1004 IRON 



single ; as, combined with the process of running the iron in liquid from the blast- 

 furnace, the consumption of fuel is under the one-half of the quantity demanded 

 with single furnaces. 



Puddling furnaces are sometimes constructed with what are called ' water boshes.' 

 The hearth is surrounded with heavy cast-iron plates, in which is formed a passage of 

 1 inch or 1 inch bore, through which a current of cold water is caused to flow, the 

 object being to protect the furnace from the destructive action of the heat and cinder. 

 Overman found such furnaces to work well with fusible metal such as is produced 

 from a heavy burden on the blast-furnace, or from ores containing phosphorus ; but 

 with iron requiring a strong heat, such as results from a light burden on the blast- 

 furnace, or when it contains impurities firmly and intimately combined, puddling 

 furnaces with cooled boshes failed to make good malleable iron. 



We do not know whether the iron manufacturers in England will assent to the 

 following proposition, laid clown by the American metallurgist, viz : ' That the 

 smaller the amount of coal consumed, or the lower the temperature of the hearth 

 in the blast-furnace, the better will bo the quality of the metal ; that is, the more 

 fit it will become for improvement in the puddling furnace. The advantage of 

 heavy burden in the blast-furnace is not only that it reduces the first cost of the 

 metal, but makes a far superior article for subsequent operations. The worst cold- 

 short, or sulphurous metal, smelted by a low hoat, is quite as good as the best metal 

 from the best ore smelted by a high temperature.' Whatever may bo thought of 

 the latter part of this quotation, no iron manufacturer will deny that careful at- 

 tention to the blast-furnace is the best security of success in the puddling furnace, 

 and that success in the one is in proportion to the economy observed in relation to 

 the other. 



Siemens's Gas Puddling Furnace. Mr. C. W. Siemens in the application of his 

 regenerative gas-furnace to puddling has effected a considerable improvement. His 

 process must therefore be fully described. 



It is thought that it may be convenient to reproduce the figure in section of the gas- 

 furnace from p. 599, as it prevents the necessity of referring back to that article. 



The gas-producer is shown in fig. 1265 ; it is a rectangular fire-brick chamber, one 

 side of which, B, is inclined at an angle of from 40 to 60, and is provided with a 

 grate, c, at its foot. The fuel, which may be of any description, such as coal, coke, 

 lignite, peat, or even sawdust, is filled in through a hopper, A, at the top of the incline, 

 and falls in a thick bed upon the grate. Air is admitted at the grate, and in burning, 

 its oxygen unites with the carbon of the fuel, forming carbonic acid gas, which rises 

 slowly through the ignited mass, taking up an additional equivalent of carbon, and 

 thus forming carbonic oxide. The heat thus produced distils off carburetted hydrogen 

 and other gases and vapours from the fuel as it descends gradually towards the grate, 

 and the carbonic oxide already named diluted by the inert nitrogen of the air and by 

 any small quantity of unreduced carbonic acid, and mixed with these gases and 

 vapours distilled from the raw fuel is finally led off by the gas-flue to the furnace. 

 The ashes and clinkers that accumulate in the grate are removed at intervals of one 

 or two days. 



E is a pipe for the purpose of supplying a little water to the ashpit, to be decom- 

 posed as it evaporates and comes in contact with the incandescent fuel, thus forming 

 some hydrogen and carbonic oxide, which serve to enrich the gas ; o is a small plug- 

 hole, by which the state of the fire may be inspected, and the fuel moved by a bar if 

 necessary ; and n is a sliding damper by which the gas-producer may be shut off at 

 any time from the flue. 



It is necessary to maintain a slight outward pressure through the whole length of 

 the gas-flue leading to the furnaces, in order to prevent the burning of the gas in the 

 flue through the indraught of air at crevices in the brickwork. 



Where the furnaces stand much higher than the gas-producers, the required pressure 

 is at once obtained ; but more frequently the furnaces and gas-producers are placed 

 nearly on the same level, and some special arrangement is necessary to maintain the 

 pressure in the flue. The most simple contrivance for this purpose is the ' elevated 

 cooling tube.' The hot gas is carried up by a brick stack, H, to a height of 8 or 10 

 feet above the top of the gas-producer, and is led through a horizontal sheet-iron 

 cooling-tube, j, (fig. 1265), from which it passes down either directly to the furnace, or 

 into nn underground brick flue. 



The gas rising from the producer at a temperature of about 1000 Fahr., is cooled 

 as it passes along the overhead tube, and the descending column is consequently 

 denser and heavier than the ;is'-endin<r column of the .-am-- lc nLrili. and continually 

 overbalances it. The system forms, in fact, a siphon in which the two limbs are of 

 the usual length, but the one is filled with a heavier gaseous fluid than the other. 



In erecting a number of gas-producers and furnaces the inventor generally prefers 



