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but are lost in the lower strata of the limestone, and where the upper strata of the formation appear, these cover over the veins, and are consequently known as the cap-rock. In the fissures or crevices the galena is found, sometimes in loose sheets and lumps embedded in clay and earthy oxide of iron, and sometimes attached to one or both walls. It is rarely so much as a foot thick. No other ores are found with it, except some zinc blende and calamine, and occasionally pyritous iron and copper. The lead contains but a trace of silver. The fissures, as they are followed beneath the surface, sometimes expand in width till they form what is called an "opening;" and the hollow space may go on enlarging till it becomes a cave of several hundred feet in length and 30 or 40 in width. Their dimensions are, however, usually within 40 or 50 feet in length, 4 to 8 in width, and as many in height. The walls of the openings often afford a thick incrustation of galena, besides more ordess loose mineral in the clay, among the fragments of rock, with all of which the caves are partially filled. Flat sheets of ore often extend from the vertical fissures between the horizontal limestone strata; these are more apt to contain blende, and pyrites, and calcareous spar than the ore of the vertical crevices. Besides these modes of occurrence, galena is found in loose lumps in the clayey loam of the prairies. This is called float mineral, and is regarded as an evidence of productive fissures in the vicinity.

The galena occurs under a variety of singular forms in the crevices. It lines curious cavities which extend up in the cap-rock, terminating above in a point, and which are known as chimneys. Upon the roofs of the openings it is found in large bunches of eubical crystals, and the same are obtained lying in the clays of the same openings. A flat sheet of the ore was worked in Iowa that was more than 20 feet across and from 2 to 3 feet thick, each side of which turned down in a vertical sheet, gradually diminishing in thickness. It yielded 1,200,000 lbs. of rich galena, and more still remained behind in sight. The crevices near Dubuque are the most regular and productive of any in the district. One called the Langworthy, on a length of about three-fourths of a mile, has produced 10,000,000 lbs. of ore. On the main fissure there were usually three ranges of crevices one above another, widening out to 15 or 20 feet.

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The smelters of this region form a distinct class from the miners, of whom the former buy the ores as these are raised, and convert them into metal in the little smelting establishments scattered through the country. The lead has been principally sent down the Mississippi river to Saint Louis and New Orleans; but a portion has always been consumed in the country, and some has been wagoned across to Milwaukee before the construction of railroads, which since 1853 have afforded increased facilities for distributing in different directions the product of the mines. The only records of the amount of lead obtained are those of the shipments down the river. The following table presents the number of pigs shipped from the earlier workings to 1857; the figures for 1841 to 1850, inclusive, being furnished to Dr. Owen's Report of 1852 by Mr. James Carter, of Galena. The pigs weigh about 70 lbs. each.

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The lead region of Missouri was first brought into public notice by the explorations of the French adventurer, Renault, who was sent out from Paris in 1720, with a party of miners, to search for precious metals in the territory of Louisiana, under a patent granted by the French government to the famous company of John Law. Their investigations were carried on in the region lying near the Mississippi and south of the Missouri river; and here, though they failed to find the precious metals they were in search of, they discovered and opened many mines of lead ore. A large mining tract in the northern part of Madison county is still called by the name of their mineralogist, La Motte. Their opera

every

and Perry's mines, both situated on the
same group of veins, which form a network
of fissures and openings running in
direction and spreading over an area of
about 1,500
1,500 feet in length by 500 in
breadth, the extension of which is from north-
west to south-east. These mines have been
steadily worked since 1824, and 22 shafts
have been sunk upon the fissures, six of
which are over 110 feet deep, one is 170
feet deep, and only two are less than 50
feet. For the first 10 to 30 feet they pass
through gravel and clay, below this through a
silicious magnesian limestone of light color,
and then enter a very close-grained variety
of the same, called by the miners the cast
steel rock. A succession of openings are
encountered, which are distributed with
considerable regularity upon three different
levels. Those of the middle series have
been the most productive. Sometimes
chimneys connect them with the caves of
the tier above or below. The portion of
these mines on the Vallé tract produced,
according to the state report, from 1824 to
1834 about 10,000,000 pounds of lead, and
in the succeeding 20 years about as much
more; and Perry's mine from 1839 to 1854
has produced about 18,000,000 pounds.

