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By H. Evans, L. A. Hunt

In the pellet-producing industry it is sometimes claimed that "The pellets are made in the concentrator," or that "The key to good pellets is in the balling operation." However, one claim is generally agreed on: If you can put in, on, and through the indurating furnace a good green ball of Proper size and adequate strength to withstand the handling, load, dehydration, and thermal shock until it is properly heat-hardened, you will have the pellet product you desire-that is, a "competent" green ball. The strength requirements that enable a competent green ball to withstand the environment of the indurating furnace are usually less restrictive than those for transporting the green ball from its source of production to the furnace. Experience has shown that different types of material may have different balling characteristics which may impose limitations on the quality of the green ball that can easily be produced under normal conditions. Therefore, if a specific material will produce a green ball that meets the physical requirements for competency in the furnace, but not for handling or transportation, various practices must be instituted to overcome this deficiency. In other words, if a normal handling system is too rigorous for the green balls that can be produced under standard conditions, then "handling with care" should be tried.

Jan 5, 1967

By Joseph A. Norden, A. R. Willson

Much has been written concerning the hoisting equipment of various mines throughout the country, but most of the literature on the subject, if not all, describes equipment of extraordinary capacity and the small and medium-sized outfits have been neglected. The hoisting equipment here described is capable of handling about 1200 tons per day. It has not been worked to capacity, but 600 to 700 tons, together with men and materials, have been handled in two shifts without any great effort. Only one shaft extends from the surface to the lowest levels of the mine; see Fig. I. It is composed of three compartments, two of which are used for hoisting, and the third for water, air, and electrical lines, and for sinking purposes. In 1909, this shaft was raised from the 1000-ft. (304-m.) level to the 700-ft. There a station was cut and an air hoist installed. At this time all mining operations were confined to the upper levels of the mine; that is, above the 700-ft. The ore was dropped to this level through chutes from the 300-, 400-, 500-, and 600-ft. levels and then lowered in cars on cages to the 1000-ft., which is the main haulage adit, the mill and railroad bins being about 3000 ft. from the shaft. Orebodies were, in due time, developed on the 1000-ft. level and below. Therefore, in 1913,the shaft was sunk to the 1150-ft. level and thereafter sinking was continued at regular intervals until the 1500-ft. level was reached. But, hoisting from the 1300-ft. level was a difficult and slow process with the antiquated air hoist, so, in 1916, it was decided to raise the shaft to the surface and install a modern, electrically operated hoist. This was completed early in 1917 and the hoist was in operation in March of that year. The Hoist Figs. 2, 3, and 4 show various features of the hoist and electrical equipment. A Nordberg engine of the double-drum, geared type, designed for a 10-ton load, including rope, at a speed of 1500 ft. per min., is used. The drums are 7 ft. (2.1 m.) in diameter, with a 54-in. (137-em.)

Jan 1, 1922

By W. L., Yerkes

AN interesting study of the application of air-, conditioning to the problem of mine ventilation and cooling can be found on the Witwatersrand in South Africa. Here there are a large number of deep mines in a relatively small area. Due to the nature of the reef, many mines are working at a depth of 6000 ft. and some have gone down to 8000 and 9000 ft. below the surface. At such depths, even in a country geologically as old as Africa, the virgin rock temperature approaches 110°F. The flow of heat from the- rock to the ventilation air is tremendous though the shaft or drift may have been open to ventilation for some years. In addition, there is the heat produced by machinery, lights, and men at work and the heat of adiabatic compression of air introduced into the mine. The difference in atmosphere pressure between the collar of a shaft and a level 6000 ft. below is nearly 3lb. per sq. in., resulting in an increase in heat content of nearly four B.T.U. per pound of air delivered to the mine at surface. Further the exclusive use of wet mining to reduce the incidence of miner?s phthisis increases the latent- heat content of the air.

