The liquor is, as required, drawn off into the measure which supplies the vacuum pans, and rapidly boiled to its proper consistency, at 150° to 175° Fahrenheit, taken by an instrument, termed a proof-stick, discharged into the heater, and by the time they are full, which will be in three skippings, the whole arrives at 180°, the granulating heat, and, being slightly stirred, is ready to be immediately removed into the hogsheads in curing-house, where, in one-fourth of the time necessary in the old method, it delivers itself of its natural portion of molasses by precipitation, which, accelerated by having the curing-house heated by steam-pipes, and then ready for shipment. The molasses thus drained is of the first quality, for whatever purpose it may be applied. This closes the process. * USEFUL DRAWING INSTRUMENT. Chancery Lane, August 18, 1829. SIR,-In making mechanical drawings of the actual size of machines, or in reducing them to another scale on paper from their true measurement, the use of a two-foot rule is a great convenience, and the necessity of having recourse to many instruments, I have often found to be as great an inconvenience. To reduce their number, I made a slight addition to the common rule, by which I preserve the full use of it, (and its scales) and have besides a good square, a bevil and a pair of calippers; a combination that embraces nearly all that is essential, and enables a draftsman to take, and lay down, his measurements with great facility and dispatch. a and b represent the two limbs of the rule; to the extremity of the limb is glued and rivetted the cross piece c, which is only rather more than half the usual thickness, or about three-eighths of an inch; the limb a is fastened in a similar manner to another piece exactly * "Or remove every boiling, in which ease the heaters may be considerably lessened in depth, and give more surface and despatch. corresponding with c at the back of it, and so as to shut against each other, as a two-foot rule does, when not fixed. When the rule is closed, it forms a perfect T drawing square, screws to measure with, and lay down any thing to the real dimensions, or to a reduced size by the scales on the rule. By opening the rule, you can measure and draw lines to its full extent of two feet, and, if there is a slide to the rule, two measures may be taken, and laid down together, which is a great convenience and preventive of mistakes being made. The cross ends c, when inclined to each other, as in opening the instrument, serve to take some angles, and the broad joint at the other end of the rule is useful in taking others. And it is evident that the extremities of the cross pieces may be brought to embrace and measure the diameters of round bodies, all the purposes of a large pair of callipers are answered thereby. In short, I find this trifling contrivance of an idle hour so useful, that L could spin you a long yarn in descanting upon its merits, but as all your readers are not draftsmen, (though all draftsmen are, or ought to be), I will here close my letter by simply recommending my instrument to the use of all whom it may concern. I remain, your constant reader, THEOPHILUS LINDSAY, M. D.* A NEW MODE OF HEATING APARTMENTS. 7 SIR, THE paper which I had the honour of addressing to you on the subject of heating apartments, and which appeared in the Number for August (Part 25), page 23, having, as I observe from your notices to Correspondents, been illustrated by drawings made from memory, in consequence of the engraver having mislaid the originals, I beg your attention to the accompanying sketches: First, because the figures 10, 11, 12, and 13, given in plate 2, of Part 25, do not agree with the printed references to the engraving, in the description, where they run in the order of figs. 1, 2, 3, 4, 5 and secondly, because the figs 10 to 13 are quite incorrect, and represent an apparatus which it would be impossible to manufacture. : The annexed diagrams (with the references to figures 1 to 5, on page 24 of the Number before alluded to) will fully explain the nature of this heating apparatus. The following is a memorandum of experiments made in February 1828, with one of these air-heaters, formed of copper. At Mr. G.'s the room door shut during the whole time. 1. Temperature before using the apparatus, 54°. 2. Do.... half an hour after using ditto, 62°. .... 3. . Do.... in about one hour, on holding a chemical thermometer within the tube, (Fig. 1. h.), without touching the metal with the bulb; the mercury rose to 254°. * Quere. Do the initials M. D. stand for Medical Doctor, or for Mechanical Draftsman ? 4. A thin slice of beef, on a small plate, placed within the hood, was completely cooked in thirty minutes. At Mr. G.'s-11th February. 1. Temperature of the room, 54°. 2. In the course of an hour the temperature was between 62° and 64°. 