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By A. W. D. Hills

This paper describes the development of a generalized integral-Wofile method for the analysis of heat transfer dwing solidification. The method is extremely flexible, and can be applied to a wide range of situations. This flexibility has been achieved by characterizing the solid metal layer in terms of two parameters, and by developing two simultaneous nonlinear differential equations for these parameters in terms of the heat fluxes crossing the boundaries of the solid layer. The use of these equations is illustrated in a series of examples which involve the solidification of pure metals at zero superheat cooling under different conditions. The simplicity with which the method can be extended to treat more complicated jwoblems is illustrated in a further example which involves natwal convection effects in the liquid metal. ThE rate at which molten metal solidifies in an industrial casting process, and the structure of the cast product, are both controlled by the rate at which heat can be removed from the casting. A knowledge of heat transfer rates is thus essential to the control of the process and to the control of the structure and soundness of the final casting. Heat transfer rates during real solidification processes cannot be predicted by formal mathematical techniques, however, because nonlinear boundary conditions are involved. Approximate methods are normally used, and these have included electrical and hydraulic analogue techniques, finite difference methods, and the integral-profile method. Considerable effort has been devoted to the development of the first two techniques, but the integral-profile method has been used very little so far. This is unfortunate because the method is capable of providing relatively accurate solutions for the heat transfer equation during solidification without involving large amounts of computer time. A further advantage of the method is its flexibility, although this is not apparent from the integral-profile solutions that have been developed to date. These solutions have been derived for the solidification of molten metal at zero super-heat under cooling conditions involving either a constant heat flux from the cooled surface;' a constant heat transfer coefficient at the surface,'-3 or a specified variation in the surface temperature.4,5 A generalized integral-profile method is presented in this paper which can be used to predict unidirectional solidification rates under a very wide range of more realistic cooling conditions. The use of the method is illustrated in a series of problems involving pure metals, or skin forming alloys, solidifying at zero super-heat. However, the principal advantage that this method has over the previous integral-profile methods is the ease with which it can be extended to treat more complicated solidification problems. This is illustrated by considering a problem in which super-heat is liberated from the liquid metal by natural convection during the solidification process. In the final section of the paper the generalized method is compared with previous methods used to predict solidification rates and its extension to more complicated solidification problems is briefly discussed.

Jan 1, 1970

By John W. Langley

The unsatisfactory character of most, if not all, of the processes for the direct determination of alumina in the presence of iron and phosphoric acid, and the sharpness with which both the iron and phosqhoric acid can be determined, have led chemists to rely mainly

Jan 1, 1892

By J. Ostachowicz, B. Holynska, M. Lankosz

The paper presents an analyzer and the method for the continuous determination of weight percentage of ore grains with diameter smaller than 75 µm in mineral slurries. The method is based upon the measurement of characteristic x-rays of copper excited by primary radiation of two different energies 16.5 keV and 60 keV from Pu238 and Am241 sources respectively. Additionally the backscattered primary radiation is measured in order to correct the variations of the solids content in the slurry. Since the particle size distribution of slurry can be described by the Rosin-Rammler formula, some calculations have been carried out in order to evaluate the influence of distribution parameters upon the results of the measurements of weight percentage U75 of particles smaller than 75 µm. The influence of solids content and of the copper concentration variation on the results has been also evaluated.1 It resulted from the calculations that the ratio rl/rz, where rl and r2 are the relative intensities of copper characteristic x-rays excited with 16.5 keV and 60 keV photons respectively does not depend on the copper content within the range 1 % to 4% of copper and is slightly dependent on the solids weight fraction and its chemical composition. The change of the dispersion parameter of the Rosin- Rammler distribution from 0.5 to 0.9 results in a change of value of U75 of approximately 3.0%. The results of calculations have been confirmed by the results of laboratory experiments. Therefore, a prototype of industrial analyzer for continuous determination of weight percentage of particles smaller than 75 µm has been designed and made. Its schematic drawing is shown in [Fig. 1]. Slurry is flowing down through steel flow-cell of the length equal to approx. 2 m. In the center, two XRF measuring heads (1) and (2) are located. Each of the heads comprises a rigid waterproof cover (3) with the mylar window (4), in which a proportional counter of resolution 15% for 6.4 keV is mounted with a preamplifier (5). The low- energy isotope source (6) is centrally located above the detector

