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IN order to make his work easier, every master of any art whatever keeps always to the road that he has learned or that his skill or good judgment has shown him to be the best. Although there are various methods used in making moulds for guns, depending on whether they are large or small, nevertheless almost the same road is traveled in all. You must first know that it is necessary to make a pattern of wood or clay exactly as the gun is to be, with those ornaments of cornices and rings that you wish to be in the bronze. Let us suppose that you wish this pattern to be of wood. You must try to have for this a piece of fir as long and thick as you wish, dry, solid, and well seasoned, with few or no knots if possible. This should be longer than the gun by the length of the head and foot rests where it is pivoted [83v] so that it can be turned as on a lathe. On the end where the mouth is to be it should project out enough so that you can attach a feeding head at the top of the casting. You can make or have this pattern made round, fluted, spiral, or half fluted, as you like best, making the measurements exactly correct with all care and attention. Then two bearing trestles must be fixed firmly in the ground, one at the head and one at the foot, as is usually done with roasting spits and as you see drawn here. This done, if it is fluted, put the cornice pieces at the place where you wish the mouth to be and at the foot where the fire is applied. These are

Jan 1, 1942

By Philip B. Bucky

THE Mining Methods sessions, one of which was run jointly with the Industrial Minerals Division, were fortunate in having a number of exceptionally fine papers. At the Tuesday session R. P. Smith presented the results of six years' experience with prepaid medical care for the employees of the Hollinger mine. It was felt that this paper was a real contribution to the cross field of mining-medicine, and the presentation was exceptionally well done. Olof V. Lindqvist acquainted us with the consider- able progress made in blast-hole diamond drilling in recent times, especially in Canada. The opening of a mine is always a matter of considerable interest and the description of the procedure and problems encountered in opening the Mather mine of Cleveland Cliffs Iron was presented by L. C. Moore.

Jan 1, 1944

By Kenneth Schellinger

THE terms surface tension and surface energy are well known when applied to liquids and are generally described by referring to the excess energy of the air: liquid interface as a result of unsaturated molecular forces surrounding the surface molecules of the liquid due to the presence of the air phase on one side. Such unbalanced forces produce the familiar water droplet of spherical form and are generally summed up as a surface tension measured in dynes per centimeter which can be shown mathematically to be equal numerically to a corresponding surface energy expressed in ergs per square centimeter. A specific surface energy, however, is best thought of as the energy necessary to produce one unit, of new surface on a substance. Hence, in producing a bubble in a flotation cell the impeller must supply surface energy corresponding to the air: liquid interfacial area on the interior of the bubble. Inasmuch as it is relatively easy to extend or contract the surface of a liquid, there are a number of successful methods for liquid surface tension, or energy, measurement based upon surface deformation. This happy state of affairs does not, however, extend to solids, which are considered to possess surface energies for the same reasons as do liquids, i.e. because of unsaturated ionic bonds at the solid: gas interface. As in the case of the flotation cell producing surface on liquids as new bubbles, it takes energy to produce new surface on solids as new particles. As every mill man knows, this surface is produced on mineral solids in a grinding mill by the action of a tumbling mass of iron balls. But here so much energy usually is wasted by the inefficient action of these balls that a large amount of heat is generated, and the surface energy production may be easily confused with the energy necessary to produce this ineffective heat. The tumbling balls and fracturing minerals ultimately take their energy from a rather large electric motor. It has been variously estimated that from 10 to 20 pct'" only of this energy from the motor does not appear as heat and may be presumed to appear as surface energy on the min- erals present. Such a production of new surface on the mineral phases is accompanied, of course, by a size reduction that is inevitable as more and more mineral interior molecules become surface molecules by the fracture exposure. This size reduction of mineral particles, although the most obvious feature and perhaps the sole object of the milling operation, is from this energy viewpoint the outward manifestation of the production of surface energy only. Measurement of the characteristic surface energies of pure minerals and their various mixtures in ores would be a step towards understanding of the energetics of the commercial grinding operation. In addition, the characteristic surface energy of a mineral is probably a physical property specific for that mineral, and therefore, from a scientific standpoint, should be measured. It is interesting to note that, in contrast to the large body of work on the surface tensions of liquid systems and biological systems, the field of solid surface energies has been neglected. Prior to 1920 it is difficult to find more than one or two references to work on solid surface energies in Chemical Abstracts. Since 1920 such references number somewhat less than 100, while those on liquid systems are numbered in the thousands. Much of this apparent neglect of the field of solid surface energies (the term is intended to be somewhat inclusive at this point and refers both to the solid: gas, and the solid:liquid interface) is because of the lack of a reliable method of measurement rather than any lack of scientific curiosity. It was, and still is, difficult to produce new surface on a solid without the simultaneous production of interior changes in the same solid which may consume part of the energy used. The extension in the surface area can be measured, but the interior crystal-

