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By Frank C. Greene

The results of drilling in Missouri in 1938 are overshadowed by the leasing activity in northern Missouri, which began about the middle of the year. Nothing like it has ever been witnessed by the oil industry. With no production except a minor amount of gas, and with no drilling except in Clay, Platte and Marion Counties, a leasing campaign has embraced most of the counties north of the Missouri River and spread into southern Iowa, southeastern Nebraska and northeastern Kansas. It is reported that nearly all farms that could be leased without payment of a bonus have been leased, mostly on 10-yr. contracts, and at the end of the year a policy of bonus paying is in effect. Many of the major oil companies are leasing in the area and at least 15 of them are represented by scouts. Similarity to the Illinois Basin, low-priced leases and low drilling costs are among the reasons advanced for the leasing activity. Drilling activity in Missouri increased nearly two-thirds over 1937, with a total of 164 completions. The main activity was the extension of the "shoestring" of the so-called Bartlesville gas pool in Jackson County. It now seems that this sand is probably at the horizon of the Burbank sand. A new Squirrel sand oil pool was discovered in Jackson County. Cass County had five oil wells, with 63 bbl. initial production, four gas wells with 542,000 cu. ft. initial open flow, and 15 dry holes. Jackson County had three oil wells, with 24 bbl. initial production, 56 gas wells with 52,021,168 cu. ft. initial open flow and 57 dry holes. In Vernon County seven oil wells, with about 36 bbl. initial production, and two dry holes were completed. The oil production dropped off very quickly. In counties where wildcatting was carried on, new production was found. Clay County had seven dry holes, Hickory and Marion one each; Platte, four and St. Clair, two.

Jan 1, 1939

By E. E. Thurlow

The Geology Div. of Northern Pacific Railway Co. has adapted to its exploration efforts field procedures for geochemical sampling and semi-quantitative analysis which have been developed through research by the U. S. Geological Survey. The sampling is done in conjunction with reconnaissance geologic mapping on aerial photographs or during field checking of maps which have been prepared largely by photo-geologic interpretation. Stream sediment or soil samples are taken and readily soluble combined heavy metals are extracted with ammonium citrate followed by colorimetric titration with dithizone at the sample site. The effectiveness of this approach has been demonstrated both in positive and negative results, thereby assisting in the elimination of large areas of land from further immediate attention and in providing targets for followup exploration. An occa sional sample is submitted for spectrographic analysis as a check on the possible presence of other elements of economic significance. Field laboratory procedures are also being implemented for determining molybdenum, mercury, and other metals which may be valuable in themselves or useful as pathfinder elements in outlining mineralized areas. A lead-zinc occurrence in Oregon and a copper deposit in Montana were readily detected and outlined by stream sediment and soil sampling and a heavy metal anomaly that lacks obvious interpretation has been found in northwestern Montana. Detailed mapping and additional sampling are followed by other exploration techniques if warranted. Northern Pacific's program of reconnaissance mineral evaluation of company-owned lands and adjoining areas was outlined in a paper presented at the American Mining Congress meeting in Las Vegas four years ago. That report included policies and procedures with respect to mineral development on Railway Co. lands and may be referred to for information on these matters.1 In a sense this paper is a progress report on the use of geochemical prospecting in Northern Pacific's continuing mineral evaluation program. At this time there are positive results but as yet there is no real success story in the form of a minable ore body. GEOCHEMICAL PROSPECTING PROCEDURES The decision to use geochemistry as a reconnaissance exploration tool must be followed by research into sampling and analytical methods and into the interpretation of results. Various analytical methods were tried and evaluated by the Geology Div., including hot and cold acid extraction with and without fusion of the sample, panning and magnetic separation followed by dithizone testing of the magnetite, and cold aqueous extraction of metallic ions followed by indicator tests. Samples were first sent to the laboratory for analysis; later field laboratories were established and now virtually all testing is done at the sample site. It was concluded that, where applicable, the quickest dependable methods for reconnaissance use are the dithizone field tests for readily extractable heavy metals. This involves the simultaneous treatment of a sample, usually of soil or stream sediment, with two immiscible liquids; one a cold aqueous extractant (ammonium citrate) and the other a solution of dithizone in toluene or xylene.2 Dithizone is a colorimetric indicator that reacts quantitatively with copper, lead, zinc, and several other metals to form colored complexes in organic solvents. Results may be expressed in ml of 0.001 pct dithizone that are required to reach the blue end point, or calibration of the test results can be carried out with standard solutions of zinc; conversion factors would then be expressed in ppm, zinc equivalent. Calibration of dithizone solution with zinc standards indicates that 1 ml of 0.001 pct dithizone is equivalent to approximately 0.25 ppm of zinc. An authoritative report on dithizone field tests authored by H. E. Hawkes in the June-July 1963 issue of Economic Geology* states "The appeal of these techniques has been the simplicity and speed of the determinations as compared with more tedious laboratory determinations of trace metals in weathered rocks, soils, or plant materials. This obvious appeal, however, has often been more than matched by misuse of the method in such a manner that the results are

