the different sizes of Sturtevant's fan and Root's pressure-blower; the latter, yielding a much higher pressure, is better for lead-smelting, and may possibly compete with cylinder blast-engines, where coke is used in smelting. The only advantages the former have over the latter are their cheapness and the small amount of power they require. A Root's blower No. 8, yielding sufficient blast for three large-sized furnaces, does not require more than twenty horse-power.

Building materials.-Rubble-stones are used for building the founda tions and sometimes the outer casings of furnaces. The latter are gen erally made of common brick or dressed stone to present a handsomer appearance. Those parts of a furnace, however, which are most exposed to an intense heat and the corrosive action of ore and slag, must be constructed of refractory or fire-proof materials. Of such we have

Certain sandstones, free from alkaline matter and metallic oxides. A small percentage of iron oxide is less detrimental than alkaline earths or feldspar. An excellent sandstone is found on Pancake Mountain, a series of low hills between the Diamond and White Pine Ranges, distant about twenty-five miles from Eureka, Nevada. Sandstones of the same age-the carboniferous-are also found in the Diamond and White Pine Mountains, but their physical properties, and hence their behavior in the furnace, are different and not satisfactory. The Pancake sandstone has a very fine grit and a light yellow color, and does not crack or fly in the fire after seasoning. Green sandstones of ever so good a quality, and defective ones, viz, such as show flaws or nodules of foreign matter, are not fit to be placed in the furnace. The Pancake sandstone is known to stand for months in a furnace without needing to be replaced. It sells for $20 per ton at the quarry, and $12 additional for hauling.

The coarse-grained reddish sandstones and quartzites of Utah are not to be compared with those before mentioned, and had better be used for outer casings only.

Granite does not often answer the requirements of a fire-proof material, and is mostly used as bottom-stone only. In Argenta, Montana, however, a very quartzose granite is used in the furnaces, and it stands campaigns of three weeks' duration.

Instead of the natural fire-proof stones the majority of smelters use artificial ones, viz, English, Pennsylvania, and Colorado fire-bricks. Sun-dried bricks or adobes, molded of various proportions of good clay and coarse quartz-sand, are too expensive, and therefore have gone out of use. They were used in the White Pine Smelting-Works.

The clay used about a furnace ought to be refractory, or nearly so, and plastic at the same time. These qualities are combined in the Eureka and the Camp Floyd (Utah) clay; that of Camp Douglas (Utah) is too lean, and that of White Pine (Nevada) almost worthless on account of its large percentage of oxide of iron.

Lean clay serves well enough as a mortar, but is unfit for a great many other purposes, as will be seen below.

Good fire-clay contains from 50 to 70 per cent. of silicic acid, and from 30 to 50 per cent. of alumina.

As a mortar for the foundation-walls and the outer casings, a mixture of slacked lime and river-sand is used; for the inside, or lining, however, as for all parts of a furnace directly in contact with heat, a mixture of refractory clay with quartz-sand or ground sandstone has to be used. The clay, of course, must be ground and sifted. Lime-mortar in this instance is unfit for use, as it crumbles off in the heat, and allows the slag in combining with it to creep through the joints.

The annexed sketches show the construction of an improved blastfurnace for smelting lead-ores, such as are now in use in the West, and have given great satisfaction.

The longitudinal section (Fig. 1) is made along the line H Y, in Fig. 2; and the cross-section (Fig. 2) is along the line T V in Fig. 1. A is the shaft of the furnace; B, the chimney; C, the hearth; D, the founda

tion; E, the bottom-stone; a, the dam-plate; a and b, hearth-plates of cast iron; c, cast-iron pillars, on which the flange d rests; e, dam; f, fore-hearth lying outside of the furnace; g, bridge; h, tymp-stone, or front made of clay; i, breast; k, slag-spout; 1, matte-spout, or iron-spout; m, siphon-tap; n, tap-hole; o, lead-well; P, p', p2, &c., tuyeres through which the blast enters the furnace; q, nozzles, (made of galvanized iron;) r, wind-bags, (of leather or canvas;) 8, induction-pipe; t, charging-door or feed hole; u, throat.