Jan 1, 1941

By George A. Roberts, Robert F. Mehl

When austenite first forms from aggregates of cementite and ferrite, it is not homogeneous.' This inhomogeneity, consisting of both undissolved carbide and carbon concentration gradients, has a profound effect upon the characteristics of the austenite-pearlite reaction. The rate of formation of pearlite is increased by the presence of inhomogeneities2,3 and because of this (when the inhomogeneity is sufficiently pronounced) the hardenability of the steel is reduced.4,5 In addition to this kinetic effect, inhomogeneities will cause the direct formation of spheroidite from austenite at temperatures just below the Ael.6-11 The present report attempts quantitatively to evaluate the effect of inhomogeneity upon the rate of the austenite-pearlite reaction, presents a method of determining the austenitizing cycle necessary to obtain "practical homogenization," and considers the effect of inhomogeneity on hardenability. Effect of Inhomogeneities on Reactions Near Ae1 Few quantitative data are available representing the effect of undissolved carbide or of carbon concentration gradients upon the rate of the austenite-pearlite reaction. In procuring such data it is necessary to separate the effect of undissolved carbide from that of grain size, and this is not an easy task. The solution of carbide is always accompanied by an increase in the grain size, both effects contributing to the retardation of the reaction rate. It has been possible to make this separation and to obtain data that are independent of the grain size by the use of steels that differ only with respect to their tendency toward grain-coarsening. Steels C and D in Table I are such steels. These steels have been studied previously ;l,2,12 they differ only with respect to deoxidation practice; C was deoxidized with silicon while D, teemed from a portion of the same heat, was deoxidized with additional auantities of aluminum in the mold. C therefore is what is normally termed a "coarse-grained steel" and D is a, "fine-grained steel." These steels can be compared at the same grain size by heating c to a low temperature and heating D to an elevated temperature, producing a structure of austenite plus residual carbide in the former while forming homogeneous austenite in the latter; in such

Jan 1, 1943

By George A. Roberts, Robert F. Mehl

When austenite first forms from aggregates of cementite and ferrite, it is not homogeneous.' This inhomogeneity, consisting of both undissolved carbide and carbon concentration gradients, has a profound effect upon the characteristics of the austenite-pearlite reaction. The rate of formation of pearlite is increased by the presence of inhomogeneities2,3 and because of this (when the inhomogeneity is sufficiently pronounced) the hardenability of the steel is reduced.4,5 In addition to this kinetic effect, inhomogeneities will cause the direct formation of spheroidite from austenite at temperatures just below the Ael.6-11 The present report attempts quantitatively to evaluate the effect of inhomogeneity upon the rate of the austenite-pearlite reaction, presents a method of determining the austenitizing cycle necessary to obtain "practical homogenization," and considers the effect of inhomogeneity on hardenability. Effect of Inhomogeneities on Reactions Near Ae1 Few quantitative data are available representing the effect of undissolved carbide or of carbon concentration gradients upon the rate of the austenite-pearlite reaction. In procuring such data it is necessary to separate the effect of undissolved carbide from that of grain size, and this is not an easy task. The solution of carbide is always accompanied by an increase in the grain size, both effects contributing to the retardation of the reaction rate. It has been possible to make this separation and to obtain data that are independent of the grain size by the use of steels that differ only with respect to their tendency toward grain-coarsening. Steels C and D in Table I are such steels. These steels have been studied previously ;l,2,12 they differ only with respect to deoxidation practice; C was deoxidized with silicon while D, teemed from a portion of the same heat, was deoxidized with additional auantities of aluminum in the mold. C therefore is what is normally termed a "coarse-grained steel" and D is a, "fine-grained steel." These steels can be compared at the same grain size by heating c to a low temperature and heating D to an elevated temperature, producing a structure of austenite plus residual carbide in the former while forming homogeneous austenite in the latter; in such

Jan 1, 1943

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By Scott Turner

HOSTS of friends will rejoice that T. A. Rickard has been given honorary membership in the Institute. It might well have been done long ago, since, when one reviews distinguished services rendered by individuals to our organization and our profession, it is at once apparent that his name ranks high and that he has merited this distinction for more than three decades. Our by-laws restrict this list to twenty names; "T.A." becomes the sixteenth living member. Young engineers should particularly be pleased; Mr. Rickard has had a career rich in human interest, and full of useful suggestions to the younger men; he has given them good advice and set them a notable example; he, more than anyone else, has shown them how technical writing can be clear and concise; he has inspired youngsters to do their best; he has been their friend. No one has more first-hand knowledge of these facts than the writer of this appreciation:

Jan 1, 1935

By C. R. Ince

THE term "differential flotation" is used to denote a flotation operation in which separation is effected between two or more minerals of the same class; e. g., lead sulfide from zinc sulfide, pyrite from blende, chalcopyrite from pyrite, chalcopyrite from blende. At present, so far as published work shows, there seem to be two theories as to the mechanics of differential flotation. The earlier and more generally accepted theory is that the so-called depressing agents alter the surface of one or more of the sulfides in the ore, either by chemical action or adsorption, so that it is no longer amenable to flotation, but that these depressed sulfides can be revived, after the unaffected sulfide has been floated, by reagents which react chemically with the altered surface and make it amenable to flotation. More recently, Professor Taggart1 has advanced the theory that slime adsorption is an important factor in differential flotation. He believes that, with the proper use of a class of agents, which he calls .dispersion agents and which include practically all the depressing agents, one can cause the slime to adsorb differentially on sulfide surfaces. A gangue-slime coated sulfide surface will act as a gangue particle and will not float. If, subsequently, an agent that will remove the gangue-slime coating is added, the sulfide again assumes its original surface and can be floated as an ordinary sulfide. This-is the basis of the slime theory of differential flotation. Timber Butte mill at Butte, Mont., is a typical lead-zinc flotation concentrator. Neihart ore, chosen for investigation in this work, is one of the custom ores treated at that mill. Practice at Timber Butte mill in February, 1928, was as follows: A combined lead-zinc concentrate was first made using 0.2 lb. per ton on the ore of potassium xanthate and 0.03 lb. per ton of Cleveland Cliffs oil after 1.5 lb. per ton of lime and 1 lb. per ton of calcium chloride has been added just before the ball mill. The concentrate was then thickened to 70 per cent. solids. Potassium cyanide to the amount of 0.3 lb. per ton and zinc sulfate in the quantity of 0.5 lb. per ton were added to the thickened pulp and the whole

Jan 1, 1929

By D. M. Blacknall, N. N. Winogradoff, E. W. Williams

Low-temperature measurements of photolumines-cence were used to evaluate the progvess in materials development. Variation of the impurity type, impurity concentration, and method of growth were used to clarify the chemical origin of defects in GaAs. Melt-g~ozun, epitaxial vapor-, and solution-grown samples were studied. A comparison of measurements at 77" and 20°K shows that more defects can be observed at the lower temperature. Th'vee residual defects were identified in relatively pure GaAs. These were: silicon, copper, and a gallium vacancy-donor complex. Solution growth from a gallium solution inhibits the formation of the latter two. Eleven defects were studied and the "optical" activation energy of some of these, namely, silicon, cobalt, and chromium, has not been reported in the literature before. THE discovery of the injection laser in 1962 prompted extensive measurements of the photoluminescence of GaAs. The measurements were made at 77°K on GaAs doped with shallow impurities at various doping levels and compared with electroluminescence1'2 and absorp- tion data.374 In addition, lower-temperature studies were made on relatively pure GaAS' and on GaAs doped with oxygen,5'" manganese,' and copper.' The observation of defects* in GaAs with photolu- *The word "defects" ~efers to both chemical impurities and native defects. minescence at low temperatures makes photolu mines-cence an invaluable tool in evaluating the progress in materials development. The only previous evaluation was done at 77°K when solution-grown and melt-grown GaAs were compared.O No identification of defects was made but it was shown that some of the deep-level luminescence seen in melt-grown GaAs was absent in solution-grown GaAs. The present work extends the comparison of preparation techniques to lower temperatures and to a study of epitaxial vapor-grown GaAs. It is particularly valuable for thin epitaxial layers since they cannot be analyzed by conventional analytical techniques. In addition, by varying the impurity type and impurity concentration the chemical origin and nature of defects in GaAs was demonstrated. Eleven defects were studied in all. Three of the defects were identified as residual defects which often contaminate GaAs prepared from the melt and the vapor. Only one such defect was observed in GaAs grown from a gallium solution and this was identified as silicon.

