GLANDERS, or Farcy, is a name given by veterinary surgeons to a disease affecting horses and other cattle. It appears in the form of a suppurative disease of the mucous membrane of the nose and of a pustular eruption. The former is sometimes called glanders and the latter farcy, but the two often occur together, and the pus discharged by the one will produce the other. In 1821, Mr. Muscroft drew attention to the fact that this disease could be communicated from the horse to the human system. In the same year cases occurred in Germany, and since then it has been demonstrated by a large number of cases that this disease often spreads from the horse to man. When it attacks man it is characterised by vascular injection of the nasal mucous membrane, on which chancre-like sores are formed, extending to the frontal sinus and neighbouring mucous surfaces, from which a profuse and offensive discharge flows. At the same time a tubercular or pustular eruption appears upon the skin, followed by suppurating bloody or gangrenous ulceration in various parts. These symptoms may be either acute or chronic. In the acute cases a primary fever is followed by the local disease. In chronic cases the local affection alone presents itself. The acute disease is ushered in by rigors, pains in the back and limbs. These symptoms are followed by phlegmonous tumours in various parts of the body, which are accompanied with pain and tenderness, and terminate in abscesses or boils. At the same time a discharge takes place from the nostrils of a matter more or less purulent, viscid, and mixed with blood. The eyelids frequently become tumefied, and discharge a thick viscid matter like that from the nose. About the twelfth day of the disease an eruption breaks out on the face, trunk, and limbs. It is preceded and accompanied by profuse and fetid sweats. The eruption is scattered, and resembles, according to circumstances, the vesicles of cow-pox, or the pustules of small-pox or ecthyma. These are sometimes accompanied with large vesicles (bulla), which become black, and discharging leave gangrenous sores. At first the pulse is full and quick; but it becomes rapid, small, irregular, and intermittent. The tongue is at first loaded with white fur, which afterwards becomes brown or black. Diarrhoea and tympanitis often come on in the course of the disease. This disease is generally fatal from the seventeenth to the twenty-first day. In the chronic cases the febrile symptoms are not so prominent. The local symptoms are much the same, but they progress more slowly. The abscesses are attended with a large amount of subcutaneous inflammation. A twelvemonth has been known to elapse in such cases as these before a patient has recovered or died.

There is no doubt that these symptoms are the result of a poison introduced into the system of man from the horse. In all cases contact with glandered horses has been ascertained to have taken place before the breaking out of the disease. Matter has been taken from the ulcers and membranes in men, and horses have been inoculated, and the disease has been produced. The disease has also been produced by compelling animals to swallow the poisoned matter in their food. There can, therefore, be no doubt that the poison can be absorbed both from mucous and cutaneous surfaces. This being ascertained, it becomes more than ever necessary to prevent contact with glandered horses. Such horses have been known to give the disease to persons riding behind them or passing near them by snorting the matter from their nostrils into the air. All glandered horses ought to be destroyed. In Germany the conviction of the danger of this disease is so strong, that all horses proved to have come in contact with glandered horses are ordered to be destroyed. Not only can this disease be communicated from horse to horse, and from the horse to man, but cases have occurred in which those attending glandered individuals have become affected. The poison of glanders soon manifests itself. Mr. Turner inoculated two young donkeys, and in one the maxillary glands became tender on the second day, and the discharge took place from the nose on the third day, whilst in the second the glands became swollen on the third day, and the discharge took place on the sixth. Cases have been recorded in which the incubation of the poison must have taken at least three months. In the human being the poison has remained latent from two to eight days after exposure.

