ings similar to those already described distinguish this mode of occurrence of the galena, with the exception of the arrangement being horizontal and between the strata, instead of vertical and crossing them. Moreover, other ores, as blende and iron pyrites, and mineral substances like veinstones, as calc spar, or tiff, as the miners call it, are more commonly associated with the galena, the different materials arranged in layers, the lead ore often the lowest, and in case of an opening incrusting the roof with bunches of crystals. Crevices have been found taking a saddle shape by the portions each side of the centre gradually dropping down to lower strata. One of these at Mills's lode, near Harle Green, presented a flat sheet at top measuring 20 feet across, with 2 to 3 feet thickness of solid galena. On each side the mineral sheet dropped down, gradually diminishing in thickness, but presenting so far as exposed an area of nearly 100 square feet of ore, from which about 1,200,000 lbs. of galena had been removed, and large quantities more remained in sight. In various parts of the lead region are groups of productive inines, as in the vicinity of Mineral Point, Shullsburg, and other places in Wisconsin, Galena in Illinois, and Dubuque in Iowa. The last district for its area has probably produced the largest amount of ore, and the crevices are here found in greater regularity and more extensive in length and depth than elsewhere. From many of the caves, which extend several hundred feet on the course of the crevices, several million pounds of galena have been obtained. The Langworthy crevice, which has been worked in different places along a line of nearly of a mile, has produced, it has been stated, about 10,000,000 lbs. of ore. It usually presented 3 tiers of crevices, of which the upper one was the most productive; their width was often 15 to 20 feet, and the width of workable ground sometimes 40 feet. Several other crevices are noted, which have produced from 2,000,000 to 4,000,000 lbs. of ore.—The statistics of the yield of the mines have been imperfectly preserved. The following table of lead shipped from the Galena river mines for the years named is compiled from reports made to government, and from records kept in Galena; the amount of receipts from the sales is estimated at $32,824,913: posed to have been produced by a lateral shrinkage or other force, which caused the rock to be rent apart in parallel lines. These lines are for the most part nearly due E. and W. On their extension mining may be prosecuted for long distances, but in depth its range is evidently very limited. The galena is found in great purity, sometimes free from all associations of other ores, but sometimes mixed with zinc blende, and more rarely with iron pyrites. It contains but a trace of silver. Three modes of its occurrence are recognized, viz., surface deposits, vertical crevices, and flat sheets. In the first the ore is in the clayey loam of the prairies, left behind in fragments when the rock that contained it decomposed. It is called by the miners "float mineral," and when found indicates the proximity of deposits in the rock, and encour ages "prospecting." This consists in sinking shafts into the rock, and driving across the presumed direction of the crevices. Miners are constantly engaged in this work, going from place to place till the discovery of a rich deposit rewards their search. In the natural sections along the cliffs that border the streams discoveries are most easily made; but under the deep soil of the prairies and the Hudson river shales that cover the elevated surface, rich crevices will remain concealed for centuries. In the vertical fissures the galena is found in a thin sheet attached to one or both walls, or separated from one or both by clay and ferruginous matter. It may be one or several inches thick, rarely a foot, and several may be so close to each other as to be mined together. The walls may maintain their parallelism for some distance, and gradually close up; or, as is often the case, they may suddenly separate and form what is called an opening. This enlarged crevice is usually only in part filled with the loose materials left behind by the decomposition of the rock, as fragments of the walls, the remains of the strings, bunches, and sheets of ore, and the loose matters that have been introduced. These openings, of irregular dimensions, are usually from 4 to 15 feet in height, 4 to 10 but sometimes 40 in width, and have been met with several hundred feet long. They are sometimes repeated to the number of 5, one below another, but one alone is more common. In some of the openings conical-shaped cavities, called chimneys, are found running up to a point in the cap rock, and occasionally lined with layers of galena, calc spar, and clay. These cavities were apparently worn and dissolved out by water. Some noticed by Mr. Whitney near Dubuque, rising up from the roof of a barren opening, which was traced the unusual length of some 500 feet with a height of 6 to 8 feet, extend 25 or 30 feet into the overlying strata. Flat sheets are a form of deposit that may occur anywhere, proceeding from the vertical crevices; but they are chiefly limited to the lower part of the formation, and are even found in the Trenton limestone, as well as in the true lead-bearing rock. 1840.. Features of distribution of the ore and of open- 1841.. Years. 