Search Documents

By AIME AIME

ALTHOUGH the present economic depression is felt in the petroleum industry, probably as much as in any other branch of American industry, the Petroleum Section of the Institute was well represented at the general sessions on Monday and at all of the seven division sessions on Tuesday, Wednesday and Thursday. The seven sessions of the Division were so arranged as not to conflict and thus permitted members to hear the programs of all sessions.* The first meeting of the Petroleum Division was held on Tuesday afternoon; a joint session on engineering research and production engineering. The following papers were presented:

Jan 1, 1931

By J. R. Campbell

In order to discuss the subject intelligently, it will be necessary to touch briefly on the forms in which sulphur is supposed to exist in coking coal to be carbonized in beehive or byproduct ovens. Sulphur is known to exist in coal as sulphides and sulphates, as can be determined experimentally. Then there is the so-called organic sulphur, i.e., sulphur in combination with the carbon, 'hydrogen, and oxygen of the coal, about which much has been written, but nothing definitely proven in an experimental way. In fact, so far. as we know, there never has been developed a satisfactory and conclusive method in the laboratory for the direct determination of organic sulphur. For most coking coals, it can be safely assumed that the preponderance of sulphur is in the form of pyrite (FeSz). When exposed to comparatively low temperatures during the coking process, it loses its sulphur according to the following chemical reaction: 7FeS2 = Fe7Ss + 6S. It will be seen, therefore, that six out of the 14 atoms of sulphur (or 42.8 per cent.) are expelled, or volatilized. FelSa remains in the coke as pyrrhotite, or magnetic sulphide of iron; this accounts for the highly magnetic properties of the powdered coke. A more commonly accepted reaction is FeS2 = FeS f S, in which the straight sulphide of iron is produced with 50 per cent. volatilization of sulphur. In the beehive methods of coke making, air is introduced in sufficient amounts to carry on the distilling and the coking processes, and the sulphur is oxidized along with the other volatile products: First, into sulphur dioxide (SO2), known by the pungent andsuffocating odoremitted from the trunnel head; second, into sulphuric anhydride (SOa); and, finally, into sulphuric acid, as it comes into contact with the air and moisture. In a properly regulated draft on a beehive oven, there is never complete combustion of the gases. In other words, the coking process should be carried on in a reducing atmosphere, and a low-grade producer gas kept issuing from the trunnel head. For coals of about 30 per cent. volatile matter, the ratio of air to gas is 3½ to 1. In complete combustion, the ratio is 6 to 1, producing an extremely high temperature

Jan 1, 1916

By AIME AIME

BOB VAN PELTS boyhood days in the mining atmosphere of Colorado apparently influenced him to direct hip college education first towards geology, at. Cornell College, then to mining at Michigan College of Mines and finally to graduate work in geology at the University of Chicago. He taught geology at his alma mater. Cornell College. served as geologist for the National Park Service then was on the staff of the Illinois Geological Surrey investigating and mapping mineral resources, and in 1928 because chief of the department of geology, mining, and metallurgy in the newly organized Rosenwald Industrial Museum (now the -Museum of Science and Industry,). He was made assistant director of the Museum in 1931.

Jan 1, 1941

By H. L. B. Gould, Jr. Wenny D. H.

