It is not our purpose to trace the history of window glass, but it would seem that, according to the best documentary evidence, before the fourteenth century but little if any white glass was used for windows.

According to M. Le Vieil, painting on glass was discovered in the twelfth century. The first windows are said by him to have been painted for the St. Denis Abbey. This, however, appears to be an erroneous statement, for several monuments had been decorated with painted windows before this. Among others the Abbey of Leroux, in Anjou, France, dating from 1121; in Bavaria, in the Abbey of Tegernsee, where window frames are preserved dating from the tenth century. Glass painting, with vitrifiable colors, according to several authors, was discovered about the tenth century.

In Europe window glass is made in two ways, crown and cylinder glass. Crown-glass making is almost abandoned, with the exception of a few factories in England; it is an awkward and unprofitable way of manufacturing, and is not, I believe, practiced anywhere in this country. Cylinder-blowing being more economical and producing a better quality of glass, this method has been adopted all over the world. The Venetians and Bohemians blew cylinders for the windows of the twelfth and thirteenth centuries. Cylinder-blowing was introduced in France from Bohemia in the beginning of the eighteenth century.

France now manufactures a large quantity of window glass, one factory alone, “La Compagnie des Verreries de la Loire et du Rhône,” producing annually 590,000 square yards, and 89,000 yards of colored glass. In the north of France 25 to 30 furnaces of 8 pots produce from 4,500,000 to 5,000,000 square yards. The annual production, according to the official statistics of 1873, is put down at $4,400,000; for 1878, $3,000,000. In France, as in other countries, glass manufactories are to be found mostly near the coal fields.

Belgium has 60 window-glass factories, with 213 furnaces, containing each from 6 to 8 pots. These factories are mostly located near Charleroi and Jumet; a few, however, are to be found near Mons. Owing to the general commercial depression now existing, about one-third of these factories are idle. The annual production, notwithstanding this reduction, has fallen off but little, owing to gradual improvements which have been introduced in the methods of working and

in the construction of furnaces. These improvements have increased the production from 20 to 25 per cent., with the same running expenses of a few years ago.

The annual production in 1877 may be put down approximately from 175,000,000 to 185,000,000 pounds, say 18,000,000 or 19,000,000 square yards. Nine-tenths of this production are exported. The highest figures in the exports were, in 1874, 177,400,000 pounds; in 1875 the figures fell to 164,250,000 pounds; in 1877 the exportation still reached 163,000,000 pounds. These figures speak highly in favor of the low prices and the good quality of Belgian glass, and are an acknowledgment of the great resources of that country for glass making. Would that this country, with her equally wonderful resources, could make as good a showing.

The following is given as the average composition of French window glass:

Arsenic is sometimes added in order to refine the glass; this substance does not remain in the glass, but is vaporized and passes through the mass in the shape of gas, stirring the metal and thereby refining the glass. It is preferable, however, not to use arsenic, but to use finely pulverized and sifted materials. In Bohemia a substitute is used for arsenic; it is simply a potato put at the end of an iron bar and plunged into the mass. A green stick of wood also answers the same purpose, both producing watery vapor which escapes through the metal.

Most glasses have a greenish tinge, owing, it is thought, to the use of sand more or less ferruginous. Glass made with potash is freer from this coloration, but owing to the higher price of potash and the hardness, and difficulty in working, this glass it is now but little made. The green coloration is usually corrected by a small quantity of bioxide of manganese. This body should be as pure as possible, since it is a strong coloring element, turning glass to rose color, purple, and even black, according to the quantity used; consequently, it is always used in very small proportions as a corrective. I have also shown that the use of manganese should be dispensed with whenever it is possible, as glass containing it while under the action of sunlight in course of time acquires a purple tint.

