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By J. Ellzey Hayden

THE Cliffs Shaft mine of the Cleveland Cliffs Iron Co., located in the city of Ishpeming, Mich., is the largest producer of hard hematite ore on the Marquette iron range. The two shafts, A and B, lying 820 ft. (250 m.) apart on the east-west trend of the ore formation, were sunk in the early eighties, and, except for four years, have been steady producers of iron ore. Their location, on a hill overlooking the general offices of the company on the one side and the city of Ishpeming on the other, has made the shaft houses landmarks. In the spring of 1919, as the old wooden shaft houses had become shaky and out of line, and would soon be unsafe, it was necessary to replace them with the least possible delay. Three plans of construction were, therefore, considered: To replace the old shaft houses by somewhat similar structures made of wood; to use steel and radically change the design; or to build reinforced-concrete shaft houses outside of the wooden structures, completely enclosing them. The first plan was disapproved, because it is anticipated that the mine will have a long life and the proximity of other buildings makes the danger from fire rather great. Delay in receiving material, and the necessity for closing the shafts during erection, were other factors in the situation. The second plan was disapproved on account of the high cost of steel, slow delivery, and interference with hoisting during the period of erection. The presence near one of the shafts of a large bed of hard gravel suitable for concrete made, the cost of the third plan considerably less than the second, and little, if any, delay in hoisting was expected. Our expectations in this regard' were fully realized. Furthermore, the work could be done by unskilled labor, which was plentiful, and the erection could be quickly started. When the proposition was submitted to Mr. W. G. Mather, president of the company, he recommended that, on account of the prominence of the buildings due to their location, an effort should be made to combine in the design as far as practicable something of architectural beauty. Following his recommendation, the original plans were submitted to the

Jan 8, 1920

By H. W. Graham

AS these annual occasions in honor of Henry Marion Howe continue through the years, there is progressively less likelihood that the lecturer will have had personal knowledge of Dr. Howe. The present speaker is one of those who unfortunately had no opportunity to come under the inspiring presence of this great metallurgist. A review of Howe's work shows it to cover a comprehensive range of interests and to evidence an impressive richness of detail. Not only was Howe at home in the laboratory, but he was familiar with the processes of iron and steel making and had a real understanding of them writings include much that is descriptive of processes with a wealth of material that is becoming of increasing historical value. He recorded his studies of the theoretical aspects of processes and published at least two process classifications, one in 1890 that was lengthy and somewhat theoretical, and a second in 1906 that was more of a practical listing. Wide as Howe's field of interest was, it is significant of the circumstances of his time that he gave little consideration to raw materials or to their effect on iron and steel making processes. In 1933, Waterhouse, Howe lecturer for that year, presented a descriptive summary of the major steelmaking processes, and in 1946 Joseph discussed the blast furnace process. Otherwise Howe lectures have not dealt with processes as major subjects. In today's lecture, with no effort to describe the mechanical arrangements of iron and steel making facilities, it is proposed to examine the essential technological elements of the processes, to explore the inter-relation of these elements, and particularly to seek recognition and understanding of those factors which determine why certain processes are or are not used. The discussion of this lecture will deal with the major well-known large tonnage processes, with only such attention to processes of minor tonnage and special character as may be warranted for explanation by contrast. Subject to the errors of generalization and the short- comings of condensation involved in presentation limited to a single hour, it is proposed to examine broadly but intensively those operations which convert raw materials into steel. It is an innovation for a Howe lecturer to discuss the raw materials of the iron and steel industry, but the changing circumstances of passing years intensify the influence of raw materials on processes and require the metallurgist to be alert for the process adjustments that may become advisable or mandatory. For a half century the metallurgical processing of iron and steel has followed a surprisingly straight path, but this does not necessarily mean that there are no curves in the road ahead. Ages ago primitive man came to know iron in its metallic form, not only by the

