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Executive A R LEDOUX, Chairman ARTHUR S DWIGHT CHARLES F RAND E P MATHEWSON J V W REYNDERS Membership E DEGOLYER, Chairman W Y WESTERVELT, Vice-chairman WILLIAM H BASSETT H G MOULTON C MINOT WELD Finance WALTER H ALDRIDGE, Chairman GEORGE D BARRON GALEN H CLEVENGER Library GEORGE C STONE,' Chairman JOHN H JANEWAY ALEXANDER C HUMPHREYS, ROBERT LINTON FREDERICK F SHARPLESS

Jan 1, 1923

By R. E. Head

Under existing economic conditions, the treatment of gold ores occupies an outstanding position in metallurgical activity. The increased price of gold has automatically brought about a reclassification of old dumps and low-grade orebodies, and many that formerly were considered valueless are now being vigorously investigated and worked. This situation has developed problems that have taxed the ingenuity and ability of metallurgists to the utmost. Some gold ores give a high extraction of gold by standardized methods of treatment; other ores of apparently similar character yield but a relatively small percentage of their gold when treated by the same processes. Surface Contamination The experience gained by microscopic study of numerous gold ores and tailings has shown that there are pronounced differences in the physical characteristics of the minerals composing them, more especially of the gold. Repeated studies of tailings from flotation and cyanidation of gold ores has established the fact that surface contaminations on gold particles are often directly responsible for high gold losses; comparison of gold particles isolated from flotation concentrates and the resulting tailings have showed that the clean gold has been recovered and the tarnished or contaminated gold invariably lost in the tailing. Obviously, it is not possible to make such a comparison of gold ores treated by cyanidation, as the clean gold has been taken into solution; but when the gold found in cyanide tailing has a tarnished or coated surface, one may infer, with a reasonable degree of certainty, that the clean gold has been extracted. This premise is supported by experimental evidence obtained by isolating particles of tarnished gold and exposing them to cyanide solution in small parting cups. In one such experiment, tarnished gold particles picked from a cyanide tailing showed but slight evidence 01 dissolving at the end of 27 days. In this test, a cyanide solution of 1.6 11). per ton was used and the leach solution was decanted arid renewed every

Jan 1, 1939

By R. E. Head

Under existing economic conditions, the treatment of gold ores occupies an outstanding position in metallurgical activity. The increased price of gold has automatically brought about a reclassification of old dumps and low-grade orebodies, and many that formerly were considered valueless are now being vigorously investigated and worked. This situation has developed problems that have taxed the ingenuity and ability of metallurgists to the utmost. Some gold ores give a high extraction of gold by standardized methods of treatment; other ores of apparently similar character yield but a relatively small percentage of their gold when treated by the same processes. Surface Contamination The experience gained by microscopic study of numerous gold ores and tailings has shown that there are pronounced differences in the physical characteristics of the minerals composing them, more especially of the gold. Repeated studies of tailings from flotation and cyanidation of gold ores has established the fact that surface contaminations on gold particles are often directly responsible for high gold losses; comparison of gold particles isolated from flotation concentrates and the resulting tailings have showed that the clean gold has been recovered and the tarnished or contaminated gold invariably lost in the tailing. Obviously, it is not possible to make such a comparison of gold ores treated by cyanidation, as the clean gold has been taken into solution; but when the gold found in cyanide tailing has a tarnished or coated surface, one may infer, with a reasonable degree of certainty, that the clean gold has been extracted. This premise is supported by experimental evidence obtained by isolating particles of tarnished gold and exposing them to cyanide solution in small parting cups. In one such experiment, tarnished gold particles picked from a cyanide tailing showed but slight evidence 01 dissolving at the end of 27 days. In this test, a cyanide solution of 1.6 11). per ton was used and the leach solution was decanted arid renewed every

