blast is admitted through three tuyeres, one at the back and one at each side. The mouth or nozzle of the tuyeres is generally three inches in diameter, admitting a very large amount of wind-too much, considering the horizontal dimensions of the furnaces, which are about two feet square, and the easy fusibility of the ore. The shaft is from twelve to sixteen feet high, from the tuyeres to the charging hole. The hearth is about two feet below the tuyeres, and is made of stone, the front part alone being formed of a composition. At the bottom of the hearth is the tap-hole, through which the lead is run out at intervals. One tapping gives about 200 pounds of pig lead, which being run into molds, forms bars weighing from 80 to 120 pounds apiece, The furnace is built of stone found here, lined inside with a fire-proof sandstone, which is found at Pancake Mountain, about twenty miles distant. This last is porous, and of an excellent quality. Lately sandstone equally as good has been found at Eureka. The blast is furnished by fan-blowers. The illustration shows the common style of furnace used. Here A denotes the walls, built of a sort of porphyry tufa; B, the inside lining of sandstone; C, the front of the hearth, of composition. The shaft D has a square horizontal section, and the shaft O a circular one. I is the charging hole.

The ore is principally cerussite or carbonate of lead. There is also some galena, but only in limited quantities at present, and mostly changed into a dull, black mineral, retaining the structure of galena, and apparently unchanged in the center. Singularly enough, the dull portion is richer in silver than the galena, from which it seems evidently to have been formed, perhaps by the influence of internal heat. It resembles stetefeldtite. On an average, the ore prepared for smelting contains 40 to 48 per cent. of lead, $50 to $80 in silver, and $15 to $20 in gold per ton. In bulk, the ore has a yellow color, due to the iron in it. There is also arsenic in the ore, which, in smelting, combines with the iron, forming a white compound (speiss) somewhat like matte, and holding $36 to $45 per ton in silver and gold, and 24 per cent. of lead. The ore smelts readily by itself, nothing being added except about 20 per cent. of slag.

Analysis of the slag shows the following composition. For the sake of comparison, the composition of a Freiberg slag is also given. No. 1 is the slag from Eureka, and No. 2 that from Frieberg:

No. 1. No. 2.

There is a little too much iron in the slag No. 1. For the protection of the furnace lining a somewhat larger proportion of quartz in the ore would seem to be advantage

ous.

Yet as it is, there is a most fortunate coincidence of all the requirements for easily smelting the Eureka ore. About 24 pounds of charcoal are charged into the furnace at one time, and from 40 to 45 pounds of ore, besides 12 pounds of slag. The charging is done in a very irregular manner, by shovels, and without weighing or measuring. One furnace can smelt from eight to nine tons of ore in twenty-four hours. Three and a half tons of ore yield about one ton of pig lead, or "bullion," as they prefer to call it. The consumption of charcoal varies from 30 to 35 bushels to the ton of ore. At present, it costs about $20 to smelt a ton of ore; it is probable, however, that by using a furnace of larger capacity, the expenses may be reduced to $14 or $15.

When the furnaces are properly managed, the loss of lead will probably not exceed 20 per cent. At present, however, it is larger, owing to several reasons, and very largely to the very frequent use of crowbars about the hearth, whereby a great deal of lead is mixed in with the slag. By using such large tuyeres, it would seem that too much wind was brought into the furnace, and without sufficient pressure. Hence the heat is not concentrated in the smelting region just above the tuyeres, but is diffused in the upper part of the furnace, and the carbonate of lead commences to melt at a distance of one or two feet below the charging hole, and the lead is thus exposed a long time to volatilizing influences. Hence, also, in the hearth the temperature is too low, the slag stiffens, sticks to the walls, makes the constant use of the crowbar necessary and takes up mechanically considerable lead. Again, the ambition of having a very long run induces some smelters to keep the furnace at work when it evidently needs repairs, and this is another source of loss of lead and silver.

The amount of speiss (the combination of arsenic and iron) is about 3 per cent. of that of the ore. At present this is not treated further.

The bullion contains on the average about $170 in silver and $80 in gold, or a total of $250 per ton. This statement must be taken, of course, as a very general one. The lead is at present shipped to Newark, New Jersey, for the purpose of extracting the

silver and gold. There is nothing to prevent its being cupelled at Eureka, but different circumstances induce the companies to send it away.

A large furnace, with five tuyeres, and capable of smelting 24 tons in twenty-four hours, is now being built by the Eureka Smelting Company, under the superintendence of Mr. Ch. Von Liebenau. This furnace will be six-sided, and in the middle of each side, except the front one, comes a tuyere directed towards the center of the furnace. The diameter of the furnace, or rather the distance of the centers of opposite sides, is three and a half feet at the level of the tuyeres, and four feet at the level of the feeding hole. From the tuyeres to the feeding hole is 16 feet. The furnace will cost between $2,500 and $3,000.

