furnace, the keeper is enabled to reach with a ringer above the tuyere. Where argillaceous or clay ores of gray iron are smelted, this is necessary. The opening left by raising the timp is easily kept tight by a good stopper; for this purpose, a flanch, which reaches under the stone, is cast to the timp-plate k. The timpstone is protected by the timp-plate, which must be two inches thick, imbedded in fire clay, and secured by two uprights l. These angular iron plates protect the stones or bricks on each side of the timp; they are more distinctly shown in Fig. 58. Besides holding the

timp-plate, they afford the advantage of keeping the forehearth clean; for the hot cinders will not adhere to the iron plates, but are very apt to stick tenaciously to stones or brick. At this stage of our work-during the whole of which great care must be taken to form good joints, and to employ good refractory mortar, that is, fire clay mixed with river sand, or, what is preferable, with sand from pounded furnace cinders-the boshes may be put in. In charcoal furnaces, if steep, these are generally made of fire brick, but if built at an angle of less than 50°, good sand, mixed with a little fire clay, is an excellent material. In the latter case, the mixture should be well stirred and worked, and every pains should be taken that the compound is well prepared before it is used. It should be well pounded in, and, to prevent cracking, should be gradually dried. If fire bricks are used, made in proper form, and of the largest possible size, there will be no difficulty in putting in good boshes. The damstone b is very seldom laid in its place, before the furnace is properly dried, and ready for the blast. Its protecting plate m, the dam-plate, can be laid at any time after the furnace is in operation.

Below each hoop the last layer of bricks projects at least half an inch; upon this layer the hoop rests. If the stack is built of stones, pieces of iron bars are walled in to support the hoops. Between these hoops are left air-holes, through which moisture has vent.

b. Starting of a Charcoal Furnace.-When a furnace is erected, and ready to be fired, a small fire may be put in the hearth. We should always be cautious to give the interior of the hearth a lining of common brick. This will prevent, in a great measure, the cracking and scaling of the hearthstones. The fire is fed from below. Any kind of fuel will serve for this purpose, because the fire is only designed to dry the masonry. If the stack is new, or if it is one which has been for a long time unused, it is necessary to cover the throat by iron plates, and to leave but a small hole; this hole may be so regulated that we may burn just as much fuel as we choose. Seven weeks, and if the season is cold, eight or ten weeks of constant firing, will be necessary to dry a new stack so that it can be charged with charcoal. But before the furnace is charged, the temporary lining of brick in the hearth must be removed. The lower part of the furnace, or the hearth, is to be filled gradually; and the fire must be permitted to rise in a blue flame on the top of the coal, before the furnace is filled higher than the boshes. From this point half coal and half brands are to be used; the latter addition causes a more liberal draft of air in the furnace. If the furnace is quite warm before putting the charcoal in, and if we are confident that no moisture exists in the masonry, ore may be charged after the furnace is half filled with charcoal; but if we doubt that moisture is wholly expelled, the whole stack should be filled with coal, and the fire kept up until we are satisfied that the walls are perfectly dry. Where everything is ready for the start, repeated grates may be formed to facilitate the burning of coal, as well as to heat the furnace. Grates are formed by laying across the timp a short iron bar, as high up as the damstone; by resting upon this bar six or seven other bars, or ringers; and by pushing their points against the backstone of the hearth. A grate thus formed increases draft and heat to a considerable degree, and very soon brings the top charges down into the hearth. Where ore is charged to the top, the descent can be accelerated by leaving the grate most of the time in the hearth; but care should be taken that too much coal does not remain at the bottom, for this will injure the bars. In this way the ore charges may be brought down within twenty-four or thirty hours. But if we are not to put the blast in,

square stacks. The cause of these evils may have been too thin and too rough walls, which may easily be avoided. But these furnaces have another disadvantage, that is, they nearly always break the strongest binders. In addition to this, they require too many binders; so that, on an average, a round stack is not cheaper than the square stack. There may be instances, some of which we shall produce hereafter, in which a round stack is preferable. These instances are rare. Still, for the sake of those who may be disposed to build a round stack, we will present a drawing of one in operation at the Great Western Works.

section, and Fig. 60 a front The drawing is so dis

Fig. 59 represents a vertical cross view, of a cupola furnace built of brick. tinct as to need no particular description. The whole stack can be built altogether of brick; or partly of brick and partly of stones, as is the case at the Western Works; or altogether of stone. Stone, however, would be very expensive, on account of the dressing necessarily required. Through the lower or square part, four binders are laid; the hoops, of wrought iron of good fibrous quality, of the upper or round part, must not be more than six inches apart, and should be two inches wide, and three-fourths of an inch thick.