Jan 1, 1947

By FREDERICK W. BRADLEY

MINING methods are evolved rather than devised; and the process is slow. The advance in no particular year is phenomenal, but progress is un- questionably being made constantly in several directions: (a) better adaptation to given conditions of various "systems" of mining; (b) better utilization of mechanical equipment ; (c) improvement in working conditions so as to promote the health, safety and efficiency of the workers. During the year 1930 operations were commenced at a number of important new mines. Methods adopted are not new, except in minor detail, but the fitting of methods to conditions is interesting, because, as the engineers presumably started from scratch, they have selected the methods that experience under similar conditions has indicated as being the best.

Jan 1, 1931

By A. M. Tweedy, Felix A. Vogel

Since the publication of Prof. J. W. Richards's paper on The Schumacher Briquetting Process,' this process has been in operation on a practical scale in two plants in the United States, and a few notes on the results obtained may be of interest. An experimental plant, consisting of a toggle press and a hydraulic press, was installed at Johnstown, Pa., together with the necessary bins and other equipment, and an attempt was made to briquette a mixture of Mahoning fines and blast-furnace flue dust, in a ratio of 7 parts of ore to 3 parts of dust. The results were unsatisfactory, in that the briquettes made were not hard enough to stand the severe handling to which they were subjected in the various transferences necessary between the press and the furnace. The trouble was due to several causes: First, the mechanical arrangement of the plant, which did not lend itself to a proper hardening and loading of the briquettes into the cars. Second, the irrrgular composition of the flue dust, as to both its lime and its fine coke contents. Third, the variability of the moisture content of the ore, and its viscosity when wet. Fourth, the ratio of fine ore to flue dust; that is, it was attempted to bind in too large a quantity of fine ore for the small amount of flue dust used. The first trouble could be overcome, and has been improved upon in the plant as it stands to-day. The second trouble was important, because of the small amount of dust used as a binder, and might have been easily removed by mixing the flue dust of the different furnaces, which, however, was never done. The third difficulty was more serious, but could have been partly solved, had it been possible to meet this along with the fourth difficulty, by decreasing the percentage of ore in the briquettes. It was proposed to do this, but it seems that the problem at the works in question is, primarily, to prepare Mahoning fines for reduction in the blast furnace, and only secondarily to use up the flue dust, and a solution along this line did not seem to be interesting.

Jan 1, 1914

By Danforth R. Hale, R. E. Blair

Minerals for electronic and optical uses divide easily into two sections: (1) quartz and (2) minerals other than quartz. Quartz Quartz, having a great usefulness discovered by the radio communication enthusiasts about 1918, has become a subject of amazingly expanded interest in the US over the past decade as a man-made mineral and a multimillion dollar crystal-growing business. An economic summary of the commercial growing of quartz crystals has a place in a handbook directed to the mineral engineering industry when it is remembered that quartz crystals have long been an important commercial mineral, and that the raw material for "cultured quartz"-that is to say, quartz crystals grown through the ingenuity of man-is still natural quartz. Nearly all the natural crystals come from Brazil. The larger pieces which meet rigorous standards of quality are used for electronic and, to a lesser extent, optical components. Smaller pieces and fragments are used for vitreous silica. The need for high quality material in quantity led to US government-sponsored research programs in the 1940s that have resulted in the factory growing of beautiful crystals of prescribed shape, size, and quality. The development of the cultured quartz crystal is typical of man's success in adapting the product of the mine to increasingly sophisticated uses. A remarkable achievement perhaps, but foreshadowed by experiments in 1908 by Giorgio Spezia (1908), an Italian geologist studying the relative effects of temperature and alkaline environment on the solubility of quartz. Modern radio equipment is most often controlled as to frequency by the presence in the circuit of a separately added "crystal"-the 1918 discovery responsible for the existence and growth of the quartz industry. The "crystal" is quartz, but this component is a carefully oriented and prepared slice from a crystal, but not a crystal as recognized by a rock hound or seen in a museum. How quartz operates to control frequencies is not a proper subject for a handbook on industrial minerals, and references should be consulted (Cady, 1964; Mason, 1964). Quartz belongs to that class of materials called dielectrics: those that do not conduct an electric current but permit electric fields to exist and act across them. Quartz shows the "piezoelectric effect," which means that when a quartz plate is mechanically deformed against its natural stiffness, one of its surfaces becomes negatively charged, the other, positively charged. When the plate is released from the stress quickly, the charges disappear as the plate regains its original shape, but because of mechanical momentum the plate deforms in the opposite direction (to a lesser amount) and the surfaces correspondingly become charged in the opposite direction. By coating the two surfaces thinly with metal and attaching flexible wires, these charges may be brought into an electronic circuit. If the surfaces are suddenly electrically charged by movement of current through the wires, the "converse piezoelectric effect" occurs -the plate deforms. Carry the thought further and it is realized that an alternating current flowing through the wires responds to the mechanical oscillation of the plate and is keyed to this oscillation. By controlling the thickness of the plate its mechanical vibration frequency can be varied through a wide range. One type of quartz plate, called the AT-cut, having a precisely defined orientation with respect to the crystallographic axes of the crystal, vibrates on a microscopic scale much as a book would deform when placed flat on a table and the top cover moved parallel back and forth with the hand. There are at least 17 other orientations which have been studied, some of

