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NOTES 
 
 ON THE 
 
 TREATMENT OF MERCURY 
 
 IN 
 
 NORTH CALIFORNIA. 
 
 BY 
 
 T. EGLESTON, Ph. D., 
 
 COLUMBIA SCHOOL OF MINES, NEW YORK CITY. 
 
 [FROM VOL. Ill TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS.] 
 
 PHILADELPHIA: 
 
 SHEKMAN & CO, PRINTERS. 
 1 8 7 6 . 
 
Digitized by the Internet Archive 
 in 2016 
 
 https://archive.org/details/notesontreatmentOOegle 
 
NOTES ON THE TREATMENT 
 
 OF 
 
 MERCURY IN NORTH CALIFORNIA. 
 
 The ores of mercury of North California are composed of metallic 
 mercury and cinnabar. They are found in serpentine, and are very 
 often associated with chalcedony, in masses more or less irregular, 
 often concentrated enough, however, to furnish ores yielding from 
 three to ten per cent., and sometimes richer. This deposit makes its 
 appearance in Vallejo where it has been worked. North of here 
 the mines are more developed. Most of the quicksilver mines, how- 
 ever, are situated in Sonoma and Napa Counties. On its outcrop 
 the serpentine rocks have become decomposed, and have often been 
 washed away to a considerable depth, so that in many cases in their 
 neighborhood, what is apparently nothing but ordinary dirt, will 
 frequently contain from two to three per cent, of metallic mercury, 
 with but a trace of cinnabar, in which case, as at the Sonoma mine, 
 it is made up into adobes and distilled. Such material does not 
 require to be mixed with dirt to be made into adobes. Very often, 
 also, the outcrop of the rock, where it is not decomposed, is filled with 
 metallic mercury, so that by striking a pick into it, as at the Rattle- 
 snake mine, a pound or more of mercury at a time will sometimes spurt 
 out. Such rock as this is found in several localities in every stage of 
 impregnation, and usually makes very rich ore. There is generally, 
 however, very little of it, and it is found only in the first workings ; 
 the ore in depth is always cinnabar. At the Rattlesnake mine near 
 Pine Flat, where large quantities of metallic mercury are found, the 
 rock contains so much petroleum that it has been necessary to make 
 special arrangements to burn the carbides of hydrogen, since the dis- 
 tillation of the petroleum causes an extra quantity of poor soot to 
 be formed in the condensation-chambers. At the Geysers the ore is 
 associated with large quantities of sulphur and gypsum, so that in 
 a hand specimen there is often more sulphur than cinnabar, which, is 
 
 2 
 
 
4 
 
 NOTES ON THE TREATMENT 
 
 a serious impediment to working, especially for the modern style of 
 furnace with iron condensers, and causes so much soot to be formed 
 that it has been known to penetrate as far as the blower, and to so 
 completely clog it as to prevent its revolution. 
 
 The ore coming from the mine is more or less hand-picked. In 
 one or two cases attempts have been made to treat the poorest, and 
 especially the very fine ores, mechanically as at the California works. 
 The apparatus used for the purpose is very rude, and the treatment 
 does not seem to be very successful, as there is visibly a considerable 
 loss in the tailings. 7 
 
 Usually the fine ore is not concentrated ; it is taken as it comes 
 from the mine, mixed with dirt and made up into adobes, which 
 have no regular size or weight, and treated in the furnace. 
 
 The processes by which the ore is treated are, first, the process by 
 precipitation ; second, by roasting. The precipitation is done in 
 retorts with lime, and consists of oxidizing the sulphur by means of 
 an excess of air, and so producing sulphate of lime and free mercury. 
 The roasting is done either in retorts, or in other furnaces which are 
 not continuous, and in several styles of continuous furnaces. The 
 reaction consists in volatilizing the sulphur and oxidizing it so as to 
 produce free mercury and sulphuric acid, which, with the moisture 
 of the fuel and ore is condensed and allowed to run to waste. The 
 furnaces which are not continuous are a modification of the old Idria 
 furnace, which is used at Knoxville and at New Almaden in South 
 California. Those which are continuous are the Luckhart, which is 
 used at Sonoma, and which was being built at the Rattlesnake mine 
 and elsewhere ; and the Knox furnace, which is in very successful 
 operation at the Redington, Manhattan, and the California mines, 
 and elsewhere. There are a number of other varieties of furnaces, none 
 of which, however, I saw. To these processes should be added the 
 process of distillation, if the metallic mercury of the outcrops were 
 found in sufficient quantities to warrant the ore being treated alone. 
 This, however, has never been the case, and the small quantities that 
 are found are charged in the furnace with the other ores, either as 
 rock ore or as adobes. Very little effort is made to sort the ore, and 
 this generally consists in a rough attempt at hand-picking. No as- 
 says of any kind are made. The furnace manager, or miner, judges 
 by the eye that the ore contains one, two, three, ten, or twenty-five 
 per cent., as the case may be, and hence there is little faith to be 
 placed in the statement of many of the advocates of different kinds 
 of furnaces, that their furnace yields such and such a percentage of 
 the assay value. 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 5 
 
 The mercury produced is put up in iron flasks, which contain 
 76J lbs. each, with an iron screw for a cork, and shipped. Irregu- 
 lar flasks, as they are called, contain less or more. 
 
 METHOD OF DISTILLATION. 
 
 AMERICAN MINE. 
 
 At the American Mine, near Pine Flat, all the ore is crushed fine 
 in an ordinary California stamp-mill, with a battery of ten stamps, 
 which is run at a high velocity. It is then mixed with lime, and 
 treated in retorts. The average yield of the ore is said to be two 
 per cent. 
 
 There are twelve retorts 9 feet long, 2 feet wide, and 18 inches 
 high in the middle. They are made of cast iron, and are D-shaped 
 like the ordinary gas retort, and are arranged in benches of three, 
 the centre one being the highest, so that there are four fireplaces to 
 the twelve retorts. The charge consists of 150 lbs. of crushed ore, 
 to which ten per cent, of quicklime is added. This charge is intro- 
 duced into the muffle in an iron spoon 6 feet long, 9 inches wide, 
 and 6 inches deep. This is carried by three men, one taking the 
 end, which has an iron handle 2 feet long, with a crossbar of wood 
 of the same length. The middle is supported on an iron bar, curved 
 in the middle to fit the shape of the spoon, with handles projecting 
 18 inches from the sides, and is carried by two men. This spoon is 
 introduced into the muffle and shoved to its end. It is drawn out 
 by short jerks, so as to leave the charge in the retort. The doors of 
 the retort are then fastened by means of thumb-screws, and luted 
 with wood ashes, and fired during four hours, when the charge is 
 withdrawn. Not over 500 lbs. per retort is treated in twelve hours. 
 
 The condensation pipes are in the back of the retort. A pipe, 
 about 18 inches long, connects each retort with a vertical pipe about 
 5 feet long, which connects with a horizontal pipe 6 inches in 
 diameter, placed in a water-tank at a lower level than the front of 
 the furnace, and which receives the pipes of all the retorts. Every 
 six retorts are so arranged that they discharge their condensed mer- 
 cury through a siphon pipe. 
 
 The soot is treated with lime as is usual. 
 
 These works are new and carefully built. It is surprising to see 
 works upon which no expense seems to have been spared, apparently 
 put up to treat such very small quantities at a time of very lean ore 
 by such a system ; not even the possible economy of the retort sys- 
 tem seems to have been taken into account. There did not seem to 
 be sufficient care taken with the condensation apparatus, for the air 
 
6 
 
 NOTES ON THE TREATMENT 
 
 for some distance from the works was filled with mercurial vapors ; 
 and though the workmen wore wet sponges over their mouths and 
 noses, most of them were more or less salivated. I did not visit the 
 mines; but any mine which would justify such carefully erected 
 works with stamp-mills, would certainly justify the erection of other 
 and less wasteful furnaces. 
 
 METHOD OF ROASTING. 
 
 The method by roasting is the one which is the most extensively 
 used, and all the different varieties, of furnaces are adapted to it. 
 Those most in use are retorts, and the modified Idria furnace of the 
 non-continuous varieties, the Luckhart and the Knox furnace of the 
 continuous ones. 
 
 NON-CONTINUOUS FURNACES. 
 
 Missouri Mine. 
 
 At the Missouri mine, near Pine Flat, the average yield of the ore 
 is from one-half to 2 per cent, of mercury. The cinnabar is irregu- 
 larly scattered through a chalcedony found in very irregular masses 
 in serpentine ; the large pieces are crushed in a Blake’s crusher to 
 about 1 cubic inch in size. There are two benches of retorts, one con- 
 taining two retorts and holding 250 pounds of charge at a time, and 
 the other containing three retorts and holding 350 pounds, so that 
 the small retorts treat 1000 and the large ones 2100 pounds in 
 twenty-four hours. The large retorts have been in use but a short 
 time, and have consequently produced but little. The retorts are 
 D-shaped, and are here 9 feet long, 12 inches high, and 18 inches wide 
 on the bottom ; they are charged every twelve hours by means of a 
 shovel. At the Lost Ledge mine the same company have three 
 retorts which are only five feet in length, and have a capacity of 500 
 pounds, or 160 pounds each ; they are charged every four hours, and 
 consequently treat 3000 pounds of ore in twenty-four hours. It 
 takes three-quarters of an hour at the Missouri mine to discharge 
 and charge the large retorts, and half an hour for the small ones, 
 so that, as there is not much difference in the wear and tear, the 
 large size retorts are the most advantageous. They are never filled 
 full, as there would be danger that the pressure of the discharging 
 vapors might force an exit through the luted joints. 
 
 When the furnace is ready to be discharged the men cover their 
 mouths and noses with wet sponges, tied on with bandages, and then 
 remove the cover of the retorts. When they are about to be re- 
 moved a little fan placed on the condensing pipes is set in motion to 
 cause ah aspiration through the retorts, so that no mercurial fumes 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 7 
 
 escape. When the fumes cease to be dense the charge is drawn out 
 of the retort with long hoes on to the floor in front of the furnace. 
 The discharged ore is at a cherry -red heat, and, as it is not entirely 
 free from mercury, a considerable quantity of fumes are given off so 
 that the precaution of using the bandage over the mouth and nose 
 is indispensable. After the ore has all been raked out, it is carried 
 as quickly as possible a short distance from the furnace and extin- 
 guished with water, a new charge being put in in the meantime. 
 This is an exceedingly bad system, as the workmen are constantly 
 exposed to fumes, more especially when water is scarce, since small 
 quantities at a time thrown on the very hot ore seems to increase the 
 quantity of fumes. The men, however, seem to know this, and 
 take the necessary precautions, as none of them were salivated. The 
 product of the small retorts varies from 3f to 70 pounds of mercury 
 in twenty-four hours. The large ones yield from 10 to 100 pounds. 
 
