this kind of work is selected; its surface is slightly | greased, and is applied in conjunction with the hooked stick h, to force the metal gradually inwards, as shown at 5, 6, 7, and also to curl up the hollow tead which stiffens the mouth of the finished vessel 9. In some cases the moulds m are made of the exact shape of the vessel to be turned: each mould is nade up of a number of pieces, each piece smaller than the central opening; so that like the parts of a hatblock [see HAT, Fig. 1130], or of a boot-tree, on taking out the central block all the other parts are easily released. It is important during the spinning to keep the edge exactly concentric and free from notches: should these occur, the edge is to be touched with the turning tool. "The operation," says Mr. Holtzapffel is very pretty and expeditious, and resembles the manipulation of the potter, who forms a bottle or vase with a close mouth in a manner completely analogous, although the yielding nature of his material requires the fingers alone, and neither the mould, stick, nor burnisher." 1 The second method of raising works is by means of the hammer, by the application of circles of blows applied much in the same order as the burnisher, which acts by the gradual and continued pressure on one circle at a time. The metal disk to be raised must be so selected as to size and thickness that it shall exactly suffice for the production of the article, leaving no excess of metal to be cut off, nor deficiency to be supplied; and the blows of the hammer must be so managed as to direction and intensity that the finished work shall be of uniform thickness throughout. Thus, a hollow ball 6 inches in diameter is made up of two circular pieces of copper each 74 inches in diameter: the circumference of the disk measures 22 inches, and this becomes contracted to 18 inches, or the circumference of the ball, while the original diameter of the disk, 74 inches, has become extended to 9 inches, or the girth of the hemisphere. This double change of dimensions is still more strikingly illustrated in the spinning of the tea-pot, Fig. 1807, the disk for which was about 1 foot in diameter; this is contracted to 2 or 3 inches at the mouth. In the use of the hammer for works of this kind, care must be taken to distinguish between opposed or solid blows, which have the effect of stretching or thinning the metal; and unopposed or hollow blows, which tend not to thin the metal but rather to bend and even to thicken it. Minute directions on these points are given in Mr. Holtzapffel's work. One of the most remarkable examples of raised works is the ball and cross of St. Paul's Cathedral, London, erected in 1821. The old ball consisted of 16 pieces riveted together: the present ball is of the same diameter, viz. 6 feet; this was raised in two pieces only, and may be regarded as a fine example of the coppersmith's art. The metal for the ball was first thinned and partly formed under the tilt-hammer at the copper mills, and sunk in a concave (1) In the first volume of the "Mechanical Manipulation" will be found a very full and highly instructive chapter on "Works in sheet metal made by raising." bed; the raising was effected with hammers not much larger than usual, and the two parts were riveted together in their place, the joint being concealed by the ornamental band. Most of the work of the cross and ball is hammered up; the consoles beneath the ball are of cast gun-metal. The whole structure is 29 feet high, and the weight of copper 34 tons. The ball and cross are strengthened by an inner framing of copper and wrought iron bars, stays, bolts, and nuts, extending through the armis aud downwards into the building, thus adding about 2 tons of iron to the load of copper. 38 oz. of gold were consumed in the gilding. Sugar-pans, stills, &c., are made of very large size, on the same principle. Works, such as jelly-moulds, in which the raising is very considerable, are produced by the hammer; but works in less relief, required in considerable numbers, are produced by means of dies. For the best works both the top and bottom dies are usually of hardened steel, but in some cases the bottom die is of cast-iron or hard brass: in many cases, the top die is also of lead, this metal being preferred from the facility with which it assumes the required shape, The method of producing figures in relief on buttons by raising and letting fall a succession of forces, is an example of this kind of work [see BUTTON, Fig. 393]; we are, however, now referring to larger works than buttons, in which cases the sheet of metal to be raised undergoes the same bendings and stretchings between the dies as if it were worked by the hammer, and unless gradually produced the metal will be cut and rent. This gradual action is brought about by placing a number of sheets of metal between the two parts of the die, and after every blow one piece is removed from the bottom, and a fresh plate added at the top: in this way the plates descend and gradually accommodate themselves to the figure of the die. The pieces are finished by being struck singly between dies which exactly correspond. In thus gradually bringing the plates into the