Jan 1, 1953

By Kenneth Schellinger

THE terms surface tension and surface energy are well known when applied to liquids and are generally described by referring to the excess energy of the air: liquid interface as a result of unsaturated molecular forces surrounding the surface molecules of the liquid due to the presence of the air phase on one side. Such unbalanced forces produce the familiar water droplet of spherical form and are generally summed up as a surface tension measured in dynes per centimeter which can be shown mathematically to be equal numerically to a corresponding surface energy expressed in ergs per square centimeter. A specific surface energy, however, is best thought of as the energy necessary to produce one unit, of new surface on a substance. Hence, in producing a bubble in a flotation cell the impeller must supply surface energy corresponding to the air: liquid interfacial area on the interior of the bubble. Inasmuch as it is relatively easy to extend or contract the surface of a liquid, there are a number of successful methods for liquid surface tension, or energy, measurement based upon surface deformation. This happy state of affairs does not, however, extend to solids, which are considered to possess surface energies for the same reasons as do liquids, i.e. because of unsaturated ionic bonds at the solid: gas interface. As in the case of the flotation cell producing surface on liquids as new bubbles, it takes energy to produce new surface on solids as new particles. As every mill man knows, this surface is produced on mineral solids in a grinding mill by the action of a tumbling mass of iron balls. But here so much energy usually is wasted by the inefficient action of these balls that a large amount of heat is generated, and the surface energy production may be easily confused with the energy necessary to produce this ineffective heat. The tumbling balls and fracturing minerals ultimately take their energy from a rather large electric motor. It has been variously estimated that from 10 to 20 pct'" only of this energy from the motor does not appear as heat and may be presumed to appear as surface energy on the min- erals present. Such a production of new surface on the mineral phases is accompanied, of course, by a size reduction that is inevitable as more and more mineral interior molecules become surface molecules by the fracture exposure. This size reduction of mineral particles, although the most obvious feature and perhaps the sole object of the milling operation, is from this energy viewpoint the outward manifestation of the production of surface energy only. Measurement of the characteristic surface energies of pure minerals and their various mixtures in ores would be a step towards understanding of the energetics of the commercial grinding operation. In addition, the characteristic surface energy of a mineral is probably a physical property specific for that mineral, and therefore, from a scientific standpoint, should be measured. It is interesting to note that, in contrast to the large body of work on the surface tensions of liquid systems and biological systems, the field of solid surface energies has been neglected. Prior to 1920 it is difficult to find more than one or two references to work on solid surface energies in Chemical Abstracts. Since 1920 such references number somewhat less than 100, while those on liquid systems are numbered in the thousands. Much of this apparent neglect of the field of solid surface energies (the term is intended to be somewhat inclusive at this point and refers both to the solid: gas, and the solid:liquid interface) is because of the lack of a reliable method of measurement rather than any lack of scientific curiosity. It was, and still is, difficult to produce new surface on a solid without the simultaneous production of interior changes in the same solid which may consume part of the energy used. The extension in the surface area can be measured, but the interior crystal-