 As the two benches of retorts are at some distance, each bench 
 requires one man per shift of twelve hours, who is paid $3.75 a 
 day. They burn 3J cords of wood in twenty-four hours. Wood costs 
 $6 per cord, and labor $64 per month with board. Each retort is 
 connected by a short joint, with a horizontal pipe leading to the 
 condenser, which must be large enough to insure of its not being 
 clogged by the soot. This pipe is of cast iron, and is 30 feet long 
 and 6 inches in diameter. The pipes leading from the retorts, in 
 the latest and best construction, come from the back, where there is 
 plenty of* room and they are not in the way, so that they can be 
 large. Formerly they were made to come from the front, where 
 they were in the way of the workmen, and were constantly in danger 
 of being damaged by the charge lying against them as it was drawn 
 from the furnace. 
 
 The condensing apparatus consists of two cast-iron boxes 3 feet by 
 2, and 2 feet high, turned down into cast-iron tanks, with inclined bot- 
 toms, which are covered with water. From the bottom of these tanks 
 a wrought-iron pipe, curved in the shape of an S, is placed, with the 
 arms sufficiently long to counterbalance the pressure of the water, so 
 that the mercury flows from it continuously. The mercury commences 
 to flow two and one-half hours after the charge is put in. Between 
 the two cast-iron boxes, which are connected with each other, and on 
 the main pipe, a small fan-blower is placed, and is made to suck out 
 the vapors from the retorts, or when the condenser is to be cleaned 
 into an exterior pipe. The fan is inclosed in a box 18 inches square, 
 into which there is an opening 1 foot in diameter, closed with a hy- 
 draulic packing. The pipesand condensers are cleaned once a week. 
 
8 
 
 NOTES ON THE TREATMENT 
 
 In the small furnace 140 pounds of soot and mercury together 
 are collected ; this is put into a sheet-iron pan, 8 feet long, 3 feet 
 wide, 6 inches deep, inclined about 25°, which is not fixed, but is 
 moved from place to place as convenience may require. The soot is 
 placed at its upper end, and is worked with a hoe for a quarter of an 
 hour, to separate the free mercury. Three to five pounds of unslacked 
 lime without water are then stirred into it. As the soot is already 
 damp, the lime soon commences to slack ; it is left until it slacks en- 
 tirely. No one goes near it for one-half or three-quarters of an hour, 
 on account of the vapors arising frdpi it. It is then worked with a 
 hoe for three hours. About one barrel of lime, which costs $3 the 
 barrel, is used per week for treating the soot. The mercury as it is 
 collected runs into the lower part of the pan, and is taken out with 
 a ladle and put into fiasks. The residue, which has twice the bulk 
 which the soot originally had, is added to the next charge of the 
 retorts, in addition to the charge of ore. Such a charge will produce 
 about 10 pounds more of mercury than usual. From 140 pounds of 
 soot, 120 pounds of mercury are obtained directly, and about 10 
 pounds more from soot charged in the furnace. The large furnaces 
 were run 10 days; 200 pounds were taken from the first condensers 
 and pipes, and from 12 to 14 out of the second condenser. When 
 there is only a small amount of soot to be treated, a small cast-iron 
 sink 3 feet by 18 inches is used, the drain-hole being placed over an 
 enamelled iron vessel 1 foot in diameter, and 6 inches deep. This 
 vessel is used because ordinary kitchen utensils answer perfectly well, 
 and can be had much cheaper than special apparatus, which would 
 work no better. 
 
 The expenses are for twenty-four hours : 
 
 2 men at the retorts, $6.50 
 
 3|- cords of wood, at $6, 21 00 
 
 Lime for soot, ......... 50 
 
 Crushing the ore two days, at $1.25, 2.50 
 
 There does not seem to be any real economy in using this retort 
 system. The yield is not greater, nor is the cost of repairs and run- 
 ning less, while the risk of salivation is greater. There is certainly 
 an economy of first installation, and this seems to be the only reason 
 why such furnaces are used. With the high prices of quicksilver 
 w’hich have ruled during 1873 and most of 1874, every place where 
 ores could be found has been worked, and as all the deposits are 
 irregular and uncertain, the owners of such mines have not felt 
 themselves justified in going to any greater expense. I saw no well- 
 developed property, nor any property which appeared to have any 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 9 
 
 future, which was worked with retorts, except in a few instances, 
 where the retorts were put up to have a yield while other furnaces 
 were being erected on the property developed, or where the mines 
 were evidently being worked w 7 ith too small a capital. 
 
 MODIFIED IDRIA FURNACE. 
 
 Redington Works. 
 
 As an example of non-continuous working with shaft furnaces, I 
 have selected the practice of the Redington mine, with the old Idria 
 furnace, which is by far the largest mercury works in North California. 
 But as everything relating to this variety of furnace, which is destined 
 in a few years to disappear altogether, is of interest, I have added 
 some details relating to the New Almaden furnace of the same type, 
 which I visited shortly after, although they are south of San Fran- 
 cisco. Great attention is being paid to the question of condensation, 
 which is, perhaps, even more important than that of the furnace. 
 The two questions are, however, intimately connected, and are en- 
 gaging the most serious study of all persons interested in the metal- 
 lurgy of mercury. 
 
 At Knoxville, the Redington Quicksilver Company treat the ores 
 from the Redington mine, which they own, in both the modified 
 Idria furnaces, of which they have two, and also in the Knox fur- 
 naces, of which there are two working, and two in the course of 
 construction ; besides these, two others are to be built. The furnaces 
 are situated at the mines and within a few feet of the ore shaft. The 
 mine produces 700 to 800 tons of cinnabar per week. The ore occurs 
 in a sand-rock, in serpentine. Much pure cinnabar is found, and a 
 considerable quantity of high grade ore, but the average yield of the 
 whole mine is about 3 per cent. Metacinnabarite is found in con- 
 siderable quantities in these mines. Epsomite, resulting from the 
 decomposition of the serpentine, also occurs here in very large quan- 
 tities, in acicular crystals over a foot long. The ore is largely asso- 
 ciated with pyrites. About one-tenth of the ore comes from the 
 open cut made in the side of the hill. From the mine the ore is 
 thrown upon screens placed one over the other ; the upper screen is 
 made of round iron bars 1 \ inches in diameter, placed 2 inches apart 
 at the top, and 2J- at the bottom. The screen itself is 5 feet wide 
 at the top, 5 feet 6 inches at the bottom, and is 8 feet long. Whatever 
 passes over this screen only, is hand-picked. What passes through 
 falls upon strong iron-wire screen of J-inch mesh. What goes over 
 the second screen goes directly to the furnace, and is charged with 
 the hand-picked ore ; what passes through is treated as fine ore ; all 
 
10 
 
 NOTES ON THE TREATMENT 
 
 the large pieces are broken by hand. Before the Knox furnace was 
 introduced, the ore was dressed by hand up to 5 per cent. 
 
 All the fine ore is mixed with dirt and made into adobes, which 
 are sun-dried and stored, for use in the modified Idria furnaces ex- 
 clusively. There is no generally adopted size for the adobes. They 
 are made in roughly constructed wooden frames, made by the work- 
 men, which wear out rapidly. The usual sizes are 9x4x4 inches. 
 When dry such adobes weigh 12 pounds. They are sometimes 
 made 12 x 5 X 5 inches, which is <a very large size. Such adobes 
 weigh 18 pounds. The smaller siz6 is the one most generally used. 
 Seven men, at $2 per day, can make 6000 adobes. Each man can 
 mould one thousand, but the six men require one man to loosen and 
 moisten the dirt, and to mix the ore with it. Making the adobes 
 costs, therefore, $2.33 the thousand. The cost of the adobes deliv- 
 ered at the furnace, ready for charging, including making, carting, 
 and storing, is $5 the thousand. 
 
 The modified Idria furnaces (Plate VIII, Fig. 1) are built one on 
 each side of the condensers, which are at right angles to them. Each 
 of these furnaces is capable of treating 100 tons of ore with 4000 to 
 5000 adobes per week. They are built of a porous sandstone, which 
 is found a short distance from the works. Each furnace has a double 
 fireplace, B, 20 inches in width, 17 feet long, and 15 feet high, from 
 the spring of the arch of the fireplace. The total inside height of the 
 fireplace compartment is 20 feet. It has on the ore-chamber side a 
 brick screen pierced with fourteen openings, the size of one brick, and 
 two bricks apart, across the furnace, and fourteen openings in height, 
 also two bricks apart. ' The fireplace wall has been repaired once in 
 seven years. It is made of red brick, and is glazed by the heat. 
 The ore chamber, C, is 13 feet by 10, and 20 feet high. Its walls are 
 4 feet thick. There are two ore discharge openings, 32 by 20 inches, 
 on each side, at the bottom, which are four feet above the ground. 
 The car for discharging the furnace runs under a swinging apron of 
 cast iron, and the ore which has been treated is raked out over it. 
 The fireplace and condenser wall are each mere screens of brickwork 
 filled with holes, which are the starting-points of the flues, made in 
 the charge. As the condenser side is constantly exposed to the acid 
 vapors, it is the one most rapidly worn. It has been renewed twice 
 in five years. It is now strengthened with an abutment. From 
 constant use the inside walls round the ore-chamber have become 
 worn away, making its present size somewhat larger than it origi- 
 nally was. Beyond the ore-chamber each furnace has two sandstone 
 condensers, D, which are 4 feet wide, 13 feet long, and 20 feet high, 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 11 
 
 in which very little material ever collects, never more than two flasks 
 of mercury a week. 
 
 In the drawing, Fig. 1, Plate VIII, these furnace condensers are 
 connected with the main condensing chambers, A, by the flues, E, 
 which are supported upon arches, and which enter the top of the 
 first chamber of the main condenser, A. The length of the flue 
 between the furnace and the main condenser is 8 feet, and the fur- 
 naces are so arranged that each one may work independently into 
 the condenser, the connection being cut off at will. The total length 
 of each furnace, including the fireplace, ore-chamber, and two con- 
 densing chambers, is 36 feet, its total width is 17 feet, total outside 
 height 24 feet. The main condensers, A, consist of a series of twelve 
 chambers, each of which is 4 feet wide, 20 feet long, and 20 feet 
 high on the inside, contained in a structure at right angles to the 
 furnaces, and which is common to both of them. Each one of these 
 compartments has an iron door on each side on a level with the 
 bottom of the chamber. The inside walls of the condensers are 1 
 foot thick, the outside 18 inches. They are braced on the outside 
 with wooden beams 8 x 10 inches, which are tied with f-inches round 
 iron rods. These rods must be carefully watched, as they are likely 
 to become corroded through, and allow the wall to fall, and thereby 
 cause serious accident. 
 
 The walls of these chambers are soon saturated with mercury, and 
 become soft from the effects of the acid vapors. The stones are found 
 corroded for a depth of 6 inches, and some of the interior walls have 
 been corroded entirely through. Whenever they have been repaired 
 with brick, it is found to be quite hard and to resist much better 
 than the stone. 
 
