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By Arthur Lubinski, K. A. Blenkarn

It is explained why the bottom portion of freely suspended tubing in a pumping well buckles and straightens in succession during the pumping cycle. Field evidence of resulting rod-on-tubing wear, excessive polished rod load, and excessive horsepower are given. The possibility that buckling hastens pump wear is strongly suggested. Means for either prevention of buckling or for mini-mizing its effects are explained, their relative merits compared, and field results of their use given. These means are: tension anchors, tail pipe, sucker rod guides, and corrosion inhibitors. Charts and formulas for best use of tension anchors, tail pipe, and guides are given. Use of tension anchors, or compression anchors with a heavy tail pipe, prevents both buckling and breathing, thus improving volumetric efficiency. Without tail pipe, buckling above compression anchors precludes such improvement. INTRODUCTION It is well known that a column must be subjected to some compression in order to buckle; and also that a structural member does not buckle if subjected to a tension. When consideration is given to a tubular column, the question may be asked, "How is the buckling phenomenon affected by inside or outside pressure?' At first, it seemingly should not be affected. However, this is not so. In order to arrive at a correct deduction one should first understand the basic reasons for buckling of a column under loading*. Then he should add to the effect of that loading the effect of pressure. Following this procedure, one may discover quite unexpected phenomena. In some cases, when subjected to more pressure inside than outside, a pipe may buckle under tension. In other cases, a pipe may remain straight, although subjected to a very large compression. In 1950 and 1951 it was explained why the bottom portion of a string of pipe freely suspended in a well does not buckle even when subjected to a large compression due to buoy- ancy.2,3 It was shown that the com-monly used concept of a neutral point, as being a point in the string with neither compression nor tension, is inadequate, and a more relevant definition of the neutral point was introduced. The findings were also generalized to cases of different pressures inside and outside a pipe.3a Later, in a further generalization, allowance was made for variations of stress and pressure with depth.' The findings were applied to the new technique of hydrostatic high pressure testing of lengths of pipe in the mill.5 In 1952 it was observed that previous theoretical findings apply to tubing in pumping wells. The lower part of freely suspended tubing buckles during the upstroke portion of the pumping cycle. Later, it was ascertained that this phenomenon is responsible for wear and malfunctioning of the equipment. Various remedial measures were devised and successful field trials conducted. Only brief mentions on the subject have been published.6,7 In this paper, the phenomenon of tubing buckling is explained, field

Jan 1, 1958

By John V. W. Reynders

Our entry into the World War suddenly brought home to us in a startling way the vital importance of manganese. Since the war, much has been written and said upon the subject of manganese and a great deal of time and money have been spent in attempts to find an adequate substitute for this metal in the manufacture of steel; none has been found. It is true that ways are known by which it is possible to make small amounts of good steel without manganese, but taking into consideration the diminishing quality of iron ores and fuels as well as the increasing exaction of specifications for finished products, it may safely be assumed that, high-grade manganese ore will be more and more a necessity in the production of steel as time goes on. Taking world resources as a whole it may be well to point out that the problem of obtaining needed supplies of manganese from a strictly commercial viewpoint is now less serious than it was before the war. Formerly it was feared that world resources of high-grade manganese ore might be exhausted in a relatively short time, but, largely as a result of the stress laid upon the importance of manganese during the war, the world's available supply of high-grade manganese ore has been greatly augmented by new discoveries and fuller development of previously known deposits. Sources of Production Russia alone, of countries producing the major part of the world's stee1, has within its geographical boundaries sufficient manganese to supply its needs. The domestic production of England is inadequate and English requirements for high-grade manganese are supplied principally from India. France also draws largely upon India, as it depends upon foreign sources of supply except with respect to a small tonnage of silico-manga-nese and silico-spiegel produced in the Hautes-Pyrénées. Germany and the United States likewise depend upon foreign sources of high-grade ore, though each possesses comparatively large reserves of ferruginous manganese ore and manganiferous iron ore. At present the world demand for high-grade manganese ore is met with ease by the production of Russia, India, Gold Coast and Brazil.

