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By G. L. F. Powell, L. M. Hogan

Samples of silver and Ag-O alloy, 0.12 wl pet, have been undercooled to a maximum of 250°C by melting in a slag of commercial soda-lime glass. Grain refinement occurred in undercooled silver samples whet the degree of undercooling exceeded a critical value which varied from 153° to 175°C, depending on the melting conditions. In under cooled Ag-0 samples, the grain structure was fine and equiaxed at degrees of undercooling larger than 50oC. The grain refinement in both silver and Ag-0 alloy samples was the result of recrystallization during or immediately following freezing. When the oxygen content was increased, the degree of undercooling at which recrys-tallization occurred decreased. INVESTIGATIONS of the grain structure of strongly undercooled melts of nickel and cobalt1-4 have revealed a change in room-temperature grain size as a function of undercooling. At large degrees of undercooling the grain size was fine, but samples undercooled by smaller amounts exhibited a much coarser grain structure. The reported undercooling at which this grain size transition occurred in nickel varied between 140° and 175'C undercooling. Walker1 attributed this grain size change to an enhanced nuclea-tion rate. Cavitation at a melt-solid interface was con sidered to generate a high-pressure wave. This, in turn, produced nucleation in the liquid as a result of an elevated freezing point increasing the undercooling in the melt. A similar grain size transition was observed in undercooled silver between 133° and 153°C undercooling.5 The grain size transition in undercooled silver was found to be dependent on oxygen con tent. More recently, the authors5 showed that a simila transition occurred in an undercooled Cu-O alloy, =0.08 pet, but not in oxygen-free copper undercooled more than 200°C. The transition was attributed to recrystallization of the solidified grains after freezing; the greater the degree of undercooling, the more complete the recrystallization. In view of this effect of oxygen content on grain size transition, additional undercooling experiments were carried out with silver. This paper reports the results of these studies on silver and Ag-O alloys undercooled more than 50°C EXPERIMENTAL 1) Materials. The silver was supplied by Matthey Garrett Pty., Ltd., as fine granulate, silver mini' mum 99.9 pet, and contained the trace impurities shown in Table I. The silver originated from two different refineries resulting in the difference in impurity content shown in Table I. However, the variation in composition had no discernible effect on the undercooling behavior. Samples of the silver were melted in an open-ended, vertical, cylindrical resistance furnace, wound with Kantha] wire, the temperature of which was adjusted by means of a variable transformer, 2) Melting and Undercooling. Bulk samples of silver were undercooled by preoxidation and removal of oxidized impurities in a glass slag, as previously described,5 but special precautions were necessary to allow comparison between oxygen-free silver and a Ag-O alloy. Samples free of oxygen were prepared by first melting weights of granulate varying from 200 to 400 g in clean vitreous silica crucibles in air for approximately 15 min. A sample was frozen and a complete glass cover formed over the top surface by adding granulated glass rod. The sample was then melted and frozen several times until no oxygen bubbles appeared in the glass slag. Subsequent thermal analysis indicated that the oxygen content was negligible. The glass acted as an efficient barrier to absorption of oxygen from the air. Ag-O alloys were prepared by melting silver in silica crucibles with only a partial cover of glass, so that the top surface of the melt was in contact with air. The silver was held molten in air for several hours at 1000° to 1050°C, in the expectation that the oxygen in solution would reach equilibrium with atmospheric oxygen. At T - 1000°C the equilibrium oxygen content was calculated as 0.12 wt pet O, using Sieverts law and Eq, [l], derived by Mizikar et a!.7 from the data of Sieverts and Hagenacker8 for 1 atm of oxygen:

Jan 1, 1970

By Samuel S. Wyer

THE installation of the gas-producer power-plant in America has been so unusual that all engineers have viewed it with in¬terest; a large majority, however, regard it with a lack of con-fidence and many with positive distrust. Despite the fact that European engineers have usually been less inclined to take the initiative along experimental lines than are Americans, they have, nevertheless, developed the gas-producer plant to a very high state of efficiency to which they were forced by the neces¬sity of economy in fuel-consumption. The gas-producer power-plant is so common in Europe that engineers as well as the general public regard it with the same degree of confidence that is now universally placed in steam¬plants. Gas-engines, both small and large, are in general use there, and central stations, aggregating several thousand horse¬power, are quite numerous. The fact that gas-producer power-plants have received so little attention in America may be attributed to five conditions:-1', ignorance and prejudice; 2, newness of work; 3, in-

Mar 1, 1905

F A. THOMSON, president of the Montana School of Mines, gave an interesting talk on mining schools of the past, present and his ideas of the future before a recent meeting of the Montana Section of the A. I. M. E. He covered the history .of the various mining schools and com- pared the three main types of schools; those attached to or forming part of an endowed college or university such, for example, as' the Columbia School of Mines, the Mining Department of the Massachusetts Institute of Technology and the Mining Department of Stanford University. These resemble in a general way the second class, those attached to the state universities and colleges. The schools of this general type have had varied success.

