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By Ralph H. Kress

Haulage trucks designed expressly for mine service were introduced about 35 years ago. The first models to arrive on the scene hauled about 15 tons and easily outperformed the modified highway trucks that had been used for mine haulage up to that time. The specialized trucks obviously had a greater potential for mining operations, and once this fact was recognized, competitive pressures in both the mining and truck-manufacturing industries drove the new vehicles toward ever more efficient performance. Many changes in truck design resulted, but not all were accepted for a variety of reasons. Often poor design was the reason, but in many cases progressive and promising designs were abandoned only because the truck manufacturer lacked the courage, tenacity, or vision to capitalize on them. There were also many cases where a promising new design was abandoned because the prototypes were initiated in a mine where personnel lacked the patience to prove them. Truck Startup Takes A Team Ally new truck that is to succeed and contribute to lower mine haulage costs must be well conceived and launched with good teamwork on the part of all concerned. Naturally, it is essential to have a good overall truck design at the outset to make this teamwork worthwhile. The design must include the selection of the right components manufactured by suppliers that can each do justice to their particular part of the new truck. Last, but by no means least, the mine operator where the truck is to be launched must be enthusiastic in his efforts to see the new vehicle through to successful operation.

Jan 1, 1971

By R. P. Rothwell

A Reference to the geological map of Alabama shows the Goalmeasures of that State to form three distinct fields. The Coosu, or most easterly, contains about one hundred square miles ; the Cahaba, or middle field, which is also the most southern true coal in the United States, contains about 230 square miles ; and the Warrior field, which contains in the State of Alabama some 5000 square miles, is the southern extremity of the great carboniferous deposit, which extends through Pennsylvania, West Virginia, Kentucky, Tennessee, and Georgia. But very little has yet been done towards developing those coalfields, partly owing to the absence of all commercial manufacturing enterprise in the South under slavery, and partly owing to the want of capital and the disturbed condition of the South since the war. During the past three or four years I have devoted a large part of my time to the examination of the coal and iron ores of this range,

By L. S. Reid

THE study of the flow of oil and gas mixtures through oil-bearing formations has received special attention from the petroleum industry within the past few years, and has resulted in a series of research projects based upon various phases of the flow of heterogeneous fluids through porous media. Obviously, the low cost of producing oil during the flowing life of a well makes it desirable to obtain production by natural flow as long as possible and to effect a maximum recovery of oil and gas by the utilization of reservoir energy through efficient methods based upon a thorough knowledge of reservoir characteristics. Despite the extensive research that has been carried out, there is little information available on the behavior of oil and gas mixtures flowing through reservoir formations. This makes it impossible to predetermine the optimum operating condi-tions for flowing wells. A differential pressure must exist in the reservoir in order to induce flow toward the well. It is a well established fact that with homogeneous fluids the relation of pressure drop to linear distance traveled is a straight-line function as long as the flow is viscous. However, in regard to gas-saturated oils, a number of investigators1,3,4 have reported that the flow characteristics are materially altered as some of the lighter hydrocarbons are liberated from the oil to form gas while the fluid passes through the reservoir. Most of the work done has been concerned primarily with steady-state flow of liquid-gas mixtures. Cloud1 has studied the effects of saturating crude petroleum oils with various gases, together with the resultant pressure gradients under steady flow conditions, noting that unsaturated oils flowed faster and yet maintained lower pressure gradients than saturated oils.