required shape, they may require annealing from time to time. Thimbles are raised at 5 or 6 blows between as many pairs of conical dies, gradually increasing in height, but in passing from one pair of dies to another the metal requires to be annealed. The art of stamping and shaping sheet metal was made the subject of a patent granted to Mr. T. Foxall Griffith of Birmingham, Feb. 3, 1846. By the methods here employed, works with lofty and perpendicular sides, such as jelly-moulds, are produced by the alternation of stamping and spinning. By a former patent, the sheet metal, having been raised as far as possible in dies by stamping, the shaping was completed by burnishing to form. "In shaping sheet metal by stamping, as heretofore practised, the sides of the articles depend materially for the height of the raising on the stretching or extending of the metal; and, to this end, the metal at the outer circumference is supported throughout the process of stamping by a projecting flanch, which rests horizontally on the upper surface of the dies, such flanch being progressively reduced, and the metal thereof stretched or extended, so that, MM 2 from the bottom to the upper edge, the thickness of the metal is brought thinner and thinner, which is objectionable. At the same time, owing to the severe treatment to which the sheet metal is thus subjected, it requires to be more often annealed, in order to prevent its suffering injury by the successive processes of stamping; and such is the extent to which the metal is stretched or extended by raising, according to the old practice, that the disk, or blank of metal employed for raising a vessel of a few inches diameter to a considerable extent, is only about 2-inch larger in diameter than the finished vessel raised therefrom by stamping. Whereas, according to my invention, the blank or disk of sheet metal used for making any particular article when the sides thereof are upright, is of a diameter of about the diameter of the vessel or article added to the depth of the vessel: thus, supposing the vessel or article produced by stamping in a die be 6 inches in diameter and 3 inches deep, then the die or blank of sheet metal would B Fig. 1809. a The vertical sections, marked A to G, Fig. 1810, represent the several forms given to the sheet of metal aa, Fig. 1809, by employing a die such as that shown in the same figure, with a second point of bearing at ¿ ¿; the successive forces or top dies, that are employed, being so shaped as to bear only on the bottom of the vessel as far as the edge bb, and not over the sloping sides, the effect of which is to make the edge bb perform the office of a draw-plate, such as would be used for drawing cylindrical tubes. Having been progressively stamped to the contour of G, the work is burnished to form on a chuck, Fig. 1811. The work is again stamped in the second die, Fig. 1812, then burnished on the second chuck, Fig. 1813; struck in a third die, Fig. 1814, and then burnished on a third chuck, Fig. 1815, in order to make the metal proceed through the forms H to L, Fig. 1616. The work is occasionally annealed as required. Fluted works, such as M N Fig. 1818, are first raised nearly as cylinders with bottoms to the shape of L by the processes just noticed: the burnishing to form is then discontinued. The flutes are gradually developed by means of 2 or more pairs of dies and forces, Fig. 1817. In the first pair of tools for the object N the flutes are shallow, and the die is a little bell-mouthed: in the second pair the flutes K Fig. 1816. be about 9 inches diameter, and the article when stamped therefrom, if it be cut through the sides and bottom, all parts would be found as nearly as may be of the same thickness, and that thickness the thickness of the original sheet metal." fast in the die, the latter is perforated, and has a central rammer, Fig. 1819, which is raised by a side lever L to force the finished work out of the die. That the metal after the raising should be of uniform thickness throughout, is thus explained in the case of the cylindrical vessel already referred to. If the disk, 9 inches in diameter, by stamping in a die 6 inches in diameter, could have its margin folded up without puckering, it would have a rim of 14-inch high, the upper edge being of twice the primary thickness; but the stretching from the dies causes the height of the sides to become 3 inches, and therefore 7 RAISED WORKS IN METALS-RAISINS-RAPE-OIL. 533 the tapering thickness actually produced is gradually | is preserved from injury by being supported on a sanddrawn out, as in tube-drawing, to form the increased bags, Fig. 1823. height. RAISINS. In the south of Europe and in Egypt, So successful is the improved method of raising, &c. grapes are allowed to ripen and dry upon the that sheet-iron, which is much less tractable than cop-vine so as to form raisins. The sweet fleshy grapes per and brass, may be raised. The scaling of the surface of the iron during the annealing was at first a difficulty, but this was obviated by annealing after the manner adopted for malleable iron castings, [see ANNEALING,] the annealing mixture preferred being 1 part of pulverized iron ore added