Jan 1, 1964

By M. J. McPherson

Having worked on the thermodynamics of air/liquid-water mixtures passing through the surface fans of deep mines, I find this paper of great interest and congratulate the authors on producing it. There are two matters, however, deserving discussion. First, the authors have described the classical theory of fog formation with fogging occurring at "supersaturation." In fact, the process of fog formation begins well below 100% humidity. The more strongly hygroscopic nuclei in the atmosphere will attract water molecules and begin to grow at a relative humidity perhaps as low as 70%. The process is a dynamic one with both condensation and evaporation taking place throughout the mixture on microscopic liquid surfaces. As saturation is approached, the rate of condensation accelerates rapidly producing the familiar reduction in visibility. Hygroscopic nuclei are present in all natural atmospheres and under the appropriate conditions of pressure and temperature, will produce clean fogs. However, if the air is polluted by particulates from combustion or other processes then the resultant coagulation with growing liquid particles may produce dense (and sometimes photochemical) smogs. It is this process that is likely to occur in underground mines when moist air is cooled below dew point. Second, the authors have summarized very well the individual measures that might alleviate the problem. In particular, I agree that neither heating nor refrigerating the air, by themselves, provides a satisfactory solution. However, there is a combination of these that provides a neat and effective control of fog formation. This involves a small, self-contained refrigeration unit within a duct but without the usual external heat rejection facility. The air is cooled below dew point and, hence, dehumidified on passing over the cold evaporator coils. The heat from the condenser is rejected back into the air down-stream from the water eliminator, as shown in [Fig. 1]. The duct configuration can be designed to create good mixing at the outlet.

Jan 1, 1984

By W. E. C. Eustis

1st. THE fine iron ore is mixed with a sufficient proportion of fine coking coal, and is coked in any of the ordinary methods for making coke. The effect of this is to convert the iron oxide into sponge in such a shape that the usual trouble of oxidation is avoided. 2d. The resulting mixture of coke and sponge is melted down in an ordinary cupola, the coke furnishing more than sufficient fuel for that purpose. I may briefly point out here that in the first place the iron is sponged, and this sponge, as is well known, contain-, no phosphorus or silicon when the reduction takes place at a low temperature; and in the second place this sponge is melted down in a cupola in which there is no zone of reduction for phosphorus or silicon, and that con¬sequently the resulting iron should be free from both of these impu¬rities. 3d. The liquid sponge, now carburized, is run into an open-hearth furnace, where the requisite degree of hardness or softness is obtained by adding some of the fine ore, and the usual dose of ferronmanganose. I have merely given above the rough outlines of the process, but it is my intention, as early as possible, to bring the process more fully before the Institute.

Jan 1, 1881

By J. H. Scaff, H. C. Theuerer

Germanium may be reversibly converted from n to p type by heat treatment. Data for the conversion and the associated changes in resistreatment.tivity are given and the results are interpreted in terms of changes in the donor-acceptor balance. MEANS for controlling the electrical properties of germanium in a predictable manner are of interest because of the increasing utilization of this element as the semiconducting material in electrical devices. Since both the mechanism and the magnitude of the electrical conductivity depend upon the kind and quantity of impurities present, the conductivity usually is adjusted by first carefully purifying the germanium, and then, by standard alloying procedures, adding the elements desired. The elements usually added are from the third or fifth periodic groups depending upon whether p- or n-type germanium is desired. However, in the development of germanium rectifiers during the war, it was found that it was possible also to modify reversibly the conductivity of germanium and even to produce conversion from n to p type by heat treatment.1,5 Since then a detailed study of this effect has been made. The data are presented in this paper and an explanation is offered for the effects observed. Preparation and Experimental Procedure The method used in preparing the germanium ingots for this investigation has been previously described.' The method consists essentially of (1) reduction of GeO2* and (2) preparation of a 50-g ingot from the reduced material. Graphite containers are used in both steps. In the first step the GeO2 is reduced in hydrogen at 650 °C to form a sponge germanium which, to assure complete reduction and to obtain massive materials, is fused subsequently in the reduction furnace by gradually raising the temperature to 1000°C. The button of germanium thus obtained corresponds to a yield of 99.8 pct. The final ingot is prepared by fusion of the germanium button in a helium atmosphere. A cylindrical crucible in a vertical silica tube furnace is employed and the crucible is heated by an external induction coil. The ingot is solidified from the bottom upward by raising the induction coil at a constant rate with power to the coil kept at a fixed value. In such ingots, segregation is normal and most of the impurities are concentrated in the last region of the ingot to freeze. It follows then that the major portion of the ingot is purer than it would have been if freezing had occurred in a random fashion. Moreover the orderly advance of the freezing surface during solidification establishes in the ingot a succession of surfaces of constant composition, if it is assumed that the liquid is homogeneous and that diffusion in the solid is negligible. Therefore, some information on the distribution of impurities in the ingot may be acquired by determining the shape of the solid-liquid interface at different stages of solidification. This is of importance because the concentration of impurities will be seen to affect the response of germanium to heat treatment. Such information is difficult to acquire by direct means, for the impurities responsible for the electrical properties of germanium prepared in this way are present