Jan 1, 1980

By R. T. DeHoff, L. J. Buteau, J. Kronsbein

Network topology is introduced and used to describe sinter bodies at various stages of the sintering process. The matrices of incidence, loop-branch. tree-branch, and cut-branch are constructed and their relationship to the three-dimensional void space and the common two-dimensional bounding surface is established. The sintering body is assunzed to remain connected but this is not so with the void space. The topological invariants known as Betti numbers are related to this observed fact and provide parameters which measure the progress of the sintering process. They are extracted from the matrices by means of known algebraic operations. Experimental procedures are given which permit actual construction of the various matrices and determination of the Betti numbers by serial sectioning of the sinter bodies. A sinter body is produced by exposing a large number of metallic particles (0.00001 to 0.3 in. diam) to a temperature that is near but below their melting point. When these particles are maintained at such a temperature for a sufficient length of time, it is found that the interparticle contacts become welded. As time increases, these welds, often referred to as necks, grow. All of the space between the particles constitutes a single connected void; an ultimate consequence of sintering is the breaking up of the void into separated parts. A mathematical apparatus for describing the geometric characteristics of a sinter body at each stage of the process was first proposed by F. N. Rhinesl when he introduced the application of topology to this problem. He described the sinter body in terms of one of its topological invariants, the genus. The most important advantage of a topological description is invariance with respect to continuous deformations. This means that particle sizes and shapes need not be considered, resulting in considerable simplification and generalization of the geometric description. In the case of a sinter body, wherein the internal geometry is particularly complex, the simplification provided by topological concepts is absolutely essential. The important parameters in the Rhines model are the number of particles and the interparticle contacts. The invariant considered called genus is given by Euler's formula for the connectivity of two-dimensional surface of the sinter body. This surface includes the pore-solid interface. The Euler formula is G = C - P + 1 [1] where C = number of interparticle contacts, P = number of particles, and G = genus of the surface bounding the sinter body. In topology the term genus may be used to mean the number of self re-entrant cuts that can be made on a closed surface without dissecting it into more than one connected surface. Its use is restricted to the surface and does not apply to the three-dimensional volume enclosed or excluded by it. In the case of sintering, the volume enclosed by the surface is defined as the sinter body; the volume excluded will be referred to as the void space. There is an intrinsic reason for using genus as a characteristic number associated with a sinter body. The genus is related to the Gaussian curvature by the integral of the product of the principal curvatures taken over the entire surface of the sinter body, as given by

Jan 1, 1965

By L. W. Pommier, F. B. Brien, A. K. Bhasin

The diflerential movement of solid particles through solid-liquid suspensions is very important to many branches of engineering. The flow of suspensions around immersed bodies is mainly of a turbulent nature. Problems are encountered when attempts are made, as is the general practice, to extrapolate the velocity and resistance relationships of Newton, pertaining to Newtonian systems, into non-Newtonian solid-liquid suspensions. The conventional velocity and resistance relationships for turbulent flow in fluids when applied to suspensions, do not take into consideration the two very important variables: suspension particle size and solid volume fraction. A study of the effect of suspension particle size (dgb) on the velocity of falling balls leads to the concept of a critical particle size (dgc) at which the suspensions will be Newtonian. This leads to the classification of static suspensions into two types: suspensions consisting of particle of diameter dgh > dgt, and those with dgh, < dgr. Separate velocity and resistance equations for these two types of suspensions have been proposed, taking into account both the solid particle size and solid volume fraction. The agreement between the velocities predicted from the proposed equations and the measured velocities, confirms their validity. The resistance force offered by suspensions to the movement of immersed bodies has been calculated from the proposed equations, and the effects of suspension particle size and solid volume fraction on the resistance force and velocity have been examined. The movement of immersed bodies in solid-liquid suspensions is of great importance in many areas of engineering such as minerals processing, oil well drilling, suspension flow in pipelines, and hydrometallurgy. A number of mineral dressing processes deal essentially with the movement of solids in suspensions—in particular, classification, thickening, filtration, ore washing, and gravity concentration—thus a study of the fluid characteristics of suspensions is of theoretical and practical interest.&apos; A rigorous analysis of the mechanisms of momentum transport of a solid-liquid system is complex indeed. The rheological properties of the suspensions deviate from those of liquids, varying, for example, with density, solid volume fraction, size and shape of the solid phase of the suspension, and with the density and viscosity of the liquid phase. The flow of suspensions around immersed bodies is mainly of a turbulent nature and hence studies of the turbulent flow characteristics of suspensions are of par- ticular importance. Problems are encountered when attempts are made to extrapolate the velocity and resistance relationships of Newton, pertaining to Newtonian systems, into non-Newtonian solid-liquid suspensions. Due to the numerous variables present in a suspension, certain limitations and assumptions become necessary in order to produce quantitative relationships for predicting their effects. The solid particle size and the solid volume fraction are two of the more important variables. By comparing the measured and calculated Newtonian velocities of falling balls in simple static suspensions, the existing velocity and resistance relationships have been modified to take these variables into account. In order to keep the study less complex, all other variables such as the characteristics of suspending liquid and shape of the particle are maintained constant. Objective The objective of the present investigation is to modify the Newtonian velocity and resistance equations in order to take into account the suspension particle size and solid volume fraction. Theory Liquids are classified on the basis of viscosity, which may be defined as the relationship between applied shear stress and resulting rate of shear.&apos; pure single-phase fluids composed of small light molecules behave as Newtonian liquids, having a single viscosity pa-

