because it saves the operator the necessity of shifting the different parts of the microscope, when he desires to study the same object under different degrees of magnitude.-Athenæum. PAINTING MACHINE. M. LEIPMANN, of Berlin, has invented a machine for copying paintings in oil with perfect exactness. This discovery is stated to be the result of ten years incessant study; M. Leipmann having been a regular attendant at the museum at Berlin, where he selected a portrait by Rembrandt as the object of his experiment. Fixing single features and parts of this picture in his memory, by hours of daily and incessant observation, he contrived to reproduce them at home, with perfect fidelity, and by the aid of a machine, in what manner is not known. The discovery, however, is so complete, that he has produced, in the presence of the directors of the museum, 110 copies of the painting in question. These copies are said to be perfect, and to retain the most delicate shades of the original picture, confessedly one of the most difficult to copy in the usual way. The price of the copies is but a louis d'or each. - Foreign Quarterly Review. NEW WEAVING-BAR FOR ENGRAVERS. MR. E. SANG, of Edinburgh, has invented a weaving bar for engravers' ruling machines; the chief novelty of which is the substitution of a cylindric weaving-bar, easily removable, for the usual flat one, by the turning of which may be produced changes in the pattern, and a combination of levers for altering the depths of the undulations. Trans. So. Arts, Scotland. ENGRAVING ON MARBLE. MR. C. PAGE, of Pimlico, has discovered an improved means of engraving on marble, by covering the surface with a coat of cement before the chisel is used. The cement effectually prevents the marble from chipping, and when the coating is removed the letters remain as perfect as if cut in copper.-Civil Engineer and Architect's Journal. THE EVER-FOINTED PENCIL. An improvement has been made on that useful article, " the everlasting pencil," that will recommend it again to many who have disused it, owing to the disadvantages remedied by Mr. Riddle's patent. Instead of the slide working in a groove, an internal spiral action is substituted, which, by simply turning the upper part of the case, protrudes or withdraws the point. This not only obviates the inconveniences of the projecting slide to the fingers, but, by dispensing with the slit that weakened the tube, strengthens the case, and preserves its external beauty, that was injured by the traversing of the slide; and prevents the accumulation of dirt, that injured the movement. Mr. Riddle's spiral pencil is at once durable and elegant; in short, this handy invention is now perfected.-Spectator. SELF-ACTING EXTINGUISHER. THIS ingenious contrivance is the invention of Mr. Jones, who has named it "The Photolyphon, or self-acting extinguisher;" which being slid on to a candle at any distance, beyond which the candle is required not to burn, snuffs it out as soon as the upper part is consumed.-Spectator. WIRE-SEWN BOOTS AND SHOES. M. SELLIER, of Paris, has patented the right of using brass wire for attaching the upper leather to the welt of shoes and boots. He urges that this metallic thread allows neither moisture nor dust to enter the shoe, and farther that it does not rip. The sewing is performed with as much ease as with waxed thread, and is not more expensive. From the French; Mechanics' Magazine. PATENT ELASTIC BOOTS AND SHOES. MR. J. DOWIE, in some observations read to the Edinburgh Society of Arts, on March 15, states that he has succeeded in a valuable improvement, by making those parts immediately under, or on each side of, the principal arch of the foot, of an elastic material, composed of caoutchouc and animal skin; so manufactured as to bestow on the fabric the elasticity of the caoutchouc, while it retains the tenacity and durability of leather. The introduction of this elastic substance allows considerable changes to be made in the form of the boots and shoes, and gives the wearers the free use of their feet and ankle-joints in walking, to a much greater extent than any hitherto in use. The patent elastic boots and shoes possess the following advantages:-They are light, elastic, and durable, and admit of being made of the shape and form of the foot when at rest; while their capacity to alter their figure admits of their adaptation to the ever-varyingmotions of the foot. They may be made lighter than the ordinary kind, yet no unequal pressure is felt; indeed, support is given to the foot. They are rendered light by the absence of that weight of rigid leather, placed in the sole immediately under the arch of the foot.Abridged from Jameson's Journal. IMPROVED SHAKER. A SHAKER for a thrashing mill, on a new principle, has been invented by Mr. Sherman, of Kirkpatrick, Durham, Kircudbright. It is of the same width as the machine, and about four feet and a half long. The sides, which run from the machine outwards, are three-quarter boards, about four