Jan 1, 1983

By M. R. Goldick

THE Roan Antelope concentrator was originally designed with a nominal milling capacity of 6000 tons of copper ore per day but this was subsequently considerably exceeded. In broad outline the plant consisted of two No. 30 McCully gyratory crushers for coarse crushing, five 5 1/2-ft Standard Symons crushers in open circuit for secondary crushing, ten No. 98 Marcy ball mills arranged in five sections, each two-mill section with primary and secondary Dorr classifiers for two-stage grinding. One stage of flotation roughing was followed by two stages of cleaning, all in airlift type pneumatic flotation machines, with the final concentrates filtered on Oliver drum filters. Tailing was thickened in a 250-ft Dorr traction type thickener before pumping to the tailing dam. Concentrating operations commenced in June 1931, on the completion of the first two ball-milling sections and output was increased during the next few months as the remaining sections were finished. From the start, very few technical difficulties were experienced but a number of evolutionary changes have been made as a result of operating experience and the availability of improved equipment. These have resulted in plant and ore-flow alterations although the general scheme of ore treatment remains substantially as before. The main changes to date were the installation of a new crushing plant at Storke shaft, some 7000 ft west of the original Beatty shaft; the completion of a two-stage secondary crushing plant; an increase of 20 pct in ball-milling capacity; a change-over from pneumatic to a mechanical type of flotation machine for flotation roughing; the reduction of flotation cleaning from two stages to one stage. ORE TREATED Typically the ore treated consists of metamorphosed shales and sandstones with shales as the principal mineral-bearing rock carrying chalcocite, bornite and chalcopyrite as the main copper minerals. Chalcocite predominated in the original eastern end of the ore body but there is a pronounced trend to an increased proportion of the copper-iron sulphides as mining proceeds westward. Although the ore can be described as soft, this advantage is offset by the extremely fine dissemination of the copper minerals which calls for a high degree of comminution of the ore (90 pct minus-200 mesh Tyler standard) to give a reasonably satisfactory separation of mineral from gangue. Latterly, there has been a tendency for the ore to become harder as shown by a reduction in the ball-milling rate from a previous figure of over goo tons per ball-mill day to the present output of some 800 tons. Chalcopyrite is not so finely disseminated and has also proved more amenable to flotation than chalcocite. Nonsulphide minerals are mainly the so-called oxides such as malachite, cuprite and melaconite with some chrysocolla and