Jan 1, 1952

By David P. Hale

The Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,' but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1942

By E. C. Smith

THE CHAIRMAN.-Mr. Earle Smith- has kindly offered to make some remarks in connection with segregation in the product, Mr. Smith: E. C. SMITH,* Cleveland, Ohio-I will start this off by a story of the code days of the American Iron and Steel Institute. In those days, Republic did not have a big strip mill, and the question came up of the check analysis of rimmed steel. I suggested that they let me be the chairman of the Committee on Accumulating the Information on the Variation of the Composition of the Ingots of Rimmed Steel. Somebody wanted to know why I wanted to be the chairman. I said, "We don't make any of the big ingots of rimmed steel, and no matter who makes them they are so bad that you don't dare publish the information. So if I collect it and hide it you can't charge me with having done anything that really disrupted the commercial situation. So, everybody furnished me with a rather complete story as to the horrible variations in big rimmed ingots. I took it out to my house and put it away, and it is still there. Now, segregation in the big ingot is no longer an "-academic-matter-as far as II am concerned. ¬I am in a situation like that of the German who was told in 1936 about the coming war. He said: "Until it is your throat that is going to be cut, you don't pay any attention to what is happening to the other man." That is the way with the problem that we have in front of us. Recently I have been told that the comptroller was questioning the payment for certain articles of stamped steel that had been made from rimmed steel, because upon check analysis of the rimmed steel it had been determined that these stamped articles were not within the compositions that were included in the specification, and therefore he as the comptroller had no alternative. It was not meeting the specification; therefore, no payment. So I would say to all of you: You can very seriously consider this matter of segregation now and on into the future on the basis of the fact that it is actually going to cost your companies, which are making these products, money unless there is some new idea about the infallibility of quantitative chemists who analyze some of these products or lawyers who read specifications. I don't know which man is going to be the major factor in the future. If the National Bureau of Standards could in some way show the specification writers the variation between good chemists analyzing for what they expect to be umpire results, the writers would certainly realize that some of the specifications to which we have calmly signed our names as being O.K. are well, as one man said to me, they might be filled by the devil, and they, certainly could be filled by the Lord, but they could not be filled by mankind. I would like to inject two or three things into a segregation study which I want you to think about, because I would be a little surprised if there is very much discussion of them. In the first place, we generally make steel in the United States in the basic open hearth, and I do not think there has been nearly enough consideration given to segregation within the bath before it moves into the ladle. I am sure that any of the people who handled the 9400 series of the NE series when it contained the 0.60 per cent silicon have more respect than they had previously for the segregation that is within the ladle; that is, before the metal reaches the ingot mold, the frozen ingots and the segregation in them. Another point to which I think we ought to give serious consideration is the segregation of iron oxide in the ingot-iron type of material, where the distinction between that and the steel segregation is that it is actually segregating iron oxide. Normally we are segregating some form of carbon or sulphur, or something like. that, with the stamping steel industry now coming down into the ranges of chemistry, where the segregation of iron oxide will be just

Jan 1, 1944

By R. A. Bloom, John Birtalan

CONSIDERABLE interest has been shown in recent years toward determining the crystal structure, mode of formation, and chemical composition of the x phase, designated as such by Andrews,' who was the first to establish its presence in Fe-Cr- Ni-Mo alloys . Later work2 by the same author has shown that the occurrence of x depends on the presence of some molybdenum in the alloy. The phase, which appears to be identical or very similar to a manganese, has a body-centered-cubic structure and is closely related to s phase. Koh observed a similarity in composition between x and s and speculated as to whether x might be an ordered structure of u which is known to have a tetragonal crystal