TO date there has been but limited interest in alloys of 80 to 95 pct Co and Fe with or without other additions. In 1932, S. R. Williams' reported practically zero magnetostriction for the 90 pct Co-10 pct Fe alloy. This same composition was used for pole pieces to control the magnetic field in magnetrons operating at high temperatures.' In 1947, a 90 pct Co, 9.5 pct Fe, and 0.5 pct Mn composition was investigated3 for use in ballast lamps because of its high temperature coefficient of resistance. Recently, as part of a survey of ductile and malleable magnetic alloys capable of being processed to thin gages for possible applications in memory devices, the high Co-Fe alloys have been re-examined to determine their fabricating and magnetic characteristics. Alloys from 80 up to 95 pct Co and Fe with and without additions such as vanadium were prepared. In general these all had excellent ductility and malleability. Wire was drawn to thin gages without difficulty and fine hard-drawn wires flattened to 2) The phenomenon may have potential in estimating the carbon content of molybdenum. A given solution-treating temperature and cooling rate could perhaps be calibrated so that the area fraction of surface covered by carbide could be interpreted in terms of carbon concentration. By segregating to the surface, a big "magnification" of the carbon content is obtained, which should make the method cheap, direct, and sensitive and, therefore, perhaps of interest to the molybdenum industry. This work was conducted at Battelle Memorial Institute. Financial support by the Aeronautical Systems Division, United States Air Force, under Contract No. AF 33(657)-7376, is gratefully acknowledged, and the writer is thankful for the experimental assistance of Miss Marjorie Cantin. ribbon without splitting. Similarly, strip was cold-rolled as much as 99.75 pct reduction to a 0.25 mil thickness without intermediate anneals. Samples of round and flat wire and foil, in the severely cold-worked and annealed states, were checked for magnetic characteristics. The alloys exhibited widely divergent magnetic characteristics depending on the processing and heat-treating procedures used in preparing the samples. Direct-current hysteresis loops showing the different magnetic characteristics of 90 pct Co, 9.5 pct Fe, and 0.5 pct Mn alloys are shown in Figs. 1 to 8 inclusive, while Figs. 9 and 10 show the loops for an alloy of 82 pct Co, 11.75 pct Fe, 5.6 pct V, and 0.65 pct Mn. Figs. 1 and 2 show the high remanence and exceedingly square-loop characteristics of the hard-drawn wire and ribbon roll flattened therefrom. With the change in processing from roll flattening to flattening by drawing through flat diamond dies the resultant change in texture is accompanied by the drastic change in the shape of the loop as shown in Fig. 3. This skewed loop on annealing reverts to a more normal loop as shown in Fig. 8. The most unique loops are obtained with flat rolled strip. These are shown in Figs. 4 and 5. In the case of the hard-rolled material, Fig. 4, there is little change in induction until the magnetizing force reaches 50 oe. From 50 to 60 oe there is a sharp increase in induction to over 15,000 gauss, which for all practical purposes is saturation. The induction remains at a constant value while the magnetizing force decreases to 40 oe. At this point the

Jan 1, 1965

By W. F. Wheeler

IN the study of the coals of Illinois now being carried on by the State Geological Survey, an attempt is being made to determine the most satisfactory basis of comparison between different coals. The following discussion is based upon work done for the survey in the laboratories of the State University and under the general direction of Prof. S. W. Parr. " Pure coal " has been defined by Mr. A. Bement1 as ash- and moisture-free coal, and the use of this " pure coal " as a basis for comparing different bituminous coals has lately been much discussed among engineers in the middle West. By some the B.t.u. of the pure coal is being used to check calorimetric results, and to calculate the calorific value of different coal-samples from the same seam, for which purposes it is necessary to assume-first, that the composition and calorific value of pure coal from different parts of the same coal-seam are uniform, and, second, that these values remain constant after the coal is mined, both of which assumptions there are reasons to believe are inconsistent with the facts. Certain variables are included in pure coal, as ordinarily defined, and disregard of them may lead to serious error. In any event, where delicate shades of difference are involved, no sure interpretation of results can be made, unless these variables be eliminated. As a basis of comparison between coals, ash- and moisture-free coal is much to be preferred to " dry coal," and still more is it to be preferred to " moist coal," as ordinarily reported in analyses. There are, however, two constituents other than ash and moisture which are similar in effect to them, and which

