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By E. S. Leaver

THE amount of gold that occurs in a ton of milling ore from most of the large-scale copper mines is so small that unusual care and special attention are necessary to recover it. In some cases the gold is not considered important enough to warrant daily assays of the various products. Considering the large tonnage of copper ores that are now concentrated by flotation, as computed in a recent review, the gross gold content is surprisingly large, probably amounting to over 10 million dollars per year in the United States. The indications are that in many of the copper-milling operations with gold content under $1 per ton, only 50 per cent. of the gold is recovered in the flotation concentrates. Lime is generally used as a depressant for pyrite in the flotation circuit. The authors have shown that high lime or a solution high in calcium ions is also a depressant for gold. Their experiments on several well-known ores show that by careful regulation of the alkalinity of the mill solutions, a higher flotation recovery of the gold can be obtained, together with equally good copper recovery in a good grade of copper concentrates. In cyanidation for the recovery of gold, the best accepted practice demands that the mill solutions be tested and regulated by simple chemical reactions at definite periods during treatment or with each change in the treatment. It is similarly important for the recovery of gold that the solution in the flotation circuit be analyzed for calcium ions at regular periods and at each step in the flotation practice. The lime should be added when and where needed and not in excessive amounts at the head of the mill.

Jan 1, 1931

By James Aston

THREE years ago the writer presented a paper on the trend of development in the wrought iron industry,1 wherein was described a process in the development of which he has been a factor, which at that time had passed through several years of progressive experimental development but which had not then been put upon a commercial scale of operation. The present paper deals with two years of observation and experience in the commercial operation of a plant by the A. A Byers Co. at Warren, Ohio. It will not enter into the controversial field of the relative merit of wrought iron and steel in various classes of service, nor will it elaborate upon the characteristic services or fields of utility to which wrought iron is particularly adapted. It is sufficient to state that the wrought iron industry is upon a substantial basis and that the material finds service in pipe, where its advantages are in superior corrosion, fatigue, welding and threading qualities; in bar iron for staybolts, engine bolts, and rivets, demanding maximum service against corrosion and fatigue; in plates for corrosion service; and in chains, because of welding and shock-resisting characteristics. In short, ability to withstand the stresses of shock and vibration, or the ravages of corrosion, to hold protective coatings, and to give maximum efficiency in welding, are its features of relative superiority. If these features were not well recognized, the wrought iron industry would have shrunk to insignificance in the face of high costs and acknowledged limitations in manufacture. To charge that this industry is built upon a structure of assumption, psychology, and improperly weighed evidence is an impeachment of the integrity or belittling of the powers of observation of users through many centuries of service experiences.

Jan 1, 1929

By C. A. Mitke

(Butte Meeting, August, 1913.) 1. Character of Gases which Caused Helmets to Get Out of Order. DURING September, -1911, the fire area in the Lowell mine continually increased and gases resulting from the fire came through the upcast shaft. These gases contained such a large percentage of sulphur dioxide that the men were unable to go up and down on cages, and, within a comparatively short time, repairs in the shaft were found to be necessary. Since the fire was in sulphide ores and extended into certain timbered sections, the gases contained varying amounts of SO2 CO2, and perhaps, at times, CO. The temperature in the shaft was generally about 97°, and the relative humidity from 97 to 99.5 per cent. The corrosive action of the fumes became apparent when the cables had to be changed more often than usual, the heads of lag screws .in the guides of the shaft disappeared, and the cages needed frequent repairs. It also became necessary to repair two compartments of the shaft by putting in 150 ft. of new guides between the 600 and 800 levels and lag screws in nearly all the old guides from the surface to the 800 level. 2. Ordinary Methods of Testing Helmets which were Unsatisfactory. These conditions required all work to be done by men wearing oxygen helmets. The Draeger type was tried, and was used until all repairs were completed. At first the helmets were. tested for air circulation and air tightness and the injector was tested by water gauge according to the methods recommended by the Draeger Oxygen Apparatus Co. Six arrangements, covering .these different tests, are illustrated in the catalogue and circulars of the company.