Jan 1, 1957

By C. J. Osborn

The temperature dependence of the free energies of formation of metallurgically important oxides, sulphides, chlorides, carbonates and sulphates is presented graphically, whereby the task of deriving practical metallurgical information is greatly simplified. The diagrams have been revised according to the latest available thermodynamic data. WHILE it is true that much careful investiga-tional work remains to be done, there are already available in the literature sufficient thermo-dynamic data to enable the metallurgist to predict with reasonable confidence the equilibrium conditions to be expected in most important, and potentially important, metallurgical reactions. In this connection, the careful, critical compilations of K. K. Kelley and his collaborators in numerous U. S. Bureau of Mines Bulletins are particularly valuable. However, the translation of reliable thermo-dynamic data into metallurgical language unfortunately involves lengthy manipulations of the cumbersome formulas which can be set up from heat of formation, entropy, and heat capacity data. Many years ago, Kelley20 predicted that thermo-dynamic calculations would be made in the future "with the aid of free energy, heat content, and entropy tables, rather than by means of the algebraic methods employed at present", and where such tables are available they greatly simplify the task of deriving practical metallurgical information. However, in addition to these tables, there are also available one or two reliable graphical presentations, particularly of free energy data, which may be used in the same way as the tables, but which have the added advantages that interpolation is never necessary, and that the behavior of different metals or compounds may be compared at a glance. Some years ago Professor Robert Lepsoe, Head of the Department of Metallurgy at Norways Institute of Technology (N.T.H.), began a compilation of curves showing the temperature dependence of the heat contents of the elements, and the heat contents and heats and free energies of formation of the common metallurgical compounds. With such a compilation, the thermal and free energy requirements of a reaction may be read from curves in a matter of seconds; and this statement applies not only to the formation of compounds from their elements, and to the reverse dissociation, but to any reaction involving substances whose thermodynamic properties are available. This follows from the fact that heats and free energies of formation are completely additive. For example, the free energy change associated with the chlorination of a metallic oxide at any temperature, T, is given by the free energy of formation of the chloride at temperature T minus that of the oxide also at T; both of these quantities may be read directly from curves of the type suggested above. Since this early, unpublished work of Lepsoe, both Ellingham7 and Richardson and Jeffes46 have

Jan 1, 1951

By R. J. Mellen

IN a chloridizing roasting and cyanidation plant treating a manganese-silver ore, certain experiments pointed out the way to an improvement in roasting conditions by a change in the degree of crushing. The following short article is simply a description of the various changes that were necessary throughout the plant and of the results obtained. There is nothing unusual in these changes but they are of some interest in that they constitute a good many of the alterations usually resorted to in increasing production. In the beginning, the changes were brought about by an experiment that was not successful, but which clearly pointed to means of improving the operation, and is an example of the fact that often experimental work may result in failure and still be of value in arriving at correct fundamentals. This experiment also shows how far a metallurgist can get out of line in his deductions, particularly in a field with which he is not thoroughly familiar. The ore at the plant of Compania Minera Kildun y Anexas is crushed through a 13-in. gyratory, a 3-ft. standard Symons cone crusher and a set of 16 by 42in. rolls, the latter in closed circuit with two Tyler 400-mesh screens. The crushed ore is then conveyed to two fine-ore bins. These provide storage and feed for two 6 by 90-ft. kiln roasters, which discharge directly to coolers. The coolers in turn discharge to a 6 by 12-ft. ball mill, where the ore is ground for cyanidation. Laboratory and pilot-plant tests previous to the mill construction had indicated that minus ¼ -in. crushing was satisfactory for roasting, although results did not vary greatly with some coarser or considerably finer crushing. The plant was designed for a capacity of 300 tons per day on this basis. After a few months operation, the initial operating problems were overcome and the anticipated milling rate was reached but the results being obtained were not really good. The plant seemingly did not have much excess capacity in any department but the roasting operation was the most critically limiting factor both as to tonnage and the results obtained. If this could be improved there seemed some possibility of improving the total tonnage rate to some extent. Segregation of the calcine into various screen sizes showed that the coarser sizes ,were not giving the expected recoveries. In all of the laboratory and pilot-plant testing, any limiting conditions as to the percentage of salt used, temperatures, feed rates, etc., had affected the fine material more than it had the coarse, and even in making laboratory tests at this time the mill conditions could not be exactly duplicated. Further laboratory testing indicated that a segregation of the crushed ore into a coarse and fine product for roasting might result in some improvement in roast-

Jan 1, 1945

By Bruce T. Stanley

A key point in the design and operation of a modern mining operation is the construction of what is called an ore-body model or block model. This model is a representation of reality constructed from predicted information. The blocks involved are merely subsets of the overall model which allows manipulation of the contained information on a local scale. In general, block models enable mine planners to effectively select the most promising means of extracting the ore both physically and economically. The uses of a block model can be quite diversified, but one must realize that a single model that satisfies all curiosities and forms of expertise is difficult to construct.