In France and Belgium pots usually contain from 1,000 to 1,200 pounds of glass. In England they are much larger, holding as much as 5,000 pounds. Furnaces usually hold 8 pots. It is customary in some factories to make pots very thin and replace them regularly at the end of the week, instead of making them of a great thickness to prolong their life. This system has advantages. A thin pot will allow the heat to penetrate the mass of the metal much more readily than one with thick sides. It is also very frequently the case that when broken pots are removed from the furnace, and the hands are at work, the rush of cold air is very apt to break other pots. This regular change of pots is of course only applicable in factories where melting and blowing is completed every twenty-four hours. The batch is put into the pots in three different times — seven hours being allowed for melting the first charge, four hours for the second, and three hours for the third. The mode of working is similar to that followed in this country, with the exception that many manufacturers work the glass in the melting furnace instead of blowing from an additional furnace, as is the custom in England and in some places in this country. The question of an additional furnace with French and Belgian manufactures is one of fuel, but where coal is in abundance it is obviously a plan so superior to use a separate blowing furnace that I am surprised it is not more generally adopted. One blowing furnace maybe used for two melting furnaces, and by using it continuously the extra expense of fuel is not proportionately so great as when the work is intermittent. It is also obvious that work can be performed in a less crowded state of the workmen; the melting furnace can be regulated much better for the different degrees of heat required; the metal may be emptied at once from each pot in succession; in a word, as Bon-temps expresses it, “Every manufacturer who does not adopt this system will be obliged to cease making window glass.” A workman usually blows during 20 hours, and averages from 16 to 17 cylinders per hour, making sheets of 22 x 26 inches.

I shall not describe here the tools used for blowing window glass; I found nothing new. The same tools used for years are still to this day in existence. Nor shall I describe the method followed in blowing cylinders, as it is practically the same as in this country. In Belgium, in some factories, the handling of glass is rendered lighter by the use of a small truck running upon rails; upon this truck the blow-pipe is rested, relieving the workman from the

weight of the glass. In Bohemia, where looking-glasses of large sizes are blown, the workmen use levers, cranes, props, and other mechanical means. Some manufacturers in Belgium split the cylinders with the diamond. A long wooden rule is laid lengthwise inside of the cylinder, a diamond fastened at the end of a long stick is made to travel forward while held against the rule, thereby causing the cylinder to be split in the middle longitudinally.

Flattening ovens.

In Europe the usual style of compartment ovens, with flattening, cooling, and piling-up sections, is still somewhat used. The flattening stone, as usual, is carried by a small truck running on rails. An improvement in flattening ovens has been made by M. Segard, of Anzin, France, by which the quantity of glass flattened has been increased, 600 cylinders being flattened in 24 hours. The system consists of two stones carried on carriages running on rails arranged on different levels, so as to enable one carriage to pass under the other. The glass is first flattened upon one of the stones, then pushed into the cooling oven; the next stone is now used for a second cylinder, and the first stone is returned to its original position by passing under the other one. The operation is repeated for every sheet flattened. This system, although economical, is subject to the breaking of the stones when the carriages are raised to pass over one another.

In another style of flattening ovens the cylinders are introduced into a compartment where they are heated, then flattened upon a stone carriage; the carriage is then pushed into another compartment at the head of the leer, and from thence the sheet is pushed upon iron bars countersunk in the masonry of the leer floor and laid lengthwise; these bars are connected together at both ends, and slide upon rollers laid in the countersunk masonry. Through a system of balanced levers the bars can be raised out of the gutters where they are kept below the surface of the floor, and in so doing the sheets of glass are raised from contact with the floor. While in this position the bars are pulled forward a sufficient distance to make room for a new sheet. This operation, being repeated as often as necessary, finally brings the sheets to the end of the leer, after having been gradually cooled in a better manner and more rapidly than by the usual method. It will be observed that after each sheet has been brought forward the bars are lowered on the rollers and returned to their original position. This oven

contains only nine sheets, which reach the end of the leer in twenty or thirty minutes, instead of seven or eight hours with the old system. Glass annealed in these furnaces can. be cut more readily and seems to have been cooled more uniformly on both sides, owing to the periodical lifting of the sheets, and the risk of breakage in cooling is considerably decreased. These ovens, moreover, cost much less and are smaller than the old-style ones; they also show a notable saving of fuel.

