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By Fred C. Bond

The Standard method of determining the crushing resistance of rocks consists of crushing prepared shapes under slow compression, and expressing the ultimate crushing resistance at the load causing failure in pounds per square inch of cross-sectional area perpendicular to the crushing force, with the height approximately equal to the diameter. One-inch cubes or cylindrical drill cores are commonly used. Cubes and drill cores are cut by a highspeed steel disk with diamond dust embedded in the edges, and running under a water spray. such a saw will cut one square inch or more of hard stone per minute. An oiled, spherical, swivel compression block of small diameter should be used to equalize the pressure. Each sample is crushed between sheets of cardboard or blotting paper extending about one-half inch beyond the edges of the stone. A cloth is wrapped around it to prevent dangerous explosive shattering. It is probably preferable to place the swivel block below the specimen, with either a rigid head or another swivel block above. Whatever the arrangement, the conditions should be selected that will develop the maximum crushing strength of the specimen, even though its top and bottom planes may not be precisely parallel. The cardboard pads may be dispensed with if the ends of the specimens are polished smooth. The use of lead pads was discontinued because of the observed tendency to split the material. The samples are weighed and measured before breaking, and the density is calculated. Cubes that contain bedding lanes or veinlets are usually placed with these vertical and parallel to the crushing force, in order to develop the maximum resistance possible. A number of compression tests were made on Canadian ores, by Forrest Nagler, of the Allis-Chalmers Manufacturing CO., and are listed alphabetically in Table I. These tests were made on one-inch cubes or on diamond-drill cores approximately one inch in diameter and One inch long. The drill cores represent virgin rock, while the cubes may have been previously weakened by explosives. compression tests have been made in the Allis-Chalmers Milwaukee Laboratory on a number of ores and other materials. These are listed alphabetically in Table 2. In test NO. 1339, on limestone from the Hanna Coal Co., comparison was made between 2 by 2-in. diamond-drill core segments and one-inch cubes cut from the cores in the same strata. Results for the cylinders are tabulated directly below those for the cubes. The bedding planes were normal to the compressive force in breaking the cylinders and parallel in breaking the cubes, which accounts for the lower strength obtained from the cylinders. The percentage of net linear compression at the ultimate pressure was measured in test No. 1055 for Fontana TV A quartzite as 0.30 for cube A, and 0.37 for cube D.

Jan 1, 1947

By J. K. Edgar

FOR a number of years the production and use of super-purity aluminum (better than 99.99 pct) has been steadily increasing. High-grade lots of such aluminum show certain outstanding characteristics not found in lower grades containing principally silicon, iron and copper as impurities. One such characteristic is the so-called "self annealing," that is, the recrystallization of the heavily cold worked metal at room temperature.' Interest therefore is aroused as to the effects of the impurities. It is well known that the amounts of silicon and copper which occur in aluminum of better than 99.95 pct are completely soluble, at least at elevated temperatures (above 200°C). Iron, on the other hand, is known to be fairly insoluble in solid aluminum. Thus, a knowledge of the limits of this solubility would be of considerable use in studying the characteristics of the high purity metal. All investigators have agreed that iron has very low solubility in solid aluminum. Rosenhain, Archbutt and Hanson2 reported traces of an aluminum-iron phase in the "purest samples of aluminum obtainable." Gwyer and Phillips3 reported that an iron constituent was visible under the microscope in metal containing ".0088 per cent iron." Roth1 found that in the solid state the solubility of iron in high purity aluminum was 0.01, 0.01, 0.017 and 0.022 pct at 225, 320, 500 and 600°C respectively. Dix5 working with alloys containing less than 0.03 pct impurities, concluded from microscopic and chemical analyses of eutectic areas that the eutectic composition was close to 1.7 pct iron. Dix placed the eutectic temperature at 655°C'. Archer and Fink,6 using high purity aluminum-iron alloys, found that the hypoeutectic liquidus intersects the eutectic horizontal at 1.7 pct. This is in fair agreement with the investigation of the aluminum-iron system by Gwyer and Phillips who placed the eutectic at 1.89 pct iron with a freezing point of 653° PREPARATION AND CHEMICAL ANALYSIS OF ALLOYS Electrolytically refined aluminum (99.991 pct aluminum) and a high purity aluminum-iron alloy (11.45 pct iron) were used in the preparation of the alloys for this investigation. To aid in controlling the iron content of the experimental alloys, an alloy of lower iron content was prepared first from these materials. The high purity aluminum was melted and heated to about 700°C in a plumbago crucible coated with alundum cement and the aluminum-iron alloy was then added. The alloy was thoroughly stirred, fluxed and skimmed and then chill-cast into notch bars. The analyses of the three materials are given in Table I. The alloys for the determination of the solid solubility of iron in aluminum were prepared by melting 600 g total of the aluminum plus the required quantity of the aluminum-iron alloy (No. 92531). These