Jan 1, 1938

Jan 1, 1901

By Frank E. Woolley, John F. Elliott

Mathematical models of the transient thermal behavior of a high-temperature solution calorimeter1-3 have been developed. The thermal behavior of the calorimeter is appoxirrzated by linear lumped-parameter models, and hence is described by sets of linear ordinary differential equations with constant coefficients The response of the models to various inputs is shown to agree with the response of the real system. Application of the modeling to experimental design and analysis of data illustrates the usefulness of simple models of complex systems. The early eperiments1,2 with the high-temperature solution calorimeter indicated that the change in the temperature of the bath resulting from the addition of a solute sample to the bath involved not only the direct effect due to the solution process but also possibly a secondary effect arising from the change in coupling between the bath and the induction heating coil. Consequently, an extensive analysis of the calorimeter was carried out, and models of the transient thermal processes of the instrument were developed to aid in improving the design and interpreting the behavior of the system. This paper describes the dynamic modeling; the use of it in treating experimental results has been reported earlier.3 The high-temperature solution calorimeter was constructed to measure directly the partial molar heats of solution of solute elements in a variety of liquid metal solvents.1-3 The calorimeter consists of an induction-heated liquid metal bath into which small samples of a solute element can be dropped. The bath temperature is recorded continuously, and the change in the measured bath temperature with time, dTm = f(t), resulting from the solute addition are the raw data from which the enthalpy change caused by the addition is determined. To extract the rmodynamic results from the data, the temperature change must be compared with that resulting from calibration additions of known enthalpy change. Accordingly, it is necessary to understand the transient thermal processes arising as a result of the addition to the bath. Neither modeling nor experimentation alone could provide the required insight into the working of the calorimeter. The alternate use of both methods in conjunction greatly assisted the design of the equipment and experiments, and the interpretation of the data. THE PHYSICAL CHARACTER OF THE SYSTEM The essential parts of the calorimeter, Fig. 1, for model studies are the thermocouple, the liquid metal bath and the surrounding refractories. The system is the solvent metal bath and those refractories around it which undergo a temperature change as a result of an addition to the bath, and which determine the way the temperature of the bath responds to an input. The inputs are the combined transient thermal effects arising when an addition is made to the bath. They include the thermal effects of the addition itself and the results of changed coupling between the bath and the induction coil. The response is the variation in the measured bath temperature, dTm(t) = Tm(t) - Tm(O), from an initial steady state resulting from the inputs. It was assumed in this study that the physical properties of the various elements of the system are independent of the inputs and time, although these properties may vary as the result of changes in the composition and size of the bath during a series of additions. This separation of inputs and the system is equivalent to assuming that the system is linear, i.e., that its behavior can be described by linear differential equations with constant coefficients. Linear behavior can be expected whenever the departure of each portion of the system from its steady-state condition is small enough to cause negligible changes in the thermal properties of the materials and in the various heat-transfer coefficients. Radiative heat transfer is important in this system, so the assumption of linearity should be valid only for small temperature deviations. Several conclusions were drawn from operation of the calorimeter in earlier experimental studies: 1) Radiative heat transport from the top of the bath is a significant portion of the total heat lost from the bath. However, for small changes in the bath temperature the change in transport by this path could be assumed to be proportional to the change in the bath temperature. 2) A very small portion of the heat input is lost through the thermocouple to its water-cooled holder. The thermal resistance and thermal capacity of the thermocouple protection tube are small, so the temperature of the thermocouple should follow closely that of the bath. 3) The remainder of the total heat lost from the bath will pass by conduction through the crucible to, and through, the other refractories, eventually being absorbed by the water-cooled induction coil or by the water-cooled sides and bottom of the enclosure. 4) The thermal resistance between the bath and crucible is very small. Thus the thermal capacity of the crucible will affect the temperature of the bath very soon after an addition of heat to the bath. 5) The thermal resistance between the crucible and the silica sleeve is large, especially if a radiation shield is placed in the gap. The effect of the thermal capacity of the sleeve thus will be significant only at longer times. The thermal resistance through the packing below the crucible also is large, so the packing and the silica sleeve will have similar effects on the behavior of the system. 6) A large temperature drop exists across the gap containing the water-cooled induction coil. Thus for relatively small changes in the thermal input to the bath, the refractories beyond the sleeve

Jan 1, 1970

By Gordon M. Matheson, Charles V. Logie

The current state-of-the-art design of mine pillars can be grouped into empirical and numerical design techniques. Numerical design techniques are based on sophisticated computational techniques which analyze the stresses and strains through the interstices of a pillar. Empirical techniques are less exact, but have been widely used, particularly for coal mine pillar design, because of their ease of computation. Over the years numerous empirical equations have been proposed to calculate the ultimate strength of coal mine pillars. This paper presents a review of the various equations which are most frequently utilized and examines the fundamental assumptions, limitations and applicability of the design formulae. The review intends to provide the practicing mining engineer with an understanding of the assumptions and mathematical basis of each equation to aid in the selection of the criteria most applicable to his specific design problems. Recommendations are made of the empirical equations that are presently most acceptable for design.