Jan 1, 1947

ALABAMA Alabama City.-Eddy, L. Altoona.-Cain, J. America.-Foreman, J. T. Anniston.-Foster, R. N. Ashland.-Sturdevant, J. C. Bessemer.-Ball, E. M. Calhoun, F. W. Maschmeyer, W. L. McKenzie, W. C., Jr. Birmingham.-Abbott, C. E. Aldrich, T. H. Aldrich, T. H., Jr. Ashton, J. J. Aufderhaar, H. C. Ball, T. L. Biddison, P. M. Blair, C. S. Brown, T. S. Bush, M. W. Clark, G. H. Crawford, G. G. Crockard. F. H.

Jan 1, 1929

By Stuart E. Buckley

The application of hydrocarbon equilibrium data to various problems encountered in refining and in natural gasoline recovery is an old and well established practice. Both generalized data and data on specific hydrocarbon systems have been made available by a number of investigators. More recently such data have been applied to the relations governing the separation of oil and gas both in the reservoir and at the surface. Most of the applications to production problems, however, have been based upon examinations of surface samples of oil and gas. This paper describes a technique that has been used satisfactorily in a number of cases to calculate directly from the hydrocarbon analysis of and auxiliary laboratory data on a subsurface sample of the reservoir fluid the behavior of the oil and gas during the various stages of separation at the surface incident to production. Types of Information Calculated The system of calculations is not designed to supplant field data, but rather to correlate with them laboratory data obtained under controlled conditions in order to obtain a more complete and exact picture than usually is possible through the use of field data alone. The chief advantage of the calculations is the possibility of their use at a minimum of both time and expense to determine completely the effect of any possible operating technique upon each of the following: (1) The gas-oil ratio resulting from liberation of the dissolved gas; (2) the composition and gasoline content of the liberated gas; (3) the composition and gravity of the residual oil; (4) the amount and composition of the gas liberated upon flashing the oil from the separator to the stock tank; (5) the shrinkage of the oil in passing from the reservoir to the stock tank. This information is frequently essential to the correct determination of the advisability of installing a natural gasoline plant, to design such a plant to take care of seasonal production, and to determine the optimum separator pressures to carry in various parts of a field.

Jan 1, 1938

By M. Muskat, H. G. Botset, R. D. Wycoff, M. W. Meres

The subject of the flow of homogeneous fluids—gases alone or gas-free liquids—through porous media may be considered at the present time to be fairly well completed. That is, analytical, graphical, numerical, or experimental methods are now available for obtaining detailed descriptions of the behavior of such homogeneous fluid systems of any reasonable geometry. Thus, satisfactory empirical techniques are now well established for the determination of the permeability of porous media for homogeneous fluids, the numerical magnitude of this permeability uniquely and completely describing a porous medium as a carrier of a homogeneous fluid. Considering this constant as known, the treatment of a wide variety of specific problems involving either the flow of gases or liquids has been carried through to satisfactory conclusions. Beginning with the simple case of strictly radial two-dimensional flow of a liquid or gas into a well under steady-state conditions, generalizations have been developed to apply for systems where the flow is not strictly radial, due either to a lack of uniformity in the reservoir pressures at points distant from the well or deviations from circularity of the external boundary whereby the fluid is being supplied, and finally, to the lack of complete penetration of the well into the producing strata. Satisfactory descriptions are now available for cases where gravity is acting as the driving agent inducing the flow of liquid into the well, either alone or as a supplement to the effect of pressure. The effect of acid treatment on limestone wells has been given a reasonable interpretation on the basis of the fundamental theory of the flow of homogeneous fluids through sands, as have the important features of the problem of water-coning. Then, too, systems in which the outlet of the fluid from the underground reservoir is of a predominantly multiple character may be now considered as in the domain of