Jan 1, 1979

By R. J. Reynik

A semiempirial small flunctation theory of diff- sion in liquids is presented, which employs a fluctuation energy assumed quadratic for a small atomic or molecular displacement and Einstein's random-iralh model. The resulting diffusion equation is given by In these equations. D is the diffusivity, is the average liquid shite coordination number (at interatomic distance d. cm. T is the absolute temperature, xu. em, is (the diffusive displacement. K, is the quadratic fluctuation energy force constant, and rg, cm, are the radii oj diffusing atoms A and B, respectively. The quantities Xn and K are calculated from the computer-filled values of the slope and intercept. respectively. The radius of self-diffusing atom or radii and of diffusing atoms A and B are eta United and compared with values reported in the literature.. The predicted linear variation of diffusivity with. It tempera lure htm been observed in approximately thirty-iire metallic liquid systems, and in over seventy-fiee other liquid systems, including the organic .alcohols, liquified inert gases, and the molten salts, ALTHOUGH the average density within a macroscopic volume element of liquid is constant for fixed total number of atoms. pressure. and temperature, there exist microscopic: density fluctuations within the respective volume element. As such the microscopic volume available to an atom and its Z first nearest neighbors at any instant of time fluctuates above and below the average volume available to these atoms. If one assumes that liquid state atoms vibrate as in a solid. and further postulates that the mean position of any atom in the liquid state is not stationary. but shifts during every .vibration a distance 0 5 j 5 xo. then every atom in the liquid state continuously undergoes diffusive displacements which vary in the range 0 5 j 5 ro. Mathematically. for a binary liquid system consisting of atcrms A and B. the maximum diffusive displacement. .YO, is defined by the equation: where d is the average liquid state interatomic distance at specified liquid state coordination number Z. and v~ \ and vg are the effective radii of diffusing atoms A and B: respectively. For self-diffusion. r^ equals rg , and Eq. [I.] reduces to: It is interesting to note that Eq. [l] or [2] can be used to compute the radii of the diffusing atoms, provided one had an experimental evaluation of xo. As such. the computed radii could be compared with metallic or crystallographic ionic radii to ascerlain the electronic character of the diffusing atoms. Thus it is proposed that in the liquid state the n~otion of an atom relative to its original equilibrium position of oscillation represents the thermal vibration of any atom and its Z first nearest neighbors. while the small and variable displacements. 0 5 1 5 xc,. of the centers of oscillation represent the complex diffusive motions of the atoms at constant temperature and pressure. This is consistent with data obtained from slow neutron scattering by liquids1 ' and resembles an itinerant oscillator model of the liquid state.'" It is further postulated that the atomic displacements characterizing the liquid state diffusion process are essentially a random-walk process. As such. it nlay be described by Einstein's equation:' where D is the diffusivity. sq cm sec-'. j2 is the mean square value of the diffusive displacement. and i> is the frequency of density fluctuations giving rise to diffusion. FORMULATION OF DIFFUSION EQUATION The effective spherical volume occupied by an atom, as a consequence of a microscopic density fluctuation which enlarges the volume available to any atom, exceeds its average liquid state atomic volume by an amount: where AV is the enlarged spherical volume, v is the radius of the diffusing atom. and j is the elementary displacement distance from the original center of oscillation of the vibrating atom to a new center of oscillation position. For small atomic displacements. where c is a constant whose value depends upon the assumed geometry of the enlarged volume. For a spherical increase in volume, c equals 4nr2. Following the treatment of Furthl' and ~walin." assuming the enlarged volu~nes AL7 for the diffusing atoms are distributed in a continuunl. the probability of finding a fluctuation in the size range 0 5 j 5 xo defined by Where c includes the geometric constant cl and Eij) is the fluctuation energy causing the volume change. But the proposed model assumes all the Z first nearest-neighbor atoms are centers of oscillation. and hence the probability that any of these atoms is adjacent to a fluctuation of magnitude 05j5xo is unity. Thus:

Jan 1, 1970

By J. T. McGrath, R. C. A. Thurston

Poly crystalline specimens of copper, and copper with various additions of zinc, were tested in plane-bending fatigue. In tests performed at a constant stress, the fatigue life of copper increased slightly with the addition of up to fifteen per cent zinc. There was a sharp increase in fatigue life as further additions of zinc of up to 35 pct were made. Surface observations showed that the coarse slip bands that are characteristic of fatigue became narrower as the concentration of zinc increased. The rate of crack propagation also decreased with increasing zinc content. It is suggested that the fatigue behavior is controlled by cross slip processes. CROSS slip occurs when dislocations move from one primary slip plane to another along a connecting or cross slip plane. The primary and cross slip planes have a common slip direction. Wide stacking faults, having low energy, tend to make cross slip more difficult. According to recent theories, the ability of a material to cross slip is important to the formation and propagation of fatigue cracks. McEvily and Machlin2 have examined this concept experimentally by fatiguing single crys tals of lithium fluoride, sodium chloride, silver chloride, and KRS-5.* The latter two materials ex- hibit easy cross slip, while the former two do not. Normal rapid fatigue failure was obtained in the silver chloride and KRS-5 specimens, whereas it was much more difficult to achieve in sodium chloride and lithium fluoride crystals. Furthermore, numerous slip band extrusions and intrusions were found in silver chloride and KRS-5 crystals, whereas only one isolated extrusion was found in lithium fluoride and none was found in sodium chloride. McEvily and Machlin also consider that there is no clear-cut demarcation between crack initiation and propagation. The intrusion-extrusion process, which initiates crack formation, continues ahead of the cracks to allow propagation of these cracks along slip bands. The process of cross slip is therefore important not only to crack initiation, but also to crack propagation. Holden4 postulates that fatigue crack growth is dependent upon cross slip and thus upon stacking-fault energy. Using an X-ray microbeam technique, he found a cyclic subgrain structure in fatigued aluminum and a-iron. Holden suggests that micro-cracks develop in the densely-packed sub-boundaries ahead of the main crack front, and when sufficiently numerous join up to promote crack growth. The ease with which a subgrain structure could form would depend upon the ability of the dislocations to cross slip, and thus upon the stacking-fault energy. Hence in aluminum, which has a high stack-ing-fault energy and in which cross slip is easy, Holden found that the relative rate of fatigue crack propagation was considerably greater than in stainless steel, a low stacking-fault energy material. It has been shown by a number of investigators that the probability of forming deformation stacking faults in copper increases as zinc is added.5-7 Cross slip should, therefore, become more difficult as the zinc concentration is increased. In order to check the validity of the foregoing theories, it was decided to test copper and copper with various additions of zinc in plane bending fatigue, and determine to what extent their fatigue properties are dependent upon their ability to cross slip. EXPERIMENTAL PROCEDURE Fatigue tests were carried out on polycrystalline OFHC copper and various copper-zinc alloys with 5, 15, 20, 30, and 35 wt pct Zn. The Cu-Zn alloys were obtained commercially in sheet form. Test specimens, as shown in Fig. 1, were machined from sheet that had been reduced to an approximate grain size of 0.040 mm, the heat-treatment procedure being similar to that of Feltham anc copley.8

Jan 1, 1963

Jan 1, 1962

By James J. Wise

INTRODUCTION One basic design feature utilized in all caving and sublevel stoping techniques is the drawpoint. These draw- points may be located on sublevels when using sublevel caving methods, or may be located at the floor pillar when using block caving, sublevel stoping, or vertical crater retreat methods. How the drawpoint is designed and developed, how the ore is withdrawn from it, and how the ore is hauled to the shaft or portal encompasses the loading and hauling function. Historically, predominate loading and hauling equipment for caving and sublevel stoping has been scraper slushes, air powered overshot loaders, and rail mounted train haulage. All of this equipment has two common constraints. 1. The equipment locked into specific work sites and is not easily shifted to another work site. This constraint can often lead to low utilization and low productivity of the equipment. 2. The equipment is designed to work in the horizontal plane, which requires that the various horizontally-oriented working levels be connected by vertical raises. Vertical development by means of raises is not only increasingly expensive, but also is not well adapted to movement of large equipment into the s topes. In the last 20 years, two revolutionary labor saving concepts have become common in caving and sublevel stoping. 1. Long-hole drilling, which has mechanized the development of the drawpoint extraction structures as well as the actual stoping and undercutting. 2. Vertical access by means of trackless ramps between levels, and the consequent use of rubber-tired vehicles not only for loading and hauling ore, but also for the rapid movement of men, material, and equipment into the stopes. The introduction of trackless mining systems for loading and hauling has not been easy. Mine planners have had to re-orient their thinking to the larger operating space required by trackless equipment. Larger access drifts have necessitated reconsideration of mine layouts to insure proper ground support. Spiral ramp developments were often laid out on slopes steeper than the equipment could negotiate economically. Mine operators had to accept the added responsibility of roadway maintenance, water removal, increased ventilation, and more technical mechanical maintenance. As the mine operators enthusiastically embraced the superior productivity of trackless mining systems, they some- times disregarded opportunities to combine the older types of equipment with trackless vehicles to maximize productivity at lowest cost. In order to gain a proper perspective on this problem, it is necessary to review the various techniques of loading and hauling and to become more aware of the advantages or disadvantages that each system or combination contributes. LOADING Loading consists of two functions, (1) primary loading from a drawpoint and (2) secondary loading into long- haul system, a truck, train, or possibly a belt conveyor. Mine planners have four basic loading systems available to fit various operating conditions. These are, (1) gravity, (2) scrapers, (3) rail-mounted loaders, and (4) trackless loaders. Each system can produce optimum results under specific conditions. Gravity Loading Gravity loading is probably the oldest system in general use today.