 The relation of the condensing surface of the condensers to that of 
 the charging compartment is much too small. The relation of the 
 condensing volume to the volume of the furnace should be at least as 
 24 to 1. In this furnace, however, it is not more than one-half of 
 that amount. This would make the chambers only large enough 
 for one furnace. That the condensing capacity is not sufficient, is 
 evident, from the fact that metallic mercury has supersaturated the 
 stones, and still exudes in globules from the walls even after re- 
 peated cleaning. 
 
 The flue leading to the chimney is also built of cut stone, and is 
 250 feet long. It is oval, 4 feet in the highest diameter inside, 
 with walls 2 feet thick. It lies against the side hill. The chimney 
 is built of stone, with walls 3 feet thick. It is conical, 5 feet in 
 diameter at the base, and 50 feet high. 
 
 wWERS uurm;y 
 
 of HUNOlS 
 
12 
 
 NOTES ON THE TREATMENT 
 
 The furnace is charged by a windlass from above. The ore is let 
 down in iron buckets 3 feet in diameter, and 30 inches high. The 
 adobes are let down in iron cages that hold 150 adobes, which weigh 
 about a ton. This cage is 3 feet by 30 inches, and 2J feet high. 
 The charging compartment is ‘lined with adobes 2 to 5 thick, piled 
 close, but not crowded. Inside of this the ore is placed in pieces 
 from about the size of an egg to twice the size of the fist, in layers 
 of four, 18 to 24 inches in thickness, then four to five channels the 
 size of an adobe are built of adobes over the ore. Their number de- 
 pends on the size of the ore, five for fine ore, and four for coarse. 
 These channels start in the opening of the fireplace screen, and end 
 in the opening towards the condensation-chamber. They answer the 
 purpose of flues, and are necessary not only to provide a draft and 
 to allow of the heat coming in contact with the ore, but also to pre- 
 vent the charge from packing together. The poor soot, or that 
 which has been worked, is charged on top of every layer of ore. A 
 new' layer of ore is then put in, and so on, until the chamber is 
 nearly full. A layer of fine ore and poor soot is placed near the top, 
 and this is covered over with clay and straw. The compartments 
 are closed with cast-iron pans, which are filled with water, the joints 
 between the pans and against the masonry being made tight with 
 ashes or cement. These pans are 10J feet long, 4J feet wide, 5 inches 
 deep. The cold water flows constantly from an inch pipe into the 
 pan nearest the fireplace. A spout from every pan carries the water 
 to the next pan, so that they are always full. Each pan is provided 
 with two eyes at the sides for their removal when it is necessary to 
 recharge the furnace. One furnace is charged on Monday, and is 
 fired Monday night, and is kept burning until Thursday morning. 
 During this time two cords of wood are burned to each furnace. 
 The sulphur, to a great extent, answers for fuel, for there is always 
 an excess of sulphur in the shape of pyrites in the ore. The other fur- 
 nace is charged on Tuesday, and is fired Tuesday evening, and kept 
 burning until Friday. One furnace will thus be cooling on Satur- 
 day and Sunday, and the other on Sunday and Monday. A little 
 mercury commences to run in D on Tuesday, and in the 1st, 2d, and 
 3d compartments of the main condenser. It runs most freely Wed- 
 nesday and Thursday. By Thursday the mercury condenses quite 
 in the end of the condenser, but only in very small quantities; 150, 
 sometimes 200, flasks are collected from both furnaces during the 
 week; most of it comes from the 5th and 6th condensers. On Wed- 
 nesday it commences in the 5th and 6th, and runs from here con- 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 13 
 
 tinually until the furnace is discharged. The most of the mercury 
 is obtained when the furnace is cooling down. When the draft is 
 good and the ore moderately rich the yield will not be less than 200 
 flasks a week. 
 
 The bottoms of the condensing-chambers were originally built in- 
 clined toward the centre, as is shown in the lower part, Fig. 2, with 
 the intention of having all the mercury in all the condensers run 
 out through a common opening made for the purpose, but the open- 
 ings in the partition walls of the condensing-chambers very soon 
 became clogged, and so much mercury was absorbed in the masonry 
 that this was shortly abandoned. The present disposition is iron 
 pans sloping from the centre toward the outside, as is shown in the 
 upper part, Fig. 2, which are placed 3 feet above the furnace bottom 
 of the old construction, which has not been altered, so that there is 
 a space of considerable size under the bottom of the pans. The pans 
 are made in three pieces, which overlap each other. This is espe- 
 cially necessary, as when the walls get old and fall, the whole pan 
 would then be liable to be broken. Tiles placed upon the top of the 
 pans to protect them have been used with good effect. The castings 
 with this protection have lasted already four years, and are seemingly 
 perfect. The cast iron without the tiles lasts only two years, at 
 which time it is corroded by the sulphuric acid which condenses 
 from the furnace. 
 
 On Saturday the iron doors at the bottom of the condensation- 
 chambers are taken off, and a workman with a long hoe collects the 
 soot on the pan and that from the walls about two feet above the 
 bottom of the pan ; what is higher up on the wall is left to collect 
 there until it falls of its own weight. 75 to 100 bushels of soot are 
 collected in buckets every week from the bottom of the condensing- 
 chambers, which yields from 5 to 20 flasks of mercury. This soot 
 is a mechanical mixture composed of ordinary soot condensed from 
 the smoke of the fuel, ashes, fine dust and dirt carried over from the 
 ore, volatilized cinnabar, and sublimated mercury in very fine glob- 
 ules. It is usually taken from the condenser damp, owing to the 
 condensation of steam from the moisture in the fuel and ore, and the 
 acid vapors. This soot is removed in buckets, 14 inches in diameter 
 at the bottom, 30 at the top, and 33 inches high. Two such 
 buckets filled one foot high are taken from each side of the conden- 
 ser. Sometimes as many as eight, and sometimes not as many are 
 taken. It takes two men two days to clean out and work the soot 
 from all the five condensers in an ordinary working of the furnace. 
 The amount collected is very variable. When, for any reason, such 
 
14 
 
 NOTES ON THE TREATMENT 
 
 as a stoppage for repairs, the furnace cools, a large quantity of soot 
 becomes detached at the time the furnace is lit. The amount of 
 mercury collected from the soot varies from 5 to 20 flasks a week. 
 The flue leading to the chimney is cleaned once in two or three weeks ; 
 about one bushel of soot is taken from it. This is not kept sepa- 
 rate, but is mixed with that taken from the condensers. 
 
 It takes ten men one day to charge each furnace, and six men one 
 day to discharge it. The six men are paid about $35 per month and 
 board, making about $1.90 a dayy There is a fireman and one man 
 to clean and repair the flasks and to fill them. They work during 
 the day only. Each shift of twelve hours has its own foreman. 
 This does not include the men working up the soot. When the 
 draft is not good a fire is placed at the foot of the chimney, which 
 is fifty feet high, to increase the draft. The draft depends for the 
 most part upon the way the furnace has been charged, but is some- 
 times due to the direction of the wind. This draft furnace is oftenes.t 
 used when the furnace has been allowed to get cool. Not a cord of 
 wood per month is required for this purpose. In winter, fall, and 
 spring there is no trace of mercury in the flue, but when the weather 
 is hot it collects inside, near the top of the chimney, which is pro- 
 vided with a ladder in order to make any observations on the escape 
 of gases at the top which may be desirable. When the furnace is 
 out of repair in very hot summer weather, it is apparent that some 
 mercury escapes. The joints of the furnace are made so tight that no 
 accident arises from salivation except through the carelessness of the 
 men. As soon as the workmen experience any sensitiveness about 
 the mouth they are instructed to go to the office, and are there fur- 
 nished with a mouth- wash, consisting of 2 parts of cinchona, 1 part 
 tincture of myrrh, and 3 parts water, but no case of real salivation 
 except from the carelessness of the men, has occurred in a great 
 many years. 
 
 Twice in a year a general clean-up is made. This is done by 
 putting iron pipes, 24 inches in diameter, in compartment D, and 
 three in the flues leading to the chimneys, both to hasten the cool- 
 ing and ventilate them while they are being cleaned. The walls of 
 the condensers are cleaned by scraping. On account of the dust 
 arising from the falling soot, it is necessary, when this work is done, 
 for the men to wear a wet sponge over the mouth and nose, which is 
 covered with a thin cloth tied behind the head. At this work, the 
 men relieve each other every fifteen minutes. After scraping, the 
 walls are thoroughly washed. It takes eight men two days to scrape 
 and wash the walls, flues and condensers. The soot so detached 
 
OF MERCURY IN NORTH CALIFORNIA. 15 
 
 contains a large amount of mercury. From such a general clean-up 
 as many as one hundred flasks have been collected. The soot in the 
 first condenser is often 6 inches thick in concretions. It is here hard 
 and solid, but in the other condensers it is soft and light. The light 
 soot upon the walls is of very variable thickness, but is rarely less 
 than 1 to 2 inches thick. It sometimes reaches as high as 6 
 inches after a long run without cleaning. When there is very rich 
 soot it may often be as thick as 6 inches on the bottom of the iron 
 pan. The soot is richest in the fourth, fifth, and sixth condensers, 
 but it is always very unevenly distributed. In all the compart- 
 ments in the space below the iron pans a hard concrete, consisting 
 of hardened soot and mercury in globules, is found. 
 
 The furnaces with the condensers cost originally between $100,000 
 and $125,000; they have been built eight years, and have been re- 
 paired three times, parts of six partition walls having falling down 
 at the flue end. At the furnace end the wall is good. The walls 
 after having been scraped and washed every day for a month still 
 showed mercury in globules all over them, a few hours after they 
 became exposed to the heat of the sun. All the stone taken out of 
 the condensation-chambers during repairs is carefully preserved and 
 is treated as very rich ore. 
 
 The first time that the furnace was charged the ore was picked. 
 At the top of the charge, over the rich ore, 6 to 7 feet of rich soot 
 were put in, but the heat did not reach it. The charge being un- 
 usually rich, should have yielded five hundred flasks of mercury, 
 but all but nine flasks of it were absorbed by the walls. 
 
 This furnace has been definitely abandoned at Knoxville. The 
 masonry has been altered into Livermore’s inclined continuous fur- 
 nace, which is adapted to treat fine ores, and since its introduction, 
 in the earlier part of 1875, no adobes are made. The cost of alter- 
 ing the furnace was only $1200. 
 
 Average cost per week of reducing 1 ton of ore in the modified 
 Idria furnace, at the Redington mine, furnaces Nos. 1 and 2, in 1874: 
 
 5£ cords of wood at $5, $27.50 
 
 36 days, furnaceman,#fireman and his assistant, . . . 86.00 
 
 20 days, laborers charging furnace, . . . . .38.60 
 
 12 days, laborers discharging furnace, ..... 23.15 
 
 8 days, laborers working soot, 14.55 
 
 8 days, fireman, . . . . . . . . .14.55 
 
 9000 adobes at $5 per thousand, 45.00 
 
 Total charge of 200 tons cost, .... $249.35 
 
 Average cost per ton for reduction, .... $1.25 
 
16 
 
 NOTES ON THE TREATMENT 
 
 New Almaden Works. 
 
