Volume 11 (1865) (424 pages)

194 She Mining and Scientific Dress. Gomaninications. Jn ruis Department we invite Ihe FREE Discussion of all pooner anbjecta—correspondents alone being responsible fur ideas and ihenries they advance. [Written for lhe Mining and Sclentlfic Press.) Copper Mines and Reduction of Copper Ores. Ths rednetion of eopper ores has agitated ths miods of many lenrned men and capitalists in California—the former to briog their knowledge, the latter their copital to a beneficial account. The value of our copper interests is kuowo to but a very few in the eom-. munity. In looking through tbe country we find that nearly or quite every couuty iu this State and Nevada bas:mors or less well defined lodes, and it would be superfluous to describe their locations, formations, etc., as this has been done over and again. ‘That the mines and ores are here, and in abundaoce, is also an established fact; but tbe great question to be solved, is WUAT TO LO WITH THE ORE. J have almost daily opportunities to be shown and to have an assay made of ores from newly discovered mines, and am contineally asked whnt I consider a mins is worth with teu to twelve per cent ore, or in other words, if they are worth auything at all? Those are questions generally not very easily answered, as the value of 2 mine depends principally on the distance the ore bas to be trausported to a shipping port, and other local facilities; and until we have in California all the means at command to reduce our own ores, we shall have to be conteut with shipping abroad. At least this must be the case so long the smelters abroad give n3 n reasonable price for the ore; but if tbey shonld continue for a while longer to depreciate the value of our ores, as they have been doing of late, we shall be compelled to work them here; for it wont pay to ship at prices much reduced from preseut rates. Several efforts have been made in California to smelt the low grade ores; but the undertakings have not, as yet, been very profitable for various reasons, which J will hereafter explain. Mivers are at present just as much in doubt as to the value of their mines as when they discovered them ; everybody wnnts to find a solid lode of sulpbnrets, carbouates, or oxyds, and if they do not find at least twenty per cent. ore their mines nre considered worthless. I know of many mioes which contniv well’ defined and good lodes, averaging from six to twelve per cent., and the ore not worth working ; as ooe of that grade canuot be taken out and transported to Swansen or Boston, so as to lenve a profit to the miue. The question very naturally arises: What shall be done with such mines—are they worth anytbing or not? I have carefolly read the articles published on this swhject in your paper, some time ago, and writteu by a learned Professor. He gave us an elaborate description of copper sineltiog, by means of charcoal. Tho notes giveu by tbe Professor are of much practical value ; but in some points I think he is iu error. He says the cheapest mode of extracting the copper from ores is by smelting, aid then goes on aud gives us all the expenses connected with reduction and refining, and lastly sys concentration by water wont pay. He says he has calculated the costs of concentration, and the figures satisfy him that it willnot pay. If the Professor had given us the figures we might he better able to judge ol the correctness of his calculations. ‘This is the first point in which I ditier from the learned gentleman. I am not a Protessor or Doctor, I am only a learver, although I believe I have sufficient knowledge to rednce copper ore by snielting as wells by balf a dozen otlier processes ; and I know also by practient experience thut copper ores here, as wellas in other countries, fe be eonceutrated cheaper by water than by re. Tt the Professor has seen what they call the dressing floors in England and Vornwall, or the dressiug works in Germany and Australia, he must surely be conviuced that it does not cost as inuch to crush and concentrate a ton of orc, us it does to smelt it; and that, too, where cval is only wortb $1 per ton. At least two-thirds of all the ore smelted iv Evgland and Germany, is first coneevtrated by wnter and then smelted, aod I believe that the people in Europe study their business quite as elose as they do here, and they have the advantage of n thousand years. of experience. But all this wont satisfy our miuers ; they want sineltiug works as the first operation, and if I tell them, a hundred tines, don't smelt as long us you can eoncentrate your ore by water, or sell it for from two to three dollars per unit, they won't