1827. 1829. 1821 to-'23 1828. Pigs. 4.790 335,1301842.. 447,909 31,858,680 2,503 175,220 1843.. 558,261 39.148.270 9,490 664.530 1844.. 624,672 43,726,040 18,700 958,842 1845.. 74,130 5,182,180 1846.. 152,655 11,105,510 |154.. 190,620 13,343,150 1848.. 119,060 8,323,998 1849.. 778,408 54.494.850 51,268,219 54,085,920 44,025,880 1835. 1836. 1837. 1830.. 1832. 1833. 1834. 1838. 91,170 6,351.793 1850.. 568,589 The most available crevices being worked out, and the greater attractions of the newly discovered gold region of California drawing the miners away, the production declined from a maximum of about 25,000 tons in 1847, till in 1853 it amounted to only 13,800 tons. Since that time, the transportation from the mines being in part by the railroads instead of altogether by the river as before, no exact record has been kept of the quantities. The following are given in the Iowa geological report as the amounts of lead received at Chicago and St. Louis for the years named; but to represent the actual production an unknown amount should be added for the home consumption, which has been largely increased by the establishment of white lead and shot works in the region: Tons of lead received.] 1853. At Chicago. Total.. 1,452 14,248 1854. 1856. 1857. 1855. 15,700 12,018 14,206 8,995 १ ers's mines. The most productive mines have been found in Washington co., but many others are met with in the S. E. part of the state. The geological formation in which they are chiefly contained lies below the Trenton limestone, and by Prof. Swallow is regarded as the equivalent of the calciferous sandrock of the New York reports, which appears to be here represented by a group of alternating beds of magnesian limestone and sandstone. The 2d and 3d of these limestones below the Trenton limestone have produced the principal supplies of the ore; and in some localities in the state lead is found in the coal measures, even in the coal beds themselves, and has been worked to some extent in the carboniferous limestone called the Archimedes or mountain limestone. The 3d magnesian is regarded by the Missouri geologists as corresponding to the lower magnesian of the upper lead region, which is there unpro6,847 ductive. The mines are frequently along the line of meeting of the limestone with granitic rocks, though in this position the deposits are The sum given for the receipts at St. Louis in either superficial or run between the calcareous 1857 includes the receipts from the Missouri strata, without penetrating the granite. Various mines, which however are but trifling. A more other ores are found associated with the galena, complete table, including domestic receipts, for- as the carbonate of lead, called by the miners eign imports, and invoice value, will be given, dry bone, white mineral, &c., the sulphuret and after noticing the lower or Missouri mines. Lit- silicate of zinc, known as black jack, pyritous tle of the products of the western mines now iron and copper, and at some of the mines, as reaches the Atlantic coast; in 1857 only about Mine La Motte, carbonate of copper and black 100 tons arrived at New York. The seaboard oxides of manganese and cobalt. The surface is almost entirely supplied from the English and of the country in the lead region is strewed Spanish mines.-The Missouri lead mines were with crystallized quartz derived from the leaddiscovered and first worked in 1720 by Renault bearing rocks, and called by the miners "minand his mineralogist La Motte, who came out eral blossom." The modes of occurrence of the with a large party under authority of a patent lead ore are generally the same as those already granted by the French government to John described as common to the northern mines. Law's famous company. Mine La Motte and The openings on the vertical fissures vary from the Potosi lead mines were discovered and the capacity of a cubic foot to 10 or 12 feet opened by them; but little however had been square, and when very small are called pockets. done up to Renault's return to France in 1742. They do not preserve a uniform course, but The only smelting of the lead ores appears to connect one with another by passages filled have been done on log heaps, a wasteful pro- with material different from the walls, and excess, much practised even of late years. In tending toward every point of the compass. 