Jan 1, 1939

By F. E. Werner, B. L. Averbach, Morris Cohen

THAT bainite formed near the M, temperature bears a striking r esemblance to martensite tempered at the same temperature has been shown by the electron microscope.' By means of electron diffraction,' it has been established that carbide and cementite are present in bainite formed at 500°F (260°C); these carbides are also found in martensite tempered at 500°F (260°C).' The investigation reported here is concerned with an X-ray study of the matrix phases in lower bainite and tempered martensite. These phases have turned out to be dissimilar in structure; the matrix of bainite is body-centered-cubic while that of tempered martensite is body-centered-tetragonal. A vacuum-melted Fe-C alloy containing 1.43 pct C was studied. Specimens of 16 in. diam were sealed in evacuated silica tubing and austenitized at 2300°F (1260°C) for 24 hr. One specimen was quenched into a salt bath at 410°+7 °F (210°+4°C), held for 16 hr, and cooled to room temperature. The structure consisted of about 90 to 95 pct bainite, the re: mainder being martensite and retained austenite. A second specimen was quenched from the austen-itizing temperature into iced brine and then into liquid nitrogen. It consisted of about 90 pct martensite and 10 pct retained austenite. The latter specimen was tempered for 10 hr at 410°+2°F (210°+1°C). The specimens were then fractured along prior austenite grain boundaries (grain size about 2 mm diam) by light tapping with a hammer. Single aus-tenite grains, mostly transformed, were etched to about 0.5 mm diam and mounted in a Unicam single crystal goniometer, which allowed both rotation and oscillation of the sample. Lattice parameters were measured by the technique of Kurdjumov and Lyssak. This method takes advantage of the fact that martensite and lower bainite are related to austenite by the Kurdjumov-sachs orientation relationships Thus, the (002) and the (200) (020) reflections can be recorded separately, permitting the c and a parameters to be determined without interference from overlapping reflections. According to these findings, the matrix phase in bainite is body-centered-cubic and, within experimental error, has the same lattice parameter as ferrite (2.866A). On the other hand, martensite, tempered as above, retains some tetragonality, with a c/a ratio of 1.005t0.002. Most workers in the past have assumed that bainite is generated from austenite as a supersaturated phase, but the nature of this product has not been established. The question arises as to whether bainite initially has a tetragonal structure and then tempers to cubic, or if it forms directly as a cubic structure. If it forms with a tetragonal lattice, it might well be expected to temper to the cubic phase at about the same rate as tetragonal martensite. The martensitic specimen used here was given approximately the same tempering exposure, 10 hr at 410°F, as suffered by the greater part of the bainite during the isothermal transformation. About 50 pct bainite was formed in 6 hr at 410°F. On tempering at this temperature, martensite reduces its tetragonality within a few minutes to a value corresponding to 0.30 pct C.' Further decomposition proceeds slowly, and after 10 hr the c/a ratio is still appreciable, i.e., 1.005. Thus, even if the bainite were to form as a tetragonal phase with a tetragonality corresponding to only 0.30 pct C, which might be assumed to coexist with e carbide, it would not be expected to become cubic in this time. It seems very likely, therefore, that bainite forms irom austenite as a body-centered-cubic phase and does not pass through a tetragonal transition. The carbon content of the cubic phase has not been determined, but it could easily be as high as 0.1 pct, within the experimental uncertainty of the lattice-parameter measurements. It has been postulated that retained austenite decomposes on tempering into the same product as martensite tempered at the same temperature. There is now considerable doubt on this point. The isothermal transformation product of both primary and retained austenite at the temperature in question here is bainite," and the present findings show that bainite and tempered martensite do not have the same matrix. Acknowledgments The authors would like to acknowledge the financial support of the Instrumentation Laboratory, Massachusetts Institute of Technology, and the United States Air Force.

Jan 1, 1957

By Barry N. Whittaker

INTRODUCTION Considerable progress has been achieved with long- wall mining in recent years especially in enabling increased rates and levels of output to be gained, higher standards of safety and increased usage of advanced technological developments. Longwall mining also has major long term advantages, prominent amongst which is general minimisation of the effects of pillars and room intersections giving rise to future instability problems as can be the case with room and pillar mining operations. The fact that longwall mining is not presently limited by depth below surface inclination of seams or thickness of seam to be worked strengthens its position as the most popular underground mining method for extracting coal seams in Europe. Its wider application in North America and Australia can give rise to significant economic benefits coupled with higher levels of safety and recovery of coal. This present paper reviews recent progress achieved and draws attention to the more important factors influencing longwall mine design and layout. LONGWALL STRATA PRESSURE ABUTMENTS A longwall gives rise to major redistribution of strata pressures. The roof behind a longwall is normally allowed to cave and permit subsidence of the overlying strata and eventually giving rise to a trough depression at the surface. Consequently, reestablishment of strata loading within the caved region behind the longwall depends upon effective caving and subsequent recompaction. This requires sufficient depth pressure and/or adequate width of extraction in relation to the depth to achieve breaking of overlying roof beds necessary to reload the extracted region. Figure 1 shows results of an analysis carried out by Whittaker and Singh (1979) indicating the pattern of redistribution of vertical stress around a longwall in the plane of the seam. The analysis represents the average depth of longwall working in the UK, and was performed using a stress balance assumption of compatibility before and after mining. The main stress abutments are indicated by (1) the front abutment strata pressure zone which travels with the longwall, and (2) the flank abutment strata pressure zone which

