Volume 29 (1874) (428 pages)

194 MINING AND SCIENTIFIC PRESS. [September 26, 1874. Refining Base Bullion. A correspondent of the Eureka Sentinel gives the following description of his visit to tbe Germania Refining Works, situeted about six milee south of the Salt Lake city, on the Utah southern railroed. The main objéct’ of. these works is the separation of the precious metels from the leed in the so-celled base bullicn, by means of zinc, or, technically speeking, the desilverization of lead by zinc. As it may not be nninteresting to a large number of yout reeders to get an idea of the exeention of this rocess, I willin tbe following try to give a Brief description of the menipnlations carried on atthe works above mentioned. Previously it will be necessary, however, to make a few general remerks. Tho zine desilverization precesa.is based upon the following facts: = 1. Zinc has a greeter affinity for silver and gold than lead. 2. It does not form an alloy with lead. 8, It has a lesser specific gravitythan lead. * 4, The melting point of zine is et 412°C., while that of Jeed is et 334°. If metallic zinc is added to molten base bnilion at a temperature higher than the melting point of the former, the zinc forms an alloy with the gold and silver of the lead bullion, and, in cooling down, rises to the: snrface of the now impoverished lead, which must be kept in a state of fusion, covering the whole of the lead in the shepe of a hard scum—the zine senm. ‘This scnm is teken off from the leedbath, and’as it still contains a large percentage of lead, is subjeoted to:a liquetion process, by which the lead is sweated out to within about 21% per cent. Thé zine scum from this operation is the silver producsr; the reméining lead being zinciferous, must be softened, end is then ready. for,the market. From the above, it would appear thet the zine process is composed . of three main operations: : + 1. The desilverization of the lead bullion. 2. The dezincifioation of the poor lead. 3, The desilverization of the zine scum. Desilverization of the Lead Bullion. After the bullion is sampled and assayed, from 20 to 22 tons are introduced into a large calcining furnace, the bottom of which is encased by e strong cast-iron box. Here the bulliou is melted and then subjected to a dull red heat, air being admitted through the work-doors, whereby most of the mecbanical impuritiss, consisting of iron and coppsr mette, and a portion of the antimony, arsenic ‘and copper, in the shape of their oxides, are bronght to the surfece of the metal, in cnseqnence of their lesser specific gravity. These impurities are known nnder the name of dross, As soon es the surface of the metal is completely covered with dross, this is skimmed off and removed throgh ithe work-doors. It still contains precious metels. Wewill call it ‘‘first dross.’’ The lead bullion in this celciner is then tapped, end, by means of an iron spout, conveyed into either one of the two largest of a system of five cast-iron desilverizing pots. These pots, or kettles, are set in the shape of a wedge, the two lergest ones forming its basis, the smallest one the point. As the works are rnnning at helf capacity at present, that is, 20 tons of bullion per 24 honrs, only one series of pots is in use, viz: one large one, one middle one end the one at the point. Hech pot has its separate fireplece, which derives its draught, like all the other fnrnaces, from a stack 90 feet in hight. The Lead Bullion In the first potis now exposed to a temperature high enougb to smelt @ certain percentage of zino, which is added ina sort of an iron cege attached to a stirring contrivence. As soon as athe zine is believed to be sufficiently mixed with the bullion the stirring epperatus is withdrewn end the temperatnre ellowed to go down to the melting point of leed. The scum, which now rises to the surfece, is ladled over into the adjoining smaller pot, melted, stirred, and cooled, and skimmed as before, the skimmings being transferred to the last and smallest pot, in which they have to nndergo the.same manipulations. The scum from this last pot is the rich scum and goes to the alloy furnace. The leed from the second and third pots is returned to the first pot by meens of a connecting gutter, ‘into which the lead is ladled. Hereafter a second eud ‘afterward a third addition of «zine is mede in pot No. 1, and the ensuing scums are treated in the samé menner as before, with the sole exception thet’ the final scums are not taken to the alloy furnace, but are nsed over: again instead of metallic zinc, they being too poor‘in precious metals. The liquation lead (lead sweated out) from these laet zine addition, is returned to the firet pot, whereupon the ‘latter is emptied, through a spont atits bottom, into a softening furnace— of which there are'two, one connected with each large pot. Dezincitication of the Poor Lead. The lead from the first pot is now practically desilverized, ae it containe only 15 grammes of eilver, or less than 1-11 of on ounce in the ton; but itie hard, owing to a small percentage of zinc being retained in it, and to the presence of arsenic and antimony, if such have been in the . To remove these impurities the lead is exposed to 2 dull, red heat in the softening furnace, and from time to time stirred with a hoe to offer a new surface to the As soon as the lead is perfectly covered with dross, and the samples teken out of the furnace from.time