Jan 1, 1948

The war story of the engineer corps at home and in France is told officially for the first time in the advance sheets of the War Department's brief history of American war efforts. Many of these accomplishments have been published before as isolated incidents, but they gave no idea of the extraordinary duties modern warfare has laid upon engineering troops. In the engineering units that reached the other side, there were seven regiments and two battalions of railway construction engineers; five battalions for maintenance of way; two battalions for maintenance of railway equipment; four regiments and one battalion to operate the main American railways in France; three regiments to operate light railways and their repair shops; two regiments to operate the regular railway repair shops; two regiments and six separate battalions on general construction work; two regiments for storing and transporting engineer supplies; a forestry regiment; a light-railway construction regiment; a roadbuilding regiment; a water-supply regiment; a mining regiment; a quarrying regiment; a technical regiment for surveying and sound ranging; three survey and printing battalions; two railway transportation battalions; an electrical and mechanical regiment; several separate companies to operate cranes; a camouflage service; five inland waterway companies, to operate canal boats and the like; five pontoon trains and a pontoon

Jan 6, 1919

By P. E. Baker

An improved method of logging formation density has been developed in which the formation is bombarded with a collimuted beam of gamma rays. By means of a scintillation detector and pulse height discriminator, the gamma-ray energy band is accepted and recorded which corresponds to deepest penetration into the formation. Laboratory tests on a field tool revealed no borehole diameter effect for smooth holes and no effect of formation chemistry, except insofar as chemistry affects density. In extensive field tests, the density log has exhibited satisfactory agree-ment with core measurements and has correlated accurately with other logs. INTRODUCTION This paper describes an improved method of logging formation density by means of back-scattered gamma rays to penetrate the formation together with energy discrimination to select only that energy (or frequency) range corresponding to deepest penetration into the forma- tion. This method of density logging was developed at the La Habra laboratory of California Research Corp.* Field instruments have been built and tested by McCullough Tool Co. and commercial service has begun in some areas. All of the data discussed here were obtained for the original field tool. The density log can be a valuable adjunct to existing logs because of its use in determining porosity quantitatively. It is useful also in connection with seismic and gravity surveys where formation density information is of interest. PHYSICAL PRINCIPLES The intensity, I, of a beam of gamma rays after traversing a distance, x, in an absorbing medium is given by I = loe -ax where I, is the intensity of the beam entering the medium and a the attenuation constant or macroscopic cross section of the medium for gamma-ray absorption. The macroscopic cross section depends on the number and types of atoms per unit volume and the gamma-ray energy. In brief, it is the sum of the atomic cross sections of all atoms per cubic centimeter. The density of the material is the sum of the masses of all atoms per cubic centimeter. Thus, the density and the macroscopic cross section for gam-ma-ray absorption vary in propor- tion to the number of atoms per cubic centimeter. The density of the material increases, of course, if the atomic masses increase without a change in the number of atoms per cubic centimeter. When the density increases in this latter way, the macroscopic cross section increases also, but disproportionately. This results from the fact that part of the gamma-ray absorption arises from the photoelectric effect and the pair-production effect**, which are proportional to the sixth and to the second power, respectively, of the atomic number of the absorber. The remainder of the absorption results from the Compton effect, and is directly proportional to the atomic number. The gamma rays that undergo Compton scattering are not immediately absorbed. Since these rays are scattered in all directions, a fraction will emerge from the face of the medium at which they entered. If a gamma-ray shield is placed between the source and detector, most gamma rays reaching the detector will be those scattered out of the medium. The intensity will depend on absorption and scattering in the medium, and so indicates the density of the medium. For gamma rays for which Compton scattering prevails, the intensity

