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By R. E. Tate, L. J. Herman

We have had occasion to produce wire of Np-237 in small diameters for use in some chemical experiments. Since the mechanical metallurgy of neptunium has not been investigated extensively, it seems desirable to report our successful extrusion technique. Because of the neptunium activity and its attendant health hazard the experimental work was done in glove boxes and related equipment also used for Pu-239. At room temperature a phase neptunium' is a hard (Dph -355) orthorhombic metal of high density (p = 20.45 g per cu cm). a neptunium transforms2 to tetragonal ß neptunium at about 280°C and this in turn transforms to bcc y neptunium at about 577°C. The y phase melts at about 637°C. A temperature of 340° to 345°C was selected for the extrusion, this temperature being a compromise be- tween a possible advantage of working with the presumably more plastic cubic y phase above 577°C and the risk of having the neptunium react with the alloy steel die to form the low-melting Fe-Np eutectic. A 0.75-in.-long, 0.26-in.-diameter ingot of good-purity* Np-237 was extruded by the direct *C = 230 ppm, Pu = 200 ppm, thirty-five metallic elements below limit of detection by spectrographic methods. process through flat-face orifices to form several sizes of wire ranging from 0.010 to 0.030 in. in diameter. Molybdenum disulfide was used as the die lubricant. The extrusion was done in a vacuum of about 10-4 torr to reduce reaction of the neptunium with atmospheric gases. British workers3 at Harwell have extruded neptunium under similar conditions. The force required to extrude 0.010-in.-diameter wire at the rate of 4 in. per min was 6000 lb, as measured with an electrical load cell. Wire 0.020 in. in diameter was extruded with a force of 4700 lb at a rate of 2 in. per min, and wire 0.030 in. in diameter was extruded with a force of 4000 lb at a rate of 1.3 in. per min. An extrusion constant, c, can be computed from the measured forces, P, for the equation4 P = c log-A/a where A/a is the extrusion ratio or the ratio of the cross-sectional areas of the container and the

Jan 1, 1965

By HERBERT G. MOULTON

FROM prehistoric times to our own day man has struggled against extremes of climate. Human life, originating in semi-tropical or temperate areas, was unable to progress into the northern latitudes until fire was discovered and some form of clothing provided. It was found possible to maintain life even in the hottest parts of the tropics, but only at a great sacrifice of comfort and efficiency compared with the more temperate zones, or in cooler areas with the protection of clothing and artificial heat. It was no accident, but the natural result of climatic conditions, that efficiency became the greatest and civilization the most advanced in areas where the natural climate was favorable, or in cooler zones where protection against severe cold could be se-cured by relatively simple methods of conserving or producing heat.

Jan 1, 1933

By J. A. Fellows, Earnshaw Cook, H. S. Avery

THE increased use of heat-resistant alloys (26 per cent Cr, 12 per cent Ni, 16 per cent Cr, 35 per cent Ni, 12 per cent Cr, 60 per cent Ni, etc ) in recent years has been accompanied by continued demands by the consumer for improvement in properties The manufacturers of these materials, of necessity, have resorted to more critical studies of the basic causes of variations in fundamental properties To keep pace with the need for augmented information, previous techniques of investigation have been refined and new test methods and instruments created It is the purpose of this paper to describe the apparatus, experimental technique and precision of measurement that were employed in the exploration of properties of heat-resistant alloy presented in a companion paper† The detailed precautions in experimental procedure essential for attainment of accurate and comparable data at elevated temperatures cannot be too highly emphasized THE CREEP TEST Since the fundamental concepts of creep testing have been recognized for the past 20 years, present interest is restricted to refinements in equipment and experimental procedure The creep-test laboratory constructed for the American Brake Shoe and Foundry Co is designed to permit 1000-hr tests in the temperature range of 1200° to 2200°F with a choice of applied stress extending from 50 to 50,000 lb per sq in in increments of 50 lb per sq in To simplify the calculation of weight combinations, the loading beams (Fig I) are provided with counterweights to eliminate the tare The precision of the knife-edges (10 1 ratio) is such that a 10-gram weight placed on the upper specimen grip will be exactly balanced by a 1-gram weight attached to the loading shackle Check of the loading weights proved the maximum error to be 0 06 per cent Axial alignment is provided by crossed knife-edges in the grip seats The furnaces are similar in design to those of Crane and Company, Battelle Memorial Institute, and the U S Steel Corporation An 80 per cent Pt, 20 per cent Rh No 19 B and S gauge wire is used as the heating element The details of construction are shown in the radiograph reproduced in Fig 2 The windings are held in place on an alundum tube with alundum cement, the distribution of turns is adjusted to give a maximum temperature gradient of ± 1°F over a 4-in gauge length (Fig 3) To avoid sharp temperature differentials at the ends of the test section, the length of the furnace is four times the gauge length Sixteen-inch coupons are used to reduce the temperature of the threaded