to time by their peculiar luster.and crystalline texoriginal bullion, oxidizing agency of the air, ture demonstrate its purity, the drogs is removed through the work-doors and the lead is tapped into a large cast-iron pot with fire-place. Here the lead is poled for several hours, thet is, stirred with a pole of green wood, whereby it assumes a bubbling motion and thus gives a large number of surfaces to tbe air. By this ) operation the lest traces of zinc are removed. Through a movable spout at the bottom of tbe pot the lead is run into molds branded “selected’? or “common” lead, according to its purity. The ‘dross is reserved for further working; we will call 1t poor lead dross. Desilverization of the Zinc Scum, The rich zine scum, es I said before, is treated in the alloy furnace. This is a blast furnace of smalier dimensions than the enormous*ore-smelting furneces of Eureka. The scum is sinelted in. conjunction with pieces of Serap-iron and cre-slag, Pennsylvania coke serving as a fuel. The smelting is doneata low temperature under a pressure of blast. By this operation the. zine is, for the most part, 7) volatilized as oxide of zinc, which is caught iu . a condensation chamber atteched to the furnace; but the silver and gold remain with the lead, which was intermingled with tbe zinc scum. This “rich lead’’ is tapped below the furnace-hearth and ladled into molds, aud is tben pussed over to the cupelling furnaces. The slag is not kept running coutinuously, but tapped at intervels, the breast of tbe furnace being closed in the meanwhile. Tbe slag is jused over in the ore-smelting furnaces esa flux. As enother residual product, we heve zincifarous iron-sows, which form a crust around the heerth of the fnrnace and have to be detached ‘by mechanical means. ‘They look very much ‘like’ our speiss or ‘‘iron,” as it is commonly tion of galena. The rich lead is cupelled iu an English Cupelling Or refining furnace, of which thero are six ‘in the works. The bottoms, cupels or tests, of these furnecss are made of bone ashes, and have an oval shape. Before use they are dried and anneeled. Tbey-resf on two strong iron bars in tho farnace proper. Attho back wall of the furnace there is an opening for the blast, which is created by steam, and on each side of it a charge-hole. At tbe front well there is-an sideways from the test there is a fire door. The test is placed in the furnace in such a manner that the plane ofits long axis passes through the center of the tweer-opening and the discharge. The cupelling process is based upon the following circumstances: If en alloy of leat aud and precious metals is fused and then exposed to a enrrent of eir, the entire lead is gredually converted into oxide of or litharge, asit is generally termed, leeving fiually an alloy of the precious metals, The rich lead is now introduced through the cherge-holes in the test, ber by bar, and melted. As soon as the test is filled up to the rim the blest is turned on and the heet kept up at the same time. The Formation of Litharge Begins, which is partially absorbod by the porous test—pertially drawn offinto a gutter cut into the test on the discbarge side. The lithargeis run into pots monnted on wheels, end removed when filled. As soon as the metal bath has decreased sufficiently in size more rich lead is introduced into the cupel, till it is supposed to contain tbe quentity of siiver desired. The blest is continued until the brigbtening of the silver has teken place, when no more litharge is perceptible, and then the operation 1s finished. A hole isnow bored into the bottom of the test, and the refined metal drewn off into melds resting on a movable frame, The silver bars thus obtained sre remelted in bleck lead crucibles, cast into ingot molds, assayed, and cari now be sold to tbe banks. They are then .996 fine. The litharge is acoumulated for furtber treatment. The test is broken np and assorted. The Untarnished Portions Of it are used over again, while the balance goes to the ore smelting furnace for tbe extrection of the metels it contains. It now remains for us to state briefly what is done with the residual products, in which there is still a good deal of money value hidden. Tbe first dross from the calcining furnace is liquideted ina furnace constructed especially for that purpose by Mr. Weise, the superintendent. Itisareverberatory, with two bottoms, one above tbe other. The upper one is composed of grate-bars with narrow slits, and is charged with the dross. -The lower one coneista of composition, and has a eteep pitch toward the tap-hole, in front of which there is a cast-iron receptacle. The temperatnre is now conducted so that the lead trickles out of the dross into the lower hearth, but leaves the balance unfused. ‘This droesis then withdrawn, and smelted for copper-matte, with iron pyrites, which is not further treated on the epot. The lead goes back to the desilverizing pots. , The Poor Lead Dross Is smelted directly with sleg for antimonial or hard lead (type metal) in 1 cupola furnace. This lead commands agood price, The litharge , from, the cupelling furnaces ie revived in a reverberatory furnace; that is, it ia mixed with stone coal, exposed to a melting heat, whereby it is reduced to metallic lead. As the litbarge ie neither very pure nor free from silver, the reeniting lead has to be returned to the desilverizing pots. ‘ ‘. Exclusive of {the furnaces heretofore men: ‘celled, and mey be used in the desulphuriza. tioned, thore are three more furnaces on the ground destined for the reduction of rew ores and by-products. One is an English flowing furnece, for the production of lead bulljon and gray slag (slag rich in lead) from rich gelena ores. Tbe gray slag is turther treated in one of the two remaining cupola or blest furnaces. I herdly need to sey tbet all ores not fit for the reverberatory ere smelted in tho latter with the proper finxes. The Blast Furnaces, One of which is provided with all the modern appliences (water jeckets)receive their blast from a large-sized Sturtevant fen, propelled by a 45-horse-power engine. All the furneces are provided with dust-chambers connected with flues, wbiob run into the main fiue, the latter terminating into a tall stack. The only fuel required at the works is raw stone coul for the reverberatory furnaces, desilverizing pans and the steam-engine, and coke for the blest and assay furnaces, : Finelly, I cennot forbser to praise the urbanity and willingness of the gentlemen in charge to give inform ation—Mr. Billing, the business mianager, end Mr. Weise, the superintendent. Low Grade Ores. The question of the utilization of low grede ores, says the Eureka Sentinel, is one which hes, heretofore, been too generelly overlooked throughout Nevada. In Europe a system of concentration is now and has been for many years in suecessiul operation, end through its means very nearly all crude ore is prepered for the reduction. What little rich material occurs throughout the vein matter is carefully separated by hend; whilst tbe residuum, by far the major portion, is orushed, jiggsd, passed over the shaking table, round buddles and plane tables, "until a working preduct is obtained ready for the final manipulation, generally in the furnaces. It would surprise the majority of our millmen to leern how small a yield in the lead and the precious metels is deemed worthy of-apreparatory treatment. It is not unusual to submit to oonesntration ores which will jassay two to three per cent. of leed, with from five to $15 in silver t» the tou. So perfect, indeed, is the mechanical errangement of many i i 5 opening for the discharge of the litharge, and . of the works thet as high a8 75 stamps may be seen at work and not a single attendant in sight. The batteries are self-feeders; the crushed pulp passes {first into and over a series of obloug boxes, fitted underneath with pyramidshaped bottoms, from whence the sends, sinking euch according to their respective gravities, are projected through a metallio pipe upon a series of continuslly-moving sheking tebles. The very finest slimes are collected in properly proportioned settling tanks, whenco they are taken on tbe buddles to plane tables, The method of universe! application throughout England, France and Germany depends upon the agency of water, carrying along and holding in a temporary suspension the various comminuted particles of dre and gangue. With us, however, water iu sufficient quantity is not always attaineble, and the inventive genius of our people has been taxed to find enotber medium, which shall combine in a more delicete mauner all tbe requisites of quantity, elasticity and ease of applicetion. All these have beeu found in a combination of erushers, rolleis, separating sieves and jets of atmospheric air. The current of air may be regulated so that its wave-like impulses act on the suspended ore particles precisely as the weter in the jiggiug machines; in tact, being a more attenueted medium, it does not offer too harsh @ resistance to the most delicate atom of tbe so-called noble silver ores, and may be equally as well applied to the commonest of the base leed and copper minerals. Already, for several months, one of these ‘‘dry eir concentretors’’ has been in successful operation in Nevada, and we learn that another and larger machine is to be set up in one of our most successful mills. We shell wetch with more than ordinary interest the progress of the experimont, which is, indeed, in the right direction. Here, right in onr midst, there are thousends, not to say millions, of tons of low grade lead ore, which will_essay from five to eight per cent. in lead, and from, say, five to 15 dollars in gold and silver, which are practically wortbless. At best they ere, if of an irony character, only aveileble as flux. Conld they be concentrated, say four or five tons into one, they could be smelted with profit, We commend this snbject to the cereful consideration of our furnaco men, whom we shall endeavor to keep informed as the experiment to which we allude progresees. ManvractvkE oF CHLoRaTe of Porasu.