Jan 1, 1958

By Philip B. Dettmer

Up to now we have spoken optimistically of the many potential savings in capital and operating costs to be obtained from the selection of larger diameter and horsepower grinding mills. Such mills may well be the correct choice for one grinding plant but could be absolutely wrong for another plant. It is emphasized here that many significant factors other than the capital cost, labor, grinding media and power savings are involved in the sizing and selection of the optimum grinding circuit. The following discussion covers some of these factors and their relationship to larger mill design. The first consideration is: What is the grinding circuit supposed to do? In most instances it is one or both of the following: 1. Grind the feed material fine enough to liberate the desired minerals but with a minimum of over- grinding. Examples are preparation of ore for flotation, gravity separation, etc. 2. Grind to some pre-specified particle size or particle surface area. Examples of this are cement manufacture or the preparation of feed material for pelletizing; other examples are preparation for chemical reactions or ceramic manufacture.

Jan 5, 1965

By C. R. King

Most of the acid volcanic glasses such as obsidian, perlite, pitchstone, pumice, and pumicite (volcanic ash) are susceptible to some expansion if suddenly subjected to a suitably high temperature in a properly designed furnace, and subsequently suddenly cooled. Expansion results from the action of chemically combined or dissolved water expanding as a vapor within the softened heated rock particles. This expansion forms countless minute bubbles within the pasty mass of the natural glass particles. If the particles are cooled before these bubbles can escape, the resulting products are cellular, more or less spherulitized glass froths or hollow glass spheres of many types. Chemically, they are essentially aluminum silicates containing about 70 to 75 pct silica, 10 to 16 pct alumina, and 2 to 7 pct sodium plus potassium oxides. They are relatively resistant to attack by acids or alkalies, are resistant to heat up to over 1000°F, and are completely inert to insect or fungus attack. These products are of great potential value in many branches of industry as insulation materials, aggregates, fillers, abrasives, and additives. By proper selection of the perlite rock type and control of processing conditions, expanded perlite of a bulk density varying from about 2 to 20 Ib per cu ft can be • made. The physical properties of the particles comprising a product of a given bulk density also may be varied within wide limits of porosity, water absorption, and crushing strength. In general, crushing strength of expanded perlite increases in direct relation to increase in bulk density, but insulating value varies in inverse ratio to bulk density. The selection of a particular grade of expanded perlite for a given use as an aggregate is therefore always a compromise between insulating value, lightness, and friability. If porosity and water absorption are factors affecting the use of the material, factors other than bulk density are important. Some types of perlite rock tend to decrepitate excessively during expansion, resulting in a highly porous or even hygroscopic product of high friability relative to the bulk density of material produced. In general, treatment of any good perlite rock below the temperature necessary for maximum expansion, or insufficient time in the hot zone of the furnace for effective heat penetration to the core of the rock particles will result in some decrepitation and high porosity in the expanded product. On the other hand, exposure of the material to the temperature required for optimum expansion for a period of time slightly longer than that necessary for proper heat absorption will result in a slightly heavier product of extremely low porosity, i. e., a glazed surface. It is beyond the scope of this paper to describe in detail the rock types and processing methods used to produce the many types of expanded perlite in present use, or that may be produced to fill the present and future needs of industry. A few phases of the economics involved in processing and selling products made from this abundant and cheap mineral raw material, plentifully distributed in large and relatively accessible deposits in most western states and in other areas within economic shipping distance of large centers of consumption, will be treated with particular reference to the Los Angeles area. Relation of Balk Density to Use and Cost of Production Perlite differs from most other lightweight aggregates and fillers in that the raw material (perlite rock) may be quarried much as rock arid sand is mined, and then shipped into consuming areas as crude rock in open gondola cars at correspondingly low freight rates and handling costs. At processing plants in or near large consuming areas the rock is converted into relatively fragile, very bulky products which in most cases are used within a short haul of the processing plant or enter into a manufactured product made at the site of the perlite processing plant.