Jan 1, 1942

By Thomas R. Stauffer

The principle that conventional schemes for taxing petroleum or mineral resources are "inefficient" is illustrated using simulation calculations tested against an "ideal" system. Inefficiency is defined as the relative success in maximizing expected government revenues from the resources. Most systems fail because: 1) they leave oil in limbo, i.e. unproduced because of excessive fiscal burden; or 2) they unnecessarily increase the variance in the explorationist'c, rate of return by undertaxing large fields and overtaxing smaller but infra-marginal fields. This increases his discount rate and reduces taxable surplus. An "ideal" tax system is specified which maximizes government revenues while minimizing risk to the operator. Two criteria are developed: 1) the tax falls to zero on fields which yield only the minimum necessary rate of return ("marginal" fields); and 2) the after-tax present value of all fields is the same for all fields above a threshhold size. In particular, marginal fields, while contrib- uting little to expected values, do contribute to reducing variance and hence risk praemia by distributing the exploration costs over a higher probability of successful outcomes.

Jan 1, 1982

By Henry Newton

It may seem somewhat a work of supererogation to present to the American Institute of Mining Engineers, composed largely of gentlemen with whom the subject is so familiar, a paper on iron ores and their distribution. To many of them, however, it possibly will not be without interest, as there may be some, like myself, who hare nowhere found a connected account of the character of the deposits and the circumstances upon which are founded the great iron-producing centres of the world. This blank I have endeavored to fill,

By Henry Newton

IT may seem somewhat a work of supererogation to present to the American Institute of Mining Engineers, composed largely of gentle- men with whom the subject is so familiar, a paper on iron ores and their distribution. To many of them, however, it possibly will not be without interest, as there may be some, like myself, who hare nowhere found a connected account of the character of the deposits and the circumstances upon which are founded the great iron-producing centres of the world. This blank I have endeavored to fill,

Jan 1, 1875

Jan 1, 1947

Jan 1, 1947

By R. J. Woody

DESIGN of the most economic continuous counter-current decantation (CCD) circuit is based on selection of the number of stages and the wash volume that will give the minimum summation of the following items: 1) Capital and operating costs of the CCD circuit. 2) Capital and operating costs of the precipitation circuit. 3) Value of the dissolved product lost.