Jan 1, 1937

By J. W. Onuscheck

The oxygen-fuel oil burner lance is a very useful tool at the Monessen B.O.F. It increases the overall flexibility of the operation. An additional 15,000 to 20,000 ingot tons can be produced at a given hot metal supply. It helps overcome sporadic drops in hot metal thermal values and/or supply. It results in increased yield, in particular, on high carbon heats where much yield was lost on reblow triggered slag reactions. The burner has also been adopted as a standard tool to aid burning in new vessel linings. Overall, steelmaking performance has improved with the use of standard preheat practice. Scrap charges up to 50 percent have been used routinely in times of extreme hot metal shortages, but the performance is weak in some categories. Development of a single step oxy-oil process is in progress. In this process, scrap and hot metal are charged as in the normal B.O.F. practice, but fuel oil is fired with the refining oxygen.

Jan 1, 1972

By D. W. Fuerstenau

This paper presents the results of an investigation of the stability of the mass flow rates and average pellet size in the different streams of an industrial-scale balling circuit. The variables in this study include water content, drum speed, and fresh feed rate. It was found that both the mass flow rates and pellet diameter are greatly disturbed when a change, positive or negative, in any of the variables takes place. For most of these disturbances to be damped down, a period of 1 hr or so is required. When a disturbance in the feed rate was made, the transient period extended to more than 1% hr (the duration of the experiment). It was observed that there is an interaction between the drum speed and moisture needed for producing an acceptable green ball product. The moisture content of the product pellets was found to be a function of the pellet size, with the larger pellets retaining a higher moisture content

Jan 1, 1983

By William Victor Vietti

A METHOD of determining the average density of the fluid column in a flowing oil well is presented. Actual field data from several wells are used to illustrate the application of the method in the Yates Field, Pecos County, Texas. The depth of the wells in the Yates Field varies from 900 to 1700 ft. depending on surface elevation and the location of the wells on structure. Production rates over 8000 bbl. hourly have been determined and many

Jan 1, 1930

By Leon W. Dupuy

INTRODUCTION A BRIEF elemental discussion of the fundamental factors involved in diamond drilling often fills a need, particularly when a mine operator is contemplating for the first time an exploratory drilling campaign. Mr. James A. Barr, of the Mining Methods Committee of the Institute, has suggested that many engineers must undertake a drilling program of one kind or another and, in the case of diamond drilling, sometimes even are at a loss as to how to start correspondence. The Bureau of Mines has acquired much experience in managing exploratory diamond-drilling activities. Its activities in diamond drilling included exploring for potash in Texas, Utah and New Mexico 1-4 during the 1920's. The Strategic Minerals Exploration program was started in 1939 and was materially expanded during the war to include critical and essential minerals. At the peak of its war-time activity more than 200 engineers were employed, a majority of whom supervised diamond drilling. Many of them had little experience with such work prior to their employment with the Bureau, and it was necessary to instruct them in their duties. The purpose of this paper, therefore, is to present the fundamentals of exploratory diamond drilling from the viewpoint of management in such a way that they will serve as a basis on which those beginning exploratory diamond drilling may build an experience and acquire ability to direct exploration as they gain that experience. SELECTION OF METHOD OF DRILLING Selection of the method of drilling is governed by the type of material to be penetrated and by the type of sample needed to determine the quality and importance of a deposit. Types of drills that might be used for a given job include diamond drills, churn drills, hand auger drills, power auger drills, bucket drills, and rotary drills (sometimes called "seismograph rigs"). Each type has a specific field in which it is most useful. While the Bureau of Mines utilized all the types of drilling mentioned, diamond drilling was used on a majority of its exploratory projects. FACTORS GOVERNING SELECTION OF DIAMOND DRILLING The prime consideration in selecting a method of drilling is first to determine what results are desired and then to choose a method that will furnish reliable data in the ground to be penetrated. Use of diamond drills permits recovery of a core as well as sludge at a comparatively low cost. The core provides an excellent means of studying the formation being drilled and furnishes much information that would be difficult to obtain otherwise. Diamond drills will recover a satis-