This disease in its acute form is very fatal. Of fifteen cases recorded by Rayer only one recovered. Of the treatment, therefore, little can be said as a matter of experience. The general symptoms in the latter stages are those of low malignant fever, and a stimulant plan of treatment is indicated. Cases have been bled and cupped, and the blood was buffed, but there is no reason to believe that the

bleeding did any good. In the chronic forms of the disease recovery is more frequent. The symptoms indicate the necessity of a generous diet. We add the following remarks by Mr. Finlay Dun, V.S., in the 14th vol. of the English Agricultural Society's Journal,' pp. 128, 129:"From their weak and unsound constitution, horses of a scrofulous diathesis are unusually prone to glanders and farcy-two forms of a disease peculiar (at least as an original disease) to the equine species. As has been already remarked, it is characterised by a specific unhealthy inflammation, identical in all important characters with the syphilitic inflammation in man. From the dire and loathsome nature of glanders, and the terror in which it is held, animals affected by it are never used for breeding, so that we have little opportunity of judging of its hereditary nature. There is no evidence (so far as I know) which proves it to be directly hereditary, but there is no doubt that the progeny of a glanderous horse would exhibit an unusually strong tendency to the disease. Though I am not aware of any facts proving glanders to be congenital, yet I think there is every probability that such is the case; for it is notorious that syphilis, the analogous disease in the human subject, is congenital, and often appears at birth in the children of women affected by that disease. Its ordinary predisposing causes are, many of them, hereditary: it is very prone to attack animals of a weak or vitiated constitution. It is emphatically the disease which cuts off all horses that have had their vital energies reduced below the healthy standard, either by inherent or acquired causes. Glanders is also sometimes caused by inoculation; is frequently produced in healthy subjects by mismanagement, as by insufficient food, want of shelter, and overwork; and often supervenes on bad attacks of influenza, strangles, diabetes, and other diseases which debilitate the system, or impair the integrity of any of its more important parts. These causes appear to possess the power of engendering in the constitution of the horse a peculiar poison, which, as it reproduces itself, and spreads to all parts of the body, gives rise to the characteristic symptoms of glanders, causing, sooner or later, a breaking up of the system, and a fatal prostration of the vital powers. This poison produces in the blood abnormal changes, which vitiate that fluid, and unfit it for healthy nutrition. From the irritant action of the morbid fluids passing through them, the lymphatic glands and vessels become inflamed, and lymph is deposited. This, however, being of an unhealthy nature, soon runs on to softening, which extends to the skin overlying the part, and ulcerating farcy-buds are formed. On the surface of the more vascular mucous membranes effusions of tubercular matter are also poured out; these take on an unhealthy inflammation, and degenerate into chancrous ulcers, which may generally be seen on the mucous membrane of the nostrils in most bad cases of glanders."

GLASS MANUFACTURE. Glass, one of the most beautiful of manufactured products, is a transparent, solid, and hard substance, exceedingly brittle while cold; but by the application of a high degree of heat it is rendered so flexible and tenacious that it may with the utmost facility be moulded into any form. It is so ductile while heated, that it may be spun into filaments of the greatest conceivable fineness; and these when cold are exceedingly pliant and elastic.

The

The time at which glass was invented is very uncertain. popular opinion upon this subject refers the discovery to accident. It is said (Plin. Nat. Hist.' lib. xxxvi., c. 26)" that some mariners, who had a cargo of nitrum (salt, or, as some have supposed, soda) on board, having landed on the banks of the river Belus, a small stream at the base of Mount Carmel in Palestine, and finding no stones to rest their pots on, placed under them some masses of nitrum, which, being fused by the heat with the sand of the river, produced a liquid and transparent stream: such was the origin of glass." The ancient Egyptians were certainly acquainted with the art of glass-making. This subject is very fully discussed in a memoir by M. Boudet, in the Description de l'Egypt, vol. ix., Antiq. Mémoires. The earthenware beads found in some mummy cases have an external coat of glass, coloured with a metallic oxide: and among the ruins of Thebes pieces of blue glass have been discovered. Sir Gardner Wilkinson adduces three distinct proofs that the art of glass-working was known in Egypt before the exodus of the children of Israel from that land, more than 3500 years ago. The manufacture of glass was long carried on at Alexandria, from which city the Romans were supplied with that material; but before the time of Pliny it had been introduced into Italy, France, and Spain (xxxvi., c. 26). Glass utensils have been found among the ruins of Herculaneum.

