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By Frank Firmstone

In the Kaernthner Zeitschrift, No. 2, 1881, p. 53, et seq., Prof. Ledebur details some experiments on the power of various silicates of lime and alumina, magnesia and alumina, and lime, magnesia and alumina, to remove sulphur from pig-iron, from which it appears (as has long been recognized in practice) that the more basic the silicate the greater the quantity of sulphur it will take up; but also that for the same grade of silicate, this quantity is greatest for the lime-alumina silicate and least for the magnesia-alumina silicate, the lime-magnesia-alumina silicate occupying an intermediate position, and he concluded therefrom (p. 59) that, for the production of pig-iron low in sulphur, pure limestones are to be preferred to those containing magnesia. Much the same opinion has been published elsewhere on high authority, and lately (not to multiply references) by Sir Lowthian

Jan 1, 1895

By J. D. Miller, A. Cortez, J. Hupka

The separation efficiency of the hot water digestion-flotation technique used for bitumen recovery from various domestic tar sands was evaluated. Bitumen viscosity was found to be the most important tar sand property in determining the success of the bitumen separation. Bitumen viscosity of the tar sand war controlled by changes in digestion temperature and/or changes in diluent (kerosene) addition. Complete and uniform dilution of the bitumen phase was achieved by providing a sufficient presoaking, or penetration time, for a given tar sand type. For all the tar sand samples tested, an excellent correlation was obtained between the coefficient of separation and the bitumen viscosity. To achieve a satisfactory coefficient of separation, it was found that the bitumen viscosity must be reduced below 1.5 Pa.s (16 P) at the temperature of digestion. This was the case regardless of the tar sand type, grade, or origin.

Jan 1, 1984

By J. Gurland

The wmk is concerned with the estimate of the degee of continuity of a particulate phase dispersed in a matrix. The first section is a verieu: of the parameters nzeasurable by quantitative rnetallogvaphy, namely the contact area and, under certain conditions, the number of contacts between particles of one phase. In the second section, the frequency of particle contacts is related to the degee of continuity of a randomly embedded phase orz the basis of the lattice-percolation model of Hamrnersley and others. THE extent of continuity of the constituent phases may greatly influence the structure-sensitive properties of phase mixtures, particularly if the phase properties differ significantly. An example from the literature1 is shown in Fig. 1. The marked decrease of the electrical resistivity of sintered silver-alumina bodies near 25 pct by volume of silver presumably occurs because the more conductive phase changes from a discontinuous to a continuous structure. Other example of electrical- and thermal-conductivity transitions are cited by kingery In view of these observations, a knowledge and understanding of the connectivity of the microstructure may be of considerable practical importance. This study is concerned with one aspect of the genera1 problem, namely the estimate of the degree of continuity of a particulate phase dispersed in an opaque matrix. The first section reviews the parameters measurable on a polished cross section by auantitative metallography, such as the contact area and under certain conditions, the number of contacts between particles of one phase. In the second section, an attempt is made to relate the frequency of particle contacts to the degree of continuity of a randomly embedded phase. For the purpose of this discussion, the aggregate has two constituents: the particulate phase and the matrix. The latter is considered to be homogeneous. The term "particle" is used with the meaning of "grain", i.e., a minute unit of matter which is usually a single crystal of a readily distinguishable substance within the confines of a simply connected boundary. While many of the concepts which are used here to describe the structural variables characterizing the microstructure of phase mixtures are qualitative and ill-defined, they are presented with the intent of stimulating further work of a more general and rigorous nature. I) PARTICLE CONTACT, CONTIGUITY, AND MEAN FREE PATH 1) Measurement of Contiguity. The fraction of the total internal surface of a phase a shared with particles of that same phase in a two-phase mixture of and $ is indicated by the contiguity ratio:3 whereis the area of the interface between o particles, and Sap is the area of the interface between a particles and matrix P, per unit volume of mixture. The contiguity ratio ranges from 0 to 1 as the distribution of the a phase changes from a completely dispersed to a completely agglomerated structure. The interfacial areas may be obtained from simple intercept measurements on a random plane, after Smith and Guttman where and N are the numbers of intercepts between a random line of unit length on a plane of polish and the interparticle and interphase interfaces, respectively. The equations are valid for any distribution of particle sizes and shapes.