Jan 1, 1971

By Richard Klimpel

This paper describes the effects of slurry viscosity on the selection-for-breakage and breakage distribution parameters in the wet grinding of ores. A series of experimental tests were run on laboratory scale ball mills. Slurry viscosities were modified by varying the solids/water ratio with and without the presence of selected chemicals. Very consistent and predictable correlations are shown to exist. The grinding parameters were calculated using a computerized back-calculation technique developed by Klimpel and Austin. Industrial scale circuit calculations and preliminary plant trial data suggest that considerable increases in throughput and/or fineness of grind can be achieved through the judicious use of chemical additives.

Jan 1, 1977

By R. J. Sherman, M. R. Achter

Creep rates have been measured for nickel at 1200°F in air and in vacuum, and related to the depth of surface cracks in the specimens tested in the two environments. The surface cracks were observed to grow faster in air than in vacuum in both short-time and long-time tests. Crack depths, however, could be correlated with creep rates only in the short-time tests. Although no cracks were observed in a relatively brittle Ni-Cr-A1 alloy creep tested at 1300°F, the appearance of alloy specimens fractured after interruption in creep indicated that there was a decrease of intergranular cohesion resulting from the diffusion of atmospheric gases into grain boundaries. PREVIOUS investigations1-3 have demonstrated that the effect of atmosphere on the high-temperature strength of nickel and nickel-base alloys may be reversed by changes in the stress or temperature of the test. At high stress and low temperature the creep-rupture life is longer in vacuum than in air, while at high temperature and low stress the relative strengths are reversed. A mechanism to explain this behavior was proposed based on two competing processes. Oxidation hardens and strengthens a metal, but adsorption of gas, by lowering surface energy, reduces the work required to propagate an intergranular crack. The controlling process is determined by temperature and stress. Basic to this mechanism is the concept that environment determines the ease of propagation of intergranular cracks and thus affects creep rate and rupture life. To explore the mechanism in greater detail, this investigation was undertaken to determine the effect of atmosphere on crack initiation and propagation rates in nickel1 and a relatively brittle Ni-Cr-A1 alloy.3 EXPERIMENTAL PROCEDURE The materials were the same as used previously. Nickel of 99.8 pct purity had the following impurity content: 0.02 pct Co, 0.03 pct Fe, 0.02 pct Mg, 0.03 pct Si, and 0.008 pct C. Rods were cold swaged from 1/2 in. to 3/8 in. in diam and machined into speci- mens with gage sections 1/4 in. in diam by 1-1/4 in. long. They were annealed in vacuum at 1600" F for 1 hr to achieve a grain size of 0.07 mm. The alloy was composed of 19.1 pct Cr, 3.6 pct Al, 1.7 pct Si, 0.57 pct Fe, 0.10 pct Mg, 0.027 pct C, 0.004 pct S, and the balance Ni. Sheet specimens of 0.500-in. width and 1.25-in. gage length were machined from 0.033-in.-thick strip and annealed in vacuum at 2000° F for 2 hr, resulting in a grain size of 0.036 mm. Large amounts of an intergranular phase were introduced as a result of the anneal. Creep tests on both materials, using equipment previously described by Shahinian; were conducted in air and in a vacuum of 1 x 10-5 mm Hg. They were continued to rupture and interrupted at various stages of the test. Although extensions were measured from dial gage readings of movement of the lever arm, it is considered that valid comparisons of creep rate may be made in this manner.l Two parameters were measured metallograph-ically* on longitudinal sections of nickel specimens interrupted during creep—the mean depth of surface cracks 2, and the density n as the number of cracks per unit length of surface. They were combined into one parameter by the relation p = n-d [1] As used here, p is equal to the total of crack depths per unit length of surface. RESULTS Nickel. It is well known that the incidence of intergranular cracking is increased with increasing rupture life. Indeed, it is evident in Tables I and I1