Jan 1, 1928

By D. L. McElroy

SAFETY in coal mining received especial attention by the public in general and the mining industry in particular during 1940 and early in 1941, owing primarily to the six explosion disasters which occurred last year with a total of 276 fatalities. This was the largest number of fatalities due to explosions in bituminous coal mines since 1928, when 347 lives were so lost. But facilities due to explosions have had a definite decreasing trend since 1907, in spite of bad years such as 1917, 1924, 1932, 1937, and 1940. Although the upswing in explosion fatalities in 1940 is lamented by all, none will admit it represents a trend and it will serve mainly to stimulate ways and means of further reducing these disasters.

Jan 1, 1941

By Howard A. Meyerhoff

AS a source of mineral wealth, the larger islands of the West Indies have never had an enviable reputation. The Spaniards took possession of them in the sixteenth century hopeful that they would yield gold; but it was not long before they knew the rather rigid limitations of Antillean gold production and were seeking-and finding ---richer deposits of the precious metals in Mexico and on the west coast of South America. Although a great deal of wealth changed hands in the West Indian islands in subsequent years, the fact may be laid to the abundance of pirates and privateers and not to the richness of local ore bodies.

Jan 1, 1941

By Ralph Arnold

WITHIN the past three weeks the price of crude oil in the Mid-Continent field has been cut 50 .per cent. Similar action has been taken, or probably, shortly will be taken, in most of the other fields of this country. This cut is very drastic. Is it justified? Some of the causes advanced for the cut are: that it is in line with the industrial downward readjustment now taking place throughout the country, and that there is an over-production of oil, which can best be slowed down by lowering the price of crude. In part, these two reasons are logically advanced, but such underlying causes as the great production- in Mexico have not been prominently brought forward nor the fact that it would be advantageous at this time to fill up the empty storage of many of the consuming companies at a low 'price. In order to properly comprehend the situation let us compare for a moment the production- of oil in the United' States and that in Mexico. Oil in the United States occurs in numerous often widely separated pools, varying in individual area, but each usually relatively extensive, compared to the area or gathering ground from which it is ultimately derived: It occurs in mod-erately porous reservoir rocks under such conditions of pressure, mobility and availability as to preclude its withdrawal except over a period of years-varying from 1 to at least 40 (average, say 15 years, depending on-the pool). One well will usually drain a limited area-2 to 10 acres-so that rate of withdrawal of oil under each owner's property is determined by the owner. - The important point to remember is that no matter how intensive the development, the oil reserves of -the United States cannot be materially exhausted' for at least 20 years, and the total available supply, not including shale oil, will probably require 50 to 75 years, or longer, for its withdrawal, the yearly rate of production decreasing slowly from this time on.