The well-known furnace with rotating stone and compartments in connection with a leer are also used successfully.

Another description of flattening oven has also been introduced in France of late, but it is principally used for baking colors on enameled glass. It has been recommended, however, for window glass. This oven is built in the shape of a leer, with compartments attached for heating and flattening the cylinders. The flattening compartments contain the usual flattening stone mounted upon a carriage traveling back and forth upon rails from the heating to the flattening chamber. The leer contains a number of rollers mounted on shafts placed diagonally across and near enough to one another to give a sufficient resting support for the sheets of glass. These rollers, by suitable gearing, receive a slow rotary motion. The operation is as follows: The cylinder is introduced into the heating chamber, then placed upon the stone when properly heated. The sheet is now flattened and the stone-lined carriage pushed into the next chamber opposite the mouth of the leer. The workman, by means of a suitable tool, places the sheet upon the first of the series of rollers; the rotary motion imparted to them gradually and slowly carries the sheets to the end of the leer, where they are withdrawn. It will be seen that the action of the oven is continuous, simple, and possesses, besides the advantage like the preceding one described, of allowing both sides of the sheet to be equally cooled. Whether the large number of rollers required to traverse the whole length of the leer may not be a source of trouble to keep them in order experience alone can determine.

Since sheets of glass, however well flattened and annealed they may be, have a tendency to show iridescent colors, it is customary to plunge them, as they come from the leer, into water containing a small quantity — about two Per cent.— of hydrochloric acid. After this washing and drying, the glass becomes less subject to the action of the air.

Fluted glass.

A great deal of this glass is used in Europe. Owing to the semi-circular flutings pressed upon it, the interior of apartments fitted with this glass cannot be seen, but yet allows a free transmission of light; it is therefore much used for door panels and window panes. This glass is prepared by blowing a pear-shaped piece, which is then introduced into a brass mold having a number of deeply-channeled flutings inside. It is now blown and receives the imprints of the flutings, and the cylinder is finished as usual, being careful, however, to impart no rotary motion to the blowpipe, as by so doing it would distort the flutings. The expansion and lengthening of the cylinder reduces the depth of the flutes, but the mold is so calculated as to leave sufficiently deep indentations after the cylinder is finished.

Enameled glass.

This branch of the glass-maker’s art is carried to a great state of perfection on the Continent of Europe, and fusible colors are made by several celebrated manufacturers. It is not my purpose to enter upon a minute description of its manufacture, but I believe the superiority of the work turned out by the European manufacturers is due to the excellent quality of fusible colors and enamels manufactured for the trade. The means employed for applying the colors and the baking are simple and well known. I regret to say, however, that so far we are nearly entirely indebted to Europe for our fine colored enameled glass, as our manufacturers have not yet produced anything but the plain gray enamel with success.

Colored sheet-glass.

The most beautiful colored sheet-glass is made by the French and Belgian manufacturers, such as sheets composed of two layers or coats of glass, white and colored, and in some instances sheets made of white glass and covered over with as many as four different layers of colored glass, put on very thin and equal in thickness on the whole of the surface. For the coloration of this glass, as for all colored glass in general, the oxides of the different metals are used. For blues the oxide of cobalt, or safre. For the different shades of blue, violet-blue or celestial blue, different proportions of cobalt. For a very light shade of blue for spectacles a mixture of cobalt and red oxide of iron; London smoke is obtained by a mixture of the oxides of copper, iron, and

manganese — a black is produced by increasing the proportions of these three oxides. Purple glass has for coloring element oxide of manganese. A glass so colored and made with soda gives a purple shade, edging on the red, while a potash glass will give a bluish purple. This color is made of a deeper blue by the addition of cobalt. The brown-purple is made with a mixture of oxide of manganese and oxide of iron. The purple of the ancients can be perfectly imitated with a mixture of oxide of manganese and red oxide of iron.