Jan 1, 1908

By C. G. Black

The purpose of this paper is to present data obtained from an investigation conducted on the grindability of coal by the American Society for Testing Materials Tentative Standard ball-mill method. This investigation has been conducted over a period of a year, during which time several hundred tests were run on a wide selection of different coals coming from Pennsylvania, Ohio, West Virginia and Kentucky. The data herewith presented tend to show that the tentative standard ball-mill method might give results that are misleading and that a volume measure might be more indicative of the true grindability of materials of varying specific gravity. A means whereby the time element might be reduced has been studied and other phases of this work such as preparation of samples, mechanical screening, reporting results and duplicating tests have been investigated. It is hoped that all criticism offered in this paper will be taken as constructive, with the purpose ill mind of perfecting the method now tentative to show the true conditions 2nd of making optional the manner in which certain parts of the test might be conducted to meet diversified laboratory conditions. Weight and Volume The results of grindability on extraneous material from the coal scam obtained with the present tentative standard ball mill method indicate easier grinding of these materials as compared to most coals. Varying amounts of these impurities in the coal therefore may cause a raising of the grindability index and may lead to the erroneous conclusion that coals containing large amounts of these foreign materials are easier to grind. For a true comparison of grindability, it would seem necessary to grind to the same particle weight. If material were sized in a commercial mill by means of an air current set at a velocity to remove 1.60 sp. gr. float coal ground to 80 per cent minus 200 mesh, any 1.60 sink particles would be left behind, and in order to remove this 1.60 sink material by the same current it would be necessary to grind finer and produce a

Jan 1, 1936

By C. G. Black

The purpose of this paper is to present data obtained from an investigation conducted on the grindability of coal by the American Society for Testing Materials Tentative Standard ball-mill method. This investigation has been conducted over a period of a year, during which time several hundred tests were run on a wide selection of different coals coming from Pennsylvania, Ohio, West Virginia and Kentucky. The data herewith presented tend to show that the tentative standard ball-mill method might give results that are misleading and that a volume measure might be more indicative of the true grindability of materials of varying specific gravity. A means whereby the time element might be reduced has been studied and other phases of this work such as preparation of samples, mechanical screening, reporting results and duplicating tests have been investigated. It is hoped that all criticism offered in this paper will be taken as constructive, with the purpose ill mind of perfecting the method now tentative to show the true conditions 2nd of making optional the manner in which certain parts of the test might be conducted to meet diversified laboratory conditions. Weight and Volume The results of grindability on extraneous material from the coal scam obtained with the present tentative standard ball mill method indicate easier grinding of these materials as compared to most coals. Varying amounts of these impurities in the coal therefore may cause a raising of the grindability index and may lead to the erroneous conclusion that coals containing large amounts of these foreign materials are easier to grind. For a true comparison of grindability, it would seem necessary to grind to the same particle weight. If material were sized in a commercial mill by means of an air current set at a velocity to remove 1.60 sp. gr. float coal ground to 80 per cent minus 200 mesh, any 1.60 sink particles would be left behind, and in order to remove this 1.60 sink material by the same current it would be necessary to grind finer and produce a

Jan 1, 1936

By M. J. Pool, P. J. Spencer

Using liquid tin as the solvent metal, the heats of solution of silver and gold in dilute Ag-Au-Sn alloys have been determined at 723°K by solution calorimetry. From the values obtained, the various enthalpy interaction coefficients in the liquid solutions have been calculated. The self-interaction coefficients Au and Ag values of 2413 and -6322 cal per g-atom in binary Au-Sn and Ag-Sn alloys, respectively. For an alloy containing 0.04 mole fraction Ag, Au is equal to 2443 cal per g-atom, and in an alloy containing 0.04 mole fraction Au, Ag has a value of —8883 cal per g-atom. Ag Au has been determined as —2650 cal per g-atom. ADDITION of a second solute to a dilute binary alloy may cause striking changes in the thermodynamic characteristics of the alloy. As yet, such influences cannot be reliably predicted and it is only by accumulation and critical assessment of data that definite patterns can be established. Solute interactions in dilute solutions were first treated mathematically by Wagner,1 who derived expressions for the Gibbs energy interaction coefficients. For an alloy consisting of. two dilute solutes, i and j, in a solvent s, these coefficients are given by: where yi is the activity coefficient of component i and x represents the mole fraction of solute or solvent. Other interaction coefficients have since been established in terms of the various partial molar thermodynamic properties of an alloy; the definitions of these are summarized in a recent paper by Lupis and Elliott.2 Mathematical and experimental studies of such coefficients have received much attention recently, providing a very useful theoretical background to an understanding of the nature of solute interactions taking place in dilute solutions. One of the definitions to arise from such work has been the extension of Wagner's treatment by Lupis and Elliott4 to include an enthalpy interaction coefficient, defined as. where ?Hi is the relative partial molar enthalpy of component i. ?Hi is related to the relative partial molar enthalpy at infinite dilution, ?Hio, and to the enthalpy interaction coefficients by the expression: Values of ?Hi can often be obtained with a high degree of accuracy by calorimetry, and, if the composition of the alloy is carefully controlled by making calculated solute additions throughout a series of measurements, application of Eq. [2] will enable reliable enthalpy interaction coefficients to be determined. Partial heats of solution must be investigated as a function of solute concentrations down to xi = 0, and, since ? values are obtained from the slope of mi plotted against x, great care must be taken to obtain precise data. The data for binary systems which are presently available often require extrapolation of ?Hi values from compositions as great as xi = 0.05 or even 0.1 to obtain limiting heats of solution. Reliable enthalpy interaction coefficients are thus impossible to obtain from published data for most of the alloy systems already investigated. The aim of the present work was to determine values of Au, Ag, Ag, and Au in the limit xsn -1 for the relatively simple Ag-Au-Sn system and from these results to gain some insight into the possible influence