Jan 1, 1927

By Ralph Smith

DEVELOPMENT of the lime industry in Ste, Genevieve County began in a crude way in 1840. According to information furnished by the Missouri Bureau of Geology, in the early days small vertical kilns built of stone were used, and wood was the fuel. Modern development began in 1904 when one company introduced steel shells lined with firebrick. Within a few years two more companies erected similar plants, and in 1925 a fourth company began operations. Thus there are today four lime companies at Ste. Genevieve, all operating at high capacity and with a gradually increasing production. GEOLOGY The limestone of Ste. Genevieve County, which has the chemical composition and purity required for lime burning, is the upper 80 or 90 ft. of Spergen formation. The Missouri Bureau of Geology, in its geological map of Ste. Genevieve County, gives the Spergen formation a total thickness of 160 ft., but only the upper portion is pure enough for lime burning, with an average raw-stone analysis of 98.7 per cent CaCO3; 0,35 Si02; 0,3 R203; 0.35 MgCO3; 0.3 SO3. The Spergen, one member of the Meramac group, Iowa series, of the Mississippian system, underlies an area approximately 12 miles long north and south, by 5 miles wide east and west (Fig. 1) in Ste. Genevieve County. The entire eastern two-thirds of Ste. Genevieve County is sedimentary, the formations dipping gently toward the east on an average grade of about 4 per cent, or 2 ½ °. Thus the outcrops of the various sedimentaries run approxi-mately north and south. A line running west from Ste. Genevieve crosses the outcrops of the sedimentaries, ranging from the top of the Mississippian to the Ozarkian geological system in a space of 12 miles. Thus with the gentle dip of 2 1/2° the 160-ft. thickness of the Spergen formation stretches out in its outcrop so that it is approximately one mile

Jan 1, 1938

By B. M. Larsen, L. S. Darken

Some years ago we collated all laboratory data then available to us on the distribution at equilibrium of manganese and of sulphur between metal and simple slags, and used the results in setting up an equation, which proved to be in accord with determinations of the distribution ratio of manganese and of sulphur between liquid steel and open-hearth slag, over a wide range of operating conditions. We now present an outline of our calculations and inferences on these two closely related questions, which are of especial importance because of the advisability of conserving manganese wherever possible. In general, our results show that in the open-hearth furnace equilibrium between metal and slag, with respect to both manganese and sulphur, is substantially attained during the finishing period of the heat, or in about a half hour to an hour after any additions were made. This implies that the end result will be identical whether manganese is added as alloy or metal to the liquid steel or as oxide to the slag. The proportion of total manganese retained by the steel is favored: (I) by use of the minimum amount of lime, consistent with other operating limitations, required to give a lime-silica ratio of about 2.4, which usually corresponds to a minimum practical slag volume; (2) by a high concentration in the slag of MnO relative to FeO; (3) by high operating temperature. Absorption of sulphur by the slag from the liquid metal is favored: (I) by large slag volume; (2) by a high concentration of active (or "free") lime and of manganese oxide dissolved in the slag; (3) by low concentration of silica, iron oxide, and phosphate dissolved in the slag. Distribution 02 Manganese between Slag and Metal at Equilibrium On the basis that the distribution of manganese between liquid steel and slag is controlled by the reaction FeO + Mn -& MnO + Fe [A] slag metal slag metal the distribution at equilibrium, at a given temperature, is expressed by the equilibrium constant for this reaction, which is defined as K,, _ aMnO' afe aFeO ' aMn where a is the activity of the molecular species denoted by the subscript. The activity of each of the several components, although it is not known precisely, is approximately equal to the concentration of each component expressed as its mol fraction; that is, as the ratio of the number of mols of the given component to the total number of mols of all the molecular species present in the metal or slag, as the case may be. Moreover, since the activity, or concentration, of iron in the liquid metal is in fact substantially constant, the term afe may be combined with K" to give a new constant K'. Making these changes, 7