Jan 1, 1983

By Roger A. Harris

INTRODUCTION The Kidd Creek Mine produces a total of 3.6 million tons annually. Geologically the orebody is complex, containing rich values of zinc, copper, silver and lead which are mined and milled as two separate "ore types". Production is mainly from highly mechanized sub-level open stopes of approximately 300,000 tons each. The Mine Engineering Department has developed, and now operates, a computer system that is the subject of this report. It was created specifically to aid the daily work of the mining engineer and has features that are new and possibly unique in the industry. DESIGN OBJECTIVES In 1971 a task force, set up to investigate the subject of computer assistance to mine engineering, specified four design requirements which it felt a successful application had to satisfy. They were:- 1) The computer had to offer a TOTAL SYSTEM that was fully integrated into the routine mine engineering function. 2) The computer had to be directly usable by the current engineering staff, the majority of which had received no formal training in computing.

Jan 1, 1977

By W. B. Mather

R. G. Wuerker (University of Illinois, Urbana)—Mr. Mather is to be congratulated for stressing the most urgent need for a program of testing the physical properties of rocks, as they are encountered by the petroleum engineers on their drilling jobs and by the miners on their excavating, roof control and mineral preparation tasks. Another valuable source of information is the Handbook of Physical Constants.22 It stresses the physicist's approach rather than the engineer's procedure. The study of hardness, and rock hardness in particular, is beset with many difficulties. There is no satisfactory definition of hardness yet, and the term hardness is used to describe a number of quite dif- ferent properties. Hardness tests are grouped into static and dynamic determinations. They should be expressed with reference to the mechanical action of the applied force, like indentation hardness, scratch hardness, abrasion hardness, rebound hardness. A discussion of all these various hardness tests and of the special difficulties encountered in hardness testing of such heterogeneous material as rocks is given in the U. S. Bureau of Mines' standard proposal. The more critical student may be referred to the book by D. Landau: Hardness, which is in my opinion the best existing treatise on this subject.

Jan 1, 1952

By G. E. McElroy

Much attention has been directed to mine-air flow in recent years, more especially in Great Britian where there is frequent reference to a theory of fluid flow developed by English engineers. Briefly stated, this theory is that for similar passages of the same relative roughness, in which fluid flow occurs, the conditions of flow are exactly the same for W D V equal values of the product where W = density of the fluid, D = diameter of the passage through which flow occurs, V = mean velocity of flow, and p = absolute viscosity of the fluid flowing. This, the "Reynolds Criterion" of fluid flow, had its origin in the work of Reynolds1 more than 40 years ago. Later, Rayleigh2 amplified the theory which has been conclusively proved for small pipes by the experiments of Stanton and Panne13 over a large flow range, and by Lacey4 over a somewhat more limited range. Concordant results on small pipes have also been obtained by numerous other investigators with single fluids over more or less limited ranges of flow. According to this theory, results in one medium, such as water, are immediately applicable to another, such as air; and experimental results on models are (theoretically, at least) applicable to full-scale designs. This is of great importance in aeronautics and can be of considerable value in mine ventilation research. Hodgson, in a recent paper,6 has outlined the application of this theory to mine-air flow and recent English experiments6 on the resistance of a timbered mine airway have been expressed in this form.

Jan 1, 1927

By Joseph Pogue

THE prices of crude petroleum and its derivatives have shown an upward trend from 1915 to 1920, and a downward trend from 1920 to 1923, see Table 1. Over the former period, oil prices were dominated by the rapidly increasing demands and inflation incident to the war and its aftermath, while over the latter period oil prices were influenced at the outset by deflation and then by the conditions of overproduction that have characterized the past three years. The purpose of this paper is to analyze the broader features of the more recent price movements in the petroleum industry and to relate these features to basic economic conditions in the industry.