inches deep, with a flat bar across, at each end; to which the bottom, which is parallel rods, is nailed. The rods are five-eighths of an inch thick, five-eighths apart, and about an inch deep. The end of the shaker is attached to the machine by hinges, and the straw is thrown on it by the rake. The other end is suspended by wooden rods from a spindle of inch iron, cranked at each end-an inch and a quarter giving the shaker two inches and a half in throw. The shaker has a small bolt on each side, which runs into a hole in the rods, by which the shaker is connected with the crank. There are several holes in the rods, by which is given more or less declivity, that mostly used being one foot in three. The bolts are about one foot from the extreme end. The motion is raised from the spur-wheel by a pinion on a shaft, on which also there is a pulley, and another on the end of the crank-spindle turned with the rope over them; giving about the same motion as fanners require, the fanners being driven from the same shaft. The bottom of the rake might be taken out, and the shaker introduced, in which case room might be saved; and in many cases, the shaker might be driven by a pinion on the crank-spindle attached to the spur-wheel. Should there not be room for the shaker between the rake and fanners, a small rake, just sufficient to relieve the drum of the straw, with a little more motion, might serve. By putting a close bottom on the shaker, two or two and a half inches below the rods, the grain would run into fanners almost without hoppers. By this improvement, the shaker can be made longer, giving the straw more time, the crank can be enlarged, giving it more shake; or more motion can be given, which will shake it oftener.-Dumfries Times; abridged. NEW THRASHING MACHINES. A NEW hand-thrashing machine has been introduced into the county of Sussex, which will thrash about four quarters of wheat daily; two men turning it, and two others feeding it, and clearing the straw away. This machine, instead of diminishing manual labour, increases it, by giving employment to those labourers who cannot use the flail; and who, in wet days, could not be profitably occupied. It is very portable, and costs but a few pounds. Sussex Express. TRAVELLING PLATFORM. THE Society of Arts have rewarded the inventor of a simple and ingenious contrivance, termed " a travelling platform." It consists of two boards, twelve inches long, by four wide, strongly hinged together; the joints of the hinges are uppermost, and a groove in the centre allows a rope to pass between the boards freely when they are brought into a horizontal position. Each board is to be strapped securely to the climber's feet; a belt also passes round his waist, having attached to it a ring, through which also the rope passes. When a person thus equipped wishes to ascend the rope, he hangs by his hands, draws up his knees, keeping the hinged board in a flat position, and it slips up the rope: immediately his weight is put under the boards, the edges on the under side, (the contrary to that on which the hinge joints are placed,) collapse, and firmly clutch the rope; whilst he raises himself, his weight acting on the lever formed by the width of the board, its thickness, and the hinge joints. A workman may thus be supported in many situations where a ladder could not be conveniently used, without the fatigue of keeping the muscles of the legs in constant exertion in clasping the rope, and with the facility of moving upwards or downwards, without extraneous assistance.-Mechanics' Magazine. PNEUMATIC FILTER. MR. PALMER, of Newgate-street, has lately made a useful application of pneumatic pressure, in the filtering of liquids. His apparatus consists of a tin vessel, divided by a rim at about the middle; where also is a moveable division, formed of a plate of zinc, perforated with holes. This plate supports the superincumbent pressure; and above it is laid a filtering fabric of paper, calico, flannel, leather, felt, or other material. An air-pump is attached to the upper part of the lower division; and a heavy loose brass ring is placed above the edges of the filtering fabric, to keep the rim close to the side of the filter. The filtered liquor is drawn off by a cock. To use this filter, having prepared the fabric, fill the upper portion of the vessel with liquid, exhaust the air from the lower part by means of the air-pump, when the liquid will quickly pass through, leaving the filter nearly dry; then unscrew the air-pump, and draw off the fine liquid. - Mechanics Magazine; abridged. TRANSPARENT WATCH. A WATCH has been presented to the Academy of Sciences at Paris, constructed principally of rock crystal. It was made by M. Rebellier, and is small in size: the works are visible; the two teethed wheels which carry the hands are rock crystal, and the other wheels are of metal. All the screws are fixed in crystal, and all the axles turn on rubies. The escapement is of sapphire, the balance wheel of rock crystal, and its springs of gold. This watch is an excellent timekeeper, which is attributed, by the maker, to the feeble expansion of the rock crystal in the balance-wheel, &c.