Jan 1, 1967

By W. F. Tanner

A river delivers a given load of sand, and hence heavy materials, into the sea. The load is fixed by drainage basin characteristics and processes. Wave energy available for redistributing that load is fixed in an entirely different way. An equilibrium diagram of these two parameters (load vs energy) pennits a tentative prediction of what will happen to the heavy minerals. Alluvial rivers transport a mechanical load which consists essentially of wash load (finer than about 0.05 mm in particle diam), bed load (coarser than about 0.10 mm) and the transition sizes in between. A few rivers carry no appreciable mechanical load, and are excluded from this discussion. An example of the latter is the Suwannee River of Florida, which empties across an oyster bar into the Gulf of Mexico and does not build a delta despite the absence of significant waves or currents in that part of the Gulf. An alluvial river may deliver its load into a protected sediment trap (such as an estuary, sound or lagoon), onto a low-energy coast (where it builds a delta) or onto a high-energy coast (from which spot the river load is swept away). The nature and disposition of the load depends, obviously, on three sets of factors: 1) drainage basin characteristics and processes, which determine quantity and make-up of the load; 2) coastal structure and geomorphology, which determine the kind of river-sea coupling which

Jan 1, 1962

By G. L. Corrigan, J. R. Coleman

Four factors that largely determine the end product obtained when cement and water are mixed are the chemical compo ition of the cement, the fineness to which the cement is ground, the amount of mixing water used, and the procedure used in mixing the slurry. In order to study the effect of two of these factors, the other two, the chemical composition and method of mixing, are kept constant, leaving as variables fineness and water-cement ratio. Through years of experimentation and usage it has been well established that the reduction of cement clinker to a very fine state by grinding improves its cementing value, principally because the reaction between cement and water takes place only at the surface of the cement particle, further action being hindered by the accumulation of reaction products that tend to coat the unreacted material. Therefore, the more finely ground a cement, and the greater the surface exposed in proportion to its mass, the more rapid is the hydration rate. Similarly, the greater the surface exposed, the greater the proportion of the cement that reacts, and the lower the amount of residue that is unreacted and so remains inert and unable to make any contribution to cementing properties.1 Although it is more expensive to manufacture a finely ground cement than a coarser cement, the advantages of fine grinding of construction cements were so marked that the fineness of cement has increased considerably in past years. When the manufacture of special oil-well cements was begun, it was necessary to consider properties of cement that previously were considered of minor importance, foremost of these being pumpability. Since, with the water-cement ratio constant, a finely ground cement will produce a neat slurry of higher consistency and shorter time of pumpability than will a coarser cement, there is a tendency to grind oil-well cements to a lower degree of fineness. Therefore, in order to produce oil-well cements that will make a slurry having a long time of pumpability, cements are manufactured that because of their coarseness generally are poorer cementing materials than some of the more finely ground construction cements. On the other hand, often it is necessary to pump oil-well cements for long periods of time to place them properly behind a string of casing in a deep well, and since high strength is not of foremost importance for such cement, there is room for considerable controversy concerning the proper fineness range.

Jan 1, 1941

By Roy C. Kirkman

It is with great pleasure that I read Mr. Howard M. Wells article in the December 1978 issue of MINING ENGINEERING entitled: "Optimization of Mining Engineering Design in Mineral Valuation." Mr. Wells very adequately presents the case and point that there are a great number of variables which must be analyzed during an economic evaluation of an FUND RESOURCE, such as copper or uranium.