1798, as stated by Schoolcraft in his "View of Vallé's mine in St. François co. and Perry's on the Lead Mines of Missouri," p. 19, Moses Aus- its extension S. present a remarkable network tin of Virginia, having obtained a grant of land of veins spread over an area of about 1,500 feet from the Spanish government near Potosi, sunk in length by 500 in breadth, ranging N. W. and the first regular shaft, and erected a reverbera- S. E. They are also examples of mines of a more tory furnace, and also a shot tower. According permanent character than are found in the to the same authority, there were 45 mines in northern lead legion. Vallé's mine was discovoperation in Missouri in 1819, giving employment ered in 1824, and it is believed has been workto 1,100 persons; in 1811 Mine Shibboleth pro- ed ever since without interruption. There are duced 3,125,000 lbs. of lead from 5,000,000 lbs. 14 shafts upon it, and 8 more principal shafts of ore. From 1798 to 1816 Mine à Burton and upon Perry's mine. Of all these, only 2 are the Potosi diggings were estimated to have less than 50 feet deep; 6 exceed 110 feet, and produced over 500,000 lbs. annually; and from one of them is 170 feet deep. They are in gra1834 to 1837 the production of Mine La Motte vel and clay 10 to 30 feet, then in a light-colored is rated at an average of 1,035,820 lbs. of lead silicious magnesian limestone, which passes beper annum. For 14 years succeeding 1840 Dr. low into another variety of very close texture Litton in his state geological report makes the and known by the miners as the cast-steel rock. annual average of all the mines over 3,833,121 Three series of caves are found, the 2d set 18 lbs.; and yet in 1854 he thinks there were or 20 feet below the first, and the 3d about 8 scarcely 200 persons engaged in mining, beside feet below the second. The middle set has been those employed at Perry's, Vallé's and Skew- most worked. They run out in every direction, and in some instances communicate by chimneys with the series above or below. They are filled with clay, loose rock, and ore, the last often an intermixture of galena and silicate and carbonate of zinc, which requires roasting and washing to prepare it for the furnace. From 1824 to 1834 Vallé's mine, it is estimated, produced about 10,000,000 lbs. of lead, and about as much more in the next 20 years; Perry's mine about 18,000,000 lbs. from 1839 to 1854. These are remarkable instances of lead mining regularly prosecuted for so many years at one locality. But excepting at these and Skewers's mine there appears to have been little regular mining conducted in the state in 1854. Dr. Litton was of opinion that of all the lead obtained in Missouri had been from clay diggings overlying the rock. These operations have often been highly productive, but were carried on without system and without capital by men who had no interest or ability to prosecute the work in the rock, and thus the more permanent deposits have been passed over. The estimates of the production are based upon very uncertain data, no records for the most part having been preserved of the lead mined and smelted.-The table below, compiled for Hunt's "Merchants' Magazine," July, 1859, presents various data of interest relative to the lead business of the United States; but the production is imperfectly represented for late years by the figures in the second column, for the reasons that other outlets are now opened to the eastern market, and the consumption about the mines has largely were reexported to foreign countries. The exports of American lead were valued at about $30,000, beside a small quantity of manufactured lead.-Metallurgic Treatment. As lead ores are ordinarily received from the mines, they require preparatory treatment for the furnace. The earthy matters adhering to them, as clay and sand, may be washed away by exposing the ores to a current of water; but before the intermixed gangues and foreign ores can be separated, the lumps must be reduced to small fragments, and the fine materials be subjected to a systematic dressing by the process of jigging or other convenient methods of sorting materials according to their different specific gravities. The coarse lumps may be reduced by hand upon an iron-top table with the so called bucker, a thick cast iron plate with a face 3 inches square and a socket on the upper side for a handle; or they may be passed through the crushing rolls, of which two or more pairs are commonly employed, one set above the other. After