— To manufacture chlorate of potash on a lurge scale, it has been recommended by W. Hunt to adopt the following method: Milk of lime is made to trickle down over bricks, pleced in a tower where it comes in contact with a coutinuous current of chlorine gas. Chlorate of lime is the chief prodnct, and, by treating this with chloride of potassium, chlorate of potash is formed, which can be purified by cryetallization. Narrenrr, a German pbyeicist, by more modern applianoes, eucceeded in obtaining a temperature of 220° below the freezing point of water, and Dr. Kane obeerved a temperature of 76° below it. Jonle, an eminent English physicist, calculated, from the law of the expaneion of gases, that a temperature of 459° degrees below the freezing point of water wonld probably be the absolute, zero. —_ New and Old Towns in California. The mining towns, says the Bulletin, of Calfornia have been ‘‘cremeted’’_onoe, twice, and some of them three timos. The very bones of these towns have besn burned np, And this has happened, genorally, after the resources throngh which they have been built up have been pertially exhausted. Nevada at one time had a population of not less than 15,000; that is, there were this number which were near enongh to depend upon the postoffice in thet town. ‘Three great conflagrations have swept over the town, yet if is to-day just about as much of a place és it would heve been had no fire consnmed it. In the autumn, according to precedent, we expect to got the news of the burning of twoor three mining towns. The buildings are chiefly of wood. ‘There is always e Chinese querter with all the appliances tor touching off e fire suddenly; high winds and materiel exposed to. thé hot sux until it it almost ready for spontaneons combustion, will ordinarily insure a sweeping conflagration, And so it happens that nearly every mining town of eny prominence hes been tried by fire. Mokelumne Hill hes been swept for the sscond or third time. It will be restored again, beceuse its resources are not confined to 2 few wooden houses. The eigbt or ten thousend people who used to he tributery to the ‘‘Hill” are not there now. We shell heve only the 2,500, more or less, who will still cling t6 its fortnnes, and hold, with a good deal of justice, thet it is one of the healthiest and most picturesque towns in the world. After snch a disastrous experience the wonder is that greater precautions are not taken against fire in these mountain towns, Thus, at Mokelumne Hill there is a kind of-lava-rock nearly or quite fire-proof, and yet so soft whan itis uncovered thet it can be cut with an ax, and cen be prooured witbout limit. We do not hear that any of the buildings coustructed of this rock were destroyed. In the vicinity of all tho mining towns there is an abundance of rock within eesy reech which may be had without other expense than thetof healing. The rough stone cottage is cheap end comfortable. There are no earthquakes in the mountains to shake it down, and the fire will not consumeit. If these mountain towns were construoted from thg waste rock everywhere accessible, they would be among the most picturesqne towns in the world. But in respact to combustible material, the mining towns are herdly worse off tban is San Francisco. We have a wooden weter-front, and two-thirds of the area of the city is covered with wooden buildings. We havea better police supervision end a moro efficient fire dspartment. These are dboutall we have toreduce the contingencies of a sweeping conflagration. An artisan has recently shown the practicability of inclosing ell wooden houses in cities with a brick sbell. He demoustrates thatitcan be done at comparatively small expense, thet the value of houses so treated is grsatly enhanced, and that all objections to wooden houses would be thereby avoided. Tbe brick shell would sustain only its own weight, and there wonld be little reel denger from earthqnakes. These double houses may yet come into favor, but we are not ready for them yet. At preasnt, wooden housss are popular, aud the more so as they admit of much cheap and meretricious oruamentation. New mining discoveries will create new mining towns, and these will follow the fortunes of the mines toalarge extent. But the most promising new towns will spring up along the coest. A considereble town will resnlt from the colony settlement of tbe Lompo ranch, just north of Point Conception; Monterey will be recuscitated, partly through the influsnce of a locel railroad, and the development of agricultural wealth. Santa Berbare has grown from a Mexican hamlet to its present dimensions within the last eight years; and San Diego, with & fine harbor iu front, end a paper reilroad in the rear, hes done wonders. It is now evident that there will be a chain of flonrishing towns along the coast, built up largely throngh agriculture end local commerce. These will never go beckward, beceuse the chief elements of prosperity are not likely to fail. In early times there were towns laid ont, like ‘‘ New York of the Pacific,” which never came to anything. They were sterted without resources and es @ crazy speculation. They never pregressed far enough to furnish a respectable rnin. But the new coast towns, deriving their life from populetion and bnsiness, will be both permenent and prosporous. There is room for at least 20such towns. Many of them may be swept by fire as the mountain towns have been. Bnt the white wooden towne by the sea will be likely to hold on their way until the bottom falls out of agrioulture and commeree—which will certaiuly not be in our time. Frenow Ratuwaxy Cazs,—Some of the double deck cars, which are quite common upon French roads, exhibit an almost extraordinarily emell proportion of dead weight. One on exhibition at Vienna, with a capacity of 90 persons, weighed only 11.75 tons. Freight oars weighing but 10,000 pounds carry 20,000 or even as much as 30,000 pounds. * «om & at nvab ted Lap For Ponisuino.—I, dare aay many will at once say ‘‘ Itwon’t do,” but for many purposes ‘Ho emery glued oh anything, or made np in any way, is so simple and effecinal asa plain piece of hardwood tured to the shape reqnired, and smeared with emery and oil.—Hnglish Mechanic.