The application of glass to the glazing of windows is of comparatively modern introduction, at least in northern and western Europe. In the year 674 artists were brought to England from abroad to glaze the church windows at Weremouth in Durham; but even in the year 1567 this mode of excluding cold from dwellings was confined to large establishments, and by no means universal even in them. An entry then made in the minutes of a survey of Alnwick Castle, the residence of the Duke of Northumberland, informs us that the glass casements were taken down during the absence of the family, to preserve them from accident. A century after that time the use of window-glass was so small in Scotland that only the upper rooms in the royal palaces were furnished with it, the lower part having wooden shutters to admit or exclude the air. It may be presumed that this window gloss was of

home-make. The earliest manufacture of flint-glass in England was begun in 1557; and the progress made in perfecting it was so slow, that it was not until near the close of the 17th century that this country was independent of foreigners for the supply of the common article of drinking-glasses. In 1673 some plate-glass was made at Lambeth, in works supported by the Duke of Buckingham, but which were soon abandoned. It was exactly one century later that the first establishment of magnitude for the production of plate-glass was formed in this country, under the title of "The Governor and Company of British Cast Plate-glass Manufacturers." The members of this company subscribed an ample capital, and works upon a large scale were erected at Ravenhead, near Prescot in Lancashire, which have been in constant and successful operation from that time to the present day.

There are several distinct kinds of glass, which differ from each other in regard to some of the ingredients of which they are made, and in the processes of manufacture. The names crown, flint, cut, window, sheet, broad, spread, blown, cast, plate, &c., glass, are not very well chosen; but whatever be the names, the principal ingredients employed are silex or flint, and an alkali. The differences in the various kinds result from the description of alkali employed, and from the addition of certain accessary materials, usually metallic oxides. The form in which silex is now generally used in this country for glass-making is that of sea-sand, and eare is required to select those kinds which are free from foreign matters and impurities. The port of Lynn in Norfolk, and Alum Bay in the Isle of Wight, have long furnished the greater part of the silex used in our glass-houses. Flint-glass derives its name from the practice in former times of using flints calcined and ground in the manner now employed for making porcelain; but this has long been discontinued. Of late there has been some apprehension of a scarcity of sand suitable to the manufacture; and a good idea may be formed as to the importance attached to the purity of this chief ingredient from the fact that sand has been imported for the purpose from New South Wales. The alkali employed for making fine flintglass is pearl-ash, purified by solution and subsidence, in which process impurities to the extent of one-third of the weight are removed. Coarser alkaline substances are used for making inferior kinds of glass: the impurities even assist towards fusing the silex; but such alkalies all contain iron in some degree, and it is to the presence of this metal that the green colour of common glass is owing. Barilla and kelp were formerly the chief sources of the soda employed; but in recent years the carbonate and sulphate of this alkali have been obtained from common salt; either one alone, or the two combined, being chosen for different kinds of glass.

We shall now treat succinctly of the processes by which the principal kinds of glass are produced.