Jan 4, 1979

By L. S. Panyity

The Cleveland (0.) gas pool described by Frank R. Van Horn,' is the northern extremity of the great "Clinton" sand gas development in Ohio. Numerous gas pools have been developed in this formation, which are now more or less connected, link by link, forming an almost continuous gas pool, starting at Cleveland, and running thence southward through Cuyahoga, Medina, Wayne, Ashland, Richland, Knox, Licking,

Jan 1, 1918

JAMES ASHWORTH, Livingstone, Alberta, Can. (written discussion*).-About the year 1878, the writer commenced to experiment on safety lamps, the results of which will be found in the Transactions of the North of England Institute of Mining and Mechanical Engineers 1879-1880, the Transactions of the Manchester Geological and Mining Society, and in the technical press. He has also made a careful investigation of the flame caps produced by chemically prepared methane when mixed with air in accurately measured percentages. Before the conclusion of these experiments he personally fitted the hydrogen gas test to a special pat-tern of the Ashworth-Gray patent safety lamp. Later, as pure hydrogen gas was not always available, the writer constructed a safety lamp that would separately burn oil and alcohol; and still later, a somewhat similar lamp to burn alcohol only for specially testing low percentages of methane. This lamp was known As the Ash-worth alcohol safety lamp.

Jan 12, 1919

By M. R. Geer, H. F. Yancey

John Grifien (Pittsburgh)—I wish to congratulate the authors on this paper, which, I am sure, will promote a clearer conception of the various criteria which have been advanced as measures of coal-cleaning performance. Their clear descriptions of the more important criteria that have been advanced and explanations of their meaning and application have been sorely needed and, if widely promulgated and followed, should remove much of the confusion which, heretofore, has been evident. I suggest that much of this confusion has also arisen from lack of common agreement as to the exact meaning of the words and terms used in our discussions of this subject. I am sure I have been equally guilty in this respect and suggest it is time that we select a committee to study vocabulary as well as criteria, so that common understanding and agreement can be had. Thus, I suggest, that the title of this paper should have used the words "coal-cleaning performance" and not "coal-washery performance." My understanding is that "washery" refers to a complete plant and it has additional functions to that of coal-cleaning, such as control of size, moisture, etc. Also, I do not agree with the authors that the formulas given in their paper, the Fraser and Yancey formulas, are necessarily the only ones that can be called efficiency formulas. When a dictionary is consulted one realizes that the words "efficiency" and "efficient" have not precise meanings but only very general ones and must be further defined for each particular use, if they are to have any precise meaning. To my mind, the first of the Fraser and Yancey formulas given should never be used as expressing "efficiency" alone but only by the fuller phrase which truly expresses the kind of efficiency it states, which is "coal recovery efficiency." For complete clarity we then need only define "coal" for the particular circumstances under which the formula is used. This would recognize the fact, fully explained by the authors, that the limits in coal qualities imposed by the market have imposed a factor—and a variable factor—which has influenced any answer obtained by this formula. Such a procedure makes it entirely practical and logical to use the values of any of the qualities of coal—ash, sulphur, phosphorus, specific gravity—or a combination of them to define what is coal for that particular use of the formula. Further, it is clear to me that the criteria to be used must be dictated by the objective in view and the use for which the data are obtained. The authors clearly point out that the Fraser and Yancey coal-recovery efficiency formula is influenced by three factors, "one is determined by the coal, one is dictated by market or use conditions, and one is an inherent characteristic of the cleaning unit itself." The formula which uses the inverse of misplaced material as a measure of efficiency is also a coal recovery efficiency formula and is influenced in like manner by these three factors. As the authors point out, both are useless in obtaining data which enables a direct and valid comparison of the performance of a given cleaning unit on two coals where the other two factors vary or of the performance of two or more cleaning units of different types unless the values of the other two factors are identical. Much of the confusion in our discussions of and literature on coal cleaning has come from failure to understand clearly this fact. Many such comparisons have been made from which erroneous conclusions have been drawn. I am, therefore, particularly glad to see the authors' emphasis on 4?-1e criteria which indicate the "sharpness of separation. I feel that these are the essential criteria

