tages attendant upon logarithmic operations, such as the probability of errors in the tables, a thing of no uncommon occurrence, even in our best tables; all which circumstances tend to show that logarithms should be used only when other methods of computation do not present themselves, or when, if they do, they require much greater labour and trouble. Within these last few years, several new methods have been proposed for extracting the cube-root; some of your readers may be able to decide upon the merits of these several methods, and by making public that which is most easy and expeditious, through your Magazine, will, I dare say, do a service to many of its readers, and particularly so to Your obedient servant, GENTLEMEN'; Your very respectable correspondent Mr. B. Be van, has sent you a method of simplifying the extraction of the cube-root by logarithms, as an answer to J. T. It is all very good and very correct in its results, provided we can find tables of logarithms, whose natural numbers extend to twenty or thirty places; but I have never seen tables extending to more than four places. He has very sagaciously, but not very mathematically (inadvertently no doubt) taken the number 2875, with two ciphers annexed; for he well knew where to find the logarithm of 2875, which, with its annexed ciphers, would make its index equal to 5; but it often happens that we have a quantity which may extend to a far greater length than six places to find the root of; and unless we have tables whose natural numbers extend to such a length, we shall find that the logarithm of the four integers only on the left will make us play a very foolish game, and will by no means be "sufficiently near for practical purposes." Your numerous readers who may be acquainted with the tables of logarithms, but ignorant of the principles upon which they are constructed, may be apt to rùn into a great error, by following Mr. Bevan's method; and I throw out this remark for his consideration, with all due deference to his superior abilities. Mr. B., however, will understand, that I do not mean to say that he is altogether incorrect in the exact number he has adopted; but I say, the adoption of the two ciphers is less excusable in him than it would have been in me; and I say that it leads to crror, if we always follow his mode of treating the subject, and this from a cause already mentioned. Yours obediently, J. Y. P. S.-Will any of your correspondents inform me where I can find a set of logarithmic tables, whose natural numbers extend to 6, 8, or 10 places of integers ? J. Y. Mr. Picket will perceive, that in his answer on this subject he was anticipated by Mr. Bevan: his offer to teach J. T. gratis in logarithms, "if not already acquainted with them," at his house, Brook-street, Ratcliff, is liberal, and not the less deserving of thanks; that J. T. seems, from the reply which we now publish, to be an inquirer of a very different stamp. ENGLISH METHOD OF CASTING MEDALLIONS. Brownlow-street, Feb. 25, 1824. GENTLEMEN ;-A subscriber of Lincoln's-iun wishes to know the French method of casting medallions. Although I am ignorant of the method adopted by the French, yet I am inclined to think the English mode is quite as good; as I have both seen cast, and have myself cast medallions which I have considered in every respect equal to those cast in France. The plan we pursue in London is that of taking the mould in plaster of Paris, the fineness of the texture of which enables a mould to be drawn off in the greatest state of perfection. It need scarcely be remarked that the mould should have the moisture thoroughly eradicated prior to its being cast in. Your correspondent is perfect ly right respecting the nature of the metal. It usually consists of one-fifth antimony, and the remainder lead (it should be tea-lead). I have at present by me a small cast (the bust of Shakspeare) which I should be happy to show your correspondent. I am yours respectfully, AN OLD CASTER. METHOD OF MAKING ALUM GENTLEMEN;-As some of your correspondents might wish to employ a leisure hour in contributing to the amusement of the ladies, I beg to offer a method of making alum baskets. Form a small basket, about the size of the hand, of iron, or split wire, or split. willow; then take some cotton, such as ladies use for running into flounces; untwist it, and wind it round every limb of the basket. Boil a pound of alum in a quart of water, or in that proportion; let it boil well, stirring it all the time; when completely dissolved, pour it into a deep pan, or other convenient vessel, and suspend the basket in it to a good depth, so as that no part shall touch; let it remain perfectly at rest for twenty or twenty-four hours, and when you take it out, the alum will be found very prettily crystalized all over the basket, making a very neat chimney ornament to hold flowers, &c. The alum may be coloured pink, purple, or yellow, by boiling Brazil logwood or French berries with it. Sometimes, however, the crystals will be too large, and the basket not uniformly covered; therefore, if any of your correspondents know how to prevent this, or any better method of proceeding, they will, by communicating it, very much oblige, Gentlemen, yours, &c. &c. VECTIS. HOW TO POLISH PEBBLES, CORNELIANS, &c. Rub the pebble to a surface upon a thick piece of lead, with emery, mixed with sweet oil or water; first with coarser, then with finer, as the Furface improves; next with the dif ferent Scotch grits, proceeding as with the emeries, until all the scratches left by the emerics disap pear; this being done, provide yourself with a block of wood, well planed on one side, intended to be the uppermost, about 14 or 15 inches by 4 or 5, and as many thick; cover it with a thick coarse flannel, called fearnought; on this fasten a piece of coarse linen cloth, double at least, and upon it rub the stone, prepared for polishing, with tripoli, finely powdered, and mixed with either sweetoil or water; then rub it on soft washleather, and afterwards on the thick part of the hand, which process will bring the polish to its highest pitch. E. TO MAKE BRUNSWICK GREEN. The Brunswick green colour used in paper-hangings, and