Jan 1, 1969

By Paul M. Tyler, Carle R. Hayward

DOES it pay to do really good work? Quite likely the practical millman will answer that it does not. The preparation of ores for market is primarily a business enterprise, and by and large the individual operator does not bother his head about squandering our national resources or making easier the job of the smelterman. Having accepted such ore as he may get fro111 the mine, his job is to make the best possible showing with his mill fro111 the standpoint of financial return. His success is measured in dollars and cents, and he has no rightful reason to expect more than scant acknowledgment of any other achievements from the stock- holders of his company who in the last analysis are his employers.

Jan 1, 1936

By AIME AIME

Adjustable Pyrometer-Stand. By L. W. BAHNEY, xxxvii, 33. Agency of Manganese in the Superficial Alteration and Secondary Enrichment of Gold-Deposits in the United States. By WILLIAM H. EMMONS, xlvi, 767. Application of Descriptive Geometry to Mining-Problems. By JOSEPH W. ROE, xxxix, 173. ARNOLD, C. EVERARD. The Giroux Shaft at Kimberly, Nev., xlii, 461. BAHNEY, L. W. An Adjustable Pyrometer-Stand, xxxvii, 33. BALL, SYDNEY H., and SHALER, MILLARD K. Mining-Conditions in the Belgian Congo, xxxix, 253. BEALS, ROGER L., and TWEEDY, GEORGE A. Cyanide-Plant and Practice at the Minas del Tajo, Rosario, Sinaloa, Mexico, xxxviii, 123.