Jan 1, 1942

By B. M. Larsen, L. S. Darken

Some years ago we collated all laboratory data then available to us on the distribution at equilibrium of manganese and of sulphur between metal and simple slags, and used the results in setting up an equation, which proved to be in accord with determinations of the distribution ratio of manganese and of sulphur between liquid steel and open-hearth slag, over a wide range of operating conditions. We now present an outline of our calculations and inferences on these two closely related questions, which are of especial importance because of the advisability of conserving manganese wherever possible. In general, our results show that in the open-hearth furnace equilibrium between metal and slag, with respect to both manganese and sulphur, is substantially attained during the finishing period of the heat, or in about a half hour to an hour after any additions were made. This implies that the end result will be identical whether manganese is added as alloy or metal to the liquid steel or as oxide to the slag. The proportion of total manganese retained by the steel is favored: (I) by use of the minimum amount of lime, consistent with other operating limitations, required to give a lime-silica ratio of about 2.4, which usually corresponds to a minimum practical slag volume; (2) by a high concentration in the slag of MnO relative to FeO; (3) by high operating temperature. Absorption of sulphur by the slag from the liquid metal is favored: (I) by large slag volume; (2) by a high concentration of active (or "free") lime and of manganese oxide dissolved in the slag; (3) by low concentration of silica, iron oxide, and phosphate dissolved in the slag. Distribution 02 Manganese between Slag and Metal at Equilibrium On the basis that the distribution of manganese between liquid steel and slag is controlled by the reaction FeO + Mn -& MnO + Fe [A] slag metal slag metal the distribution at equilibrium, at a given temperature, is expressed by the equilibrium constant for this reaction, which is defined as K,, _ aMnO' afe aFeO ' aMn where a is the activity of the molecular species denoted by the subscript. The activity of each of the several components, although it is not known precisely, is approximately equal to the concentration of each component expressed as its mol fraction; that is, as the ratio of the number of mols of the given component to the total number of mols of all the molecular species present in the metal or slag, as the case may be. Moreover, since the activity, or concentration, of iron in the liquid metal is in fact substantially constant, the term afe may be combined with K" to give a new constant K'. Making these changes, 7

Jan 1, 1942

By Henry N. McCarl

Lightweight aggregates include a variety of mineral and rock materials used to provide bulk in concrete building units (block), light- weight structural concrete, and precast concrete units, as plaster aggregate, insulating fill, and other structural and/or insulation purposes. They are distinguished from other mineral aggregate materials by their lighter unit weight- 80 to 100 pounds per cubic foot (pcf) or less for loosely packed lightweight aggregates as compared to 125 pcf or more for crushed stone, sand, gravel, air-cooled slag, and other more common mineral aggregates. The various lightweight aggregate materials may be classified into four groups as follows: 1) Natural Lightweight Aggregate Materials-prepared by crushing and sizing natural rock materials such as pumice, scoria, tuff, breccia, and volcanic cinders. 2) Manufactured Structural Lightweight Aggregates-prepared by pyroprocessing clay, shale, or slate in rotary kilns or on traveling grate sintering machines. 3) Byproduct Lightweight Aggregates-prepared by crushing and sizing foamed and granulated slag, cinders, and coke breeze. With the exception of processed slag, this group is becoming less important as time passes. 4) Manufactured Insulating Ultralight- weight Aggregates-prepared by pyroprocessing ground vermiculite or perlite. This chapter will focus on the use of natural lightweight aggregates and manufactured insulating ultralightweight aggregates, and both the production and use of manufactured structural lightweight aggregates with some comments on byproduct materials. Detailed discussion of the production and use of both expanded and air-cooled slag is presented in a separate chapter in the utilization section of this volume, and there are separate commodity chapters on vermiculite, perlite, pumice, and volcanic cinders. Discussion of the commodities covered elsewhere in the book will be limited to observations on their utilization and relation to other lightweight aggregate materials. All materials considered as lightweight aggregates are derived from some initial natural raw material. While historical definitions have included such organic materials as straw and peat as lightweight aggregates, the discussion in this chapter will restrict itself to lightweight aggregates derived from mineral or rock materials. Thus while the actual lightweight material in use may be a manufactured product, it is derived from an ore or raw material that is obviously a mineral resource. In this context, then, the reserves of raw materials for lightweight aggregate use may include iron ore and flux stone (the components of blast furnace slag) as well as coal (the raw material from which cinders are derived) as well as those clay, shale, and slate deposits that display the characteristics of bloating or controlled expansion when subjected to elevated temperatures (1600 to 2400°F.).