Jan 1, 1950

Discussion of the paper of C. W. WASHBURNE, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 93,. September, 1914, pp. 2365 to 2378. ROSWELL H. JOHNSON, Pittsburgh, Pa.-It seems to me rather important to bear in mind one thing which is sometimes lost sight of, that the marine sedimentary rocks are laid down in water. We have to start with an initial charge of water. That being so, and the surface tension between the water and the -oil being as slight as it is, as referred to by Mr. Washburne,. the phenomena of capillarity are bound to be most important as between the liquid surface and the gas surface. So far as the liquid-gas surface is concerned, capillarity, in my opinion, is of the utmost importance, and it seems to me this paper of Mr. Washburne's is of great value to us for that reason. Starting out as we have, with our attention concentrated upon gravitational sorting, we have had to wait for the discussion of movement furnished by Munn, and this discussion of capillarity by Washburne, for a more balanced view of the situation. It seems to me that in the accumulation of oil and gas we have a problem of the interworking of gravitational sorting, capillarity, viscosity, immiscibility, and movement. All five things seem to me to be important. I would have expected Mr. Washburne to have given a fuller treatment of the relation of movement to capillarity. In my own experiments I find that gravitation and capillarity alone seem remarkably impotent when everything is at rest, but if I furnish a little movement, gravitation and capillarity step in and accomplish a great many results that one would not expect. Take a horizontal tube and fill a portion at the middle with an ordinary sand saturated with oil, and then put water and sand in each end, and the tube may remain at rest a very long time without that oil distributing itself along the top of the tube. But with a little motion that oil will gradually work up to the upper side. So gravitation and capillarity alone are rather impotent unless they get this element of movement. It would not be necessary to have very extensive movement, but some degree of movement is essential. Now if natural gas, in addition to the method of origin by the action of bacteria on organic matter in mud, may also arise by pressure at great depth, as the overburden is added, a great deal of motion may result. I think more motion is produced in this way than by the descent of meteoric waters.

Jan 4, 1915

By Richard D. Call

In any open pit, some slope instability can be expected, varying from bench sloughing to large-scale slope movement. Major slope displacements are preceded by small, but measurable, displacements and by other indicators of instability, such as tension cracks, rock noise, and changes in groundwater levels. A comprehensive monitoring pro- gram, capable of measuring and assimilating displacement related data, is essential for sound pit operation. The objectives of a pit slope monitoring program are 1) to maintain safe operational procedures for the protection of personnel and equipment; 2) to provide advance notice of instability so that mine plans can be modified to minimize the impact of slope displacement; and 3) to provide geotechnical information for analyzing the slope failure mechanism, for designing appropriate remedial measures, and for conducting future re-design of the slope. Surface displacement measurement using conventional survey equipment and extensometers has been the most widely used method, and it is still the most cost-effective. Tiltmeters and borehole inclinometers are also useful tools, and there are promising developments in micro- seismic monitoring. A monitoring system should have redundancy in both type and number of measurements, and be capable of rapid and effective dissemination of displacement information to those affected.