Dec 1, 1910

By Elmer R. Kaiser

COMBUSTION of coal and transfer of heat from flames and gases to boiler surfaces continue to be of great interest to engineers here and abroad. Numerous investigations have been in progress to improve furnace and boiler performance and economy. The importance of better understanding of the processes and opportunities for improvement is apparent when it is remembered that heat from at least 500 million tons of coal a year the world over is being transferred to boiler water at efficiencies ranging mostly between 50 and 90 pct. Even slight gains in efficiency, economy, and labor saving become very significant when multiplied by the enormous quantity of fuel consumed. Also the competitive position of the large coal, oil, and gas industries in satisfying the fuel consumers is greatly affected by the achievements made through technical progress with each fuel. This paper is part of a continuing activity of Bituminous Coal Research, Inc., to extend the knowledge of coal utilization for steam generation and to seek promising directions for future research and development in cooperation with others. Particularly in the latter regard, numerous interviews were held during the last three years to seek the experience and advice of boiler and combustion-equipment manufacturers, electric-utility executives, and fuel engineers. A wealth of published information was also reviewed, which together with the interviews pointed to the advisability of further work on ash and sulphur control. For the present purpose a number of factors important to efficient heat liberation and recovery have been grouped as follows: 1—combustion, temperatures, and rates of heat liberation; 2—radiation, convection, and furnace and boiler configuration; 3—sponge ash, slag, and hard-bonded deposits; 4— low-temperature deposits and corrosion (cooling flue gas below dew point and air-pollution control); 5—the limitations of coal cleaning and boiler size and cost as related to fuel characteristics; 6—future possibilities and conclusions. The development of combustion apparatus for power boilers is progressing at a lively pace. There has been no letup in improvements in design of pulverized-coal-fired boilers, and there is a strong trend at present toward improving dry-bottom units. Spreader stokers with overfire jets and dust collectors as standard equipment are gaining favor. Less than 10 years in commercial use, cyclone burners are going into numerous installations here' and abroad.' Underfeed and traveling-grate stokers have long since been developed for heavy-duty operation, yet new developments in overfire jets and humidification of air blast have improved their performance. A water-cooled vibrating-grate stoker of German origin is being introduced into the United States and Canada." The primary objectives of an ideal coal combustion device are: capacity to burn the variety and sizes of coals likely to be economically available during the life of the unit; capacity to burn the coals automatically for a wide load range and rapid load fluctuations and to burn the coals completely to CO2, H2O, and SO2, which means without smoke and cinders, or carbon in the refuse; capacity to control and discharge all the ash in final granular form without ash adhesion to walls or tubes, and without flue dust; minimum furnace volume; minimum labor and maintenance; low initial and operating cost. Regardless of the method of burning, the gaseous products of coal combustion are N2, CO2, O2, H20, and SO?. By way of illustration, the coal analyses in Table I is assumed from an installation described by E. McCarthy.' When coal is burned with 20 pct excess air (theoretical air, 9.23 lb per lb of coal), the quantities of combustion gas shown in Table II are produced. In addition, the gases carry particles of fly ash, unconsumed cinders, soot particles, and small but significant amounts of vaporized oxides and sulphates of sodium, potassium, lithium, phosghorous, iron, and other metals. In recent years, germanium, one of the rare metals found in coal, has been shown to oxidize and vaporize at combustion temperatures and to be concentrated by reconden-sation at lower temperatures." Pulverized coal and cyclone flames" have peak temperatures of 3000' to 3500°F. Temperatures in fuel beds of large underfeed stokers reach maxima of 3000°F, sufficient to fuse almost any ash and to volatilize some of it. These peak temperatures are above the optimum necessary for rapid combustion, but they hasten heat transfer for ignition as well as boiler heat absorption. Furnace and gas temperatures increase with combustion air preheat. Low excess air has the same effect. Fine coal pulverization and highly turbulent combustion shorten the distance for fuel burnout, increase flame temperature, and speed up heat transfer. Rates of combustion of pulverized coal exceeding 200,000 Btu per cu ft per hr have been demonstrated in atmospheric gas-turbine combusters,

Jan 1, 1955

By S. F. Shaw

Fox some time it has been more or less recognized within the industry that a scientific control of flowing wells would result in increased production and a greater ultimate recovery of oil. About two years ago it was proposed by the writer that this control should follow principles worked out by him while handling large air-life operations. In the case of wells that had ceased to flow where a large quantity of liquid was present, the use of these principles would result in a large increase of production by using compressed air or gas to flow the well; in the case of a well flowing naturally it would take the form of controlling the gas associated with the oil, resulting either in immediate increase of production or in a reduction of the gas consumed per barrel of oil, and in both cases would result in a greater ultimate recovery from the sand. The Roxana Petroleum Corp., appreciating the advantages to be obtained by a scientific application of the principles of the air lift to oil wells, recently engaged, for a limited time, the services of the writer to work out some of the problems involved. The work was carried out at Braman, Garber and Tonkawa in Oklahoma, and at Oxford in Kansas. Following some suggestions of the writer a well was also equipped by the Roxana company at Smackover by A. S. Field.