3. The bulb of a chemical thermometer being held close to the edge of the additional plate, the mercury, in the space of one minute, showed 160°; and, in three minutes, it indicated 160°, 4. A thermometer, about two feet above the edge of the additional plate, and in the stream of hot air issuing from under it, rose to 74°. TRANSACTIONS OF THE SOCIETY OF ARTS, &c. THE annual volume of this Society made its appearance so much later than usual, that we were unable to notice its contents previous to our last number, which contained descriptions of two of the inventions that had received the Society's premiums. We now propose to give a summary account of the whole of the contents, reserving to a future opportunity, the enlarging upon any of the subjects it embraces. PLANTING FOREST TREES. THE large gold medal was voted to Lord Newborough, for having planted 3,738,000 of forest-trees, of which a fair proportion are oak, to stand for heavy timber. These plantations are situated in Caernarvonshire and Denbighshire; for the most part, on mountainous, or other ground, not adapted for more valuable crops. From the remarks contained in the margin of the planter's book, the following conclusions may be drawn : That exposure to the prevailing sea winds, on the western coast, is highly injurious to young plantations; that, if a very dry summer succeeds the autumn and spring planting, a considerable proportion of the young trees, especially of the pinus genus, will perish, although such dry season will probably be by no means injurious to trees a few years old; that, although plantations will rise tolerably well on land imperfectly drained, other circumstances not being unfavourable, yet it is highly detrimental to them when exposure to the sea wind is superadded; that plantations, in other respects favourably situated, are injured by grasses and weeds over-topping the young plants, and, that many perish when this circumstance is combined with imperfectly drained soil. A NEW ESCULENT VEGETABLE. THE Silver Ceres Medal was presented to Joseph Houlton, Esq. of Lisson Grove, for the introduction to public notice of a new esculent vegetable. The stachis palustris, or March-all-heal, is a plant not unfrequently occurring on the sides of ditches, or moist rich cornfields; it increases rapidly by creeping roots, and forms on these during the summer, a number of thick, half-tuberous buds from which the stems of the next year are to arise. From the end of autumn to the close of winter, these tuberous buds abound in a mild, somewhat sweetish, farinaceous matter, fit for domestic use. The plants and roots are figured in Curtis's Flora Londinensis; but Mr. Houlton has the credit of having first suggested its use as an esculent vegetable, and of having made some experiments in the way of cultivating it, he proposes to call it Panace. The roots of this plant taken up in December and January, are from six to ten inches in length, and, when boiled, are similar to asparagus in flavour; they are very tender, having no hard fibres, and VOL. IV.--No. 74. 1ST SEPTEMBER, 1829. H require boiling but from twelve to fifteen minutes to render them fit for the table; in the raw state, they are very brittle, and free from any unpleasant flavour. The cultivation of this plant is very simple, and attended with comparatively no expense, and it produces plentifully being indigenous, it is easily obtained. In the month of March, the roots should be taken up, and divided into portions, each containing two or three joints. These should be planted at not less than twelve inches from the surface, in a light, rich soil, and in a moist situation. Mr. Houlten is of opinion that the size of the roots might be considerably increased by careful cultivation. It is probable, that many situations, which now produce nothing but weedy herbage of the coarsest kind, may be profitably cropped with panace. APPARATUS FOR INSTANTANEOUS LIGHT. THE Silver Isis Medal was voted to Mr. George Jackson, of No. 30, Church Street, Spitalfields, for his improved apparatus for obtaining instantaneous light. The singular fact that platina, in a state of very minute division, is capable of becoming red hot when exposed to a stream of hydrogen gas, and then of inflaming the gas itself; was first discovered by Dobereiner. The construction of an apparatus whereby this property of platina is applied to the purpose of lighting. a taper is due to Gay Lussac. The modifications now introduced by Mr. Jackson, render the machine more simple, and of greatly reduced cost in the manufacture. Mr. Jackson thus describes its construction: "The instrument which I have the honour of laying before the Society, consists of an inverted syphon, made of stout glass tube, about half an inch outside diameter, having a ball, about two inches and a quarter diameter blown on each leg. The bend of the syphon is cemented into a wooden foot, loaded with lead, and the ball on the longer leg stands about six inches, measuring from centre to centre, above that on the shorter one. The tube extends about an inch above each ball. That from the upper one is simply covered with a loose brass cap, more for ornament than use. On that which rises from the lower ball, a brass cap is cemented, into the top of which a brass plug is ground, with a hole drilled across it, met by another drilled up the centre, so as to form a stop-cock, A jet with a fine orifice is screwed into the side of the cap, so as to communicate with the lower ball through holes in the plug, when the latter is turned; and just below the jet an arm projects, which carries a short piece of brass, tube, lying horizontally, that serves to support the platinum, and protect it from accidental displacement. The end of a thin platinum wire is formed into a small helix of two or three turns, by bending it round a wire or glass rod, and is covered with moist ammonia-muriate of platinum. It is then heated to redness in the flame of a spirit-lamp, again coated with the ammonia-muriate, and again heated, so as to form a platinum sponge, from the size of a pepper corn to that of a pea. The wire is then attached to a ring, |