Jan 7, 1958

By G. R. Speich, L. Zwell, H. A. Wriedt

HORNBOGEN1 has recently shown that it is possible to measure the degree of segregation accompanying cellular precipitation in ferritic Fe-Zn alloys by measuring the lattice parameter of the ferrite phase within the cell. In extending this work to study a wider range of composition and to evaluate the free-energy change accompanying the growth of the cells, the lattice parameter and the boundary of the a! phase in Fe-Zn alloys were redetermined to check the earlier work of Schramm.2 This appeared to be necessary since the Fe-Zn diagram has been drastically revised since the work of Schramm. Stadelmaier and Bridgers3 have recently shown that, contrary to prior belief: the y iron field is closed and the a phase boundary extends to an a + T + L peritectic at 782°C where peritectic a contains 42 at, pet Zn. The phase T in equilibrium with the a solid solution has a composition near Fe3Zn10 and a cubic 081 type structure.' The alloys were prepared by two different methods. In the first method carbonyl iron powder (400 mesh, 99.8 pet pure) and high-purity zinc powder (200 mesh, 99.99 pet pure) were mixed in a ball mill and then pressed in a die at 40,000 psi pressure to make compacts with a diameter of 5/8 in. and a thickness of l/4 in. These were sealed in evacuated quartz capsules, gradually heated to 1100°C over a period of 1 week (3 days at 600°C) 3 days at 800°C, 1 day at (1100°C), and then quenched in iced brine. For the alloys containing 23.4 and 30.1 at. pet Zn, the final homogenization anneals were performed at 1000" and 850°C) respectively, to prevent melting. In the second method, alloys were prepared by saturating high-purity iron millings (0.001 in. thick, 99.9 pet pure) in zinc vapor. For each alloy the impregnation was conducted at a fixed vapor pressure of zinc and a fixed temperature between 750' and 800°C. When saturated, the millings were quenched in water. The compositions of the alloys prepared by both methods are shown in Table I. The lattice parameters of the ferritic solid solutions were determined by comparing the 26 values of their 310, peaks (using Co Ka) or of their 211 , peaks (using Cr Ka) with those of corresponding peaks for high-purity a iron. The 20 values were measured at room temperature with an X-ray dif-fractometer (G.E.-XRD5). By using a fiducial value of 2.8664Å for the lattice parameter of pure a iron at 25oC,5 the lattice parameters of the zinc-bearing

Jan 1, 1964

Jan 1, 1886

By R. Ruka, E. A. Gulbransen

ONE of the interesting questions in the understanding of the reaction of iron with oxygen is the kinetics and the mechanism of the crystal structure changes occurring in the formation and breakdown of the oxide film. In a recent work' the electron diffraction method was applied to the study of the solid phase reactions occurring internally in the oxide film on iron above 570°C and under vacuum conditions. The higher oxides which form under oxidizing conditions are reduced internally by the diffusion of iron into the oxide leaving the bulk of the oxide FeO (wüstite). This paper will ask and consider three questions. These are: (1) What is the nature of the depressed transformation temperature for the Fe3O4 + Fe ? 4Fe0 reaction in very thin oxide films?; (2) What is the mechanism of the forward transformation of Fe3O4 to FeO at or near 570°C?; and (3) What is the nature and mechanism of the slow reverse transformation of FeO to Fe3O4 and Fe below 570°C?. The composition of the oxide as well as its electrical, magnetic, mechanical, and chemical properties depends upon the kinetics of these reactions. Literature Survey The composition of the oxide film on pure iron at temperatures up to 570°C has been studied extensively by the electron diffraction method. Nelson,' Jackson and Quarrell,3 and Gulbransen and Hick-man4 have shown that Fe3O4 and a-Fe2O8 are formed in the temperature range of 225" to 570°C, while y-Fe,O, is most likely formed below 225°C for long oxidation times. In very thin films FeO (wüstite) is found to form at temperatures as low as 400°C, and its existence depends essentially upon the extent of initial oxidation. FeO is not found in the formation of thick films below 570°C. On the other hand X-ray5 and micrographic8 studies show that Fe3O4 may exist as the main com-ponent in thick films up to 650°C, well above the equilibrium temperature for the reaction Fe3O4 + Fe ? 4FeO. The kinetics of the forward and reverse trans-formations of the reaction Fe3O4 + Fe ? 4FeO have not been studied in oxide films. However, analysis of the data of Gulbransen and Hickman4 on the heat-ing and cooling of iron oxide films of known thick-nesses in high vacua shows that the forward reac-tion proceeds rapidly even for a 4000 A film at temperatures of 575" to 600°C. The reverse reaction or decomposition of wüstite (FeO) occurs at tem-peratures below 450°C. Thus, there appears to be a slow process in the decomposition which is in marked contrast to the rapid forward reaction. The decomposition of a bulk sample of FeO free from the metal has been studied extensively by Chaudron, Benard and coworkers using the micro-graphic, X-ray diffraction, and thermomagnetic methods. Chaudron7,8 first observed that the de-composition of FeO (wüstite) below 570°C occurs by the reaction 4FeO ? Fe3O4 + Fe. Later work by Chaudron and Forestier5 showed that the rate of de-