Jan 1, 1975

By R. G. Davies

Above 500°C, where dislocation climb is rate controlling, it is observed that the activation energy for creep is independent of the apblied stress, although it varies from 62 kcal per mol at 15 pct A1 to 73 kcals per mol at 20 pctA1 due to the change in short-range ovdw with composition. Below 500°C, when the nonconservative motion of jogs upon dislocations is thought to be rate controlling, the activation energy is stress dependent. A sudden increase in the creep rate, for which no explanation is availab2e, occurs at the highest stress at all temperatures. CREEP has been the subject of numerous research publications during the past decade with most of the attention focused upon high temperature steady state creep, i.e., above 0.5 TM, where TM is the absolute melting temperature, as it is the most amenable to theory. Many of the proposed theories involve the climb of dislocations out of their slip plane, which allows them to circumvent obstacles or to annihilate dislocations of opposite sign on other slip planes.' For pure metals it is observed that the activation energy for this creep is equal to the activation energy for self diffusion.' The position is much more complicated in alloys as there are many possible microcreep mehanisms, as well as dislocation climb, which could be rate controlling. There has been little systematic investi- gation of alloys, but Weertman (lead and indium base alloys)3 and Lawley, Coll, and Cahn (Fe-A1 alloys)4 suggest a microcreep process as the controlling factor. A Cottrell-Jaswon atmosphere mechanism is proposed for the lead and indium alloys, and a mechanism involving crystallographic order for the Fe-A1 alloys. Lawley et al. showed that the formation of a super-lattice, either of the FeAl or Fe3A1 type. decreased the rate and increased the activation energy for creep. From the measurements of lattice parameters,= resistivity,' magnetic properties,7'8 internal friction: and dilatometry10 the ordered region is thought to commence at -19 at. pct Al. However, a recent investigation by the author indicates a value

Jan 1, 1963

By J. W. Stewart

ONE of the postwar problems posed for mineral engineering educators is the desire of some mature student veterans to finish their college education under the G. I. Bill of Rights as quickly as possible, a desire that is quite understandable. Not only have they lost several years of education, which they wish to make up as quickly as possible, but many are married and have families and want to become productive as soon as possible in order to support their families properly. The obvious solution to this problem, if it really is serious, would appear to be a continuation of the wartime Accelerated Program, as it was carried on in most colleges and universities. As a matter of fact some schools are known to have continued their wartime programs in one or another form. To ascertain just what our mineral engineering schools generally are doing to meet this postwar problem, last April a questionnaire was sent to administrative officers at colleges and universities

Jan 1, 1946

By Be Van Presley

There has been developed at Latouche a rather unusual system of mining which, for want of a better name, has been called the "Latouche system of mining." It is a modified form of shrinkage stoping applicable to orebodies of large or fairly large size where the ground is such that timbering would not be required in stoping. Mention has been made of this method of mining by Birchll who gave no details as it had been in use only a short time and the final outcome undetermined. The system, however, has proved to be entirely successful and it is thought that a paper covering it might be of general interest. Before proceeding with a detailed description of the Latouche system a brief description of the property and the various mining methods previously used will be given. Location The Beatson mine of the Kennecott Copper Corpn. is situated on the west coast of Latouche Island, in Prince William Sound, Southwestern Alaska, 45 miles east of Seward, the coast terminus of the U. S. Government Railroad. It is a regular port of call for ships on the Southwestern Alaska run. The island is about 12 miles long and 3 miles wide. A ridge of mountains runs the entire length with a maximum elevation of 2500 feet. Climate Latouche has to contend with possibly the greatest amount of precipitation on the North American continent. The annual average precipitation for the past 4 years has been 188 in., with 248 in. for the year 1926. A rainfall of 4 in. per day is not uncommon. In the winter the thermometer rarely falls below +20° F. and the snowfall is usually heavy during the months of March and April.

