Among the borough's manufactures are stoves and furnaces, malt liquors and silk.
These small furnaces are frequently arranged for direct coal firing, but regenerative gasfired furnaces are also employed.
There are blast furnaces, iron foundries, engineering works, iron ship-building yards, extensive saw-mills, flour-mills and a manufactory of "blue and white" pottery.
The Monteponi Company smelts its own zinc, but the lead is almost all smelted at the furnaces of Pertusola near Spezia.
The first steel plant in the southern states was established at Birmingham in 1897; in 1902, at Ensley, one of the suburbs, there were 10 furnaces controlled by one company.
There are smelting furnaces in several districts, as at Alfreton, Chesterfield, Derby, Ilkeston.
At the Charlestown navy-yard (1800) there are docks, manufactories, foundries, machine-shops, ordnance stores, rope-walks, furnaces, castingpits, timber sheds, ordnance-parks, ship-houses, &c. The famous frigate " Independence " was launched here in 1814, the more famous " Constitution " having been launched while the yard was still private in 1797.
Plantations have increased greatly in size (and also diminished in number), greater capital is involved, bagasse furnaces have been introduced, double grinding mills have increased by more than a half the yield of juice from a given weight of cane, and extractive operations instead of being carried on on all plantations have been (since 1880) concentrated in comparatively few " centrals " (168 in Feb.
Besides the sugar-refinery already mentioned, there were in Ig00 four tobacco factories, a national printing-press, an annular furnace for brick-burning, an iron-foundry and several blast-furnaces, under the management of the state.
In 1888 the Dowlais Iron Company (now Messrs Guest, Keen & Nettlefold, Ltd.) acquired here some ninety acres on which were built four blast furnaces and six Siemens' smelting furnaces.
Deep, and of the furnaces where they melted copper, tin and gold, are very numerous; their weapons of a hard bronze, their pots (one of which weighs 75 ib), and their melted and polished bronze and golden decorations testify to a high development of artistic feeling and industrial skill, strangely contrasting with the low level reached by their earthenware.
The appendix de Benedictionibus to the Rituale Romanum contains formulae, often of much simple beauty, for blessing all manner of persons and things, from the congregation as a whole and sick men and women, to railways, ships, blast-furnaces, lime-kilns, articles of food, medicine and medical bandages and all manner of domestic animals.
The shores of all the lakes which filled the depressions during the Lacustrine period abound in remains dating from the Neolithic Stone period; and numberless kurgans (tumuli), furnaces and so on bear witness to a much denser population than the present.
On account of its transparency and its resistance to fire and sudden changes of temperature, mica has been much used for the windows of stoves and lanterns, for the peep-holes of furnaces, and the chimneys of lamps and gas-burners.
Bangor has various manufactures, the most important of which (other than those dependent upon lumber) are boots and shoes (including moccasins); among others are trunks, valises, saws, stoves, ranges and furnaces, edge tools and cant dogs, saw-mill machinery, brick, clothing, cigars, flour and dairy products.
A similar process is used in Carinthia; only the furnaces are smaller and of a somewhat different form.
In large works the silver-lead alloy is removed when it contains 60-80 silver, and the cupellation of the rich bullion from several concentration furnaces is finished in a second furnace.
The efficiency of such ventilating furnaces is low, and they cannot safely be used in mines producing fire-damp. They are sometimes the cause of underground fires, and they are always a source of danger when by any chance the ventilating current becomes reversed, in which case the products of combustion, containing large quantities of carbon dioxide, will be drawn into the mine to the serious danger of the men.
On account of their dangerous character furnaces are prohibited by law in many countries.
Electrical furnaces have not as yet been employed for ordinary glass-making on a commercial scale, but the electrical plants which have been erected for melting and moulding quartz suggest the possibility of electric heating being employed for the manufacture of glass.
In the next stage of the process, the glass is raised to a high temperature in order to render it sufficiently fluid to allow of the complete elimination of these bubbles; the actual temperature required varies with the chemical composition of the glass, a bright red heat sufficing for the most fusible glasses, while with others the utmost capacity of the best furnaces is required to attain the necessary temperature.
The Venetian furnaces in the island of Murano are small low structures heated with wood.
In Germany, Austria and the United States, gas furnaces are generally used.
In England directly-heated coal furnaces are still in common use, which in many cases are stoked by mechanical feeders.
The furnaces are driven to a white heat in order to fuse the mixture and expel bubbles of gas and air.
The temperature required in the fusion of sheet-glass and of other glasses produced in tank furnaces is much lower than that attained in steel furnaces, and it is consequently pos Since the discovery of the Rntgen rays, experiments have been made to ascertain the effects of the different constituents of glass on the transparency of glass to X-rays.
In Europe the gas burnt in these furnaces is derived from special gas-producers, while in some parts of America natural gas is utilized.
Thus the dimensions of the largest glass tanks greatly exceed those of the largest steel furnaces; glass furnaces containing up to 250 tons of molten sible to work glass-tanks continuously for many months together; on the other hand, glass is not readily freed from foreign bodies that may become admixed with it, so that the absence of detachable particles is much more essential in glass than in steel melting.
This workman stands upon a platform in front of special furnaces which, from their shape and purpose,.
