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Discussion of the paper of O. P. Hood, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October, 1914, pp. 2607 to 2611. R. V. Norris, Wilkes-Barre, Pa.-I have had a little experience with gasoline locomotives and I want to indorse very strongly Mr. Hood's point with regard to the danger of carbon monoxide poisoning. I think .the terrible danger is not fully realized. I was foolish enough some time ago, in investigating a gasoline locomotive, to attempt to walk out of the mine entry behind it, and for several days I felt very seriously the carbon monoxide effects. The use of gasoline locomotives ought to be confined to mine entries where there is a very large amount of air. One of the grave dangers is their great convenience and the temptation to run them into chambers for just a few moments to get a car or two. GEORGE S. RICE, Pittsburgh, Pa.-Apparently one of the great dangers is in the style of the gasoline engine. When my attention was. first directed to the type of gasoline locomotives which I saw in the foreign mines-France, Belgium, and Germany, I was most favorably impressed with them, and they have given no trouble on account of fumes, so far as I could learn. Large numbers of them were being used, but all were of small capacity, and of a kind in which the speed control is by a governor of the hit-or-miss type, the engine running continuously. Their power capacity was very low, if I remember correctly it was not over 4 or 5 h.p., but they were used under favorable conditions where the grades in the mines were slight, since the entries or tunnels bad a slight grade in favor of-the load, making about the same pull for the empties against the grade as for the load with the grade. I understand the hit-or-miss valve arrangement enables a setting that will give more perfect combustion than can be insured with the valve controlled by the operating man, as in the automobile type of valve and engine used in this country. Apparently the European type of locomotive does not have the capacity to permit use under the conditions existing in this country, where most of our entries or tunnels have variable grades and long heavy trips of mine cars are used.

Jan 4, 1915

The Institute has no available copies of Bulletin No. 7, January, 1906, and Bulletin No. 105, September, 191.5. The sum of 30.50 per copy will be paid for these Bulletins.

Jan 6, 1917

By Alexander Knoll, Dwight L. Baker

THIS paper is a report on work undertaken to investigate the results and conclusions of Ravitz and Porter1,2. that galena freed of surface oxidation products and lead carbonate ("clean" galena) is water-repellent, and that the action of xanthates in flotation is the action of a cleansing agent, enabling oxidized galena particles to expose a pure lead sulphide, water-repellent surface. The apparatus, in construction and use, was essentially that of Ravitz and Porter. The only significant modification introduced by the present authors was the substitution of a three-necked flask for the flotation cell as the "reaction vessel." Our procedure was to place 50 grams of freshly ground, minus 200-mesh galena in the reaction vessel, sweep out all molecular oxygen from the system with oxygen-free nitrogen, and proceed to wash the galena surface free of its oxidation products with repeated small portions of (I) ammonium acetate (500 c.c. of water, 200 grams of ammonium acetate) or (2) ammonium chloride, hydrochloric acid (2 liters containing 200 grams of ammonium chloride and 25 c.c. of 1.18 sp. gr. hydro chloric acid). The galena was next washed with many 100-c.c. portions of oxygen-free, distilled water. The galena was finally considered free of soluble salts when wash water that had been in contact with the mineral for at least 48 hr.* gave negative tests for: (I) lead ion with sulphide; (2) chloride with silver ion; (3) acetate with cuprous chloride, sodium chloride; and (4) ammonium ion with Nessler's reagent. Next 500 c.c. of potassium ethyl xanthate solution, free of dissolved oxygen, was run onto the "clean" galena particles. For this system there were determined: I. The wetting properties of the clean galena particles by shaking the reaction flask and noting the degree of mineral collection at the liquid-air interface. This was, of course, simply a qualitative test, but it proved adequate for our purpose. 2. The removal of xanthate ion from the potassium xanthate solution on being shaken with the "cleansed" mineral. Xanthate concentrations were determined by iodine titration according to the methods of Taylor and Knoll.3 3. The pH of the xanthate solution after having been shaken with the "cleansed" galena. The pH was determined colorimetrically.4 The results of five experiments of the type mentioned above are given in Table I.

