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By H. Ries

In the marketing of mineral products, it is always highly desirable for both the producer and the consumer to be able to discuss things in a common language, and this can only be done if there are standard methods for expressing the properties of the raw materials. Having developed such a form of expression, the next step would be the making of specifications, which may serve as a basis for selecting raw materials. Considering the large number of non-metallic minerals that are used, there are not a few for which there are no standard laboratory tests to be used in determining their properties, or even standard specifications on which grades or market price may be based. Indeed in many cases the consumer simply requests the producer to submit samples, and rejects or accepts them without any explanation. Could the producer know in advance just what the consumer needed, time and money might often be saved. It appears to the writer that it is of the highest importance to devise standard laboratory tests wherever possible, as this enables the consumer to state definitely what he needs, and is of great assistance to the producer. It should also work to reduce misunderstandings and disputes. In the case of sands, we find that they show a wide variation in their character, ranging from those that are so coarse as to be of gravelly nature to those that are so fine that they might be classed as silt; and from very clayey ones to those that are practically free from clay. For this wide range of sands, we have a corresponding variety of uses, which are based mainly on the physical properties of the sand, although these are not always very definitely stated. The chemical composition need rarely be considered, if the sand is of siliceous nature. To determine and express these properties there should be standard tests, which are to be followed in all cases where the material is tested in the laboratory. The use of sands for foundry work (making molds or cores) is old, and it has been recognized for some time that the important properties to be

Jan 1, 1926

By J. M. Larkin

GOOD will is becoming recognized more and more as a necessary business asset, and a successful concern must have the good will not only of its customers and the public, but of its employees. Management -enlightened management-recognizes this and will go the limit to get it. Progress depends on cooperation, and in industry cooperation must be based on the acceptance by employ-ers and employees of some practical application of the principle that capital and labor are interdependent. Capital cannot exist without labor, and labor without capital is helpless. The development of each is depen-dent on the cooperation of the other. Confidence and good will are the foundation of every successful enter-prise, and these can be created only by securing a point of contact between employer and employee. We feel that one of the most effective agencies for promoting good will between employers and employees is through some well organized method of conference and have consequently adopted, to accomplish this, a plan of employee representation. The plan inaugurated by the Bethlehem Steel Co. about four years ago, which provides for the election by secret ballot of representatives by and from among the employees, has for its purpose three fundamentals; namely, to give the employees a voice in the determina-tion of the conditions under which they work, to furnish machinery for the prevention and adjustment of differ-ences between employees and management, and, so far as possible, to provide and foster continuous employment. The constitution and by-laws adopted take care of the detail in setting up machinery for the functioning of the representatives of both management and men, but the spirit with which the plan has been carried out and the results which have been accomplished are of far greater importance than the plan itself. The Bethlehem plan, which has been in operation since October, 1918, can no longer be classed as an experiment. The original by-laws provided for amend-ments and, as was anticipated, changes and improve-ments have been made from time to time by mutual agreement. The operation of the plan for over four years shows it to be fundamentally sound and that it must therefore be conceded a success.

Jan 2, 1923

By Cadwallader Jr. Evans

THE Hudson Coal Co. is an anthracite concern with 22 mines, employing, when operating full, something around 18,000 men. We have, there-fore, necessity for a large number of subordinate officials and for a considerable number of major officials, and we carry on two separate courses of training in our endeavor to develop these two groups. The one in which college professors will be most interested is that which we call our two-year course. A man to be eligible for it must have completed a college course at one of several institutions from which we regularly seek our men, but he need not necessarily be a graduate of the course in mining, although we have been giving prefer-ence to graduates of schools of mines. Each year we take a number of men from these col-leges, sometimes five, six or seven, and put them through this two-year course, which is carefully. laid out so as to give them experience in the various details of our business. A schedule of the typical two-year course laid out for a man who started in July, 1925 shows that he was employed in the mining engineering department first for a period of four months, then for six months in inside mine work, three months in the mechanical and electrical departments, two months in "preparation," which with us means the cleaning of our product for market, one month in the study of statistics, one month on transportation and safety, and seven months in loading coal at the face, working with a shovel, making twenty-four months in all. We started this training in 1915 and in the first year we gave six months in the mining engineering depart-ment. We have now cut that to four. We gave six months in inside mine work and have continued that. We gave four months in the mechanical department, which is now cut to three; five months in preparation, now cut to two; two months in statistics, now cut to one; one month on transportation and safety which re-mains, and we have added seven months in loading coal. This last class of work gives them experience with the miner at the mining face.