Jan 1, 1953

By A. L. Field

This general subject has been so thoroughly discussed by Dr. Herty and his associates, especially with regard to the degree of oxidation of the metal at the time that the silicon pig or spiegel is added, that I am not going to spend much time on that today. I should like to propound a question, which is based on my own observations made some years ago while with a large alloy-steel company which had two open-hearth furnace plants. It is true that one of these plants was not engaged particularly in making alloy steels, but there were certain relations between slag and metal composition which appeared to me to be entirely different in the two plants. I have an explanation for it that is more or less incomplete, but possibly Dr. Herty or Mr. Reinartz or some of the others may be able to complete it. Suppose we take our three layers; the metal on the bottom, on top of that the slag, and on top of the slag, the gas. We cannot overlook the gaseous phase. Regardless of the effect of the iron oxide in the slag on the rate of carbon elimination—and that, of course, is rather important in alloy practice since it is not desirable to have the carbon dropping too rapidly at the time the deoxidizing is had in the furnace—it will probably be admitted that it depends on the iron oxide in the metal for a given carbon oxide. I have seen cases where with approximately identical metal and slag compositions one furnace would work twice as rapidly as another in removing carbon. Of course, there is some explanation of this in what others have already said, that the question of the exact lime and silica content of the slag determines the activity and viscosity of the slag; but I am convinced, without having reviewed the actual records since I was asked to make this talk, because they were not available at the time, that the slags in these two furnaces were not materially different. Putting it another way, one furnace would have

Jan 1, 1935

By A. L. Field

This general subject has been so thoroughly discussed by Dr. Herty and his associates, especially with regard to the degree of oxidation of the metal at the time that the silicon pig or spiegel is added, that I am not going to spend much time on that today. I should like to propound a question, which is based on my own observations made some years ago while with a large alloy-steel company which had two open-hearth furnace plants. It is true that one of these plants was not engaged particularly in making alloy steels, but there were certain relations between slag and metal composition which appeared to me to be entirely different in the two plants. I have an explanation for it that is more or less incomplete, but possibly Dr. Herty or Mr. Reinartz or some of the others may be able to complete it. Suppose we take our three layers; the metal on the bottom, on top of that the slag, and on top of the slag, the gas. We cannot overlook the gaseous phase. Regardless of the effect of the iron oxide in the slag on the rate of carbon elimination—and that, of course, is rather important in alloy practice since it is not desirable to have the carbon dropping too rapidly at the time the deoxidizing is had in the furnace—it will probably be admitted that it depends on the iron oxide in the metal for a given carbon oxide. I have seen cases where with approximately identical metal and slag compositions one furnace would work twice as rapidly as another in removing carbon. Of course, there is some explanation of this in what others have already said, that the question of the exact lime and silica content of the slag determines the activity and viscosity of the slag; but I am convinced, without having reviewed the actual records since I was asked to make this talk, because they were not available at the time, that the slags in these two furnaces were not materially different. Putting it another way, one furnace would have

Jan 1, 1935

Kaolin deposits in Georgia lie in a belt that stretches across the central part of the state from Alabama to South Carolina. In 1977 the state's kaolin production was an estimated 4.58 million tons (5.05 million st) or 77% of US production. While mining methods vary, stripping contractor W. F. (Billy) Jackson of Wrightsville, Ga., depends on a fleet of 18 twin-engine elevating scrapers to move the hulk of overburden and clay. Owner Billy Jackson explains that the soil in this part of the state is perfect for scraper operation; overburden ranges from Georgia red clay to a sandy gumbo material. Apart from some shale, very little rock is encountered, thus eliminating any blasting re¬quirement. Most of the material can be removed with cutting edge teeth or with drop center blades.