Jan 7, 1913

By Wilbur C. Helt, Joseph J. Yancik

Throughout the history of mankind, the principal use of coal has been to produce heat through combustion. The heat is used in many ways: to warm air space for our comfort; to provide heat or energy to power industrial processes, such as cement and steel production; and to produce electricity. Because it is our nation's most abundant fossil energy fuel, coal in the late 20th century is on the threshold of becoming a significant source for synthetic liquids and gas energy fuels for this country. This is made possible by conversion processes which can change solid coal into various synthetic gases and liquids. These coal-derived fuels are nearly identical to the processed fuels and chemicals provided by natural gas and crude oils, which presently provide almost all the petrochemical feedstocks and energy fuels needed for the residential, light commercial, and transportation markets. A revolution is beginning to take place, not only in the United States, but in many other countries with a return to a coal-based energy economy. Also, new combustion and conversion technologies which are compatible with national health arid environmental goals are rapidly emerging. These technologies will allow coal's use to be expanded not only in its traditional markets, but also to supply markets held by natural gas and crude oil. With the worldwide decline in natural gas and crude oil reserves, coal is being looked upon to meet the energy demand. Because of these new coal conversion technologies, coal will no longer be only a combustion fuel, but a valuable raw material for production of a variety of clean fuels and chemicals. MARKETS FOR COAL: PAST AND FUTURE A simplified diagram of the marketing network for coal is shown in Fig. 1. As shown in this figure, coal is transported to its traditional

Jan 1, 1981

By D. E. Wolfson, H. J. Gluskoter, M. R. Geer, John A. Harrison, H. F. Yancey, I. S. Latimer

When this chapter was prepared for the kst edition in 1942, continuous mining machines virtually were unknown, and hand loading in underground mines, which gave an opportunity to discard impurities, accounted for 55 percent of the production of bituminous coal and lignite as compared with the 1965 figure of 11 percent. Only 24 percent of the total production was cleaned mechanically, compared with the present (1965) figure of 65 percent. The amount of refuse discarded during preparation for the same period increased from 13 to 21 percent. Changes in the equipment used in the cleaning process were as follows: [ ] Unclassified nearly 8 percent. Data on the amount cleaned by flotation was not collected until 1960 when 1.8 million net tons was so treated. In 1965 this figure increased to 6.9 million tons. Although the great increase in mechanization and full seam mining has resulted in substantial increases in the impurity content of the raw coal as well as in a finer size consist, some phases of face preparation are still important, particularly the variability of the distribution and thickness of the interbedded impurities and the changes in the character of the roof and floor from place to place in the mine. Knowledge of these factors in relation to all phases of the mining operation, particularly selective mining, are still of importance to the treatment of raw coal in the preparation plant. The major characteristics of coal and impurities from the standpoint of mechanical cleaning are particle size composition, generally called size consist, density differences, the relative friability of the coal and of its associated impurities, hardness, and strength. Some of the other factors related to preparation are petrographic composition and rank. COAL PROPERTIES Rank Perhaps 95 percent or more of the coal cleaned mechanically is of bituminous rank. Only a very small tonnage is subbituminous and prac-

Jan 1, 1968

By Charles Brush

THE general subject of accurate pyrometry, its great development in recent years, and the importance of its application in arts and manufactures is so ably treated in other papers that this paper will bee confined to a resume of some research work on certain temperature effects in carbon and other steels, some of which appear to, be new. The results of these researches are embodied in several papers presented to' various scientific societies during the last few years, most of them under the general title of Spontaneous Generation of Heat in Recently Hardened Steel.1 Several years ago, when studying the behavior, tinder certain conditions, of specimens of hardened tool steel, I observed that they all spontaneously generated a small quantity of heat, the rate of generation diminishing from day to day for several weeks before generation became imperceptible in the sensitive calorimeter used. In each case the steel had been hardened only a few days prior to its use. It seemed highly probable that the generation of heat was associated with some sort of "seasoning" or incipient annealing process, perhaps accompanied by slight changes of volume, and that it would be most rapid immediately after hardening. I subsequently investigated this curious phenomenon more fully. Twelve ½ in. round bars of tool steel, 5 in. long and with machined surfaces, were hardened by heating to high cherry red in a reducing atmosphere of a gas furnace and quenched in cold water. The bars then had a thin strongly adhering coating of black oxide. They were next stirred in a large quantity of water at room temperature, to acquire that temperature, wiped dry, and oiled with heavy, neutral mineral oil to prevent generation of heat by further surface oxidation, wiped free of excess of oil and placed in the copper cylinder of a heat-insulated box.