Jan 1, 1983

By A. B. Parsons

This YEAR BOOK, which is sent to every member, contains the roster of officers and the principal standing committees, brief summaries of the proceedings of the Annual Meeting and of the Regional and Divisional meetings, and the necrology for the year 1934. Also are included abstracts of papers published during the year and a classified list of TECHNICAL PUBLICATIONS and CONTRIBUTIONS, as well as an index of all material published by the Institute in 1934 in TRANSACTIONS, in TECHNICAL PUBLICATIONS and CONTRIBGTIONS and in MINING AND METALLURGY, the monthly magazine, the twelve issues' of which contained 98 technical papers Thus 111 small space are gathered together references to all papers, magazines and books printed by the Institute during the year. The papers for the Iron and Steel and Institute of Metals Divisions have been issued as TECHNICAL PUBLICATIONS distributed under the binding of METALS TECHNOLOGY in the months of January, February, April, June, August, September, October, December This plan of distribution will be continued in 1935 for these two groups The publications for the year 1934 include two sponsored by the Institute's special funds. A Manual for Student Associates and Affiliated Student Societies, prepared by the Committee on Student Relations, of which Jay A. Carpenter was Chairman, was published through the courtesy of the Seeley W. Mudd Memorial Fund, and Volume 112 of the TRANSACTIONS, on Milling Methods, assembled by the Committee on Milling Methods, of which Charles E. Locke was Chairman, was financed by the Rocky Mountain Fund The remaining volumes were all TRANSACTIONS, Volumes 107, Petroleum Development and Technology; 108, Coal Division; 109, Metal Mining and Nonmetallic Minerals; 110, Geophysical Prospecting; 111, Institute of Metals Division and 113, Iron and Steel Division

Jan 1, 1935

E. R. Rice, Wickenburg, Ariz. (communication to the Secretary*):—While this paper is primarily intended as a discussion of Mr. Riter's, I think it will be best to indicate my criticism by describing my own field-methods. It has been my experience that, for ordinary work, the regular transit-book is to be preferred to the card-system for recording notes. This is specially true when computations in the field are required, for it is then necessary to have at hand the total latitudes, departures, ancl elevations. Moreover, the transit-book is easier to carry and manipulate in wet or cramped places, and is not as liable to damage as the loose leaf or card. I use a regular transit-book in the field, and then copy my notes, sketches, etc., in an o5ce-book, entering also the latitudes, departures, and other reductions. These values are then copied into the field-book, securing a duplicate record, in case either book should be lost or mislaid. In the field-book, the notes are entered on the left-hand, and the sketches and remarks on the right-hand page. The next two pages are left blank for the latitudes, departures, bearings, reduced distances, etc. Of course, the notes for the different parts of the mine are entered in the field-book in the order in which they are surveyed; but in the they are entered systematically. It has been my experience that the system of keeping notes used by a surveyor, is particularly adapted to the needs and temperament of the individual. Otherwise, he would not be

Jan 1, 1912

By G. H. Pardue, L. H. Gollwitzer, J. H. Moran, R. L. Morris

Experimental and theoretical studies of casing-borne signals have provided data on the attenuation efect, compressive strength and shear modulus for different types of cement. These data resulted in the establishment of a definite relationship between the cement compressive strength and the Cement Bond log reading. The relationship is influenced by the casing dimensions, but is independent of the type of cement and the curing conditions. The theoretical analysis provides a mathematical statement of the phenomenon and shows that the attenuation rate is basically a function of the shear modulus of the cement and the thickness of the casing. The lab tests provided a connection between the shear modulus and the compressive strength, and permitted a comparison of the experimental and theoretical work. The results of the experimental and theoretical study have provided means of quantitative interpretation of the Cement Bond log. This interpretation is made more convenient with the use of a nomograph. INTRODUCTION Past interpretation of Cement Bond logs has been essenlially based upon a qualitative comparison between the log response in the zone of interest and the responses in the "fully cemented" and the "uncemented" intervals. Most of the variables influencing the magnitude of the signals were recognized in an earlier paper'; however, insufficient laboratory data were available at that time for quantitative evaluation of these variables. Early attempts to use the numerical amplitudes of the signals without full knowledge of their significance resulted in erroneous comparisons between various types of cement. An extensive program was undertaken to evaluate, both experimentally and theoretically, the attenuation phenomenon and to study the effects of the more common variables. A major objective of the experimental program was to obtain data on the relationship between cement-bond-tool response and physical property standards used by the industry so that practical interpretation methods could be devised. The studies included a comparison of attenuation rate with these properties as a function of time, temperature and pressure, using common sizes of casing. The main result was that a definite relationship was established between the compressive strength of the cement in inti- mate contact with the casing and the response of the cement bond tool. For a given casing thickness, regardless of the type of cement or the curing conditions used, the attenuation rate is a function of the compressive strength. A theoretical analysis showed that the attenuation rate for casing-borne signals should be a function of (among other things) the shear modulus of the cement and the thickness of the casing. The relationship between the compressive strength and shear modulus for curing times similar to those encountered in the field was determined from laboratory tests. Using this relationship, the computed attenuation rates showed reasonable agreement with the measured attenuation rates. The purpose of this paper is to report the results of the experimental and theoretical investigations and to present the first practical method for a quantitative interpretation of Cement Bond logs based on known variables. This method is applicable where the casing-borne signal is not affected by high-velocity formation arrivals. DESCRIPTION OF LOGGING TOOL The Cement Bond logging tool shown schematically in Fig. 1 has been described previously.' The tool consists of two sections: acoustic and electronic. The acoustic section contains a transmitter and a receiver, usually spaced 3-ft apart. Sonic energy emittted by the transmitter travels through the casing and is detected at the receiver. The electronic section measures the amplitude of the