tions, however, were altogether superficial, | them black jack, and the silicate of zinc. and the lead they obtained was wholly by Iron and copper pyrites are often seen, and the rude and wasteful process of smelting at Mine la Motte are found the black oxides the ores upon open log-heaps-a practice of cobalt and manganese associated with which even of late years is followed to some the carbonates of lead and copper. Nearly extent. Up to Renault's return to France, all the mining operations have been mere in 1742, little progress had been made in superficial excavations in the clay, which the development of this mining district. The were soon exhausted of the loose ore and next step was made by one Moses Austin, abandoned. But to this there are some reof Virginia, who obtained from the Spanish markable exceptions of deeper and more government a grant of land near Potosi, and permanent mines than are known in the commenced in 1798 regular mining opera-northern lead regions. Such are Vallé's tions by sinking a shaft. He also started a reverberatory furnace and built a shot tower. Schoolcraft states in his "View of the Lead Mines of Missouri," that there were in 1819 forty-five mines in operation, giving employment to 1,100 persons. Mine å Burton and the Potosi diggings had produced from 1798 to 1816 an annual average amount exceeding 500,000 pounds; and in 1811 the production of Mine Shibboleth was 3,125,000 pounds of lead from 5,000,000 pounds of ore. At a later period, from 1834 to 1837, the several mines of the La Motte tract produced, it is estimated, 1,035,820 pounds of lead per annum. From 1840 to 1854 the total yield of all the mines is stated by Dr. Litton in the state geological report to amount to over 3,833,121 pounds annually. At the close of this period it had, however, greatly fallen off, there being at that time scarcely 200 persons engaged in mining, besides those employed at the three mines known as Perry's, Vallé's, and Skewers'. The principal mines have been in Washington, St. Francis, and other neighboring counties. The ores are found in strata of magnesian limestone of an older date than the galena limestone of Wisconsin, and supposed to lie, with the sandstones with which they alternate, on the same No accurate estimates have been pregeological horizon as the calciferous sand served of the total production of the Misrock, which is found in the eastern states souri mines. This has always fallen far overlying the Potsdam sandstone. Some of the mines are at the contact of the horizontal limestone with granite rocks, but the ores in this position are only in superficial deposits or in layers included in the limestone. In their general features the veins do not differ greatly from those of the northern mines. Some of them, however, contain a larger proportion of other ores besides galena, as well as a greater variety of them. Carbonate of lead, called by the Miners dry bone and white mineral, is more abundant, and also blende, called by

short of the yield of the northern mines. From 1832 to 1843 it is, reported as running from 2,500 to 3,700 tons per annum, while that of the northern mines in the same time was from 5,500 to 14,000 tons, and in 1845 it even exceeded 24,000 tons. In 1852 Mr. J. D. Whitney estimated that the production in Missouri had fallen to 1,500 tons, or less; and from that period it has probably not advanced. As this decrease in the supply has been going on while the price of lead has risen to nearly three times what it was in 1842, the cause is probably

owing to the mines themselves being in former metal. As the production of the great part exhausted. The only sufficient United States fell off that of Great Britain sources known from which the increasing increased from 64,000 tons in 1850 to 73,129 supplies required from year to year can be tons in 1856, and 96,266 tons in 1857, thus furnished, are the mines of Great Britain considerably exceeding one-half of the whole and Spain, though should the argentiferous production of the globe in this metal, which lead mines of Mexico ever be worked for in 1854 was rated at about 133,000 tons. the lead as well as the silver they contain, At that time the production of Spain was they might furnish large quantities of the rated at 30,000 tons, and of the United States at 15,000 tons.

Years.

Pig lead from
American mines
received at St.
Louis and New

Orleans.

lbs.

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For the year ending June 30, 1859, the imports of lead are given at 64,000,000 pounds, worth nearly $2,700,000. Of this about $57,000 worth were re-exported to foreign countries, besides American lead to the value of $30,000, and a small amount of manufactured lead.

LEAD SMELTING. Lead SmeltinG. The lead mines of the United States being scattered over, wide territories, and their products being nowhere brought together in large quantities, the process of reducing the ores has been conducted in small establishments and by the most sim

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ple methods. The earlier operations were limited to smelting the ores in log furnaces. Upon a layer of logs placed in an inclosure of logs or stones piled up, split wood was set on end and covered with the ore, and over this small wood again. The pile was fired through an opening in front. combustion of the small wood removed from the ore a portion of the sulphur, and the re、 duction was completed by the greater heat arising from the burning of the logs. The lead run down to the bottom and out in front into a basin, whence it was ladled into

the moulds. The loss of metal was of to receive the melted lead that overflows, course very large; but a portion was recovered by treating the residue in what was called an ash furnace. The process is still resorted to in places where no furnaces are within reach. But wherever mines are opened that promise sufficient supplies of ore, furnaces are soon constructed in their vicinity. Those in use are of two sorts: the Scotch hearth and the reverberatory. Besides these, another small furnace is often built for melting over the slags. This is little else than a crucible built in brick-work, and arranged for the blast to enter by an aperture in the back, and for the metal to flow out by another opening in front.