Jan 9, 1919

By G. D. Bengough

CORROSION tests should be designed so as to facilitate as far as possible the interpretation of results, consequently factors which may affect the rate of corrosion should be controlled as far as practicable, and very full data should be given regarding the conditions of the test. Among the most important factors affecting the rate of corrosion is often the rate of supply f oxygen to the metal surface. It is essential therefore to understand the mechanism by which oxygen is transferred from the liquid surface to the surface of the metal. The work of Adeney and his coworkers has thrown much light on this mechanism. They have shown1 that the aeration of deaerated water and salt solutions proceeds much more rapidly than can be accounted for by mere diffusion, and have suggested that downward "streaming" takes place from the surface of the water, due mainly to an increase of density brought about by evaporation. The evaporation reduces the temperature of the surface layer, and also increases the concentration in the case f salt solutions. The effect of evaporation in facilitating the transfer of oxygen to a metal and increasing the corrosion f the metal was shown in some experiments due to Friend .2 He tested the corrosion f mild steel plates immersed in water in glass jars, a steady stream f air being drawn over the surface of the water in the jars. The air passing through half the number f jars was saturated with moisture, that passing through the others was dried with calcium chloride. He found that "in every case the water exposed to dry air was approximately twice as corrosive as that exposed to air saturated with water vapor."

Jan 1, 1929

By Warnie Flint

According to statistics that have been compiled by the National Safety Council, U.S. Bureau of Mines, American Medical Association, and other agencies, accidental injuries cause more deaths than all the leading diseases. There isn't anyone who is immune to an accident. Probably the best way to describe an accident is to say that it is an unexpected happening. The automobile driver isn't expecting a terrifying crash, the electrician isn't expected to be electrocuted, nor is the coal miner expecting the roof to fall on him. All personal injuries will not result in death. There is a multitude of victims who are living proof of what accidents can mean to an individual. These are the victims who are blind, paralytic, missing arms, legs, etc. In most instances the earning power of these individuals is gone, and they are utterly dependent upon family or welfare. For many years there seemed to be an attitude that prevailed upon industrial America that accidents were inevitable, and that so many fatalities and injuries should be expected. This, of course, was utter nonsense. Since the birth of such organizations as The National Safety Council, American Society of Safety Engineers, and the U.S. Bureau of Mines, much progress has been made in reducing accidents. The enactment of compensation laws greatly contributed to the progress that has been made. Does this mean that all accidents can be prevented? Unfortunately, it doesn't. Human psychology indicates that men will work unsafely or perform unsafe acts for the following reasons: 1) Lack of knowledge or skill. 2) Conflicting motivations, such as: (a) to be more comfortable, (b) to save time or effort, (c) to be accepted by a group 3) Physical or mental condition.

Jan 1, 1973

By Paul Merica

ALTHOUGH nickel was discovered and isolated as early as 1750 and its valuable properties recognized, many years passed before it was used commercially for wire, sheet, rods, etc., in the pure form. This was due partly to its high cost at that time and partly to the fact that it was not possible to refine and cast nickel into ingots sufficiently malleable to be amenable to the usual forging, rolling, or drawing processes. So remarkable was this fact, and so different from the experience at that time with metals such as copper and iron, that it has left its impress on the no-menclature within the nickel industry. To this day, furnace-cast nickel produced in such a manner as to be suitable for rolling and forging is called malleable nickel to distinguish it from the ordinary pig and shot nickel of commerce. In 1878, the firm of Jos. Wharton, of Philadelphia (which later became The American Nickel Works, a constituent of The International Nickel Co.) exhibited at the Paris Exhibition specimens of rolled pure nickel strip and of drawn nickel wire. About this time, there was considerable activity in the study of the refining of nickel and several methods were described, some of which were patented, for the production of furnace-cast malleable nickel including the use of manganese (Boed-dicker,1 Selve and Lotter2), the use of potassium permanganate (Bernsdorfer Metallwarenfabrik3) and the use of phosphorus (Garnier4). By far the most efficient method was discovered by Th. Fleitmann in 1879;5 it consisted in adding to the molten nickel, just before pouring the castings, from 0.05 to 0.125 per cent. of metallic magnesium. This soon became the recognized final malleableizing treatment for furnace-cast nickel.