Jan 11, 1926

THE following employment items are made available to AIME members on a nonprofit basis by the Engineering Societies Personnel Service, Inc., operating in cooperation with the Four Founder Societies. Local offices of the Personnel Service are at 8 W. 40th St., New York 18; 100 Farnsworth Ave., Detroit; 57 Post St., Son Francisco; 84 E. Randolph St., Chicago 1. Applicants should address all mail to the proper key numbers in care of the New York office and include 6c in stamps for forwarding and returning application. The applicant agrees, if placed in a position by means of the Service, to pay the placement fee listed by the Service. AIME members may secure a weekly bulletin of positions available for $3.50 a quarter, $12 a year. MEN AVAILABLE Engineer, 43, married. Sixteen years' experience mining. Desires permanent position mine superintendent. Broad knowledge all types underground mining and shaft sinking. Construction and milling experience. Prefer North American continent but will accept foreign. Presently located Australia but available May 1, 1953. M-706. POSITIONS OPEN Mining Engineer with broad exploration experience, young, single status, and must be in excellent physical condition, as nature of work will be under very primitive conditions. Salary about 25 pct more than applicants last salary rate plus travel expenses and living allowance. Duration until July 1953. Location, Burma. Y7498.

Jan 1, 1952

By Krahmann, Rudolf

THE following is an account of a survey undertaken to test the possibility of outlining a kimberlite pipe by magnetouietric methods. Kimberlite is a basic igneous rock closely related to melilite-basalt or alnoite, which occurs either in the form of volcanic plugs or as dikes intruded into rocks of various types and geological ages up to and includ¬ing the Lower Cretaceous. The famous diamond mines of South Africa are all in kimberlite pipes and these pipes are probably the original source as well of the vast alluvial deposits found in various parts of the country. The pipe chosen for this experiment is one that ' occurs on the farm Goedgevonden No. 20, about sixteen miles north of the village of Klerksdorp and ninety miles southwest of Johannesburg. Some prospecting has been done on this pipe and diamonds were produced from it but not in paying quantities. The magnetometric survey was made in June, 1932, by R. Krahmann and H. Wallisch and the results are shown on the accompanying plan. On the plan are shown also the boundaries of the pipe as exposed at the surface and details in regard to the surrounding foundations. These are taken from a geological survey made at a later date by W. Beetz, of Johannesburg.

Jan 1, 1935

By AIME AIME

Further details of the 97th meeting of the Institute, at Spokane, have been sent to members in the Special Circular of May 8, 1909, and for convenience a summary of the additional information is given later in this announcement. In spite of the present small number who have joined the party, final arrangements have been made to complete the itinerary given in the circular. It is greatly to be desired, both in behalf of the Institute and in recognition of the special courtesies to be extended on the trip, that the party be made larger. Exceptional facilities to visit the many mines and smelters have been freely provided; and members are requested to make all reasonable effort to attend the meeting at Spokane and participate in the excursions. . For those who cannot take the entire trip, it may be possible to provide special Pullman accommodations after leaving the Yellowstone Park. In order to make the necessary arrangements, however, the names of members and guests contemplating this partial trip should be sent at once to Mr. Theodore Dwight, .39 West 39th St., New York, N. Y. A special train of Pullman cars will leave Chicago September 16. This train will be side-tracked at all places visited, and the sleepers will be available for lodging and the dining-car for meals (luring the entire trip, except while taking the tour through the Yellowstone Park. The general cost of the trip per member will be $300, which includes transportation, berth, and meals for the entire trip from Chicago back to Chicago, almost 6,000 miles, and the tour through Yellowstone Park, occupying in all about 30 days. Special accommodations on the train will be furnished at the following rates

Aug 1, 1909

CRUSHING and concentration flow-sheets of western mills have become greatly simplified and more or less standardized of recent years with the introduction of modern grinding methods and flotation. Improvement has not stopped, however, and advancement is continually being made in crushing and milling practice. A case in point, where remarkable improvements in efficiency have resulted from comparatively minor changes in the flow-sheet, is in the New Cornelia mill of the Calumet and Arizona Mining Co. at Ajo, Ariz. This mill, completed in 1924 for the concentration ,of the sulfide ores of the New Cornelia mine, was originally designed for a 5000-ton capacity. Before recent changes and additions were made the five 1000-ton units were handling 6500 to 7000 tons per day, giving a flotation feed of approximately 14 per