Jan 1, 1947

By Francis M. Rice

Before the world-wide depression, the primary purpose of most blast-furnace operators was to produce a maximum tonnage of pig iron per day for each furnace in blast. Some attention was paid to the conservation of labor and raw materials, but the idea was well established that low-cost pig iron was attainable only when each furnace was producing a high tonnage. After the depression had set in, the picture changed considerably. Each blast-furnace operator was forced to run his plant in a manner that best fitted the economical set-up of his company. A great deal of thought was expended on the different methods of operation, always with the idea of making each product in a way that would best serve his company financially. Because of this abnormal condition, the blast-furnace man was compelled to indulge in various practices of which many had been believed to be next to impossible up to that time. The ultimate purpose of these innovations was either one or a combination of the following: 1. To produce only enough pig iron for immediate consumption at a minimum cost. 2. To produce gas for boiler or mill use to supplant some higher priced fuel. 3. To consume the coke produced at the coke plant, which was often viewed as a byproduct. 4. To protect the cash position of the company. These conditions were met by diverse methods, some of which were: 1. Slow or decreased wind. In some instances the blast blown was held as low as 25 per cent of the normal volume. 2. Intermittent operation, in which the furnaces were shut down or "fanned" at frequent intervals.

Jan 1, 1935

By Francis M. Rice

Before the world-wide depression, the primary purpose of most blast-furnace operators was to produce a maximum tonnage of pig iron per day for each furnace in blast. Some attention was paid to the conservation of labor and raw materials, but the idea was well established that low-cost pig iron was attainable only when each furnace was producing a high tonnage. After the depression had set in, the picture changed considerably. Each blast-furnace operator was forced to run his plant in a manner that best fitted the economical set-up of his company. A great deal of thought was expended on the different methods of operation, always with the idea of making each product in a way that would best serve his company financially. Because of this abnormal condition, the blast-furnace man was compelled to indulge in various practices of which many had been believed to be next to impossible up to that time. The ultimate purpose of these innovations was either one or a combination of the following: 1. To produce only enough pig iron for immediate consumption at a minimum cost. 2. To produce gas for boiler or mill use to supplant some higher priced fuel. 3. To consume the coke produced at the coke plant, which was often viewed as a byproduct. 4. To protect the cash position of the company. These conditions were met by diverse methods, some of which were: 1. Slow or decreased wind. In some instances the blast blown was held as low as 25 per cent of the normal volume. 2. Intermittent operation, in which the furnaces were shut down or "fanned" at frequent intervals.

Jan 1, 1935

By Albert Sauveur

AT the New York meeting of the Institute, February, 1914, Professor Hopkinson and Sir Robert Hadfield presented an important paper entitled Research with Regard to the Non-Magnetic and Magnetic Conditions of Manganese Steel.1 Any contribution on manganese steel by its discoverer necessarily carries with it much weight and is entitled to serious and close consideration. The momentous discovery of that alloy by Sir Robert Hadfield some 30 years ago was the signal for great activity in the field of alloy steels; and the remarkable results obtained in the last two decades probably constitute the most important modern advance in the metallurgy of steel. The authors of the paper referred to above are unable to reconcile with the allotropic theory the interesting results obtained by them in heat treating manganese steel. When they speak of the allotropic theory, however, I understand that they have more especially in mind the existence of beta iron. It is not my understanding that they question the occurrence of iron in the two allotropic varieties known as gamma and alpha. If I am wrong, I trust they will correct me. A careful consideration of the experimental results reported and discussed by the authors leads me to believe that on the contrary they can be very satisfactorily explained in terms of allotropy and that, in the light of our present knowledge, they cannot be accounted for in any other way. The physical properties of non-magnetic manganese steel described by the authors are those pertaining to iron-carbon alloys in which iron is present in the gamma condition, or, in other words, to austenite. The metal is then characterized by great tenacity and ductility and low elastic limit, while its hardness, mineralogically speaking, is not excessive, but of a special kind termed "tough hardness" by the authors. Even when subjected to the restraining influence of a large amount of manganese and of considerable carbon, however, relatively rapid cooling