Jan 1, 1968

By George A. Roberts, Robert F. Mehl

WHEN austenite first forms from aggregates of cementite and ferrite, it is not homogeneous.1 This inhomogeneity, consisting of both undissolved carbide and carbon concentration gradients, has a profound effect upon the characteristics of the austenite-pearlite reaction. The rate of formation of pearlite is increased by the presence of inhomogeneities2,3 and because of this (when the inhomogeneity is sufficiently pronounced) the hardenability of the steel is reduced,4,5 In addition to this kinetic effect, inhomogeneities will cause the direct formation of spheroidite from austenite at temperatures just below the Ae1.6-11 The present report attempts quantitatively to evaluate the effect of inhomogeneity upon the rate of the austenite-pearlite reaction, presents a method of determining the austenitizing cycle necessary to obtain "practical homogenization," and considers the effect of inhomogeneity on hardenability. EFFECT OF INHOMOGENEITIES ON REACTIONS NEAR Ae1 Few quantitative data are available representing the effect of undissolved carbide or of carbon concentration gradients upon the rate of the austenite-pearlite reaction. In procuring such data it is necessary to separate the effect of undissolved carbide from that of grain size, and this is not an easy task. The solution of carbide is always accompanied by an increase in the grain size, both effects contributing to the retardation of the reaction rate. It has been possible to make this separation and to obtain data that are independent of the grain size by the use of steels that differ only with respect to their tendency toward grain-coarsening. Steels C and D in Table I are such steels. These steels have been studied previously;1,2,12 they differ only with respect to deoxidation practice; C was deoxidized with silicon while D, teemed from a portion of the same heat, was deoxidized with additional quantities of aluminum in the mold. C therefore is what is normally termed a "coarse-grained steel" and D is a "fine-grained steel." These steels can be compared at the same grain size by heating C to a low temperature and heating D to an elevated temperature, producing a structure of austenite plus residual carbide in the former while forming homogeneous austenite in the latter; in such

Jan 1, 1943

By Edmund D. North

In making a glass model of mine-workings, each mine will present some little individualities, to meet which will call for the exercise of special ingenuity. Having made several models, I offer the following details of the model of the Montana-Tonopah mine-workings, believing that with small changes for different conditions the method described can be successfully used in making a glass model of the workings of any mine. The model, Fig. 1, has the top, one end, and the front removed. The case is made of kiln-dried pine, painted with several coats of dead-white paint. It is made to take sheets of glass 24 by 42 in. in size, and is 18 in. high, the workings shown being on a scale of 1 in. = 40 ft., or 4800 : 1 scale. The base is made of four pieces of 2-in. material, well pinned and glued together. The back, of material 1 in. thick, is secured rigidly to the base by screws and countersinking. The four posts, 1.5 in. square, are so cut that the front and two ends of the model fit in flush with the outside edges of the posts. The top rails, 1 in. square, are fastened rigidly to the front and back posts by means of small iron braces. The ends, front, and top of the case are of 0.5-in. material; the ends and front are held in place at the bottom by pegs fitting into the base ; at the top the ends are held by buttons and the front by cupboard-hooks on the inside. Hinged hasps on the cover, fitting over staples in the end-pieces, make it easy to lock the entire case. Before the back is fastened to the base, it is cut with horizontal and vertical grooves to receive the horizontal and vertical sheets of glass, shown clearly in Figs. 1 and 2. The horizontal grooves, spaced to scale, represent the vertical distances between the levels at the shaft. The vertical grooves are placed wherever cross-sections of the workings are desired.

Jan 1, 1910

By K. R. Bixby

OPENING of numerous stripping operations in Ohio, Pennsylvania, and other districts, particularly outside the Middle West and Southwest where the large-scale stripping mines predominate, holds the limelight for the year 1940. Several factors are responsible for this expansion. One is the scarcity of untested and undeveloped properties in this central field. Another has been the development of earth-moving and preparation equipment suitable for these smaller tonnage tracts. Draglines of the Walker type, small long-range .hovels, and large-capacity tractor- drawn scrapers have to be considered. Wash boxes, designed for light tonnages, costing a few thousand dollars, have made their contribution.