Jan 1, 1981

Jan 1, 1918

By M. D. Cooper

UNDERGRADUATES in mining engineering may be prepared for work by giving them sound instruction in the courses generally considered essential to the profession. The industry is not deeply concerned about the details of those courses. The average man in the coal industry does not wish to insist upon a rigid program. Therefore, he differs little from those in the teaching profession who evidently are not unanimous in their opinions, or all college catalogs would be alike. For the good of the profession, it is just as well that there should be differences in regard to details. It appears that students graduating in mining engineering from the accredited institutions receive similar instruction. It is taken for granted that the graduate will have a good understanding of English, mathematics, mechanics, electricity, chemistry, physics, geology, and surveying, in addition to his major courses in mining. Somewhat belatedly, industry hopes he will have had at least an introduction to the subject of labor relations, the importance of which is only too clear at present. The coal industry expects, of course, that students in mining engineering will be taught the strictly mining subjects by men who have had practical experience in the mines and who keep themselves well informed in regard to current methods. While the undergraduate is subject to the control of members of the teaching profession, industry expects him to be trained in certain ways that are not a part of his textbooks, but can be made an inseparable part of his development by the skillful supervision of his teachers. Of the desired characteristics, dependability is of the utmost importance. Probably most employers would overlook certain short-comings if the young graduate demonstrated that he was thoroughly dependable. If he always appeared at the right place at the right time with the proper equipment, he would soon be well established as a welcome member of his organization. The graduate who gets a reputation for being undependable will have little opportunity for advancement. Closely allied to dependability is loyalty. Athletic teams and social groups in college tend to develop loyalty which may well be carried over into industry. This does not mean that the graduate has to be satisfied with customary practices. The average manager is glad to see the graduate make constructive criticism as long as he demonstrates his loyalty at the same time. It is important that his loyalty keeps him alert arid ready to take helpful action for the benefit of his organization, and especially to stand with it during times of stress. With or without an introduction to labor relations in college, the graduate is expected to develop ability in this most important field. Beginning with himself, he will find it essential to deal agreeably with his immediate associates. Getting along in friendly fashion with his own small group will be a great help as his responsibilities increase and he is required to deal with larger numbers of persons. On a higher scale, his interest in his community may grow at the same time by voluntary work in any one of a great number of useful activities. Industry expects the graduate engineer to be a mature man at the time he gets his first job. Supposing that he has better than average intelligence, industry expects him to continue to grow intellectually and to fit himself for responsible jobs when they are offered to him. For this reason, employers are apt to look over his college record to see what he did that would indicate his fitness for leadership. There is interest in knowing what he did beyond the requirements. As evidence of his mental growth, it is expected that the graduate will do independent thinking; that he will not take too much for granted. When he reads a report, he should develop the ability to see whether the subject is new or whether it is just a description of an old method that has been superseded by something better. For the same reason, the graduate should be able to accept conditions that have been arrived at by sound experience rather than cling to something else that seems better in theory. In this connection, it may be remarked that the ability to operate successfully a personal budget will be noteworthy, as it may be assumed that a man who knows how to conduct his own affairs will be prepared to assume the larger responsibilities of industry. Membership in AIME will indicate to the employer that the graduate is interested in the mining industry as a whole. Therefore, it is good evidence of something more than a local outlook. Quite apart from college training and mental ability, the newly employed graduate will be expected to be willing to do hard manual labor for a time. This will give him an understanding of the actual conditions of work done by those he supervises later. He will gain their confidence and be able to see that the work is carried on in a safe and efficient manner. Part of this experience may be acquired in his summer vacations during his undergraduate career. Such work would make a favorable impression on a prospective employer, especially if the graduate showed a willingness to continue it until he was prepared for something better. To summarize, the man in authority in the coal industry will not quarrel with the professor of mining engineering over details of curriculum. He will be pleased if the school sends him graduates who possess a good foundation in the courses studied, and who may be depended upon to do their work faithfully and intelligently. Such men will be ready when the time comes to assume their places as leaders of an essential industry.