Flint Glass. This, known in other countries under the name of crystal, is the most generally useful, the most brilliant, and the heaviest description of glass. This last quality it owes to the large quantity of oxide of lead which it contains, and which is used sometimes in the form of minium, but more frequently in that of litharge. The metallic oxide acts as a flux, and promotes the fusion of the other materials at a comparatively low temperature. The greater density which it imparts gives to the glass a greater power of refracting the rays of light; and it is this quality which renders flint-glass of so much importance for optical purposes. Nitre in a small proportion is used for the destruction of any carbonaceous matter in the other ingredients; the oxygen which it gives out in the furnace further serves to maintain at their highest degree of oxygenation the metallic oxides that are present. Black oxide of manganese in minute proportion is also used to remove any foul colour that might otherwise remain through the impurity of the alkali used; its cleansing property occasioned this oxide to be known formerly under the name of glass-soap. Any undue proportion of manganese would impart a purple hue to the mass; and if any considerable quantity be used that colour will be deepened almost to black. When through inadvertence the glass has been made purple, the colour will be almost instantly discharged by thrusting a piece of wood into the melted mass. The cause of these changes is as follows:-The purple colour given by oxide of manganese arises from its being in a high state of oxygenation; the wood when thrust into the heated mass becomes speedily carbonised, and the carbon, combining with the superfluous oxygen, is driven off in the form of carbonic acid gas; if by the addition of nitre the quantity of oxygen is again increased, it will combine with the manganese, and restore the purple colour. It will be seen from these circumstances how much skill and experience are necessary for the due mixture of ingredients so as to produce glass of the best quality. The manufacturers of flint-glass are generally unwilling to disclose the precise proportions in which they employ the requisite ingredients; and it is probable that each has a favourite recipe of his own. One kind consists of 120 parts fine clean white sand, 40 well-purified pearl ash, 35 litharge or minium, 13 nitre, and a small (undefined) quantity of the black oxide of manganese. The French chemists recommend a much larger proportion of oxide of lead, but this is found to make the glass inconveniently soft. Where less metallic oxide is used, more nitre is required as a flux, and vice versa.

The ingredients, in whatever proportions selected, must all be intimately mixed before they are put into the crucibles or pots, which

dients are added until the pots are full of melted glass. A very strong and long-continued heat is necessary, not only for the perfect fusion and amalgamation of the materials, but also for the discharge of the impurities which they contain. The chief of these, known under the name of sandivir, or glass-gall, consists of salts existing in the alkali which have but small affinity for silex, and from their specific levity rise in the form of a white porous scum to the top of the crucible, whence it must be removed before it is volatilised by the excessive heat of the furnace. This glass-gall is used as a powerful flux by refiners of metals. When the whole of the impurities have been thus thrown off by the action of heat and are removed, and the glass, or metal, as it is called, appears colourless and translucent, the vitrification is known to be complete. The temperature of the furnace is then lowered by preventing the access of air until the glass loses a part of its fluidity, and assumes that pasty character which is the most convenient for the workmen; it being sufficiently consistent to be tenacious, but soft enough to yield to the slightest pressure without cracking or losing its tenuity. The material is usually brought to a perfect state of vitrification in about forty-eight hours from the first application of heat.

There is perhaps no process of manufacture which more excites the surprise and admiration of a stranger than that of fashioning flint-glass into all the various objects of convenience and ornament for which it is employed. To see a substance, proverbially brittle, blown with the human breath, pulled, twisted, cut, and then joined again with the greatest facility, never fails to strike with astonishment those who are unaccustomed to the sight. The tools with which all these operations are performed are of the most inartificial description, and do not appear to have received any improvement from the earliest records of the manufacture. Most articles in flint-glass, such as drinking glasses, cruets, decanters, phials, &c., are made by the combined processes of blowing, manipulation, and casting, in varying degrees. A square perfumery bottle may be selected as an example of one kind. The workman takes a long iron tube, and collects a little of the melted glass on one end of it, by thrusting the tube through the open door of the furnace into the mouth of the melting pot; this pasty glass is rolled into a cylindrical form on an iron plate, and is pinched at one place to form a neck. The glass is then thrust into a brass or iron mould, and the workman blows through the other end of the tube; the mould gives an external shape to the glass, while the current of breath hollows the interior. All this is done in less than half a minute. The mould, which consists of two halves hinged together, is opened;

Moulds for casting Flint-glass bottles.