 At New Almaden, the Quicksilver Mining Company have six 
 furnaces of the modified Idria type, built of brick, which produced 
 in the year 1874, 11,042 flasks of 76 J pounds each, or 920 flasks per 
 month. Four of these have a capacity of 50 tons, one a capacity 
 of 70, and one 100 tons of ore a week. They run a week, so that 
 each furnace makes four charges a month. Each furnace has from 
 sixteen to twenty-two brick cond^nsing-chambers, the numbers vary- 
 ing with its ore capacity. The bottom of the chambers inclines from 
 the centre toward the doors. The floor is built of brick, and is 
 covered with cement. Beside the brick condensers, each furnace has 
 four to five wooden condensers, which are 26 feet long, 14 feet wide, 
 20 feet high, divided into six compartments of equal size. As the 
 result of the addition of these wooden chambers, one of the flues, 
 which formerly yielded in the general clean-up from 60 to 100 flasks 
 of mercury, yielded in the year 1873 only two flasks, and the largest 
 part of this was found near the outlet from the condensers, and no 
 signs of metal were found further on. 
 
 It is the present intention to cut up the blocks of brick condensers 
 by taking down the outside wall of one or more compartments, and 
 making the dividing walls the exterior walls of the new structure. 
 The former condensers will thus be divided into three or more 
 separate buildings. A much larger radiating surface being exposed 
 in this way, it is expected that the condensation will be much more 
 perfect. Adobes 10 x 4\ x 4J inches in size, made of the fine ore 
 mixed with dirt, are placed over the floor of the ore-chamber, one 
 adobe thick the entire height of the sides ; ore is then put 2J to 3 feet 
 in thickness, then a layer of adobes, in which five flues from one side 
 to the other of the furnace are made, and then ore, and so on to the 
 top. The top is covered with a layer of adobes, and then a layer of 
 straw 2 or 3 inches thick, and then ordinary clay and mud, to make 
 it even with the top, and over this ashes. Any cracks that may 
 occur are filled in with ashes. When the furnace is filled, one-third 
 of the charge will be adobes ; sometimes the furnace is run on adobes 
 alone. It takes six men one day to charg& the jiirnace. It takes 
 one man part of twelve hours to keep up the fire. It takes four 
 men one day to discharge it. The charging is done by the company, 
 as it must be carefully done, but the discharging, as it requires no 
 supervision, is done by contract. The fire is kept up for ninety -six 
 hours, and during this time 18 cords of wood are burned for 100 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 17 
 
 tons of ore. The wood costs from four to six dollars a cord. The 
 ore is discharged twelve hours after the fire is drawn ; twenty-four 
 hours afterwards the soot is taken out. 
 
 The mercury commences to condense fourteen to sixteen hours 
 after the furnace is lit. If the ore is very rich it sometimes com- 
 mences to condense in eight hours. It appears first in condenser 
 No. 1. In Nos. 1, 2, 3, 4, and 5, it runs for ten hours; after this 
 it runs in Nos. 3 , 4 , 5, 6, 7. It appears in No. 7 on the second 
 day, after which it ceases to run in the first four condensers, but con- 
 tinues to run in all the others. The greater part collects in Nos. 9, 
 10, and 11. Before the fire is drawn, half of all the mercury is con- 
 densed, which is in about forty hours, gradually diminishing until 
 it ceases to condense. A small amount of mercury still runs, how- 
 ever, the flow being kept up by the dripping from the walls. From 
 the bottom of each of the condensers there are small pipes leading 
 into an outside trough, to allow any mercury that forms to run im- 
 mediately into the gutter, from which it is discharged into the recep- 
 tion basin. 
 
 The iron doors which close the entrance to the brick condensers 
 have been given up, except for the first four or five chambers, and 
 are now replaced by ordinary glass window-frames 3x3 feet, with 
 six panes of glass. It is found that there is a material difference in 
 the condensation since they have been adopted. The condensers 
 made of wood and glass, which were patented in May, 1874, are 
 in successful operation here. They are certainly much cheaper, 
 and it would seem a much better condenser, and less likely to get 
 out of repair than the iron ones used elsewhere. This kind of con- 
 denser requires no water, and is, therefore, applicable everywhere. 
 The want of water in many places in California is often a serious 
 drawback to the working of the ores. Four such condensers are at 
 work at New Almaden. Each one has a volume of 2640 cubic 
 feet, and 1196 square feet of condensing surface, or altogether 
 10,560 cubic feet volume, and 4784 square feet of surface. They 
 have cost only $1500, which is the smallest cost for any such 
 amount of condensing surface known. If they work as well as they 
 promise they will replace at least half of the iron or brick con- 
 densers. 
 
 The soot is collected in the same way as at Knoxville. That col- 
 lected from four charges gave 18 flasks of mercury. The same four 
 charges produced 474 flasks. The soot condenses in all the con- 
 densers from No. 4 on; the most of it collects in 10, 12, and 14, or 
 about in the middle. On an average about a lime-barrelful per 
 
18 
 
 NOTES ON THE TREATMENT 
 
 week is collected from each condenser. One man does the whole 
 cleaning np. 
 
 The soot was formerly placed on an inclined plane, and stirred 
 and slightly rubbed with a wooden hoe. A certain quantity of 
 quicksilver separated and ran out into a vessel prepared for it, but 
 left a very large quantity still remaining in the soot, which was 
 afterwards treated with lime. This method, which is in general use 
 and takes a great deal of time,<^has been given up here. The soot 
 is now put into a hemispherical boiler about 3 feet in diameter; 
 it is mixed with boiling water from a vertical boiler, used for this 
 purpose only. About half of the bulk of soot is added in wood- 
 ashes, and the whole thoroughly stirred with an iron hoe for three- 
 quarters of an hour, when the separation is complete. It is then 
 allowed to remain an hour and settle, and during this time another 
 boiler is worked. The mercury collects in the bottom of the vessel, 
 and flows out of a siphon -shaped pipe, so that only the pure mer- 
 cury is discharged. The water is drawn off afterwards, and the 
 soot remaining behind is thrown into a heap, and when dry is placed 
 upon the top of the furnace near the flue where the flame passes, as 
 it still contains some sulphur. It is claimed that all the mercury in 
 the soot is separated in this way and with much less labor than by 
 the former method. This process was patented October 4th, 1873. 
 
 It takes one man, working ten hours, four to five days to work 
 the soot of six furnaces. 
 
 The fuel used here is wood, or ordinary charcoal made from oak, 
 or a mixture of charcoal and coke. It requires 75 lbs. of coke and 
 charcoal mixed to 3000 lbs. of ore and adobes, or equal quantities 
 in bulk. 
 
 This furnace, as used here and at Knoxville, must be considered 
 as a very great improvement on the old Idria furnaces, as there are 
 no arches in the ore-chamber which are likely to break down with- 
 out warning. 
 
 The method of charging large and small ores and arranging air- 
 channels by means of adobes prevents the charge from packing, and 
 gives all the space which is required for the circulation of the air 
 and heat, and allows of using a poorer ore than could be otherwise 
 used. The labor of making the adobes, which is, however, only 
 $5 the thousand, must be regarded as a necessary expense, as the 
 furnace could not be run without them ; as the expense of making 
 the air-channels of large pieces of ore would be too great, and there 
 would be no certainty that they would last if so made. The adobes, 
 however, do not change their form, and the air-channels once made 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 19 
 
 remain as they were made in the charge. The making of. adobes is, 
 however, one of the expenses to be avoided in the furnace of the 
 future, and the most careful attention now being given to the con- 
 struction of furnaces which will allow of the fine ore being treated 
 as it comes from the screens. Although this furnace, with its ex- 
 pensive, cumbersome method of condensation, is ,a great improve- 
 ment on the old Idria furnace, it is destined to disappear, and in a 
 few years will probably be cited as one of the curiosities of metal- 
 history. 
 
 CONTINUOUS FURNACES. 
 
 The continuous furnaces in use are all of them shaft furnaces, 
 which do not differ essentially in the principles of their construction, 
 though there are wide differences of detail, which are more or less 
 essential. The California practice is essentially different from that 
 of other countries, in that all of these furnaces are provided with 
 fans placed beyond the condensing apparatus, which not only do 
 away with the necessity of high chimneys, but give such an absolute 
 control of the draft that there is no fear of the fumes escaping. 
 The draft is always toward the interior of the furnace, so that 
 even if an aperture in the furnace or the condensing apparatus 
 should remain open, no fumes escape, and consequently cases of 
 salivation are very rare. As the velocity of the fan can always 
 be changed, the draft can be regulated at will to suit either the 
 working of the furnace, or the irregularities of the weather. The 
 furnace is of less consequence than the condensation apparatus, 
 though its aim should always be to extract the metal at the lowest 
 possible temperature, and to require the least possible preparation of 
 the ore. It is consequently on the condensation apparatus rather 
 than on the furnace that the greatest number of experiments have 
 been made; providing that the furnaces are continuous, the one 
 which has the best condensation apparatus will be the best. 
 
 There are a number of these furnaces used in California, all of 
 which I believe are patented. I saw, however, but two of them, 
 the Luckhart and the Knox, working. 
 
 LUCKHART FURNACE. 
 
 The Luckhart furnace is, in all respects, similar to the Swedish 
 furnace for roasting iron ores. It consists of a shaft with a fire-box, 
 with openings in the two sides only, which goes through the furnace 
 from one side to the other. It is covered with a cast-iron roof slant- 
 ing from the centre towards both sides of the furnace, so that the 
 
 3 
 
20 
 
 NOTES ON THE TREATMENT 
 
 charge is divided as it passes down, and the heat is also divided as 
 it passes up. The sides of the furnace are pierced with holes to ob- 
 serve what is passing in its interior, and to watch the progress of the 
 charge. The discharge door is sufficiently far below the grate to 
 insure the ore remaining long enough in the furnace to have all 
 of its volatile contents distilled, and to be sufficiently cool to be 
 discharged with perfect safety into an open wagon at the bottom. 
 By this system, which is common to all the continuous furnaces, the 
 inconveniences arising from the discharge of hot ore not entirely 
 worked are avoided. 
 