Jan 1, 1928

By G. R. Speich, Morris Cohen

The growth rate of bainite has been determined by hot-stage metallography in five hypereutectoid high-purity iron-carbon, iron-carbon-chromium, and iron-carbon-nickel alloys. The studies have been confined essentially to lower bainite. The growth rate is independent of time at constant temperature, but both the edgewise and sidewise growth rates increase with increasing temperature. Increasing the carbon content, or adding chromium or nickel, decreases the growth rate without greatly affecting the temperature dependence. The results lead to separate diffusion-controlled models for the edgewise and sidewise growth rates. ALTHOUGH bainite has been subject of many detailed investigations,1,2 the growth mechanism of this intermediate transformation product of steel remains unclear. One difficulty has been that practically all the kinetic measurements have been restricted to studies of the overall reaction rate. Only a limited amount of information3, 4-6 is available on the growth process itself. The purpose of the present work was to investigate the effect of time, temperature and composition on the growth rate of bainite using hot-stage metallography. This method makes it possible to observe continuously the isothermal growth of individual bainitic units because of the surface upheavals accompanying their formation.3 This information is needed to test the existing growth models and to obtain a better understanding of the factors controlling the bainitic transformation. EXPERIMENTAL PROCEDURE Alloys—The compositions of the alloys used in the present work are shown in Table I. The five alloys were vacuum-melted and cast, and were prepared from high-purity materials. The three iron-carbon alloys were available from the work of Roberts et al.7 in the form of 3/8-in. diam rods.* To facilitate machining, the rods were ing. The rods were then tempered for 3 hr at 650°C to allow machining. The iron-carbon alloys in Table I were selected for investigating the effect of carbon on the bainitic growth rate. Due to the rapidity of the transformations involved, it was not feasible to measure the growth rates in iron-carbon alloys having carbon contents much less than 0.9 pct C. The iron-carbon-chromium and iron-carbon-nickel alloys were selected to study the influence of chromium and nickel on the growth rate at a carbon level of about 1.1 pct C, since this carbon content was intermediate among the iron-carbon alloys. The concentrations of chromium and nickel were chosen to match isothermal trans formation diagrams in the literature.8'9 Hot-Stage—Since the iron-carbon alloys had such low hardenabilities, it was necessary to quench the hot-stage specimens drastically from the austentiz-ing temperature to the isothermal transformation temperature to prevent the formation of pearlite or proeutectoid constituents. A rapid-quenching metal-lographic hot-stage was built for this purpose. A maximum temperature of about 1100°C and quenching rates up to 500°C per sec could be attained with this equipment. The details of the apparatus are described in a recent publication. After being polished and mounted on the hot-stage, the specimen (0.020 in. thick) was protected from oxidation and decarburization during austenitizing by a vacuum of 10-4 to 10-5 mm. The quench to the reaction temperature was accomplished with a helium blast, and the isothermal run at this temperature was conducted in a helium atmosphere. A fine-wire thermocouple spot-welded to the sample and a high-speed