Jan 6, 1978

By Gustav S. Preller, A. M. Gaudin

Fox the past 20 years it has been generally accepted that the flotation process is made possible as a result of the action of certain chemical substances on the surface of the mineral particles. In fact, it has been suspected, but never demonstrated, that this action produces on the mineral particles a layer of chemosorbed ions that is of the order of magnitude of a monolayer; that is, of a layer one ion deep. It is the purpose of this paper to present certain initial results on the relationship of mineral surface area and collecting-agent requirements. Up to about eight years ago, all considerations involving the surface area of finely divided solids were-limited by the fact that there was not in existence any general method for determining the extent of such surfaces, especially on mixed materials. However, the method invented by Brunauer, Emmett and Teller1 has changed the situation by providing a general procedure (BET method). This procedure has already been applied to mineral dressing problems2 -4 and has now received confirmation as to accuracy by an entirely independent method.5 This confirmatory or "absolute" method uses a very tedious calorimetric procedure and is not suitable for routine determinations; but still another method6 now is available to relate the results obtained by the BET method to those obtained calorimetrically. This Harkins-Jura method has the advantage that it does not require an assumption concerning the parking area per molecule of adsorbate (nitrogen). In the original work by Brunauer, Emmett and Teller the parking area per nitrogen molecule was calculated to be either 13.8Å2. or 16.2Å2. according as the nitrogen was assumed to be closely packed as in crystalline nitrogen or loosely packed as in liquid nitrogen. The initial experimental work from this laboratory2 supported the 13.8Å2. figure; that work was done on glass spheres of measurable geometric area and it was based on the assumption that the glass spheres were truly smooth; any deviation from this assumption would, of course, have made the calculated parking area higher. Harkins and Jura's results suggest that the parking area is not the same for all substrata; furthermore, the average of the 87 measurements cited indicates a "preferred" parking area for the nitrogen molecule of about 15.2Å2., with extreme values at 13.7 and 16.9Å2. The average of 21 determinations made in connection with this study' gave a parking area of 14.3 ± 0.27Å2. In view of this result and of the Harkins and Jura

Jan 1, 1946

The difficulty of finding new ore bodies, the complexities of patenting them when they are found, and the absence of incentive legislation for exploration have limited mining exploration in the United States mostly to the big companies. This situation, coupled with ECA spending abroad, has caused American capital to look outside our national boundaries for investment opportunities which are further made attractive by some relaxing of restrictions to gain American dollars and patronage.

Jan 1, 1950

By R. V. Ramani, T. V. Falkie, T. E. Wilson

In order to increase the efficiency of underground coal operations, it is necessary to understand not only the operating system in detail, but the interrelationships between system components and the operating environment. With such an understanding comes more exact application of simulation and other operations-research techniques to plan and operate mining systems. One aspect of the coal-winning system in need of better definition, namely, the performance of continuous miners, is dealt with in this paper. Detailed discussion of this research will be found in a report by the authors. Mining Rate The performance of continuous miners-that is, the rate at which miners can deliver coal from an underground face to the outby transportation system-is dependent upon the geometric and geological conditions of mining, the characteristics of the mining machinery, and the skill of the machine operators. In order to predict mining performance, it is necessary first to identify these factors, secondly to devise a data-collection technique, and lastly, to select a method of data analysis for drawing meaningful conclusions. Factors Affecting Mining Rate: The factors that affect the mining rate can be conveniently grouped in the following four categories: Geological Factors-The natural conditions such as seam thickness, hardness, and cleavage. Geometrical Factors-The height and width of the entries and the angle of drivage with respect to the main entries. Machine Factors-The mechanical characteristics and physical dimensions of the machine, condition of the machine, condition of the bits, and related items. Other Factors-Operator efficiency, size consist of cutter product, etc. A classification such as given here is not rigid; some of the factors can be included in more than one of the categories and some can be combined as ratios. Data Collection The empirical nature of this investigation required measurements of variables under operating conditions in underground coal mines. A majority of the variables measured were continuous over a specific range of values; for example, the "width ratio" varied in practice from 0.25 to 1.00. "Dummy" values were assigned to certain operational variables in order that the variables would have numerical expression, i.e.: [ ] Data Analysis The method of analysis was to test a large model containing potentially significant variables and then reduce the model to one containing only the essential significant variables. The procedure of "scanning" a large proposed model and subsequently condensing the model consisted of two cycles of the same series of computational procedures. Correlation analysis, factor analysis, and regression analysis were the three statistical procedures that were used to derive the rate-generating equation. Correlation and Regression Analysis: Multiple linear correlation coefficients between all of the variables were calculated using the Pearson product moment formula along with the statistical significance of the correlation