Jan 9, 1914

By Hans Lundberg

IN ORDER to comprehend the help and information that may be expected from electrical prospecting, it is necessary to have at least a general knowledge of the methods and principles involved in preparing and interpreting results obtained in the field. Electrical prospecting is rather complicated, both in theory and practice, and in order to make a brief description clear to the practical mining man it has been necessary to idealize and generalize the problems, at the risk of having such simplification criticized by the theoretical man. This simplification must not be misinterpreted as showing a lack of theoretical knowledge. FIG. 1.-FLOW OF CURRENT IN AND AROUND A CONDUCTING BODY. For its operation, electrical prospecting mainly depends on the fact that most metallic ores conduct an electric current much more readily than barren rocks. If an electric current flows through a block of ground within which a body of chalcopyrite is enclosed in country rock of schist, the current will find less resistance to its passage through the chalcopyrite than through the schist, even though the passage through the latter be much shorter. This is because the longer path through the chalcopyrite offers less resistance, owing to the superior electrical conductivity of the chalcopyrite (Fig. 1).

Jan 1, 1928

By Charles Burrows

THE burden a man can endure depends on its magnitude and the number of tunes it is applied, as well as on many other factors. The resisting power of steel likewise is dependent on many factors. The maximum load it can support indefinitely is much less than its possible momentary burden. A light load straining the metal far within its elastic limit, if repeated indefinitely, ruptures the metal. The magnitude f the stresses that may be alternately applied and removed without rupturing the material depends on the number of repetitions of the cycle; the intervening periods of rest; the thermal, electric, and magnetic conditions, as well as the presence of secondary stresses. While we are unable to formulate the law between the magnitude f repeated stresses necessary to produce rupture and the length of time during which these alternating stress may be applied before rupture, my experience is that the time increases as the magnitude of the force decreases, according to a law which, to a first approximation, is exponential. In other words, F = Ce-t where F = magnitude f alternating stresses; = time for which stresses are continued; C = constant, which' depends on the conditions under which the operations are carried out. It is quite probable that the same type of law holds for the magnitude of a continuous force and its duration. When a rod of steel is subjected to the blows of a drilling hammer several things happen. First, one end is struck by the hammer and the other end is driven into the rock, thus causing a bodily displacement of the entire material of the steel drill. The greatest stresses involved in this bodily displacement are located at the two ends of the steel and manifest themselves by the distortion of these parts. Second, after the blow has been delivered the steel drill, due partly to its own resiliency and partly to the resiliency of the rock, experiences a vibratory motion as a whole, this motion is quite similar to the bouncing of a rubber ball thrown violently upon a smooth pavement. Third, the free vibration of the drill is determined only by its own natural period of vibration. This motion involves all the characteristics f any vibrating body emitting sound. Certain elements of the rod will experience alternations of condensation and rarefaction and, in these regions, the individual steel