Jan 1, 1952

By J. C. Griffiths, D. W. Bennion

A mathematical model, which does not assume a priori that stratification exists, but was designed to test for the stratification was developed. The model segmented the reservoir horizontally into areas of common variance, then divided it vertically into strata (if strata were present). Next, trend surface techniques were used to determine the lateral extent and variation of each stratum. The model was tested on two reservoirs (sandstone and limestone) using porosity as the reservoir rock property. The sandstone reservoir contained approximately 60,000 samples from 2,000 cored wells, while the limestone reservoir had approximately 24,000 samples from 430 cored wells. Within the areas of common variance tested, the model was able to distinguish four separate lithological units or zones in the sandstone reservoir, four in the Marly section and seven in the Vuggy section of the limestone reservoir. INTRODUCTION To accurately predict the movement and production of fluids from a reservoir rock, it is necessary that the reservoir engineer have a knowledge of the rock properties and their distribution throughout the reservoir. For this study, a reservoir rock is defined as a solid containing interconnecting holes or voids which occur relatively frequently and are dispersed within the rock in a regular or random manner. The fraction of bulk volume that these interconnecting voids occupy is called porosity. The rock must also possess sufficient permeability to allow fluids to move through it and it may be composed of one or more strata or lithological units. A stratum or lithological unit as defined in this study is a body or volume of reservoir rock whose properties are so distributed that its lateral and vertical extent can be traced throughout or through a portion of the reservoir. Operationally, the existence of strata are question- able unless the variance within strata is less than among strata. Within the past few years computers have been widely used as a tool for calculating movement and production of fluids from reservoirs. Most prediction models require some type of a mathematical description of certain reservoir rock properties. In the past, most of these models have been relatively simple. Some have assumed vertical variation but no lateral variation, while others have assumed lateral variation but no vertical variation. In general, most of these models have not used functional relationships to predict reservoir rock properties as functions of position. The object of this study was to develop a model which would predict lateral and vertical variations of reservoir rock properties. Since samples are usually available from only a small portion of the total reservoir rock, it seemed logical that if measurements from these samples were to be used to infer the properties of the actual reservoir, the data should be treated statistically as a sample from the total population (reservoir). Therefore, the model developed in this study to predict reservoir rock properties was a stochastic model. The model was tested using porosity (a macroscopic reservoir rock property) measurements from two reservoirs — the first, a sandstone reservoir from which 60,000 samples were obtained; and the second, a limestone reservoir with 24,000 samples. Several investigators have proposed methods to determine the vertical and areal variation of a reservoir rock property. Stiles: Dykstra and Parsons 2 and Suder and Calhoun3 have all developed waterflooding prediction techniques which assume vertical variation but no lateral variation. Stiles developed a method to segment a reservoir arbitrarily using frequency distribution. Law4 suggested that porosity has a normal frequency distribution and that permeability has a log-normal frequency distribution. Elkins and Skov 5 proposed that when a reservoir is segmented vertically, the

Jan 1, 1967

By H. W. Turner

In addition to the deposits mentioned by Mr. Lindgren? the following may be noted: 1. In the " Dardanelles quadrangle," of the map of the U. S. Geological Survey, 3 miles NW. of Tower Peak, there is a considerable mass of quartzite, marble, and dark, fine-grained. gneiss. At the edge of the coarsely crystalline white marble, having a width of about 400 ft., is a white schistose rock, which,

Jan 1, 1904

By D. T. Peters, C. R. Cupp

Aging of commercial 18 pct Ni maraging steel and of related binary, ternary, and quaternary alloys has been studied by electrical resistivity, X-ray diffrac-tion, and hardness measurements. The aging process is in three stages: 1) recovery of martensite; 2) two precipitation reactions; 3) formation of nickel- rich austenite. The main objective of this work was to discover the nature of the Co-Mu interaction. Addition of cobalt to the Fe-18 pct Ni-5pct Mo alloy results in acceleration of the pvecipitation reaction by increasing the super-sat~lration 0f molybdenum. The cobalt-containing al- loys show no incubation period for the precipitation reaction, but the alloy without cobalt shows an initial slow reaction. These results are interpreted in terms of precipitation on dislocations. At low aging temperatures, the presence of cobalt leads to the appearance of a second type of precipitate which is a particularly effective hardener. Cobalt was found to retard the formation of austenite. Overaging is a combination of classical overaging and the formation of austenite in the structure. he- activation energy for the precipitation reaction determined from resistivity ,measurements is 42.8 kcal per mole and the growth of the precipitate is found to obey at law at high tenzperatures and a tU3 law at low temperatures. HE mechanism of strengthening of the 18 pct Ni maraging steels has been studied extensively since 1962.'-? The strengthening is due to precipitation hardening of the martensitic matrix. The main precipitate is an inter metallic compound involving molybdenum, but there is disagreement about its identity.