Jan 7, 1928

By S. B. Flagg

Advancement in the art of burning fuels for steam generation has been so marked and so rapid in the last 10 or 15 years that one may well hesitate to classify as unsuitable for stationary steam boiler firing any material having a fuel value. This statement should not be interpreted to mean that any existing boiler plant can successfully utilize any fuel with which it might be supplied. It does mean, however, that almost without exception it is possible to design and construct stationary boiler plants so that they can be operated with whatever coal is the economic supply therefor. In considering the subject of the use classification of coals, it must be recognized, first, that the suitability or unsuitability of a coal for certain uses or conditions may be largely a matter of opinion and, second, that as advancement in the art of burning fuels continues, fuels that may have been considered unsuitable may later be regarded as entirely suitable. This is well illustrated in the creation of a market for slack bituminous coal and for the finer sizes of anthracite that resulted from the development of mechanical stokers adapted thereto. Coke breeze is another fuel of which large tonnages were formerly wasted, that has now been found suitable for use in properly designed furnaces. Again, results that would have been thought quite impossible a generation ago are being obtained in steam boiler plants today with lignites of high moisture content and with coals of excessive ash content. It must, however, be admitted that oftentimes an existing boiler plant can be successfully operated with only a limited number of the coals that are available as possible supplies. We may briefly consider some of the more important factors that may affect the suitability of coals for such a plant. Insufficient or barely sufficient draft to meet peak steam demands is often a limiting factor, and the permissible frequency of fire-cleaning periods is another. In some cases, the action of the molten coal ash on refractory furnace linings prohibits or makes inadvisable the use of certain coals. Again, clinker conditions in the fuel bed or slag conditions on the boiler-heating surface may be much worse with some coals than with

Jan 1, 1930

By C. F. Willis

The time is no longer when a man can act as an independent unit; the appreciation of the interdependence of one man upon another has emphasized the importance of the social unit. Epidemics have made us recognize that even a man's health is not distinctly his own to control as he pleases. The physical examination of workmen previous to employment started with an effort to prevent the spread of tuberculosis, for tuberculosis may be detected in its early stages and cured. But it was soon found that many other diseases were detected and the saving of lives made possible. The physical examination does not mean the elimination of the unfit—on that basis it would utterly fail—but rather the measuring of a man's physical fitness and placing the man where he can do the best for himself, his fellow worker, and the company. Industry as a whole cannot expect to live up to the standard of physical examination set for the army, nor should it expect to do so, for in all branches of industry there are types of work that do not require the same amount of endurance as does army work, and the lacing of men with physical limitations in the work for which they are capable permits a higher average of physical fitness for the work requiring physical excellence. Objects of Physical Examination The objects of physical examination are: The early detection of illness, particularly at a time when a full restoration of health is possible; the protection of employees from infection caused by working in contact with contagious diseases; the discovery of a man's physical limitations, in so far as his possibility for rendering good service is concerned; assistance to the safety movement by eliminating association in hazardous occupations with men whose physical condition renders them likely to accident to themselves and others; and the lessening of time lost by sickness. Statistics issued by the United States Department of Labor show that 22.54 per cent. of idleness is caused by sickness, with an average number of 7.71 weeks idle; whereas only 1.66 per cent. is caused by acci-