the ores have been dressed and sorted into heaps, it is the practice at some of the European smelting establishments, as in Cornwall, to roast at a moderate heat about one half of each heap in a special calcining furnace of the reverberatory class. The effect of this is to produce considerable quantities of sulphate of lead, which is more fixed in the smelting furnace, and consequently diminishes the loss that would be experienced by volatilization of the sulphuret. Being then mixed with the unroasted sulphuret and subjected to the heat of the smelting furnace, one equivalent of sulphate and one of sulphuret afford just 2 equivalents of lead and 2 of sulphurous acid, the last escaping; thus, PbO, SO,+PbS= 2Pb+2SO2. Hence the best results are obtained when the two compounds are in equal atomic proportions. If the sulphate is in excess, sulphite of lead will be formed and remain unreduced. As smelting is conducted in the reverberatory furnace, the roasting is effected upon the surface of the charge; and when it has proceeded sufficiently far, the whole is stirred together and subjected to the reduction heat. In the blast furnace, as the operation is conducted in this country, the smelter seeks to attain the same end by a surface roasting with each addition to the charge before putting on the blast. Two kinds of furnaces are employed in the United States for smelting lead ores, the reverberatory and the Scotch hearth. Beside these, a small high or blast furnace is used in some parts of Europe for silicious refractory ores. Reverberatory furnaces are constructed on the general principle of those described for smelting copper ores or puddling iron. Those for lead have a shallow basin-shaped hearth, the greatest depression beneath the arch being about 2 feet. The aperture into the flue is only about 6 inches high, and the space over the fire bridge is 14 inches. The dimensions, however, vary in different districts. The sole is about 8 feet in length by 6 in breadth, and formed of the slags of previous operations. The charge is supplied through the top by a hopper, and, being immediately spread over the hearth, is afterward worked through apertures in the side, by which air also is admitted as required. On one side holes are also made for the scoria and metal to flow out; or, as at the western mines, the discharge may be at the extreme end, the hearth being made to slope from the bridge. The charge varies in different countries; in Derbyshire and near Alston Moor it is composed of several varieties of ore suitably mixed, and weighing about 2,000 lbs. and sometimes 2,500 lbs.; in Wales it is from 20 to 24 cwt., and in Wisconsin from 45 to 60 cwt. In Yorkshire 7 cwt. of bituminous coal are consumed to the ton of lead, and the smelting of each charge occupies 5 to 7 hours. A common allowance of fuel iston to the ton of lead. In Wisconsin the working through one charge occupied 9 hours, with the consumption of one cord of wood and the production of 5,250 to 5,810 lbs. of pig lead. The slag produced by these furnaces is rich in lead, and is saved to be treated by other processes. In the operation the heat is very slowly brought up if the ore has not been previously roasted, and the furnace is kept close, with a small aperture only open for the air to enter. In a short time the charge becomes heated and the sulphur slowly consumes. The operation of rabbling or stirring over the materials is then commenced, and continued at intervals for nearly 2 hours. The skimmings of the receiving pot and any rich slags are thrown into the end of the furnace furthest from the fire, and soon cause a separation of metal as they react upon the roasting ores; this metal is occasionally drawn off. Some coal is usually worked into the molten mass to aid the reduction and protect the metal from oxidation. In England, after the roasting process is far advanced and the rich slags introduced have been partly smelted, the doors are all opened and the charge is allowed to become partially cool. To this soon succeeds the second stage or "firing," the first being the roasting. In half an hour the furnace becomes red-hot and the materials begin to flow. The working doors are then opened and the charge is pushed back and spread out, and quicklime is spread over the surface, the effect of which is to thicken or "dry up" the slags, and protect the metal from oxidation, but more especially, in case of the ores being silicious, to break up the compound formed of silica and oxide of lead and set the latter free. Another partial cooling and subsequent firing succeed, and these processes continue to be repeated, till in about 4 hours the tap hole is opened for the flow of the metal, the slag floating upon it being pushed back to be further treated by renewed melting, or to be dried up with quicklime and taken out from the door in the opposite side of the furnace. Six hours are consumed in the whole operation, thus allowing a succession of 4 every 24 hours; though for a week's work 16 charges are sometimes admitted, and 22 are a maximum. Better results are obtained by this VOL. X.