Jan 1, 1941

Discussion of the paper of H. M. WARREN, A. S. BIESECEKER and E. J. POWELL, presented at the New York meeting, February, 1916, and printed in Bulletin No. 110, February, 1916, pp. 181 to 193. R.. V. NORRIS, Wilkes-Barre, Pa.-For many years the power requirements of breakers designed in the Anthracite. Region have been based on calculations made from indicator diagrams taken during operation, with various sections of machinery idle; these, while giving reasonably accurate figures, gave no intimation of the peak loads which have been shown so clearly in the paper. The high-speed flywheel for breaker rolls is new and shows a remarkable saving in peak power required, besides eliminating the stalling of the rolls from overload. The figures given are so far in advance of anything previously published that they will undoubtedly be used as a basis for future breaker design. It is to be hoped that the authors will continue this investigation and extend their paper by a description of the motors found best suited for this work. WILLIAM KENT, Montclair, N. J.-I notice on p. 187 reference is made to one of the difficulties being the starting torque, and it is proposed to use roller or ball bearings in order to decrease the high starting torque. I suggest that. before the roller or ball bearings are put in, an investigation be made as to the amount of the starting torque, as shown by wattmeter measurements and as to what the starting torque ought to be, theoretically, according to the energy formula; that is, how much starting torque is required to accelerate the rotating mass in a given number of seconds up to full speed. Having secured this information it may be found the amount to be saved by roller bearings is not very great. If it appears that roller bearings will not greatly decrease the starting torque, the next thing to be done is to have a special design of motor in which there is a field that can be made very strong at the start, by the use of extra poles or other means, and the next thing that may be done is to increase the speed from 10,000 r.p.m. to 25,000, which can be done with wire-wound flywheels, especially if the wires are made of vanadium steel.

Jan 5, 1916

By Hiroshi Oikawa, A. G. Guy

Recent experimental evidence has shown that it is often incorrect to neglect the reactions occurring at an interface with respect to the diffusion reactions. By introducing reaction-rate constants and k for the transfer of components 1 and 2 between the a and b phases, a phenomenological description has been devised for the coupled processes of diffusion and in-terfacial reaction. An illustrative example has been analyzed with the aid of a suitable computer program. The results indicate that for kab values on the order of 10'1 cm per sec and Ð values of about 10¯10 sq cm per sec, the interfacial reactions are significant during the first 10 2 to l0 6 sec of a diffusion experiment. Among the observable effects of the interfacial reactions in this case appear to be the burying Kirkendall markers and an anomaly in the initial shifting of these markers. THE study of diffusion between two phases is especially important because of its direct connection to phase transformations. For example, the transformation of austenite to ferrite involves diffusion in the a and ý phases and also an interfacial reaction (trans formation) at the a/? interface. If ferrite and aus-tenite are the two members in a diffusion couple, the same two reactions occur during the diffusion process. The numerical values obtained for the diffusion coefficients and interfacial-reaction constants from diffusion experiments can then be employed to predict phase-transformation behavior. Refinement of the calculations of phase transformation is also suggested by the present method for treating two-phase diffusion. In the recent paper by Nolfi et al.' only the solute com ponent is considered in the interfacial reaction accompanying a phase transformation. The present analysis demonstrates that both components must be considered. It is generally recognized that reactions of some kind must occur at the interface in a two-phase diffusion couple, but usually it is assumed that the interface reaction occurs so rapidly that its effect on the overall process is unobservable because the slower diffusion process determines the kinetics of the process. However, Seith and Heumann 2 pointed out that effects of the interfacial reaction should always occur in the early stages of diffusion, and recently Eifert et al. 3 have shown that interfacial reactions influence the composition and motion of the interface in a/ß Al-Cu diffusion couples during the entire course of prolonged, high-temperature treatments. A general procedure for handling the combined processes of interfacial reaction and diffusion in a binary, two-phase system is to introduce kinetic coefficients for the interface reactions and to develop the system of equations governing the interlinked processes of diffusion and interface reaction. The resulting equations, although not amenable to solution in closed form, can be usefully manipulated by a digital computer. INTERFACIAL REACTIONS IN TWO-PHASE DIFFUSION Consider the general case of diffusion between two solid solutions, a and ß, which are adjacent phases in a binary system, Fig. 1. Two semiinfinite bars having compositions c1 and c0ß are jointed at x = 0. If concentrations are expressed in volume fraction,4