The process of sheet-glass manufacture described above is typical of that in use in a large number of works, but many modifications are to be found, particularly in the furnaces in which the glass is melted.
In some works, the older method of melting the glass in large pots or crucibles is still adhered to, although the old-fashioned coal-fired furnaces have nearly everywhere given place to the use of producer gas and regenerators.
For the production of coloured sheet-glass, however, the employment of pot furnaces is still almost universal, probably because the quantities of glass required of any one tint are insufficient to employ even a small tank furnace continuously; the exact control of the colour is also more readily attained with the smaller bulk of glass which has to be dealt with in pots.
Except for making bottles of special colours, gas-heated tank furnaces are in general use.
- Glass for this purpose, with perhaps the exception of the best white and tinted varieties, is now universally produced in tank-furnaces, similar in a general way to those used for sheet-glass, except that the furnaces used for " rolled plate " glass of the roughest kinds do not need such minutely careful attention and do not work at so high a temperature.
These small furnaces are usually heated by an oil spray under the pressure of steam or compressed air.
In the 16th century it had become a trade of great importance, and about 1764 twenty-two furnaces were employed in the production of beads.
It appears that as early as 1295 furnaces had been established at Treviso, Vicenza, Padua, Mantua, Ferrara, Ravenna and Bologna.
In 1324 a municipal edict was issued forbidding the erection of glass-furnaces within the city.
They can be traced by cullet heaps and broken-down furnaces, and by their names, often mutilated, recorded in parish registers.
Slingsby for burning coal in furnaces, and coal appears to have been used in the Broad Street works.
The ore is smelted at Lubumbashi, where in 1918 were seven furnaces with a producing capacity of 40,000 tons a year.
In the neighbourhood of Millom there are blast furnaces and highly productive mines of red haematite ore.
The bagasse so used is now commonly taken straight from the cane mill to furnaces specially designed for burning it, in its moist state and without previous drying, and delivering the hot gases from it to suitable boilers, such as those of the multitubular type or of the water-tube type.
The chief industrial establishments are smelting furnaces for cobalt, meat-preserving works at Ouaco, sugar-works and distilleries at Noumea and La Foa, tobacco, oil and soap factories at Noumea.
Pliny explicitly speaks of a mineral Katiµ€ia or cadmic as serving for the conversion of copper into aurichalcum, and says further that the deposit (of zinc oxide) formed in the brass furnaces could be used instead of the mineral.
The furnaces are square and open in front, to allow the outlet ends of the retorts to project; they are grouped together by fours; and their several chimneys are within the same enclosure.
When hydraulic pressure to the amount of 2000 to 3000 lb per square inch is applied, the saving is unquestioned, since less time is required to dry the pressed retort, its life in the furnaces is longer, its absorption of zinc is less, and the loss of zinc by passage through its walls in the form of vapour is reduced.
The primary advantages of gasfiring are that less fuel is required, that there is better control of the heat in the furnace, and that larger and more accessible furnaces can be built.
In Silesia the introduction of gas-firing has led to the use of furnaces containing eighty muffles.
In the United States, Belgian furnaces of type (a) are built to contain 864 retorts; of type (b), to contain 300 to 400 retorts; and of type (c), preferably about 600 retorts.
The use of gas-fired furnaces greatly simplifies manual labour.
Again, in direct-fired furnaces there are commonly seven or eight rows of retorts, one above another, so that to serve the upper rows the workman must stand upon a table, where he is exposed to the full heat of the furnace and requires a helper to wait upon him.
Furthermore, with the large furnaces which gas-firing makes possible mechanical appliances may be substituted for manual labour in many operations, such as removing and replacing broken retorts, mixing and conveying the charge, drawing and casting the metal, charging and emptying the retorts, and removing the residues and products.
A redistilled zinc, from an ordinarily pure commercial zinc, is often called chemically pure, but redistillation is seldom practised except for the recovery of zinc from galvanizer's dross and from the skimmings and bottoms of the melting furnaces of zinc rolling mills.
As each retort in a furnace is in all essentials a separate crucible, and as the metal from only a few of them goes into a single ingot, there can be no uniformity either in the ingots made from the same furnace during a day's run or in those made from several furnaces treating the same ore.
Much of the earlier electrometallurgical work was done with furnaces of the (a) type, while nearly all the later developments have been with those of class (b).
- Independently of the question of the application of external heating, the furnaces used in electrometallurgy may be broadly classified into (i.) arc furnaces, in which the intense heat of the electric arc is utilized, and (ii.) resistance and incandescence furnaces, in which the heat is generated by an electric current overcoming the resistance of an inferior conductor.
Practically the first of these furnaces was that of Despretz, in which the mixture to be heated was placed in a carbon tube rendered incandescent by the passage of a current through its substance from end to end.
Many of the furnaces now in constant use depend mainly on this principle, a core of granular carbon fragments stamped together in the direct line between the electrodes, as in Acheson's carborundum furnace, being substituted for the carbon pencils.
Elba was famous for its mines in early times, and the smelting furnaces gave it its Greek name of A' OaNia ("soot island").
The latest cupelling furnaces have the general form of a reverberatory copper-smelting furnace.