said to knead itself, there being no arms, beaters, or agitators whatever, it is calculated that the power saved by it is very considerable, while, from the simplicity of its construction, the cost is moderate.

The patentee is at present engaged in combining with this kneading machine an apparatus for preparing carbonated water, highly charged with the gas, with which he proposes to mix up the flour to form dough, for the purpose of making the bread spongy or vesicular, without having recourse to the fermentative process; the result of which process, under the most favourable circumstances, he considers to be detrimental to the health of those that eat the bread, (owing to the deposition of fermentable matter in the stomach,) while it is destructive of a portion of the nutriment of the flour.

KNIVES (including Forks). Knives are well-known instruments, made for cutting a great variety of substances, and adapted by differences in form to various uses; but the two principal sorts may be classed under the terms of pocket-knives and table-knives, with their now necessary accompaniments, forks. The manufacture of these articles in this country is almost wholly conducted at Sheffield. Our account of the process of making them must necessarily be concise, and afford only a glimpse of the procedures, as it is manifestly impossible for us to transform the uninitiated into cutlers by any information that we can give.

In the making of pocket-knife blades, one workman and a boy are generally employed; the boy attends to the heats, (that is, to the rods of steel in the fire,) which he successively hands to the forger, and takes back the rod from which the last blade was formed. One heat is required to fashion the blade, and a second to form the tang, by which it is fastened into the handle. The skill of the forger is displayed in forming it so perfectly by his hammer, as to require but very little to be filed or ground off in the subsequent operations. The springs for the back of the knife, and the scales which form the rough metal under-handle, and to which the other pieces are rivetted, are made by a distinct class of workmen. In the forging of table-knife blades, and other blades of a similar or greater size, the forger has an assistant, who, with a large hammer, strikes alternately with him; and the hammering of all blades is continued after the steel has ceased to be soft, in order to condense the metal and reader it very smooth and firm. Table-knife blades are usually made with iron backs, which are welded to the steel by a subsequent forging, to that of forming the cutting edge; the thick piece that joins the handle, called the shoulder or bolster, as well as the tang that goes through the handle, is forged out of the iron immediately after the welding of the steel blade: dies and swages being employed to perfect and accelerate the shaping of these parts. When the forging is completed, the blades undergo the processes of hardening and tempering, already explained in our account of the steel manufacture (article IRON). The blades are then ground upon a wet stone, about 4 feet in diameter, and 9 inches wide, which roughs out the work; they are subsequently finished or whitened, as it is termed, upon a finer dry stone; and the shoulders or bolsters are ground upon a narrow stone, about 3 feet in diameter, which completes the grinding. The next process is that of glazing the blades, which is effected upon a wooden wheel, made up of solid segments, well fitted and secured together, and with the ends of the fibres of the wood presented to the periphery of the circle; over this is extended a piece of leather, which is charged with emery or other powders, adapted to the finish or nature of the work required.

It is only about 200 years since, that table-forks were known in England, when they were introduced from Italy; and even now, in some remote parts of Scotland and Ireland, they are regarded as useless articles of luxury. The cheaper kind of forks are made by casting them from malleable pig-metal, (see Izos,) sometimes denominated "run-steel;" and some of these, which are well annealed and worked under the hammer, turn out very serviceable and good. Those made of wrought metal, were formerly either forged, and the prongs drawn out by the hammer, (and welded together, or they were forged into one solid piece, and the spaces between formed by cutting away the metal. These processes, however, were tedious and expensive, and a great improvement in

their manufacture has been introduced. The tang, shoulder, and a thick, flat piece, called the blade, are forged, and the blade is then submitted to the action of a pair of dies, contained in a powerful fly or stamping-press; the dies being so formed as to force or cut out the superfluous portion of the metal and raise the curved swelled portions at the junction of the prongs, termed the bosom. The forks after this operation are filed up, ground, glazed, and burnished, when they are ready for hafting, which is a distinct business.