Jan 1, 1962

R. B. BRinsmade, Ixmiquilpan, Hgo., Mexico (written discussion").—how far ahead of the United States are the self-governing British colonies in their application of economic democracy is well illustrated by Mr. Godson&apos;s paper. To prove this, I need quote only two of his assertions, the italics being mine: "lt is a stern fundamental principle that a11 natural resources are the inalienable property of the crown.&apos;&apos; "The right to a claim should only exist as long as it is worked or taxed to insure work. Once depart from that sound maxim, there results improper control of the natural resources of the country, which primarily belong to the people." These assertions formed the basis of my criticism1 of Dr. Raymond&apos;s paper in 1913, and they should be inscribed in letters of gold above the entrance to the office of every county recorder in the United States. I venture to assert that the existing United States mineral land laws are essentially unfair to the nation and a hindrance to the legitimate miner, because they fail to embody the above quoted principlca; and this applies both to state laws east of the Mississippi and to federal laws in the West. That these laws favor the forestaller and the monopolist, defraud the government of its fair share of the profits of mineral production, and tend to industrial feudalism must be evident to any competent unbiassed observer. The fact that no serious political movement arose to change them, until the conservation agitation of the last decade, may be largely explained by two salient conditions. First, as stated by President Winchell, "for a long time there was such a vast surplus, or excessive amount of unwanted, undesirable land in the West that the land offices did not scrutinize the claim sought to be located;" second, that the millions of individual farm owners throughout the country could easily be aroused, by the special pleaders hired by the great land speculators and monopolists, to use their vast political power for the suppression of any statesmen striving to incorporate in our semi-feudal land laws any such principles as those quoted from Mr. Godson. While agreeing with Mr. Godson that a freehold or fee-simple title, if coupled with obligatory continuous work, may have the same practical effect as a lease, it seems to be the experience of the most active and