 The Luckhart furnace used at the Sonoma mine, is capable of 
 treating 15 to 18 tons of ore and adobes a day. The richest ore 
 treated has not contained over 10 per cent. The serpentine contain- 
 ing the mercury crops out near the furnace, and is very much decom- 
 posed. The rock is soft and crumbly, and where it is exposed to the 
 weather, its debris have been washed away so that the soil for some 
 distance from the outcrop is composed of its detritus, more or less 
 mixed with free mercury, and a very little undecomposed cinnabar. 
 Where the rock has been mined so as to reach the undecomposed 
 parts of it, it is found to contain in the upper portions more or less 
 free mercury mixed with the cinnabar, but nine-tenths of all the ore 
 treated consists of dirt taken from the surface of the ground, which 
 is made into adobes by Chinamen, The adobes contain from one- 
 quarter to one-half per cent. The rock does not contain more than 
 one and a half per cent. The adobes are made by mixing the earth 
 with water to a thick paste, and then putting it into wooden moulds 
 5 by 4J inches, and 4 inches high. The thick mud is simply placed 
 in a frame containing 8 of these moulds, patted with a shovel, the 
 wooden frame drawn up, and the adobes left to dry in the sun ; it 
 takes about two days to dry them. When ready for use, they weigh 
 about eight pounds each, and are a little larger than an ordinary 
 brick. One Chinaman can make a thousand in a day. The men 
 are paid $1.25, and find themselves. It takes two Chinamen, at 
 $1.25, to pick as much dirt as six men can use for making adobes. 
 
 The furnace is charged by means of a circular hopper 22 inches in 
 diameter, and 26 deep ; 5 to 6 of these hoppers full make a charge, 
 and 5 such charges make a ton. The hopper is covered over with a 
 hydraulic cover for safety, but even when it is off, the draft is so 
 strong that there is no discharge of mercurial vapors from the top 
 of the furnace, as I assured myself by removing the cover and hav- 
 ing the charge withdrawn below the hopper. The furnace consumes 
 one and a half cords of wood a day, which comprises all the fuel 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 21 
 
 used in the works. The wood is usually oak, and is worth $3 a 
 cord. About 15 tons of ore a day are treated. Most of the ore is 
 discharged from the bottom of the furnace black, some of the last of 
 a discharge is occasionally red-hot ; it is drawn about every hour 
 and a quarter into iron wagons, which hold about half a ton. There 
 are 7 men engaged in making adobes, and there is one Chinaman 
 and one engineer on each shift of twelve hours at the furnace ; the 
 Chinaman is paid $1.50, and finds himself, the engineer is paid $65 
 a month. The engineer helps the Chinaman, who draws the charge 
 and dumps it, and charges the furnace and puts in the fuel. In ad- 
 dition to the two helpers, there is one man engaged continually in 
 chopping wood. The total cost of treating the ore is one dollar per ton. 
 
 The condensing apparatus consists of three sheet-iron cylinders 
 five feet apart, which are 14 feet high, 6 feet in diameter. The va- 
 pors pass from the furnace through a pipe about 20 feet long, in at 
 the top, and out at the bottom of the condenser. A blower is placed 
 just beyond the last condenser, which is three feet in diameter, and 
 makes 100 to 120 revolutions a minute. If there is much fine stuff 
 not made into adobes charged into the furnace, it must be run faster. 
 The engine used is twelve horse-power, but six would answer for a 
 single furnace. Just beyond it is a wooden box, 6 feet high, 12 feet 
 long, and 8 feet wide, into which the blower discharges. This box 
 has a partition in the centre, which goes to within 2 feet of the bot- 
 tom, to break the current. From this box there is a flue 2 feet square, 
 and 100 feet long, ending in a wooden chimney 20 feet high. Around 
 the top of the condensing cylinders there is a lead pipe 1 inch in 
 diameter, pierced with small holes about 3 inches apart. When 
 there is a plenty of water it is allowed to flow continuously from this 
 pipe, and discharges itself over the outside of the cylinder, thus 
 cooling it. When there is a lack of water it is allowed to flow only 
 over the last condenser. The pipes which connect the cylinders 
 have in their interior a partition about 2 feet long, and on them 
 a considerable amount of soot collects. The bottom of the cylin- 
 ders incline towards the centre, and from here a pipe leads to an 
 iron kettle on the outside two feet in diameter, which is kept 
 constantly full of water. A large quantity of soot collects on the 
 sides of the condensing apparatus. A little of it constantly falls, 
 and is washed out into the iron basin by the condensed moisture, 
 which is but slightly acid, as there is but little cinnabar in the ore. 
 About one flask of mercury a day is collected from the first two 
 condensers. About one-half of this comes from the second. From 
 the third about a flask a month is collected. The cylinders are pro- 
 
22 
 
 NOTES ON THE TREATMENT 
 
 vided with doors, and the furnace is stopped once in three weeks to 
 clean out the soot, which is collected in kettles. About ten flasks of 
 mercury will collect from the soot after some stirring ; the rest is put 
 into an iron pan, 9 feet by 3, with a gutter in the centre. The pan 
 is set at an angle of 20°, and gently heated to about 120° F. ; it is 
 then mixed with lime or ashes and stirred. The mercury flows 
 readily from it, and about 70 per cent, of its mercury contents is 
 collected in this way. The resi is made into adobes and treated in 
 the furnace. 
 
 The more or less acid water which is constantly flowing into the 
 basin outside of the condenser, as it runs off carries away some light 
 mercury and soot. This is conducted to a wooden tank, 12 feet long, 
 6 feet wide, and 4 feet deep, where it collects and gives a product 
 which contains considerable mercury, which is treated as soot. The 
 soot comes from the basins, the wooden tanks, and sometimes a very 
 little is taken from the blower cylinders. This soot gets poorer as 
 it is further from the furnace. The richest contains 60 per cent, of 
 mercury and the poorest about 3. The product of the works is 
 about 25 to 50 flasks of mercury a month. 
 
 The condensation at these works seemed nearly perfect. The man- 
 ager stated to me that he had exposed a $20 gold piece for six weeks 
 from the top of the wooden chimney, and that he not only found it 
 there at the end of that time, but entirely unaffected by mercury. 
 There is so little sulphur in the ore that the sheet iron does not seein 
 to have been acted upon to any great extent. With this system of high 
 cylinders with a bottom converging towards the centre, there seems to 
 be but little opportunity for the action of the acid, and with a thick 
 cast-iron bottom there seems to be no reason why it should not answer 
 quite well. It would seem, however, that a few large compartments 
 could not give as good results as a greater number of smaller ones, 
 as a perfect condensation requires a maximum of surface, and does 
 not depend so directly upon volume, though the amount of soot 
 and mercury collected in the wooden box and in the last condenser 
 here seem to show that in this case, at least, owing probably to the 
 very small product of the furnace, the condensation was quite perfect. 
 
 KNOX FURNACE. 
 
 At Knoxville, beside the Idria furnaces, there were, in August, 
 1874, at the Redington mine, two Knox furnaces in the course of 
 construction, and two in work, which treated 25 tons of ore each in 
 twenty-four hours, and have been running since January, 1874. 
 During the years 1874 and 1875, two other furnaces have been con- 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 23 
 
 structed, making six in all, which treat together from 900 to 1000 
 tons of ore a week. Before the use of these Knox furnaces, and 
 while the modified Idria furnaces were the only ones in use at these 
 works, all the ore had to be dressed up to 5 per cent. Now ore 
 yielding not more than 1 to 1 J per cent., as it comes from the mine, 
 is treated, and Mr. Knox claims that he can treat profitably ore con- 
 taining not more than J per cent. A furnace about to be con- 
 structed is to be adapted to treat fine ore exclusively, and it is ex- 
 pected, if this furnace w T orks successfully, to give up making adobes 
 altogether and treat the fine ore here, and if the modified Idria fur- 
 naces are still retained, to treat in them only the large and medium- 
 sized ores. 
 
 The Knox furnace (Figs. 1, 3, 4, and 5) is a shaft furnace with 
 a fireplace upon the side. The total height of the furnace is 39 
 feet. The bottom of the fireplace is 17 feet 6 inches from the 
 bottom of the furnace, so that the fire itself is about in the middle 
 of the shaft. The furnace is rectangular in shape. At the top it is 
 2 feet square ; it continues for 2 feet at this size, and then widens out 
 • on one side, until at the depth of 4 feet it attains the width of 7 feet. 
 While in the other direction it continues straight for a depth of 10 
 feet, and then increases gradually until it becomes 7 feet at the fire- 
 place. At this point there are two chambers, Z and Z', Fig. 5, 
 arranged in the masonry, on one side for the fireplace, and on 
 the other, the space for the introduction of the pipe U', which 
 carries off the fumes. At this point, which is 17 feet 6 inches 
 from the top, there commence a series of six retreating arches, 
 which support the masonry of the furnace, four of which retreat 
 2 feet 6 inches on either side. The two others which are above are 
 much smaller, and reach to within 3 feet of the top of the furnace. 
 At the fireplace the furnace is 7 feet square. The shaft continues to 
 the bottom on the fireplace side of the same size. On the other 
 side it contracts equally upon both sides, so that at the bottom, 
 X Y, where the ore discharges, the width is only 2 feet. The fire- 
 place follows the retreating arches with a width of 36 inches to the 
 top of the second arch, and then diminishes to 30 at the top of the 
 third, and continues so to within 3 feet 6 inches of the top of the fur- 
 nace. Between each of these arches, on both sides of the furnace, 
 there are openings 6 inches wide, and the whole width of the arch. 
 The aspiration of the blower draws the flame from the fireplace Z 
 to the chamber Z' on the opposite side. The heat of the fireplace 
 is always sufficient to keep it at a dull-red. This construction of 
 the fireplace is far too complicated. These retreating arches are 
 
24 
 
 NOTES ON THE TREATMENT 
 
 liable to be worn by the ore, though not very rapidly, but are quite 
 rapidly affected by the fire and the gases. Exactly the same effect 
 might be brought about by the much simpler construction of having 
 the fireplace entirely outside of the furnace. As originally con- 
 structed the furnace was quite different. It was 24 x 42 inches at 
 the top, and continued for 2 feet at this size, and then gradually 
 widened by a curve upon one side until at a depth of 7 feet from 
 top it was 7 feet 6 inches wide f it continued to the bottom of the 
 fireplace at this width, and then gradually diminished until it was 2 
 feet at the discharge. On the other side, at a depth of 2 feet from 
 the top, it widened to 3 feet, and continued at this width to the top 
 of the arch, then followed the retreating arches down to the bottom 
 of the fireplace, where it was 7 feet, and continued at this size to the 
 discharge. There were only three openings between the arches, and 
 it was found that this was insufficient, and the two small arches 
 above were introduced to increase the heat and attack the ore higher 
 up. The fireplace is so arranged that it receives air which enters 
 at the bottom of the furnace and passes round it through a series of 
 channels Y, so that before entering the fireplace, it is heated by the • 
 walls of the furnace, and thus effects a small saving in fuel, so that 
 the furnace may be said to be in some respects a hot-air furnace. 
 The masonry of the furnace was formerly made 6 feet thick, and it 
 is now made 8 feet. It is braced by ten large wooden beams, which 
 are held together by iron bolts, and as the furnace is double, are 
 strengthened by three uprights of the same size, also clamped to- 
 gether by bolts which pass entirely through the masonry furnace. 
 By the enlargement of the furnace in the centre the ore as it comes 
 to the point where it is to receive the highest temperature is made 
 suddenly to spread out, so that each particle of it comes in contact 
 with the heat, and is in no danger of fusing. The flames are made 
 to traverse through the six openings between the arches, which are 6 
 inches in height, to the chamber on the opposite side of the furnace, 
 into which all the fumes are carried by the draft. 
 