Jan 1, 1920

By B. Fernow

The question of preserving the forests in this country is an impor tant one, not only to trades using wood but to the whole nation, and though agitated for many years has not received that general consid eration which its broad bearing demands. Those who are interested in and working for reform in the treat ment of American forests are looking to the government for help, suggesting the creation of a commission to study the conditions of forests at home and abroad, and hope that a sound system of manag ing the woodlands will be thereby inaugurated. This reform will cost time and money, all the more because the government can bring to bear upon private owners hardly any power but that of good example and encouragement. There is, however, another aspect of the question to which I wish to draw your attention, namely; the more economical use of the valuable material which our forests offer, a more careful and ex haustive utilization of its constituents in all cases where wood or its products are applied. The wasteful consumption of wood in the United States is in every way so enormous as to justify the statement that by merely adopting an economical husbandry in this particular the destruction of forests might be delayed for many years, while the neglect of this imperatively needed and immediately practicable reform deprives legislative remedies of much of their value. In this regard I wish to draw the attention of metallurgists, especially those who are in terested in the manufacture of charcoal iron, to a more economical and profitable use of wood in iron manufacture. For thousands of years of human history wood was the main, nay, the only material used for fuel. Mineral coal came into use only in the fourteenth century, and it is only recently that it has largely displaced its less carbonaceous predecessor as fuel. The art of concentrating carbon in the form of charcoal for easier transportation and readier use in distant places was, according to Pliny, known to the ancients long before Christ., and was practiced in all countries, especially in connection with the iron-manufacture.

Jan 1, 1879

By B. Fernow

(Read at the Philadelphia Meeting, February, 1878.) THE question of preserving the forests in this country is an important one, not only to trades using wood but to the whole nation, and though agitated for many years has not received that general consideration which its broad bearing demands. Those who are interested in and working for reform in the treatment of American forests are looking to the government for help, suggesting the creation of a commission to study the conditions of forests at home and abroad, and hope that a sound system of managing the woodlands will be thereby inaugurated. This reform will cost time and money, all the more because the government can bring to bear upon private owners hardly any power but that of good example and encouragement. There is, however, another aspect of the question to which I wish to draw your attention, namely; the more economical use of the valuable material which our forests offer, a more careful and exhaustive utilization of its constituents in all cases where wood or its products are applied. The wasteful consumption of wood in the United States is in every way so enormous as to justify the statement that by merely adopting an economical husbandry in this particular the destruction of forests might be delayed for many years, while the neglect of this imperatively needed and immediately practicable reform deprives legislative remedies of much of their value. In this regard I wish to draw the attention of metallurgists, especially those who are interested in the manufacture of charcoal iron, to a more economical and profitable use of wood in iron manufacture. For thousands of years of human history wood was the main, nay, the only material used for fuel. Mineral coal came into use only in the fourteenth century, and it is only recently that it has largely displaced its less carbonaceous predecessor as fuel. The art of concentrating carbon in the form of charcoal for easier transportation and readier use in distant places was, according to Pliny, known to the ancients long before Christ, and was practiced in all countries, especially in connection with the iron- manufacture.

Jan 1, 1878

By D. A. Bailey, F. L. Kadey

During recent years, expanded perlite has found extensive use in a wide variety of commercial applications. Specifications for a range of uses call for aggregates having different physical properties and requiring various types of processing. The mitre scopic examination of expanded aggregates in specially prepared thin sections has yielded important information regarding internal structure and can be a useful aid in evaluation of the product. Perlite is an acid volcanic glass containing from 2 to 5 pct combined water. When crushed and rapidly raised to a temperature of 1500° to 2100°F, the volatilization of the combined water, coincident with softening of the siliceous glass, causes the particles to expand or pop. Expansion of perlite to densities as low as 1-1/2 lb per cu ft has been achieved, although the normal range is from about 2.5 to 10 lb per cu ft. Low-density materials of this nature have found application in cryogenic insula- tions, insulating tile and board, plaster and lightweight concrete, soil conditioners, filter aids after comminution, and a host of other uses. The expansion of perlite may be controlled by a number of variables. Some of these are ore milling, furnace design, expanding temperature, use of preheating techniques, screen size distribution, and feed rate of the crude. For the specific intended uses, the art of perlite expanding has developed to the point that much is known about the effect of these variables on the end product. The requirements, however, for an aggregate to be used in plaster are different from those for an expanded perlite to be used in lightweight concrete or for cryogenics. In the study of perlite, many practical questions remain unanswered. One of the most important is, "why do some perlites make hard aggregates while others cannot resist crushing or compaction?" The usual tests and methods for evaluation of nonmetallic substances have been tried and have contributed their share to our knowledge. But chemical analyses, compaction resistance tests, screen analysis, etc., will reveal only a limited amount of information. The answers to these complex questions may well be found in an examination of the intemal structure of the expanded particle. Such questions and the ex-