Jan 1, 1951

By Ellsworth Daggett

The ore smelted in the Winnamuck furnace during the year 1872 consisted, for the most part, of oxidized ores from the Winnamuck mine, only sixty tons of outside ore (from the Spanish mine) having been smelted. The latter, like the principal Winnamuck ore, was oxidized or so-called carbonate ore. There was mixed with these oxidized ores three hundred to four hundred tons, or 7 to 10 per cent. of galena, some of which was mined with the oxidized ore, while a part was mined separately from the lower portion of the mine, and afterwards mixed with the ore, with a view of preventing the formation of deposits of metallic iron in the furnaces. The average assay in silver of all the ore handled was 51.46 oz. per ton, most of it existing as chloride of silver. The lead contents were 34.98 per cent,, all, or nearly all, in the form of carbonate of lead. The relative amount of silver is not at all constant, the best silver ore often being poorest in lead. The predominant gangue was silica, several determinations of which have been made on representative samples, yielding in three such samples 26, 38, and 58 per cent. silica, the latter test being ore containing but little lead. The average contents in silica are about 35 per cent., with 6 to 7 per cent. sesquioxide of iron, and small quantities of alumina and lime. Mechanically, the ore was very fine, and so thoroughly disintegrated that it presented few distinguishing characteristics, rendering sorting or separating of ore from waste difficult, and often impracticable. Experiments on a small scale have been tried, with a view to separate the silica by washing; but these were unsuccessful, as the finest slime, requiring a long time to settle in still water, contained a large amount of silver; and on a careful sizing and washing of the sands and coarser parts, the silver contents were found to be less dependent upon specific gravity

By Ellsworth Daggett

THE ore smelted in the Winnamuck furnace during the year 1872 consisted, for the most part, of oxidized ores from the Winnamuck mine, only sixty tons of outside ore (from the Spanish mine) having been smelted. The latter, like the principal Winnamuck ore, was oxidized or so-called carbonate ore. There was mixed with these oxidized ores three hundred to four hundred tons, or 7 to 10 per cent. of galena, some of which was mined with the oxidized ore, while a part was mined separately from the lower portion of the mine, and afterwards mixed with the ore, with a view of preventing the formation of deposits of metallic iron in the furnaces. The average assay in silver of all the ore handled was 51.46 oz. per ton, most of it existing as chloride of silver. The lead contents were 34.98 per cent., all, or nearly all, in the form of carbonate of lead. The relative amount of silver is not at all constant, the best silver ore often being poorest in lead. The predominant gangue was silica, several determinations of which have been made on representative samples, yielding in three such samples 26, 38, and 58 per cent. silica, the latter test being ore containing but little lead. The average contents in silica are about 35 per cent., with 6 to 7 per cent. sesquioxide of iron, and small quantities of alumina and lime. Mechanically, the ore was very fine, and so thoroughly disintegrated that it presented few distin¬guishing characteristics, rendering sorting or separating of ore from waste difficult, and often impracticable. Experiments on a small scale have been tried, with a view to separate the silica by washing; but these were unsuccessful, as the finest slime, requiring a long time to settle in still water, contained a large amount of silver; and on a careful sizing and washing of the sands and coarser parts, the silver contents were found to be less dependent upon specific gravity