Jan 1, 1925

By A. S. Richardson

Ventilation of the Butte mines has long been a rather difficult problem because of the natural high temperature of the rock. With increase* in mining depth, higher rock temperatures have been encountered, and this has caused a constantly growing demand for more effective ventilation measures. During recent years the hazards of dust in mine air have been more clearly recognized, and have necessitated the adoption of dust-prevention methods. To meet these ventilation problems in the mines of the Anaconda Copper Mining Co., a mines ventilation department was organized in 1918, to act under the direction of the general superintendent of mines. At the present time, under normal operating conditions, the force employed includes the ventilation engineer, two chief assistant ventilation engineers and eight assistant ventilation engineers. The activities of the department are, briefly: (1) planning and supervising operation of the general ventilation system; (2) planning and supervising the operation of dust-prevention measures, together with dust sampling and related microscopic work for the quantitation of the dust samples and determination of particle-size distribution; (3) the design and development of air-conditioning methods to meet present exceptionally severe temperature conditions and in anticipation of future requirements. To a large extent the technical features of the ventilation methods have been described in earlier papers by the author. This paper is written mainly to summarize past accomplishments bearing most closely on health and safety, with a somewhat more detailed account of the dust-prevention measures that have been developed comparatively recently. Facilitating Flow of Am As a basic requirement for the safety of the mcn, all ventilation plans are subject to a ruling that the main operating shafts must be maintained as inlet air courses. Under this condition, a safe, fresh-air escapeway is assured if a fire occurs within the mine, and the shaft; is available as a base

Jan 1, 1940

By A. S. Richardson

Ventilation of the Butte mines has long been a rather difficult problem because of the natural high temperature of the rock. With increase* in mining depth, higher rock temperatures have been encountered, and this has caused a constantly growing demand for more effective ventilation measures. During recent years the hazards of dust in mine air have been more clearly recognized, and have necessitated the adoption of dust-prevention methods. To meet these ventilation problems in the mines of the Anaconda Copper Mining Co., a mines ventilation department was organized in 1918, to act under the direction of the general superintendent of mines. At the present time, under normal operating conditions, the force employed includes the ventilation engineer, two chief assistant ventilation engineers and eight assistant ventilation engineers. The activities of the department are, briefly: (1) planning and supervising operation of the general ventilation system; (2) planning and supervising the operation of dust-prevention measures, together with dust sampling and related microscopic work for the quantitation of the dust samples and determination of particle-size distribution; (3) the design and development of air-conditioning methods to meet present exceptionally severe temperature conditions and in anticipation of future requirements. To a large extent the technical features of the ventilation methods have been described in earlier papers by the author. This paper is written mainly to summarize past accomplishments bearing most closely on health and safety, with a somewhat more detailed account of the dust-prevention measures that have been developed comparatively recently. Facilitating Flow of Am As a basic requirement for the safety of the mcn, all ventilation plans are subject to a ruling that the main operating shafts must be maintained as inlet air courses. Under this condition, a safe, fresh-air escapeway is assured if a fire occurs within the mine, and the shaft; is available as a base