Jan 1, 1921

By H. B. Goodrich

Anthony I?. Lucas died suddenly at his home in Washington, D. C., on Sept. 2, 1921. Captain Lucas, as he was known to us, was born in Dalmatia, Austria, in 1855, of Montenegrin ancestry. He was graduated as an engineer at the Polytechnic of Grate and served in the Austrian Navy as second lieutenant. In 1879, he obtained leave of absence and visited an uncle in the United States. After an extension of this leave of absence, in order to undertake an engineering engagement in the lumber district of Michigan, where he resided, he decided to become an American citizen. He was naturalized in May, 1885. His name was Luchich, but as his uncle had adopted the name of Lucas, which was more easily pronounced by Americans, from his entrance to this country, he used this Anglo-Saxon form. Without knowing this fact, upon first meeting him a person was sometimes surprised to note the rather Germanic pronunciation of the Captain. Although he subsequently revisited Austria with Mrs. Lucas, he made his permanent home at Washington, D. C. His son served with distinction in the A. E. F. during the World War. His activities in this country as a mining engineer were at first in Colorado and later in salt mining at Petit Anse and Belle Isle, La. During his salt investigations, his attention was directed toward the possibility of oil in the Gulf Coast region and in January, 1901, his well, the "Lucas Gusher," on Spindle Top, Tex., started a new era in the oil business and his reputation as discoverer made him famous throughout the world. Captain Lucas became a member of the A. I. M. E. in 1895. During 1914, 1915, 1918, and 1919, he was chairman of the Petroleum and Gas Committee of the Institute and was at all times prominent in Institute affairs. As to the personality of Captain Lucas, the lasting impression is of a courteous hospitable gentleman, genial, affable, obliging, and helpful with his advice br assistance to any colleague. He was sincere, honest, firm against all obstacles, backing his judgment with his own hard work along any course which he had determined to be correct. His value in the engineering world lies mainly in the petroleum industry. In the oil business all wild-catters are pioneers that deserve credit and gratitude upon their success. There are, however, names that particularly stand out in our history. Drake conquered such obstacles as ridicule, lack of finances, and started the oil business. In 1901, Captain Lucas had the conviction that Spindle Top, a dome rising about 12 ft. above the coastal prairie south of Beaumont, Tex., contained commercial oil. He was scoffed at by practical oil men of the East. Noted geologists

Jan 1, 1921

Aamot, Olav Crone, Chem. Engr., Elektrokemisk Raadhusgt..23, Oslo. Norway. '29 Abadilla, Quirico A., Dir., Bureau of Mines Manila, P. I. '3S Abbott, Clarence E., V.P., Charge of Raw Materials, Tennessee Coal, Iron & R.R. Co., 1242 Brown-Marx Bldg., Birmingham, Ala. '04 Abel, Raymond L.. Prof., Dept. of Pet. Refin., Univ. of Pittsburgh Pittsburgh, Pa. '2S Abel, Walter D., Div. of Corporations Los Angeles, Calif. '32 Abele, Louis T., U. S. Corps of Engrs 7211 Glen Oak Ave., Baltimore. Md. '31 Abel], Leo M., Research Met., Mount Morgan Ltd Mount Morgan, Queens.. Australia. '31 Abenius, Hakan V c/o Falu Gruva, Falun, Sweden. '37 Abernathy, G. E., Geol., Kansas State Geol. Survey Pittsburg, Kan. 3S Aborn. Robert H., Asst. Met., Research Lab., U. S. Steel Corp., Lincoln Highway, Kearny, N. J. '19 Abrams, Charles Jackson 1624 17th St., Denver, Colo. '3 t. Abstein. Henry T., Engr. & Mgr., Profile-Tamarack Mines CoYellow Pine, Idaho. '27 Acker, E. O'C., Met L28 East Washington Lane, Germantown, Philadelphia, Pa. '86 Ackerman, D. E., Met., Assoc. Prof. of Met., Purdue Univ Lafayette, Ind. '35 Ackerman, E. Dumont, Sub-Surface Geol., Temblador Camp, Standard Oil Co. of Venezuela, Caripito, Venezuela. '3S Ackerman, George F.,. Div. Foreman. The Fresnillo Co Fresnillo, Zac., Mexico. '36 Adami, A. F., V.P. & Prof. of Min. Engrg., Montana School of Mines Butte, Mont. '19 Adami, Charles J., Min. Engr 99 S. Downing St., Denver. Colo. '12 Adams, Army, Cons. Engr 714 W. Main St., Grass Valley, Calif. .'37 Adams, Clyde B.. Geol.. Socony-Vacuum Oil Co., Inc 26 Broadway, New York, N. Y. '39 Adams, Ernest C., 6th Engrs Fort MacIntosh, Laredo, Tex. '35 Adams, F. J., Gen'l Agent, Gulf Production & Pipe Line Cos Fort Worth, 'lox. '29 Adams, F. S., Supt., Power Dept., Anaconda Copper Min. CoAnaconda, Mont. '37 ADAMS. FRANK DAWSON, Hon. Mbr., 1913; Logan Prof. of Geology and Dean, Faculty of Applied Science. McGill Univ., Montreal, Que., Canada. '13 Adams, Gale L., Supervisor, Process & Dev. Lab., General Pet. Corp. of California, Higgins Bldg., Los Angeles, Calif. '18

Jan 1, 1939

By John J. Theiler

Early in 1963, the Inspiration Consolidated Copper Co., at Inspiration, Ariz., began a program to make automatic the lubrication of several critical points on their KW Dart 37SL haulage trucks. Prior to installation of the automatic lubrication system, all the haulage trucks were serviced by hand every three shifts. Now, with automatic lubrication, the service period has been extended to four shifts. What are the principal benefits to be expected from such a system? 1) Uninterrupted production; 2) extended machinery life; 3) good housekeeping; 4) lower maintenance costs. Of these points, the most important to truck maintenance are extended component life and lower maintenance costs.