- Mechanics' Magazine; abridged. COOKING CLOCK. MR. LOUDON describes an egg-clock, which rings a bell, or sets off an alarum, at any number of minutes required: it is formed by a dial like that of a watch, but larger, surmounted by an alarum-bell, and with five divisions, representing five minutes on the dial. This being fixed up over the kitchen fireplace, the index is moved to the number of minutes the egg is to be boiled; and, during the boiling, the cook may be otherwise employed till the alarum goes off. The act of moving the index, or pointer, backwards, winds up the clock. The principle may be applied to a larger dial, so as to mark the time requisite for cooking articles generally; and Mr. Loudon has accordingly caused such an apparatus to be made. Hence the ordinary work of the kitchen may go on without the interruption of watching, &c. SUPERB PALACE GATES. MR. DEAN, of Bolton, has cast two pairs of beautiful gates and palisading, for the Imperial Palace, at Constantinople. The height of these gates, with the central ornaments over them, is 35 feet; the latter being richly gilt. The height of the gates is 22 feet, and the width of the gateway 12 feet, exclusive of the hanging pilasters of pendent vineleaves, which are 6 feet 3 inches wide. The gates will be supported by marble columns, surmounted with elegant vases; and the palisades, 23 feet long on each side, are to be fixed in marble basements. The weight of the two pairs of gates is 40 tons; and the cost upwards of 20,000l. when fixed; patterns, 900l. ; packing-cases, 150l.-Mechanics' Magazine. NEW METHOD OF PERFORATING GLASS. Put a drop of spirit of turpentine on the spot where the hole is to be made, and in the middle of this drop a small piece of camphor. The hole can then be made without difficulty, by means of a well tempered borer, or triangular file. Solid turpentine answers as well as the spirit and camphor.-Annales des Mines. VARIETIES OF IRON. DR. SCHAUFHAENTL has detailed to the British Association a series of important experiments, which severally go to prove that the purest carbon, at the highest temperature, retained hydrogen, and occasionally azote, and that what was considered to be pure carbon was, in reality, approaching to a carburet. He described a method of obtaining graphite by running puddling slag in a fluid state, or silicates of iron and manganese, over fragments of pit coal; which, on being cooled, left the graphite in thin layers on the surface of the slag. The molecules of iron, according to these experiments, are arranged in the grey cast-iron in the most regular form, having all their surfaces in one plane; the most equal distribution of molecules appeared in hardened steel; collecting in fascicular aggregation in soft steel, and being loose and longitudinally arranged in wrought iron. Pure iron could not be welded; the welding power depends on its alloy with the carburet of silicon; the good and various qualities of all the wrought irons depended on the alloys of pure iron with other metallic bodies; and the presence of most of the electro-negative metals had been generally overlooked in the existing analysis of iron. The presence of arsenic in Swedish steel, when forged red hot, could be ascertained by its smell; as well as in the Low Moor iron. The usual solution of iron under analysis, in order to separate those metals from the iron, must be, for the necessary correction, divided into two parts-one to be treated with a current of sulphuretted hydrogen, the other part dropped into sulphydrate of ammonia, and carefully digested. A small quantity of silica was more difficult to separate from a large quantity of iron than generally seemed to be believed; and the real amount of carbon could only be ascertained by Berzelius's method of burning iron in a current of oxygen, or mixed with chlorate of potash and chromate of lead in a glass tube, used first by Berzelius for analysis of organic bodies. The author maintained that steel was an entirely mechanical production of the forge hammer, which tore the molecules of certain species of white cast-iron out of their original position, into which the forces of attraction, in respect to the centres, as well as to the position of the molecules, had arranged those molecules by the slow action of heat. Steel, as it came out of the converting furnace or the crucible, was nothing more or less than white cast-iron; of which Indian steel, called wootz, was the fairest specimen. The author finally gave an analysis of two specimens of cast-iron and one of steel. The first specimen was French grey iron, from Vienne, department de l'Isère, obtained from a mixture of pea-iron-ore with red hematite, by means of coal from Rive de Gier and heated air, specific gravity, 6.898. The second specimen was Welsh iron, from the tin-plate manufactory of the |