 The cubic contents of the furnace is calculated in such a way as to 
 be capable of containing about 75 tons of ore, bqt as only 1 ton of 
 treated ore is drawn from the bottom of the furnace every hour its 
 capacity is 24 tons in twenty-four hours, so that every ton of ore 
 will remain in the furnace at least three days. When, however, the 
 proportion of very fine ore becomes large, or when the ore is wet, 
 the amount that can be treated in twenty-four hours will be reduced 
 to 12 to 16 tons per day. In the case of a large quantity of fine 
 ore it is proposed to remedy this to some extent by charging wood in 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 25 
 
 small pieces with the ore. This serves to some extent the purpose 
 of keeping the ore open, so as to allow free passage to the heat 
 through the ore, and at the same time creates a source of heat within 
 the charge, so that it will be partially dried, and not pack as it comes 
 down in front of the fireplace. The chamber for the outlet of the 
 vapor is underlaid with a very heavy cast-iron plate, in order to pre- 
 vent any possible condensation or absorption of the vapor at that 
 point. The pipe U' for the outlet of gas is made of cast iron, is 
 18 inches in diameter, 16 feet in height, as it enters the condensation- 
 chambers U. It projects 2 feet from the furnace before it turns 
 down ; at the elbow there is a man-hole for cleaning the pipe. Just 
 above the outlet pipe a cast-iron door is arranged, so as to observe 
 what is passing in the interior of the furnace on the side. Two of the 
 furnaces were built in one structure on account of economy of con- 
 structing and running them. They are charged with f to f medium, 
 and J to J of fine ore. Adobes are never used in these furnaces. 
 
 The charge is introduced by means of an automatic iron wagon, 
 which contains 18 cubic feet of ore, which is equivalent to about a 
 ton when it is moderately heaped. If the ore is very light, how- 
 ever, the amount contained may be somewhat less than this. When 
 the capacity of the furnace is given in tons, that number of carloads 
 is intended to be expressed. The wagon runs upon rails, and is 
 shoved by the charger to the top of the furnace, where the rim of 
 the wagon first strikes a lever attached to a wire rope, which sup- 
 ports the cover of the furnace, which throws off the cover, then 
 a projection on the body of the wagon throws it to one side. The 
 workman then pulls out a pin in the wagon, which discharges the 
 ore into the furnace. As soon as the ore is discharged the weight of 
 the furnace top and lever drives the car back, when the cover drops 
 and closes the furnace. The weight of the charge holds the wagon 
 in place only long enough for the car to empty itself. The work- 
 man shoves the empty car back far enough to be out of the w T ay, 
 covers the furnace top with ashes, and prepares a new charge. 
 
 There are fifteen men breaking and sorting the ore, but one man 
 does the whole charging for both furnaces. The fuel used here and 
 at the Manhattan works is the most ordinary oak brush, which is cut 
 by the company and brought one-quarter of a mile. It costs about $4 
 a load, which is supposed to be equal to about a cord of good wood. 
 The reason for the use of brushwood is, that during the summer an 
 unlimited supply of it can be had at a short distance from the fur- 
 nace, both at the Manhattan works and at Knoxville. It is much 
 
26 
 
 NOTES ON THE TREATMENT 
 
 more easily cut and carried than wood, and it is a cheap fuel in the 
 summer. As this supply fails in the winter, and teaming is more 
 difficult, wood is used at this season. A sheet-iron trough, 3 feet 
 long and 2 feet square, is hung before the fireplace door. This 
 trough is made to fit the fireplace door, which is counterbalanced and 
 rises vertically. The brush is cut to the length of the trough and is 
 packed into it with a pitchfork, the fire-place door is then raised, and 
 the brush shoved in with the fork. This brush is used green, im- 
 mediately after cutting. It flames very readily and makes a quick 
 hot fire. It is charged about every half hour. It takes 2J cords 
 of good wood to do the work of the furnace in twenty-four hours, 
 or two loads of brush, which are considered as weighing one ton. 
 The wood is a mixture of white and live oak, and costs $5 a cord 
 delivered at the furnace. A ton of the brushwood costs $5, and is 
 sufficient to treat about 24 tons of ore. 
 
 The fireman draws the ore that has been treated and takes care of 
 the furnade. The charge is drawn from a long narrow door X in the 
 lower part of the furnace, 15 feet below the level of the fireplace and 
 on the side next to it. The door is raised by a tackle, and is counter- 
 poised. The discharge is effected by means of a hoe and a rake, 
 attached to handles 12 to 14 feet in length made of inch pipe. The 
 discharging car is of iron, and is half the length of the door. It is 
 rolled to one side of the opening and stopped with the handle of 
 the rake, So as to be exactly opposite the end of the door. The ore, 
 which is black, though not cold, is drawn into it from one side of 
 the charging door until the wagon is half full, it is then rolled to 
 the other side and filled from there. By the time the car is full the 
 red-hot ore appears. The car holds one ton of fully treated ore. 
 One load is drawn every hour from each furnace. The furnace is 
 charged above as soon as the charge is drawn. It is done by the 
 same men who also attend to the fire. 
 
 Each furnace requires two men and an aid per shift, so that a 
 single furnace requires six men to treat 24 tons in 24 hours. A 
 double furnace requires only 8 men, who trekt 5 tons in 24 hours. 
 To run four furnaces, standing as in Plate VIII, requires 10 men 
 to treat 100 tons in 24 hours. It therefore requires one day’s 
 labor to treat 4 tons, 6 tons, or 10 tons in 24 hours, showing a 
 gain of twice and a half on all the labor by increasing the number 
 of furnaces to four. One engine and boiler will do all the work of 
 four furnaces, and three or four cords of wood is sufficient both to 
 burn the ore and to keep up steam to run the blowers. 
 
OF MEECUBY IN NOETH C ALIFOENI A . 
 
 27 
 
 The draft in the furnace is produced by four Root’s blowers, E, 
 F, G, H, placed at the extremity of the condensing-chambers. The 
 bottoms of the condensers U are inclined at an angle of from 15° 
 to 20°. They are joined, as is shown in the drawings, at the top by 
 means of curved iron pipes Uk There are sixteen to each furnace 
 as at present constructed. It is proposed, however, to have four 
 sets of eleven, two sets of ten, and six out of line, making twenty- 
 two in all, or eighteen for each, when the four furnaces are finished. * 
 These condensers are 8 feet long, 2 feet 6 inches wide, and 5 feet 
 high at one end and 6 feet at the other. They are set on wooden 
 frames on a cement floor. The first condenser of the series nearest 
 the furnace is set 30 inches, and the last one 37 inches above the 
 ground. Commencing with the next series, the first one farthest 
 from the furnace is 40 inches, and the last one of this series, near- 
 est to the furnace, is 47 inches above the ground. They are made 
 out of three castings, for greater ease of transportation and repair. 
 The top piece is 30 inches in depth all round, is clamped to a 
 projection of the bottom part. The top is made in the shape of a 
 pan, and holds water to the depth of 2 inches. When there is 
 plenty of water it is made to discharge over the top, so as to run 
 down the sides of the condensers, but when water is scarce it simply 
 rests upon the top. At the Manhattan works, which were the 
 first that used the Knox furnace, the condensers are only half 
 the height of those used elsewhere. They have been in constant 
 use for five years, and are nearly worn out, though they may last 
 six months or a year longer. The ore here does not contain much 
 sulphur. These condensers will be replaced by others like those in 
 use here. A very small amount of weak and impure sulphuric acid 
 water commences to condense in the third condenser, but is very 
 abundant in the eighth, and condenses through all the rest. It 
 corrodes the iron-work more or less rapidly. As this action takes 
 place chiefly on the bottom of the condenser, it is cast separate and 
 made several inches thick. As it has been found that the action of 
 the acid water is much less rapid when it is in contact with a small 
 quantity of air, it is allowed to collect for about two inches in the 
 bottom of the last eight condensers, and at this height is discharged 
 from a wooden spout into the mercury trough, and runs to the set- 
 tling vats M, which are 6 by 10 feet in size and 4 feet deep. A very 
 small amount of mercury is carried otf by these streams and collects 
 in this tank. The very small amount so collected shows that the con- 
 densation is very nearly perfect. Mercury commences to collect in 
 
28 
 
 NOTES ON THE TEE ATM ENT 
 
 the first to the eighth condenser, and is discharged at once into a 
 conduit by a small opening in the bottom of the manhole door. It 
 is collected in the iron pots K, which contain about an inch of 
 water, to prevent the mercury from spattering as it falls into the 
 pot. The iron pipe leading from the trough into the mercury pot 
 is shaped like a goose-neck, so that the acid water runs olf above 
 and the mercury collects clear. Tt is bottled from these pots in the 
 * bottling-pot J. 
 
 From the end of each set of condensers a wooden box, E', F', G', 
 H', 1500 feet long and 30 inches square, carries the fumes and 
 smoke away from the furnace. The boards of which it is made are 
 clamped against a wooden frame, on the inside by wooden clamps, on 
 the outside so that it can be taken apart at any time. If nails 
 were used they would very quickly corrode, and the flue, if not 
 clamped, would be likely to fall to pieces at any moment. 300 feet 
 from the furnace, on these long flues, there is a chimney, I, which 
 descends about 15 feet high and 4 feet square. This chimney is filled 
 with, large stones, and water is made to flow over them from a pipe 
 connecting with the reservoir S. This reduces the volume of smoke, 
 which, in this way, is made quite cool at this point. 1000 feet from 
 this point the four conduits are united into one, and is continued to 
 the top of the hill, half a mile off. No mercury and no mercurial 
 soot is found in any part of this conduit, or in the flues leading to it. 
 The object of it is to carry away the smoke, which in the winter- 
 time collects in and around the furnace and annoys the men. It 
 is quite common to see the sickly cattle of the neighborhood collect 
 near the end of this conduit and remain there for half a day at a 
 time, so that they have to be driven from it. 
 
 The engines, W, which do the work of the two blowers are fifteen 
 horse-power, and are to be used to saw all the wood. It takes re- 
 cords of wood for the engines in twenty-four hours. Nothing like 
 fifteen horse-power is required for these blowers, and only four will 
 be required when the six furnaces are built. ' 
 
 All the condensers are cleaned once a week. This is done in the 
 intervals between the charging and discharging by taking off the 
 manhole door and cleaning down the sides with a hoe, but without 
 scraping them. It takes two to three minutes to take out the soot 
 from each condenser. The soot is caught in an iron soot-bucket, 
 which is 2 feet by 3 feet, and 18 inches deep, and is carried on a 
 truck. 
 
