formed, the ground should be weeded, and if ne- | broad in the middle, so as partly to enfold the hoops, cessary, the plants thinned. After this the crop advances so rapidly that the outspreading leaves soon cover the ground, and thus completely prevent the growth of any more weeds. There is therefore no more trouble with the ground till the time of gathering, an important circumstance for the cultivator, who is then busy with his corn harvest. The beet does not attain its full perfection till the month of October. The best seed is that obtained from beet which has not been transplanted, and which has produced thin spindle-formed roots. Among the varieties which produce this kind of root, one has a pale red rind, and is internally quite white. This is a valuable variety to the manufacturer, yielding much sugar and an agreeably sweet syrup; others have a deeper red rind, and reddish circles or stripes within. These have a less agreeable syrup, retaining a taste of the root, which cannot be removed without expensive chemical processes. Other varieties are white on the outside and yellow within. These yield much crystallizable sugar, but are not fit for moist or raw sugar on account of the disagreeable taste of the syrup. Various experiments have been tried with beet, to ascertain the effect of light on the development of the saccharine principle, and it seems to be fully proved that as in the case of asparagus, endive, &c., the part protected from the light becomes sweet, while the other parts remain bitter, so with beet-root, the saccharine principle is greatest in those roots which are the most effectually protected from the light. Thus the natural growth of these plants, by which the leaves form a thick and umbrageous covering to the whole of the ground, should by no means be interfered with, and the practice occasionally followed of removing all the large leaves, is one which must necessarily deprive the root of a portion of its most valuable properties. The only leaves which it is safe to remove are those which have begun to droop or decay; but to pluck the large succulent leaves, however convenient they may be as food for cattle, is very unwise in those who grow beet for making sugar. For a description of the process by which the sugar is obtained from beet-root, see SUGAR. BELL. [See CASTING.] and narrow at the two ends, thus forming a sort of enclosed chamber, capable of being enlarged or contracted by raising the upper board while the lower one remains stationary. To the lower board is fastened a metal pipe, and a hole is also made in the centre of this board, which is covered on the inside with a leathern flap or valve opening inwards. On raising the upper board the enclosed air is of course rarefied, and air from without rushes in by lifting up the valve. Then on pressing down the top board, the air is compressed, and driven forward along the pipe with a velocity depending on the amount of force with which the two boards are pressed together. The blast is not continuous, but in puffs,' an interval of time being required for the air to enter the bellows through the valve, the blowing interval being to the filling interval as the areas of the apertures. In the oldest smelting houses this irregular blast was remedied by employing two bellows which blew al ternately, the one blowing while the other was filling. To supersede the necessity of frequent repairs, they were made entirely of wood, except the pipe or twyere. This invention is ascribed by Beckmann to one Lewis Pfannenschmid, of Thuringia, who settled at Ostfeld, near Goslar, in 1621, where he excited the jealousy of the bellows-makers of the place by the superiority of his machines. It is stated, however, that bellows entirely of wood for smelting houses and for organs, were constructed at Nuremberg as early as 1550. Beckmann describes these machines in the following terms:-"The whole machine consists of two boxes placed the one upon the other, the uppermost of which can be moved up and down upon the lower one, in the same manner as the lid of a snuff box which has a hinge moves up and down when it is opened or shut, but the sides of the uppermost box are so broad as to contain the lowermost one between them, when it is raised to its utmost extent. Both boxes are bound together at the smallest end where the pipe is, by a strong iron bolt. It may be readily comprehended, that when both boxes fit each other exactly, and the upper one is raised over the under one, which is in a state of rest, the space contained by both will be increased; and consequently more air will rush in through the valve in the bottom of the lower one; and when the upper box is again forced down, this air will be ex BELL-METAL. An alloy of copper and tin. "See pelled through the pipe. The only difficulty is to BRONZE. CASTING.] BELLOWS and BLOWING MACHINES. The common bellows is a very ancient instrument for assisting the combustion of a fire, by injecting into it a larger portion of air than would be supplied without such aid. The first form of this machine resembles that of the lungs, and was doubtless suggested by the common practice of blowing the fire