194 MINING AND SCIENTIFIC PRESS. [September 26, 1874. Refining Base Bullion. A correspondent of the Eureka Sentinel gives the following description of his visit to tbe Germania Refining Works, situeted about six milee south of the Salt Lake city, on the Utah southern railroed. The main objéct’ of. these works is the separation of the precious metels from the leed in the so-celled base bullicn, by means of zinc, or, technically speeking, the desilverization of lead by zinc. As it may not be nninteresting to a large number of yout reeders to get an idea of the exeention of this rocess, I willin tbe following try to give a Brief description of the menipnlations carried on atthe works above mentioned. Previously it will be necessary, however, to make a few general remerks. Tho zine desilverization precesa.is based upon the following facts: = 1. Zinc has a greeter affinity for silver and gold than lead. 2. It does not form an alloy with lead. 8, It has a lesser specific gravitythan lead. * 4, The melting point of zine is et 412°C., while that of Jeed is et 334°. If metallic zinc is added to molten base bnilion at a temperature higher than the melting point of the former, the zinc forms an alloy with the gold and silver of the lead bullion, and, in cooling down, rises to the: snrface of the now impoverished lead, which must be kept in a state of fusion, covering the whole of the lead in the shepe of a hard scum—the zine senm. ‘This scnm is teken off from the leedbath, and’as it still contains a large percentage of lead, is subjeoted to:a liquetion process, by which the lead is sweated out to within about 21% per cent. Thé zine scum from this operation is the silver producsr; the reméining lead being zinciferous, must be softened, end is then ready. for,the market. From the above, it would appear thet the zine process is composed . of three main operations: : + 1. The desilverization of the lead bullion. 2. The dezincifioation of the poor lead. 3, The desilverization of the zine scum. Desilverization of the Lead Bullion. After the bullion is sampled and assayed, from 20 to 22 tons are introduced into a large calcining furnace, the bottom of which is encased by e strong cast-iron box. Here the bulliou is melted and then subjected to a dull red heat, air being admitted through the work-doors, whereby most of the mecbanical impuritiss, consisting of iron and coppsr mette, and a portion of the antimony, arsenic ‘and copper, in the shape of their oxides, are bronght to the surfece of the metal, in cnseqnence of their lesser specific gravity. These impurities are known nnder the name of dross, As soon es the surface of the metal is completely covered with dross, this is skimmed off and removed throgh ithe work-doors. It still contains precious metels. Wewill call it ‘‘first dross.’’ The lead bullion in this celciner is then tapped, end, by means of an iron spout, conveyed into either one of the two largest of a system of five cast-iron desilverizing pots. These pots, or kettles, are set in the shape of a wedge, the two lergest ones forming its basis, the smallest one the point. As the works are rnnning at helf capacity at present, that is, 20 tons of bullion per 24 honrs, only one series of pots is in use, viz: one large one, one middle one end the one at the point. Hech pot has its separate fireplece, which derives its draught, like all the other fnrnaces, from a stack 90 feet in hight. The Lead Bullion In the first potis now exposed to a temperature high enougb to smelt @ certain percentage of zino, which is added ina sort of an iron cege attached to a stirring contrivence. As soon as athe zine is believed to be sufficiently mixed with the bullion the stirring epperatus is withdrewn end the temperatnre ellowed to go down to the melting point of leed. The scum, which now rises to the surfece, is ladled over into the adjoining smaller pot, melted, stirred, and cooled, and skimmed as before, the skimmings being transferred to the last and smallest pot, in which they have to nndergo the.same manipulations. The scum from this last pot is the rich scum and goes to the alloy furnace. The leed from the second and third pots is returned to the first pot by meens of a connecting gutter, ‘into which the lead is ladled. Hereafter a second eud ‘afterward a third addition of «zine is mede in pot No. 1, and the ensuing scums are treated in the samé menner as before, with the sole exception thet’ the final scums are not taken to the alloy furnace, but are nsed over: again instead of metallic zinc, they being too poor‘in precious metals. The liquation lead (lead sweated out) from these laet zine addition, is returned to the firet pot, whereupon the ‘latter is emptied, through a spont atits bottom, into a softening furnace— of which there are'two, one connected with each large pot. Dezincitication of the Poor Lead. The lead from the first pot is now practically desilverized, ae it containe only 15 grammes of eilver, or less than 1-11 of on ounce in the ton; but itie hard, owing to a small percentage of zinc being retained in it, and to the presence of arsenic and antimony, if such have been in the . To remove these impurities the lead is exposed to 2 dull, red heat in the softening furnace, and from time to time stirred with a hoe to offer a new surface to the As soon as the lead is perfectly covered with dross, and the samples teken out of the furnace from.time to time by