-25 slow and interrupted process than by more hurried ones, the yield being 75 per cent. or more of lead. From the rich galenas of Wisconsin it was formerly thought that no more than 65 per cent. could be thus obtained, the remainder going with the slags, the principal bulk of which as in England were afterward worked over in small blast furnaces or slag hearths. Those employed at the West are in fact nothing more than large crucibles built in brickwork open at top, with an aperture in the back for the tuyère, and another at the base in front for the metal after it is separated to run out into the receptacle made in the ground in front of the furnace. The cinder flows out also with the lead and floats over its surface into a second receptacle. The separation, however, is generally far from being completely effected. The fuel employed is charcoal. -The common blast furnace or Scotch hearth is a cheap, convenient, and easily managed furnace, much used at our own mines and in the northern part of England. In its improved form with the hot blast arrangement, as introduced in the United States, and furnished by some of the iron founderies ready to be set up, it is a cast iron box about 2 feet square and one foot deep, open at top, with the sides and bottom 2 inches thick. A sloping shelf, called the hearth, is attached to the front edge for the lead to flow down, and for holding the materials of the charge when these are occasionally spread out in the course of working the furnace. Over the reservoir is fitted a cast iron chest, open in front and at top, with sides and back about 14 inches high. These are made hollow, the iron walls inch thick enclosing a space of 4 inches. The blast is made to enter at one side, and passes out at the other by a pipe, which bends round and enters the tuyère set in the back of this chest, 2 inches above the top of the reservoir. When in use this reservoir continues full of melted lead, and the excess as produced from the charge floating upon it flows down the hearth into the pot set to receive it. Under the pot a small fire is kept up, so that the lead may be ladled from it as convenient into the moulds. The furnace is kept in continual operation by introducing new charges about every 10 minutes, and working them down as they become roasted at the surface. Before adding more ore the blast is turned off, and the charge already in the furnace is drawn forward on the hearth. Billets of light dry pine wood are then thrown in against the tuyère, and the charge is thrown back with the addition of fresh ore upon the wood. The blast is then let on again, and in a few minutes the charge is stirred over. It is advantageous to use a blast with more pressure than that obtained from the fan; cast iron blowing cylinders are the most effective. No other fuel is required but light pine wood; but in England bituminous coal is used. The combustion of the sulphur in the ore produces a large portion of the heat required. Fluor spar is sometimes used as a flux, and also blacksmiths' cinders and bits of iron, the effect of which is to desulphurize the galena by the affinity of the iron and sulphur. The inner walls of the air chest would be rapidly, destroyed by the sulphur, but for the cooling effect of the air driven behind them; this also tends to keep them of uniform temperature. In smelting about 5,000,000 lbs. of lead at Rossie with this class of furnaces, the consumption of fuel was less than cord of wood to 2,000 lbs. of lead. Each furnace produced an average of 7,500 lbs. of lead every 24 hours, employing 2 lead smelters and 2 assistants, or one of these every 12 hours. The cost for wood was $1.50 and labor $5-$6.50, or $1.75 per ton. In Wisconsin, before the use of the hollow air chest, the expense of one furnace shift, continuing till 30 pigs weighing 2,100 lbs. were produced, and usually occupying 8 to 10 hours, was about $4 for labor and $1.50 for fuel, charcoal and wood, both of which bore a very high price in the prairie region. In England the ore for the Scotch hearth is first roasted in a reverberatory furnace. In the Hartz mountains and some other parts of Europe poor silicious galenas are sometimes smelted in small blast furnaces, measuring about 3 feet across inside, and 20 to 23 feet in height, and surmounted by flues, which are made to wind up and down in the masonry for the purpose of arresting the metallic portions of the escaping gases. Such ores cannot be treated like pure galenas to afford first a sulphate, which shall react upon the sulphuret; for the silica would seize upon the oxide of lead of the sulphate and form with it a refractory silicate. A flux therefore is employed of metallic iron, in the form of scales, cinders, or of cast iron obtained by beating up the cinders from iron smelting furnaces. The charges are complicated mixtures of ore, containing about 24 per cent. of lead, various furnace products as scoriæ and litharge, and finally the granulated iron or scales, all properly apportioned according to their chemical composition and the reactions required.