Jan 1, 1970

By Charles Catlett

(Chattanooga Meeting, October, 1M.) THE terms " developed " and " undeveloped " are necessarily relative and cover a wide range; but the latter is here applied to cases in which the information at hand falls short of a clear demonstration of values, and conclusions must be reached from a study of the geological conditions of the particular deposit, interpreted in the light of similar and closely related deposits. Such an inquiry might be characterized as an effort to reach reliable conclusions from insufficient data. But the engineer engaged in commercial work finds himself often face to face with apparently such problems; and while he may realize with regret that a small amount of intelligent development would add enormously to the value of his conclusions, he is compelled to recognize the demand of a business situation for a prompt decision as the basis of immediate action. In a case within my knowledge, the question involved was the purchase of 50,000 acres of coal-land, and 10 days was the limit within which this question must be decided. Of course, it was impossible to make a satisfactory examination within that time; but the 'instructions were "to make the most complete examination and the most positive recommendation possible." Such instructions are often given; for, no matter how much time an investor may have, he is likely to put of his decision until the last moment, and then discover that he needs more light and advice. It does not follow that engineers, after full explanation and mutual understanding of the situation, should decline to undertake examinations thus limited. In the case just mentioned, while only the broadest view was possible, half the time available was sufficient to show that the property was a good purchase. The timber alone was subsequently resold for more than the entire purchase-price of the

Mar 1, 1909

By William R. Barton

It is generally conceded as axiomatic that the aggregate producer and the average urban resident have mutually incompatible goals. The producer wants to be near his mass market and the average resident wants him as far away as possible. The traditional economic decision to mine local material to avoid transportation costs is increasingly challenged by zoning and planning bodies and by citizens' groups. This conflict generated much written and spoken word and offered opportunity for great flights of rhetoric. The pressure on the producer also has forced re¬appraisal of the need for the classic confrontation with indications that much of the conflict is more apparent than substantive. In New England several factors combine to increase complexity of the siting problem. It is a region of high land values and population density. Due to the proximity of metropolitan areas, even rural communities have experienced a prolif¬eration of environmental groups with concomitant enthusiastic regional planning and critical watch over land use. In New England where there is little public understanding of the necessity for, and the realities of, mineral production a sophisticated approach to aggregate production site location is required.

Jan 1, 1975

Discussion of the paper of O. P. Hood, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October, 1914, pp. 2607 to 2611. R. V. Norris, Wilkes-Barre, Pa.-I have had a little experience with gasoline locomotives and I want to indorse very strongly Mr. Hood's point with regard to the danger of carbon monoxide poisoning. I think .the terrible danger is not fully realized. I was foolish enough some time ago, in investigating a gasoline locomotive, to attempt to walk out of the mine entry behind it, and for several days I felt very seriously the carbon monoxide effects. The use of gasoline locomotives ought to be confined to mine entries where there is a very large amount of air. One of the grave dangers is their great convenience and the temptation to run them into chambers for just a few moments to get a car or two. GEORGE S. RICE, Pittsburgh, Pa.-Apparently one of the great dangers is in the style of the gasoline engine. When my attention was. first directed to the type of gasoline locomotives which I saw in the foreign mines-France, Belgium, and Germany, I was most favorably impressed with them, and they have given no trouble on account of fumes, so far as I could learn. Large numbers of them were being used, but all were of small capacity, and of a kind in which the speed control is by a governor of the hit-or-miss type, the engine running continuously. Their power capacity was very low, if I remember correctly it was not over 4 or 5 h.p., but they were used under favorable conditions where the grades in the mines were slight, since the entries or tunnels bad a slight grade in favor of-the load, making about the same pull for the empties against the grade as for the load with the grade. I understand the hit-or-miss valve arrangement enables a setting that will give more perfect combustion than can be insured with the valve controlled by the operating man, as in the automobile type of valve and engine used in this country. Apparently the European type of locomotive does not have the capacity to permit use under the conditions existing in this country, where most of our entries or tunnels have variable grades and long heavy trips of mine cars are used.