Jan 1, 1975

By W. Spencer Hutchinson

It is the purpose of this paper to describe a method used to determine the corundum contents of samples of hard crystalline gneiss containing both corundum and red garnet. A chemical analysis of the rock for alumina would not fix the amount of corundum became at least three other constituent minerals of the rock, mica, feldspar, and garnet, contain alumina combined with silica. Following are the principal minerals found in the samples, together with their specific gravity and hardness as given by Dana: The corundum occurred in crystals of a gray or bluish gray color, in minute grains and coarser up to 0.5 in., and no massive or block corundum was observed. The larger crystals were commonly quite slender, well defined, and the normal hexagonal form clearly developed. They lay with the structural planes of the gneiss, and sometimes appeared prominently in relief on weathered surfaces. In some cases these crystals had suffered partial or total alteration to mica, margarite, or other soft minerals, a condition illustrated by sample D, which appeared to be studded abundantly with corundum on the flat faces. Garnet, a striking feature of nearly all the samples, was present in small rounded crystals of a pink to red color. The samples were first broken to pass a No. 4 mesh screen. This was done with a hammer on an iron plate, particular care being taken to avoid the breaking of the crystals finer than need be to pass the screen. A portion of the sample weighing 500 g. was then taken and, with a little water added, was scoured round and round in an iron bucket with a wooden block, until the coarse crystals of corundum were cleaned of adhering pieces of mica. The bucket was then re-

Jan 1, 1914

By J. J. Bodmer

In 1855, Franz Uchatius patented, in England, his process of manufacturing cast steel. The first experiments, on a practical scale, were made at the Ebbw Vale Iron Works, Monmouthshire. The charge consisted of a mixture of cast iron with about 20 per cent. of a pure iron ore, and with or without other ingredients. In order to obtain the cast iron in a subdivided condition, Uchatius granulated molten pig-metal by running it into water, which during the operation was kept well agitated, and found that "the finer the iron is granulated, the softer will be the resulting steel." The writer is not aware that granulated iron has been used practically, otherwise than in the above-named process; and until 1866 no other process of subdividing iron than by granulation was known. In April, 1866, an English patent was obtained by the writer for subdividing blast-furnace and other slags and metals in a molten condition, by passing the same through one or more pairs of rolls. In reference to iron the idea was, in following up the direction pointed out by the Uchatius process, to obtain better results in the puddling process by means of a thorough amalgamation (not simply a mixture) of the iron with the oxides and other ingredients in the charge itself. Experiments were made. A quantity of iron direct from the blastfurnace was subdivided (or laminated) by passing it through a pair of plain rolls. The rolls were hollow, and water was made to pass through them to keep them sufficiently cool. Without giving differential speed to the rolls, sheets were obtained about one-sixteenth inches thick, and from about one hundred square inches surface, downwards. With differential speed, the iron falls from the rolls in