Jan 1, 1940

By K. D. Eigenbrod

A case history is presented of a landslide that occurred adjacent to a highway in the valley of the North Saskatchewan River, about 12 miles upstream of Edmonton, Alberta. The slide took place in the late fall of 1965 following excavations associated with highway improvements that deepened the slope and cut it back to 20º. The slide occurred in the Upper Cretaceous Edmonton Formation. Till covers the bedrock at the location. The bedrock consists of interbedded mudstone, claystone, and sandstone with layers of bentonite and coal. The field investigation consisted of a series of pits at the toe of the slide and seven boreholes around it. Undisturbed samples were taken with a Pitcher Sampler and piezometers were installed at various depths in the section. The slide had taken place on a horizontal bentonitic clay layer and it crossed softened mudstone in the back slope. Three piezometric levels were detected but no water pressures were found along the horizontal portion of the slip surface because it was in contact with a free-draining coal layer. Borehole evidence revealed that the bentonitic clay layer was sheared in place beyond the confines of the slide zone. Although this slide was a first-time occurrence, it was part of a much larger slide block that moved presumably when the valley was being formed. Laboratory tests were carried out to determine the shear strength parameters of the bentonitic clay and the back slope material. These parameters together with the observed water pressure distribution in the slide area gave a factor of safety of 1.01 in a non-circular limiting equilibrium analysis. The case history is particularly instructive in indicating the care that must be taken to obtain representative information for stability analysis when geological and groundwater conditions are non-uniform. The origin of the sheared clay is discussed.

Jan 1, 1972

GENTLEMEN Submitted herewith are the report of the Treasurer for the year 1938 and reports for the same year of the following standing committees: Admissions, Membership, Papers and Publications, Mining and Metal¬lurgy (Magazine), Library, Speakers for Local Sections and Student Societies, and Student Relations. To these reports members are referred for further details. Membership.-The end of the year 1938 saw Institute membership at an all-time peak: 12,474, made up of 2898 Student Associates and 9576 members of other classifications. The next highest level had been reached at the end of 1921 when corresponding figures were: total, 10,329; student members, 1450; all other classifications, 8879. The net gain for the year was 1495, of which 751 were Student Associates and 744 in the other categories. Two factors contribute to the growth of membership: (1) the enrolment of new members; and (2) the retention of members already on the roll as reflected in a relatively small number of resignations and suspensions for nonpayment of dues. For the first, much credit goes properly to the general Membership Committee that functioned for a second year under the chairmanship of Clyde E. Williams. With the cooperation of Institute members in general, to whom Mr. Williams expresses appreciation in his report, the Committee has been successful in acquainting eligible nonmembers with the purposes, activities and advantages of the Institute. The result has been the receipt during the year of 1162 applications, exclusive of Student Associates. This compares with 1212 during 1937 and 1266 during 1936. However, in considering this modest decline, account must be taken of the somewhat less prosperous conditions prevailing in the mineral industries and, consequently, among engineers engaged ?in those industries.

Jan 1, 1939

By Samuel Shallcross

TO principal function of the Bell limestone mine, of the American Lime & Stone Co., at Bellefonte, Pa., is to supply raw material to the company's modern rotary kiln plant at Bellefonte. Because mining costs are naturally higher than many open quarries with more favorably lying strata, it cannot compete, except to a limited extent, in the markets for road material and fluxing stone. In the broad sense, mining does have an advantage over the average open quarry when the end products are designed for and controlled by process and final inspection for the exacting demands of the industrial and chemical markets. Approximately 80 per cent of the output of the Bell mine is sold in the industrial and chemical markets. And as higher standards are set each year for construction and agricultural work, the remainder of the mine output goes to these two classes. Mining produces more fines than open quarries, and these fines are difficult to market; on the other hand, owing to absence of contaminating clay and impure rock, a greater percentage of the output of a mine is marketable. Because of the great production of fines, rotary kilns for lime burning are necessary when the stone must be mined. In 1921 the American Lime & Stone Co. operated 19 quarries and 72 lime shaft kilns spread over an area of 40 miles between Bellefonte and Altoona, Pa. At that time the lime-production capacity of the 72 kilns amounted to approximately 700 tons per day. After 15 years the company operates three rotary kilns and six shaft kilns, with a combined output of approximately 500 tons of lime per day, concentrated in its single Bellefonte plant (Fig. 1). Its only stone-producing plants are now the limestone mine at Bellefonte and a construction-stone open quarry at Union Furnace, near Tyrone, Pennsylvania.