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and conduct it by the groove into the basin,
B. In this it is kept in a melted state by a
little fire beneath, and, as convenient, the lead
is ladled out and poured into moulds.
Dis
a hollow shell of cast iron of an inch thick,
its inner and outer sides inclosing a space of
4 inches width. Into this space the blast is
introduced at E, and becoming heated,
passes out at F, and thence through the
curved pipe into a tuyere, T, cast in the air-
chest 2 inches above the level of the lead
reservoir. Before commencing operations
this reservoir is to be filled with lead, and is
thus kept so long as the furnace is in use;
the process being conducted upon the sur-
face of the melted metal. The furnace may
be kept in continual operation by adding
new charges of galena every ten or fifteen
minutes, and working them down after they
have become roasted at the surface. The
fuel employed is dry pine wood split into
small pieces, and billets of these are thrown
in against the tuyere just before each new
charge of ore, that already in the furnace
being raked forward upon the hearth to
make room for the fuel, and the blast being
temporarily turned off. The old charge is
then thrown, together with fresh ore, upon
the wood, and the blast is let on, when the
heat and flame immediately spread through
the materials. The sulphur in the ore serves
itself as fuel, accelerating the process by its
combustion, and in a few minutes the
whole charge is stirred up, spread out on the
hearth, and the hard, unreduced. fragments
are broken in pieces by blows of the shovel.
Slaked lime is sometimes added in small
quantity when the partially reduced ore be-
comes too soft and pasty by excess of heat.
Its effect is to lessen this tendency rather by
mechanical than chemical action.
If any
flux is used, it is fluor spar, blacksmith's
cinders, or bits of iron. The latter hasten
the reduction by the affinity of the iron for
the sulphur of the ore. The cast iron of the
air-chest is protected from the action of the
sulphur by the cooling influence of the air
blown in; and this is also advantageous by
its keeping the furnace from becoming so
hot, that the galena would melt before losing
its sulphur, and thus form combinations of
exceedingly difficult reduction. A fan, run
by steam or water power, is commonly em-
ployed for raising the blast; but as this gives
little pressure, it is replaced to great advan-
tage by blowing cylinders, with an air-

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sides being kept open at the same time to allow free access of air. The oxidation of the sulphur is expedited by almost constant stirring of the charge, which brings fresh portions to the surface, causing an evolution of white fumes. As these begin to diminish, the fire is started on the grate, and the heat is raised till the charge softens and the pieces of ore adhere to the rake. The doors are then closed, and the fire is urged for a quarter of an hour, when the smelter opens the door to see if the metal separates and flows down the inclined hearth. If the separation does not go on well, it is hastened by opening one of the doors, partially cooling the furnace, and stirring the charge. The fire is then again urged. If the slags which form seem to require it, he treats them with

receiver for giving regularity to the current of air. With such an apparatus, the smelter can apply the blast with great advantage at times to help loosen up the charge and throw the flame through every part of it. The ores are prepared for smelting by separating from them all the stony and clayey particles, and as much as possible of the blende and other impurities that may accompany them. This may require a succession of mechanical processes, in which the ores are crushed to fine fragments and dressed by jigging and screening under water. Not only is the labor and cost of smelting reduced by the purity of the ore, and especially its freedom from blende and pyrites, but the quality also of the metal is thereby improved. Lead that contains iron is not adapted for the manufacture of white-lead. a few shovelfuls of lime and fine coal; and The American metal being generally free from this brings a higher price than Spanish or English lead. With pure ore a cord of wood may be made to produce four tons of lead; and each furnace 7,500 lbs. every 24 hours; a smelter and his assistant managing the operation for 12 hours. At Rossie large quantities of lead have thus been smelted at a daily cost for labor of $5, and for fuel of $1.50, making $1.75 per ton. In Wisconsin, before the use of the hot blast, each furnace-shift was continued from 8 to 10 hours, until 30 pigs of lead were produced of 2,100 lbs. weight, at an expense of about $4 for labor, and $1.50 for fuel.

The other form of furnace-the reverberatory-resembles others of this class employed in smelting copper ores. The sole, or hearth, upon which the ores are spread, is about 8 feet in length by 6 in breadth, and is made to incline rapidly toward an aperture on one side, or at the end under the chimney, and out of which the lead is allowed at the end of each smelting to flow into a receiver outside. The charge is supplied either through a hopper in the arched roof, or through the holes in the sides, which also serve for admitting the pokers used by the workmen to stir up the charge. Unless the galena has been previously calcined or roasted-a process necessary for poor ores only--this is the first thing to be attended to in all the smelting operations. In the large charge of 30 cwt. of ore this usually takes the first two hours of the process, and is effected in great part by the heat remaining in the furnace from the preceding operation, the doors at the

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when, after having flowed down into the lower portion of the hearth, they are brought into a doughy consistency, the smelter pushes the slag to the opposite upper edge of the hearth, from which it is taken out through a door on that side by his assistant, while he lets off the lead into the receiver.

The separation by this method is not so perfect as by the Scotch hearth, and the expense of fuel is greater; but the reverberatory is worked without the necessity of steam or water power, which is required to raise the blast for the other process. The slags of the reverberatory contain so much lead that they are always remelted in the slag furnace. Those of the Scotch hearth, when pure ores are employed, are sufficiently clear of metal without further reduction. In Europe other sorts of furnaces are in use, which are adapted particularly for ores of poorer quality than are ever smelted in the United States.

In the Hartz mountains, at Clausthal, argentiferous silver ores containing much silica are worked in close cupola furnaces, into which only enough air is admitted to consume the fuel. The object is not to roast out the sulphur, but to cause this to combine with the granulated cast iron or with the quick-lime, either of which is mixed with the ores to flux them and form a fusible compound with the sulphur, through which the metallic lead can easily find its way to the bottom. The production of a silicate of lead is thus avoided, which is a difficult compound to reduce, and is always formed when much silica is present. present. This process

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