This description is generally quite correct, and it will only require a few additional remarks to make it complete. At the same time I will try to point out the very serious defects which the present system of smelting is suffering under. Not all the furnaces are rectangular inside. I know of at least one which is round. From the sketch it can be seen that the furnace here figured has a sort of bosh on three sides, commencing about 14 feet above the tuyeres. Above, and just below the charging hole, the shaft is also contracted, and the chimney is a foot narrower than the shaft.

This form of the furnace tends greatly towards the formation of iron sows, and also toward volatilization of an enormous quantity of lead oxide, which carries always silver with it. Mr. Kuestel, in his article, does not give the result of experiments made by him and Mr. C. Von Liebenau, at Eureka. According to these, Lam informed from the most reliable source, i. e., one of the experimenters themselves, 30 per cent. of the silver and 40 per cent. of the lead contained in the ore are lost at present, and this is really enormous. Another very bad feature of the Eureka furnace is the large size of that part of the crucible lying outside of the breast. In fact, the whole of it, two feet wide and about one foot deep, is left entirely open. The consequence is, that a great amount of coal is necessary to cover up this space; that the heat, which spreads too much upwards anyhow, on account of the large quantity of insufliciently compressed blast, cannot be maintained in the crucible; that the slag, which is a low silicate, and is therefore inclined to stiffening, becomes cold and short, and mechanically incloses particles of lead which go over the dump. This takes place the more, as iron is also reduced from the charge on account of the long time it is kept in a reducing zone on the boshes, and bars are therefore frequently introduced to loosen it. To do this the fore-crucible is opened and more heat is lost. Considerable silver has heretofore also been lost in the speiss which, to within a short time ago, went over the dump as "white iron." It is now saved, but not treated further for the present. I am informed that part of the dumps, especially the oldest around the Eureka furnaces, assay as high as $80 per ton in silver.

As will be seen from Mr. Kuestel's article, the proportion of coal used per ton of ore is extravagant for ores as easily fusible as those at Eureka. This is partly caused by the construction of the furnaces; but a great deal of it is also due to the treatment of the coal, which is transported in sacks instead of racks, and exposed to all kinds of weather, so that it always contains a large amount of moisture, and is rather small and soft.

In my opinion, the improvements required in Eureka to make smelting extremely profitable are: 1. More careful burning of the coal, so as to obtain it hard, in larger pieces, lustrous and ringing; transportation in racks in the way done in Pennsylvania, New York, and the Eastern States generally. 2. Roasting of the ores in free heaps, with intermixture of small coal to volatilize part of the arsenic and sulphur. This

ought to be done at the mines, where wood is much cheaper than in Eureka. 3. The furnaces must be differently constructed, i. e., the walls must come down straight to the hearth, or contract gradually about one foot in the whole height from top to bottom, like the Raschette or the Piltz furnaces; the mouths of the tuyeres ought to be narrowed from three to one and a half inches, and pressure blowers ought to be employed instead of the fan-blowers now used. The fore-crucible ought to be closed, so as to protrude not more than four inches from the breast at the commencement of the campaign, and not wider than six inches. 4. As long as no dust chambers can be connected with the furnaces, (which would undoubtedly be the best,) the stack ought to be rather wider than the furnaces than narrower, so that the draught may be reduced to a minimum, and thus the escape of dust be prevented as much as possible. 5. Regular charges ought to be carefully mixed on the charge-floor, before the ore goes into the furnaces, which is not done now. The quartzose silver ores from New York and Secret Cañons, and no slag, should be mixed with the carbonates, so that a slag between a singulo and bi-silicate would be produced. Such a slag being hot, light, and not inclined to stiffening, mechanical losses of lead would be prevented, and the furnace-walls and crucible would last longer.

The Eureka Consolidated have been chiefly running on Champion and Buckeye ore, which is so easily mined that the whole cost of mining and hauling over two miles to the furnaces is only $4 25 per ton. In the fifty-six days immediately preceding the 30th of June, they smelted 765 tons 368 pounds of ore, which gave 238 tons of bullion, gross returns, for which, from New York, gave $348 per ton. The quantity of charcoal consumed was 25,832 bushels, worth 30 cents per bushel, delivered. From these figures it will be seen that it took about three and a quarter tons of ore to make one ton of bullion, and required, say, thirty bushels of charcoal to smelt one ton of ore. Ores from some twenty-five or thirty other mines have been smelted in the various furnaces, and the results show about the same figures. It may therefore be safely noted that in the Eureka district three and one quarter tons of ore make a ton of bullion, and thirty bushels of charcoal are required to smelt one ton of ore.

The above account was prepared for this report in August, 1870. Since then the Piltz furnace, in the course of erection at that time, has been completed by the Eureka Consolidated Company, and has proved a perfeet success. Much of the former loss, occasioned by the unsuitable construction of the older furnaces, is entirely avoided in this one, and the consequence is a cheaper smelting and a higher yield in lead and silver.