by means of the mouth. It consists of two flat boards of an oval or triangular shape, each furnished with a projecting handle, and between the boards two or more hoops are bent to suit their figure. To the edges of the boards is nailed a piece of leather, prevent the air which forces its way in from escaping anywhere else than through the pipe; for it is not to be expected that the boxes will fit each other so closely as to prevent entirely the air from making its way between them. This difficulty, however, is obviated by the following simple and ingenious method:-On the inner sides of the uppermost box (1) A very convenient form of domestic bellows was introduced a few years ago, producing a constant blast. A vaned wheel was enclosed in a tinned-iron box communicating with a tube. The supply of air was obtained by means of holes in the side of the vessel, so that by turning a small multiplying wheel at the side. along the tube. the vane was set spinning, and, drawing the air in, projected it out BELLOWS AND BLOWING MACHINES. there are placed movable ships of wood, which by means of metal springs art pressed to the sides of the other box, and up the space between them As these long slips of wood might not be sufficiently pliable to suffer themselves to be pressed close enough, and as, though planed perfectly straight at first, they would in time become warped in various directions, incisions are made in them across through their whole length, at the distance of from 15 to 18 inches from each other, so as to leave only a smal space in their thickness, by which means they acquire sufficient pliability to be everywhere pressed close enough to the sides." These bellows are made of clean fir-wood without knots. They are represented in Fig. 117, in which A EBF is the upper chest. BF the line of hinges, I the handle, and P the blast pipe, which is sometimes furnished with a valve opening wards, to prevent the burning coals from being sucked into the bellows when the upper box is drawn up. The lower box, with one of the valves v, is shown separately in Fig. 118. The slips of wood at the sides are apt to become damaged, but they can be easily repaired, and every 3 or 4 months the outer sides of the inner box and the bolt which keeps the boxes together must be smeared with oil. These bellows are of very large size; they are 16 feet long by 5 feet, and the circular end is also 5 feet. The rise is 3 or 34 feet, expelling at each stroke about 90 cubic feet of air, and making eight strokes per minute. The great objection to bellows of this kind, is the want of a continuous blast. This was first remedied 123 nie a contras hast. Thus it will be seen, This construction will be understood by reference to the bell ws in Halley's portable forge, Fig. 1119, in which a a is a square frame of iron passing round the whole; ¿¿, pil- platform or hearth Fig. 119. for the forge fire; d, the bellows made fast by nected by a rod g, which passes across the Fig. 120. by the addition to the single bellows first described, furnace portable, the parts are taken asunder, and of a third board of the same shape as the other two, the bellows and frame are placed on the hearth e, the and connected with the lower board by means of a pipe h and the legs b are packed on the top and sides piece of leather, thus making two exactly similar of the bellows, and the whole is shut up in a box, cavities or chambers, separated by the lower board of formed by the hearth of the forge with its side the single bellows, which now becomes the middle plates; the cover is then turned down by its hingeboard of the double bellows. Each of these two joints upon the box, and secured by boards is furnished with a valve, and the blast-pipe padlock. is connected with the upper part of the middle a hasp and By board The lower board is held down by a weight, rocker, with a string or chain fastened to it. The smith's bellows is worked by means of a as in Fig. 121, in which a is B the movable lower board, e the raised, by which means air rushes into the lower parallel to each other, cavity, and in its descent forces air into the upper the blast-pipe, Carty, the rares preventing its return, and the fixed board with the pipe inserted, p the upper move weight on the upper board forces it out through the able board loaded with a weight. Motion is gra eing 5 of the furnace is an ingenious contrivance for preventing the twyere from rising when the bellows is drawn up. It consists of a bar, the bottom of which presses on the end of the twyere, while its tip hitches into a loop of iron placed between two laternal studs or staples. The dotted line shows the form of the hearth, and the direction of the flue. A very simple form of bellows, perhaps the simplest, is that used by the Chinese smiths. It consists of a square pipe of wood, Fig. 123, with a square board B exactly fitting it, which is moved to Fig 123. will be 113.19 inches, and the upper board would require a weight of 56.5 lbs. for a blast equivalent to a pressure of lb. on the square inch, or a velocity of 207 feet per second, a blast well adapted to a smith's forge. The force of the blast can be varied by