to 8 parts of coke or lime, preference being given to that iron ore which has been once used for annealing cast-iron. Thus, by the combined processes of stamping and burnishing to form and annealing, extinguishers can be raised from disks of sheet-iron: they are of course without a seam. The method of stamping with dies having the bevelled mouth and shoulder bb, Fig. 1809, allows vessels to be raised much higher than by any other method of stamping, even when burnishing to form is not employed in conjunction with stamping. The various ornamental details of raised work, such as escutcheons, concave and convex flutes, are usually added after the vessel or article has received its gene ral form by one or more of the processes described. If, from the shape of the work, swage tools, such as those represented in Fig. 1821, cannot be employed for raising the projecting parts, they are snarled up by means of a snarling-iron, s, Fig. 1822. One end of this iron is secured between the jaws of a tail-vice v, and the other end e is turned up so as to reach any part of the interior of a vessel. The work is held firmly in the two hands with the part to be raised or set-out exactly over the end e: the snarling-iron is then struck by an assistant with a hammer at h, and the reaction gives a blow within the vessel which throws out the metal in the form of the end of the tool. After the flutes or other ornaments have been snarled-up, the vessel or other object is filled with a melted composition of pitch and brick-dust, or some similar mixture, which, from its adhesive and yielding which grow upon the sunny sheltered slopes of hills are preferred. When the fruit is ripe, the grapes are thinned and the vine is stripped of its leaves. The sun then completes the saccharification and drives off the superfluous water. When the bunches are plucked they are cleaned, dipped for a few seconds in a boiling lye of wood-ashes and quicklime; the wrinkled fruit is then drained and dried, exposed to the sun upon hurdles for 14 or 15 days. The finest sun raisins are the plumpest bunches left fully to ripen upon the vine, after their stalks have been cut half through. An inferior kind of raisins is prepared by drying the grapes in an oven. In the year ending 5th Jan. 1853, 261,824 cwt. of raisins were imported into the United Kingdom, of which quantity 208,801 cwt. were retained for home consumption. The import duty is 15s. per cwt. from foreign countries, and 7s. 6d. per cwt. from British possessions. RAM. See HYDROSTATICS and HYDRODYNAMICS. RAPE-OIL. The seeds of Brassica rapa and B. napus are valuable for the large quantity of oil which they yield by expression. [See OILS and FATS.] B. rapa yields the largest quantity of oil. B. campestris yields a superior oil known in France as Colza oil. Rape-oil is thick, of a yellow colour, and with a peculiar taste and smell; it concretes into a yellow mass at about 28°. Its specific gravity is 0.9167. It is used in the preparation of woollen goods and of some kinds of leather. It is much used in France for burning in lamps. Colza-oil may be used without purification, and it is largely employed in lighthouse lamps. [See LIGHTHOUSE.] The common kind of oil is purified by being agitated with a 200th part of sulphuric acid, left to repose for 24 hours, when twothirds of its bulk of water at 165° are added, and the mixture stirred until it becomes milky. It is then kept for 2 or 3 weeks in a room heated to 80°, when it becomes clear by the deposition of a dark coloured sediment. It is lastly filtered by being drawn off into vats the bottoms of which are pierced with holes stuffed with filaments of carded wool or cotton. Having passed through this filter the oil is fit for use. The acid may be removed by the addition of powdered chalk. RAREFACTION. See AIR-EVAPORATION-ICE. RATAFIA. Certain liqueurs, such as noyau, curaçou, &c., are termed ratafias from the custom of drinking them at the ratification of an agreement. (Ratum and fio to make firm.) RATCHET-LEVER. See WHEEL. RAZOR. See CUTLERY. REALGAR is the red sulphuret of arsenic As S.. See ARSENIC. RECEIVER. See DISTILLATION. RECOIL ESCAPEMENT. Fig. 1163. See HOROLOGY, | acid resins may also be distinguished by the crystalline precipitate produced by the addition of their ammoniochloride solutions to nitrate of silver. RECTIFICATION. See DISTILLATION. RED LEAD. See LEAD. REED. See WEAVING. Some of the resins dissolve in sulphuric acid without decomposition in the cold, and they are preci REFINING or PARTING. See ASSAYING- pitated by the addition of water; but if heat be SILVER. REFLECTION and REFRACTION. See LIGHT. TION. applied sulphurous and carbonic acids are disengaged, and a carbonaceous mass is obtained mingled with another substance which has been improperly named artificial tannine. The action of nitric acid upon REGULUS. See ANTIMONY, vol. i. p. 59, where resins leads to the formation of various new products. this term is explained. REISNER-WORK. See BUHl-work. RESINS. Resinous substances are found in greater or less abundance in most plants. Many of them exude naturally from fissures in the bark or in the wood, or they are obtained from incisions made in certain