 The soot from the first eight condensers only is rich enough to 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 29 
 
 treat ; that collected from the others is too poor to work, and is put 
 back into the furnace. The draft into the condenser is so strong 
 that there is no danger that mercurial vapors will escape, if not more 
 than one condenser is open at a time ; so that to prevent any pos- 
 sible accident they are opened one by one. After one or two have 
 been cleaned the soot is worked up, and then the others are cleaned. 
 By doing the work in this way times can be selected when the fur- 
 nace is neither charging or discharging. The quantity of soot which 
 is produced is very variable, and depends entirely upon how thor- 
 oughly the condensers are cooled, whether the fire is slow or quick, 
 upon the speed of the blower, and also to some extent upon the 
 changes of the weather, so that the quantity deposited in each con- 
 denser will vary at different times. The same is true of the acid 
 water ; and it sometimes happens that when the blower is run at 
 the usual speed, and everything else in the furnace is in the normal 
 condition, but the water has given out, that no acid water will be 
 deposited in the first six or eight condensers, the heat, which is usu- 
 ally absorbed by the evaporation of the water, being so great that 
 they remain perfectly dry. 
 
 It takes from Monday to Friday to clean out and work up all the 
 soot, which is worked in the usual way with lime on an inclined 
 plane. 
 
 On Saturday the conduit and spouts, which get filled with mud, 
 are cleaned, and the flasks are filled with mercury collected during 
 the week. In a charge which gives 150 flasks per week, 40 flasks 
 come from the soot. 
 
 The works are so arranged that two furnaces may be run with 
 one blower, or through one set of condensers ; and this may become 
 necessary when one of the blowers, or one set of the condensers, 
 have to be repaired. It is more difficult to keep the heat up under 
 such circumstances, and a smaller charge has to be put into each 
 furnace. The diminution of capacity will amount to from four to 
 five car-loads of ore in twenty -four hours. The two furnaces, B and 
 C, will generally treat 50 tons of assorted ore in a day. They have 
 been run without repairs since January, 1874, and have produced 
 from 600 to 900 flasks a month, the variation depending upon the 
 richness of the ore. 
 
 It is the intention to make the trial of distilling all the soot in a 
 retort, P. The retort is built, but the trial had not at the time of 
 my visit been made. 
 
 At the Manhattan works the soot is worked up in a retort to 
 
30 
 
 NOTES ON THE TREATMENT 
 
 which a Liebig condenser, like Q, 10 feet long, is attached. The 
 condensing pipe is large enough to hold a barrel of water at one time. 
 
 The experiment is being made here of working the soot mechani- 
 cally. It is mixed with lime and is put into an iron rocker, which 
 has several motions, and in which a rake works backwards and for- 
 wards. A very large part of the mercury in the soot is collected in 
 this way by machine labor withjfit necessarily having any one to 
 tend it. The rocker is run by the steam-engine of the works. 
 This machine is not yet perfected. Working as it did at the time of 
 my visit, some of the mercury separated is afterwards flowered. 
 This is a serious imperfection, but it is expected will be shortly over- 
 come. 
 
 The best men in the works at Knoxville are always selected 
 for the Knox furnace. They work twelve hours, and are paid $40 
 for 30 days and board. If the men have families and occupy the 
 company’s cottages they are allowed $20, as a commutation for 
 board, but they pay $7J per month for rent. 
 
 California Works. 
 
 The California Quicksilver Works also use the Knox furnace. 
 They treat their own ores and produce 26 flasks of 76 J pounds of 
 mercury a week. All the ore passes over a coarse screen, so as to 
 separate the large pieces from the fine and small, which are separated 
 by other screens in the same shute. The larger pieces are broken 
 by hand. The fine ore which is rich enough is made into adobes. 
 One man mixes his dirt and makes 900 a day. The poor fine ore 
 is dressed by hand gigs, and six men treat 10 tons, and reduce it to 
 one-eighth of its former capacity. The enriched ore contains about 
 five per cent of mercury, but a considerable quantity of cinnabar is 
 lost in the tailings, and it is doubtful whether the dressed ore pays 
 for the labor expended upon it. 
 
 The men are paid $40 and board, which equals $2 a day. 
 
 The attempt was made here to treat the soot in the arched chamber 
 7J opposite the fireplace, but the gases of the furnace contained so 
 much free oxygen at this point, that the result was the formation of a 
 large quantity of sulphate of mercury, and the attempt was aban- 
 doned, The works have been managed with so little care that the 
 condensing-chambers, which have been used only 18 months, are so 
 corroded that they will have to be taken out. Long stalactites of 
 acid sulphate of iron are hanging from them in every direction, and 
 the walls in some cases have been entirely eaten through, or are so 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 31 
 
 thin that they could be easily pushed through with the finger. It 
 is the intention to replace the last eight condensers by brick chambers, 
 8 by 10, and 4 \ feet high, with three partitions. When the iron 
 condensers are in good repair the soot is found in from the third to 
 the sixth, but now they are leaking it is found in from the first to 
 the third. The soot is drawn every week from the first six con- 
 densers ; beyond the sixth they are cleaned only once in three months. 
 The soot collected in the first six condensers is about six ordinary 
 sugar barrels per week. The quantity depends upon the sulphur in 
 the ore, its dampness, and other causes. 
 
 Good oak wood is $4J per cord. About two cords in twenty-four 
 hours are burned in the furnace. Brushwood is not as cheap as 
 other wood here, and is consequently not used. There are five men 
 in twenty-four hours about the furnace. At night the fireman and 
 engineer alone run it. 
 
 In discharging the furnace the engineer fills the wagon while the 
 furnaceman draws the charge down. In the daytime there is a 
 superintendent of the work, beside one man making adobes. The 
 miners are required to deliver the ore broken and sorted. There 
 are 100 men working in the mines. The miners are paid $45 a 
 month. The works have been run constantly for 18 months with- 
 out repairs, and have not stopped more than three weeks during the 
 whole of this time for any cause. 
 
 The first Knox furnaces constructed cost between $35,000 and 
 $40,000 each. They were built when wages were high, and labor 
 was difficult to get. The furnaces since constructed have cost about 
 $25,000 each. There are 170,000 brick in the furnace beside the 
 stone, but nearly half the cost of construction is for iron- work. 
 
 Below is a statement of the cost, at the Bedington mine, of treat- 
 ing the ore in the modified Idria furnace and the Knox furnace. 
 
 Cost per ton of reducing ore in the modified Idria furnaces, Nos. 
 1 and 2, at the Bedington mine, Napa County, California, in 1874, 
 
 taking one week’s run, both furnaces : 
 
 5^ cords wood, at $5, $24 50 
 
 36 days. Furnace foreman and his assistant, . . . 86 00 
 
 20 “ Laborers charging furnace, 38 60 
 
 12 “ Laborers discharging furnace, . . . 23 15 
 
 8 “ Laborers working soot, . . . . 14 55 
 
 8 “ Fireman, 14 55 
 
 9000 adobes, at $5 per thousand, 45 00 
 
 Total charge of 200 tons ore in these two furnaces cost . $249 35 
 Average cost per ton for reduction, 1 25 
 
32 
 
 NOTES ON THE TREATMENT 
 
 Cost per ton of reducing ore in the Knox furnace at the Redington 
 mine, furnaces Nos. 3 and 4, taking one week’s run of both furnaces : 
 
 42 days’ labor, engineer, fireman, soot men, etc., . . $81 06 
 
 17| cords wood, at $5, 87 50 
 
 1 gallon oil for lamps, 75 
 
 1 gallon lard oil for engine, 1 20 
 
 v 
 
 Total cost of one week’s ruh, $170 51 
 
 Average cost per day for reducing 50 tons, . . 24 36 
 
 Average cost per ton, ...... 50 
 
 The difference between $1.25, which is the cost of treatment in 
 the modified Idria furnace, and $0.50 the cost of treatment in the 
 Knox furnace, is sufficiently great not only to warrant the use of 
 much poorer ore in the latter furnace, but to call seriously into dis- 
 cussion whether it is not worth while to abandon the old style of 
 furnaces altogether. 
 
 Below is given an estimate of the principal items of expense of 
 building one Knox & Osborn quicksilver furnace, in October, 1874: 
 
 50 to 75 M red brick. 
 
 12 M fire-brick. 
 
 Stone for foundation, walls, etc. 
 
 1 cast-iron lintel, weight, ..... 
 
 . 3000 lbs. 
 
 1 cast-iron draw-door frame, weight, . 
 
 . 650 
 
 it 
 
 1 set draw plates, cast iron, weight, 
 
 . 3500 
 
 a 
 
 18 cast-irOn condensers, complete, weight each, 
 
 . 6500 
 
 It 
 
 1 fire-door and frame, weight, .... 
 
 . 650 
 
 It 
 
 1 flue-chamber plate and door, weight, 
 
 . 1000 
 
 tl 
 
 6 braces, weight, 
 
 . 3000 
 
 it 
 
 1 blower-box, weight, ...... 
 
 . 2500 
 
 tl 
 
 2 pots, etc., weight, ...... 
 
 . 500 
 
 It 
 
 1 set grate-bars, weight, ..... 
 
 . 1200 
 
 tl 
 
 1 blower, 
 
 . $500 
 
 
 Blower pipes, ....... 
 
 . $50 
 
 
 1 retort and condenser, 
 
 . $500 
 
 
 1000 feet wooden flues, cost per running foot, . 
 
 . . . $1 
 
 
 1 engine, with pulleys and shafting, 8x12 cylinder. 
 
 2 boilers (12 x 3). 
 
 35 square timbers, 12 inches b} T 12 inches, and 21 fbet long. 
 
 60 round iron rods, 1£ inch diameter, 23 feet long, 10-inch washers 
 on both ends. 
 
 2 cars, railroad tracks, etc. 
 
 It takes six or eight masons, with their helpers, between three 
 and four months, to build one of these furnaces. The cost might be 
 made less by making more than one-half of the condensers of wood. 
 They might answer even nearer the furnace, if there was a certainty 
 of always having a large supply of water, so that they could be kept 
 constantly wet. 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 33 
 
 Cost of labor would be about . . . t . . . . $5,000 
 
 Cost of building the furnaces 3 and 4, and condensers now in use, . 60,000 
 
 Below is given Knox & Osborn’s estimated cost of a quicksilver 
 furnace, with a capacity of 75 tons, or to work 24 tons every twenty- 
 four hours : 
 
 Cast iron in furnaces, 17,000 lbs., at 6 cts. per lb. 
 
 j 
 
 $1,020 00 
 
 Cast iron in condensers, 91,600 lbs., at 6 cts. per 
 
 lb., . . 
 
 5,496 00 
 
 Work, planing and fitting, .... 
 
 . $90 00 
 
 
 1 conical charging car, 
 
 . 150 00 
 
 
 1 discharging car, ...... 
 
 . 125 00 
 
 
 1 Knox patent suction blower, 
 
 . 400 00 
 
 
 2 boxes borings to caulk condensers, 
 
 . 10 00 
 
 
 3 iron kettles, 120 gallons each, 
 
 . 100 00 
 
 
 Forging bolt ends, and nuts and screwing, 
 
 . 70 00 
 
 945 00 
 
 
 
 Gross amount of foundry bill, 
 
 
 $7,461 00 
 
 20,000 feet lumber, at $20 per M, . 
 