Yellow. — A mixture of oxides of iron and manganese is used. To get this color with more facility charcoal in the shape of wood sawdust is substituted. By increasing the quantity of sawdust an orange color is produced; with still larger proportions it may turn to brown and sometimes even red or black. All books state that antimony gives a yellow coloration to glass, but it would seem that this is erroneous, for pure antimony does not color glass at all. The sulphur contained in the antimony is supposed to be the coloring agent. Glass is also tinted yellow by applying to its surface a mixture of ocher and sulphate of silver, and baking it in an oven.

Green. — For grass-green a mixture of black oxide of copper and oxide of iron is used. The same color may be obtained by replacing a part of these oxides by one-third of their weight of bichromate of potash. By using these substances and adding an oxide of cobalt a blue-green is obtained. Yellow oxide of uranium added to the oxides of iron and copper gives a yellow-green.

Red or ruby. — This color is always used as a coating upon white glass, and is obtained with the brown oxide of copper, the oxides of lead and tin, scales of iron, and borax introduced into the batch and melted. The glass when melted is dipped out with a spoon and broken or ground; brown oxide of copper, oxide of lead, oxide of tin, and borax are again added and melted anew. The color of this glass is not developed until it has been repeatedly heated; in cooling it becomes perceptible. This glass requires particular care in its preparation and blowing. I believe but little of it is made successfully in this country.

Opal. — This glass is produced by adding calcined bones to the metal or batch; it is much used for gas and lamp globes, clock dials, etc. Pure cryolite has also been used for the manufacture of opal glass, and a factory was started a few years ago in Philadelphia to make this glass, under the name of hot-cast porcelain. The name was unfortunate,

as the glass was not cast, but was pressed and blown. This misnomer, with other reasons — the principal one, perhaps, there being no economy in the use of cryolite — carried the establishment under. Our manufacturers, however, still continue to use it with good effect, but principally in the making of hollow wares. The Philadelphia factory used the following ingredients:

The dirty, discolored oxide answers very well for this purpose. Fluor spar has also been employed for making opal glass.

Round, oval, and square shades.

These shades are used in large quantities in France for protecting clocks, artificial flowers, etc, They are made in a very similar manner to the cylinders blown for window glass, with the exception that the glass must be of a very even thickness all through. This requires especial attention in blowing and reheating, in order to distribute the glass evenly throughout the mass. Oval cylinders are first blown round, then passed between two parallel pieces of wood coupled together, having the upper ends cut wider at the top. For square shades, four pieces of wood are used instead of two. Several precautions must be taken in this peculiar branch, and expert workmen are particularly necessary. Round cylinders may be cut without being annealed in ovens or leers, but oval and square shades, owing to their forms and uneven cooling of the several parts, must first be annealed before they are cut, or else, on the mere contact of the thread of hot glass to separate the bottom, they are liable to fly to pieces.

Glass furnaces.

Europe has gone much ahead of this country in the use of gas furnaces, and they have in every instance proved quite economical. The question of fuel — one of great importance in Europe — has had the effect of stimulating their adoption, and wherever they have been put up a considerable saving of fuel has been the result. France, Belgium, and England have been the foremost in adopting them. It is to be regretted that, so far, in this country but few gas furnaces have been put up. Aside from their economy, gas furnaces offer many advantages; the heat is under easier control, and may be graduated from an intense degree when

melting to one sufficiently low to work the glass. Some of the objections urged against the Siemens furnace are their great cost, difficulty of management, liability to explosions, and the necessity of keeping skillful and experienced persons to manage them. The gases, traversing in pipes from the generators to the regenerators, are constantly condensing in tarry matter, which must now and then be burned, an operation which is exceedingly disagreeable to the neighborhood, owing to the dense smoke produced. Notwithstanding these and other minor drawbacks, the great economy of 40 to 50 per cent, in the fuel, in some cases 75 per cent., and the great cleanliness and easy management of the heat, ought to be by themselves sufficient inducements for their general adoption.