Jan 5, 1965

SOUTHERN CALIFORNIA LOCAL SECTION Executive Committee THEODORE B. COMSTOCK, Chairman SEELEY W. MUDD, Vice-Chairman FREDERICK J. H. MERRILL, Secretary-Treasurer, 300 Germain Building, Los Angeles, Cal. C. COLCOCK JONES FRANK ROBBINS The February meeting of the Southern California Local Section-was held at the headquarters in the Chamber of Mines and Oil of. Los Angeles on Feb. 17, C. Colcock Jones presiding. Fourteen members were present. The subject announced was Ore Sampling. W. M. Watts opened the discussion by a general outline of the important points to be covered, in sampling a mine and the methods to be used in the various stages of the work. All the members present successively contributed details from their personal experience. The March meeting of the Section was held at its headquarters on Mar. 15. Twelve members were present, with Dr. Theodore B. Comstock in the Chair. The subject announced was Secondary Enrichment and all present took part in the discussion, Frank Robbins contributing a short paper on some observations in Central America. The next meeting will be held on Apr. 14, at which time the subject of Mine Accounting will be discussed. F. J., H. MERRILL, Secretary.

Jan 5, 1914

By W. A. Eardley

FIFTEEN years ago the world's deepest oil well penetrated the earth about 7300 ft. That depth has now been more than doubled. Why has such deep drilling become necessary and how has it become possible? Three factors have had an important bearing: (1) Depletion of shallow zones, making it necessary to search for deeper producing measures. (2) The perfection of prospecting methods, which have been success- fully used to locate favorable buried structures, many at great depth. (3) Improvement in the quality of steels used for drilling.

Jan 1, 1940

By R. A. Sharma, F. D. Richardson

Manganese oxide acitivities and sulfide capacities have been measured at 1650°C in mixtures of MnO + A1203 and MnO + SiO2 - Al2O3. Sulfide capacities have also been measured at 165O0C for melts of MnO + SiO2, MgO + SiO2, MgO + SiO2 + Al2O3, MgO + MnO + SiO2, and SiO2 + Al2O3 and for crystalline CaO. The activity coefficients of the sulfides of manganese and magnesium have been derived where possible. It looks as though the activity coefficients of sulfides are greatest at compositions where the free energies of formation of the silicate mixtures have their maximum negative values. The amphoteric nature of alumina is reflected in the results for the binaries and ternaries in which it is present with silica. The limiting solubility of CaS in CaO at 1650°C is 6.3 x 10-4 mole fraction. THE activities of manganese oxide have been measured in a variety of silicate and aluminate melts by use of the equilibrium (MnO)slag = [Mn]pt .½O2 [l] and the experimental techniques described previously.' Sulfide capacities (CS = wt pct S (PO2/PS2)½) have also been determined in a series of melts, by use of an established method2 which exploits the equilibrium (O°) + ½S2 = (S") . ½O2 [2] If CS and the activity of a metal oxide are known in a melt, the activity coefficient of the metal sulfide can be calculated by use of the equilibrium constant K, for the pure phase reaction MO i ½S2 = MS + ½O2 [3] The activity coefficient of the sulfide is then given by the equation

