IRON 939 



experience of tho workman. The result is subject to considerable variation, that 

 is, whether economy of coal or that of ore is our object. Thus a modification is 

 required in the construction either of the whole apparatus or in parts of it. Tho 

 manipulation varies in many respects. One workman by inclining his tuyere to 

 the bottom, saves coal at the expense of obtaining a poor yield. -Another by carrying 

 his tue iron more horizontally at the commencement, obtains a larger amount of 

 iron, though at the sacrifice of coal. Good workmen pay great attention to the 

 tuyere, and alter its dip according to the state of the operation. The general manipu- 

 lation is as follows : The hearth is lined with a good coating of charcoal-dust ; and 

 the fire-plate, or the plate opposite the blast, is lined with coarse ore, in case any is 

 at our disposal. If no coarse ore is employed, the hearth is filled with coal, and the 

 small ore piled against a dam of coal-dust opposite the tuyere, a. The blast is at first 

 urged gently, and directed upon the ore, while the coal above the tuyere is kept cool. 

 Four hundred pounds of ore are the common charge, two-thirds of which are thus 

 smelted, and the remaining third, generally the finest ore, is held in reserve, to be 

 thrown on the charcoal when the fire becomes too brisk. The charcoal is piled to 

 the height of two, sometimes even three and four feet, according to the amount of ore 

 to be smelted. When the blast has been applied for an hour and a half, or two 

 hours, most of the iron is melted, and forms a pasty mass at the bottom of the hearth. 

 The blast may now be urged more strongly, and if any pasty or spongy mass yet 

 remains, it may be brought within the range of the blast and melted down. In a 

 short time the iron is revived, and the scoriae are permitted to flow through the 

 tapping hole c, so that but a small quantity of cinder remains at the bottom. By 

 means of iron bars, the lump of pasty iron is brought before the tuyere. If the iron 

 is too pasty to be lifted, the tuyere is made to dip into the hearth ; in this way the 

 iron is raised from the bottom, directly before, or to a point above the tuyere, until it 

 is welded into a coherent ball, twelve or fifteen inches in diameter. This ball is 

 brought to the hammer or squeezer, and shingled into a bloom, which is either cut in 

 pieces to be stretched by a hammer, or sent to the rolling mill to be formed into 

 marketable bar iron. A mixture of fibrous iron, cast iron, and steel, is the result of 

 the above process ; the quality of the iron depends entirely on the quality of the ore, 

 for there are no opportunities for the exercise of any skill to create improvements in 

 the process poor ores cannot be smelted at all. In Vermont, where the rich mag- 

 netic ores are employed, 4 tons of ore and 300 bushels of charcoal are required to 

 produce 1 ton of blooms. 



Although the old process of making iron directly from the ore has been completely 

 abandoned in Germany, it is still employed to a considerable extent in the United 

 States, where it was introduced early in the eighteenth century ; and has latterly been 

 employed in Canada for the treatment of the black magnetic and titaniferous sands 

 of the Labrador. The following description of the process has been given by Dr. 

 Sterry Hunt : The hearth or furnace (also known as the bloomary fire, Jersey or 

 Champlain forge) varies in length and breadth in different localities from 27 by 30 

 inches to 28 by 32 inches, and the depth from 20 to 25 inches above the tuyere, and 

 from 8 to 14 inches below; the sides are made of cast-iron plates, and the bottom 

 usually of beaten earth or cinders, but in the best-constructed hearths a hollow cast- 

 ing cooled by water is preferred. At East Middlebury in Vermont, the bottom plate 

 is 4 inches thick, with a hollow space of 2 inches within it. The side plates, which 

 are 1 inch thick, are slightly inclined inwards, and rest on ledges on the bottom 

 plate. A water-box, measuring 12 by 8 inches, is let into the tuyere plate; and the 

 water, after cooling the tuyere, passes through the bottom plate. The tuyere is placed 

 12 inches above the bottom at such an inclination that the blast may strike the 

 middle of the hearth. It is of segmental form, measuring 1 inch in height by f inch 

 wide. In front of the furnace, at a height of 16 inches above the bottom, is placed a 

 flat iron hearth 18 inches wide. The side plate berjeath it is provided with a tap-hole 

 for drawing off the cinders from time to time. The cast-iron plates used in the con- 

 struction of these furnaces last for two years. 



The blast employed has a pressure of from 1 to If Ib. to the square inch, and is 

 heated by passing through a stove of the ordinary siphon-pipe pattern, placed in an 

 upper chamber above the furnace, and heated by the waste flame. The temperature 

 at East Middlebury is said to be from 280 to 320. The use of hot blast is attended 

 with a considerable saving both of time and fuel, 240 bushels of charcoal being suffi- 

 cient to produce a ton of bloom with hot, while 300 are required with cold blast. The 

 weight of the charcoal may be estimated at from 16 to 18 Ibs. per bushel. 



The working of the furnace is conducted in the following manner: The fire having 

 been made up and the furnace heaped with charcoal, the ore in coarsely-pulverised 

 form is scattered at short intervals over the top of the burning fuel, and in its passage 

 downwards is reduced to the metallic state, the grains agglomerating to an irregular 

 mass or lump at the bottom, while the earthy matters form a liquid slag or cinder, 