Jan 1, 1874

By S. F. Emmons

Jan 1, 1899

By R. W. Parsons

This discussion concerns fitting an ellipse to angle, where the permeability k is measured for a series of plugs cut from varying angles in the horizontal plane. The conclusions and procedures given by Greenkorn, et al. are in no way affected by these comments, since the degree of anisotropy (ratio of maximum to minimum permeabilities) they found is generally quite close to one (see their Table A-1). However, since large anisotropies may arise, I feel that the comments should be made. Both Marcusl and Scheidegger2 have shown that there are two limiting expressions for the permeability of an unbounded anisotropic media. If the permeability is measured in the direction of the pressure gradient, the result is equivalent to the author's Eq. 11. This is the equation used to find kl1 and k22 from the experimental data. If, however, the permeability is measured in the direction of flow, then the resulting equation for the measured permeability is From these equations it follows that plots on angle will be ellipses. The principal axes will correspond with the major and minor permeability axes. The question arises as to what permeability is actually being measured on an anisotropic sample in the laboratory. An overall pressure gradient and a gross flow rate are determined and a permeability calculated by Darcy's law. The details of the macroscopic flow within the sample will be determined by the boundary conditions of the sample and the orientation and magnitude of the major and minor permeability axes. The situation is shown in Fig. 1 for the two-dimensional case. Using the method of conformal mapping, Marcusl has solved the problem of determining the overall apparent (or measured) permeability for this experiment for any condition of W-L ratios and orientation and magnitude of the principle permeability axes. For W-L ratios approaching zero, the streamlines are all forced by the boundary conditions to be in the direction of the measured permeability which is equal to kg. For W-L ratios approaching infinity, the effects of the no-flow bounds are negligible, and the pressure gradient and measured permeatility direction are parall;l. The streamlines are

Jan 1, 1965

By R. C. Thompson

THE lead-zinc mill of Phelps Dodge Corporation, Copper Queen Branch, Mines Division, Bisbee, Arizona, is about 3 miles from the main hoisting shafts of the Junction and Campbell mines at Lowell. All the ore treated in the mill is obtained from these two mines. The mill was designed for an all-flotation treatment of 450 tons of lead-zinc ore per day, and has been operated at that capacity since the start of milling operations on Nov. 17, 1945. An expansion program is underway whereby the mill capacity will be doubled, but this article describes only the original program and presents results of the 45o-ton operation. GENERAL DESCRIPTION The milling plant consists of an ore-receiving bin and three steel-constructed buildings housing, respectively, the primary crushing equipment, the secondary crushing equipment, and the ore-storage bins, grinding, flotation, and filtering equipment. The mill site is the one that was used for a previous copper-concentrating plant, which was operated over a period of years and then dismantled. There remained from this operation some milling equipment, a reservoir for mill-water supply, railroad tracks, tailings-disposal ponds, and a steel-constructed building, all of which were incorporated in the design of the present lead-zinc mill. The location plan of the plant layout is shown in Fig I. The flowsheet of the mill is based on the conventional scheme for lead-zinc treatment, however, several innovations were made necessary in order to utilize the existing building. Placing of equipment also was governed by the design of the building; thus making the mill unique in many respects. The following brief description of the mill building as adapted to the flowsheet points out the compactness of the installation and some of its unusual features. The first floor (Fig 2) houses the grinding equipment, with connecting conveyors for ore feeding, also an air compressor, two vacuum pumps, bins for lead and zinc concentrate storage with individual conveying systems for loading the two kinds of concentrates. Filtering of concentrates is done on the second floor, the concentrates discharging directly into the concentrate-storage bins. On this floor are the lead and zinc filters, two diaphragm pumps, sample-filtering equipment, sample-preparation room and a change room for the mill employees. The flotation machines are on the third floor, at elevations allowing a gravity flow of the lead and zinc concentrates to the thickeners. The annex to the building contains a freight elevator and provides space for all reagent mixing and feeding, also storage of reagents and grinding balls. All the water used for milling purposes is pumped from the Junction mine and