Jan 1, 1965

By Gifford White

Considerable attention has been directed in recent years to methods of electric prospecting other than the conventional direct-current techniques. It has been extensively recognized that electrical data of a more general nature than that possible by direct-current methods might be useful in geophysical studies. To this end, a number of different types of electric currents have been employed, such as single-frequency alternating currents, square-topped periodic current waves,4 periodic surges of a less specific nature,s and suddenly applied direct current.1,2 Yet, to the author's knowledge, little analysis of these different types of driving currents has been made from the standpoint of network theory to determine just what typc of currents would give the most useful data, and, most important of all, to determine the relation of the data taken by one method to those of another. Without touching on the actual theoretical problem of how currents flow in the earth under specified boundary conditions, some very useful information can be obtained from the study of the fundamental integral equations of electrical networks, throwing light on the problem not ordinarily appreciated by the field worker. Some manipulation of the standard network equations will be made, with the sole purpose in mind of developing expressions leading to practical results. Suppose that four points in the earth have been located and it is wished to obtain the most useful type of electrical data by inserting current into two of them and measuring the potential developed between the other two. The first problem that arises is that of which pair of the four shall be chosen as current grounds. In the direct-current case, where only steady potentials are measured, the selection is of little consequence, but as soon as currents varying with time are used at the current grounds, a new effeet arises. The fact that a varying current is flowing in the current-carrying conductor between the current grounds means that magnetic and electric fields varying with time will be produced

Jan 1, 1940

By Gifford White

Considerable attention has been directed in recent years to methods of electric prospecting other than the conventional direct-current techniques. It has been extensively recognized that electrical data of a more general nature than that possible by direct-current methods might be useful in geophysical studies. To this end, a number of different types of electric currents have been employed, such as single-frequency alternating currents, square-topped periodic current waves,4 periodic surges of a less specific nature,s and suddenly applied direct current.1,2 Yet, to the author's knowledge, little analysis of these different types of driving currents has been made from the standpoint of network theory to determine just what typc of currents would give the most useful data, and, most important of all, to determine the relation of the data taken by one method to those of another. Without touching on the actual theoretical problem of how currents flow in the earth under specified boundary conditions, some very useful information can be obtained from the study of the fundamental integral equations of electrical networks, throwing light on the problem not ordinarily appreciated by the field worker. Some manipulation of the standard network equations will be made, with the sole purpose in mind of developing expressions leading to practical results. Suppose that four points in the earth have been located and it is wished to obtain the most useful type of electrical data by inserting current into two of them and measuring the potential developed between the other two. The first problem that arises is that of which pair of the four shall be chosen as current grounds. In the direct-current case, where only steady potentials are measured, the selection is of little consequence, but as soon as currents varying with time are used at the current grounds, a new effeet arises. The fact that a varying current is flowing in the current-carrying conductor between the current grounds means that magnetic and electric fields varying with time will be produced

Jan 1, 1940

By Gifford White

CONSIDERABLE attention has been directed in recent years to methods of electric prospecting other than the conventional direct-current tech-niques. It has been extensively recognized that electrical data of a more general nature than that possible by direct-current methods might be useful in geophysical studies. To this end, a number of different types of electric currents have been employed, such as single-frequency alter-nating currents, square-topped periodic current waves,4 periodic surges of a less specific nature,8 and suddenly applied direct current.1,2 Yet, to the author's knowledge, little analysis of these different types of driving currents has been made from the standpoint of network theory to determine just what type of currents would give the most useful data, and, most important of all, to determine the relation of the data taken by one method to those of another. Without touching on the actual theoretical problem of how currents flow in the earth under specified boundary conditions, some very useful information can be obtained from the study of the fundamental integral equations of electrical networks, throwing light on the problem not ordinarily appreciated by the field worker. Some manipulation of the standard network equations will be made, with the sole purpose in mind of developing expressions leading to practical results. Suppose that four points in the earth have been located and it is wished to obtain the most useful type of electrical data by inserting current into two of them and measuring the potential developed between the other two. The first problem that arises is that of which pair of the four shall be chosen as current grounds. In the direct-current case, where only steady potentials are measured, the selection is of little consequence, but as soon as currents varying with time are used at the current grounds, a new effect arises. The fact that a varying current is flowing in the current-carrying conductor between the current grounds means that magnetic and electric fields varying with time will be produced

Jan 1, 1940

By B. M. Burchfiel

CALIFORNIA possesses such an abundance of ceramic materials other than clays, that she is quite independent of other states and foreign countries so far as these materials are concerned. Certain users import some feldspar, silica, and allied minerals, but they do so from choice and not necessity. Production is largely for home consumption, so the total volume of ceramic materials produced is comparatively small. Many small deposits of the materials here under discussion are worked by individuals, and their output sold to individual grinding companies or users. The data given here shall be confined to the larger deposits and developments because they give a truer picture of typical deposits, operations, and materials.