Jan 3, 1924

By W. R. Purcell, C. S. Brooks

The internal surfaces of rocks which are in contact with interstitial fluids are known to influence in some degree the recovery of hydrocarbons from pay zones. Despite the admitted importance of the influence of solid surfaces on hydrocarbon recovery, little information is available concerning the extent of surface of reservoir rocks. In this paper a description is given of the apparatus and procedure employed in the determination of the surface areas of sedimentary rocks, and values are reported for a variety of sandstone and limestone cores. In addition, consideration is given to the Kozeny equation, which relates surface area to porosity and permeability. A colliparison is made between the surface areas as calculated from this equation and the geometrical areas of a series of packs of spherical glass beads. Also, for a group of sandstone cores. Kozeny areas are compared with surface areas as determined by the gas adsorption method employed in this investigation. INTRODUCTION It has long been recognized that many processes which are of importance to hydrocarbon production are controlled in some degree by the extent of the surface of the reservoir rock through which the hydrocarbons move. For example, the recovery efficiency that is obtained in a given reservoir is certainly determined in part by the action of interfacial forces between the reservoir fluids and rock, and this action is influenced in turn by the extent of solid surface. Despite the admitted importance of surface effects to problems of petroleum recovery, little information is available concerning the extent of surface of reservoir rocks." It is the purpose of this paper to describe an apparatus which has been employed for the measurement of the surface areas of rock samples and to present the values which have been obtained for a variety of sandstone and limestone cores. In addition, the relationship of surface area to permeability and porosity, as given by the Kozeny equation, will be discussed. METHOD OF MEASURING SURFACE AREA The method of determining surface areas as employed in this work has previously found wide use in studies of porous solids such as catalysts. The method involves the measurement of the amount of physical adsorption of an inert gas, such as nitrogen or argon, on the bare surface of the solid at reduced pressure and constant temperature near the normal liquefaction temperature of the gas. With the aid of the theory of isothermal adsorption as developed by Brunauer, Emmett, and Teller,' it is possible to ascertain the amount of gas (and hence the number of molecules) which is required to cover the solid surface with a single layer of molecules. From a knowledge of the covering area per molecule the total surface ares of the solid can be computed. Since the Brunauer. Emmett, Teller (BET) theory has been adequately discussed elsewhere: it will suffice here merely to present their final equation as ordinarily employed for surface-area calculations. This equation relates the volume of gas, V, which is adsorbed at pressure, P, to the liquefaction pressure, Po, of the gas, and to the volume of gas, V.,, that is required to form a monomolecular layer: In this equation C is a quantity which is related to the heats of adsorption and liquefaction of the gas; for a particular solid-gas system at Constant temperature, C is considered to have a constant value. The basic adsorption data can be presented in the form of Equation (1) by plotting the quantity P/V(Po- P) as a func-

Jan 1, 1952

By G. C. RIDDELL

THE metallurgist, chemist, and physicist are blazing trails that lead far afield. Pushing on into an "Alloy Age" they see a non-ferrous era over- taking iron and steel. Delving into the nature of the physical world, they break down a supposedly indivisible element, hydrogen. Not content with terrestrial problems, they peer back along the cosmic ray into iaterstellar space, glimpsing forces that are, apparently, still busy with the task of atom-making. Mastering and organizing the material and physical, they advance steadily toward that borderland of science where the concept of matter itself seems abandoned, and force is the substance left.

Jan 1, 1930

By Paul C. Merritt

For more than 100 years, British Columbia has been considered a mountainous mining province, rich with potential but relatively poor in actual production. Times have changed. Today, Japanese interests and money have altered the difficult, if not once impossible, economic conditions and market factors which until recently precluded any great growth of the British Columbia mineral industry. The mining boom now underway in British Columbia has carried the total value of mineral production in the Province to a record height in 1962 as it rang up a 27% increase over that of 1961. Breaking the $200 million barrier for the first time, total value of British Columbia's mineral output reached $229- 276,385. Of this amount, metals accounted for 70%; industrial minerals, 6 %; structural materials, 9 %; and fuels, 15%. The substantial increase is attributed to the record production of copper, iron, asbestos, natural gas and petroleum, in addition to the continuing high production rate and favorable prices of other mineral commodities.