Jan 1, 1967

By S. Razi

Injection luminescence of single crystals of rare-earth-activated CdS was investigated. Crystals of CdS:Nd, CdS:Er, and CdS:Yb, grown by the vapor transport technique, were suitably etched and hetero-junctions of Cu2S-CdS were fabricated on one side of the CdS substrate by chemical reaction. The device was then heated to 200°C in an inert atmosphere for 5 min. Static V-I measurements show that at low voltages (V < 1 v) the current is controlled by the junction, while at higher voltages the bulk Properties of the CdS substrate effectively control the current. Because of the large thicknesses no negative resistance was found. Reverse breakdown voltage varied from 5 v, for junctions that were not heat-treated, to 100 v, for diodes that received the proper heat treatment. The rectification ratio, measured in the range of 2 to 10 v, varied from 300 to 3000. Capacitance- voltage measurements indicate a weak dependence of the junction capacity on applied voltage. The capacity was found to increase appreciably with room light illumination. The variation of capacitance with frequency is indicative of a p+-i-n structure. An open-circuit voltage of 0.4 v was measured under an illumination of 100 mw per sq cm. Under forward bias, the bluish-green edge emission characteristic of CdS was observed. No sharp rare earth emission line was observed, which is in contrast to our results using ZnS:Tb, where, under high-voltage excitation, the rare earth emission was dominat over the lattice emission. The absence of rare earth emission implies that either the nature of the rare earth ion is different at the het-erojunction than in the bulk or the probability of energy transfer to the rare earth ion is small. RARE earth elements are playing an increasingly important role in the Synthesis of materials for a variety of purposes, e.g., solid-state lasers, color television screens, and so forth. Interesting systems result when wide-band-gap photoconducting lattices are activated with rare earths. A study of the lumines-

Jan 1, 1969

By Robert Parker

Measurements of the latent heat of transformation from a to 0 titanium were made using a pulse-heating technique. Rapid heating was accomplished electrically by discharging a low-inductance capci-tor hank through a thin-strip specimen. Both high-purity titanium and titanium containing 2700 ppm of 0 were studied. An electrical-resistivity technique and a plot of energy input us temperature rise were used to monitor the phase change. It was concluded that: 1) the latent heat of transformation is 800 i 48 cal per mole; 2) phase change occurred in less than 200 sec; and 3) the percentage phase change that occurs is linearly a function of the energy available for phase change. In addition, this experiment provides a simple and inexpensive method for determining specific heat of electrical conductors over large temperature ranges. The chief advantages of this technique over past pulse-heating experiments are: 1) static measurements of capacitor-bank voltage capacitance and specimen resistance can be made quickly and accurately to determine the energy supplied to the specimen; 2) the specimen is heated so rapidly (10 µ sec) that there is no appreciable heat loss during the heating. THE purpose of this paper is to illustrate the use of the capacitor bank as a tool for basic experimental investigations and to determine the rapid phase-change kinetics of titanium. The capacitor provides a number of unique properties: 1) rapid heating rates in the order of l09oC per sec can be obtained; heating rates as slow as l04oC per sec are available by merely adding a given amount of inductance to the circuit; 2) the energy input can be precisely determined and can be varied from several joules to millions of joules, depending on the bank capacitance and voltage; 3) the specimen can be heated uniformly through the thickness and length or non-uniformly, as desired; 4) the apparatus is simple and inexpensive and can be easily altered; 5) the form of the specimen can be wires, sheets, foils, rods, and cylinders; 6) there is great precision in the timing of events; 7) this technique may be readily used in conjunction with rapid cooling.