By H. A. Schlesinger

Various studies have estimated that for the next few decades, about half of all new power plants will be nuclear. The other half will be fueled with coal. Pending legislation on air pollution control would require all new coal-fueled power plants to install stack gas scrubbers or other technology to reduce sulfur oxide (SO,) emissions. These regulations would require flue gas desulfurization (FGD) or other technology for SO, reduction even on lower sulfur western coals. Among the options for FGD are single or dual alkali throw away processes using lime or limestone as the major reagent. These processes are currently more economically attractive than recovery processes, such as magnesium oxide and Wellman- Lord, that produce a salable product such as sulfur or sulfuric acid. One of the major problem areas with the throw away processes is disposal of the thrown away solid wastes, primarily calcium sulfite (CaSO3) and calcium sulfate (CaS04). Coal ash also must be disposed of, even if SOx reduction is not required. This paper addresses the alternatives for handling and disposal of throw away lime, limestone, and dual alkali process solid wastes. Advantages, disadvantages, and the economics of various methods are discussed. Both large central station power plants (500-1000 MW capacity) and smaller industrial power plants (up to 100 MW capacity) are considered. High sulfur eastern coals (53% S) and lower sulfur (3 1% S) western coals are considered.

Jan 1, 1981

By Donald P. Richards, John F. Abel

Geotechnical site investigation for new mine shafts can reduce the level of design uncertainty for shaft linings. The parameters which determine the lining strength required include rock strength and hydrologic properties, the in situ stress conditions, and the concrete strength. These parameters are applied to analytical methods of shaft lining design using the plastic and clastic assumptions of rock response to determine the required lining thickness to maintain the stability of the shaft excavation.

Jan 1, 1982

By AIME AIME

ONE test is worth a thousand expert opinions, say the engineers of the John A. Roebling's Sons Co. of Trenton, N. J. Confronted with the job of building the cables for the new Hudson River Bridge between Fort Lee and upper Manhattan, the Roebling organization, in spite of its long and varied experience in building cables for suspension bridges of various sizes, recognized that old yardsticks would be of little value in estimating safety factors for the immense span across the Hudson.

Jan 1, 1929

By Gregg A. Scott

Upper Stillwater Dam is to be a roller-compacted concrete gravity structure, founded on nearly horizontally bedded sandstone and argillite rock. An overview of the testing and analyses used to evaluate the adequacy of the foundation relative to deformation, seepage, and stability is presented.

Jan 1, 1984

By Robert W. Hunt

Having had some twenty years' experience in trying to make good Bessemer steel rails, and now devoting my thoughts and energies to seeing that other people seek the same end, I venture to lay before the Institute some of the conclusions deduced from my practice and observation.

Jan 1, 1889

By Richard Dunmore

Tests of the MRDE firedamp prediction method have been carried out in a number of longwall districts with different conditions. The method itself and its development have been described previously At many test sites the prediction has been good, i.e. the calculated gas emission levels have agreed with measured values, averaged over a period of many weeks, within a few percent. In other cases, where there have been larger discrepancies between calculation and measurement, investigations have shown that these may be attributed to particular conditions of mining or geology. Recognition of these conditions in advance of mining is clearly desirable to improve the accuracy of the initial prediction. It has been shown that variations in gas emission rates depend largely on coal production in terms of the weekly advance of the coal face. Although there appears to be a random element present, variations in gas emission levels calculated from changing face advances agree well with measurement. The accuracy of prediction therefore depends on how well face advance can be forecast and needs to be updated as the working proceeds in the light of the face performance actually achieved. Continuous monitoring of the mine environment provides the information necessary to compare actual gas emission with predicted levels, and computerised systems make it possible to carry this out in real time. Predictions can thus be adjusted to take account of emission levels measured in previous weeks These adjustments, whether they are made after the first few weeks or subsequently during the district life, would also be used to alert management to particular abnormalities or significant changes in gas emission.

Jan 1, 1982

By Gerald Laswell

Jan 1, 1976

By Koehler S. Stout

At today's mineral prices, unproductive or low productive work in any underground mine must be kept at a minimum to insure a profit. Improper level and raise spacing can be one of the contributing factors to high production costs, and little can be done to reduce these costs after the spacing interval has been chosen. The objective in selecting level spacing is to find the most desirable interval which produces ore at the least cost per ton while still operating within the highest margins of safety and efficiency to the workmen. In addition, maximum possible recovery of ore under the conditions must be attained.

Jan 11, 1962