Jan 1, 1951

By J. G. Eenink, R. A. Cunningham

One phase has been completed of a laboratory invesrigation of formations with relatively high permeability under conditions of overburden, formation and mud coltrmn pressures. The following statements are based on these tests within the limitations described. Drilling rate decreased when mud column pressure was greater than formation pressure. The decrease was primarily due to a layer of cuttings and mud particles held to the hole bottom by the difference in pressure. Much of the force of the bit was wasted in this layer and was unavailable for penetrating virgin formation. Adequate jet velocities helped clean the filter cake and chips away and resulted in increased drilling rate — the higher the jet velocity the faster the drilling rate. Drilling rate increased slightly when formation pres sure was greater than mud column pressure. The i11(reuse resulted from cleaning the hole bottom as formarion fluid flowed into the borehole. Overburden pressure had practically no effect on drilling rate. INTRODUCTION Some formations are difficult to drill in a wellbore hole but are easily drilled under atmospheric conditions in the laboratory. The reasons for this apparent difference in drillability are not fully understood. An increase in formation compressive strength causes a reduction in drilling rate. It has been shown by Griggs1, Handin2 and others3-1 that formation strength increases under conditions of high hydrostatic stress. Based on these results, a decrease in drilling rate would be expected with increased drilling fluid pressure in formations of low permeability having low formation fluid pressure. Such a decrease has been shown by Murray. et a1 and Eckel" This effect holds even when using nitrogcn under high pressure as the drilling fluid (unrc-ported tests from the Hughes laboratory). Poor bottom-hole cleaning may account for decreased drilling rates. Even though it may not be easily explained, evidence of poor cleaning can easily bc seen. One evidence is the increased drilling rate that accompanies decreased balling obtained with addition of oil in some muds used to drill shales.4,7,3 Many variables can affect drilling rates. These may include mud composition and properties, formation properties, bit types and operating conditions, formation fluid, mud column and overburden pressures. These must be studied a few at a time under carefully controlled conditions which simulate actual conditions as closely as possible. The purpose of this work was to investigate effect of overburden, formation and mud column pressures on drilling rates in permeable formations. These tests were suggested by conditions shown in Fig. I. Represented is a borehole drilled into a formation with relatively high permeability. In the vicinity of the hole bottom there exists a mud column pressure, P a formation fluid pressure, P and an overburden pressure, The mud has low water-loss properties and sufficient weight to more than overbalance the formation pressure. Laboratory investigation included a range with formation pressure greater than mud column pressure. NOMENCLATURE Pm mud column pressure = pressure of drilling fluid or mud at hole bottom Pf, formation pressure = pressure of fluid in intersticies of formation

M. G. CORSON.'-I am not going to discuss any of the papers presented but merely the question of season cracking of brass in general. Alpha brass has been known for nearly 500 yr. and from the very beginning a number of articles were made from sheets of this alloy by the process of spinning. Metal turning lathes were not yet known but wood turning lathes already existed and the wood turners used to make the mandrils and do the brass spinning themselves. Cases of season cracking were known even then. In 1915 I was connected with a small company doing a certain amount of brass spinning. Before the war its products never gave cause for complaint but their war-time products were cracking too frequently. The reason was, that due to the exigencies of war an excessive speed-up was attempted and the material simply could not take it. Today corrosion cracking of brass is most important in the case of cartridges for small arms ammunition and shell cases for large guns. The cracking takes place in storage and too frequently it is explained by the hypothetical presence of vapors of ammonia. However, I had the experience of purchasing some 20,000 rounds for the old Vetterli rifle from the Swiss government in 1905. The rifle and the cartridges were obsolete for many years and those which I bought were stored for at least 10 yr. None of them was found to be cracked or to crack in use. And the reason again was in the amount of work used in manufacturing the cartridges between anneals. The machinery today is more powerful and the amount of

Jan 1, 1945

By P. I. Brooker

The semi-variogram, the basic tool of geostatistical estimation procedures, must itself be estimated from the available data. From a numerically simulated two-dimensional deposit, with known variability expressed through its semi-variogram, the standard arithmetic mean estimator is used to calculate experimental semi-variograms. These are determined on a series of data sets obtained from the deposit with various sampling grids that cover different areas of the deposit and have a mite range in the number of available data. The orders of discrepancies between estimated and theoretical semi-variograms are determined in this idealized situation; and this provides a basis against which to assess experimental semi-variograms made on field data.

Jan 1, 1984