Jan 1, 1965

By M. R. Geer Olds, H. F. Yancey

.I. S. Huckaba (Western Machinery Co., Spokane, Wash.)—It has been my pleasure and privilege to be able to follow this work with the H.M.S. pilot plant very closely. This has been a very thorough and painstaking piece of work and will be of great value to the dense-media operators and manufacturers. Unfortunately time was not available to make an accurate comparison between this pilot plant and the commercial plant at Bellingham Coal Mines, both plants having Wemco drum separators. Briefly I would like to point out what I consider the most interesting finding of this work. Capacity: Very good results were obtained at a feed mte of 5.2 tons per hr in a 30-in diam by 24-in. long drum separator. The maximum capacity of this drum is not known but it is something over 5.2 tons per hr for the available area of 2.08 sq ft. Medium Preparation: The importance of proper medium preparation is well demonstrated. A "tailored" or

Jan 1, 1954

By M. Muskat, H. H. Evinger

A METHOD of calculating productivity factors for oil, gas, and water systems in the steady state is presented as an illustration of the quantitative application of the fundamental data on the flow properties of heterogeneous- fluid systems. While the numerical results of the calculations cannot be applied directly to field conditions, because they are based on permeability data for unconsolidated sands and involve specific assumptions regarding the nature of the reservoir fluids, the methods of analysis and interpretation should have significance in considering certain specific field situations when the necessary field and laboratory data become available. Moreover, it is felt that even under the idealized conditions to which the numerical calculations refer they should serve to give at least the orders of magnitude of the effects of gas-oil ratio and connate water on observed productivity factors. Within the indicated limitations, the computations imply that the foregoing factors can explain only a part of the apparent discrepancy between the homogeneous fluid productivity factors and those obtained recently in field measurements on the West Coast.

Jan 1, 1942

By Adolf Gurlt

It has long been known that minute quantities of foreign substances, when alloyed with steel, are capable of materially altering its physical properties. Thus, half a century ago, Faraday and Stodart, in England, discovered in the famous Indian steel, known as " wootz," small quantities of aluminum, from 0.0728 to 0.693 per cent., and attributed its extraordinarily good quality to the presence of such minute quantities of that metal. Since aluminum is now produced by electrolytic means on a large scale and at low cost, its addition to cast-steel has been frequently recommended of late. Chromium was alloyed with steel fifty years ago by the celebrated French metallurgist, Berthier, of Paris, and has recently been successfully applied to the same purpose by Holtzer, of Terre-Noire. In 1860 titanium was alloyed with crucible steel by Robert Mushet, of Coleford, the alloy containing up to 0.50 per cent. of titanium, which was extracted from Norwegian ilmenite. The titanium-steel was much vaunted by him for its excellent qualities. Rhodium, a very rare metal of the platinum series, was maintained by Berthier to improve steel materially in strength and hardness. Manganese has always been held by Sheffield steel-melters to provide steel with excellent qualities, and this influence was quite recently investigated by H. M. Howe and L. Campredon. Nickel was tried as an addition by Berthier, not to speak of gold, silver and platinum ; and nickel-steel has recently been brought into prominence by J. Riley and others, who recommend it for its great strength and toughness, particularly as material for armor-plates.