Jan 1, 1961

By Gregory M. Dexter

Recent litigation in Pennsylvania between three coal-mining companies and a private water company resulted in the payment by the coal companies of the equivalent of about $500,000 to buy a new water supply to replace that which had been damaged by acid drainage from strip mining. An investigation of the relevant facts indicates that the water could have been treated by spending about $40,000 on equipment and $15,000 yearly for chemicals, labor, and power until the contarnination could be reduced about 80 pct. The water company's supply, furthermore, had deteriorated largely by reason of dry weather before stripping was begun by the coal companies. Payment to the water company should not have exceeded $300,000 and could have been as low as $100,000. Strip mining of coal is common in Pennsylvania. The most important objection to it in Pennsylvania is generally acid pollution of runoff water. An outline of the methods, therefore, that could be used to reduce such pollution, to compare acid-contaminated waters. and to treat such waters to make them satisfactory for public and industrial use is worth-while. The watershed of the West Penn Water Co. covers about 4.5 square miles, 20 miles west of Pittsburgh, and has two 90,000,000 gal reservoirs supplying about 1,300,000 gal daily for public and industrial use of which 450,000 gal daily are for two railroads. The pollution arises from weathered derivatives of typical'" Coal Measures"' rocks, the principal source being pyrite (and marcasite) in Pittsburgh and Rooster coals. Springs and seeps on hillsides issue from sandstone and limestone formations intersecting shale or clay land surfaces, or from perched water tables. The two reservoirs create an artificial permanent water table. Soap-hardness tests on three seepage samples taken in a dry summer ranged from 150 to 500 ppm. Water sampled came from aquifers above Pittsburgh and Rooster coals, obviating the possibility of contact with pyrite-containing coal. Since acid contamination of mine waters is the result of chemical reactions of oxygen and water with pyrite, it will be reduced by the exclusion of either air or water. The Sunnyhill Coal Co. has applied this principle in its "contouring" method of strip mining by burying contaminated coal-waste material under a compact, smoothed-up surface of top-soil, gravel, clay, and sand at a cost

Jan 1, 1950

By D. A. Keyes

International Minerals & Chemical Corp. (Canada) Ltd. is presently exploiting by underground mining a potash-rich zone in the middle Devonian Prairie Evaporite formation near Esterhazy, Saskatchewan. Of the three main potash-bearing horizons denoted by Goudie as zones 1, 2 and 3 only the 1ower. two are present at Esterhazy and mining is confined to the lower or zone 1 horizon. The area in which the evaporites were deposited, although flanked on the west by a zone of geosynclinal deposition and tectonic activity, has been subjected to only very gentle epeirogenic activity. The sylvinite ore is coarsely crystalline and occurs in well-defined beds. The halite, sylvite and insoluble content of the ore bears a direct relationship to the lithological units, but the carnallite cuts across the beds. Local concentrations of salt produce blank spots in the ore horizon. Some of these appear to be salt-filled, post-ore channels and cracks while others have been formed by brines emanating upward from below the ore. INTRODUCTION International Minerals & Chemical Corporation (Canada) Ltd. is operating an underground potash mine near the town of Esterhazy in eastern Saskatchewan. The deposit was discovered by IMC in 1955. Subsequent drilling outlined extensive high-grade reserves, and in 1957 shaft sinking and plant construction began. Production from Yarbo No. 1 Shaft commenced in September, 1962 and quickly reached the initial capacity of one million tons of muriate product per year. Production is currently being expanded to 1.6 million tpy. The single mining level is 3140 ft below the surface at No. 1 Shaft. GENERAL GEOLOGY The Esterhazy district lies within the Interior Plains region of Canada and on the northeast rim of the Williston Basin (Fig. 1). Average dip of the rock formations in this area is about 40 ft per mile to the southwest. The potash ore occurs in the Prairie Evaporite formation of the Middle-Devonian Elk Point Group. The Prairie Evaporites are overlain by 3000 ft of Paleozoic shales and limestones and by Jurassic and Cretaceous sandstones and shales (Fig. 2).

Jan 1, 1967

By James E. Howard

AT the request of the Council of the Institute, I have the honor to submit the following remarks upon the Program of Tests under which the current work of the Watertown Arsenal Testing Laboratory is carried on, which comprises, among other items, the tests of steel ingot metal and derivative shapes. The intended scope of the tests may be illustrated by extracts from the descriptive part of the program as submitted by the Laboratory under date of April 17, 1907, and subsequently approved by the Chief of Ordnance, U. S. A. Under Item 1, Ingot Metal-Open hearth, acid and basic; Bessemer, acid and basic; crucible; fluid compressed and uncompressed-descriptive remarks were made as follows ; " A thorough, fundamental inquiry into the physical properties of steel necessarily begins with the ingot metal. Investigations, having for their object the improvement of steels, should also begin with the ingot. A knowledge of the ingot structure is essential for judging of the subsequent behavior or appearance of the metal. Under ordinary conditions, so little information is obtained from the ingot in individual cases that practically none of importance is acquired. These remarks have particular reference to the state of physical and structural soundness of the steel. Questions of chemical composition, segregation, piping and the grosser cavities have frequently been given attention. Defects of continuity of structure, which manifest themselves in the working; of the metal, and at the final stages cause distrust in the finished forging, have generally been neglected. ? The range in physical properties in a given composition of metal, as shown in Tests of Metals, 1902 and 1903, is very great. Tests are there found which, when the results are