Jan 1, 1941

By C. R. Ince

The term "differential flotation" is used to denote a flotation operation in which separation is effected between two or more minerals of the same class; e. g., lead sulfide from zinc sulfide, pyrite from blende, chalco-pyrite from pyrite, chalcopyrite from blende. At present, so far as published work shows, there seem to be two theories as to the mechanics of differential flotation. The earlier and more generally accepted theory is that the so-called depressing agents alter the surface of one or more of the sulfides in the ore, either by chemical action or adsorption, so that it is no longer amenable to flotation, but that these depressed sulfides can be revived, after the unaffected sulfide has been floated, by reagents which react chemically with the altered surface and make it amenable to flotation. More recently, Professor Taggartl has advanced the theory that slime adsorption is an important factor in differential flotation. He believes that, with the proper use of a class of agents, which he calls dispersion agents and which include practically all the depressing agents, one can cause the slime to adsorb differentially on sulfide surfaces. A gangue-slime coated sulfide surface will act as a gangue particle and will not float. If, subsequently, an agent that will remove the gangue-slime coating is added, the sulfide again assumes its original surface and can be floated as an ordinary sulfide. This is the basis of the slime theory of differential flotation. Timber Butte mill at Butte, Mont., is a typical lead-zinc flotation concentrator. Neihart ore, chosen for investigation in this work, is one of the custom ores treated at that mill. Practice at Timber Butte mill in February, 1928, was as follows: A combined lead-zinc concentrate was first made using 0.2 Ib. per ton on the ore of potassium xanthate and 0.03 lb. per ton of Cleveland Cliffs oil after 1.5 lb. per ton of lime and 1 lb. per ton of calcium chloride has been added just before the ball mill. The concentrate was then thickened to 70 per cent. solids. Potassium cyanide to the amount of 0.3 lb. per ton and zinc sulfate in the quantity of 0.5 Ib. per ton were added to the thickened pulp and the whole

Jan 1, 1930

By J. L. W. Birkinbine

INTRODUCTION. This paper is a discussion of a part of the mineral wealth of the States of Oaxaca and Puebla, Mexico. It does not refer to the precious metals, some miles of which, in these States, are said to have been worked before the advent of the Spanish conquistadores in the sixteenth century, as my purpose is to invite attention to the exploration of deposits of coal and iron-ores in the Mixteca region. The prominence given to coal is warranted by the great effect of the scarcity of fuel upon the industrial development of Mexico. Under the progressive administration of President Porfirio Diaz, the Republic has made wonderful advances in the past three decades; and this progress would have been greater but for the limitations imposed by expensive fuel. In the spring of 1906 I was detailed by the Birkinbine Engineering Offices, of Philadelphia, to accompany A. B. Adams, of New York, in a reconnoissance of reported deposits of iron-ores in the State of Oaxaca. The result of this expedition was the formation, in 1907, of the Oaxaca Iron & Coal Co., of which Mr. Adams became, and has remained, President and General Manager, and I have spent the past three years as Chief Engineer of this company in Mexico, principally in western Oaxaca, where field-headquarters were established. GEOGRAPHY AND POPULATION. Although the geographical anti topographical, features of the Republic of Mexico are well known, few realize that the majority. of its population is domiciled in the States which immediately surround the capital city of Mexico, including the Federal District, Mexico, Tlaxcala, Morelos, Puebla,