Though these furnaces have been used quite extensively in metallurgy with great success, in this country we find but three glass-houses using them, viz: Burgin & Sons, of Philadelphia, the Lenox Plate Glass Company, and the Crystal City Plate Glass Works. In Europe we find quite a number of firms using them: in England, five plate-glass works, twelve window and bottle houses, and one flint house; in France, seven plate works, ten window and bottle works, and nine flint factories; in Germany, three plate works, eight window and bottle houses, and twelve flint works; in Belgium, four plate works, one window house, and one flint factory. These furnaces have also been introduced in Russia, Portugal, Hungary, and Austria.

Recently, a new system of gas furnace, without the regenerating principle, has been introduced among European manufacturers. The Boëtius furnace is much simpler in construction than the Siemens. The gas generator is somewhat similar to that of Siemens, but the gases, instead of passing through regenerators, are conducted directly to the furnace with a sufficient quantity of air, and there ignited. The air, by passing through passages under the bottom of the furnace, serves to cool the bench, and thereby receives a certain degree of heat extracted from the hot bricks. The furnaces do not cost as much to construct as a regenerating furnace, they are easy of management, and the heat can be readily regulated. With a few changes, an ordinary open fire-furnace can be altered into one of the Boëtius system. They possess all the advantages of the Siemens furnaces, with the exception that the economy of fuel is not so great. An economy of 30 per cent, is claimed, and even more with fuels of inferior quality. I am fully convinced of the advantages and convenience of gaseous fuel, and think the day is not far

distant when gas will be used not only in the melting furnaces but also in the annealing furnaces, leers, and pot-arches, as well as glory-holes; in fact, wherever fuel is used.

Many other styles of gas-generating furnaces are used in Europe, such as the Thomas & Laurens generator, using peat or wood; the Beaufume system, applied principally to generating steam; the Ten Brink, also applied to locomotives and steam-boilers, vaporizes from nine to ten kilograms of water per kilogram of bituminous coal, and is perfectly smokeless. These different systems, with suitable modifications, can be applied to glass furnaces.

M. Émile Gobbe, of Aniche, France, exhibited a model of a furnace showing a combination of coke and gas furnace, with which it is claimed an economy of 70 per cent. is obtained, owing to the fact, it is said, that all the coke made can be sold to metallurgical establishments. This furnace has been applied to two glass-houses in France, but is yet under trial, and no definite results have been obtained.

I also wish to call attention to a furnace which has been introduced in this country by the Société Generale de Métallurgie of Paris. These furnaces are built upon the Ponsard system, consisting of the usual Siemens generator or a hot-air generator. In the latter case the grate is suppressed and the coal is held in a fire-brick basin. The gas coming from the generator rises to the fire-chamber of the furnace, but before combustion takes place it is mixed with a sufficient proportion of hot air coming from the regenerators. The heat escaping from the fire-chamber after having done its work is conducted to a regenerator under the furnace, made somewhat in the same style as the Siemens. Instead, however, of one of the regenerators receiving the gas from the generator and the other the air to be mixed in the furnace, and having four regenerating chambers, the Ponsard system uses but one chamber. This regenerating chamber is made up of a number of passages adjoining one another, one series of which receives the hot gases after combustion and the other receiving the air to be heated by the absorption of heat from the adjoining hot canals. This system is therefore continuous, and simpler than the Siemens. It is claimed that such a regenerating furnace will last one year in a glass-house; some have been known to last three or four years when applied to other purposes than glass-making. The regulation of gas and air is under perfect control, and can be graded as circumstances require. This system is now in operation in two melting furnaces and one annealing oven in France. An economy

of fuel from 30 to 70 per cent. is claimed by their use. As these proportions are so very wide apart, it would be interesting to know why such difference exists. Messrs. W. Sellers & Co., of Philadelphia, Pa., proprietors of the Edgemoor forges, write to the inventor that the system applied without grates works admirably with anthracite. The cost of these furnaces is said to be but two-thirds of that of the Siemens patent.