Jan 1, 1936

By G. B. Gould, F. M. Gibson

IN DECEMBER, 1934, the joint Committee on Fuel Values, of the American Institute of Minim and Metallurgical Engineers and the American Society of Mechanical Engineers, submitted a preliminary report, which briefly stated its conclusion that it was not possible to devise any formula for the valuation of coal, based upon the various physical and chemical properties, that would be generally applicable. That report also listed those chemical and physical properties of coal that are generally recognized to have some effect on its use in steam plants, and those physical characteristics of steam plants which affect, in one way or another the relative importance of the properties of coal used in them. Since then, the Committee has considered and discussed in greater detail the interrelationship of the properties of coal and plant characteristics. The conclusions of the Committee are summarized below, with certain recommendations regarding engineering procedure, which will promote the collection of more easily correlated observations with respect to this subject, and thus advance more rapidly the accumulation of data capable of general application.

Jan 1, 1936

By C. W. Hazelett

This paper is a resume of some of the accomplishments in direct rolling of strip from molten metal, and a description of some experimental developments in recent years. In all the early developmental work, we used a pair of rolls with a bath of metal between them, maintained by flanges or plates at the ends of the rolls. These flanges produced an excess cooling of the metal and built up enormous pressures at this point as the metal went through the bight of the rolls. Many means were tried for compensating for this excess cooling, such as thickening the strip at the edges, heating the end dams directly or by flowing more of the molten metal against them, leaving an open crotch below the end dam and above the bight of the roll, where the excessive pressures built up could be relieved by some of the metal squeezing out at this point, and so forth. All of these helped somewhat to solve the problem, so that very large heats of many metals melting up to 200°F., having commercially uniform gauges, could be rolled up to 24 in. in width. The rolls were made by mounting heavy rings on heavy shafts, and pressures up to 75,000 lb. per inch in width were used. Cooling of the rolls was generally done by spraying water on the outside surface of the rolls that came in contact with the molten metal. Roll life was commercial with brass, barely satisfactory with copper, and totally impractical with steels. The greatest difficulty encountered in all this work was caused by lack of uniformity in the product, owing to a folding action in the mill. Those who are familiar with the operation of a rolling mill know that a bar entering a mill moves at a lower speed than the peripheral speed of the roll. However, the metal solidifying from a bath in a direct rolling mill is cast at exactly the peripheral speed of the roll. This results in irregular folding of the metal, some irregular remelting of the previously solidified sections, and it is difficult, if not impossible, in some cases to exert enough pressure to weld these folded sections sufficiently into a sound product. In addition to this melange of solid, semisolid and liquid metal in the bath, we know that pressure near the freezing point of any alloy in which the constituents have different melting points—and I believe all of them have—causes the lower-melling-point constituent to be squeezed back until it becomes cold enough to solidify and go through the mill. This segregates all alloys, the segregation increasing with the pressures and the freezing ranges of the metals. Add to these problems the excessive roll-maintenance costs with high-melting-point metals and then, the greatest difficulty of all, the vanity of homo sapiens where a matter of possibly large importance is being considered, and the problems seemed almost insuperable. It was long ago obvious to me that something much more than the size of a corporation's money and self-assuradce was necessary if this process was to be made commercial. I should like to show you first the performance of the only mill we ever really designed and built, to see what might be done with a well constructed mill. We accomplished something new in history with this prccess, first, by producing at Scovill Manufacturing Co. coils of brass