Jan 1, 1962

By E. P. Pfleider, O. Rellensmann

For many years mine surveyors and exploration engineers have sought an accurate means of transferring meridian underground by using the gyro-compass. These efforts have generally failed, either because they were inaccurate or because the size and cost of the unit were prohibitive. During the past ten years, however, great strides have been made. Autonetics in California has developed a comparatively light-weight (100-lb) gyro-theodolite, and the Institute for Mine Surveying at Clausthal Mining Academy in Germany has developed an instrument that is accurate to within 20" to 30" of arc. Concurrently, Minneapolis-Honeywell has produced an astounding gyro, the size of a salt shaker, that weighs less than 0.5 lb and compares favorably in performance with the 50-lb gyros of conventional design. This unit, designed for missile guidance, should be adaptable for surveying small boreholes. Given the proper interest and approach from the engineering fraternity, excellent gyrocompasses could probably be available for accurate underground survey work at nominal cost within the next three years. Principles of the Gyro-Compass: The gyrocompass, used for 50 years as a navigational instrument in ships and aircraft, senses the turning axis of the earth and points out true polar north. It does this by employing the earth's rotation, the force of gravity, and the precession characteristics of a gyro. For further details the reader is referred to several excellent publications'"3 covering the principles and application of the gyroscope. The heart of the gyro-compass is the gyroscope, or rapidly spinning wheel, which rigidly maintains its angular orientation in inertial space. Free gyros employ universal joints to allow the wheel axle to maintain its rigid spatial orientation independent of base motion disturbances. Free gyros are independent of the earth's turning and are not north-seeking. Only as they might be initially oriented parallel to the earth's turning axis could any north indication be obtained. In practice, the free gyro tends to drift off its set position and lose its accuracy. The Sperry-Sun Well Surveying Co. instrument (5M in O. D.) is of this free gyro type. It is counterbalanced, however, against the rotational effects of the earth, so that orientation of the spinning axis will be maintained throughout the survey.

Jan 1, 1960

By C. S. Matthews, H. C. Lefkovits

The purposes of this study are (a) to determine the accuracy of a previously proposed method for calclrlating average reservoir pressure and (b) to find a method for estimating the shape of the drainage area of each well in a bounded reservoir. Both numerical and experimental methods are used to determine the pressure distribution and the location of drainage bounrlaries in idealized reservoirs at steady state. A number of photographs are included which show flowlines and drainage areas in reservoir models of various shapes. Results from these studies are then compared with those from the previously proposed method for calculating average reservoir pressure.' It is concluded that the previously proposed method is sufficiently accurate for most reservoir engineering purposes. In addition, some simple methods are given for estimation of .shapes of drainage boundaries. INTRODUCTION A method for the determination of the average Pressure in a bounded reservoir was previously developed by Matthews, Brons, and Hazebroek,1 and presented at the Petroleum Branch Fall Meeting in 1953.† In aP- plying this method, the reservoir was first divided into drainage volumes; second, the average pressure in each drainage volume was calculated; and third, these drainage volume pressures were averaged volumetrically to give the average pressure in the reservoir. It was shown that each well's individual drainage volume, at steady state, is proportional to the well's production rate; however. the question of how to estimate accurately the shape of these drainage volumes could not be answered. Furthermore, in calculating the average pressure for each drainage area, the actual drainage areas, which are in general quite asymmetric in shape, are replaced with one of the symmetric prototypes given in T.P. 3876. A question may then be raised as to how accurately the symmetrical figures depict the pressure behavior of the actual unsymmetrical drainage areas. The study reported on in the present paper was made in an attempt to shed light on the above questions. METHODS It was shown in T.P. 3876 that after a period of steady rate of withdrawal the rate of pressure decline becomes constant at every point in a bounded reservoir containing a single-phase fluid whose compressibility is small and constant and whose viscosity is con-