Mar 1, 1908

INTRODUCTION The geology of porphyry copper deposits in the southern Cordilleran orogen is the subject of this chapter. The area considered extends northwest from southern Mexico to the Columbia volcanic plateau, the Cascade volcanic province, and the Idaho batholith. Transversely it is a belt some 800 km (500 miles) in width bounded on the west by the Sierra Nevada range. Included within this area are many large segments considered unfavorable for hosting porphyry copper deposits, which are mentioned in the text. The region and its porphyry copper deposits have probably been more intensely studied and reported in the literature than any other area in the world. This summary considers regional geologic controls that governed formation of porphyry copper deposits within this province. Geologic factors that influenced the mineralogy and metallogeny of the deposits are also examined. Discussions with H. R. Cornwall have greatly helped in writing this section. GEOLOGIC SETTING The geologic setting has been summarized by Anderson (1966), Burchfiel and Davis (1972), Rogers, et al. (1974), and Lowell (1974). No porphyry copper deposits in this area are known to be pre-Triassic, so Mesozoic and Tertiary events will be stressed. Figs. 40 and 41 show basic data believed most pertinent to the topic of porphyry copper deposits. Pre-Middle Jurassic: Figs. 40 and 41 contain the principal structural and crustal ele¬ments found in the Cordilleran orogen after Anderson (1966), Schmitt (1966), Coney (1972), Rogers, et al. (1974), and Lowell (1974, 1976), together with location of some of the more important porphyry copper deposits. The western limit of the Precambrian craton is shown in Fig. 40 (Rogers, et al., 1974). East of that limit the crustal environment through which the porphyry copper plutons ascended includes the Precambrian basement as well as varying thicknesses of Paleozoic shelf and platform accumulations. The northwestern and western portion of the southern Cordilleran orogen west of the Rogers, et al. (1974) limit of Precambrian basement has what Churkin (1974) calls a thin continental crust. Brooks (1976) and Churkin (1974) describe oceanic volcanic

Jan 1, 1978

By AIME AIME

I would like to ask Bob Merrill whether he considers that horizontal concave curvature of a slope has any stabilizing effect, such as Jenike 1 suggested several years ago. The stabilizing effect is due to the restraint offered to radial movement by the curvature. We found in laboratory tests that if we constrained the rock with the same stresses as those measured in the pit then it would sustain a maximum stress about two or four times greater than when the same rock type was unconstrained. We are therefore definitely of the opinion that a constrained situation in a slope is favorable towards stability.

Jan 1, 1967

By THOMAS J. CLIFFORD

IN 1926, finer grinding began to be a feature of the milling practice of the Southeast Missouri lead district. Nothing since the adoption of flotation has caused greater changes and greater improvement in results. The trend toward finer grinding, with the consequent discarding of tailing at finer sizes, and consequent lower assays in lead, continued to progress until 1931, when the abnormally low price of lead brought a halt: that is, the better metallurgical results obtained would not offset the increased costs due to higher power and necessary maintenance. Since 1931 a slight tendency toward the discard of coarser tailing has taken place. , In 1926, larger rod mills i.12 ft. 1 in. by 6 ft. 6 in.) than any previously used in the district were installed in cue plant, and a new primary crushing plant, of greater capacity was built. This combination demonstrated immediately the better metallurgical results obtainable by finer grinding and all the mills now running have adopted the practice.