Jan 6, 1921

By J. D. Price, W. M. Bertholf

One of the chief difficulties with which the operator of a coal washing plant has been forced to contend is the handling of the very fine coal. First he has the problem of separating the fine coal from washery water. This is usually accomplished by the use of settling cones or Dorr thickeners: in either event the separated fine coal contains a high amount (40 to 80 pct) of water and, somewhat loosely, dependent upon the size of the coal particles present, may be known as sludge or slurry. His second problem is the satisfactory further dewatering of such separated sludge and/or slurry. At the coal washing plant of the Colorado Fuel and Iron Corp., washed coal from the Deister Plat-O tables is sluiced to a stationary inclined de-watering screen provided with 3/16 by 1-in. slots, and the coarse coal passing over this screen is conveyed by a Baum-type elevator and a flight-type distributing conveyor to a battery of Carpenter centrifugal driers. The fine coal and water passing through the openings of the primary dewatering screens, plus the fine coal passing through the screens of the centrifugal driers (and no small portion of which is the result of the disintegrating action of these driers) is pumped to two 30-ft Link Belt settling cones. The sludge recovered as underflow from these cones was formerly dewatered on stationary screens having 1/16 by 1-in. slots and discharged on top of the coarse washed coal in the Baum drainage conveyor; but after a relatively few hours of op eration the circulating load of fine coal on this conveyor built up to a point where it became necessary to reduce the quantity of feed to the washing tables. The original arrangement of our coal washing and dewatering equipment is shown in Fig 1. In order to regain the loss in active throughput which had been caused by this circulating load, an installation of six vibrating filters was made during the year of 1936. This resulted in an increase in normal tonnage of washed coal from 1430 to 1750 tons per 8-hr shift, a gain of slightly over 22 pct. This increase in throughput has made a very substantial decrease in the " conversion cost" per ton of washed coal. Since the vibrators were installed, we have gained about 2,000,000 tons in production, compared to what would have been produced in the same number of shifts at the former rate. Putting it in slightly different form, we have saved in the past 12 yr the cost of 1400 operating shifts in the washery. Fig 2 shows the location of the vibrating filters as applied to the original flowsheet. It will be noted that the sludge from the bottom of the settling cones is passed through a distributing box and thence to the filters. The de-watered coal from the filters is de-livered to the conveyor receiving the dried coal from the Carpenter driers.

Jan 1, 1950

By H. R. Peiffer, R. Geckle

The silver phase of silver and finely divided alumina composites is shown to grow as single crystabs upon solidification from the melt. These crystals grow without the aid of an externally applied thermal gradient or a mold. The single-crystal growth is more readily disrupted as the alumina content varies from the optimum concentration of 20 wt pct. Pretreatment such as variation of fabrication pressure, and presintering of the specimens appear to play a lesser role in this phenomenon. In actual practice the growth of single crystals of metals from the melt is a tedious, painstaking process.' Care must be taken to insure the proper thermal gradients and rate of growth in a vibration-free environment. Excellent single crystals can be grown when these variables are controlled. When a second insoluble and finely divided phase is present in the melt the growth of single crystals is difficult, if not impossible, even under the most favorable conditions outlined above. During the past few years, a composite of silver and alumina has demonstrated an ability to resist flow even though the major phase, silver, is mo1ten. 2 A more surprising feature of this material is the ease with which single crystals of silver grow upon cooling the composite from temperatures above the melting point of silver to temperatures near room temperature. Observations have been made that demonstrate that single crystals of silver will grow even when conditions most unfavorable for growth of pure silver crystals exist. The crystals grown in this manner are imperfect in that a great deal of subgrain structure exists. It is the purpose of this manuscript to qualitatively describe this process and to attempt to isolate the influencing factors of this behavior. MATERIAL PREPARATION The composite material is prepared by powder-metallurgical techniques. Two items of great importance are the introduction of oxygen into the system and the obvious need for a thorough mixing of the metallic and refractory oxide phases. The oxygen is necessary in order that the silver wets the alumina. Without oxygen the phases separate and the material shows no unusual properties. In order to supply the needed oxygen the silver is added in the form of silver oxide which is readily decomposed to oxygen and silver upon heating. The silver oxide is readily obtained in a finely divided form that allows a uniform mixture of the alumina and silver oxide to be prepared. The correct ratio of alumina to silver oxide is mixed in the presence of alcohol in an ordinary food blender. The mixture has the consistency of a thin slurry and after mixing for approximately 20 min is dried and pressed into billets at various pressures. As is shown in Fig. 1, there is no limit to the shape of the specimens obtainable as single crystals. These billets are heated in air in a predeter-

Jan 1, 1964