In the Austrian section M. Rosenegger, of Innsbruck, Tyrol, exhibited the plan of a new gas furnace used in his factory. A gas generator furnishes the gas, which is conducted by suitable passages to the fire chamber of the melting furnace. The gas in its passage to the fire chamber is met by a current of heated air blown through iron pipes. The gas and air are regulated by suitable valves so as to insure a properly proportioned mixture. After combustion in the furnace the hot gases escape through an iron pipe which leads to a drying oven for drying sand, cullets, etc. Whenever this drying oven is not used, the heat, before escaping to the outside air, is allowed to go still further and enter another oven for drying wood, peat, etc., used as fuel. The hot air supplied for mixing with the gas is derived from a current of cold air blown into the chamber where the iron pipe for the exit of the hot gas is laid. This cold air, coming in contact with the highly heated pipe, absorbs the heat from it and, by means of other pipes, is conducted to a suitable channel, where it mixes with the gas. M. Rosenegger, the manager of the works, has these furnaces in operation for the manufacture of plate glass, and makes about 6,000 square meters of plate monthly. This furnace appears to be a simple combination of gas and hot air under pressure, but it is to be supposed that the iron pipes, being under the influence of a very hot temperature, must rapidly be destroyed by oxidation. The inventor, however, asserts that it gives entire satisfaction.

The difficulty of obtaining good homogeneous pots, and the serious losses experienced by their breaking in the furnaces, have led inventors to devise furnaces with chambers and compartments instead of pots. Prominent among these furnaces is that of M. Fred. Siemens, of Dresden, who has applied it in his bottle factory. This furnace is constructed to take advantage of the increase of density glass acquires as it becomes more melted. It is composed of two large chambers, separated in the middle by a wall. In the first compartment the batch is put, and as the glass, under the action of the gaseous fuel, commences to melt it flows

through a passage left open in the separation wall and reaches the second chamber. Directly after leaving this chamber it passes over a low wall built across the furnace; in so doing it is exposed in a very thin layer to the action of the heat, and rapidly becomes quite liquid. The glass now continues its course forward, and, reaching a third wall having an opening at the bottom, it gradually reaches the front of the furnace or chamber, from which it is drawn for working. Thus is the operation of melting and working glass made continuous. The heat is regulated in each chamber to suit the purposes required. The layer of glass does not exceed 16 inches in thickness; the glass is therefore more accessible to the heat. These furnaces, including the gas generator, cost about $3,000.

Applied in Europe to bottle-making, this system has given satisfactory results, but in the manufacture of window glass it has not yet proved so successful. So long as cullets or broken glass alone are used, the glass is of suitable quality; but as soon as batches are introduced the glass becomes grainy and lumpy. These defects are attributed to an imperfect refining and to the wear of the fire bricks, which are rapidly cut away and the pieces mixed with the glass. The duration of the basins, so far as experimented, has not exceeded three months. Window glass made in these furnaces was shown in the Exposition, but it appeared to be of a very imperfect quality. Should these defects be remedied, as they probably will be, these furnaces offer so many advantages and secure such an economy in fuel — at least 50 per cent. — that it would be unwise to condemn them at present.

MM. Chagot, of Blanzy, France, bottle manufacturers, constructed a gas furnace to do away with pots, and substituted a tank in their place. This furnace is 22 feet long, 6œ feet wide; the tank is 18 inches deep, and is capable of melting 26,400 pounds of metal at each operation.

Other styles of furnaces have been proposed, with tanks and gas generators, by M. Flamm, of France, for the manufacture of plate-glass, with what success, however, I have not been able to ascertain. Should suitable furnaces be devised to do away with pots, they will be welcomed by most of the manufacturers, who have been under the domination of the autocrat of the glass-house, i.e., the pot-maker.