Jan 1, 1936

By Persifor Frazer

It was my intention to have directed the attention of the members of the Institute to a complete series of rocks representing the older and middle formations represented in Pennsylvania, but time has been insufficient for the purpose, and 1 have been unable, in the first attempts to reduce the sections of those rocks, which I have brought with me to this meeting, to the requisite thinness necessary for exhibiting the peculiarities of their constituent minerals. The rocks represented here belong to the various horizons already mentioned, and include gneiss, ferruginous gneiss, chlorite slate, quartzites, and hydro-mica slates, limestones, dolomites, ferruginous conglomerates, quartz conglomerates, " Potomac marble" (nether member of the Mesozoic series), dolerites, and a syenite. The order in which these are named is, roughly, the order .of geographical position in a section line from southeast to northwest, commencing at the intersection of the Northern Central Railroad with the Maryland line, and ending a few miles from the town of York, and a short distance within the marginal outcrop of Mesozoic red sandstone. In such a geographical section all the rocks above mentioned would be encountered in the given order except syenite, about which a few words are to be said in a moment. (But this is far from representing the rocks in their geological sequence.) There is nothing of unusual interest to present to your notice in these slates and quarteites. The limestones were carefully searched tinder 450 diameters microscopic power, but they show no signs of organic remaius. One section of a fine-grained Triassic sandstone contains a very beau- . tifully banded plate of quartz. But the objects of greatest interest at present are the specimens of trap. The more fine-grained and compact traps were collected from

By R. P. McLaughlin

EXACT information as to performance of the gas lift from the mechanical engineering standpoint is hard to obtain. Several hundred wells are now producing in California fields by means of the gas lift, and a survey of results shows that the gas lift has increased production at these wells by approximately 60 percent. Similar or even larger figures describe results in Mid-Continent fields. Such an increase in output of oil is so satisfactory, to the average oil producer, that it may not encourage investigation looking to more efficient operation. The cost of lifting oil by compressed gas varies from 3 c. to 15 c. per bbl. of oil, depending upon the efficiency of the gas lift. A difference of 10 c. or 12 c. per bbl. of oil is immediately noticed by an oil operator and the cost in production is as real to him as is the price of his product. Therefore, the efficiency of gas-lift process deserves more consideration than it has been given in some quarters. It has been found that there is a wide variation between different operators and at different wells in the amount of gas used per barrel of oil lifted. Some of the most efficient operations show oil being lifted with only slightly over 400 cu. ft. of gas per bbl. of oil.1 On the other hand, wells are being flowed and using as high as 3000 cu. ft. per bbl. of oil. The cost of compressing gas to 300 or 400 lb. varies from 3 c. to 5 c. per 1000 cu. ft. of free gas. This figure has been obtained from a number of sources and as a matter of fact is the basis of actual business transactions involving gas compression. The cost of lifting oil with compressed gas is thus determined.

Jan 12, 1926

By S. F. Ramseyer, E. A. Steigerwald

INFILTRATED structures represent composite materials which are capable of combining high-temperature strength with adequate low-temperature toughness and thermal shock resistance. Although copper- and silver-infiltrated tungsten structures are actually being used in rocket nozzle hardware, adequate understanding of the fracture mechanics of these composite systems is not available. Specifically the relative importance of the strength, ductility, and modulus of the infiltrant in determining composite properties is not known to the extent that optimum composites can be selected. The major portion of experimental effort in the area of composite strength has been devoted to fiber-reinforced systems1 or to systems where a discontinuous phase is imbedded in a relatively ductile matrix.2'3 In the case of high-temperature systems, which are composed of a relatively brittle matrix, such as tungsten or an oxide, a continuous phase exists for the propagation of a crack. The method by which the presence of a conjugate ductile continuous phase influences the gross properties of the composite represents an area which requires further investigation. This technical note presents results which evaluate the effect of infiltrant strength on the strength of the tungsten-base composite. A tungsten matrix and copper-base infiltrant were selected for the initial studies because of the ease of fabrication. Tungsten structures with nominally 20 and 30 pct porosity were evaluated. The porosity was controlled by varying the initial powder size and a ratio of open-to-total porosity greater than 95 pct was obtained by selective sintering cycles. The processing sequence involved hydrostatic pressing followed by a 72-hr presinter in hydrogen at 2000° F and a final sinter at 4000°F for 4 hr in vacuum. The 20 pct porous structure was obtained