Jan 4, 1915

By Frank T. Sisco

The discovery of phosphorous is usually credited to the German alchemist Brand, in 1669, and the element was rediscovered the next year by Boyle in England. IT was more than 100 years later, however, before its presence was detected in high-carbon iron produced in early blast furnaces. In 1781 the German chemist Meyer published the results of his investigation on the ?white earth? that he had found in cast iron made from bog ores. This white earth was metallic in appearance, it was extremely brittle, it was readily fusible, and it was not attracted by magnet. Meyer noted that cast iron containing this white earth was more fusible than other cast iron, and he was sure that he had discovered a new metal ? for which he proposed the name Wassereisen, or the Latin term Hydrosiderum. Two years later the distinguished Swedish Chemist Bergmann made the same discovery, finding a ?white calx? in cast iron, which he also mistakenly considered to be a new metal, and for which he proposed the Siderum.

Jan 1, 1944

By H. I. Aaronson, H. A. Domian, A. D. Brailsford

A current study of the growth kinetics of k (hcp) plates in a Cu-Si (fcc)' has generated a requirement for data 02 the chemical interdiffusion coefficient in a (termed D,) as a function of temperature at the composition of the a/a + k pJase boundary. Rhines and Mehl 2 have determined D, as a function of composition at lower silicon contents by making Matano analyses of concentration-penetration curves. However, the accelerating increase in B, which they demonstrated as the phase boundary composition is approached at constant temperature and the rapidly diminishing accuracy of this analysis as the limiting compositions of a diffusion couple are approached (the silicon-rich component of their couples contained appreciably less silicon than is permitted by the solubility limit) indicate that the required information cannot be safely obtained by extrapolation of their data. Although the quite different method employed in this study is not exact, it will be shown that the approximations made are not serious ones, particularly from the viewpoint of the prgcipal application anticipated for these data. D, was determined from the migration kinetics of the a :k boundaries formed in sandwich-type diffusion couples produced by welding a block of high-purity copper to opposite sides of a cube (* in. on edge) of homogenized high-purity Cu-5.82 wt pct Si alloy. The alloy is pure k in the temperature range employed. The surfaces of the couple components which were normal to the diffusion direction were machined accurately flat and parallel, lightly polished, and carefully cleaned. Welding was then accomplished by means of the vacuum-encapsulated pressure jig technique previously employed.3 Welding was always conducted at the intended diffusion temperature; thus the welding anneal also served as the first diffusion anneal. Subsequent diffusion anneals were performed in evacuated Vycor capsules. Following the welding anneal, one of the surfaces parallel to the diffusion direction was machined, ground, and polished flat; additional material was removed from this surface after each diffusion anneal in order to avoid any effects of composition changes. After etching,4 the average distance between a : k boundaries was measured by means of a traveling microscope with an accuracy (per measurement) of better than 1 p. Satisfactory results were obtained at four temperatures in the range 775° to 655°C; attempts to obtain data at two lower temperatures were unsuccessful, evidently as the result of the interference of surface contamination during the welding process.

Jan 1, 1969

By P. G. Shewmon, W. M. Robertson

The derivative of the surface tension with orientation, ??/??, for copper has been measured over the entire unit triangle. This derivative or torque term was determined from the variation of the dihedral angles at the intersection of twin boundaries and free surfaces. High-temperature anneals in graphite with a hydrogen atmosphere gave torque terms of 0.097 at (111), 0.066 at (100), and 0.0257 at (110). A variation from -36oto +23oC in the dew Point of the H2 had no effect on these values, nor did a change from 99.98 to 99.999 pct Pure copper. The removal of graphite from the system decreased ??/?? slightly. Considering the surface near a low-index plane to be smooth except for occasional steps, the free-energy increment per cm of step is calculated, and it is shown that the observed variation of ??/?? is consistent with a random distribution of steps and an interaction energy between steps. Integration of ??/?? gave the relative values of y at (100), (110), and (111) as comPared to ymax: (Y111/Ymax) =0.974, (Y110/Ymax) =0.996, (y100/Ymax) = 0.983. The ratio of the surface tension of coherent twin boundaries to the surface tension of the free surface was found to be (yT/ys) = 0.027 * 0.011. In a crystalline solid the surface tension y (surface free energy per unit area) depends on the orientation of the surface relative to the crystallographic axes of the crystal. Measurements of this variation of y with surface orientation have been reported for metals only within the last few years. Consider the grain boundary groove shown in Fig. 1. Here the three surfaces are all normal to the plane of the paper, and each has a different surface tension, y1, y2, and y3. If the system is at equilibrium, the total surface free energy must remain unchanged for a slight vertical displacement of the intersection (points A, B, and C are kept fixed). As shown by Herring,' the following equation is obtained:

Jan 1, 1962

By AIME AIME

OUR own Institute of Metals and Iron and Steel divisions cooperated with the Iron and Steel Division of the American Society of Mechanical Engineers, the American Welding Society, and the American Society for Steel Treating in a busy week at Cleveland. The morning sessions were held at the Hotel Cleveland and the afternoon ones at the Auditorium, where the metallurgical exhibition under the auspices of the American Society for Steel Treating not only occupied the arena of the Auditorium but completely filled the huge adjacent Annex. In the intervals of sessions the members thronged the exhibits but in the evenings the local attendance was so great that if the crowds had been any larger it would have been difficult to see the exhibits. With so many firms, both producers of metals and of equipment accessory to their production and use, it would be impossible to mention them -all and unfair to single out a few, since no two individuals' judgment would coincide as to relative interest and importance. In any case an exhibit is a thing to be seen rather than described, and these were well worth seeing.

Jan 1, 1929

By Earl R. Hoskins, James E. Russell

The electrical resistivity of rocks has been studied quite extensively, in particular, the effects of temperature and confining pressure on resistivity. References 1 through 6 at the end of this chapter pertain to electrical resistivity of rock and contain further references on the same topic. The present study is motivated by an interest in determining the in-situ properties of rock as well as the stress state of the rock and how these quantities are changing with time. Most of the previous work on the electrical resistivity of rocks has been directed toward saturated rocks at relatively high confining pressures and temperatures. The present study was oriented towards air-dry surface rock that might occur in mine pillars. The mean stress and temperature under such conditions are comparatively low. It has been demonstrated that the resistivity of rock is highly dependent upon the porosity. In fact, for saturated rocks, a relationship referred to as Archie's law has been established between porosity and electrical resistivity. In the case of saturated rock, the property that is actually being measured is the resistivity of the solid/fluid system. Since the resistivity of the fluid alone is usually much lower than that of the dry rock, it is understandable that the resistivity of a saturated rock is in general several orders of magnitude lower than the resistivity of a relatively dry rocli. For dry rock, it seems reasonable that the electrical resistivity should increase as microcracks open within the material. Since microcracks open as material is stressed closer and closer to its failure point, it appears that there should be a correlation between electrical resistivity

Jan 1, 1970

By Alexander Knoll, Dwight L. Baker

THIS paper is a report on work undertaken to investigate the results and conclusions of Ravitz and Porter1,2 that galena freed of surface oxidation products and lead carbonate ("clean" galena) is waterrepellent, and that the action of xanthates in flotation is the action of a cleansing agent, enabling oxidized galena particles to expose a pure lead sulphide, water-repellent surface. The apparatus, in construction and use, was essentially that of Ravitz and Porter. The only significant modification introduced by the present authors was the substitution of a three-necked flask for the flotation cell as the "reaction vessel." Our procedure was to place 50 grams of freshly ground, minus 200-mesh galena in the reaction vessel, sweep out all molecular oxygen from the system with oxygen-free nitrogen, and proceed to wash the galena surface free of its oxidation products with repeated small portions of (I) ammonium acetate (500 c.c. of water, 200 grams of ammonium acetate) or (2) ammonium chloride, hydrochloric acid (2 liters containing 200 grams of ammonium chloride and 25 c.c. Of 1.18 sp. gr hydrochloric acid). The galena was next washed with many 100-c.c. portions of oxygen-free, distilled water. The galena was finally considered free of soluble salts when wash water that had been in contact with the mineral for at least 48 hr.* gave negative tests for: (x) lead ion with sulphide; (2) chloride with silver ion; (3) acetate with cuprous chloride, sodium chloride; and (4) ammonium ion with Nessler's reagent. Next 500 c.c. of potassium ethyl xanthate solution, free of dissolved oxygen, was run onto the "clean" galena particles. For this system there were determined: I. The wetting properties of the clean galena particles by shaking the reaction flask and noting the degree of mineral collection at the liquid-air interface. This was, of course, simply a qualitative test, but it proved adequate for our purpose. 2. The removal of xanthate ion from the potassium xanthate solution on being shaken with the "cleansed" mineral. Xanthate concentrations were determined by iodine titration according to the methods of Taylor and Knoll.3 3. The pH of the xanthate solution after having been shaken with the "cleansed" galena. The pH was determined colorimetrically.4 The results of five experiments of the type mentioned above are given in Table x.