 . 400 00 
 
 
 80,000 red brick, at $10 per M, 
 
 . 800 00 
 
 
 7000 firebrick, at $60 per M, . 
 
 . 420 00 
 
 
 4000 lbs. wrought iron, at $5 per M, 
 
 . 200 00 
 
 
 1 set blocks and fall (watch tackle) 6 inches, 
 
 . 10 00 
 
 
 2 iron sheaves, 1£ x 6 inches, .... 
 
 5 00 
 
 
 4 iron side pulleys, ..... 
 
 2 00 
 
 
 40 feet chain, 1-inch wire, .... 
 
 2 00 
 
 
 10 kegs nails and spikes, at $4.50 per keg, 
 
 . 45 00 
 
 1,884 00 
 
 
 
 Labor, erecting furnace, .... 
 
 . 
 
 $2,000 00 
 
 Boiler and engine, four horse-power, 
 
 
 800 00 
 
 
 
 $12,145 00 
 
 In this estimate nothing is included for grading site, drayage, 
 freight, hauling brick, sand, clay, rock, and timber, to the furnace; 
 nor for the sheds to cover the structures. As different sized fur- 
 naces would require about the same amount, as an approximation, we 
 may say, that $3000 would cover an extreme case, and $1500 would 
 suffice for a very favorable one. In a position where water for a 
 four horse-power can be had, a saving in the first cost is effected, 
 and a greater saving in the current expenses of running. 
 
 There are two sizes of this furnace, a half size, or 12-ton furnace, 
 which easily treats 15 tons, and has, when crowded, worked 17 tons. 
 
 The full size, or 24-ton furnace, crowded in the same way, will 
 work 30 to 34 tons. 
 
 The cost of the half size furnace is about . 
 
 The cost of the three-quarter size furnace is about 
 
 $9,000 
 
 14,000 
 
 Both these sizes have been built within the year 1874, and they 
 are giving perfect satisfaction. 
 
34 
 
 NOTES ON THE TREATMENT 
 
 The following is the estimated cost of running or operating the 
 Knox & Osborn furnace, at the Manhattan works, per day of twenty- 
 four hours, when run by steam power : 
 
 For an average ore for 24 hours, 1£ cords of wood (oak), at $4.50 per 
 
 cord,* . $5 63 
 
 2 men on each watch of twelve houri, or 4 men, $50 per month, and 
 
 board, $2.53 per day, . 10 12 
 
 Oil for light and engine, 50 
 
 Cost per day of reducing 24 tons of ore, ...... $16 25 
 
 Cost per ton, 67f 7 
 
 With regard to these systems of working it may be said that the 
 advantage of the retort system is its economy of installation. It 
 does not appear that there is any gain in yield, though this is claimed 
 for it, while the expenses for fuel and labor are necessarily a maxi- 
 mum, as the amount which can be treated at any given time must 
 be considered as a minimum. The cost of repair is also a maximum, 
 since the iron of the retort is rapidly attacked by the sulphur of 
 the ore, which destroys them, so that a larger number of them must 
 always be kept on hand. The danger of accidents from salivation 
 is at a maximum, even when the precaution of using a blower, as at 
 the Missouri mine, is taken, and there seems to be no good reason 
 why such furnaces should not go out of use altogether. 
 
 There is evidently a limit beyond which the speed of the blowers, 
 which are so characteristic of California practice, cannot be increased. 
 Not only is a large surface necessary to a perfect condensation, but 
 a certain amount of time is quite as indispensable to cool the vola- 
 tilized material, in order to have it condense. If, therefore, the con- 
 densing surface be a maximum, but the velocity of the current too 
 great, it is evident that there will be a loss of mercury, which will 
 be exhausted out of the condensers by the rapidity of the current. 
 The proper speed of the blower will vary at different times, and 
 with the obstruction caused to the passage of the air, by the kind of 
 condensers used, and by the character of the bre charged in the fur- 
 nace. It is evident that in a given furnace, the ore may be charged 
 so fine, that it will pack in such a way, that no speed of the blower 
 will draw the furnace’s gases through it, or so large that a few revo- 
 lutions per minute will be all that will be required. Between these 
 two extremes there is a mean, which can only be determined by the 
 judgment of the person in charge of the furnace, and it is often pre- 
 
 * Of this one cord would lire the furnace, one-quarter the boiler. Ores rich in 
 sulphur will not require over one-half cord of wood in twenty-four hours. 
 
OF MERCURY IN NORTH CALIFORNIA. 
 
 35 
 
 cisely this judgment and skill, which may or may not have been 
 acquired by long experience with a process, which makes an inferior 
 process give good results in one place, and the want of it which 
 makes a good process fail in another. Such examples occur through- 
 out the whole range of metallurgical industry, and not in the metal- 
 lurgy of mercury only. 
 
 The objections to masonry condensers are generally the penetrat- 
 ing power of the mercury, which is so great that it not only impreg- 
 nates the vertical stone or brick walls of the chambers, but infiltrates 
 into the ground to such an extent that on taking up the the founda- 
 tions of some old furnaces at New Almaden, about the year 1863, mer- 
 cury was found to have penetrated through the foundation, and the 
 clay beneath it to the bed rock a depth of 25 to 30 feet, and over 2000 
 flasks were recovered in a single year from the foundations of two 
 furnaces. This loss is now prevented by building the condensing 
 chambers upon double arches, into which plates of iron are built so 
 as to cut off the flow of mercury, and turn it inwards towards an 
 iron basin into which it may be seen to fall in intermittent streams 
 every few minutes. At the time of my visit to New Almaden 
 a large shaft had been dug beside one of the furnaces, and at the 
 depth of 30 feet, it was still profitable to wash the dirt in order to 
 collect the mercury from it. In 1874 sufficient mercury was ob- 
 tained from the brick ore-chamber, and three condensing-chambers 
 of a furnace, and from the dirt around the structure, to more than 
 pay for the new shaft furnace and condensers. For the construction 
 of condensers bricks, though porous, are much preferable to and I 
 think less porous than the sandstone used in the old Idria furnaces 
 at the Redington Works. Whenever repairs in the condensers at 
 Knoxville have been made with brick, they have stood while the 
 sandstone next to the bricks has been worn away. It is evident 
 that what is required is some substance that will be impervious to 
 mercury. Bricks, however, are not so. Every brick or piece of 
 sandstone taken out of a condenser must be considered and treated 
 as a very rich ore of mercury, for whenever broken myriads of 
 globules of metallic mercury are seen scattered through it. Iron is 
 better than brick, in that it does not absorb mercury, but it is rapidly 
 corroded by the sulphuric acid which condenses. Wood is much 
 cheaper, but cannot be used near the furnace on account of the heat. 
 At a certain distance from it, it is more or less rapidly acted on by 
 the condensing sulphuric acid. It seems perfectly practicable to 
 make such a combination of wood and glass that will stand at a 
 
36 
 
 NOTES ON THE TREATMENT 
 
 certain distance from the fireplace, and by placing the condensers 
 made of brick near the furnace, and cutting them up into smaller 
 structures so that they shall not retain the heat, or substituting iron 
 condensers with water cooling arrangements, for them to arrange a 
 good condensing apparatus. Jj3y using, for instance, the Knox con- 
 densers together with the wood and glass arrangement recently 
 patented at Almaden, it would seem that a much better condenser 
 would be made than any now in use.* In any case a few large 
 compartments are not so effective as the same volume distributed 
 among a large number of small ones. What is required to effect a 
 perfect condensation is surface more than volume, and more especi- 
 ally sudden and frequent changes of the direction of the current of 
 volatilized material. With a furnace having only a natural draft 
 this was impracticable, but with a furnace working by an exhaust 
 fan, where obstacles can be introduced within certain limits, it is only 
 necessary to increase the speed of the .fan to get the necessary draft. 
 There is, however, evidently a limit of obstruction which cannot be 
 overstepped. 
 
 There seems to be a very decided advantage in using an artificial 
 fuel when it can be had ; European experience has pronounced de- 
 cidedly in favor of it. At Kew Almaden a series of experiments 
 were made during the years 1873-4 with coke and charcoal, and a 
 mixture of both, but at the time of my visit no definite conclusion 
 had been arrived at. It would seem even advantageous under certain 
 circumstances to mix a certain amount of fuel with the ore, especi- 
 ally when large amounts of fine ore not made into adobes must be 
 charged. It is evident that the fuel which contains the least amount 
 of moisture, if it is not friable, will prevent the formation of a 
 certain quantity of soot, and as artificial fuels generally contain less 
 moisture than natural ones, there would probably be less acid con- 
 densed if they were used. There are places, however, where the 
 cost of making the artificial fuel would more than counterbalance 
 the advantage gained. 
 
 Every system in use, and some which are not, have their sup- 
 porters. When the date of the discovery of these deposits in Cali- 
 fornia is taken into consideration, it must be confessed that more 
 
 * While this paper is going through the press, Mr. C. E. Livermore, of the 
 Eedington mine, writes that they have commenced to use six or eight wooden 
 condensers to each furnace. They are made of seasoned red wood inches thick, 
 and of the same size and shape as the iron ones. They are found to last at least 
 equally as well, and are far cheaper. 
 
OF MERCURY OF NORTH CALIFORNIA. 
 
 37 
 
 rapid strides have been made in the metallargy of quicksilver there 
 than in Europe. There is, however, much to be done. So little is 
 known of what is done, and the prices of the metal have been sub- 
 jected to such great fluctuations, that except in the case of the 
 wealthy companies, there has been but little encouragement to ex- 
 periment. The price of quicksilver in San Francisco in August, 
 1874, was $1.75 per pound. It is now 75 cents, and has been in 
 former years as low as 35 cents. Such prices as these, if they 
 should rule again, would compel almost all the small works to stop. 
 The general feeling is that every advantage must be taken of the 
 present. Under such circumstances the small works must wait to 
 benefit by the experiments and experience of the larger ones, if they 
 are not entirely ruined by the fluctuations in value before they have 
 the opportunity. 
 
 In conclusion, I beg to express my thanks to Messrs. C. E. Liver- 
 more and J. W. Hall, of the Redington mine, and to Mr. R. F. Knox, 
 of the firm of Knox & Osborn, in San Francisco, who have furnished 
 me photographs, drawings, and a large amount of information before 
 and since my return from California, and to the managers of the 
 works generally who were always ready to facilitate the object of my 
 visit. 
 
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Transactions off tin® American Institute of Mining Engineers. Vol. III. 
 
 PLANS AND SECTIONS OF THE MODIFIED IDRIA FURNACES Nos. 1 & 2 OF THE KNOX FURNACES, Nos. 3, 4, B & 6, AT THE REDINGTON MINE, NAPA CO., CALIFORNIA.