The wall in which the breast lies is called the front wall, the one opposite to this the back wall; the adjoining ones the side walls.

This furnace is called an open-breasted one. In foreign countries furnaces with a closed breast and without fore-hearth, which have only an opening for the exit of the slag, are often used. Such furnaces are termed "crucible furnaces." Notwithstanding the many advantages they have over the open-breasted ones, they do not permit the detaching of accretions in the furnace, and are, therefore, not suited for our pur poses. The mason-work, especially the lower part, of all rectangular furnaces is strongly bound together by 12-inch tie-rods of wrought iron laid in the outer walls. Each pair of them, lying in the same vertical plane, passes through a wooden, or, better, a cast-iron brace, which is screwed tight to the wall. Round furnaces are tied either by means of iron rings passing around the outside, or by complete shells of boiler or sheet iron.

The height of shaft-furnaces ranges from 8 to 20 feet above the center of the tuyeres. Low furnaces are necessary for basic ores, especially such as carry a great deal of oxide of iron, (White Pine district,) to prevent the reduction of metallic iron. High furnaces are of good service for refractory ores, e. g., argillaceous or quartzose ores, (Bingham Cañon,) and where a bi-silicate slag is desired. In high furnaces a higher temperature is attained with a less amount of fuel than in the low ones. But a low furnace is easier manipulated when deranged than a high one. Where the character of the ores changes frequently a low furnace is preferable. The standard height in this country is 10 feet above the center of the tuyeres. On the top of the furnace is an iron, or, better, brick smoke-stack, high and wide enough to carry off the fumes.

The manner of charging or feeding is of importance, as it affects the working of a furnace materially. Furnaces of small dimensions generally have a feed-hole a few inches above the throat, on that side of the furnace directly opposite the front wall. The proper proportion of fuel, either by measurement or weight, is introduced first, and on the top of that the ore, which may be scattered all over the area of the furnace, leaving an empty space only. at the front wall, (Jackson & Roslin furnaces, Eureka; Salt Lake Valley, Stockton, &c.) More capacious furnaces require two feed-holes, which are situated at nearly right angles to the breast, i. e., in the side walls, (Eureka Consolidated Company's and Utah Silver Mining and Smelting Company's new furnaces.) The ore is not spread over the area of the throat, but charged round the tuyere-walls, leaving a core of coal in the center.

To insure regularity in charging, the throat of a furnace is frequently provided with a funnel, the opening of which can be kept closed by a sheet-iron box let down from the top while charging. As soon as it is time to charge the furnace, this box is raised by means of a counterpoised lever, and the charge drops down. After emptying the funnel, the box is lowered again. This arrangement at the same time protects the workman from noxious vapors. Where no condensation-chambers are used, this box runs out into a pipe, which is movable in the station

ary smoke-stack, (Richmond furnace, Buel & Bateman's furnaces.) I shall have occasion hereafter to speak more fully about charging.

The number of tuyeres and the manner of placing them are really not of so great consequence as is generally assumed, if the proper quantity of air is introduced into the furnace and divided well in the hearth. The majority of smelters in this country place the tuyeres only 6 inches above the level of the slag-spout, and point them downward. This is very faulty in lead-smelting, as it tends to concentrate the heat too far below, volatilizing much metal. Placing the tuyeres too high above the slag hole is entirely wrong, as in that case the metal in the hearth below cannot be kept sufficiently hot. Before the tuyeres the furnacetemperature is highest. There the separation of the metal from matte and slag, according to their specific gravity, takes place. Below the tuyeres the temperature decreases again. If the tuyeres are, therefore, inserted too high above the slag-spout, the molten masses will stiffen, and even solidify, below. A furnace in White Pine once had the tuyeres three feet or more above the slag-hole. The consequence was a congealing of the fused masses in the hearth, and an entire clogging up of the furnace. The correct way is to place them horizontally, all on the same level, and from 10 to 18 inches above the slag-spout, (Eureka Consolidated Company's and Phenix Company's works.) All vertical dimensions are understood to be measured from the center of the tuyeres. For every 1 square feet of hearth-area, a tuyere of 2-inch nozzle is required.