their peculiar luster.and crystalline texoriginal bullion, oxidizing agency of the air, ture demonstrate its purity, the drogs is removed through the work-doors and the lead is tapped into a large cast-iron pot with fire-place. Here the lead is poled for several hours, thet is, stirred with a pole of green wood, whereby it assumes a bubbling motion and thus gives a large number of surfaces to tbe air. By this ) operation the lest traces of zinc are removed. Through a movable spout at the bottom of tbe pot the lead is run into molds branded “selected’? or “common” lead, according to its purity. The ‘dross is reserved for further working; we will call 1t poor lead dross. Desilverization of the Zinc Scum, The rich zine scum, es I said before, is treated in the alloy furnace. This is a blast furnace of smalier dimensions than the enormous*ore-smelting furneces of Eureka. The scum is sinelted in. conjunction with pieces of Serap-iron and cre-slag, Pennsylvania coke serving as a fuel. The smelting is doneata low temperature under a pressure of blast. By this operation the. zine is, for the most part, 7) volatilized as oxide of zinc, which is caught iu . a condensation chamber atteched to the furnace; but the silver and gold remain with the lead, which was intermingled with tbe zinc scum. This “rich lead’’ is tapped below the furnace-hearth and ladled into molds, aud is tben pussed over to the cupelling furnaces. The slag is not kept running coutinuously, but tapped at intervels, the breast of tbe furnace being closed in the meanwhile. Tbe slag is jused over in the ore-smelting furnaces esa flux. As enother residual product, we heve zincifarous iron-sows, which form a crust around the heerth of the fnrnace and have to be detached ‘by mechanical means. ‘They look very much ‘like’ our speiss or ‘‘iron,” as it is commonly tion of galena. The rich lead is cupelled iu an English Cupelling Or refining furnace, of which thero are six ‘in the works. The bottoms, cupels or tests, of these furnecss are made of bone ashes, and have an oval shape. Before use they are dried and anneeled. Tbey-resf on two strong iron bars in tho farnace proper. Attho back wall of the furnace there is an opening for the blast, which is created by steam, and on each side of it a charge-hole. At tbe front well there is-an sideways from the test there is a fire door. The test is placed in the furnace in such a manner that the plane ofits long axis passes through the center of the tweer-opening and the discharge. The cupelling process is based upon the following circumstances: If en alloy of leat aud and precious metals is fused and then exposed to a enrrent of eir, the entire lead is gredually converted into oxide of or litharge, asit is generally termed, leeving fiually an alloy of the precious metals, The rich lead is now introduced through the cherge-holes in the test, ber by bar, and melted. As soon as the test is filled up to the rim the blest is turned on and the heet kept up at the same time. The Formation of Litharge Begins, which is partially absorbod by the porous test—pertially drawn offinto a gutter cut into the test on the discbarge side. The lithargeis run into pots monnted on wheels, end removed when filled. As soon as the metal bath has decreased sufficiently in size more rich lead is introduced into the cupel, till it is supposed to contain tbe quentity of siiver desired. The blest is continued until the brigbtening of the silver has teken place, when no more litharge is perceptible, and then the operation 1s finished. A hole isnow bored into the bottom of the test, and the refined metal drewn off into melds resting on a movable frame, The silver bars thus obtained sre remelted in bleck lead crucibles, cast into ingot molds, assayed, and cari now be sold to tbe banks. They are then .996 fine. The litharge is acoumulated for furtber treatment. The test is broken np and assorted. The Untarnished Portions Of it are used over again, while the balance goes to the ore smelting furnace for tbe extrection of the metels it contains. It now remains for us to state briefly what is done with the residual products, in which there is still a good deal of money value hidden. Tbe first dross from the calcining furnace is liquideted ina furnace constructed especially for that purpose by Mr. Weise, the superintendent. Itisareverberatory, with two bottoms, one above tbe other. The upper one is composed of grate-bars with narrow slits, and is charged with the dross. -The lower one coneista of composition, and has a eteep pitch toward the tap-hole, in front of which there is a cast-iron receptacle. The temperatnre is now conducted so that the lead trickles out of the dross into the lower hearth, but leaves the balance unfused. ‘This droesis then withdrawn, and smelted for copper-matte, with iron pyrites, which is not further treated on the epot. The lead goes back to the desilverizing pots. , The Poor Lead Dross Is smelted directly with sleg for antimonial or hard lead (type metal) in 1 cupola furnace. This lead commands agood price, The litharge , from, the cupelling furnaces ie revived in a reverberatory furnace; that is, it ia mixed with stone coal, exposed to a melting heat, whereby it is reduced to metallic lead. As the litbarge ie neither very pure nor free from silver, the reeniting lead has to be returned to the desilverizing pots. ‘ ‘. Exclusive of {the furnaces heretofore men: ‘celled, and mey be used in the desulphuriza. tioned, thore are three more furnaces on the ground destined for the reduction of rew ores and by-products. One is an English flowing furnece, for the production of lead bulljon and gray slag (slag rich in lead) from rich gelena ores. Tbe gray slag is turther treated in one of the two remaining cupola or blest furnaces.