listen to me; they think they know better,aod go on and build their smelting works. I have several times declined to build smelting works whe I have beeu asked to do so, and refused guod pay, because 1 kuew it would be too expensive; and when I have recommended concentrstion by water they would not listen to me, until by dear bought experience they have learued a lessou. We bave now several smelting works in California ; ask the proprietors what they have dooe and what their profits are, and if they are candid, they will tell you they have lost money. Smelting is a very easy work ; but it ig not so easily accomplished as it is tu melt a bar of lead or silver. “Phe operator has not only to get out 2 certain quantity of metal, but tle value of that depeuds on the quality of the copper, whicb cau be greatly improved by an experienced smelter. 1 have seen regulus smelted here in California not much over thirty per cent., tbe ore of which was yellow j, sulphurets that hnd been concentrnted, at one fourth the cost of sineltiug, to a twenty-five per cevt. ore. Many miners have but little knowledge of what is ineant by coucentration by fire or water, and to those who are not ncquaiuted with metallurgical processes, I simply say : concentration by water meaus notlhiiug more or less than to separate the metal from the gaogue or matrix, and get the metal as much as possible concentrat-d withthe least possible loss. In England this is chietly done by hand labor ; in Germany it is dooe by machinery, and this latter method will have to be adopted by our miners as hand labor is high, and power in most of the mines cheap. It would take too much room in your paper to deseribe the many nnd very ingenious machines whicb have of late years been iuvented and introduced in Germany, by the application of which machines, ore can be concentrated for six or ten cents per cubic foot. The only effort of the kind made in California, was at the Keystone mine, in Copperopolis, aud these works were imperfect in every way. I told the Superintendent then, a year ago, that the rst principle of concentration had heen overlooked. ‘The ore should be properly classified first, and then he vould be nble to concentrate or separate by specific gravity. I did not see a single machine there for which I would give ove dollar, if I had to nse them; but nevertheless, several thousand dollars have been spent to no purpose, and as any ove ac-! quaiuted with such machinery could have foreseen, it did not pay, nnd IJ had to hear repeutedly that the Keystone tried coveentratiou aud it proved of no account. But Tam sure if the Keystone take their eight per cent. ore, concentrate by proper machinery and let the Union mine go on sinelting their eight per cent. ore, that at the end of the year the Key.stoue will be ahead fifty per cent.in profits over the Uniou. In conelusion, I have only to say that I covsider a mine witb a good jode and eight per ceut. ore, in a convenient location, a valuable property. J. Mosueimer, Eogineer and Metallurgist. [Wrillen for the Mining and Scientific Press.] The Mount Diablo Goal Mines. Epitors Mrixinc anp Scientiric Press :— California not only possesses her mines of untold wealth in the precious metals, whieh havo attracted hither the inhabitants of every clime, and made her name memorable as the great gold-produciug field of the world; but the experience of the past five years‘has also demonstrated that she holds imbedded within her hills, and within a few miles of navigable waters, immense avd iuexhaustible fields of coal, the production of which has already tended to lesseu the importation of ofthat article to the extent of thousands of tons yearly, and which is daily increasing. For four years the California Steam Navigation Company have used the Mt. Diablo coal ; the same may be said of all the ferries and steamers plying on the Bay, as well as ninetentbs of the stationary engines in this city. It is now exclusively employed for making steani at the sugar refineries, distilleries, woolen’ mills, four mills, nnd in all the foundries; it being considered cheaper for such use than any other coal which can be obtaiued in San Francisco. Thsre nre now in successful operation four mines—tbe Black Diamond, Eureka, aud tbe Manhattan—which can supply ten thousand tons per mouth. Of these, the two first named are ths most valuable and extensive. The mines are loeated in the foot hills of Mt. Diablo, and distant about five miles from New. York, the embareadaro, which is situated ot ths mouth of the San Joaquin river. ‘I'be Black Diamond mioe lies,nbout a mile west of Somerville, and is separated fiom