the glass is taken out; it is detached from the tube by a touch with a piece of cold iron; it is taken up on the end of a heated rod by another workman; and by means of a few simple tools the neck and mouth of the bottle are finished. A claret-jug may be taken as an example of another large class of flint-glass manufactures. The workman collects a considerable quantity of melted glass on the end of his iron tube, which is raised to elongate it, rolls it into a cylin

method of obtaining some such effect as this was devised by Mr. Johnson in 1853. It consists in laying a piece of glass on another piece of a different colour; softening and uniting them by the heat of an enamel-furnace; stamping a device on the upper surface by a die; and then grinding away most of the upper glass-by which the upper colour presents itself as a device set or incrusted in the lower. The incrusted glass, or crystallo-ceramie, invented by Mr. Pellatt, consists in forming a small medallion bas-relief, alto-relief, or other article, of a kind of clay which has the property of expanding and contracting by changes of temperature just in the same degree as flint-glass; this is imbedded in a mass of red-hot glass; and when cooled, annealed, fashioned, ground, and polished, the glass appears with the device in the middle of its substance; the clay, under these circumstances, presenting an appearance almost exactly like that of unburnished silver. The gilding of flint-glass is effected by processes not differing much from that of porcelain. [PORCELAIN MANUFACTURE.] Two or three patents have been taken out for electro-gilding on glass: but this process has not yet come extensively into use.

Artificial Gems.-Before passing to the consideration of other kinds of glass, we may say a few words concerning the art of making imitative gems and precious stones, which resemble flint-glass more than any other substance. A transparent, fusible, dense glass, called paste or strass, is the basis employed. To make good strass is the primary work to be done. There are many recipes for producing it. One, by Loysel, consists in using pure silica, 100 parts; red oxide of lead, 150; calcined potash, 30; calcined borax, 10; and arsenious acid, 10. This mixture produces a glass of great brilliancy, much power of refracting and dispersing light (on which the flashing lustre of gems, whether real or factitious, so much depends), and a specific gravity not far different from that of the diamond; it fuses at a moderate heat, and acquires additional brilliancy when kept heated for two or three days. Diamonds are imitated by this uncoloured strass; and other gems by mixing this strass with colouring agents. For every different factitious gem, there are numerous combinations known; but a few examples will suffice to illustrate the general character of all. Amethyst: strass, 100 parts; oxide of manganese, 3; and oxide of cobalt, 2. Aquamarine strass, 4800 parts; glass of antimony, 30; and oxide of cobalt, 14. Avanturine: strass, 500 parts; scales of iron, 100; and protoxide of copper, 50. Beryl: nearly the same as for aquamarine, of which beryl is only a variety. Chrysolite: strass, 7000 parts; and calcined sesquioxide of iron, 65. Carnelian, or Cornelian; strass, 7000 parts; glass of antimony, 3500; calcined peroxide of iron, 875; and binoxide of manganese, 75. Emerald: strass, 7000 parts; carbonate of copper, 65; and glass of antimony, 7. Garnet: strass, 1200 parts; glass of antimony, 580; purple of cassius, 3; and binoxide of manganese, 3. Lapis lazuli: strass, 7000 parts; calcined bones, 570; oxide of cobalt, 24; and oxide of manganese, 24. The golden veins in this beautiful stone are imitated by painting in the composition with a mixture of gold-powder, borax, and gum-water, and then applying a gentle heat till the borax fuses. Opal: strass, 960 parts; and calcined bones, 48. Ruby: strass, 45 parts; and binoxide of manganese, 1; or in another variety, 1 part of topaz paste, which has turned out too opaque, with 8 of strass, fused together for thirty hours, cooled, and fused again in small pieces before the blowpipe. Sapphire: strass, 3600 parts; oxide of cobalt, 50; and oxide of manganese, 11. Topaz strass, 1050 parts; glass of antimony, 44; and purple of cassius, 1. Turquoise blue strass, 20 parts; and calcined bones, 1. There is a peculiar mode of producing imitative rubies and emeralds by the use of a kind of alum-glass, subjected to a long and elaborate series of processes; and another, by M. Gaudin, for producing imitative sapphires by an equally elaborate treatment of alum and sulphate of potash. There are other modes of imitating gems; but we need not notice them here.