Jan 1, 1982

By Donald H. McLaughlin, John H. Moses

IN the latitude of Lima, the broad uplifted block that forms the Andes is made up of a complex sequence of folded and faulted sediments and volcanics, broken by large and small bodies of granitic rocks and porphyries with which the principal mineral deposits are closely associated in both time and space. The intrusives are a final episode in the geologic history as revealed by the consolidated rocks, for after their emplacement and after the formation of the primary ore deposits in and about them the record is simply one of long continued erosion and uplift.

Jan 1, 1945

By G. R. Mansfield, W. B. Lang

THE third year of Government exploration for potash by the U. S. Geological Survey and the U. S. Bureau of Mines under the authorization of the act approved June 25, 1926 (Public 424-69th Cong.) is drawing to a close. The results thus far obtained are thought to be sufficiently interesting and satisfactory to justify the presentation of a brief preliminary account of the work. Review of Earlier Exploration The general geologic similarity of the Permian basin of Texas and New Mexico to the potash field of Germany had long ago suggested the possibility of the presence of potash salts somewhere in that basin, but petroleum exploration was then making little headway there and the necessary data could not be obtained. The discovery by Udden in 1912 of potash in brine from the Spur well in Dickens County, Texas, was the first direct evidence of its presence. In 1915-17 the U. S. Geological Survey drilled a test well with standard tools at Cliffside near Amarillo, but failed to find potash. Nevertheless, an observer has been kept in the field, at first in cooperation with the Texas Bureau of Economic Geology but since 1922 by the Survey alone, to secure data and samples from oil and gas tests. Since the discovery of oil in Reagan County in 1923 exploration by drilling has been rapidly extended to many parts of western Texas and southeastern New Mexico. The identification of the potash-bearing mineral polyhalite was first announced by the Geological Survey in June, 1921, the material having come from cuttings from the Bryant well in Midland County and the Burns well in Dawson County, Texas. Successive discoveries and announcements of similar purport aroused widespread interest in potash exploration, which culminated in the action by Congress already noted. Permian Salt Basin The Permian salt basin extends generally northeastward from western Texas and southeastern New Mexico through the Panhandle sections of

Jan 1, 1929

By C. Laird, C. E. Feltner

May different kinds of dislocation structures have been observed in strain-cycled metals and alloys. In order to understand their pattern and causes, an experimental program has been carried out to determine the influence on the dislocation structures of the three variables: 1) slip character of the material, 2) test temperature, and 3) strain amplitude. The results show that at high strain amplitudes cell structures me formed when the slip character is wavy, and that these are progressively replaced by uniform distributions of dislocations as the stacking fault energy is decreased. At lower strains, dislocation debris is formed which consists primarily of dipoles in wavy slip mode materials and multipoles in planar slip mode materials. Temperature merely acts to change the scale of the structure, smaller cells, and clumps of dislocation debris being associated with lower temperatures. It is shown that the results for many metals fit this pattern, which Parallels that occurring in unidirectional deformation. DISLOCATION structures produced by cyclic strain (fatigue) have been examined in a number of metals by transmission electron microscopy. These studies have produced a variety of interesting and often seemingly conflicting results. For example, different investigators have reported such structural features as cells.le4 bands of tangled dislocations,4'5 dense patches or clusters of prismatic dislocation loops, planar arrays,4'10 and various combinations or mixtures of these different structures. Most of these observations have been made on materials which were initially annealed and cyclically strained at low amplitudes resulting in long lives. Recently we have reported observations of the dislocation structures produced in copper and Cu-7.5 pct Al cycled at large amplitudes, resulting in lives of less than 104 cycles.4 These results, examined in combination with those in the literature, have suggested that a common or consistent structural pattern exists. Variations in this pattern appear to be determined chiefly by the three variables, namely, the slip character of the material,4,11 test temperature. and the strain amplitude. To verify this interpretation, we have studied [he influence of the above three variables (in different combinations) on the resultant structures in cyclically strained metals. Copper, fatigued at room temperature, was chosen as a reference state to which all other observations can be compared. The effect of slip character has been investigated by employing fcc metals of different stacking fault energy. Thus aluminum which has a more wavy slip character than copper, and Cu-2.5 pct A1 having a more planar slip char- acter, have been examined. The aluminum samples were fatigued at 210°K thus making their homologous temperature equal to that of copper at room temperature. The influence of temperature has been evaluated by examining the structures in copper at room temperature and 78°K. Finally the effect of strain amplitude was studied by looking at the structures at amplitudes giving lives ranging from 104 to 107 cycles. All of the specimens were examined at the 50 pct life level at which stage the structures have reached a stable configuration.12 I) EXPERIMENTAL PROCEDURE Strip specimens, 0.006 in. in thickness, were prepared from base elements of 99.99 pct purity or greater. Specimens were fatigued by cementing the strips to a lucite substrate which was subjected to reverse plane bending. This method of testing has been described e1sewhere.7 After fatiguing, specimens were thinned and examined in a Philips EM 200 which was equipped with a goniometer stage capable of ±30-deg tilt and 330-deg rotation of the specimen. On the basis of separate calibrations,13 allowances were made for the relative rotation and inversions between the bright-field images and the diffraction patterns. II) RESULTS AND DISCUSSION The life behavior of the materials under different test conditions is shown in Fig. 1 in the form of plots of total strain range vs cycles to failure. Comparisons of structures produced in the different materials were made at amplitudes which produced equal numbers of cycles to failure. The influence of strain amplitude on the structures produced in the reference state material (copper tested at room temperature) is shown in Fig. 2. At the 104 life level the structure produced comprises cells similar to those previously observed.3,4 They are approximately 0.5 p in diam and the cell walls are generally more regular or sharper than those produced by unidirectional deformation.14 At the 10' life level the