thoss of that plece by a higb intervening hill. The company was incorporated in June, 1861, and has heen steadily eniployed since. For, the past four years, Mr. Benjamin Joues has had the man-. agement of the works; and the manoer in which he hns discharged his duty reflects great credit upon him as n skillful miuer and competent superintendent. ‘Ihe coal lands owned by this company comprise soms 600 acres, all of which is hilly and hroken nod unfit for cultivation, but nffording good pasturage. A survey lias alrendy been made fora railroad which is in contemplation, and ere anotber year rolls round, it is expected that the iron horse will be transporting his hundred tons per load to the landing. ‘The distanee from the mine to the depot on the river, is five and two-fifths ‘miles, with a maximum grade of 255 feet, aud au average of 144. Thc entire cost for a good substautial road, is estimated at $85,000. The engineer, in his report, says: “I have exaniined the coal tuunels and coal, and am satisfied that wben a system of transportation is completed, you can calculate upon hauling five hundred tons daily.” At present about 125 tons are being mined, which affords direct einploymeut to about one hundred mivers ond laborers, besides those engaged in hnuling to the landiug and boating it to San Francisco. Litigation with the California Mining Company, incorporated by Pioche & Bayerque, has tended to impede the speedy completion of the railroad, which is the only thing necessary to make this one of the most valuable nnd extensive coal mines on ths Pacifie coast, as the extent of coal lauds owned by the company, together with the natural facilities for working the vein will show at aniomentary glance. The company have two miues now in successful operntion, eacl working separate veins; ove known as the Clork vein, and the other that of the Black Diamond. In order to strike the Black Diamond vein. n tunnel hnd to be run through sand rock for a distanee of 430 feet, when a vein of pure coal four feet thick wns reached. The veiu dips from south to north at an angle of 36°. In order to expedite the workiog, two openings were made, one by driving a slope down on the dip of the vein 140 feet before opening the chambers ; and the other by continuing the gangway running with tlie coal, and which has penetrated to the great distance of 2.150 feet—1,720 beiog run with the coal and mined as the gungway advauces. As very few of the consumers of the product of the hardy collier can forin any idea as to the manner in which it is obtained, a description of the working of the vein may not here be out of place. The miver conmences by driving a drift, called a “chute,” which is from three to four leet wide, and the depth of the vein for a distance of sixteen feet, which is to lenve n substantial pillar between the chamber and gangway, to preveut caving : a chamber, or in iiner’s parlance, breast, is then opened, which is about seven yards wide, and is driven parallel with the zangway. A second chute is then continued iv a straight line with the first, nnd driven a distance of ten feet, when the second breast is opened, which runs parallel with the first, and so on, continuing to leave pillars ten leet thiek between ench, so as to have a uuiTormity of work. ‘hese pillars are easily mined, as the immense weight tends to crush them; aud on the abandonment of the mine they are taken out, so that no coal is lost. Heavy timbers have to be used in the gaogway, to prevent caving, nid posts nre required to be set in the breasts every few feet apart to support the superincumbent weiglit, nfter removing the coal. Great care is taken in this work, as it is all important that no cave should occur in the breasts after being worked out, which would prevent the lree passage of air througb them, aud allow the accumulation of black or choke damp, which is poisonous to the lungs, and which would soon drive all the workmen Irom the mine. In ordor to get the coal from the breasts after being mined, sbeets of thin iron three feet wide by nbout twelve long, are laid in the bottom of the chutes and through the breasts, aud the dip being sulficiently steep, the coal, by its own weight, will go to the bottom, when it is then run iuto the ears, which hold aboot three-quarters ol a top each, and then drawov out of the tunnel bya horse, three cars at a tine. Alter being ruo through the sereens, and the dust and pen coal separated, it is then ready for market. A wooden track cavered with iron is laid in the tunuel for the cars toron upon. Coal is mined by the yard, and the only tools used by the ininer, is the drilt-pick, gnd or