Crown Glass.-This is one of two varieties of blown glass. It is made without any admixture of metallic oxide, and is both specifically lighter and much harder than flint-glass. Many receipts have been given for the production of this kind of glass. At the great works of St. Gobain, in France, the mixture of ingredients is said to be: fine white sand, 100 parts; carbonate of lime, 12; carbonate of soda, calcined, 48; clippings of crown-glass, 100; with minute portions of manganese and cobalt to correct impurities, and to remove the colour which those impurities would impart; they are not therefore at all times necessary. In England the ingredients are mostly sand, alkali, and slaked lime, in the proportions of 200 of the first, 330 of the second, and 15 of lime, to which is added about half the weight of the three materials in broken crown-glass, called by the makers cullet. The perfect fusion and refining of these materials are usually accom plished in about forty hours. Crown-glass is made by blowing, in the form of circular plates of 54 to 70 inches diameter. A quantity of glass in the pasty state is collected upon the end of a hollow iron tube, five feet long, similar to the tube used for blowing flint-glass, The lump of glass is then converted, by blowing through the tube, into a hollow globe of the requisite substance. This globe is flattened at the side opposite to the tube by pressing it upon a hard plane surface; a solid rod of iron having a small quantity of melted glass at the end is applied, and adheres to the centre of the flattened side opposite to the tube; the tube is finally removed by wetting the glass near the point of union, leaving a small circular hole. To arrive at this

stage the glass must have been several times re-heated, by placing it, when connected with the tube, within a small opening left for the purpose in the wall of the furnace. When transferred from the tube to the solid rod, called a pontil, it must be again heated in the same manner, and is then twirled round by the workman somewhat in the manner that a mop is twirled to drive off the moisture; with this twirling the softened material is continually driven off from the centre by the centrifugal force; the hole just mentioned expands, from a few inches to a foot or more in diameter, when suddenly, and in a most unaccountable manner, it flies open, and the whole substance is converted into a flat disc of circular form, and, except

at the centre, where it is attached to the rod, of a uniform thickness. This flashing of the glass as it is called, is one of the most striking and used for the conimonest purposes, such as glazing outhouses and the surprising things in the whole manufacture. The centre parts are poorer kinds of windows. As the shape of the tables or pieces of glass is circular, and as there is a bulb or bull's eye in the middle, it is impossible to obtain very large panes of crown-glass; and the differences of quality are so great and so uncertain, that the best are worth thrice as much per square foot as the worst. Nevertheless, there is always a brilliancy of surface upon crown-glass, which renders it valuable.

Sheet Glass.-This is another kind of blown-glass, which has become a very important article of manufacture in England within the last twenty years. Before that time, glass of a peculiar kind was imported, under the names of broad, spread, or German sheet-glass; but the sheet-glass of modern make is a French invention, and French work