By HENRY JULLUM

THE ARGONAUT' mill stands at the crest and spreads down the western slope' of a hill, which incidentally covers the' outcrop of the Argonaut vein' at this point. The collar of the main shaft of the mine is situated on the eastern slope of the same hill 120 ft. below the highest ?point. The present mill, built in 1916, was designed to treat 250 tons per 24-hr. day. This capacity has not been attained recently owing to the inability of the mine to produce enough ore while extensive development and underground construction were under way. At present, however, the mine is more than able to take care of the mill requirements.

Jan 1, 1932

By J. P. Neumann, Y. A. Chang

Lattice parameter measurements of the hcp phase in the system Ag-A1 near the stoichiometric composition Ag2Al were carried out for specimens quenched from 825°K, annealed for 10 days at 453°K, and annealed for 100 days at 413°K. The three heat treatments resulted in the same lattice parameters at room temperature. None of the specimens showed any superlattice lines. The lattice parameters of this alloy were also measured at temperature from 77° to 750°K. An anomaly in the temperature variation of the lattice paramete.rs occurs in the region near 400°k, which may be associated with local ordering. FROM measurements of the diffuse scattering of X-rays, it is known that the [ phase in the system Ag-A1 near the stoichiometric composition Ag2A1 ex- hibits a considerable degree of short-range order at room temperature.' Moreover, based on the position of the short-range order peaks a superlattice model had been proposed in the same study and it was suggested that lowering the annealing temperature to 420°K might result in long-range order. In the present study, the diffraction patterns and the lattice parameters of three differently heat-treated specimens, i.e., quenched from 825°K, annealed for 10 days at 453°K, and annealed for 100 days at 413°K, were determined from 77" to 750°K. The purpose of these measurements was to investigate 1) whether long-range order could be established by prolonged annealing and 2) whether the lattice parameters at room temperature depended on the heat treatment, since it had been proposed earlier2 that the lattice parameters in this phase are related to the atomic arrangement. 1) EXPERIMENTAL TECHNIQUES Silver and aluminum, both 99.99 pct purity, were melted in a zirconium oxide crucible under helium in