Jan 1, 1969

By F. Weinberg

It has been suggested, for some time, that the behavior of metals under high-temperature creep conditions is strongly influenced by the behavior of the grain boundaries present in the material. This has led to a number of investigations1-6 in which attempts were made to measure the properties of the grain boundaries themselves, both to determine their contribution to the creep process and to obtain further knowledge of their intrinsic structure and properties. The present investigation was undertaken to extend the observed data under more closely controlled experimental conditions and to attempt to clarify sonie of the discrepancies in the literature. A brief report of the preliminary results has been published.7 EXPERIMENTAL PROCEDURE For the present investigation, controlled orientation specimens were used having plane boundaries which terminated at the specimen surface. Trierys-tal specimens were used instead of the bicrystal type of Puttick and King,' in order to simplify the gripping technique required to apply a shear stress along the boundary. The aluminum used was obtained from the Aluminum Francaise and was of 99.994 pct purity, containing 0.002 pct each of Cu, Fe, and Si. The aluminum tricrystals were grown horizontally from the melt, in graphite boats, and in an argon atmosphere, following the technique developed by Chalmers.' The orientation of the tricrystals was controlled by using seed crystals separated by mica inserts. Thermal conditions were adjusted to produce tricrystals having boundaries which were macroscopically straight, parallel to the growth direction, and perpendicular to the top surface. Following growth, the tricrystals were carefully cut with a jeweller's saw to the test specimen shapes shown in Fig. l(a) and l(b). In Fig. 1(a), the boundaries subjected to shear stresses are indicated AB and CD: Points A and C are the ends of the mica inserts separating the seed crystals; points B and D are at lateral cuts made in the specimen. It was found that the slots left by the mica inserts at A and C had to be enlarged slightly, by cutting, to ensure that the boundary terminated freely at these points. A shear stress was applied to the boundarks by gripping the upper two legs in file-faced Inconel grips and suspending a weight from the lower part of the specimen held in similar grips, as shown schematically in the diagram. The test specimens shown in Fig. 1(b) were cut from long

Jan 1, 1959

"The mines of Butte, in addition to the square timber used, consume each year large quantities of round timber, which are called stulls. The Stull business is an important industry, as will be seen from a brief description of the operations of the Mines Timber Co., which institution furnishes most of the stulls and lagging poles used in the Butte mines.Timber produced by the Mines' Timber Co. is mostly cut on the government forest reserve, on California gulch, American gulch and French gulch. To bring the timber to market, a flume 16 miles long has been constructed from Big American gulch to Mill creek. The flume, which heads on Big American gulch, on the Atlantic slope, crosses the Continental Divide at an elevation of 6,525 ft., and delivers timber at Mill creek on the Butte, Anaconda & Pacific railway, which is on the Pacific slope. Timber is loaded on cars at Mill creek and shipped to the Butte mines, a distance of twenty-six miles. There are 29 trestles on the flume line over 25 ft. high. The highest trestle is 78 ft. and the longest is 775 ft. The longest tunnel on the line of the flume is 565 ft. from portal to portal."