the manufacture; the difficulties were at length mastered; and among other results, " Crystal Palaces were rendered possible. The process of making is from first to last very remarkable. The workman gathers up a quantity of the semi-molten glass on the end of a tube; rolls it on a concave block of wood to give it a cylindrical form; and then swings it completely round in a vertical circle, blowing through the tube repeatedly. A recess is formed in the floor of the building, to afford room for this swinging. Much bodily strength and great nicety are required in this operation. The hollow cylinder of glass stretches out by the swinging; but it must be so skilfully managed that the stretching may occur equally in every part, bringing the glass to one uniform thickness. The rotating before a fire, the blowing, and the swinging, are repeated until the proper thickness is attained, and the cylinder has attained the length of four, five, or even six feet. By a mode of causing the heated air within the cylinder to expand, the remote end becomes burst open; the tube is detached, and then the other end is expanded also. The cylinder, symmetrically shaped from end to end, is then laid down; and a diamond, fixed to the end of a long handle, is drawn along the interior, making a cut. The cylinder is placed in an oven, with the cut or fissure uppermost ; it gradually opens, and flattens down to a sheet on a very smooth surface. The sheet is rubbed smoothly and evenly with a piece of charred wood, until as free as possible from any irregularities; after which it is annealed in another oven. Such sheets, when first made in England, seldom exceeded 36 by 20 inches; but the usual size now is 47 by 22 inches; and some rare examples have been produced as much as 77 inches in length, requiring no less than 38 lbs. of glass to be taken up on the end of the tube. Although sheet-glass, thus made, is less brilliant and more undulating than crown, its available size is so much larger, that its use has in recent years become very extensive. It was with sheet-glass that Messrs. Chance glazed the Crystal Palace in Hyde Park in 1851; the glass was made in sheets 49 inches by 30, from cylinders more than 4 feet long by nearly 10 inches in diameter: each sheet was cut up into three panes, 49 inches by 10; and of these there were 300,000 in number, measuring 1,000,000 square feet, and weighing 400 tons. The Crystal Palace at Sydenham has since been glazed with the same kind of glass. Messrs. Chance have recently succeeded in devising a process for grinding and polishing sheet-glass, by which it acquires nearly all the beauty of plate-glass with a much less weight; it is much prized by photographers. The German, or broad-glass, above adverted to, is made by the cylinder process, like sheet-glass; but it is clumsily-fashioned, the cylinder is cut open by scissors, and is made to spread out on a layer of sand in the oven, which does not admit of the production of so much smoothness and regularity. Until 1836 the cylinders of sheet-glass were cut open by a piece of red-hot iron; but now a diamond is employed. Such of the Bohemian and Venetian decorated glass as does not belong to the flint-glass kind, is made by the cylinder process.

Plate Glass.-This is both blown and cast. The first-named process was alone employed in England until the year 1773, when castplate began to be made. Larger pieces can be made by this than by any other method. The manufacture is difficult and costly. The ingredients are chosen with the greatest care, and every possible amount of skill is brought to bear on the manufacture. The ingredients used are sand of the purest and whitest quality, and soda produced by the decomposition of common salt and lime: manganese and oxide of cobalt being added for the purpose of discharging colour. Soda is preferred to potash or pearl-ash because the glass that is made with it flows better when in fusion, a quality of much importance where large quantities are employed for the production of the same piece. The lime acts as a flux, and is used in proportions varying from 1-24th to 1-16th of the whole materials employed. Besides these ingredients, it is necessary to use a large proportion of broken plateglass or cullet. The following is one among many scales of ingredients: Lynn sand, well washed and dried, 720 parts; alkaline salt, containing 40 per cent. of soda, 450; lime, slaked and sifted, 80; nitre, 25; broken plate-glass, 425. It requires 40 hours' exposure to the full heat of the furnace to reduce the materials to the proper state of fusion and vitrification. When this is accomplished, the glass is transferred from the melting-pot, by means of copper ladles, to a large vessel called a cuvette, previously heated to a very high degree; when filled, it remains some hours in the furnace, to disperse the air that may have been introduced into the mass by the operation of ladling. When this effect has been produced, the cuvette is withdrawn from the furnace and taken to the casting-table, over the upper end of which it is raised and suspended by means of a crane. It is then thrown into an inclined position, by which the contents are allowed to flow out upon the table. The liquid glass is distributed by means of a roller over the whole surface of the table, bars of metal being placed at each side along its entire length, and across the bottom, in order to prevent the glass from running upon the floor. The casting of large plates of glass is one of the most beautiful processes in the arts: the large mass of melted glass, rendered in a high degree luminous by heat, exhibiting changing colours in the sheet after the roller has been passed over it. Previous to the casting, the table is placed with one end against the mouth of an annealing oven; and as soon as the plate is set, it is carefully slipped from the surface of the table to the floor of the annealing oven. When the oven has received as many