Jan 1, 1969

By L. A. Morley, W. T. Parry

Engineering design problems encountered by mining engineers often depend on the properties of natural granular materials such as soil, poorly consolidated sediment, fault gouge, and hydrothermally produced clay. The physical properties of such granular materials frequently are determined by the properties of silicate clays. In most mining applications, the clays are in contact with water. Swelling of clay due to water infiltration can interfere with underground support and haulage systems. Water-saturated clay on fault, fracture, and bedding planes causes slope failures in open pit mines, roof falls and heaving of weak underclays in coal mines. Water may be removed and cementing agents may be produced in clays by electrical methods. When an electrical potential gradient is applied to a charged capillary by two electrodes, water moves toward the negative electrode.1 This electrokinetic phenomena is known as electroosmosis and has been used to successfully dewater clay minerals which lack strength because of water. A consolidation effect occurs when the flow of water is accompanied by a decrease in water content. Electrochemical changes in the clay result in cementing and irreversible hardening. Theory A mathematical basis of electroosmotic phenomena is presented by Helmholtz.3 Smoluchowski5 modifies Helmholtz’ model and presents Eq. 1 to describe fluid flow velocity due to electroosmosis. For this formula, the zeta potential can be measured experimentally. The Helmholtz-Smoluchowski model is reasonably valid for clay aggregates with large pores saturated with fresh water or dilute electrolyte solutions.° An assumption used for Eq. 1 (equations are given Table 1; terms are defined in Table 2) is that the thickness of the electrical double layer surrounding the clay particles is small compared with the pore radii. Because this is generally not the case, Schmid7 presents Eq. 2. The volume charge density in the pore may be approximated from cation exchange capacity and porosity measurements. Casagrande8 offers a semi-empirical relationship (Eq. 3) for volume rate of electroosmotic flow and finds that k, is relatively constant for most clays with an average

Jan 1, 1972

By Peter G. Groer

Several methods1-3 are being used to determine the WL and individual Rn-daughter concentrations in uranium mine atmospheres. The best of these methods is the one given in Ref. 3. According to this method, the WL and the Rn-daughter concentrations are determined from the total a-counts observed during three consecutive time intervals. Its only disadvantage lies in the fact that rather involved calculations are necessary to convert the observed counts into WL or pCi/l (picocuries per liter). There are, however, counting intervals that give simple weighting coefficients for the observed counts. This fact makes it possible to convert from a-counts to WL or pCi/l with the aid of a graph. After some trial runs on a computer the following equations emerged as the basis for the most practical procedure: [ ] NA, N.., and & stand for the number of RaA, RaB, and RaC atoms per liter of air. C(t1,t2) denotes the counts observed from time t. to time t2 (in minutes) after the end of the 5-min sampling period. E is the detector efficiency and V is the flow rate in liters per minute. With an accuracy loss of less than -5% one finds from [Eq. 1] by adding the corresponding terms: If the WL would have been calculated according to [Eq. 2] instead of using the graph, the result would have been 0.31. Since the values used for C's under [Eq. 3] represent the exact number of counts from a Rn-daughter mixture in equilibrium with 100/3 pCi of Rn the exact WL of this mixture can be calculated easily. The exact value is: [ ] This shows that the method is quite accurate for the 0.3 WL domain. The precision of the method excluding errors made in reading the graph can be estimated with the help of the following formula: [ ]

Jan 1, 1974

By Galen Clevenger

TELLURIUM has had the rare and unpleasant distinction of having fewer uses than any of the other common elements; indeed, it has had no regular or important uses. It is not only a useless and disagreeable element, but to the metallurgist it has been a nightmare. The interference of tellurium with the recovery of gold and silver from certain ores, as well as the difficulties it occasions in the electrolytic refining of copper, lead, and silver, are too well known to require enumeration here. In fact, the potential producers of the element have been quite willing to throw the crude products from which it might be recovered into the sewer. First isolated from a gold ore in 1782, although remaining a practically unknown element to the general public, it has long been a guiding star to the Western prospector in his quest for the "golden fleece." On the burning sands of the desert, in the frigid North, and in the mountain fastnesses of the more temperate regions of this and other continents, he has endured all manner of hardships in his search for tellurides; for where he found indications of tellurium, there he expected also to find rich deposits of gold and silver. This peculiar superstition, that tellurium, associates itself in nature with the precious metals, is not with-out reason, for witness the fabulously rich gold tellu-ride deposits of Cripple Creek and Western Australia. Selenium, the sister element of tellurium, which it resembles in many of its properties, was first isolated in 1817. It is found in small amounts in certain native sulfur deposits, and in many copper and silver ores from all parts of the world. Until a few years ago, selenium, like tellurium, was practically useless. The, unusual property of having its electrical conductivity influenced by light has long been known. Selenium cells, which for many years have been a scientific curios-ity, in the future may come to be of more commercial importance, but this use could scarcely absorb any large amount of the element.