Since the introduction of cast-iron or wrought-iron tuyeres cooled by water, the working capacity of lead-smelting furnaces has been greatly increased. Formerly, only sheet-iron, clay, or simple cast-iron ones were in use, giving rise to much inconvenience. In order to protect the furnace-walls from the influence of the reverberated heat, the tuyere had

to be provided with a nozzle of clay, or a very acid slag, protruding into the furnace. But, to keep this nozzle or nose of a certain length, and to prevent it from growing or melting off, it had to be constantly watched by attentive and experienced men. During the last century an attempt was made on the Hartz Mountains to increase the production by con structing a large-sized furnace with fourteen tuyeres. It failed on ac count of the difficulty in keeping the tuyere-walls from burning out. Even the first Raschette furnace, built in 1864, on the Hartz, was provided with sheet-iron tuyeres. But they had to be replaced so oftenwhich always necessitates a stoppage-that it was found expedient to try water-tuyeres, which, indeed, gave entire satisfaction. The best ones in use in this country are wrought-iron ones of the Keyes patent. The lowest point of the hearth is from 36 to 40 inches below the cen ter of the tuyeres, the latter figure being the maximum. If made deeper, the lead will get too cold.

In selecting a furnace-site a great many things have to be taken into consideration in an economical as well as a technical point of view. To answer the latter three conditions are necessary-a sufficiency of water, a spacious ore-floor, and a convenient slag-dump. The lack of one or all of these conditions puts a smelter to great inconvenience, and may even cause a financial failure. After having graded off a suitable location for a furnace at the side of a gently sloping hill, if such a one is convenient, a square or rectangular excavation is made in the ground to receive the foundation. The area is generally 8 by 10 or 10 by 10 feet, the depth depending upon the condition of the subjacent ground. If the same be directly on the bed rock, as in the instance of the Eureka Company's furnaces, no foundation is required, and a depth of 3 or 4 feet is sufficient to receive the furnace-masonry proper; but if it be moist or in gravel, a depth of from 7 to 14 feet is judicious. The foundation is made of undressed rocks which are laid in lime-mortar, or, better, in cement. The largest ones are used for corners, and the joints must be filled up with spalls. The topmost course, on which the furnace is to be built, ought to consist of dressed stones, well seasoned, and sandstones, if possible. The joints must be perfectly tight. In some instances it is desirable to make provision for draining off the surface-water by arched channels, as the furnace-bottom ought to be absolutely dry.

If the furnace is intended to be provided with hearth-plates, like the one described, those, as well as the cast-iron pillars, are to be put in place now. Then the inside of the hearth-plates is carried up of sandstone blocks 2 feet wide by 1 foot thick, leaving sufficient room for the tap-holes and an open space at the dam-plate. In Eureka, as soon as the mason-work has progressed to 7 inches above the plates, the tuyeres are placed in position and walled in with fire-brick or sandstone. Three feet above the dam-plate the arch over the breast is started and the masonry continued to a level with the top of the pillars. Then the flange which is to bear the upper part of the furnace is put in its place and well bolted to the pillars. The flange is 2 inches thick. The part of the furnace above this flange may consist of inferior sandstone or even common brick, 1 foot or 18 inches thick, as it is less affected by the heat and corrosive action of the ore. About 6 inches or 1 foot above the charging-floor the chimney for earrying off the fumes is started and continued to a height of from 12 to 15 feet, leaving out spaces for the feedholes 3 feet wide by 23 feet high at two opposite walls. The chimney ought to have a sufficient opening-say 3 feet-at the top to prevent the smoke from issuing through the feed-holes into the charging-room. The use of sheet-iron smoke-stacks is objectionable, as they always get