Jan 1, 1913

By AIME AIME

To accompanying photograph of the plant of the Beattie Gold Miner Limited, at Duparquet,. Quebec, is taken from the east and shows the open-pit from which the ore is taken during the summer. The buildings on the level ground above the open-pit are the change rooms, steel shop hoist building, compressor building, machine shop, warehouse, carpenter shop, and oil house. The main five-compartment shaft is shown west of the hoist building. The crusher plant adjoins the headframe and a long conveyor transports the fine ore

Jan 1, 1936

By S. H. Ash

More than 100 minerals are mined and processed in the U. S. Management and labor have negotiated wage-scale agreements that have balanced wages and affected cost of labor in such a manner that comparisons can be made of transportation costs. Transportation of materials underground has become of vital importance. This report describes underground haulage methods and equipment, presents cost analyses, and discusses future plans for underground transportation in metal mines. It does not cover hoisting in shafts or slopes by cage, skip, or cars. Advancements have been made by the metal mining industry in lowering transportation costs in several mines, making it possible to mine orebodies or portions of orebodies not considered economically recoverable a few years ago. Numerous reports have been written on transportation at metal mines; this report covers recent haulage at some representative mines throughout the U.S. The term metal mine is used to include all noncoal mines from which up-to-date information was obtainable.

Sep 1, 1956

By J. Burns Read

IT IS the purpose of this paper to summarize, as far as possible, the metallurgical information and experience gained by the Ordnance Department, during the War, in the manufacture of artillery cartridge cases, to describe the tests to which artillery cartridge cases were put, and to summarize the knowledge and experience gained in this testing. The authors wish to acknowledge the aid given by manufacturers, army officers, and civilian employees of the Ordnance Department in obtaining these data. Artillery cartridge cases are cold drawn from circular disks punched from strips of rolled brass. The manufacture involves from 25 to 30 main operations, which are done almost entirely on a punch press. Descriptions of the operations have appeared in various periodicals and, therefore, will not be given here. After each cupping, or drawing, operation, except the last, the cases are annealed at from 540° to 650° C. (1000° to 1200°F.), to remove all the hardening stresses set up in the metal and to allow complete recrystallization. After each annealing, the cases are pickled in niter cake or sulfuric-acid solution and then washed in water to remove all traces of acid. In some instances, the cases are then immersed in a cyanide-salt solution, and afterwards rinsed in water, to remove the thin layer of copper that forms on the surface of the cases during the acid pickle. The last cold-drawing operation is followed, by the heading operation which, by flattening the head of the case on the outside, causes the metal to flow on the inside to approximately the proper finished dimensions. The mouth, or open end, is then annealed at 430° to 480° C. (800° to 900° F.) by immersion in a salt bath or by gas flames. After being washed, the cases are tapered, when they are ready for machining, inspection, and testing.

Jan 4, 1922

Jan 1, 1933

By Benjamin Tillson

The hammer drill rightly receives the credit for having made the one-man drill possible, and so many economies seem possible through the proper application of :different types of hammer drills to various mining, quarrying, and, excavating operations, that an indication of the economies effected by the New Jersey Zinc Co. at its Franklin mines may be of pertinent interest. When this company commenced its trials of hammer drills in 1907, these tools had not I been developed to one-fourth the capacity and refinement which they have at present. At that time it was frequently stated that such a small tool, drilling holes of less diameter than the reciprocating rock drill, could not drill enough holes in a shift to permit the placing of sufficient explosive to break a tonnage of ore comparable with that produced by the"' rock drills;" that the placing of small holes inclined upward, at angles steeper than 40° above the horizontal, could not be expected to produce results equal to the large flat, wet or dry, holes in the breasted back of an overhand stope, and would only shatter the ground so as to make the back unsafe. In' spite of these adverse opinions, the hammer drills first showed their superiority over both heavy and light reciprocating drills in raising and in stoping, and then in drifting and quarry work. As a result, all of the reciprocating drills at the Franklin mines were scrapped, three years ago, all of the mining work being accomplished with increased efficiency, as shown in detail in this article. With the advent of the hammer drill in this property, it was considered advisable to make comparative tests of all the tools accessible, and it has since been the policy to investigate the merits of any advance of the drilling art in order to get the maximum amount of work from the tools. The necessity of devising some means of standardizing drill tests, and of measuring the consumption of compressed air as well as the drilling speed, was early realized.