Sep 1, 1910

By P. R. Martin, R. B. Kelly

Drilling in Central Texas during 1933 was confined, for the most part, to the search for new serpentine plugs. Bastrop County led in this particular activity, with 50 completions during the 12 months' period, 12 of which were productive. Only one new field was opened in Central Texas during the year, it being known as "Hilbig" (Bastrop County) and was discovered by the Humble Oil & Refining Co. The finding of commercial production in the serpentine at 2500 ft. led to further search in this and surrounding counties, but without success. Bexar County actually provided the greatest amount of drilling but the activity was limited to shallow development from 400 to 2000 ft. The Edwards limestone pay, which has been such a factor in past years, received but slight attention during 1933. Unsuccessful exploration was carried on in Lee and Burleson counties. With the exception of Freestone County, the Woodbine sand area was given even less consideration. This county, because of its close proximity to Anderson and Leon counties, saw a very active leasing campaign and several important tests drilled. In Central Texas, 252 wells were completed in 1933, and of this number 52, or 21 per cent, were productive. Hilbig Field The discovery well, Humble Oil & Refining Company's Annie Hassler No. 1, was completed Feb. 16, 1933, for an initial production of 65 bbl. the first hour, through tubing and 1/2-in. choke. The production was found in serpentine at 2468 ft. and tested 37.2" A.P.I. gravity. Twelve producing wells were drilled during the year and served to indicate that not more than 300 acres would comprise the entire field. Daily production at the end of the year was 775 bbl., although the field potential was 18,240 bbl. daily through 1-in. choke. The field adapts itself to pressure maintenance, and this scientific handling is being undertaken by the Humble Oil & Refining Co. through one injection well. It is the only area in the district where work of this nature is under way. Proration of Oil The more stringent application of proration in 1933 did not affect materially the producing fields in Central Texas. This is accounted for

Jan 1, 1934

By EDBIUND U. NORTH

IN making a glass model of mine-workings, each mine will present some little individualities, to meet which will call for the exercise of special ingenuity. Having made several models, I offer the following details of the model of the Montana-Tonopah mine-workings, believing that with small changes for different conditions the method described can be successfully used in making a glass model of the workings of any mine. The model, Fig. 1, has the top, one end, and the front removed. The case is made of kiln-dried pine, painted with several coats of dead-white paint. It is made to take sheets of glass 24 by 42 in. in size, and is 18 in. high, the workings shown being on a scale of 1 in. = 40 ft., or 4800 : 1 scale. The base is made of four pieces of 2-in. material, well pinned and glued together. The back, of material 1 in. thick, is secured rigidly to the base by screws and countersinking. The four posts, 1.5 in. square, are so cut that. the front and two ends of the model fit in flush with the outside edges of the posts. The top rails, 1 in. square, are fastened rigidly to the front and back posts by means of small iron braces. The ends, front, and top of the case are of 0.5-in. material; the ends and front are held in place at the bottom by pegs fitting into the base ; at the top the ends are held by buttons and the front by cupboard-hooks on the inside. Hinged hasps on the cover, fitting over staples in the end-pieces, make it easy to lock the entire case. Before the back is fastened to the base, it is cut with horizontal and vertical grooves to receive the horizontal and vertical sheets of glass, shown clearly in Figs. 1 and 2. The horizontal grooves, spaced to scale, represent the vertical distances between the levels at the shaft. The vertical grooves are placed wherever cross-sections of the workings are desired.

Jan 1, 1910

By James Howe

EVERY engineer and user of wire rope is desirous of information that will enable him to determine whether the performance of any particular piece of rope is satisfactory, and what conditions can be changed so as to increase the life of a rope. In most cases, it is far from easy to analyze the conditions of service and tell which is the greatest factor in determining the life of wire rope. If we start on a layout for an entirely new rope system, the task of making conditions satisfactory is simplified so far as the engineering details are concerned; but if the plant requiring wire rope is in operation, any change is likely to involve the expenditure of consider-, able money to replace and change over machinery that must be kept in constant operation, because a large monetary loss will result from a shutdown for even a few days. Often wire rope is kept operating under bad conditions, as the user thinks that it is cheaper and quicker to replace the rope than to make alterations in the hoisting machinery. A typical case is a metal mine operating in what is now almost the center of a large mining city, where it owns a few acres of mineral rights. It was expected that the shaft would go to a depth of 1000 ft. (305 m.), so a moderate sized rope, about 1 ¼ in. (31.7 mm.), was used on a 6-ft. drum with a 7-ft. head-frame sheave and rather short lead from drum to head sheave. This mine has gone deeper each year until, it is now 2500 ft. deep and the rope speed has been increased from 1500 ft. per min. to over 3000 ft. The original rope just filled the drum in one layer, now it overwinds three layers. The original ropes were probably 6 X 19 crucible steel and lasted from 12 to 18 mo.; now, the highest grade plow steel is used, yet the average service is only about 6 mo. The cause is not hard to find. If the engineers had known at the outset what would be done with this hoist, the design would have been very different. Conditions at this mine, from a wire rope standpoint, have gradually become worse and it is difficult to see how rope service on this hoist can be com-pared with the service of previous years with any fairness to the wire-