trees and shrubs. As they exude they are commonly mixed with an essential oil, which either evaporates on coming in contact with the air, or is resinified by the action of oxygen. Such mixtures of volatile or essential oil with resins are sometimes called balsams [see BALSAM]. When gum is mixed with resins another class of substances is produced, called gum-resins. [See GUM-RESINS.] Acetic acid dissolves many of the resins, as does also muriatic when concentrated. The resins have been considered as oxides of definite hydrocarbons; but their analysis is very imperfect, and will be further noticed under TURPENTINE. RETORT, a vessel of glass, earthenware, porcelain, clay, iron, &c. in which some kind of distillation is carried on. Numerous examples of retorts are given in the course of this work. See GAS-NITRIC-ACID, &c. REVERBERATORY FURNACE. A furnace so constructed that the flame shall be reflected or reverberated upon the bed or sole over which the material to be operated on by the flame is spread. See COPPER RHODIUM. See INTRODUCTORY ESSAY, page c, also, PLATINUM. The resins when pure and free from essential oil-IRON-LEAD, &c. have no odour except when rubbed or heated. Their colours are pale yellow or brown; they are good insulators, and become electric by friction. Most of them are heavier than water and insoluble in that fluid; they have little or no taste, but those which have distinctive flavours derive them from minute portions of some non-resinous body. They are usually softened or even fused by being boiled in water, and some of them in such a case pass into hydrates. They are inflammable, burning in the air with a sooty flame, and yielding by dry distillation volatile liquids and inflammable gases. [See GAS.] RHUBARB, the root of one of the species of Rheum, a genus of plants of the natural family of Polygonaceae. Although rhubarb has been in use for centuries, the particular species of rheum which yields it is not known, in consequence of the best, or Turkey rhubarb, being obtained only by the Russians at Kiachta from the Chinese. There are six well-marked varieties in commerce, viz. the Russian or Turkey, the Dutch-trimmed, the Chinese, the Himalayan, the English, and the French. The following description refers to the first variety, also called Muscovite, Bokharian, or Siberian rhubarb. The pieces are of various forms, cylindrical, spherical, flat, or irregular, from 2 to 3 inches long, 1 to 3 broad, and 1 to 3 thick. The smaller pieces are preferred, the larger ones being employed for powdering. The holes observed in the pieces were originally made for suspending them while drying, or for ascertaining their quality. Other per The natural resins are usually composed of two or more resinous substances, which may be separated by the action of alcohol, in which most resins are soluble. They are also mostly soluble in ether, in sulphuret of carbon and in the fat and volatile oils. Alcoholic solutions of many of the resins act the part of feeble acids, reddening litmus paper, and combining with and neutralizing acids. These compounds are termed resinates or resin-soaps, and are distinguished from oil-forations are referred to the ravages of a small beetle. soaps by not forming a gelatinous emulsion when concentrated, and by not being separable from water by the addition of common salt: they are, however, detergent and form a lather like common soap. [See SOAP.] Other resins are indifferent either as an acid or a base, but there are a few which are regarded as basic. The resins are thrown down from their alcoholic solutions by the addition of water, the white pulverulent or curdy precipitate forming the magistery of the old chemists. The alcoholic solution of the acid resins is not precipitated by ammonia; but the precipitate thrown down by the addition of water is soluble in solution of ammonia. The alcoholic solution of the indifferent resins is precipitated by ammonia.. The The pieces are covered with a bright yellow-coloured powder, the result of friction during carriage, or from the process of rouncing or shaking them up in a bag with powdered rhubarb. The odour is strong and peculiar: when chewed it feels gritty from the presence of numerous raphides or crystals of oxalate of lime: it imparts a bright yellow colour to the saliva, and has a bitter, slightly astringent taste. When fresh cut, the root has a reddish-yellow hue, with white lines interspersed. The powder is of a bright yellow colour verging on red, but it is usually adulferated by admixture with an inferior kind. Black and worthless pieces of rhubarb are sometimes disguised by means of yellow ochire; and inferior rhubarb, or roots cut to resemble the genuine article, are some therewith. times sprinkled over with powdered turmeric, or dyed | removed to detach the shell and not crush the grain. A sifting and winnowing apparatus is attached to each pair of stones. When the husk is removed the grain is passed through a whitening machine, for the purpose of removing the inner cuticle or red skin. This machine resembles that described under BARLEY, Figs, 92, 93, and 94. The rapid motion of the grains through the machine and the friction to which they are