iron wedge,and . sledge-hammier. A cut is commenced, which is done by undermining the bottom coal ahout three feet nnder, and not more than six inches . rhigh, so as not to chip up any more coal than . is necessary, when each end of the coal under . niined is then cut loose from the walls of the vein, and tlie gad driven inté the svain, which is uhout the middle of the vein, and a mass of coul seven feet long and two thick, comes tumbling under the heavy stroke of the ham. jner. Grent caution must be exercised to keep ‘clear of the falling coal. ‘he gad is then driven in between the roof and remaining seam — of coal, which is more easily detached than . the lower mass. The coal is then broken up in sinaller pieces and throwu into the chutes, ‘he miners have to work in a sitting posture, ! . i ' i the thickness of the vein. ‘Two of the great impediments to mining, are water and the acenmulation of foul air; the one is obviated by siukivg air-shafts from ths surface to iotercept the vein, and cause drafts of nir to pass through all the breasts, removing the foul air, black damp and smoke from the miners’ lamps. While it is necessary to” have steam engines at inavy if not all the . neighboring nines, to keep thein free from water, a labor which costs thousands of dollars during the year, the water from this inine ig Kept free by one man working a foreepump. The coal from the Black Diamond vein, is of a bright black color, iueh resembling ths Liverpool coal, and hasa niuch greater density than that ol the Clark vein, which is the only one yet worked by tbe Union. Eurekn and Pittsburg. The Manhattan, alter the great cost of running a tunnel 1,050 feet through sand-rock, reached the Black Diamond veio, bet at a point where it was not of sufficient . thickness to justify working. This coal, lor j household purposes, will, soouer or later, taks the place of lureign coals. The Block Diamond vein is about 300 feet below that known as tho Clark vein, which ig about three andn half feet in thickness, and i dips from south to north nt an angle of 32%, Mr. Jooes, in opening this mine, drove down a : slope so us tu intercept the pitch of the vein, and reached the coal io 147 feet, the slopa having uearly the same dip ag the.vein; a yangway was then run north and south of ths slope, so as to enable them to take coal from both ways, ‘These tunvels lave reached a dis+) tance, one 120 aud the other 320 feet from ths mouth of the slope. The coal is put in cats,run out on the rail track to the slope by man . power, then hitched to a heavy rope and drawn to the top by a horse aud whim. About forty _ tous a day are now being taken from this miue, but the tncilities are such that, with an io-: creased workiug force, 250 tous could be mined daily. . If Mt. Diablo has hitherto failed to produce mines rich in precious metals, she has neverthele s establisbed a reputation of having ths great coal producing basin of the State, aod we hope the day is not far distant when our people will see the folly of importing an orticle which she has in inexhaustible quantities in her own native hills, and which can be prodiced at one-half the cost of that iniported. By producing a home supply thousands of dollars, sent out of the State to pay for foreign and Eastern coals, will then be saved, and anotber drain upon our treasury closed. As yet the coal inines have done but little to advance the pecuniary interests ol the owners, the price Tor which it is sold being but little aboys the cost of production ; but to the State, largs benefits have accrued. Several towns have sprung into existence, a railroad in course of construetion, another in preparation, to say nothing of the direct employment afforded to several hundred men, by which they uot only Make a coinfortable living, but fair wages be: sides. A large number of teains are required to hanl the coai from the mine to the river, where a number ol schooners find steady em-. ployment at fair profit in taking it to the city, its final point of destination ; and all this is . the result of the coal discovery in Mt. Diablo, which is not known probably to one half ths coal consumers in San Francisco. A. B. ~ Patent Sarery Can.—Messrs. Perkins and House have invented a con that will protect benzine or any other fluid from the danger of explosion. The principle ou which this eau operntes is similar to that invented by Sir Humphrey Davy, and applied to his celebrated salety lamp. Tur creation by the President of a Bureat: of Pardons, witb au able and fair man at 1f6 head, has been recommended, and is now un-! . der consideration by him. . as the ceiliug is only abont four feet high, being