altering the diameter of the pipe, for which a special contrivance is sometimes made. In portable forges, the boards are brought together by means of helical springs instead of weights. In some of the native furnaces for smelting iron ore in Hindostan two bellows made of skin are used; a pipe projects from the bottom of each, and is Fig. 122. INDIAN BELLOWS. united with the blast-pipes of the twyere. These bellows are placed on a plank laid across a trench in front of the furnace, and at the further end of the plank is seated a man, who by working the bellows alternately, one with the right, and the other with the left hand, produces a continuous blast. In front and fro by means of a handle H. At the further end is the blast-pipe P, and in each side is a valve (shown by the dotted line) opening inwards. A very ingenious and powerful blowing machine, founded on the principle of the Chinese bellows, was constructed some years ago by Mr. Vaughan, and is described in the Encyclopædia Britannica. It consists of two square boxes placed side by side. A piston, P P', Fig. 124, fitting each, is Fig 124. drawn backwards and forwards by means of the rod R, working horizontally on wheels w w, by means of the spear s, which communicates with the crank of a wheel at some distance off. The body of the piston is a cast-iron plate with a socket in the middle to receive the rod; the diameter of the piston is about of an inch less than that of the box, and it is made tight by the following ingenious arrangement. Two pieces of wood, w, are cut diagonally to receive pieces of leather, 1, between them, and both the Fig. 125. leather and the wood are firmly bolted to the plate of the piston i. The leathers extend about two inches beyond the wood, and their slight elas ticity keeps them in contact with the metallic surface, so that when the piston is in motion the leather on one side claps close to the surface, rendering it air-tight, while the leather on the other side is loose. The projecting curved pipes, I 1', communicate between the box where the piston works and the airchest c. When the piston moves from A to B, the valves 1, 3 open, while 2, 4 remain shut. The air contained in the box is forced through the valve 6, BELLOWS AND BLOWING MACHINES. into the chest c, and thence along the blast-pipe в P. In the return stroke, which is the whole length of the box, the valves 1, 3 are shut, while 2, 4 are open, and the air is forced through 5 and then along B P. Two of these machines work at the same time by two cranks, so that one is in full blast while the other is returning the stroke; hence there are 4 puffs produced by 2 double strokes, and these occurring alternately at almost equal intervals, a steady blast is produced. Mr. Vaughan recommends that four of these boxes be at work at once, so as to produce 8 puffs in one double stroke, which if divided by equal intervals, produce a sufficiently uniform blast for any purpose. The machine makes 70 strokes per minute; the nose-pipe, where the blast enters the furnace, is 2 inches in diameter, and discharges 1,200 cubic feet per minute. A uniform blast is also produced by the arrangement shown in Fig. 126, in which two cylinders are connected with each other and with the discharge pipe. P is the working piston, which is worked by a rod connected by double chains with the arched head of a working beam moving round a gudgeon. By the descent of this piston, the air is compressed and forced through the valve v, while the loaded piston L is raised to its highest point. The piston P now ascends, and its cylinder is filled with air through the valve v', during which time the loaded piston gradually descends. The valve v is closed by the pressure and the air is forced out through the discharge pipe d. Before all the air in the cylinder L is discharged, it receives a fresh supply by the descent of P, and thus while the engine is in motion the blast is rendered continuous. The trompe, or water-blowing engine, Fig. 127, is an ingenious and economical method of obtaining a blast. It is used in Savoy, Carniola, and in America. It is formed of two pipes or funnels, one of which is at b, set upright, and terminating above in a cistern of water a, and below is a tub or drum c. The conical part p, just below the cistern, is called the etranguillon, and prevents the water discharged into the trompe from filling the pipe in falling, but divides it into many streamlets. Below this narrow part a number of holes qq are perforated obliquely, through which air is admitted and carried by the water in its descent. The air parts with the water by dashing upon a castiron slab d within the drum. At the bottom of the drum is an aperture for the escape of the water, a 125 but to prevent the air from escaping with it, the water as it issues is received into a chest l m n o, divided into two parts by a vertical slide-plate between mn. By raising or lowering this plate the water may be maintained at any required level within the drum, so as to give the included Fig. 127 air a greater or less pressure. The water finally drains off by the hole o. To the upper part of the drum is fitted the air pipe ef, divided at the point f into three tubes, the principal of which is for the cupellation furnace, and the other two at g for the smelting furnaces. Each of these tubes ends in a leather socket and an iron nose-pipe k adjusted in the twyere of the furnace. A flood-gate fitted in the upper cistern a regulates the admission of water. The usual height of this apparatus is about 26 feet to the upper level of the water cistern. Its total length is 36 feet, and its width 2 feet to give room for the drums. 