Jan 1, 1945

By N. J. Sather

A detailed description is given of Bunker Hill's concentration process employed at the company's lead-zinc property in the Coeur d'Alene district, Idaho. The plant is equipped to process 3000 tpd of Pb-Zn ore. The history of the Bunker Hill mine dates back to Aug. 26, 1885, when Noah S. Kellogg found the outcrop of the Bunker Hill orebody on the hillside of Milo Gulch above the present town of Wardner, Idaho. A small concentrator was erected in 1886, and before the railroad came, the mine output was transported by mule teams to the head of navigation on Coeur d'Alene Lake. After ten years of production, an interest was purchased in the Tacoma smelter at Tacoma, Wash., to which the entire output was shipped. In 1916 and 1917, a modern lead smelting plant and refinery was erected, and a modern electrolytic zinc reduction plant was built in 1927-1928 by the Sullivan Mining Co. which was 50 pct owned (and now totally owned) by the Bunker Hill Co. The first concentrator, a 100-tpd capacity plant, was built in 1886 near the Reed Tunnel in Wardner. The treatment consisted simply of crushing ore to 2 in. and then to 1/2 in. through rolls in closed circuit with a bucket elevator and trommel screen. The undersize was further sized in trommels to 10 mm and 3 mm. Oversize from the latter was treated in Hartz jigs. The 3 mm undersize was classified in crude hydraulic classifiers furnishing sands to sand jigs, the overflow being dewatered in a long V tank which supplied sands to a Cornish buddle and to Frue vanners. The concentrates were of excellent grade, old records showing assays of 69 pct lead and 29 oz. of silver per ton. Tailings were high inasmuch as the provision for treating the slimes was inadequate. Since the erection of the first mill, the Bunker Hill plant has gone through many changes and improvements. In succeeding years, the flowsheet was enlarged somewhat with Huntington and Chilean mills, vanners, tables, ball mills, and flotation cells being progressively added. In the transition period to the present day practice, the object was not only to improve the equipment for better mechanical performance, but to add new equipment whenever practicable so as to improve both grade and recovery of the product at a lower cost. For the modern plant and flow-sheet, see Figs. 1 and 2. The history of flotation at Bunker Hill dates back to 1913 when experimental work was done in a cell in which the pulp was circulated through a centrifugal pump set outside the cell and discharged against a baffle in the cell. The cell was built with a spitzkasten, and the quiet zone in the latter tended to let the froth break down before it got to the overflow weir. To remedy this situation, a belt drag with light metal flights was arranged for drawing off the froth over a ramp in each cell. Recovery of lead was not as high as present day practice, but was so much better than the vanners that the cells were multiplied gradually to eight cell units. The mill men called them mud hens. Flow between the cells was controlled by a weir, which determined the pulp level in each cell. These early machines were called Bunker Hill machines. The tailings were later treated in pneumatic scavenger flotation machines in a series, producing concentrates for retreatment in the Bunker Hill cleaners as well as the final tailings. This system of flotation served with minor changes until the Fahrenwald machine was developed at Bunker Hill during the period from 1921 to 1925. In 1925, the Fahrenwald flotation machine gradually replaced the Bunker Hill machine, although the Hearing pneumatic scavengers for retreatment of the tailings from the Fahrenwald machines were retained in the lead section until 1928. The use of the Hearing pneumatic machine for cleaning the rougher concentrates was begun in 1924. In 1941, plans were made for remodeling and modernizing the concentrator, the goal being a modern concentrator employing the latest equipment and milling practices. The old wooden building was to be replaced by a steel and concrete structure. Shortly after preliminary work got under way, the United States entered World War II and the demands for metals increased. To meet this requirement, the management decided to increase the capacity of the concentrator to 1800 tpd. This was accomplished in record time by the construction and operation of a sink-float plant. Installation of this plant was the first step in the general plan for modernization. In 1947 the concentrator (including the sink-float plant) was enlarged to handle 3000 tpd. Milling operations today are at the rate of 2300 tpd, five days per week. During 1959, 453,000 tons of ore was beneficiated. The Bunker Hill concentrator is in three sections: the crushing plant, a 3000-ton capacity storage bin, and the concentrator building. The crushing plant is of wood design with a gunnite coating on the exterior.

Jan 1, 1961

[A Aall, Christian H., M49 A Dir, Smelt & Ref, Am. Metal Climax, Inc., 1270 Ave. of the Americas, New York 20, N. Y. Aaroe, S. L., A54 A VP, W. S. Tyler Co. of Canada Ltd., P. O. Box 100, St. Catharines, Ont., Canada Abalos, Teodulo Q., J57 A Prod Frmn, Lepanto Cons. Mining Co., Lepanto, Mt. Province, Philippines Abbitt, James M., A54 770 Sole Blvd., Bartow, Fla. Abdullah, M. Y., J53 Dept. of Mines Res. Div., P. O. Box 1016 Tiger Lane,-Ipoh Peram, Malaya Abel, John F., Jr., J53 F Mine Engr, Thompson Creek Coal & Coke, Carbondale, Colo. Abell, Leo M., M31 B Const Supt, Phelps Dodge Corp., Morenci, Ariz. Abendroth, H. E., A57 Mangore Australia Pty. Ltd., 901 Hay St., Perth, W. Aust.,, Australia Abenius, Hakan V., M52 Falun, Sweden]

Jan 1, 1961