Jan 1, 1923

By Raymond E. Zimmerman

Abstract-The Swirl Cyclone developed in Japan, although based upon the same principles as the standard cyclones for heavy-media or water-only cyclones for cleaning coal, is novel in that it is invested with the apex on top, discharging rejects at the top, and clean coal at the bottom. It also uses a variable air vent tube for controlling the vortex. Tests conducted indicate that its efficiency is not only as sharp as standard cyclones but it also performs using a much coarser grain magnetite, promising higher magnetite recovery. The author describes the results of tests conducted in Japan on a very difficult coal.

Jan 2, 1978

By J. W. Rutter, K. T. Aust

Competitive growth of recrystallized grains into striated single crystals of zone-refined lead produced preferred orientations of the coincidence type after annealing at 175°C, but not at 300°C. This preferred orientation development was found to result from the higher mobility and lower energy of large -angle coincidence boundaries compared to large-angle noncoincidence boundaries. These mobility and energy difference provide a useful basis for explaining many cases of preferred orientation observed in annealed metals. DURING a study1 of the mobility of grain boundaries in zone refined lead, it was observed that the temperature dependence of the grain boundary migration rate is smaller for large-angle, coincidence-type grain boundaries than for large-angle noncoincidence ("random") boundaries. This observation is illustrated schematically in Fig. 1, which shows log rate of grain boundary migration vs reciprocal absolute temperature for two large-angle boundaries. The upper curve refers to a coincidence-type boundary of the sort discussed by Kronberg and Wilson.2 While the mobilities of these two boundaries are similar at 300°C, the coincidence-type boundary has a greater mobility, by a factor of about: four, at 175°C than does the noncoincidence boundary illustrated in the lower curve. The observation described above suggested a simple experiment for testing the role of grain boundary mobility in the development of preferred orientation in annealed, high-purity lead. On the basis of this observation, it would be expected that if a large number of grains of different orientations are growing competitively, and if relative grain boundary mobility is a controlling factor, then the specimen procluced by boundary migration will contain crystals having random orientations if annealing is done at 300°C, while preferred orientations of

Jan 1, 1962

By Charles O. Thompson

IN 1867 the city of Worcester walled in the Mill Brook for its main sewer. This stream, one of the important affluents of the Blackstone River, flows through the city in a southwesterly course from Salisbury Pond, and along its valley a considerable part of the heavy manufactories of the city are placed. At two points, a mile apart, a sufficient fall occurs to be turned to account for motive power, and at many points it was the right and practice of the riparian proprietors, prior to 1867, to use the water for steam and other manufacturing purposes. But the

Jan 1, 1881

By E. H. Griswold

The surveying of oil wells has in recent months become a common practice in the deep fields of the Mid-Continent area. Borehole surveys have been made by mining companies for many years, but the introduction of such methods into the oil fields has been delayed until the past few years, because the value of survey data was not fully appreciated. The acid and gelatin bottle methods of obtaining the angle of deviation and the floating compass method of obtaining the direction of horizontal drift have been in use for more than 20 years. A photographic recording instrument consisting of a plumb bob, magnetic needle and electrically operated camera was devised and used in the Rand mining fields of South Africa prior to 1912.1 Another and improved photographic instrument, depending upon orientation of the drill pipe instead of polar magnetism for direction, has been invented and used. The acid bottle method has also been used in conjunction with oriented drill pipe. The magnetic compass is not reliable for oil-well work because of the unsymmetrical attraction of the needle to the well casing and possible magnetic formations. Many engineers also concur in the opinion that orientation of the drill pipe from instrument to surface will be inaccurate because of the torque exerted between the drill pipe and walls of the hole, causing the lower sections of pipe to twist. When it is considered that 4000 ft. of 6 in. drill pipe has approximately the same slender-ness ratio as 6 ft. of silk thread, such twisting effects can be readily visualized. The gyroscopic compass has been suggested for use in direction finding, but the high cost of such instruments will prohibit their use, except in special cases. Due to the lack of accurate direction-finding instruments, almost all of the survey work in the Mid-Continent fields has been of the acid bottle method alone.

Jan 1, 1929