Jan 12, 1963

By John D. Ridge, Betty S. Moriwaki

One of the most profound economic forces operating on a global scale is the movement of metals, ores, and concentrates from one country to another. A single shipment can pass through a series of ports and leave a flow map looking like some psychological nightmare. Statistical tracing often proves as difficult. How much did one given country send to another? Does the word ton represent the same thing to all people? What part did free ports and transshipment play? Where did the metal finally stop traveling and enter fabrication? The amount of mineral produced in the form of concentrate and as refined metal can be tracked down in the Minerals Yearbook of the U. S. Bureau of Mines. Quantities imported by the U. S. can also be found in that publication. But the Yearbook will not tell what happened to the metals that did not find its way to the U. S. Even after a study of supplementary literature, such as the USBM Mineral Trade Notes and the publications of the International Tin Study Group and of other private and public organizations, the picture remains vague at best.

Jan 5, 1955

By S. Arthur Krom

ThE James diagonal-plane slimer is specially adapted to handle the finest slimes, but it will also handle sands as coarse as 40-mesh. The saving efficiency of this machine is due to the original construction ,of the deck, and to the rapid reciprocating movement imparted to it by the head-motion. The deck consists of a plurality of connected planes, having a certain fixed ratio of inclination one to another. These planes intersect each other diagonally to the stroke-line of the table and are arranged so as to give the pulp on the table a double treatment. This double concentration performed by the diagonal-plane deck produces cleaner concentrates and tailings than those obtained by the operation of two separate machines. The action of the diagonal planes settles, combines, and holds all the concentrates in one compact mass, sharply defined from the gangue, and easily cut away without loss. Many slime-concentrating machines distribute the feed-pulp for a distance of 4 or 5 ft. only, and upon a very limited settling-surface. This results in a thick, heavy deposit, from which it is impossible to stratify the values and wash away the gangue, the resulting products being dirty concentrates, and tailings carrying high values. The diagonal-plane slimer distributes the feed-pulp for a distance of 10 ft., and upon a settling-surface having an area of 40 sq. ft.; in other words, it spreads the pulp thinly on the table, which allows the metallic values to settle through the gangue quickly, forming a bottom stratum from which the thinly-distributed overlying stratum of gangue is easily brushed away by the feed-water without disturbing the underlying concentrates. Referring to Fig. 1, plane A is the main settling-section of the table. The feed pulp flows gently down this plane and is