Jan 1, 1920

By M. Hoch

Equations are derived from statistical considerations to represent the activities of each component of an interstitial solution, and of a compound with a wide homogeneity range as a function of composition and temperature, based on the interaction energies between the various components, Eij. The equations are checked on the binary systems Fe-C, Ta-H, and Y-H, the ternary systems Ti-O-H, liquid Fe-C-0, and the compounds TiO, MnO, COO, and YH,. In all cases the present model represents the experimental data well. THE aim of this paper is to derive from statistical considerations the thermodynamic behavior of non-substitutional solid solutions. "Nonsubstitutional solid solution" means either an interstitial solid solution (carbon in iron, oxygen and hydrogen in hexagonal and bcc titanium, and so forth) or deviation from stoichiornetry in compounds (introduction of vacancies—removal of atoms in one or both lattice sites of compounds FeO, MnO, TiO, NbO, YH2). wagnerl and Fowler and Guggenheim considered the theory of compounds with small deviation from stoichiometry; Anderson includes larger deviations from stoichiometry, the defect being present in one component only, as vacancy and interstitial. Rees considers only vacancies in one of the components and introduces various kinds of sites for the component where the defect occurs; the various sites interact with different energies, thus giving isotherms with two or more plateaus. Both Rees and Anderson are mainly occupied in determining the limits of two-phase regions, and the defect interaction energy is determined from the critical point. Darken and Gurry5 gave a brief treatment of carbon solution in iron; Speiser and spretnak calculated the configurational entropy for binary interstitial solid solutions by assuming that each interstitial atom in the solution excludes a certain number of neighboring interstitial sites from occupancy. Use will be made of this concept later. Hoch et al treated transition metal oxides of the NaCl-type structure, and also oxygen solution in titanium.&apos; The main aim was to determine the behavior of the activity of one of the components as a function of the composition in the single-phase region. In the present paper, the various interaction energies are discussed in detail and the similarity between interstitial solid solutions and deviation from stoichiometry in ionic compounds is shown. Both types of systems have in common that at least on one kind of lattice site only one kind of atom occurs; this gives a fixed frame to the system, permitting a much easier statistical treatment than for the substitu-tional solid solutions. (The theory is also applied to ternary systems.) The difference between an interstitial solution and deviation from stoichiometry can be explained as follows. In an interstitial solution in the pure or standard state the host atom or host structure is present alone and all the interstitial sites which are going to be filled when the interstitial atom is introduced are empty. The interstitial solution is now created by introducing atoms into this empty lattice. In the deviation from stoichiometry, both kinds of lattice sites are already occupied in a special fashion (all lattice sites occupied, or the same fraction of lattice sites empty, or one kind completely filled, the other only two-thirds). Deviation from stoichiometry removes atoms from lattice sites, adds them, or removes atoms from one kind of lattice site and introduces them on the other lattice site. Though both cases (interstitial solution and deviation from stoichiometry) lead almost to the same equations, they are treated separately. The treatment given below corresponds to the "regular solution"10 treatment of substitutional solid solutions. Speiser and spretnak&apos;s6 treatment is similar to the athermal solution in the substitutional use. a) INTERSTITIAL SOLID SOLUTIONS Theory. It will be assumed that there are N lat-tice sites occupied by the host atom (denoted by 1). Corresponding to those N lattice sites there are N octahedral and EN tetrahedral interstitial sites. If only one kind of interstitial atom is added, this in-

Jan 1, 1964

By James P. Roe

Those who deem the subject of this paper an old and superseded one may recall with advantage the words of the great proverb-maker, bidding us to seek the new in the ashes of the old. The manufacture of wrought-iron began with the small hearth built upon an eminence, and relying on the wind for blast. Next came, either the hearth about 12 in. in diameter by 2 ft. in height, blown by a man operating two goat-skins for bellows, or, a hearth of greatly varying diameter and about 10 R. high, depending for its blast upon natural draft. The former appeared in India, the latter in Burmah; and both were in operation until quite recently, though their origin is lost in prehistoric times. The Catalan forge was the evolutionary descendant of the foregoing, and the parent of the Blase-ofen, which in turn led to the high bloomary or " StÜckofen," the father of the blastfurnace, as a producer of cast-iron. The production of cast-iron checked the growth of the direct processes; and led to the introduction of various hearths, such as the Walloon, for low-silicon irons; and the South Wales process, combining the run-out fire with the finery, for higher-silicon irons. Some of these are still in operation in localities possessing the necessary raw materials; and their product is used for purposes requiring wrought-iron of exceptional quality, the supply of which is still smaller than the demand.

Jan 1, 1906

By Carl Swartz

ALTHOUGH a number of articles appeared during the war advocating the use of cadmium in lead-tin solders, very little information of value can be found in the literature regarding the properties of solders containing cadmium. In most of the published articles the cadmium seems to have been considered merely as a partial substitute for tin in a tin-lead alloy rather than as an essential constituent of a ternary alloy. The primary object of the substitution of cadmium for tin was to lessen the amount of tin required, at a time when the latter was scarce and high-priced, and thus to produce a cheaper solder. While this object was accomplished, the new properties resulting from a change from a binary lead-tin alloy to a ternary lead-tin-cadmium alloy were not given proper consideration in many cases. For the past few years, the American Smelting & Refining Co. has been marketing a very considerable amount of cadmium in the form of lead-tin-cadmium alloys for use as solders for certain special purposes, and the successful use of these solders suggested that if more extensive knowledge were available concerning the properties of lead-tin-cadmium alloys of various compositions their field of usefulness might be materially extended. The investigation described in the present paper was undertaken to obtain this information and, by means of tests under conditions approaching those of practical use, to determine the suitability of cadmium solders for various purposes.