other coarse kinds of paiuting in water-colours, is prepared in any close vessel of wood or earthenware, filled half full of copper filings or clippings, on which is poured a saturated solution of sal-ammoniac, which together will form the muriate of copper, the ammonia being at the same time disengaged. In a few weeks almost the whole of the copper may be converted into oxide this being well washed, and slowly dried in the shade, is pure Brunswick Green. Three parts of muriate of ammonia, or sal-animoniać, and two of copper, yield six parts of green. TESTS FOR COLOURS. Genuine Ultra Marine loses its colour when thrown into concentrated nitrio acid. Carmine is entirely soluble in liquid ammonia. Mudder and Carmine Lakes, are completely soluble, by boiling them in concentrated solution of soda or pot-ash. Antwerp Blue should not lose its colour, when thrown into liquid chłorine. Chrome Yellow should not effervesce with nitric acid. White Lead is completely soluble in nitric acid, and the solution should re main transparent, when mingled with a solution of potash. Vermillion is totally volatalized con being-exposed to a red heat, and should not impart a red colour to spirits of (« wine when digested with it BRUSH. * DISCOVERIES AND IMPROVEMENTS. FRENCH IMPROVEMENT IN THE LOOM. We are informed that the new French system of weaving all kinds of figured goods without drawboys, by a single adjunction to a common loom, merits the attention of manufacturers. The artist can change the figures from one flower to another in fifteen minutes, and can produce twenty different patterns in as many yards of cloth; the whole is worked by one single treadle only, as well in large shawls as in narrow goods; he possesses the art of printing all kinds of yarns in different colours, in set and regular distances, smaller and longer at pleasure, which produces an astonishing effect when these yarns are manufactured into goods.-Glasgow Chronicle. CLOTH MADE BY SILK-WORMS. (From an American Paper). While our countryman, Perkins, is astonishing the world with his new steamengine, and Brewster, with his thousand spindled cotton machine, a few silkworms in Lisbon (Con.) have not been less industrious in producing a new fabric from their own silken bowels; but to how great an extent they will carry their manufacture we have no assurance. Mr. W. Bettom, of Lisbon, showed us, a few days ago, a piece of silk, a yard and a quarter in length by a quarter in width, of a beautiful yellow tinge, with a bright yellow selvage entirely around it; wove, or otherwise strongly, evenly, and handsomely connected together, with a right and wrong, or a rough and smooth glossy side, as is usual on pieces of wove silk. It was wrought on a board in his silkhouse, by about twenty-five worms, in the space of three days!! They had commenced a second piece of a rather thicker texture, and of a whiter colour, which they seem to haye left unfinished. NEW PATENTS. To Jarvis Boot, of Nottingham, lace manufacturer; for an improved apparatus to be used in the process of singeing lace and other purposes.-13th December, 1823. To Thomas Greenwood, of Gildersoun, machine maker, and Joseph Thackrach,, surgical machinist, of Leeds; for certain improvements on, or substitutes for, pattens and clogs.-27th December, 1823. To John Vallanee, of Brighton, esq.; for an improved method or methods of freezing water.-1st January, 1824. TO CORRESPONDENTS. The letter of "A. Turner" has not altered the opinion we have pronounced on Mr. Hunt's case. We agree with L. E., and shall be glad to hear from him again. His improvement of Algond's solution, however, seems rendered unnecessary, by the article of F. in our last. Communications received from J. Y. -A Constant Reader-J. S.Naythan Copcake- Pertinax - T. BillinghamTyro Philo-Mechanicus-T. B.-R. Bonushome-J. N. George LovattA. B.-J. S.-T. G.-F. R. F.-Q in a Corner-Clio-Judæus-Putty-J.B.J. G.-W. G. B. —J. O.—W. K.-and G. A. S. With our next we shall publish a Supplementary Number, containing an Engraved Title Page, Preface, aud Index to Vol. 1, and aiso numerous Answers to Inquiries, which have been standing over for want of room. END OF VOLUME I. Published every Saturday Morning, By KNIGHT and LACEY, 24, Paternoster-Row. Communications from intelligent Mechanics, and from all others who may take an interest in the diffusion of useful information on any of the subjects embraced by this work (addressed to the Editor, and post-paid to the care of the Publishers) will be thankfully received, and have every attention paid to them. It was well remarked by the great philosopher, Boyle, that if every artist would but communicate what new observations occur to him in the exercise of his trade, the advantages gained to philosophy would be incalculable. T. C. Hansard, Pater-noster-row Press. 證 INDEX. A. ABERDEEN, Mechanical Institution of, 277 Air, Ascending in; Attempts at, : Ex- Air, Foul; How to detect in Wells, 15, Almanack, Supposed, 286 Alum Baskets, How to make, 447 Annals of Philosophy, Analysis of, 389 Apple Jelly, 95 Apples, Wine from, 127 Archimedes, Burning Mirror of, 39 Art and Science, Triumphs of, 435 Autumnal Complaints, Remedies for, 110 Barber's Pole, Origin of, 95 in, 309 and Water Manikins, 286 Barron, John; Patent to, 80 Beer, Cottage; Receipt to make, 47 October; Properties of, 207 Birkbeck, Dr.; the first to unfold the Black-lead Pencil Drawings, How to fix, Blue, Antwerp, Test of, 447 -Boat for passing up Rapids, 67 plied with Wheels, 169; Adoption for Weighing Anchors, Improve- Mr. Pasley, 217, 248 Boulton, Mr.; his connection with Mr. Bourne, Joseph; Patent to, 384 Brass-work, Receipt for Cleaning and Bread, Test for the Purity of, 175 Seals; Inquiry respecting, 366 Chinese Tailors, 53 Flat Colours, 108 Notions of Lawyers, 375 Chomped Hands, Cure for, 432 Chubb's Patent Detector Lock, 193 Cingalese Jewellers, 159 Clock Wakener and Lighter, invented by Cloth, Water-proof, 55, 159 Cobbett, Wm.; Speech at the Moeung . Coblers and Shoemakers, Anecdote of, Cockroaches, How to kill, 110 Coffee, Improved Method of Making, 160 Coles' Improved Truss, 426 Combination Law, On the, 341, 370, 386, Comfort, Crumbs of, 77 |