The instruments required for hafting knives and forks are few and simple. The principal are, a small polishing wheel and treddle, mounted upon a stand, a bench vice, and a kind of hand vice to fix in the bench vice, termed a snapdragon; it has a pair of long projecting jaws, adapted to hold a piece of metal or other substance, with the flat side uppermost, in order to be filed or otherwise worked; a few files, drills, drill-box, and breast-plate, burnishers and buffs, emery, rotten stone, &c. The substances used for covering the handles are almost infinite; the chief are bone, horn, ivory, tortoiseshell, and wood of every kind. The several pieces of the handle being filed to the shape intended, holes are drilled through them for the pins by which they are afterwards rivetted together. The pinning is at first loosely done; until the blades, springs, and all the parts are well adjusted and fit closely, they are then firmly rivetted together. The handles are afterwards scraped and then polished, by means of buffing, on the wheel.

KNIFE-SHARPENERS. This term has been given to a variety of convenient modern instruments, especially adapted to the sharpening of knives at table, but particularly carvers, and are intended as substitutes for the common steel. For these instruments several patents have been obtained, and a considerable manufacture of them has been established.

Filton's Patent Sharpener, without its usual accompanying ornaments, is represented in the annexed

cut; it consists of two horizontal rollers, placed parallel to each other, which revolve freely upon their axes, (represented by the two black dots;) at uniform distances, there are fixed upon each roller, narrow cylinders or rings of hard steel, the edges of which are cut into fine teeth, and thus form circular

files; the edges of the files in the opposite rollers overlap each other a little, so that when a knife is drawn longitudinally between them, the edge of the knife is acted upon on both of its sides at once. The rollers turn round with the slightest impulse, consequently, they wear uniformly, and will last a considerable time. A good edge is given to a knife by just drawing it from heel to point two or three times between the rollers; and thus obviates the necessity of imitating the skill exercised by a butcher upon his steel.

Westby's Knife-sharpener, which was patented in 1828, is a very pretty and ingenious instrument; an immense quantity of them have been sold, and it is said, have been the means of greatly enriching the proprietor of the patent. In the engraving on the next page, Fig. 1 exhibits an end elevation of the instrument, and Fig. 2 a side elevation of the bars, with a section of the boxes a and b, to show the interior. The same letters in each figure have reference to similar parts; a is a small oblong box, surmounted by a smaller box b; in the top of the latter there is a slit made throughout its length, and of sufficient width to receive the square steel bars c c. The box a has two similar slits. The surfaces of the bars are draw-filed, they pass through the slit in b, and alternately through both slits in a, so as to cross each other, as shown in Fig. 1. The lower ends of these bars are supported upon a plate of metal d, which can be elevated, so as to a bring a different portion of the bars into operation, by means of the screw underneath; ff are two screws passing through the holes

in d, to preserve its parallel motion, and likewise to support the bottom of the box; & is a tightening screw to steady the bars c c.

The mode of operating with this instrument is merely to place the edge of the knife upon the bars, so as to bisect the angle formed by them, and then

draw the knife backward and forward. As the surfaces of the bars wear away, different sides can be presented, or they can be shifted from end to end, so as to present fresh surfaces to the knife.

Church's Patent Knife-sharpener consists of two very flat truncated cones, fixed with their smaller surfaces together, and with several rectangular projections in the one, fitting into similar cavities in the other. The conical surfaces of both pieces are serrated with a series of very fine teeth extending angularly towards their centres; these are placed upon the shank of the fork, between the shoulder and the handle, with which they correspond in diameter so nearly as to constitute an ornamental finish to the small end of the handle. In the position and size of these consist the principal merit of the sharpener. When used for sharpening scythes, or other large cutting instruments, the conical pieces are made larger, and fitted on an axis between two prongs of a forked apparatus, with an appropriate handle.