194 She Mining and Scientific Dress. Gomaninications. Jn ruis Department we invite Ihe FREE Discussion of all pooner anbjecta—correspondents alone being responsible fur ideas and ihenries they advance. [Written for lhe Mining and Sclentlfic Press.) Copper Mines and Reduction of Copper Ores. Ths rednetion of eopper ores has agitated ths miods of many lenrned men and capitalists in California—the former to briog their knowledge, the latter their copital to a beneficial account. The value of our copper interests is kuowo to but a very few in the eom-. munity. In looking through tbe country we find that nearly or quite every couuty iu this State and Nevada bas:mors or less well defined lodes, and it would be superfluous to describe their locations, formations, etc., as this has been done over and again. ‘That the mines and ores are here, and in abundaoce, is also an established fact; but tbe great question to be solved, is WUAT TO LO WITH THE ORE. J have almost daily opportunities to be shown and to have an assay made of ores from newly discovered mines, and am contineally asked whnt I consider a mins is worth with teu to twelve per cent ore, or in other words, if they are worth auything at all? Those are questions generally not very easily answered, as the value of 2 mine depends principally on the distance the ore bas to be trausported to a shipping port, and other local facilities; and until we have in California all the means at command to reduce our own ores, we shall have to be conteut with shipping abroad. At least this must be the case so long the smelters abroad give n3 n reasonable price for the ore; but if tbey shonld continue for a while longer to depreciate the value of our ores, as they have been doing of late, we shall be compelled to work them here; for it wont pay to ship at prices much reduced from preseut rates. Several efforts have been made in California to smelt the low grade ores; but the undertakings have not, as yet, been very profitable for various reasons, which J will hereafter explain. Mivers are at present just as much in doubt as to the value of their mines as when they discovered them ; everybody wnnts to find a solid lode of sulpbnrets, carbouates, or oxyds, and if they do not find at least twenty per cent. ore their mines nre considered worthless. I know of many mioes which contniv well’ defined and good lodes, averaging from six to twelve per cent., and the ore not worth working ; as ooe of that grade canuot be taken out and transported to Swansen or Boston, so as to lenve a profit to the miue. The question very naturally arises: What shall be done with such mines—are they worth anytbing or not? I have carefolly read the articles published on this swhject in your paper, some time ago, and writteu by a learned Professor. He gave us an elaborate description of copper sineltiog, by means of charcoal. Tho notes giveu by tbe Professor are of much practical value ; but in some points I think he is iu error. He says the cheapest mode of extracting the copper from ores is by smelting, aid then goes on aud gives us all the expenses connected with reduction and refining, and lastly sys concentration by water wont pay. He says he has calculated the costs of concentration, and the figures satisfy him that it willnot pay. If the Professor had given us the figures we might he better able to judge ol the correctness of his calculations. ‘This is the first point in which I ditier from the learned gentleman. I am not a Protessor or Doctor, I am only a learver, although I believe I have sufficient knowledge to rednce copper ore by snielting as wells by balf a dozen otlier processes ; and I know also by practient experience thut copper ores here, as wellas in other countries, fe be eonceutrated cheaper by water than by re. Tt the Professor has seen what they call the dressing floors in England and Vornwall, or the dressiug works in Germany and Australia, he must surely be conviuced that it does not cost as inuch to crush and concentrate a ton of orc, us it does to smelt it; and that, too, where cval is only wortb $1 per ton. At least two-thirds of all the ore smelted iv Evgland and Germany, is first coneevtrated by wnter and then smelted, aod I believe that the people in Europe study their business quite as elose as they do here, and they have the advantage of n thousand years. of experience. But all this wont satisfy our miuers ; they want sineltiug works as the first operation, and if I tell them, a hundred tines, don't smelt as long us you can eoncentrate your ore by water, or sell it for from two to three dollars per unit, they won't listen to