In Virginia the slate is more soft, the fissures open more readily, and the whole vein shows the appearance of soft slate. This slate is impregnated with small quartz veins, from one-eighth to one-half an inch, and often two inches thick. Where these quartz veins are thin and in great numbers, the ore is always found to be richest in gold. This feature of the ore is well developed throughout Virginia, and at Gold-hill, North Carolina. The vein stone of the gold bearing veins is strongly impregnated with oxide of iron, showing evidence that this iron is derived from pyrites. Many of these veins have been traced to that depth where the pyrites are not oxidized; here it appears in its perfect crystal form and is profusely distributed through the slate. The oxidation of this pyrites appears to depend upon the penetrability of the rock by atmospheric agents; where the slate is soft, it is oxidized to the depth of fifty to one hundred and fifty feet; where it is hard, the oxidation hardly reaches ten to twenty feet. Where the pyrites is not oxidized, the extraction of the gold is attended with considerable more expense than from soft slate and oxidized rites. The crushing of the hard slate is more expensive; the sulphur of the pyrites destroys a large portion of quicksilver in the amalgamation, and the gold cannot all be extracted; the largest portion of it remains inclosed by the sulphuret of iron, and can be liberated only by destroying that envelope.

py

The southern gold formation extends at least five hundred miles; the breadth of the gold bearing strata in which the gold is imbedded is from five to twenty miles in width; and if we consider the depth of the veins, which by some are assumed to be two thousand feet, the amount of gold ore in this region is justly entitled to be regarded as a great source of national wealth. Various experiments have been made to faciliate the working of the sulphurets, but none of them have so far succeeded yet, as to make it profitable to work the poorer classes of ores. In Virginia and North Carolina gold ores are worked with profit which yield only seven and ten cents of gold to the bushel. The pennyweight of gold from the Virginia mines has generally been worth from 90 to 92 cents. North Carolina gold contains more silver, and a pennyweight has seldom exceeded 90 cents, and in many ranged from 80 to 90 cents, while the gold of California has been from 75 to 90 cents.

Silver has been derived in the United States exclusively from the sulphuret of lead. Until recently the only establishment for its extraction was that of the Washington Mining Company in North Carolina. The ore which this Company worked has yielded from 200 ounces to 300 ounces of silver to the ton of lead. It contains on an average eight per cent. of lead; the other matter is zinc, iron, copper, tin and sulphur. The silver has been worth

$1 80 the ounce, because it was alloyed with a large portion of gold which raised its value far above that of pure silver. We are uninformed respecting the amount of silver obtained from the ores in North Carolina.

The extraction of silver from its ore is generally conducted on the same principles-but the operations at the Washington mine which are thus described, present one of the most difficult cases, on account of the composition of the ore. It consists chiefly of brown sulphuret of zinc, which is largely mixed with galena, copper, and iron pyrites; it contains silver, gold, and other metals. The ore as it comes from the mine is broken into coarse fragments, and roasted in heaps in the open air. The roasting is performed altogether by wood and wood charcoal. After the first roasting the piles are picked over for the ore which is well roasted, and that which is too much roasted. This is brought to the stampers, crushed into a fine powder, and washed, so as to carry off all the oxidized zinc and quartz. If the ore, after its being crushed, is found to be imperfectly roasted, it is returned to the yard and once more subjected to roasting. That part of the ore which is rejected in the yard is piled and roasted along with some fresh ore from the mine. In this way it may happen that some of the ore is exposed to several heats. The roasting operation is not considered to be finished until all the sulphuret of zinc is destroyed; that is, until the zinc is deprived of its sulphur and converted into oxide of zinc, in which form it may be washed away by the water at the stamping-mill.

The finely powdered ore consists now chiefly of galena, or in case the roasting operation is well performed, of oxide of lead, oxide of iron, oxide of copper, silver and other matter. This ore is brought to the smelting-furnace, called a high-furnace, and here smelted along with some fluxes by charcoal. In fig. 1 such a

furnace is represented; it is a solid work of masonry, to retain its heat if once thoroughly heated. The fire is urged by cylinder bellows, driven by a steam engine; the air to the furnace is supplied at the tuyere m. In consequence of the alternate charges of coal and ore, the basin or hearth g is regularly supplied with metal, which is removed at certain intervals of time, so as to afford room for fresh metal and cinder. In this manner about one ton of lead is obtained in 12 hours, which is removed and put aside for refining. The composition of the ore, which makes its perfect roasting difficult, renders it necessary to make large additions of iron ore to the posts of ore. The iron oxide, which is reduced in presence of carbon in the furnace, will absorb the sulphur from the other metals in case there is any sulphur left after roasting. This circumstance renders the operation tedious and slow. It cannot be avoided but by perfect roasting, which may be considered practicably impossible in this instance. The presence of zinc is what renders the operation tedious and expensive. If the zinc is not removed to a large extent, it will, in smelting the ore, carry off by evaporation much of the other metals, gold and silver not excepted. The sulphurets of zinc and lead are very fusible if in contact. In roasting the ore these two sulphurets will invariably melt together, which causes the roasting process to be either very expensive or imperfect. All experience with similar ore in other parts of the world is confirmatory as to the operation being expensive.