Westby's second Patent.-The extraordinary success attendant upon Mr. Westby's contrivance for sharpening table-knives induced him to figure a second time as a patentee, " for certain improved apparatus to be used for the purpose of whetting or sharpening the edges of the blades of penknives, razors, and other cutting instruments." The first improvement mentioned in the specification consists in the application to a hone, or oil-stone, of a guide to keep the edge of the razor, or other cutting instrument, at the same angle with respect to the surface of the hone, during the operation of whetting. This is effected in two ways; first, by placing over the hone a plate of metal extending its whole length, and adjustable, at any required distance parallel to its surface. by set screws; now, in the operation of sharpening, the back of the instrument is kept resting upon the guide-plate, while the edge is applied to the hone. The second method consists in the application of two hones placed in an erect position, with a space between them for the razor, which is to be fixed by screws into a small horizontal frame, made to slide upon a circular rod, so that the edge can be applied alternately to the hones; these can be elevated and depressed at pleasure, so that their surfaces may be uniformly worn while in use. The patentee also mentions in his specification a method of attaching to his hone a leather strap which is made double, and kept stretched by adjusting screws attached to the frame of the hone, or else to the end of a rod extending

lengthways between the two folds of leather. This last contrivance does not appear to us to be scientifically adapted to the object in view, as the pressure of the edge of the instrument upon a strap of leather only supported at its extremities, must produce a tendency in the leather to wrap round the acute angle of the edge of the instrument, and render it obtuse.

L.

LABORATORY. A place fitted up and supplied with the necessary apparatus for chemical operations. Laboratories for conducting chemical processes on a large manufacturing scale will of course vary in their arrangements according to the main object for which they are designed. For experimental and general purposes a laboratory is more advantageously placed above than below ground, that it may be as dry as possible; the air must have free access to it; and it must even be so constructed that, by means of opposite openings, a current of air may be admitted to carry off noxious vapours. A chimney ought to be constructed so high that a person may easily stand under it, and extending the length of one of the side walls. The chimney should be high, and sufficiently contracted to make a good draught. When charcoal is the only fuel to be employed no soot will be deposited, and therefore it need not be so wide as to allow a chimney-sweeper to pass up it. Under this chimney may be constructed some brick furnaces, particularly a melting furnace, a furnace for distilling with an alembic, and one or two ovens like those in kitchens. The rest of the space ought to be filled up with stands of different heights, from a foot to a foot and a half, on which portable furnaces of all kinds are to be placed. These furnaces are the most convenient, from the facility of disposing of them at pleasure; and they are the only furnaces which are necessary in a small laboratory. A double pair of bellows of moderate size must also be placed as commodiously as possible under or near to the chimney, and having a pipe directed towards the hearth where the forge is to be placed. The necessary furnaces are the simple furnace, for distilling with an alembic, a lamp furnace, two reverberatory furnaces of different sizes for distilling with retorts; an air or melting furnace, an assay furnace, and a forge furnace. Under the chimney, at a convenient height, should be a row of hooks driven into the back and side walls, upon which are to be hung small shovels, iron pans, tongs, pincers, pokers, and various utensils for disposing the fuel and managing the crucibles. To the walls of the laboratory should be fixed, or suspended, rows of shelves, of different breadths and heights, for containing bottles and glass vessels, which should be as numerous as is possible, that the products of operations may be conveniently retained. The most convenient place for a stone or leaden cistern to contain water, is a corner of the laboratory, and under it a sink ought to be placed, with a pipe by which the water poured into it may discharge itself. As the vessels are always cleaned under this cistern, cloths and bottle-brushes ought to be hung upon hooks fastened in the walls near it. In the middle of the laboratory a large table is to be placed, on which mixtures are to be made, preparations for operations, solutions, precipitations, small filtrations; in short, whatever does not require fire, excepting that from a lamp. In convenient parts of the laboratory are to be placed blocks of wood upon mats, one of which is to support a middle-sized iron mortar, another a support for a middle-sized marble, or hard stone mortar, and a third for an anvil. Near to the mortars are to be hung sieves of different fineness and sizes; and near to the anvil, files, rasps, pincers, shears, and other convenient utensils for working metals, or giving them proper forms for the several operations; two movable trestles, to support a large filter or other apparatus, that they may be disposed of conveniently. On account of the dust from charcoal, the stock of this article had better be placed contiguous, but not inside the laboratory; also some dried furze or other quick burning fuel. In the same place may be put bulky articles, bricks, tiles, clay, lime, sand, and many other things useful in chemical operations. A small, solid table, for a levigating stone and muller; small mortars, of iron, glass, agate, and