I herdly need to sey tbet all ores not fit for the reverberatory ere smelted in tho latter with the proper finxes. The Blast Furnaces, One of which is provided with all the modern appliences (water jeckets)receive their blast from a large-sized Sturtevant fen, propelled by a 45-horse-power engine. All the furneces are provided with dust-chambers connected with flues, wbiob run into the main fiue, the latter terminating into a tall stack. The only fuel required at the works is raw stone coul for the reverberatory furnaces, desilverizing pans and the steam-engine, and coke for the blest and assay furnaces, : Finelly, I cennot forbser to praise the urbanity and willingness of the gentlemen in charge to give inform ation—Mr. Billing, the business mianager, end Mr. Weise, the superintendent. Low Grade Ores. The question of the utilization of low grede ores, says the Eureka Sentinel, is one which hes, heretofore, been too generelly overlooked throughout Nevada. In Europe a system of concentration is now and has been for many years in suecessiul operation, end through its means very nearly all crude ore is prepered for the reduction. What little rich material occurs throughout the vein matter is carefully separated by hend; whilst tbe residuum, by far the major portion, is orushed, jiggsd, passed over the shaking table, round buddles and plane tables, "until a working preduct is obtained ready for the final manipulation, generally in the furnaces. It would surprise the majority of our millmen to leern how small a yield in the lead and the precious metels is deemed worthy of-apreparatory treatment. It is not unusual to submit to oonesntration ores which will jassay two to three per cent. of leed, with from five to $15 in silver t» the tou. So perfect, indeed, is the mechanical errangement of many i i 5 opening for the discharge of the litharge, and . of the works thet as high a8 75 stamps may be seen at work and not a single attendant in sight. The batteries are self-feeders; the crushed pulp passes {first into and over a series of obloug boxes, fitted underneath with pyramidshaped bottoms, from whence the sends, sinking euch according to their respective gravities, are projected through a metallio pipe upon a series of continuslly-moving sheking tebles. The very finest slimes are collected in properly proportioned settling tanks, whenco they are taken on tbe buddles to plane tables, The method of universe! application throughout England, France and Germany depends upon the agency of water, carrying along and holding in a temporary suspension the various comminuted particles of dre and gangue. With us, however, water iu sufficient quantity is not always attaineble, and the inventive genius of our people has been taxed to find enotber medium, which shall combine in a more delicete mauner all tbe requisites of quantity, elasticity and ease of applicetion. All these have beeu found in a combination of erushers, rolleis, separating sieves and jets of atmospheric air. The current of air may be regulated so that its wave-like impulses act on the suspended ore particles precisely as the weter in the jiggiug machines; in tact, being a more attenueted medium, it does not offer too harsh @ resistance to the most delicate atom of tbe so-called noble silver ores, and may be equally as well applied to the commonest of the base leed and copper minerals. Already, for several months, one of these ‘‘dry eir concentretors’’ has been in successful operation in Nevada, and we learn that another and larger machine is to be set up in one of our most successful mills. We shell wetch with more than ordinary interest the progress of the experimont, which is, indeed, in the right direction. Here, right in onr midst, there are thousends, not to say millions, of tons of low grade lead ore, which will_essay from five to eight per cent. in lead, and from, say, five to 15 dollars in gold and silver, which are practically wortbless. At best they ere, if of an irony character, only aveileble as flux. Conld they be concentrated, say four or five tons into one, they could be smelted with profit, We commend this snbject to the cereful consideration of our furnaco men, whom we shall endeavor to keep informed as the experiment to which we allude progresees. ManvractvkE oF CHLoRaTe of Porasu.