Jan 1, 1947

By R. W. Powers, M. V. Doyle

ThE solution of a diatomic gas such as 0, or N2 in a metal usually follows Sieverts' law; i. e., Here C is the solute concentration at equilibrium and P, the gas pressure. The proportionality constant Ks is also the equilibrium constant for the reaction 1/2 02 (at pressure, P) - 0 (in solution at [21 concentration., C). to use oxygen as an illustrative gas. Sieverts' law is therefore interpreted to indicate that diatomic gases go into metallic solution atomically and that the solute "gas" atoms interact negligibly with each other. Of course, this interpretation is strictly valid only over the temperature interval in which the reaction indicated in [Z] can be investigated. At temperatures several hundreds of degrees below this interval, the possibility of interactions between solute atoms is conceivable. Indeed, from internal-friction measurements some evidence for the existence of groupings of oxygen atoms in tantalum solid solutions was presented a few years ago.1,2 Over a range of solute concentration, the experimental oxygen internal-friction peak in tantalum, measured as a function of temperature at constant frequency of vibration, can be described as the sum of two elemental peaks, each corresponding to a separate relaxation process. At 0.7 cps, the height of the elemental peak found at 137°C is proportional to the oxygen content, whereas the height of the one at 162°C varies as the square of the oxygen concentration. The 137°C peak was presumed to arise from the stress-induced ordering of oxygen atoms among various classes of octahedral sites in the manner proposed by Snoek.3 The 162°C peak was attributed to a somewhat similar stress-induced ordering process, in which each oxygen atom was interacting with a neighboring oxygen atom. Similarly, the experimental peak due to nitrogen in tantalum can also be described as the sum of two peaks. The height of one varies as the nitrogen concentration and the other as the square of this quantity. In fact, some evidence of solute interactions exist for all oxygen and nitrogen solid solutions of Group V transition metals. However, the interaction energy was not obtained previously for any alloy. The determination of this quantity, as a part of a more intensive study of the interaction between oxygen atoms in solid solution in tantalum, is reported in this paper. PRINCIPLE OF THE EXPERIMENT Consider an equilibrium in a solid solution of tantalum between oxygen atoms which are bound together pairwise and those solute oxygen atoms which are not so associated. 20 (Ta) - O2 (Ta) [3]