Jan 1, 1941

By Yeatman, Pope

FOR many years geologists have felt that mining companies should adopt a more liberal policy in the publication of their reports. The increasing usefulness of the geologist to the mining profession in recent years demands that consideration be given to this question. Prior to 1900, the call for geologists of high reputation by mining companies was probably mainly in connection with lawsuits arising from the interpretation of rights or ownership as defined by the "Law of the Apex," and from problems such as finding the continuation of the vein or whether the vein followed was the main one or a branch. Later, outside of legal questions, the most intensive and general use of their services arose from the search for oil. Geologists to determine the position of the formations

Jan 1, 1938

By AIME AIME

AWRDED jointly by the four AW Founder Engineering Societies the John Fritz Medal is generally regarded as the most signal honor that American engineers can confer on a fellow engineer. The roll of 34 recipients contains the names of Lord Kelvin, George Westinghouse, Alexander Graham Bell, Thomas. A. Edison, George W. Goethals, Guglielmo Marconi, and Michael I. Pupin; and among members of the A.I.M.E. now living, Sir Robert A. Hadfield, Herbert Hoover, and Daniel C. Jackling. On the evening of March 1 7 the name of Paul Dyer Merica was formally added to this list of illustrious engineers when the medal was presented to him at a dinner at the Metropolitan Club in New York. The citation read. For important contributions to the development of alloys for industrial uses. Arrangements for the dinner were made by the following committee representing the four Founder Societies: R. C. Allen, George S. Davison, A. A. Potter, and J. B. Whitehead.

Jan 1, 1938

By Robert :H. . Lesemann

I recently gave a talk at a seminar on mine development in the Eighties. I had to present CRU' s long-range market outlook for copper, lead, zinc, nickel, molybdenum and silver. In reviewing the recent history of each metal, and our projections, I tried to find some common pattern of behavior that could prove a guide in projecting future market behavior. When you sweep aside your input-output models and econometric equations, what you seem to be left with is this: "When a market goes through a prolonged period of price weakness, you can usually look forward to a period of considerable improvement. " "When a market goes through a prolonged period of price strength, you can always anticipate a prolonged period of price weakness." Stated another way, "The better things are, the worse they will get."

Jan 1, 1982

By Robert Sisselman

Dramatic changes have been effected since 1955 in the mode of iron ore shipments within the U.S. In 1955, less than one percent of ore consumed in domestic blast furnaces-approximately 125 million long tons-consisted of pellets. Five years later, in 1960, some 94.8 million tons of ore were consumed, 14% in the form of pellets. Projections for 1980 reinforce confidence in this most economic of blast furnace feeds, and set U.S. pellet consumption at 151.2 million tons. In the last decade, pellets caught fire in other countries. By 1969, world production reached 96 million tons. This compares strikingly with present world output of 154 million tons.

Jan 9, 1973

By W. Rostoker, S. A. Spachner

FOLLOWING the discovery of the w transition phase in certain titanium-chromium alloys by Frost, Parris, Doig, and Schwartz, much interest has centered on the alloys in which this phase is found and its mode of precipitation. The w phase has been found in alloys of Ti-Cr, Ti-Fe, Ti-Mn, Ti-MO,2 and Ti-v.3 The temperature-time-transformation characteristics have, as yet, not been determined for most of these. In this study, such transformation characteristics have been investigated for two heat-treatable titanium alloys known to exhibit transition phase phenomena. The alloys chosen, Ti-8Cr and Ti-13M0, are representative of two classes of binary equilibrium systems. In the

Jan 1, 1959

By H. K. Martin

IN September 1954 the Lavender pit concentrator at Lowell, Ariz., began treating low grade porphyry copper ore from the nearby Lavender mine. Nominal capacity of the mill is 12,000 tpd, but production now averages 16,226 tpd. Plant design was somewhat affected by the re-use of old equipment and the substantial re-use of old buildings. A breaking-in period between June 24 and Sept. 1, 1954, was devoted to training operators and making minor changes in launders, chutes, and piping. From Sept. 1, 1954, to July 1, 1956, the mill treated 8,598,105 dry tons of ore, from which 556,541 tons of concentrate were produced, containing an indicated 144,055,185 lb of copper.

Jan 11, 1957