Jan 1, 1894

By Fred D. DeVaney and

The coercimeter, as its name implies, is an instrument for measuring the coercive forcet of magnetic substances. It was developed by Davis and Hartenheim in the Special Studies Section, Metallurgical Division. A detailed description of this apparatus may be found elsewhere.2 The coercive force determinations of magnetic materials are interesting because of the relationship established by Gottschalk,4 who showed a linear relationship between the magnetization coercive force and the specific surface of comminuted particles. The value of this relationship in determining grinding efficiency has been shown by Dean.3 The determination of the surface contained in the subsieve sizes has always been a difficult problem for investigators. They made approximate measurements of the surface of coarse materials by sizing on screens, but for the determination of the surface of the sub-sieve sizes it was necessary to make detailed grain counts or elutriation tests, or to study dissolution rates. The technical literature contains many references to other methods for determining these surfaces, either by some special apparatus or by mathematical calculations based on distribution lines. Many of the methods are long and tedious, and the results of some, at least, are questionable. he turbidimeter gives quick results on ground cement. By using magnetite as the material to be ground, a simple determination of its coercive force by the coercimeter, requiring 10 minutes or less, can be transposed directly and accurately into units of relative surface. This subject has been pursued further by the U. S. Bureau of Mines in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Mo., and the following is a description of the results.

Jan 1, 1939

By Fred D. DeVaney and

The coercimeter, as its name implies, is an instrument for measuring the coercive forcet of magnetic substances. It was developed by Davis and Hartenheim in the Special Studies Section, Metallurgical Division. A detailed description of this apparatus may be found elsewhere.2 The coercive force determinations of magnetic materials are interesting because of the relationship established by Gottschalk,4 who showed a linear relationship between the magnetization coercive force and the specific surface of comminuted particles. The value of this relationship in determining grinding efficiency has been shown by Dean.3 The determination of the surface contained in the subsieve sizes has always been a difficult problem for investigators. They made approximate measurements of the surface of coarse materials by sizing on screens, but for the determination of the surface of the sub-sieve sizes it was necessary to make detailed grain counts or elutriation tests, or to study dissolution rates. The technical literature contains many references to other methods for determining these surfaces, either by some special apparatus or by mathematical calculations based on distribution lines. Many of the methods are long and tedious, and the results of some, at least, are questionable. he turbidimeter gives quick results on ground cement. By using magnetite as the material to be ground, a simple determination of its coercive force by the coercimeter, requiring 10 minutes or less, can be transposed directly and accurately into units of relative surface. This subject has been pursued further by the U. S. Bureau of Mines in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Mo., and the following is a description of the results.

Jan 1, 1939

By J. J. Rutledge

On Sept. 4, 1914, Mine No. 1 of the Union Coal Co., Adamson, Oklahoma, suddenly caved, entombing thirteen miners whose bodies were never recovered. The seam of coal mined, the Lower Hartshorne, averaged 5 ft. in thickness and dipped at an angle varying from 22" to 30n. The strata overlying the coal seam were sandstones and shales. The mine was worked by the pillar-and-room method, the rooms being driven directly up the dip of the seam. All coal was blasted off the solid. Rooms were turned on short centers and room pillars were thin and irregular, as shown in Fig. 1. Fig. 2 is a cross-section of the form; showing the mine workings. Some cracks had been observed on the surface, it is said, at least a month before the squeeze occurred, but the collapse of the mine workings came very suddenly. As is usual when squeezes occur on such steep dips and the pillars fail, the crush progressed rapidly down the dip until it reached solid coal; there was a line of break, or draw, over in the solid coal. Several well-defined cracks appeared on the surface, after the mine had squeezed, but there was no appreciable subsidence of the surface, the weight seemed to be thrown entirely to the dip. About one year after the squeeze, and after the workings of the adjoining mine, NO. 4, had been retimbered and made safe, the writer inspected the tenth north (right) entry, or lift, off of No. 4 slope, which was below and fairly near the lowest caved portion of mine No. 1. The roof shale was composed of thin layers, which had been bent in somewhat the same manner as the leaves of a book having flexible covers are bent when the book is folded or rolled up in the hands. Though the mine workings are immediately beneath the streets and buildings of the mining town of Adamson, business was not disturbed by the squeeze, so far as any subsidence of the surface was concerned. No surface monuments were available and no elevations were taken, but the mine workings had been accurately surveyed and traversed, and the streets of the town overlying the mine workings had been carefully platted on the mine map, so that it was possible to locate accurately the cracks on the surface.

Jan 1, 1923