Wedgwood ware; earthen, stone, metal, and glass vessels of different kinds; funnels, measures, glass-tubes; spatulas of wood, metal, ivory, and glass; pasteboards, writing paper, unsized paper, clean straws, horns, corks, bladders, linen strips, lutings, cements, paste, glue, portable bellows, brushes, boxes, &c. &c. are all eccasionally wanted in a laboratory. See Ure's Dictionary of Chemistry.

LAC. A resinous substance, the product of an insect found on several different kinds of trees in the East Indies. These insects pierce the small branches of the trees on which they feed; and the juice that exudes from the wounds is formed by them into a kind of cells for their eggs. Lac is imported into this country adhering to the branches in small transparent grains, or in semi-transparent flat cakes. The first, encrusting the branches, is called stick-lac; the second [are the grains picked off the branches, and called seed-lac; the third is that which has undergone a simple purification, as we shall presently notice. There is a fourth called lump-lac, made by melting the seed-lac, and forming it into lumps. To purify the lac for use he natives of India put it into long canvas bags, which they heat over a charcoal fire until the resin melts; a portion of the lac then exudes through the bags, which are subsequently twisted, or wrung by means of cross sticks at the ends of the bags, the surface of the latter being scraped at the same time to accelerate the process. The chief consumption of lac in this country is in the manufacture of sealing-wax and varnishes. It has been a great desideratum among artists to render shell-lac colourless, as, with the exception of its dark brown hue, it possesses all the properties essential to a good spirit varnish in a higher degree than any other known resin. A premium of a gold medal, or thirty guineas, for “ a varnish made from shell or seed-lac, equally hard, and as fit for use in the arts," as that at present prepared from other substances, was offered for some years by the Society of Arts. The editor of the Franklin Journal, of Philadelphia, observes, in reference to the foregoing, that "these ends are perfectly attained by the process given by Dr. Hare, which leaves nothing to desire, excepting on the score of economy." Were the oxymuriate of potash to be manufactured in the large way, the two processes, that of making the salt and of bleaching the resin, might be advantageously combined. "Dissolve," (says Dr. Hare,) "in an iron kettle, one part of pearl-ash in about eight parts of water; add one part of seed or shell-lac, and heat the whole to ebullition; when the lac is dissolved, cool the solution, and impregnate it with chlorine till the lac is all precipitated. The precipitate is white, but its colour is deepened by washing and consolidation; dissolved in alcohol, lac bleached by the process above-mentioned yields a varnish which is as free from colour as any copal varnish." About the same period of time as the publication of the foregoing, the before-mentioned premium of the Society of Arts was claimed by two persons, Mr. George Field, and Mr. Henry Luning. The Society, upon a due examination of both of the processes and products, found them both to answer the intended purpose, and awarded the sum of twenty guineas to each of the candidates.

The following is Mr. Field's process: Six ounces of shell-lac, coarsely powdered, are to be dissolved by gentle heat in a pint of spirits of wine; to this is to be added a bleaching liquor, made by dissolving purified carbonate of potash, and hen impregnating it with chlorine gas till the silica precipitates, and the soludon becomes slightly coloured. Of this bleaching liquor add one or two ounces to the spirituous solution of lac, and stir the whole well together; effervescence takes place, and when this ceases, add more to the bleaching liquor, and thus proceed till the colour of the mixture has become pale. A second bleaching liquor is now to be added, made by diluting muriatic acid with thrice its bulk of water, and dropping into it pulverized red lead, till the last added portions do not become white. Of this acid bleaching liquor, small quantities at a time are to be added to the half bleached lac solution, allowing the effervescence, which takes place on each addition, to cease before a fresh portion is poured in. This is to be continued until the lac, now white, separates from the liquor. The supernatant fluid is now to be poured away, and the lac is to be well washed in repeated waters, and finally wrung as dry as possible in a cloth.