Jan 1, 1956

By H. N. Herrick

The flow characteristics of drilling muds, as described in this paper, and the method given for solving problems relating to the flow of these muds through pipe and accessory equipment, are based on a conception that drilling muds are plastic solids like paints or greases; not liquids. The data presented in this report have been obtained from studies of California muds, chiefly those used in the Kettleman Hills field, by the Producing Department of the Standard Oil Company of California. Although no claim of scientific exactness is made for the formulas and diagrams, since the data upon which they are based are not complete even for California muds, the method has proved to be a convenient means for estimating, closely enough for practical purposes, the pressures required to force muds at various rates through pipe systems in which-they are handled. Certain approximations have been made to simplify the procedures so that they can be used easily in the field. Viscosity and Shearing Strength of Mud For the purpose of this discussion a plastic solid is defined as a material in which no deformation or flow takes place when the material is subjected to shearing forces, until the shearing force reaches a value called the "yield point." With liquids, the smallest force will produce continuous deformation; that is, the yield point of liquids is zero. The difference between true liquids and muds is illustrated in Fig. 1, which shows rates of flow through a small tube under different pressures. The flow rate of the liquids is directly proportional to the pressure and that of the muds is not. The behavior of drilling mud does not conform in every detail with the definition of a plastic solid as given, because mud actually flows slightly at pressures below its yield point. However, for practical purposes the definition describes the condition adequately and has the advantage of simplicity. In order to make mud-flow calculations based on the theory that mud is a plastic solid, it is necessary to know the "yield point" of the mud, which hereinafter is defined by equation 1 under the caption "Viscosity

Jan 1, 1932

By John B. Dilwoth

This paper treats primarily of the valuation of developed coal properties by the method of capitalizing their estimated average future earnings. However, reference is also made to valuations of undeveloped coal lands and to various methods of appraisal other than by future earnings. Fundamental Valuation Principles Before discussing in detail coal property valuations, a few statements bearing on the general subject will be made to present certain of the writer's views on the question as a whole. 1. A certain property at a given time has but one true value. This is not universally admitted. The appraiser rather frequently finds that a coal owner has in mind three valuations for his holdings; one, the figure at which he feels they should be appraised for taxation purposes; another, the much higher one that should be used if a loan is to be negotiated on the property; and a third, intermediate between the other two, the price for which he would be willing to dispose of his holdings were they for sale. The last is usually nearest to the true value, and because this is so the statement is generally accepted that the fair value of such a property is the price arrived at by negotiation between a willing seller and a willing buyer who are otherwise disinterested. 2. Notwithstanding the foregoing, it is only very generally and approximately true that the proper measure of the value of a given developed' coal acreage is the unit or per-acre price for which one or more bodies of similar coal in the same district have been sold recently. To give a few reasons why such a measure of value can not be strictly applied, it may be noted: a. That sales are often forced by circumstances at times when the coal business is depressed and buyers can be found only for properties that are offered at figures far below their true value. b. That conversely, during periods of unusual prosperity, abnormally high prices are paid. Such conditions obtained several years ago when coal brokers, with very profitable contracts but no sure source of supply, were bidding against inexperienced or shortsighted operators for proper-

Jan 1, 1928

By Carl Zapffe

THE manganese ore reserves of Lake Superior, because of their location and nature, have recently achieved a marked degree of importance as compared with the world's manganese reserves. To appreciate fully the significance and the adequacy of this reserve, one should understand how such ores are used, where obtainable, the quantity used, possible avenues for increasing use or application, and the chemical and physical characteristics of the available ores. Only with that data at hand, is it possible to arrive at a convincing answer to the question whether the reserves of manganiferous iron ores are adequate to satisfy the annual demand of the presently known iron ores for the full life of the latter. That they should last is vital; and to ascertain whether they will last was the purpose of the present investigation, which marks the first attempt to study these Lakes Superior reserves. The Lake Superior region possesses and supplies the full assortment of iron ores needed for the conversion of ore into pig iron and steel ingots and castings. These ores are named bessemer; low-phosphorus and high-phosphorus non-bessemer, manganiferous and siliceous; and to include the term aluminiferous, would be in keeping with the most recent no men clature adopted by some dealers. About 35 or 40 years ago, perhaps less, most of the Lake Superior ore which is being used today was the material then considered either useless or too poor for immediate use; perhaps it was considered no more than a future reserve. An examination of the analyses of ores and the guarantees in the sales of those older times, convinces one that the opinions of those days must have been governed by only small differences in analyses. Some grades of ores used today in substantial amounts were used most sparingly only one or two decades ago. The relative quantities of the different ores used is ever changing; and, bit by bit, the metallurgy and the opinions are every changing and the prejudices against certain ores and practices decrease. This is unquestionably more pronounced for the manganiferous ores than for any other kind. If, when using the present data for manganiferous ores, we will only be