In connection with the question of gas for fuel, I think it surprising that, with the abundance of liquid fuels we have in this country, no one has yet applied our petroleum successfully in glass furnaces. From recent experiments

made in Europe it has been proved incontestibly that with suitably devised furnaces this fuel is capable of producing a great heat and a marked economy. I have heard recently that petroleum has been successfully applied to the manufacture of iron in the oil region of Pennsylvania. If this is successful with iron, why should it not be with glass?

M. Audouin, a French engineer, with a very simple apparatus for burning heavy oils of petroleum, consisting simply of an injection of oil mixed with air, succeeded in evaporating 12 to 15 kilograms of water per kilogram of oil burnt.

M. Ste. Claire Deville, the celebrated chemist, starting upon the idea of M. Audouin, devised an apparatus which he applied upon a locomotive on the “Chemin de Fer de l’Est.” The fire box contained a cast-iron grate cast in one piece, the bars of which were set in front of the fire box and were quite short; the upper part of the bars were of concave, semi-circular form. Two fire brick fire bridges were built, one in front and the other back in the fire box. The whole fire box was lined with fire bricks. Air was admitted to the fire box between the grate bars as usual; the quantity admitted was regulated by means of a door. The operation is as follows: The oil arrives at the short grate bars by means of properly arranged pipes in front of the fire box, and is conducted by the concave gutters; coming in contact with the heated fire box, it is vaporized and mixed with the air which penetrates between the bars. With this simple arrangement a good combustion was obtained, and the locomotive upon which the apparatus was mounted continued to run for 2,300 miles on regular trains without stoppage. The result of the experiment showed an evaporation of 10.9 kilograms of water, while the best agglomerated coal bricks only evaporated 7.9 kilograms. These experiments were carried on with heavy tar oil from the Paris gas works.

In other experiments by M. Ste. Claire Deville, with a carefully prepared apparatus, the evaporation of water with heavy Pennsylvania petroleum reached 15.3 kilograms per kilogram of petroleum, and with ordinary petroleum 14.14 kilograms, very nearly double the amount obtained with bituminous coal. In all furnaces using petroleum it is essential that the vapor of petroleum and air should be thoroughly mixed before combustion is reached. An increase of pressure and the heating of the air have also a marked economical result.

In conclusion of this chapter on furnaces I wish to say that I have the assurance of the managers of one of the largest iron mills in this country that metallurgy at the present day could not be carried on successfully and economically without the assistance of gaseous fuels. I hear with pleasure that a few of our glass manufacturers have already introduced gas furnaces, and the day is not far off when they will supplant the old direct-fire furnaces entirely.

Bottles.

This branch of manufacture, as carried on in Europe, differs somewhat from the others in regard to the construction of the furnaces. The materials used are required to be previously heated before they are introduced into the melting pots of the furnace. These furnaces are, therefore, constructed with upper chambers placed at each side of the furnace, and are heated by the waste heat. The furnaces are rectangular, and similar to those used in making window glass. The batch being properly mixed is introduced into the upper chambers and heated for about twenty-eight hours. Care must be taken to regulate the heat so as to prevent partial fusion, or else the cakes formed in fusing would require to be broken up. The mass upon the furnace bottom is occasionally raked and turned over with suitable iron rakes. The materials entering into the composition of the glass being very crude, if they were introduced all at once into the pots would swell up and run out. It has been the practice, therefore, to heat these materials previously, although this operation adds to the cost of the glass.

A furnace in France generally consumes about 374 pounds of coal for every 100 bottles of 28.80 ounce weight, or 1,320 pounds of coal for 220 pounds of bottles.