plates as it will contain upon its floor, the door is closed and its crevices are stopped with mortar or clay, to insure the gradual cooling of the plates. The plates remain in the oven during a fortnight, after which the ovens are opened and their contents are withdrawn. The plates are then squared by means of a glazier's diamond, then ground and polished, and when intended for mirrors they are silvered. In order to their being ground they are imbedded in plaster of Paris. To commence the grinding, powdered flint is rubbed steadily and evenly over the surface by machinery worked by steam power, the two sides of the plate being ground in succession. Emery powder is then substituted for ground flint, coarse at first, but finer afterwards, as the rougher inequalities of the surfaces are removed. The polishing is also performed by steam-machinery. The plates are firmly fixed upon large tables, and the polishing instruments, which are of wood covered with many folds of woollen cloth, having carded wool between each fold, are passed to and fro over the surface. The polishing substance used is colcothal, and oxide of iron which remains in the retorts after the distillation of acid from sulphate of iron; the two surfaces are polished in succession.

The novelties introduced within the last few years in the plateglass manufacture are as numerous as those which bear relation to sheet-glass; they have had the effect of cheapening the price and increasing the attainable size of the plates. Messrs. Swinburne, a leading firm in the glass trade, have it recorded in their books that their charge, in 1771, for a plate measuring 50 inches by 40, was 611. 38., whereas the price in 1856 was 41. 48. Some of the recent inventions relate to the form of the furnace and melting pots; some to the mode of tilting over the molten metal; some to the form and construction of the casting-table; and some to the mode of effecting the difficult operation of transferring the plate of glass from the table to the annealing oven. A few years ago Messrs. Hawks & Crawshay made for Messrs. Swinburne a casting-table of extraordinary size; it was a solid mass of iron 18 feet 4 inches long, 10 feet 10 inches wide, and 74 inches thick, weighing 26 tons. A planing-machine was expressly constructed for planing and smoothing this iron surface. When the large plates of glass are annealed, the grinding and polishing begin: these processes, like all else, have been recently made the subjects of much inventive skill; but their details need not be noticed here. It is an interesting fact, connected with the history of the plate-glass manufacture, that the machinery constructed by James Watt for the Company in 1788 was still in existence, at the Ravenhead Works, and even in use, in 1858.

Bottle Glass.-This is the commonest kind manufactured, the alkali employed being the cheapest that can be procured, with the addition of a portion of lime to assist fusion. Considerable manufactures of bottleglass are carried on at Newcastle-upon-Tyne, encouraged by the low price of the fuel (small coal) which is used in the furnaces. The ingredients are usually nothing more than lime and sea-sand, the latter article having been frequently wetted with sea-water, and allowed to dry, in order that the salt may be allowed to deposit itself in the sand; the soda contained in the salt is the only alkali, properly so called, that is used. Or, another mixture is, Tyne-sand, lime, and the refuse of the soap and alkali works. Bottle-glass is fashioned by blowing, much in the

Bottle-glass making.

same manner as flint-glass, but with the addition of a moulding process. The description given in a former paragraph of making a flint-glass perfumery bottle will suffice to convey a notion of the mode of making wine and beer bottles, pickle and oil bottles, &c.; except that the latter are made with much less nicety. Four men can make about a hundred beer bottles in an hour. There is a greater weight of coarse green bottle-glass made in England every year than of all other kinds of glass combined.

Štained or Coloured Glass.-Coloured glass is more easily produced than colourless, seeing that many niceties in the choice and management of ingredients are necessary to remove all tint from the glass. Nevertheless, to produce a particular colour is an art requiring much skill. As in the instances of enamels and artificial gems, the colours are mostly produced by adding metallic oxides or chlorides to the