Jan 5, 1927

By J. L. Jernegan

IN this paper I propose to give a short and, I must confess, a rather incomplete description, as regards many details, of the process used in Chicago, Ill., for smelting the argentiferous ores of the far West, and shall confine myself in this description, principally, to the process used at the Chicago Silver Smelting and Refining Company's Works, known as the Balbach process, as all the other smelting works in that city follow the same method, with the exception of one, which has the Cordurié, process for the desilverization of argentiferous lead. In all, there are five silver smelting and refining works in and near the city of Chicago. The Chicago Silver Smelting and Refining Company's Works are situated at the little station of South Lynne, about seven miles south from Chicago. The plant at these works consists of one horizontal steam-engine, principally used for running the ore pulverizer, four reverberatory smelting-furnaces, connected by horizontal flues with a common chimney 85 feet high, three lead-softening furnaces, one so-called zinc or mixing furnace, one separating furnace or liquation hearth, one lead-refining furnace, three zinc distillation retorts, one English cupellation furnace, supplied with blast by a No. 3 Sturtevant blower, which is run by a small steam-engine having a vertical tubular boiler, and an assay office, in which there are two wind-furnaces of the ordinary construction, and also a small muffle furnace. The assay office is supplied with all the necessary apparatus and reagents for fire assaying. There are also a superintendent's office, various store-rooms for coke and charcoal, and for the preparation of fire-clay, etc. Recently a small slag hearth (Krummofen) with one tuyere, has been put up for the purpose of working over such slags as assay too high in silver and lead to be thrown away, of which there are large amounts. The principal ore worked while I was in the employ of the company was that of the well known Emma mine in Utah, and also small quantities of Colorado ore. The character of the Emma ore is well known to most members of the Institute. In consists principally of ferruginous mixtures of carbonate and oxide of lead, oxide

Jan 1, 1874

By R. W. Parsons

wben a displacement front encounters an isolated permeability heterogeneity, it will be perturbed. The details of this perturbation will depend on the beterogeneity size and shape, the Permeability contrast, and the mobility ratio. This paper deals with the displacement front behavior for one, simple, mathematically tractable model: a circular permeability discontinuity and unit mobility ratio. The progress of an initially planar front is shown for four permeability contrasts: k2/k1 = 0, 5/2, 2, m. The front distortion is more pronounced than streamline and isopotential distortion and it approaches a constant shape downstream from the discontinuity. INTRODUCTION The impact of reservoir heterogeneities on oil displacing processes depends upon the variation of the heterogeneous property (frequency distribution), its disposition (spatial distribution), and the inherent stability of the displacement mechanism.l The interplay of these factors plus the impracticability, if not impossibility, of describing a natural rock system in any detail makes exact displacement front movements difficult to determine. It is useful, however, to be able to qualitatively visualize what heterogeneities will do to a displacement front. In this respect certain simple models that can be treated analytically are of value. The following analysis will show the displacement front behavior for one such model. MODEL DESCRIPTION The flow field is two-dimensional and infinite in extent. The fluid flow is single phase, steady state and unidirectional at x, y = 2 m, or before insertion of the discontinuity. A circular permea- bility discontinuity is placed at the origin. Porosity and thickness are the same within and exterior to the heterogeneity. This is exactly the same model that was used by Greenkorn et al. to check analytically Streamlines as determined by Heie-Shaw flow models and finite difference computer techniques.2 FRONT POSITION CALCULATIONS The results of displacement front calculations are presented in Figs. 1 through 4 for four different permeability contrasts: k2/kl = O, %, 2, m. The times corresponding to the front locations are the Same for the 0 and cases! and for the 1/2 and 2 cases. The determination of front positions at various times is based on known analytical expressions for velocity potentials ().2 and stream functions ().2 These expressions are in terms of the x and y