Jan 2, 1915

Jan 1, 1934

By Bedrand L. Johnson

THE phosphate-rock industry is built upon natural deposits of rocks and minerals in which the element phosphorus is present as a phoshate. The term ?phosphate rock? is a general one, applied to certain rocks of different degrees of consolidation and of diverese origin, charater and occurrence, composed of intimate mixtures of several phosphate minerals, largely submicrocrystalline, usually calcium phosphates, in commerical quantities, with various impurities. This term includes phosphatized limestones, sandstone, shales, and igneous rocks; nodular phosphates ; residual weathered phosphatic limestones ; vein phosphates ; and phosphatic sediments, both consolidated and unconsolidated.

Jan 1, 1944

By W. H. Emmons

MOST mineral deposits change as they are followed downward on their dips. Some of these changes are due to primary arrangement; different ores were precipitated at different depths when the deposits were formed. Other changes are due to weathering or secondary enrichment. The chief changes resulting from weathering, in the main, are understood and standard changes are recognized. The processes are relatively simple. They take place at ordinary temperatures and pressures and can be duplicated in the laboratories. Moreover, there are thousands of deposits available for study, because the processes take place near the surface where the development of mines is begun. The changes due to primary arrangement of the deposits of the metals are not so well understood. Deposition has taken place at higher temperatures and our knowledge of the chemistry of the processes leaves much to be desired. Very few experimental data are available. The deposits, moreover, offer fewer examples because many mines are not, developed to depths where the changes can be studied and a change to unprofitable material usually results in stopping work. Most, students of ore deposits now accept, as confirmed, the hypothesis that nearly all lodes and related deposits were formed by solutions originating in intrusive igneous masses. Outward from these masses, the deposits at many places are grouped in zones and the arrangement noted from the intrusions outward are commonly the reverse of the changes noted from the surface downward in a single lode. A study of the changes in groups of deposits, from the parent intrusion outward, will throw light on the changes to be expected in a single lode downward. Because the changes in series of deposits from the intrusive outward may all be observed near the surface, where more data are available, it is possible to increase the number of examples many fold and to apply the statistical method of study with greater confidence of avoiding error.

Jan 3, 1924

By AIME AIME

THIS year the Chairman of the Institute's Iron and Steel Division is THIS William Anderson Haven, better known to the membership generally as Bill Haven. The Division Chairman is an individual endowed with a broad perspective of the ferrous metal industry he result of his earlier experiences as a successful operating man in the working and management of blast furnaces and his later experiences as an engineering-consulting executive concerned with the design and erection of and steel works throughout the world. William A. Haven was born to iron steel in the Pittsburgh district on ;. 1, 1888, and in due time--or in 1909 graduated from Penn State with a Bachelor degree in industrial chemistry.

Jan 1, 1944

By E. S. Grumell

The correct sampling of coal and coke is becoming important to an ever increasing number of producers and consumers. This, therefore, may be an opportune moment to examine where we stand with regard to existing and proposed methods. In this paper an attempt will be made to review, as briefly as possible, some of the considerable amount of painstaking research which has been done in the last 10 years, and which has unquestionably led to a much better understanding of the subject. In so doing we shall try, on the one hand, to make clear where substantial progress has been made, and on the other hand, to draw attention to points that require further investigation. The paper is divided into sections in order to emphasize the major divisions of the subject; further, in order to retain this emphasis, detailed consideration of some of the points has been relegated to appendixes. No attempt has been made to give a complete survey of the literature, as this has already been done by L. A. Bushell.2 The following abbreviations will be used: A.E., average error; P.E., probable error; S.W.R., size-weight ratio; B.S.I., British Standards Institution. Section 1.—Cost It has often been stated that the cost of sampling should bear some relationship to the value of the product, and since coal is a relatively cheap raw material it would be a major error to specify, for ordinary commercial purposes, elaborate and costly methods of sampling which nobody would adopt. Specifications must be of such a nature that they will be used. We believe that one of the achievements of the last 10 years has been to reduce the cost of sampling. There is, however, another point to be considered; via., that the cost of sampling should bear some relationship to the value of the investigation. Correct sampling is a cog (possibly a small one) in the wheel

Jan 1, 1940