me; they think they know better,aod go on and build their smelting works. I have several times declined to build smelting works whe I have beeu asked to do so, and refused guod pay, because 1 kuew it would be too expensive; and when I have recommended concentrstion by water they would not listen to me, until by dear bought experience they have learued a lessou. We bave now several smelting works in California ; ask the proprietors what they have dooe and what their profits are, and if they are candid, they will tell you they have lost money. Smelting is a very easy work ; but it ig not so easily accomplished as it is tu melt a bar of lead or silver. “Phe operator has not only to get out 2 certain quantity of metal, but tle value of that depeuds on the quality of the copper, whicb cau be greatly improved by an experienced smelter. 1 have seen regulus smelted here in California not much over thirty per cent., tbe ore of which was yellow j, sulphurets that hnd been concentrnted, at one fourth the cost of sineltiug, to a twenty-five per cevt. ore. Many miners have but little knowledge of what is ineant by coucentration by fire or water, and to those who are not ncquaiuted with metallurgical processes, I simply say : concentration by water meaus notlhiiug more or less than to separate the metal from the gaogue or matrix, and get the metal as much as possible concentrat-d withthe least possible loss. In England this is chietly done by hand labor ; in Germany it is dooe by machinery, and this latter method will have to be adopted by our miners as hand labor is high, and power in most of the mines cheap. It would take too much room in your paper to deseribe the many nnd very ingenious machines whicb have of late years been iuvented and introduced in Germany, by the application of which machines, ore can be concentrated for six or ten cents per cubic foot. The only effort of the kind made in California, was at the Keystone mine, in Copperopolis, aud these works were imperfect in every way. I told the Superintendent then, a year ago, that the rst principle of concentration had heen overlooked. ‘The ore should be properly classified first, and then he vould be nble to concentrate or separate by specific gravity. I did not see a single machine there for which I would give ove dollar, if I had to nse them; but nevertheless, several thousand dollars have been spent to no purpose, and as any ove ac-! quaiuted with such machinery could have foreseen, it did not pay, nnd IJ had to hear repeutedly that the Keystone tried coveentratiou aud it proved of no account. But Tam sure if the Keystone take their eight per cent. ore, concentrate by proper machinery and let the Union mine go on sinelting their eight per cent. ore, that at the end of the year the Key.stoue will be ahead fifty per cent.in profits over the Uniou. In conelusion, I have only to say that I covsider a mine witb a good jode and eight per ceut. ore, in a convenient location, a valuable property. J. Mosueimer, Eogineer and Metallurgist. [Wrillen for the Mining and Scientific Press.] The Mount Diablo Goal Mines. Epitors Mrixinc anp Scientiric Press :— California not only possesses her mines of untold wealth in the precious metals, whieh havo attracted hither the inhabitants of every clime, and made her name memorable as the great gold-produciug field of the world; but the experience of the past five years‘has also demonstrated that she holds imbedded within her hills, and within a few miles of navigable waters, immense avd iuexhaustible fields of coal, the production of which has already tended to lesseu the importation of ofthat article to the extent of thousands of tons yearly, and which is daily increasing. For four years the California Steam Navigation Company have used the Mt. Diablo coal ; the same may be said of all the ferries and steamers plying on the Bay, as well as ninetentbs of the stationary engines in this city. It is now exclusively employed for making steani at the sugar refineries, distilleries, woolen’ mills, four mills, nnd in all the foundries; it being considered cheaper for such use than any other coal which can be obtaiued in San Francisco. Thsre nre now in successful operation four mines—tbe Black Diamond, Eureka, aud tbe Manhattan—which can supply ten thousand tons per mouth. Of these, the two first named are ths most valuable and extensive. The mines are loeated in the foot hills of Mt. Diablo, and distant about five miles from New. York, the embareadaro, which is situated ot ths mouth of the San Joaquin river. ‘I'be Black Diamond mioe lies,nbout a mile west of Somerville, and is separated fiom thoss of that plece by a higb intervening hill. The company was incorporated in June, 1861, and has heen steadily eniployed since. For, the past four years, Mr. Benjamin Joues has had the man-.