Jan 2, 1922

By B. D. Cullity

This investigation of bismuth-selenium alloys was made in an attempt to find a suitable material for use in thermoelectric generators. These devices are simply thermocouple circuits designed for the efficient production of electrical energy from thermal energy, which may in turn be derived directly from solar radiation or from the combustion of fuels. The requirements of a material for use in a thermoelectric generator are obviously quite different from those of a material used in a temperature-measuring thermocouple. Naturally, for power generating purposes, the thermoelectric power (voltage produced per degree difference in temperature between the junctions) must be as high as possible. Furthermore, in order to obtain reasonably high power outputs, the materials used in the generator must have an electrical conductivity which is as high as possible. Finally, in order to minimize heat lost by conduction to the cold junction, the thermal conductivity must be as low as possible. The relation between these several factors and the efficiency of conversion of thermal into electrical energy—the thermoelectric efficiency—has been discussed by Telkesl in a recent review of the subject. She gives the thermoelectric efficiency as: W o Efficiency = -Wo ______________i____________ TR-TC+ O2TR-Tc) where W, = power output in external load (watts) Wi = rate of heat input to hot junction (watts) TE,T, = temperature of hot and cold junctions (oA) K1,Kz = thermal conductivity of the two thermocouple materials (watts/cm°C) p,,pz = electrical resistivity of the two thermocouple materials (ohm cm) 9 = thermoelectric power (volts0/C) For many materials, some of the desired properties (for example, high electrical and low thermal conductivity) are almost mutually exclusive; the problem thus becomes one of finding a material which has the optimum combination of pfoperties. Bismuth-selenium Alloys work on the equilibrium diagram of the bismuth-selenium alloys has been reviewed by Hanson who gives the diagram reproduced in There are two intermediate phases in this system, BiSe and Bi²Se3. The existence of an alpha and beta modification of BiSe has not been demonstrated satisfactorily and the writer found no evidence of it in the present work. BiSe and Bi2Se3 have, like bismuth, a rhombohedra1 crystal

Jan 1, 1949

By J. R. Long, T. R. Graham, R. G. Feustel, R. S. Dean

THE comprehensive study of the copper-manganese-zinc alloy system in the Bureau of Mines Laboratories has so far been principally concerned with alloys that lie within the alpha solid solution field of the system. Two regions, one centering about 65 per cent copper, 10 manganese and 25 zinc, and the other centering about 70 per cent copper, 20 manganese, 10 zinc, have been carefully examined.1,2 These have indicated that when the alloys are made with electrolytic manganese considerable amounts may be readily introduced and that the strength and hardness are increased without excessive losses in ductility. In the course of the work of establishing the limits of the alpha solid solution range,3 enough of certain of the alloys was prepared to permit determination of their physical properties at a future date. The 60 per cent copper alloys concerned here are part of that series. They cross through the alpha field and into the adjacent alpha plus beta and alpha plus X fields, and are of interest because they offer some information on the effects of manganese on alloys lying in these fields. COMPOSITION AND FABRICATION OF ALLOYS The chemical composition of the alloys involved is given in Table I. They were intended to contain 60 per cent copper with manganese increasing from 5 to 25 per cent in 5 per cent steps and zinc decreasing [ ] from 35 to 15 per cent. The analyses are so close to the intended composition that the alloys will be referred to hereafter by their nominal compositions. They were finished into sheet by cold-rolling and intermediate annealing procedures calculated to produce sheet 1/16 in. thick, cold-reduced by 20, 40, 60, and 80 per cent in thickness. Physical properties were determined on standard flat tensile specimens with 4-in. gauge length, although the test gauge section used was 2 in. The properties were obtained on cold-worked material and on material annealed at temperatures ranging from l00° to 1500°F. after 60 per cent cold reduction. Since an annealing temperature of 1200°F.

Jan 1, 1946