The following article from the pen of Mr. Guido Kuestel, which appeared lately in the Scientific Press, gives a sufficiently clear idea in regard to the construction and working of the Piltz furnace, to answer all purposes for the present:

The want of furnaces so constructed as to permit the smelting of larger quantities of ore than hitherto effected with the old styles, led first to the introduction of the "Raschette" system, an arrangement by which the tuyeres, the form of the smelting space being rectangular, are placed in two rows, one of seven or eight on each long side, and are so arranged that the blast of one side strikes between that of the tuyeres of the other side. The figure, which gives a section of the furnace, explains this. The discharge of metal and slag takes place on the two narrow sides. The smelting result of these furnaces is greatly superior to that of the old-fashioned ones with one or two tuyeres, not only with reference to the larger quantity of ore smelted, in a given time, but also in saving a greater percentage of metal and fuel. The treatment of such a furnace, however, is delicate, and it required many months running before, by gradual improvement, a long smelting campaign was secured.

It is surprising that the rectangular shape was preferred to a circular one, for in

stance, one like the old iron-assay furnace of Sefstroem, with blast holes at equal distances on the periphery, the very effective result of which was well known. Mr. Aubel

gave an elaborate description of Raschett's furnace, alluding in the same to the circular shape. By theoretical reasoning he tried to prove that a circular form does not admit of a uniform smelting region, and that the consumption of fuel in the center would be a useless one. Notwithstanding this theory, Mr. Piltz, of Freiberg, Saxony, constructed a circular furnace, 5 feet in diameter in the clear, and with eight tuyeres, which has proved very successful, and which it is now proposed to describe.

For the sake of greater convenience in building, an eight-sided shape was chosen.

The first furnace of this kind was built, if I am not mistaken, about four years ago, at Halsbrucke, near Freiberg. From the start, the result was so favorable and so superior to Raschett's that, with slight modifications in regard to dimensions and number of tuyeres, at this time no other furnaces are in use at Freiberg. Aubel's theory did not prove to be correct. In a properly regulated smelting operation, no so-called "pigs" are formed either in the center or elsewhere; the slag runs con

The Raschette Furnace-section through the tuyeres. tinually, undisturbed by crowbar opera

tions, which usually are frequently neces

sary in other furnaces on account of clogging up, etc.

The figures show a horizontal and vertical section of one of Piltz's furnaces. Ata is represented a cast-iron box, in which the brickwork, c, is placed, and the remaining space beaten out with a composition, varying with the nature of the ore, generally being composed of one part of clay or loam and one part (volume) of charcoal, coke or anthracite, all powdered, mixed and moistened slightly. This composition is beaten in as hard as possible by means of wooden or iron pestles, and either the space is entirely filled and the crucible or receiver, b, then cut out, or the crucible is shaped during the stamping. The first method is preferable. There are two, sometimes three, tap-holes, leading the metal into the kettle, c. Above the crucible are seven tuyeres, g. The distance from g to the bottom of the hearth is 3 feet, and from g to the feeding-hole, 1, 10 feet. In case eight tuyeres are used, the last one is placed in front at i, a fow inches higher than the rest, having at the same time a small inclination, so as to direct the blast to the same point in the eenter toward which are directed the other seven, which lie in a horizontal position. The breast, i, rests on a hollow cast-iron pipe, cooled by a constant current of water, as are the tuyeres. The upper part of the wall, k, is suspended in a cast-iron mantle. The advantage of this arrangement lies in the convenience and facility with which the fire-bricks above the tuyeres, which are mostly exposed to the action of heat and of dissolving substances, can be removed

The Piltz Furnace-horizontal section.

and replaced without interfering with the upper part. Being suspended, there is also free access to the furnace from all sides. In place of the "hanging suspension," other furnaces of the kind are provided with three or more iron pillars on which the upper masonry rests. The height above the tuyeres differs often greatly up to 20 feet. The section of the furnace widens always toward the feeding-hole, as this has a beneficial

effect on the result of smelting. The force of the blast, finding a larger space in the upper region, is diminished as well as the heat, and the ore dust carried out does not amount to more than 1 per cent. The feeding aperture is at l. The gases, etc., enter dust-chambers before escaping through the chimney.

One of these furnaces is attended by one smelter, two slag-wheelers and three men to feed. Ore and fuel are regularly charged. The metal is tapped, from 18 to 20 times in 24 hours, into one of the two or three tap-kettles alternately. The slag runs continually into a slag-pot of cast iron of a pyramidal shape, the base being up. This cone is 29 inches high and 22 inches in diameter on the top. Matte, or globules of metal sink through the yet liquid slag to the bottom, in case any should be carried out. When stiff, the pot is turned over, the end of the slag-cone (where the metal or matte collects) broken off and melted over with the ore.

The blast or quantity of wind required is not very great-for each nozzle, about 125 cubic feet per minute, or for seven tuyeres 875 cubic feet, at a pressure of 1 inch quicksilver.

In the year 1868, a Piltz furnace, 20 feet high, smelted in 28 days:

Lead ores..
Piritous ores

Tons. 545,00 50.30