Mechanical arrangement: for supplying the tunnel-head with the materials for fusion.—.The mode of supplying the lime, coke, iron-stone, &c. to the crater, or tunnel-head of the furnace, was formerly by men carrying them in baskets up an inclined plane or bridge. Subsequently small waggons or corves were em ployed to take the materials up an inclined railway to the crater, by means of chains connected to the waggons, and passing round a drum or rigger, actuated by the steam engine, or other prime mover. In some instances the weight of a bucket of water descending into a pit was employed as the moving force to draw the loaded corve up to the top of the furnace, or hopper leading into it; where the corve, by being provided with a sliding bottom, to which was fixed a projecting bar, discharged its contents, by the bar coming against an obstruction, which pushed the bottom away, when over the discharging hole. The bucket also, on reaching the bottom of the pit, was discharged of its water, through a valve in its bottom being opened by coming in contact with a projecting pin at the bottom of the pit. The motion was then reversed by the superior weight of the empty waggon, causing it to descend the inclined plane, and raise up the empty bucket for a renewal of the operation, by refilling the vessels, one with the mineral, and the other with the water. In some situations the mode of raising the materials is by an endless chain passing round two riggers, one at each extremity of the Inclined plane. the chain carrying two corves or buckets, one of which is being filled below whilst the other is Whig discharged above, in continuous succession ; in a similar way to the scoops in dredging and excavating machines, described under their initial letters.
Welsh Smelting Furnaces.—In South Wales and other mountainous districts they usually contrive to build their blast furnaces beside or steep pied pices, which are sometimes walled up artificially to render them perpendicular, so that the tunnel-heads of the furnaces shall be upon a level or somewhat lower plane than the contiguous high ground, from which a bridge is thrown on to the top of the solid masonry, after the manner expressed in the subjoined cut. This cut also gives the external form of the fur nace described at page 756, with this difference merely, that instead of the open crater or tunnel-head, this has a vertical cylindrical chimney of the same internal area as the upper orifice built over it ; on one side of which there is a doorway for charging the furnace with the mine and other materials. A parapet wall or iron fence surrounds the upper edge of the square tower.
The dotted lines in the figure indicate the form of the interior of the furnace. The coke-hearths and the mine-kilns, and all other supplies to the furnace, are situated on the high ground, so that they can at once be shot across the bridge into the tunnel-head. Various buildings, including the " cast-house," where the metal is run into pigs (or other forms to patterns as may be required) are situated on the lower level, and are covered with roofs.
Anthracite used in Smelting.—Before closing our account of the smelting department of the iron manufacture, we think it right to call the attention of those who are interested in the iron trade to the consideration of the practica bility of employing anthracite, or stone coal, in the process of smelting. In several parts of Great Britain and Ireland, but particularly in Scuth %Vales, there are many thousands of acres of iron-stone near the surface, with a vast abundance of anthracite coal, lying in contiguous strata. This coal, notwith
standing it consists almost entirely of carbon, has been alleged, and is generally believed, to be incapable of smelting iron ; and as there are in some districts (that of Llanelly, for instance,) no bituminous coal sufficiently near to these valuable beds of iron-stone, they remain unworked, wider the presumption that they cannot be worked with profit, owing to those circumstances. Whether this prejudice is well or ill-founded, is a question that we cannot take upon ourselves to solve ; but we will place before the reader a few facts that appear to bear directly upon the question, and leave the solution to those who are more practically conversant with the subject.
In several parts of the United States of America, where (as in South Wales) iron-stones and anthracite are plentiful, but bituminous coal wanting, recent attempts have been made to smelt the iron with anthracite alone ; and all the reports that have reached us on that subject agree in stating that success has attended those attempts.
Malin's Furnace for Smelting Iron with Anthracite Coal.—Mr. Joshua Malin, of Lebanon, in Pennsylvania, has described his furnace for this purpose in the Franklin Journal. It is very similar to our common blast furnaces, the cru cibles and health alone differing materially. Mr. Malin's crucible, instead of being square is round ; anthracite coal being so much more dense than coke or charcoal, its weight causes it to descend in the corners or angles of a square hearth, where, being screened from the intense blast which is required, and carrying with it a portion of the unmelted ore, it mixes with, and chills a quantity of the fused ore and metal, which stops the operation of the furnace.
For the smelting by means of anthracite, Mr. Malin states, that the blast must be introduced under a of at least two and a half pounds to the circular inch ; and the quantity required for a common sized furnace will not be less than 28,000 cubic feet per minute, or 7 cubic feet per minute for every circular inch in the area of the hearth at the tuyere. The hearth of the furnace in which Mr. Malin made his experiments, was only 11 inches in diameter at the tuyeres, the blast being introduced as represented in the subjoined plan. Mr. Malin had the diameter increased to 14 inches, and found that the blast which he had at his command would not enable him to go beyond that point, as, when he attempted it, the scoriae and metal chilled, and formed a tube from the tuyere a part of the way across the hearth. Fig. 1 exhibits a vertical sec tion, and Fig. 2 an horizontal section drawn to a scale of an eighth of an inch to the foot ; the letters of reference in each figure that are the same indicate corresponding parts. a is the crucible, being a part of what is commonly called the hearth of the furnace ; b are the bushes, or that part where the metal passes from the solid to the fluid state as it descends ; c is the bottom stone of the hearth, bedded in sand, and supporting the crucible and bushes; d is the dam-stone; e e the blast pipes ; ff inner walls of the furnace of fire-brick, around which is a space from 4 to 6 inches wide, filled with soft sandstone; h tymp-plate ; i i lintels of cast-iron to support the inner walls over the tuyere and tymp arches ; k k tuyere arches ; 1 part where the metal flows out; ea tymp arch ; a the tymp-stone, forming a part of the crucible, and supporting a part of the bushes.