Jan 1, 1960

By D. S. Choi, R. Stefanko

There are a number of complex factors that influence the effectiveness of anchorage to maintain tension in rock bolts. However, a plastic analysis of the anchorage site employing certain simplifying assumptions with application of the Mohr-Coulomb criterion appears to explain the observed phenomena. Such an analysis has been made and a correlation sought with field and laboratory tests. Field tests were made in an anthracite mine in eastern Pennsylvania and included pull tests and long-term tests of a variety of anchorage devices in two basic lengths, 30 and 42 in. in two widely differing seams. Performance is reviewed for wedge, expansion shell, and resin anchorage. Laboratory tests duplicated many of the field conditions but in addition compared the performance of shells with normal and reversed serrations. This performance was compared with the predicted results from the plastic analysis. One of the major problems in conducting long-term underground tests is the selection of suitable instrumentation. All installed bolts were fitted with spherical and hardened washers to insure the best possible torque wrench readings. In addition, commercially available load cells were used. Finally, the performance of a specially developed strain-gage-equipped ring cell is viewed. Rock bolting as a method of support continues to increase with applications in many other industries in addition to mining. Nevertheless, with nearly 55,000,000 roof bolts installed in coal mines alone last year, this remains as the single greatest use. While bolts have frequently supported ground where conventional timbering could not, there are relatively few design criteria; and trial-and-error procedures prevail. Furthermore, there has been a lag in development of suitable instrumentation that is simple to install and read out, sensitive, durable, reliable, safe, and economical in evaluating the effectiveness of a bolt over long periods of time. Therefore, the pull test continues to be the most popular method of evaluating the applicability of a certain type of roof bolt under specific installation conditions. At The Pennsylvania State University in the Dept. of Mining, research has been conducted for a number of years to measure bleed off in carefully controlled laboratory experiments as well as in underground investigations."-' Unfortunately, most of the instrumentation developed has been primarily suitable only for research purposes, not possessing all of the aforementioned characteristics desirable for routine underground use. Other groups also have met with restricted success. Therefore, while relatively crude, the torque wrench continues to remain as the most widely used load measuring device. While both field and laboratory tests continue to be con- ducted, analytical analyses are attempted to discover the more important design parameters in order that more efficient anchorage might be devised. Bolts are being used for a greater variety of purposes in mining. Suspending wire sideframe belt conveyors from roof bolts is a common application. The suspension of a monorail transportation system presents yet another. One such system has just been installed in a recently reopened anthracite mine and is presently being evaluated under production conditions. Preliminary studies revealed that a considerable cost reduction was possible by suspending the monorail on bolts anchored in the top. The monorail was to be installed under two widely differing conditions—a competent sandstone above the Buck Mountain seam and a softer shale top above the Skidmore. The type of anchorage device, length of bolt, and long-term performance, consistent with economy and safety, had to be established for the installation once the decision was made to suspend the system on rock bolts. This paper describes some of the testing procedures leading to a final selection. Theoretical Analysis of Expansion Shell Anchorage A detailed look at an expansion shell assembly might shed some light on the factors involved in the design of a suitable shell, Fig. 1. When a bolt is rotated, the tapered plug is forced downward, expanding the leaves laterally to grip the sides of the hole. Two friction surfaces are present: (1) the interface of the plug and leaf and (2) the interface between leaf and rock. The relationships of these friction planes, geometry of expansion shell, and properties of the rock are important in the design of an expansion shell. Therefore, an analysis assuming the rock to behave as a rigid plastic material with its yield governed by the Mohr-Coulomb criterion was made." Furthermore, the effect of friction between the leaf and rock produced by serrations was analyzed.

Jan 1, 1971

By Milton H. Fies

THE writer wishes to acknowledge at the outset his great sense of obligation to those who contributed so broadly and expertly to the preparation of this paper: Dr. Albert DeSmaele, Chairman of the Board of Directors of Socogaz, Belgium; Dr. Julien Venter, Director of the National Institute of Coal Mining and Coal Utilization Industry, Belgium; Dr. Roger Loison, Chief Engineer, French National Coal Research Board, France; and Dr. Erich Sarapuu of the Sinclair Coal Co., Kansas City, Missouri. Liberal use has been made in this paper of a recent publication on Russian, Italian, Belgian, and French experiments prepared jointly by the Centre d'Etudes et Recherches des Charbonnages de France (Cerchar) and the Institut National de l'Industrie Charbonnière of Belgium (Inichar).1 The writer is particularly indebted to Dr. E. T. Wilkins, of the Fuel Re¬search Station, London, and to Mr. James L. Elder, of the Alabama Under¬ground Gasification Experiment at Gorgas, Alabama, for their unfailing patience and effective support. Not only did these experienced and capable men edit and revise this discussion, but much of its content is a direct con¬tribution quoted in full from their memoranda. Without the assistance of all these colleagues, this presentation would not have been possible. It has been a privilege to serve and work with them and to acknowledge repeatedly their loyal cooperation. The recovery of the energy inherent in coal beds throughout the world has been done through the years by methods that today may be justly regarded as primitive. While the techniques of coal mining through the application of machines and the enhancement of information and skills have advanced to an extraordinary extent, particularly during the past 20 years, the underlying means is essentially the same as when man first began to mine coal. Despite this progress in the manner of coal mining, it continues today as a hazardous, toilsome, grimy task. Coal mining per se has advanced at a greater and more rapid stride in the past 25 years than the mining of any: other mineral, but the basic method is fundamentally the same as it was the first day a miner took a pick into his hands many centuries ago. This situation presents a challenge to mining engineers everywhere, from

Jan 1, 1953