Jan 1, 1913

By Jack White

MUFULIRA Copper Mines, Limited, conducted tests on the concentrator in 1942 to determine which type of ball mill, that is, Conical Trunnion overflow or Cylindrical Grate discharge, produced the greater quantity of finished product at the lowest cost. All the data which follows applies to Mufulira ore and to the particular degree of grinding produced with the classifiers installed at Mufulira concentrator. JACK WHITE, Member AIME, is Concentrator Superzntendent, Mufulira Copper Mines, Ltd., Mufulira, Nortltern Rhodesia. Sun Francisco Meeting, February 1949. TP 2729 B. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Feb. 28, 1949. Test Procedure: The test was carried out using ball mills No. 1 to 9 (conical trunnion overflow) as the standard with which to compare No. 10 (cylindrical grate discharge mill). The conical trunnion overflow ball mills are 10 ft diam by 72 in., and the cylindrical grate discharge mill is a No. 99. Each mill runs in closed circuit with a Dorr type DSFX classifier 8 ft wide by 30 ft long. The feed is considered as being identical to all ten units. The figures for the test were derived as follows. Dry Tons Milled: For No. 10 unit (cylindrical grate discharge mill) this figure was taken from the ball mill weightometer, which was corrected for error, and then for moisture content. The weightorneter was checked twice a week during the test, and the error did not exceed 3 pct at any time. The moisture was obtained from a 24 hr moisture sample taken by the ball mill operator hourly, and placed in a closed bucket. The sample was cut where the conveyor drops the feed into the ball mill chute. The Mill Sampling Department made a daily moisture determination on this sample. To obtain the dry tons on units No. 1 to 9 the No. 10 figure was deducted from the month's dry tons milled figure, which, in turn, was taken from the crusher weightometer tons corrected for weightometer error and moisture. All tons reported in this test are short tons of 2000 lb. Ball Mill Hours: This was taken daily from the Shift Boss reports giving actual running hours for each unit. Screen Analyses: Coarse Heads (Ball Mill Feed): The monthly composite coarse heads screen analysis, done by the Mill Sampling Department, was used for the minus 200 mesh in the feed to the mills. F. X. Classifier Overflow: The ball mill operators took an hourly 24 hr sample of the overflows of units No. 1 to 9. This was a hand sample, but cut with a special cutter, and is believed to be very reliable. On No. 10 unit, an hourly 24 hr sample, and an hourly shift sample were cut in the same way. These five samples were split, filtered, and dried by the Research Department and were then wet screened on a 200 mesh screen. The average of the three shifts samples on No. 10 unit had to check the 24 hr sample within 1.5 pct to be acceptable. A weighted composite was cut each day from both 24 hr samples, and at the end of each month it was screened as follows: Wet screened through 325 mesh, the plus 325 then screened on a rotap for 15 min through 65, 100, 150, 200, and 325. This was done in duplicate. All splitting, drying, and screening of samples was done by one of the Mill Research staff, to insure accuracy. F. X. Classifier Overflow Densities: These were taken from the Shift Boss reports. Densities were taken by the ball mill operator every hour. Circulating Loads: These were taken a number of times during the test both by direct method (weighing a measured portion of classifier rake sand, and deducting moisture) and by calculation using the formula:

Jan 1, 1951

By Jack White

MUFULIRA Copper Mines, Limited, conducted tests on the concentrator in 1942 to determine which type of ball mill, that is, Conical Trunnion overflow or Cylindrical Grate discharge, produced the greater quantity of finished product at the lowest cost. All the data which follows applies to Mufulira ore and to the particular degree of grinding produced with the classifiers installed at Mufulira concentrator. JACK WHITE, Member AIME, is Concentrator Superzntendent, Mufulira Copper Mines, Ltd., Mufulira, Nortltern Rhodesia. Sun Francisco Meeting, February 1949. TP 2729 B. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Feb. 28, 1949. Test Procedure: The test was carried out using ball mills No. 1 to 9 (conical trunnion overflow) as the standard with which to compare No. 10 (cylindrical grate discharge mill). The conical trunnion overflow ball mills are 10 ft diam by 72 in., and the cylindrical grate discharge mill is a No. 99. Each mill runs in closed circuit with a Dorr type DSFX classifier 8 ft wide by 30 ft long. The feed is considered as being identical to all ten units. The figures for the test were derived as follows. Dry Tons Milled: For No. 10 unit (cylindrical grate discharge mill) this figure was taken from the ball mill weightometer, which was corrected for error, and then for moisture content. The weightorneter was checked twice a week during the test, and the error did not exceed 3 pct at any time. The moisture was obtained from a 24 hr moisture sample taken by the ball mill operator hourly, and placed in a closed bucket. The sample was cut where the conveyor drops the feed into the ball mill chute. The Mill Sampling Department made a daily moisture determination on this sample. To obtain the dry tons on units No. 1 to 9 the No. 10 figure was deducted from the month's dry tons milled figure, which, in turn, was taken from the crusher weightometer tons corrected for weightometer error and moisture. All tons reported in this test are short tons of 2000 lb. Ball Mill Hours: This was taken daily from the Shift Boss reports giving actual running hours for each unit. Screen Analyses: Coarse Heads (Ball Mill Feed): The monthly composite coarse heads screen analysis, done by the Mill Sampling Department, was used for the minus 200 mesh in the feed to the mills. F. X. Classifier Overflow: The ball mill operators took an hourly 24 hr sample of the overflows of units No. 1 to 9. This was a hand sample, but cut with a special cutter, and is believed to be very reliable. On No. 10 unit, an hourly 24 hr sample, and an hourly shift sample were cut in the same way. These five samples were split, filtered, and dried by the Research Department and were then wet screened on a 200 mesh screen. The average of the three shifts samples on No. 10 unit had to check the 24 hr sample within 1.5 pct to be acceptable. A weighted composite was cut each day from both 24 hr samples, and at the end of each month it was screened as follows: Wet screened through 325 mesh, the plus 325 then screened on a rotap for 15 min through 65, 100, 150, 200, and 325. This was done in duplicate. All splitting, drying, and screening of samples was done by one of the Mill Research staff, to insure accuracy. F. X. Classifier Overflow Densities: These were taken from the Shift Boss reports. Densities were taken by the ball mill operator every hour. Circulating Loads: These were taken a number of times during the test both by direct method (weighing a measured portion of classifier rake sand, and deducting moisture) and by calculation using the formula:

Jan 1, 1951

DURING the early part of August, 1880, I was directed by Prof: J. P. Lesley, State Geologist, to assume charge of the geology and mapping of the Second Geological Survey of the anthracite coal-fields. I visited the region unineumbered by any instructions other than this, that I should submit a plan for making the sur- * In the practical application of this method I wish to acknowledge the valu¬able aid rendered by my assistant, Mr. A. W. Sheafer.

Jan 1, 1881

By E. A. Beck

For a number of years many attempts have been made to use thermit in order to do away with piping in ingots. Some of these attempts were successful, while others did not give the expected results. Nearly every plant had its own method of using the thermit, and no special care was taken to study the results or to find the causes for lack of success. Formerly the principle of the process was to decrease the piping by introducing a can filled with thermit, attached to an iron rod, into the head of the ingot directly after it had been poured. In this case the thermit reaction took place in the upper part of the ingot, and it was thought that through the heat produced the head would keep liquid longer and piping thus be reduced. In other words, the aim was to keep the head of the ingot open by making use of the heat of the thermit reaction, which would thereby give the gases in the steel sufficient time to escape. This result can be attained by the application of a large enough quantity of thermit, but it would not be economical in general practice, and could only he used for high-grade material. Many steel-makers abroad and in this country have had this experience. The Th. Goldschmidt A. G., Germany, has, therefore, made a special study of this question with the cooperation of a well-known steel company, and has worked out a new method for the application of thermit for this purpose. The results obtained have been most satisfactory and reliable, and this process is now used in Germany on a large scale in many prominent steel-works. The thermit is applied in cans, as in former years, but the principle of the process is entirely different. The object of using the thermit is not to heat the steel and keep it liquid,

Jan 1, 1914

By R. H. Doremus

From measurements of carbide precipitation rates in a iron it was concluded that the carbides nucleated on dislocations in both strained and unstrained samples, except for the latter at lower temperatures and higher carbon concentrations, where there were more muclei than could form on the dislocations. The equation of Cottrell and Bilby for the segregation of atoms to dislocations was found to be inapplicable to this system. No satisfactory theory for the growth process is available. A study of the rate at which a second phase separates from solid solution can frequently reveal much about the mechanism of separation. There are still many features of the precipitation of carbon from a iron that are not understood, although this system has been examined extensively. To provide more insight into the mechanism of carbide precipitation in a iron, rates of this process were measured at different temperatures, carbon concentrations, and densities of dislocations in the iron. The concentra- tion of carbon in solution was followed from the height of the internal-friction peak; this height is directly proportional to the amount of carbon in solution and is not affected by the growing carbide particles. In this paper these rates are compared with those found by earlier investigators, and the mechanism of precipitation is discussed in light of these results as well as two earlier studies1, 2 and the electron microscopic work reported in the preceding paper. EXPERIMENTAL The amount of carbon in solution was followed by

Jan 1, 1961