— To manufacture chlorate of potash on a lurge scale, it has been recommended by W. Hunt to adopt the following method: Milk of lime is made to trickle down over bricks, pleced in a tower where it comes in contact with a coutinuous current of chlorine gas. Chlorate of lime is the chief prodnct, and, by treating this with chloride of potassium, chlorate of potash is formed, which can be purified by cryetallization. Narrenrr, a German pbyeicist, by more modern applianoes, eucceeded in obtaining a temperature of 220° below the freezing point of water, and Dr. Kane obeerved a temperature of 76° below it. Jonle, an eminent English physicist, calculated, from the law of the expaneion of gases, that a temperature of 459° degrees below the freezing point of water wonld probably be the absolute, zero. —_ New and Old Towns in California. The mining towns, says the Bulletin, of Calfornia have been ‘‘cremeted’’_onoe, twice, and some of them three timos. The very bones of these towns have besn burned np, And this has happened, genorally, after the resources throngh which they have been built up have been pertially exhausted. Nevada at one time had a population of not less than 15,000; that is, there were this number which were near enongh to depend upon the postoffice in thet town. ‘Three great conflagrations have swept over the town, yet if is to-day just about as much of a place és it would heve been had no fire consnmed it. In the autumn, according to precedent, we expect to got the news of the burning of twoor three mining towns. The buildings are chiefly of wood. ‘There is always e Chinese querter with all the appliances tor touching off e fire suddenly; high winds and materiel exposed to. thé hot sux until it it almost ready for spontaneons combustion, will ordinarily insure a sweeping conflagration, And so it happens that nearly every mining town of eny prominence hes been tried by fire. Mokelumne Hill hes been swept for the sscond or third time. It will be restored again, beceuse its resources are not confined to 2 few wooden houses. The eigbt or ten thousend people who used to he tributery to the ‘‘Hill” are not there now. We shell heve only the 2,500, more or less, who will still cling t6 its fortnnes, and hold, with a good deal of justice, thet it is one of the healthiest and most picturesque towns in the world. After snch a disastrous experience the wonder is that greater precautions are not taken against fire in these mountain towns, Thus, at Mokelumne Hill there is a kind of-lava-rock nearly or quite fire-proof, and yet so soft whan itis uncovered thet it can be cut with an ax, and cen be prooured witbout limit. We do not hear that any of the buildings coustructed of this rock were destroyed. In the vicinity of all tho mining towns there is an abundance of rock within eesy reech which may be had without other expense than thetof healing. The rough stone cottage is cheap end comfortable. There are no earthquakes in the mountains to shake it down, and the fire will not consumeit. If these mountain towns were construoted from thg waste rock everywhere accessible, they would be among the most picturesqne towns in the world. But in respact to combustible material, the mining towns are herdly worse off tban is San Francisco. We have a wooden weter-front, and two-thirds of the area of the city is covered with wooden buildings. We havea better police supervision end a moro efficient fire dspartment. These are dboutall we have toreduce the contingencies of a sweeping conflagration. An artisan has recently shown the practicability of inclosing ell wooden houses in cities with a brick sbell. He demoustrates thatitcan be done at comparatively small expense, thet the value of houses so treated is grsatly enhanced, and that all objections to wooden houses would be thereby avoided. Tbe brick shell would sustain only its own weight, and there wonld be little reel denger from earthqnakes. These double houses may yet come into favor, but we are not ready for them yet. At preasnt, wooden housss are popular, aud the more so as they admit of much cheap and meretricious oruamentation. New mining discoveries will create new mining towns, and these will follow the fortunes of the mines toalarge extent. But the most promising new towns will spring up along the coest. A considereble town will resnlt from the colony settlement of tbe Lompo ranch, just north of Point Conception; Monterey will be recuscitated, partly through the influsnce of a locel railroad, and the development of agricultural wealth. Santa Berbare has grown from a Mexican hamlet to its present dimensions within the last eight years; and San Diego, with & fine harbor iu front, end a paper reilroad in the rear, hes done wonders. It is now evident that there will be a chain of flonrishing towns along the coast, built up largely throngh agriculture end local commerce. These will never go beckward, beceuse the chief elements of prosperity are not likely to fail. In early times there were towns laid ont, like ‘‘ New York of the Pacific,” which never came to anything. They were sterted without resources and es @ crazy speculation. They never pregressed far enough to furnish a respectable rnin. But the new coast towns, deriving their life from populetion and bnsiness, will be both permenent and prosporous. There is room for at least 20such towns. Many of them may be swept by fire as the mountain towns have been. Bnt the white wooden towne by the sea will be likely to hold on their way until the bottom falls out of agrioulture and commeree—which will certaiuly not be in our time. Frenow Ratuwaxy Cazs,—Some of the double deck cars, which are quite common upon French roads, exhibit an almost extraordinarily emell proportion of dead weight. One on exhibition at Vienna, with a capacity of 90 persons, weighed only 11.75 tons. Freight oars weighing but 10,000 pounds carry 20,000 or even as much as 30,000 pounds. * «om & at nvab ted Lap For Ponisuino.—I, dare aay many will at once say ‘‘ Itwon’t do,” but for many purposes ‘Ho emery glued oh anything, or made np in any way, is so simple and effecinal asa plain piece of hardwood tured to the shape reqnired, and smeared with emery and oil.—Hnglish Mechanic.