agement of the works; and the manoer in which he hns discharged his duty reflects great credit upon him as n skillful miuer and competent superintendent. ‘Ihe coal lands owned by this company comprise soms 600 acres, all of which is hilly and hroken nod unfit for cultivation, but nffording good pasturage. A survey lias alrendy been made fora railroad which is in contemplation, and ere anotber year rolls round, it is expected that the iron horse will be transporting his hundred tons per load to the landing. ‘The distanee from the mine to the depot on the river, is five and two-fifths ‘miles, with a maximum grade of 255 feet, aud au average of 144. Thc entire cost for a good substautial road, is estimated at $85,000. The engineer, in his report, says: “I have exaniined the coal tuunels and coal, and am satisfied that wben a system of transportation is completed, you can calculate upon hauling five hundred tons daily.” At present about 125 tons are being mined, which affords direct einploymeut to about one hundred mivers ond laborers, besides those engaged in hnuling to the landiug and boating it to San Francisco. Litigation with the California Mining Company, incorporated by Pioche & Bayerque, has tended to impede the speedy completion of the railroad, which is the only thing necessary to make this one of the most valuable nnd extensive coal mines on ths Pacifie coast, as the extent of coal lauds owned by the company, together with the natural facilities for working the vein will show at aniomentary glance. The company have two miues now in successful operntion, eacl working separate veins; ove known as the Clork vein, and the other that of the Black Diamond. In order to strike the Black Diamond vein. n tunnel hnd to be run through sand rock for a distanee of 430 feet, when a vein of pure coal four feet thick wns reached. The veiu dips from south to north at an angle of 36°. In order to expedite the workiog, two openings were made, one by driving a slope down on the dip of the vein 140 feet before opening the chambers ; and the other by continuing the gangway running with tlie coal, and which has penetrated to the great distance of 2.150 feet—1,720 beiog run with the coal and mined as the gungway advauces. As very few of the consumers of the product of the hardy collier can forin any idea as to the manner in which it is obtained, a description of the working of the vein may not here be out of place. The miver conmences by driving a drift, called a “chute,” which is from three to four leet wide, and the depth of the vein for a distance of sixteen feet, which is to lenve n substantial pillar between the chamber and gangway, to preveut caving : a chamber, or in iiner’s parlance, breast, is then opened, which is about seven yards wide, and is driven parallel with the zangway. A second chute is then continued iv a straight line with the first, nnd driven a distance of ten feet, when the second breast is opened, which runs parallel with the first, and so on, continuing to leave pillars ten leet thiek between ench, so as to have a uuiTormity of work. ‘hese pillars are easily mined, as the immense weight tends to crush them; aud on the abandonment of the mine they are taken out, so that no coal is lost. Heavy timbers have to be used in the gaogway, to prevent caving, nid posts nre required to be set in the breasts every few feet apart to support the superincumbent weiglit, nfter removing the coal. Great care is taken in this work, as it is all important that no cave should occur in the breasts after being worked out, which would prevent the lree passage of air througb them, aud allow the accumulation of black or choke damp, which is poisonous to the lungs, and which would soon drive all the workmen Irom the mine. In ordor to get the coal from the breasts after being mined, sbeets of thin iron three feet wide by nbout twelve long, are laid in the bottom of the chutes and through the breasts, aud the dip being sulficiently steep, the coal, by its own weight, will go to the bottom, when it is then run iuto the ears, which hold aboot three-quarters ol a top each, and then drawov out of the tunnel bya horse, three cars at a tine. Alter being ruo through the sereens, and the dust and pen coal separated, it is then ready for market. A wooden track cavered with iron is laid in the tunuel for the cars toron upon. Coal is mined by the yard, and the only tools used by the ininer, is the drilt-pick, gnd or iron wedge,and . sledge-hammier. A cut is commenced, which is done by undermining the bottom coal ahout three feet nnder, and not more than six inches . rhigh, so as not to chip up any more coal than . is necessary, when each end of the coal under . niined is then cut loose from the walls of the vein, and tlie gad driven inté the svain, which is uhout the middle of the vein, and a mass of coul seven feet long and two thick, comes tumbling under the heavy stroke of the ham. jner. Grent caution must be exercised to keep ‘clear of the falling coal. ‘he gad is then driven in between the roof and remaining seam — of coal, which is more easily detached than . the lower mass. The coal is then broken up in sinaller pieces and throwu into the chutes, ‘he miners have to work in a sitting posture, ! . i ' i the thickness of the vein. ‘Two of the great impediments to mining, are water and the acenmulation of foul air; the one is obviated by siukivg air-shafts from ths surface to iotercept the vein, and cause drafts of nir to pass through all the breasts, removing the foul air, black damp and smoke from the miners’ lamps. While it is necessary to” have steam engines at inavy if not all the . neighboring nines, to keep thein free from water, a labor which costs thousands of dollars during the year, the water from this inine ig Kept free by one man working a foreepump. The coal from the Black Diamond vein, is of a bright black color, iueh resembling ths Liverpool coal, and hasa niuch greater density than that ol the Clark vein, which is the only one yet worked by tbe Union. Eurekn and Pittsburg. The Manhattan, alter the great cost of running a tunnel 1,050 feet through sand-rock, reached the Black Diamond veio, bet at a point where it was not of sufficient . thickness to justify working. This coal, lor j household purposes, will, soouer or later, taks the place of lureign coals. The Block Diamond vein is about 300 feet below that known as tho Clark vein, which ig about three andn half feet in thickness, and i dips from south to north nt an angle of 32%, Mr. Jooes, in opening this mine, drove down a : slope so us tu intercept the pitch of the vein, and reached the coal io 147 feet, the slopa having uearly the same dip ag the.vein; a yangway was then run north and south of ths slope, so as to enable them to take coal from both ways, ‘These tunvels lave reached a dis+) tance, one 120 aud the other 320 feet from ths mouth of the slope. The coal is put in cats,run out on the rail track to the slope by man . power, then hitched to a heavy rope and drawn to the top by a horse aud whim. About forty _ tous a day are now being taken from this miue, but the tncilities are such that, with an io-: creased workiug force, 250 tous could be mined daily. . If Mt. Diablo has hitherto failed to produce mines rich in precious metals, she has neverthele s establisbed a reputation of having ths great coal producing basin of the State, aod we hope the day is not far distant when our people will see the folly of importing an orticle which she has in inexhaustible quantities in her own native hills, and which can be prodiced at one-half the cost of that iniported. By producing a home supply thousands of dollars, sent out of the State to pay for foreign and Eastern coals, will then be saved, and anotber drain upon our treasury closed. As yet the coal inines have done but little to advance the pecuniary interests ol the owners, the price Tor which it is sold being but little aboys the cost of production ; but to the State, largs benefits have accrued. Several towns have sprung into existence, a railroad in course of construetion, another in preparation, to say nothing of the direct employment afforded to several hundred men, by which they uot only Make a coinfortable living, but fair wages be: sides. A large number of teains are required to hanl the coai from the mine to the river, where a number ol schooners find steady em-. ployment at fair profit in taking it to the city, its final point of destination ; and all this is . the result of the coal discovery in Mt. Diablo, which is not known probably to one half ths coal consumers in San Francisco. A. B. ~ Patent Sarery Can.—Messrs. Perkins and House have invented a con that will protect benzine or any other fluid from the danger of explosion. The principle ou which this eau operntes is similar to that invented by Sir Humphrey Davy, and applied to his celebrated salety lamp. Tur creation by the President of a Bureat: of Pardons, witb au able and fair man at 1f6 head, has been recommended, and is now un-! . der consideration by him. . as the ceiliug is only abont four feet high, being