Jan 1, 1969

By H. F. Yancy

PooR results in coal washing and in ore concentration are sometimes attributed to the shape of the particles in the feed. It is well known that the shape of a particle influences its rate of fall in water. This is evidenced by the value of the constant C in the Rittinger equation for the velocity V of settling in water, V = C-D(d- z ), where C has the following values: 2.73 for roundish grains, 2.37 for long grains and 1.92 for flat grains. This report, which is based upon data obtained during the course of coal-washing investigations conducted by the U. S. Bureau of Mines in cooperation with the College of Mines of the University of Washington, gives the results of a method or procedure of screening in which the particles are separated into three shapes and shows the deportment of these shapes when coal is treated on a coal-washing table. The method consisted in first screening the coal with Tyler standard square-hole sieves, followed by screening tests of each of these products with screens of rectangular opening. For this purpose Tyler "Ton-Cap" screens were used; each square-hole product was subsequently sized with two Ton-Cap sieves so selected that their shortest dimensions were approximately 75 and 50 per cent., respectively, of the opening of the square-mesh sieves. For example: A product which is through 8 mesh (0.093 in.) and on 10 mesh (0.065 in.) is screened on slotted sieves which have openings 75 and 50 per cent. of the 0.065-in. opening in one direction and an opening of not less than 0.065 in. in the other direction. For convenience in discussion, the particles retained on the first slotted screen are termed "cubical"; those retained on the second slotted screen are termed "prismatic" and those passing the second screen are called "flat." (See Fig. 1.) The square-mesh screens separate particles according to two dimensions, length and breadth; the slotted screens divide them further according to the third dimension, or thickness. Prismatic particles have a mass of about two-thirds, and flat particles of about one-half, that of cubical particles of the same square-mesh size. The screen-

Jan 1, 1931

By Jerry H. Service, F. L. Partlo

The following investigation was undertaken to develop a method for determining with reasonable accuracy the depth of overburdens of 100 ft. or less. Seismic methods seemed to offer good possibilities. The problem differed from that of the familiar salt-dome location in that the depth of overburden to be determined is much less than is encountered in oil prospecting. This means that a much shorter time interval must be measured with accuracy. Refraction methods seem at present to offer greater possibilities than reflection. The air sound persists for from 0.1 to 0.5 sec., because of echoes, and seismic reflections coming during this time are difficult to detect. A seismometer sensitive to vertical vibrations only offers possibilities and has been used here with some success. It is hoped that the application of this type of seismometer to reflection shooting in this region may be investigated still further. The apparatus used consisted of a carbon-button seismometer followed by a three-stage, transformer-coupled, vacuum-tube amplifier and a General Radio string oscillograph. Time marks are provided by a 1000-cycle, 600-r.p.m., synchronous motor provided with five spokes which intercept the light to the camera at 1/50 sec. intervals. This motor is driven by a two-stage vacuum-tube amplifier of 3 watt output, actuated by a tuning fork. The power supply for the seismometer amplifier is one 2-volt storage and one 45-volt B battery. The motor amplifier is powered by a 6-volt storage battery and 6 to 225-volt, 15-watt motor generator. The temperature-frequency characteristics of the tuning fork have been determined and for ordinary working temperatures the error in time that would be introduced is less than M millisecond for time intervals up to 100 milliseconds. The impact is produced by a sledge blow for surface distances less than 100 ft. and dynamite for greater distances. Two steel balls with wires attached form an electric circuit through a 1-ft. piece of railroad rail upon which they rest. When the rail is struck by the sledge the balls rebound, opening the circuit and indicating the time of impact by a break in the oscillograph record line as at A, Fig. 3. When dynamite

Jan 1, 1934

By G. St. J. Perrott

One of the important hazards in coal mining is the danger of ignition of explosive mixtures of methane and air or coal dust and air, or both, by the explosives used in blasting the coal. It has long been recognized that certain explosives are more dangerous than others in this respect. ' In America and abroad, government testing stations have been established for officially passing on the suitability of explosives for use in coal mines. In this country the Federal government is given no power to enforce the use of the approved explosives but merely publishes from time to time, through the Bureau of Mines, those explosives which have passed the tests necessary to place them on the list for use in coal mines. In spite of this lack of police power, the increase in the use of permissible .explosives since the promulgation of the fist list in 1909 has been rapid. In 1912, only 8 per cent. of the explosives used in coal mines were permissible; in 1925, this figure had increased to 25 per cent. While the past record of permissible explosives has been most gratifying, it is very desirable that we pave the way for further improvement in explosives and blasting methods by learning more about the mechanism of ignition of gas and coal dust by explosives. To this end a considerable amount of investigative work already has been carried out and a large amount yet remains to be done. It is the purpose of this paper to discuss briefly the effect of the characteristics of explosives and method of loading in the borehole on the liability of a blown-out shot to ignite explosive mixtures of gas or dust. For an account of the methods by which an explosive is tested for permissibility for use in coal mines, the reader is referred to Schedule 17-A of the U. S. Bureau of Mines. Safety Factor in Using Explosives The factors that affect the liability of an explosive to ignite gas or dust are already known in a qualitative way but quantitative data are