Jan 1, 1965

By D. E. Hilts, R. P. Miller

A large coal-fired power plant is to be built jointly by Pacific Power & Light Co. of Portland, Ore., and by The Washington Water Power Co. of Spokane, Wash., at a site about six miles northeast of Centralia, Wash. (Fig. 1 inset). Coal will be mined from nearby open-pit strip mines that will require cut slopes up to 250 ft in height. Coal will be removed from a seam approximately 50 ft thick, located at the bottom of the mine slopes. The coal fields are located in a geologically complex area that has been subjected to intense folding and faulting. As a result, the soils and rock comprising the overburden are highly fractured, jointed, and faulted. Classical approaches to slope stability based solely on the physical proper- ties of the overburden appeared to offer little assurance that theoretically stable slopes would remain stable. Further, the scope of the exploration program that would be required to provide a reasonable evaluation of the primary and secondary structural features from which a statistical evaluation could be developed was considered impractical. As part of the development of an overall mining plan, an experimental Pilot mine excavation, about 225 ft high and about 400 ft long at the base, was made within the coal field. This experimental cut was to provide firsthand knowledge of cut slope behavior. Our purpose at the Pilot mine was to observe the cut slopes as the excavation proceeded. To accomplish this purpose, the highwall of the experimental cut was instrumented to measure face movements and movement at depth behind the face. In addition, a detailed geologic map of the soil and rock conditions exposed in the highwall was prepared, and continual visual observations of the mine were made, noting significant events as they occurred.

Jan 1, 1970

By J. E. Clennell

It is a common observation that the improvements introduced in practice since the first announcement of the cyanide process have been almost entirely mechanical. Although .a good deal of study land research has been devoted to the chemical problems [involved, the results obtained appear trifling in comparison. Few of the suggested modifications in the chemical treatment have come into practical use and those only in limited fields. Nevertheless, if we study the recent history of the cyanogen compounds from a somewhat broader standpoint, we shall find that considerable additions have been made, not only to our knowledge of their chemical properties, but also to their applications for industrial purposes. The present review of these advances naturally falls into two divisions: (1) processes involved in the treatment of ores; (2) manufacture of cyanides and other related compounds. Part I. Advances in the Chemistry of Ore Treatment by Cyanide In the attempt to extend the scope of the process, various ores have been encountered which contain gold and silver in such forms that they will not yield satisfactorily to ordinary methods of cyanide treatment. In some cases the difficulty is due to the excessive action on the solution of base metals present in the ore; in others, to the occurrence of minerals such as dyscrasite (the native alloy of antimony and silver), or a supposed oxidized manganese compound containing silver, which are either altogether insoluble in or very slightly attacked by cyanide. A particularly troublesome case is that of the so-called "graphitic" ores, containing carbon in some form which has the property of precipitating gold and silver already dissolved. Other efforts have been directed to improving extraction by electrolysis of working solutions, and by addition of various chemicals with or without electrolysis; to the diminution of cyanide consumption by "re-

Jan 1, 1916

By J. E. Tiffany

FOR blasting in coal mines the U. S. Bureau of Mines recommends that permissible explosives be used exclusively, that these shall be fired electrically, and that where feasible the working place shall be cut or sheared. These recommendations are made to promote safety and prevent mine explosions. Although permissible explosives are not flameless, their lower flame temperature and shorter duration of flame make their use safer than that of non-permissible explosives. Mixtures of air with both methane and bituminous coal dust, which are liable to occur in coal mines, may be ignited by coming in contact with any type of flame or spark of sufficient temperature and duration or by the firing of a blast. In a working place where a blast is to be fired, in addition to the use of permissible explosives, adequate ventilation for the dilution and removal of accumulations or outbursts of flammable gas should be provided. Bituminous coal mines should be rock-dusted as a means of rendering the coal dust harmless. The efficient use of permissible explosives depends upon the proper preparation of the working place, standardized drilling, the strength characteristics of the explosive, and the use of a proper weight of charge. Experienced shotfirers should load, tamp and fire all holes. The major part of the information and data here presented is based on the results of efficiency tests made in large producing mines of Pennsylvania and Illinois. Bureau of Mines Report of Investigations, Serial No. 2697, describes how a standard method of blasting was worked out and put into operation in a mine in southern Illinois.1 This paper contains a description of the methods worked out subsequently in another mine in that district.

Jan 1, 1928