-Considerable loss is experienced in smelting lead ores from the tendency of their particles to escape in the form of white fumes or lead ashes, that are seen pouring out from the chimney flues. Not only is a loss of lead thus occasioned, but serious injury is done to the vegetation around, and the cattle and dogs in the neighborhood are sometimes destroyed. An interesting paper upon this subject was read by Dr. George Wilson to the royal society of Edinburgh, and published in the "Monthly Journal of Medical Science," May, 1852. He had been called upon to investigate the cause of the death of 13 horses and a number of cows, supposed to have been poisoned near some lead furnaces, and had found the herbage and the water drunk by the animals impregnated with carbonate of lead; and the metal was detected in the organs of the body, especially the spleen, which Dr. Wilson suggests is the most convenient organ to submit to this examination. Attempts have been made to remedy the evil by conducting the fumes brought together from the different furnaces through chambers, in which they are cooled and condensed by showers of water. But these arrangements, as also drawing the gases through cold water to cause the metallic compounds to be retained, involve obstructions to the draft, and require exhausting machinery at the extreme end to supply its place. At the great exhibition of 1851 a model of the apparatus of the duke of Buccleuch, in use at his works in Dumfriesshire, was exhibited, the original of which had proved perfectly effectual in saving the lead and preventing all the evil effects consequent on the escape of the fumes. The arrangement however is costly, and adapted only to large establishments. The water used for showering is conducted into tanks in which it deposits the metallic particles it takes up. The specimens of lead ashes thus recovered were said to contain about their weight of pure lead, and nearly 5 oz. of silver to the ton.-Lead varies much in purity, according to the ores from which it is obtained and the methods of reduction adopted. Generally it is more pure the lower the temperature at which it is smelted; but some ores are intermixed with iron pyrites, blende, and sulphuret of antimony, to such a degree that more or less iron, zinc, and antimony remains alloyed with the lead, seriously injuring its quality, especially for the manufacture of white lead, and also increasing its hardness. In some of the European works special methods of purification are found necessary after the metal has been obtained. It is not so with American lead, the quality of which is remarkable for its softness and purity. Spanish lead received in the United States is not so good, but is better than the English. Silver accompanies most of the foreign ores, and is very commonly present in European lead in sufficient quantity to render its extraction profitable. The method of effecting this was formerly to melt the lead upon cupels placed in reverberatory furnaces, and, by a current of air playing over the surface of the metal, convert it into litharge or oxide of lead till the silver remained behind. This operation was hardly remunerative with lead yielding less than 10 oz. of silver to the ton. The large cupels used in extensive refineries are made in an iron frame usually of oval form, the outer rim being an iron bar inch thick and 4 inches wide bent around and the ends welded together. The larger diameter may be 4 feet and the lesser 2 feet. Cross bars of iron support the pounded bone ashes, mixed for the best cupels with their bulk of fern ashes or their weight of pearl ashes, or for common cupels with very fine cinders. When the pigs of lead are thoroughly melted upon one of these cupels, a strong current of air is blown over the surface in the direction of the longer diameter, and the oxide of lead, as it is formed, is swept on over the further edge of the cupel and falls into a receptacle conveniently placed for its removal. In the Hartz, at Clausthal, the refining is done directly upon the floor of the reverberatory furnace, which is specially < |