72 also the length of the stroke. Twenty strikes per' minute are made in each of the three indeTY, OCRresponding to an expulsion of weary 1,00 mabur feet of air per minste The fara glider is used to regulate the pressure, as will be explained presently, The piston-rods are worked so that wile the is at, the hirtest, another is half-way down or up, and the third is quite down. A laze ina widetest, 11 feet 5 inches long, is situated in the solar below : to this the four cylinders are fixed. The bottom of the fourth cylinder is open to the chest; the others are closed at bottom. From this chest, under the third cylinder, proceeds the main eduction-pipe, from whith branch-pipes proceed to the several forms, each pipe being furnished with a cock for turning the blast co or off. Behind the eduction-pipe is a short cylinder, containing a valve, shown in the section, Fig. 199, which passes through the axis both of the valve cylinder and the blowing cylinder. Fig. 129. On the principal axis are three eccentric wheels, with iron straps, connected with a lever under the wind-chest, and these wheels are so arranged in respect to the ecrresponding crank that when the piston of any cylinder is either above or below, the lever is horizontal, and the valve exactly BENZOIC ACID. on the back of the gade. The form of the bottom This of is supposed to be the hydruret of a basic substance named bearyle, from its relation to benzoie acid, containing C, H, O2 Pure hydruret of ben cyle, or bitter-almond cl C, H, 0, +H), is a thin colourless faid, of great refractive power, and of a peculiar and agreeable odcur; its density is 1.043, and its bolling-point 356. Its vapour is inflammable, and burns with a bright smoky flame. It is soluble closes the hole in about 30 parts of water, but alcohol and ether When the piston in dissolve it indefinitely. It absorbs oxygen rapidly this figure begins to, from the air, and forms a mass of crystallized benzoic ascend, the end E of acid. It is doubtful whether the pure oil is poisonous, the lever continues to but the crude product is highly so, and yet this is sold ascend also, and the for flavouring puddings, custards, &c. other end descends, Benzoic acid, or oxide of benzoyle, BzO (C1 Hs O2 and being connected+O, is not usually obtained by the oxidation of E with the valve-rod at bitter-almond oil. Several of the balsams, especially G, this also descends, and opens a communication gum-benzoin, yield benzoic acid in abundance. By between the interior of the cylinder and the external exposing this substance to a gentle heat in a subliming air, which rushes in with a fresh supply. This valve vessel, the benzoic acid is volatilized, and condensed continues to descend until the piston is half-way up; in the upper part of the apparatus. The best conit then begins to ascend until the piston is at the trivance for this purpose is a shallow iron pan, conhighest point, when the valve has the position shown taining the substance to be sublimed, in a thin layer: in the figure. The piston now descends, but the valve- a rod continues to ascend, and opens a communication between the cylinder and the wind-chest, into which the air is forced by the piston. When the piston is half-way down, the valve-rod has reached the highest point, and then continues to descend with the piston until the latter is down, when the hole h is again covered with the valve. In this way the three cylinders are successively opened to the atmosphere and to the wind-chest, and a constant influx of air is produced. To preserve a steady action in the valve-rods, they are made to pass through guards level with the floor . The fourth cylinder has no bottom, but is open to the wind-chest, and its piston, which weighs 700 lbs., serves only to regulate the pressure, which amounts to about lb. on the square inch. When the pressure exceeds this, the piston rises, and opens a safety-valve Fig. 130. sheet of bibulous paper, pierced with a number of pin-holes, is stretched over the pan, and a cap of stout cartridge-paper, secured by a string or hoop, is drawn over the whole, as in Fig. 130. The pan is slowly heated on a sand-bath; the vapour of the acid condenses in the cap, and the crystals are prevented from falling back into the pan by the porous paper. The acid thus obtained is in the form of snow-white, light, feathery crystals, with a fragrant odour, which is due to the presence of a small quantity of volatile oil. A more abundant product may be obtained by mixing the powdered gum-benzoin with an equal weight of hydrate of lime, boiling the mixture with water, filtering, and evaporating, and then decomposing it with an excess |