Jan 1, 1928

By M. N. Qureshy, D. D. Sarma, B. K. Verma

Kolar Gold Fields are one of the best known gold deposits in South India where gold occurs in quartz reefs in Archaean hornblende schists and shows large variation in grade. The history of mining goes back to 18th century. The workings at Nundydroog Mines, chosen for Operations Research studies, have entered a depth of 2150 meters. The gold values in these mines were thought to be erratically distributed. However, by using 10540 samples from 49 blocks of ore, it is established that the gold value properties in inch- pennyweight units follow a two parameter log-normal distribution. Emperical relationships between arithmetic means and estimates based on peripheral and internal block values have been worked out using the estimator suggested by Krige (1951) instead of &apos;t&apos; estimator suggested by Sichel (1952). These relations can be used in arriving at block estimates with respective standard errors. There is no significant emperical relationship between depth and the grade of ore.

Jan 1, 1969

Research and Development, once considered a luxury item only for well-heeled companies, has in the last two decades come into its own as a vital contributor to the fortunes of electronic, automotive, chemical and aerospace firms. In terms of money and talent poured into research, the mining industry is still far behind those industries. Although the U.S. Bureau of Mines, plus various mining and manufacturing firms and universities have made notable contributions to mining technology, the historical pattern of mining R&D shows a heavy reliance on the results of research in other industries. It is difficult to tell whether this pattern will change significantly in the future, but there is evidence of a growing awareness by mining officials that greater R&D efforts are going to be required not only to meet the nebulous demands of tomorrow&apos;s world but to meet the ever-present, mounting pressures being generated by "intra-metals" and "inter-materials" competition.

Jan 1, 1968

THE good and lofty men of intelligence are constantly discoverers of many beautiful things, because of their kindness or because they are driven by necessity. Either they shorten the method of making them after they have seen them, or they think how they can be increased in power or how they can be used for various effects in addition to the one intended by the inventor. Certainly all the effects described to you in this Tenth Book derive from gunpowder. When so many proper- ties and so much strength were observed in this, it was thought that by enclosing it in some strong thing that had the power to resist it, gunpowder would produce a marvelous effect. And thus they made a tube of bronze or iron [160v] which they closed with a wooden plug. They applied fire, and when they saw how forcefully this plug issued they thought of making one that would come out and strike in order to destroy things. They made an instrument of bronze or of iron and put some powder and a round stone inside, and called it a spingard. Developing then from this,

Jan 1, 1942

[Alphabetic Section: The letter immediately following a member&apos;s name indicates grade: M-member, A-associate, J-junior. The numerals following member&apos;s grade indicate year of election. The letter following year of election indicates primary divisional affiliation: A. Mining & Exploration F. Coal B. Minerals Beneficiation G. Petroleum C. Iron and Steel H. Industrial Minerals D. Extractive Metallurgy J. Council of Education E. Institute of Metals K. Council of Economics Geographic Section: An asterisk (*) preceding a member&apos;s name indicates availability for consulting work:]

Jan 1, 1961

By T. Egleston

The treatment of the residues from the manufacture of sulphuric acid which contain small amounts of copper, silver and gold, has attracted considerable attention in Europe. They are successfully treated in several works on the continent, and in as many as twenty establishments in different parts of England. As the process must sooner or later attract attention in this country, I have put together my notes made in three of the most important establishments in Europe. These are the works at Hemixem near Antwerp, of Duisbourg in Westphalia, and of Oker in the Hartz. In the last works only, the ores are produced in the vicinity of the place where they are treated. The works at Duisbourg treat ores which come from the Rio Tinto mines in Spain, which often contain considerable quantities of arsenic. They are roasted in a number of different works along the Rhine for the manufacture of sulphuric acid. They are brought by boat and are landed at the works by steam-cranes. They are carried at once by a double-inclined plane worked by steam to the storagehouses to be kept, until treated. The wagons, after being weighed, are dumped. The ore is assayed at once, the assay-sample being taken from the boat while the ores are being discharged. They are all fine, and contain two to eight per cent. of copper and about sixty per cent. of iron, and a small amount of silver and gold. Their average composition is given below:

Jan 1, 1886

By Eugene McAuliffe

The management of The Union Pacific Coal Co., which operates a group of coal mines in Southern Wyoming, believes in the value of applied psychology as a productive factor in the work of getting out coal. Operating almost wholly through the medium of mechanical loading machinery, the company has for some years paid a bonus, equivalent to one-half the labor saving made above a determined average output per shift worked, on a given machine. No penalty is attached where the established output is not obtained, but in 1933 the men on one class of machines earned an average premium of $0.633 per shift on 56.4 per cent of the tonnage loaded. On another class of machine, the men earned an average premium of $0.686 per shift on 28.4 per cent of the tonnage loaded An increase of 36 per cent in tons loaded per man-shift has resulted since the program was instituted. This coal company has also been very successful in reducing mine accidents through prizes awarded in an unusual way. At the close of the year, every man whose particular mine section passes through the year without a lost-time accident is given a ticket entitling him to participate in a safety drawing where an automobile is awarded as first prim.. There are also a number of cash safety prizes which are similarly awarded. Some 1500 persons attend the drawing, which excites much interest and attention. The particular plan employed, the payment of production bonus awards and safety prizes, is foundationed upon collective. rather than individual effort, and, once gotten under way, has proved to be substantlally self-cnforcing.

Jan 1, 1934

United Engineering Society ARTHUR S DWIGHT J VIPOND DAVIES J V N Dorm Engineering Societies Library Board SIDNEY H BALL ALEXANDER C HUMPHRFYS GEORGE C STONE JOHN H JANEWAY Engineering Foundation Board H M BOYLSTON J VIPOND DAVIES GALEN H CLEVENGER Society for Promotion of Engineering Education WILLIAM KELLY ALLEN H ROGERS

Jan 1, 1923

By R. L. Wiegel

Consideration has been given to the merging of a size reduction model and a mineral liberation model to permit prediction of mineral composition as a function of size. The results of this integration of size reduction and mineral liberation models are discussed from both theoretical and practical viewpoints using batch grinding data for a magnetic iron formation sample as a demonstration vehicle.

Jan 1, 1977

By Willard Ide Pierce

THE native methods of mining and milling gold-ores in Korea may not present any specially new features, but are chiefly interesting as primitive practices, still followed at the present day. In mining where the rock is hard, wood is piled up near the face of the tunnel or drift and then set on fire. The fire bums for twenty-four hours, after which, three or four days are given for the rocks to cool, before the miners go in and extract the loosened material. The only tools in use are a hammer, a steel gad about five inches long, and a flat spoon-shaped basket. The pay-streak or chute is closely followed, and in places the workings are very small and intricate. Rock not yielding more than $6 per ton is not extracted. The manner of opening a mine is to begin on the outcrop, where the rock pays, sink a shaft or run a tunnel on the vein, and follow the pay-streak and more easily worked ore. When this is exhausted, or the influx of water interferes, the opening is abandoned and operations are begun again at a new spot on the outcrop. The place usually selected is as high up on the mountain as possible, and in no instance is advantage taken of the topography by running a cross-tunnel to tap the vein. The ore is brought in baskets to the surface, and there placed in sacks, holding about 150 1bs. each, and taken to be crushed. The rock is first crushed between two stones, as shown in Fig. 1. The upper stone is oval and rounded on the bottom, so that it can be readily rocked on the under stone. Two pieces of wood, used for handles, are placed, one on each side, in grooves in the upper stone, and held in position by means of straw rope. The lower stone is not smooth on top, but exhibits three elevations running lengthwise, with shallow depressions between them. The middle elevation acts as a fulcrum on which the upper stone may be rocked. From two to ten men, according to the weight and size of the stone used, are employed in rocking. With four men, from 300 to 350 lbs. of rock can be crushed per day, the stone making 50 complete oscillations per minute. The men squat on each side of the stone and move it to and fro by means of the wooden handles. The ore is fed, in pieces up to the size of an egg or even larger, by one of the men. During the crushing one man on each side, as the stone rocks from

Jan 1, 1890