exposed, cause them to swell and thus to split the red skin, which flies off in dust through the perforated revolving case. Many analyses of rhubarb have been made with the view to ascertain the source of its medical activity, which has been successively ascribed to a bitter principle, to an organic basis, to an acid, to a gum, to a resin, and to a colouring matter. Some later researches by Schlossberger and Döpping, show that there are three resinoid substances in rhubarb, together with extractive matter, and the medical virtues of the root are ascribed not to any one principle, but to a mixture of several, amongst which are tannin and gallic acid. The import duty on cleaned rice is 6s. per cwt. from foreign countries, and 6d. from British possessions; but when rough or in the husk (paddy) the ex-duty is 7s. per quarter for foreign, and 1d. per quarter for British. These considerable differences in the amount of duty have led to the practice of importing paddy and cleaning it in this country. The cleaning apparatus mostly consists of millstones for breaking the husk, or one millstone and one block of wood of similar shape, and the dark pellicle is got rid of by passing the grain between flat wooden surfaces covered with sheepskin, so as to produce an effect similar to that of rubbing the grain between the palms of the hands. A machine first used in the United States consists of a long hollow cylinder of wood with bars projecting from its inner surface: an internal cylinder is also furnished with bars alternating with the former. The outer cylinder is made to revolve slowly in one direction, and the inner cylinder rapidly in the other direction. The machine is in an inclined position, and is supplied with paddy from a hopper at the highest part: the friction of the arms causes the husk to separate, which is blown away by a current of air as it falls out of the cylinder, while the rice is collected in a bin. RIBBON, or RIBAND. See WEAVING. RICE is a valuable cereal grass, Oryza sativa, tensively cultivated in India, China, and most eastern countries; in the West Indies, Central America, and the United States, and in some of the southern countries of Europe. It occupies the same place in intertropical regions as wheat in the warmer parts of Europe, and oats and rye in the more northern. The rice plant appears to be a native of India, where it is cultivated largely, forming as it does the chief portion of the food of the inhabitants. The varieties of rice are innumerable; 40 or 50 at least being described. The rice fields require a large quantity of water, which is supplied by rain or by irrigation either from rivers or banks. The best rice fields are extensive open plains intersected by large rivers, so as to be annually overflowed by the inundations. Most of the rice lands of India, however, depend on the rains only. The different varieties of rice are divided by Dr. Roxburgh into two kinds; one, named Poonas or A800, is sown thick in June or July, and transplanted in about 40 days, when the plants are from 9 to 18 inches high: the fields are then kept constantly wet; they are more or less flooded, as some sorts require very little water, others a great deal. When the grain is ripe, the water is drained off, and the crop cut down with the sickle: it is either stacked or trod out by cattle. The grain is preserved in pits dug in high ground, and lined with the rice straw. The straw is stacked for feeding cattle during the hot season. The second division of cultivated rice is named Pedder Worloo. Rice is also divided according to the seasons in which it is reaped, into that which ripens in the hot weather of spring, in the summer, or in the winter. Carolina rice is grown in the marshy grounds of North and South Carolina. The grains are shorter, broader, and boil softer than the Patna or best Indian kind known in this country. Rice in its natural state, or before it is separated from the husk, is named paddy. The husk adheres very closely, and should be separated without breaking the grain. In India and China the operation is performed by beating the grain in a kind of rude mortar of stone or earthenware with a conical stone attached to a lever worked by the hand or foot, or several such levers are worked by arms projecting from the axis of a water-wheel. A preferable mode is to employ a mill in which the stones are sufficiently RICE GLUE, or JAPANESE CEMENT, is made by mixing rice flour intimately with cold water, and boiling the mixture. It is white, and dries nearly transparent, hence its use in making many articles in paper. When made with a smaller quantity of water, models, busts, &c., may be formed of it. RICE PAPER, a name applied to a delicate vegetable film imported from China in small square pieces of various colours, and used in the manufacture of artificial flowers and fancy articles, and also as a drawing paper for delineating richly-coloured insects or flowers. This substance is said to be a membrane of the bread-fruit-tree, and although it resembles an artificial production, yet on examination by the microscope it is found to consist of "long hexagonal cells, whose length is parallel to the surface of the film; |