Jan 1, 1927

By Douglas W. Fuerstenau, Kalanadh V. S. Sastry

A mathematical model is developed for flotation in a countercur-rent column where continuously generated air bubbles rise through a downward flowing pulp. The model is based on the assumption of axially dispressed plug flow of both the liquid and air-bubble phases. An appropriate flotation-rate expression, which takes into account the changing concentration of solid particles on the bubble surface, is formulated and applied to the column flotation process. Although a complete solution of the resulting equations is not possible for the general case, solutions for specific limiting cases have been obtained. From these, it is possible to predict theoretically the dependence of the column performance on certain variables. Specifically, concentration profiles as a function of height in the column have been calculated for various values of the characteristic dimensionless parameters. The effect of axial dispersion on the perforance of the equipment is pointed out. In recent years, there has been considerable progress in delineating the fundamental physicochemical principles underlying the unit operation of flotation and in advancing methods for kinetic analysis and process modeling of flotation.' In general, nearly all such process research has been concerned with the analysis of conventional flotation equipment and circuits. From these investigations, the possibility of developing and designing flotation apparatus for more efficient separation appears limited with conventional equipment. How- ever, recently there has been an attempt to apply coun-tercurrent flow techniques to flotation in the context of a flotation column.- some of the results from pilot-plant studies2 indicate possibilities for success of this process at least in obtaining higher-grade concentrates though not higher recoveries. A flotation column operates on countercurrent principle in which bubbles continuously generated at the bottom of the column rise through the downward flowing slurry. A schematic diagram of the flotation column is shown in Fig. 1. The physicochemical principles of bubble-mineral attachment, using this flotation column, are essentially the same as those which prevail in conventional equipment, the only differences being in the flow patterns of the various phases. The salient operating feature of the column as compared to those of a conventional cell is that neither mechanical nor turbulent pneumatic agitation is employed. The column is

Jan 1, 1971

In the past few years the hydraulic aspects of rotary drilling have received considerable attention. It is generally recognized that accurate prediction of circulating pressures is desirable, particularly in those areas where a delicate pressure balance is necessary to prevent both blowouts and lost circulation. For calculation purposes the standard hydraulic equations for the pipeline flow of Newtonian fluids have been altered to facilitate similar calculations for non-Newtonian or plastic fluids.'.' This latter classification includes most colloidal types of drilling muds. Two properties: plastic viscosity, un, and Bingharn yield value, Y,, are commonly used to define the flow characteristics of a plastic fluid. These are commonly obtained with multispeed viscosimeters such as the Fann V-G meter.3 Normally these measurements are obtained at some surface temperature, and are not corrected to circulating temperatures for calculation purposes. This may result in considerable error, particularly in the laminar flow calculations which comnlonly apply to the drill pipe-borehole annulus. The purpose of this study was to investigate the effect of temperature on the flow properties of some water-base muds. A laboratory model Fann V-G meter was used for measurement of viscosities, yield values and gel strengths. An aluminum water jacket with O-ring seals was machined to fit around the mud cup of the Fann meter. All mud samples were prepared by thorough mixing in a Hobart mixer. Viscosity and gel strength measurements were made with the Fann meter using standard procedures. Flow properties of muds were studied at 80, 120, 160 and 180°F. The compositions of the test samples are given in Table 1. The typical effect of temperature on the flow properties of these drilling muds is illustrated by Fig. 1. It was found that plastic viscosity and apparent viscosity decreased with an increase of temperature. However, the curves were not linear, and did not appear to follow any definite trends or patterns. Yield point data showed much more scattering.' Since a usable method for predicting drilling mud flow behavior with temperature was desired, an attempt was made to find a simple relationship between these variables. The basic approach used by Havenaars for predicting the same effect on turbulent viscosity resulted in Fig. 2, which shows that