The lead from these blast-furnaces is transferred to the refining-furnace. Formerly the English refining furnace was used as it is represented in fig. 3, in a longitudinal section. Here is a

FIG. 8.

double, or two furnaces represented, which, as is shown, are reverberatory furnaces. The fireplace a throws the flame over the hearth or cupel into a chimney, which is provided with a sliding door at ff to shut off the draft and prevent the fumes of metal from escaping through the stack. The cupel is formed of several layers of bone-ashes, mixed with wood ashes; this mass is rammed into an iron hoop when in a moistened condition. The form of this cupel is represented in fig. 2; from above it is a concave egg-shaped dish, of about 5 inches thick, the largest diameter

being 4 feet, the smallest 2 feet. When the furnace and cupel are heated, the lead, previously melted in an iron pot, is cast into it; and now the bellows, which are represented in fig. 4, are set to work, and a gentle current of air is thrown over the hot surface. The action of the blast is here twofold; it oxidizes the lead and forms litharge of it, and drives by its force the melted litharge to the opposite side of the blast, or the tap-hole, where it flows out and falls into an iron basin, from whence it is carried back to the smelting-furnace. The level of the lead is in this way gradually reduced if not kept up to a certain height; this is done by casting in melted lead, which is always ready melted in an iron pot. This process is carried on until a certain quantity of

FIG. 4.

H

lead has been concentrated so far that a little more than one weight of lead is combined with an equal weight of silver; this rich lead is taken out and refined in a properly prepared cupel. If sufficient rich lead is ready to make from 500 to 1000 ounces of silver, it is refined in a new cupel, and the silver melted into a cake. The operation is carried on as before, with the only difference that no fresh lead is added.

FIG. 5.

The Washington mine has more recently introduced the German refining furnace represented in fig 5with what success we are not aware. This furnace is larger than the above English furnace, the cupel being at least 6 feet diameter. The drawing shows a section of the furnace, in which the

fireplace y, the tuyeres n n, and the door q, into which the

lead is charged, are shown. In fig. 6 is a ground plan of the furnace shown. Here is the flue x visible, which leads to the stack, and which serves in the mean time to clear off from the

FIG. 6.

surface of the melted lead some of the scum. The cupel of this furnace is made entirely of wood-ashes, which are the refuse ashes from the soap-works, and in this c respect the furnace has an advantage over the English furnace. The floor or hollow surface of it is well pounded by wooden mallets, to make it solid and smooth. About four tons of lead

are charged for one heat; it is carefully laid upon the bottom, and at first gently heated, so as not to injure the fresh bottom, and dome. When the lead is melted, and all ebullition ceases, the blast is thrown in at the tuyeres n n by setting the bellows at playing on the surface of the melted metal. At first no litharge is made, but a dirty froth of oxidized metals is raked off, to facilitate which formation of froth, fine charcoal dust is thrown on the surface. When all the impurities of the lead are removed in this way, the formation of litharge begins, which flows off at the flue

X.

The separation of the litharge from the lead must be assisted by a hook, because the blast is generally not strong enough to move the fluid oxide of lead over the large surface of the molten mass. The cupellation of four tons of metal lasts from 18 to 20 hours. Toward the end of the operation some silver is carried off with the litharge, which portion of litharge is therefore carefully preserved, to be re-melted by itself or along with other ore. The silver is, in this operation, obtained pure in the first heat; it is melted into the form of a cake in a cavity prepared for its reception in the centre of the hearth.

In all these refining operations there is an inevitable loss of metal, disappearing in the form of fumes, through the chimney. This loss is variable, and may be modified by the skill of the workman and the purity of the lead; it amounts on an average to from 4 to 7 per cent. of the lead melted.

Leaving out of consideration the product of silver in distinction from that of gold, we resume the consideration of the latter. The gold mines have been extensively worked in these States, particularly in North Carolina and Virginia. Some years a large number of persons have been engaged in the operations.

The following is an estimate of the product of the gold region