The operation of blowing the bottle is very simple. A piece of glass is gathered upon the end of a hollow pipe, the workman blows through it, and gradually, by rolling and blowing, brings the lump of glass to a proper shape. The roughly-shaped bottle is now introduced into a mold — generally of iron — and by means of an air-compressing piston the glass is made to fit the mold tightly, and when taken out has the shape of a bottle. This mold is made in many instances to simply shape the lower part of the bottle, and is of metal or clay. The workman withdraws the bottle from the mold, pushes up the bottom as in champagne bottles; it is now detached from the blow-pipe by chilling and cracking the glass in applying a cold iron to its surface. The bottom of the bottle is now put into a spring

tool fitting it; the neck is reheated and properly shaped with a pair of pincers, fitting the inside and outside of the neck, provided with properly shaped forming blocks.

This method of working is still largely followed in Europe for blowing bottles, especially those used for champagne in wine, as they are considered stronger when blown in this manner, rather than in a mold forming the whole bottle. Of late, however, the use of metallic molds forming the whole bottle, is extending rapidly. By the use of these molds a uniformity of contents is secured for each bottle, and is, therefore, a security against more or less unscrupulous dealers. I do not see why bottles properly molded should not be as strong as blown bottles, if the conditions of respective temperatures of the mold and bottle are properly observed. The operation of blowing in a whole mold is certainly more expeditious than with the use of a mold shaping only a part of the bottle. I believe a whole mold is generally used in this country. The bottles having been molded or blown, are carried to the leer or annealing oven, in which they are slowly cooled in the same manner as with table and other wares.

The materials used in making glass for bottles should be as cheap as possible; transparency not being a requisite, cruder materials may be used than for other glass. Manufacturers should, therefore, study the materials they have the nearest at hand, and use them in preference to those they would have to bring from a distance.

The materials used in making bottle glass do not differ materially from the following:

This Rhône sand contains iron and about 20 per cent, of calcareous matter.

France produces annually about 100,000,000 to 120,000,000 bottles, representing a value of $4,000,000. The exportation of bottles is about 59,000,000 pounds. The price of bottles varies from $2.50 to $3.50 per 100 bottles of 21 ounces to 2.20

pounds. Champagne bottles, having to stand the pressure of the gas contained in the wine, are sold higher; they range from $4.60 to $5.60, according to quality.

Belgium manufactures quite a large quantity of bottles, but the quality is said to be inferior to those made in France and Germany.

In 1872 Belgium exported 7,568,000 pounds of bottles, while the importation was only 1,377,000 pounds. Since that time the exports have decreased sensibly, and in 1877 they only amounted to 1,775,000 pounds, while the imports increased to 3,476,000 pounds. Of the 12 furnaces which were then in operation but 5 are now running. This shows a striking decrease, which is attributed to the neglect of the Belgian manufacturers to adopt the recent improvements in furnaces and the new methods now in operation elsewhere. It is an uncommon thing for the Belgian manufacturer not to be in the van of progress, and I scarcely know how to account for the apathy of the bottle-makers while the window-glass, hollow-ware, and plate-glass makers have shown such ability to maintain themselves up to the times.

Germany and England also manufacture a large number of bottles, but I could procure no data to lay before my readers. What little was exhibited in the English section appeared to be of good quality.

Of demijohns, which are usually made in bottle factories, I shall say but little. They are simply larger bottles, and the manner of blowing them is very similar to bottle-blowing, with the exception that the neck is not finished as in ordinary bottles, but is simply detached from the blow-pipe and smoothed with a file.

Table and other wares.

Of all the branches of glass manufacturing, that of making table ware and ornamental articles is incontestably the most interesting and attractive. It requires a varied knowledge, a taste for designing, a knowledge of mechanical means and appliances, be it in pressing, molding, blowing, cutting, engraving, or decorating. The variety of goods is infinite, each new article frequently differing materially from any other made heretofore. In fact, a glass manufacturer in this branch can only hope to reach success by ceaseless and watchful attention. The low cost of an article is not a sufficient guarantee to secure sales unless it is accompanied with a tasteful designing. Economizing appliances should also be adopted at once, if found to be really such, for, in this age of machinery, no one can hope to hold supremacy

{Glass-study note: Remainder of paragraph was on page 361}

unless he provides himself with the most perfect tools and devices.