Below each hoop the last layer of bricks projects at least half an inch; upon this layer the hoop rests. If the stack is built of stones, pieces of iron bars are walled in to support the hoops. Between these hoops are left air-holes, through which moisture has vent.

b. Starting of a Charcoal Furnace.—When a furnace is erected, and ready to be fired, a small fire may be put in the hearth. We should always be cautious to give the interior of the hearth a lining of common brick. This will prevent, in a great measure, the cracking and scaling of the hearthstones. The fire is fed from below. Any kind of fuel will serve for this purpose, because the fire is only designed to dry the masonry. If the stack is new, or if it is one which has been for a long time unused, it is necessary to cover the throat by iron plates, and to leave but a small hole; this hole may be so regulated that we may burn just as much fuel as we choose. Seven weeks, and if the season is cold, eight or ten weeks of constant firing, will be necessary to dry a new stack so that it can be charged with charcoal. But before the furnace is charged, the temporary lining of brick in the hearth must be removed. The lower part of the furnace, or the hearth, is to be filled gradually; and the fire must be permitted to rise in a blue flame on the top of the coal, before the furnace is filled higher than the boshes. From this point half coal and half brands are to be used; the latter addition causes a more liberal draft of air in the furnace. If the furnace is quite warm before putting the charcoal in, and if we are confident that no moisture exists in the masonry, ore may be charged after the furnace is half filled with charcoal; but if we doubt that moisture is wholly expelled, the whole stack should be filled with coal, and the fire kept up until we are satisfied that the walls are perfectly dry. Where everything is ready for the start, repeated grates may be formed to facilitate the burning of coal, as well as to heat the furnace. Grates are formed by laying across the timp a short iron bar, as high up as the damstone; by resting upon this bar six or seven other bars, or ringers; and by pushing their points against the backstone of the hearth. A grate thus formed increases draft and heat to a considerable degree, and very soon brings the top charges down into the hearth. Where ore is charged to the top, the descent can be accelerated by leaving the grate most of the time in the hearth; but care should be taken that too much coal does not remain at the bottom, for this will injure the bars. In this way the ore charges may be brought down within twenty-four or thirty hours. But if we are not to put the blast in,

and to commence smelting, the descent of the ore charges may be delayed three, even four days, without any injury to the following operations: When everything is in order, the sinking of the ore may be hastened. This will be indicated by melting drops, often drops of iron, before the tuyeres. When these are seen, the damstone is to be laid, imbedded in clay; also its protector, the cinderplate. The hearth is once more cleaned; the hot coal then drawn towards the dam, and covered with moist coal dust; after which a gentle blast may be let into the furnace. During the first twentyfour hours, but little iron is made; most of the ore is transformed into slag; and the iron which comes down gets cold on the bottom stone, where it is retained. At this early stage, it would not be prudent to urge the blast machine too fast, for great caution is required to prevent those troubles which result from a cold furnace. These troubles are, generally, cold iron in the bottom, and, in consequence of that, cold tuyeres. Gentle blast, small burden, and great attention alone will prevent these evils. Where a furnace has been for a week in blast, having in that time produced from nine to ten tons of metal, and where the hearth is clean, that is, where it is perfectly free from cold iron, or clinkers, the burden may be increased, and the blast urged more strongly. A well-regulated furnace, will, during the second week, make from sixteen to eighteen tons; and the same amount during the third and fourth weeks. furnace, just started, should not receive so heavy a burden of ore as a furnace which has for some time been in operation. About half the regular burden should, as a general rule, be taken; that is, if a full charge of ore is assumed to be 700 pounds, the starting charge should be 350 pounds. This amount should not be increased for at least three or four days, or one week. During this time, while the light charges last, an abundance of brands along with the coal may be used for the purpose of keeping a clean, open furnace.

A

c. Charges of a Charcoal Furnace.-The coal charges of a charcoal furnace should have, invariably, the same bulk or weight. Why this rule is generally observed, we shall explain at another place. The amount of coal for one charge depends somewhat on the dimensions of the throat of the furnace; but fifteen bushels are considered to be an average charge.

The ore charges vary according to the quality of the ore and coal, and according to blast and management. The method by which the quantity of ore is determined we shall investigate at the close