Jan 1, 1934

By Carlo Massa

THE Societá Auonima di Miniere e di Alti Fourni, familiarly known as the " Elba Company," works the rich ore-deposits of the Island of Elba under a long-term contract with the Italian Government. The ore-deposits are scattered over the eastern and southeastern coast; but as those parts of the island are not well provided with ports, the blast-furnaces were built at Portoferraio, the principal town of the island, situated on the northern shore, and possessing a magnificent natural harbor where even vessels as large as the battleships of the Italian navy can comfortably anchor. In the selection of Portoferraio. the cost of transporting the iron-ore from the different mines to the blast-furnaces has been reduced to a minimum, and shelter has been provided for the Company's flotilla of tugs and barges, as well as for the steamers carrying coal and pig-iron. The whole plant, of which a general view is given in Fig. 1, comprises 1. A discharging-pier with unloading-cranes. The ore and coal are transported from this pier by means of an aerial cable-rail¬way to the coal- and ore-storage yards. This cable-railway is supported by an iron bridge extending from the pier to the shore and by a wooden trestle extending from the shore to the yards. , 2. Blast furnaces, two in number, with all the accessory appa¬ratus, such as blowing-engines, dry purifiers, Cowper hot-blast stoves, hoists, etc. 3. Coke-ovens, two batteries, with coal-bin, crushers and boilers. 4. Engine-house containing the blast-engines and the electric generating-station. 5. Pumping-plant. 6. Narrow-gauge railways.

Mar 1, 1905

By Quentin Singewald

SOME of the broader relations between structure and ore deposition along the London fault, deduced from a thorough study of the geology of the eastern part of the Mosquito Range, should be of general interest to economic geologists. The first part of this paper is a generalized state-ment of the geology of the region in which the London fault is located; it may be supplemented by reference to several earlier publications by the writers and to the U. S. Geological Survey's Professional Paper 148, on the Leadville district. The second part deals with the structure of both the fault and the disturbed zone adjoining the fault. The third part dis-cusses the salient features of the ore deposits, particularly emphasizing structural control. The two generalized maps are complementary to one another but contain too many data to show on a single small map. The London fault is between Leadville and Alma, and the ore deposits along it are said to lie in the Alma district. Field work in this district, during six summers since 1927, has been a part of the cooperative work of the U. S. Geological Survey, the State of Colorado, and the Colorado Metal Mining Board. The writers have made use of work by R. D. Butler, J. W. Vanderwilt and R. E. Landon. G. F. Loughlin and C. H. Behre, Jr., who have worked on the west side of the range, have con-tributed valuable suggestions. Mining men of the district have aided in many ways.

Jan 1, 1936

By AIME AIME

IN an address before the New York Section. A.I.M.E., Oct. 20, Alex L. ter Braake, speaking on the tin industry of the Netherlands East Indies, interjected a few remarks, at the chairman's request. on the mineral stock-piling project now before Congress in a bill sponsored by Senator Scrugham. The full text of Mr. ter Braake's paper was published in the Nov. 6 issue of the American Metal Market. Following mention of the buffer stock scheme as applied in the tin industry, Mr. ter Braake continued:

Jan 1, 1943

By L. A. Mekler

THE recirculating furnace is primarily a heating apparatus of the convection type in which the heat-absorbing surfaces are heated by a mixture of fresh products of combustion and a portion of the combustion gases that have already given off a part of their heat in their previous passage over the heat-absorbing surfaces. In its basic conception, the recirculating furnace can be considered as a closed thermal system in which the heat-absorbing surfaces are .constantly swept by a fixed quantity of products of combustion at a given initial temperature with the gases being constantly returned to the furnace and reheated before they again enter the heating zone. Gases equal in amount to that produced by the fuel burned to reheat the circulating gases are constantly ejected from the system to the stack. The recirculating furnace is the most suitable apparatus for heating by convection where low furnace temperatures must be maintained and where only a small portion of the available heat is taken out of the gases, particularly where the maximum allowable furnace temperature is low and where the final temperature of the gases is only a few hundred degrees below their initial temperature. In such cases, recirculation not only provides a method of reducing the rather high combustion temperatures of the fuel when burned without a large amount of excess air, but, by returning to the furnace the heat content of the gases at their final temperature, recovers a large portion of heat that otherwise would have been lost through the stack.

Jan 1, 1928