Jan 1, 1930

In Mr. Weed's interesting paper, frequent reference is made to the Cananea copper-deposits, which are said to have been so vigorously exploited that they produced 14,000,000 Ib. of copper in 1901. The ore-bodies which yielded this large quantity of metal are described as a product of contact-metamorphism, and in Mr. Weed's genetic classification of such deposits, they receive a place under the sub-heading, "Deposits impregnating and replacing beds of contact-zone."* They are considered by Mr. Weed to represent a special type under this head, and are further classified as: " l. Chalcopyrite deposits: (a) Pyrrhotite ores; (6) Magnetite ores, Cananea type." In condensing much information into a comparatively small space, the presentation of a subject may be so abbreviated as to detract from its clearness. The situation at La Cananea, considering its importance from an economic as well as scientific standpoint, may he worthy of more detailed description. As Mr. Weed rightly remarks, " structural differences are so important, and have SO marked a bearing, not alone on the theory of their genesis, hut also on the working of the deposits and a determination of their value as mines, that they merit a full discussion."† It is my present purpose: (1) to show that it is doubtful whether the copper of La Cananea is mined, except to a limited

Jan 1, 1903

By Howard Willey

Mining operations of the Charcas unit at present are limited to the Tiro General mine at Charcas, in the State of san Luis Potosi, Mexico. The Tiro General mine was first operated during the Spanish occupation of Mexico for rich silver ores in an oxidized zone along the outcrop of the principal vein. In depth the ore is a complex sulfide with widely varying proportions of sphalerite, argentiferous galena and chalcopyrite ; and until recent years, it was economically impossible to carry on mining otherwise than irregularly in sections of the veins richest in galena and chalcopyrite. The advent of selective flotation brought the orebody as a whole within the field of economic interest, and a flotation mill of 650 metric tons daily capacity was constructed in the year 1925. The mining of partly worked-out sections of the mine, as well as the very heavy ground in most of the stopes opened in virgin ore, presented an unusually difficult problem. This paper describes the so-called "filled top slice" stoping method finally adopted as the standard system. Physical and Geological Conditions The principal orebody of the mine is an oreshoot about 1400 ft ng in a fissure vein striking about east and west and with an average lip of 70" to the north. The footwall of the orebody is fairly cleancu and regular both longitudinally and vertically and generally shows a dell-marked post-mineral slip. The footwall rock varies from a fairly strong limestone to a broken, metamorphosed limestone which requires heavy timbering. In some sections it is an altered, crumbly porphyry, which swells badly and necessitates frequent renewal of drift and raise tirnber. The hanging wall is irregular and frequently an assay wall. The stopina width ranges from a few feet up to more than 90 ft.; it averages about 30 ft. For the most part the hanging-wall rock is a shattered and altered monzonite porphyry, nearly aways requiring heavy timbering. The orebody is greatly fractured by post-mineral movement, which usually followed the footwall and left it as a smooth surface frequently covered with a slippery clay gouge. Two well marked transverse faults

Jan 1, 1931

By Henry M. Howe

In my original paper, Piping and Segregation in Steel Ingots, I pointed out1 among other things that, in view of the slighter stretching (virtual expansion) of the crust, and greater opportunity for sagging, there should be less piping in broad than in narrow ingots, and less in slowly-cooled ingots, e.g., those cast in pre-heated sand molds, than in those which cool quickly, e.g., those cast in iron molds. A. A. Stevenson said that neither of these predictions agreed with his own experience. In particular, in a picture which he showed of a wide and of a narrow ingot cast from the same ladleful of steel: the wide ingot had certainly piped much more deeply than the narrow one. At the time I did not see the explanation of these discrepancies, but further reflection makes it evident. One of the most important elements in determining the depth of the pipe is the degree of " top-lag," that is, the degree to which the solidification of the top of the ingot lags behind that of the bottom. Through this lagging the steel of the upper part of the ingot is able to run down and fill the pipe below as fast as it forms. To the importance of this lagging I called attention in my original paper.' Sand us. Iron Molds.—If we compare two like ingots, one cast in an iron and the other in a sand mold, we see that the top-lag is much greater in the former than in the latter, because in the former the lower part of the ingot is cooling off fast while the metal is running into the upper part. It is perhaps easier to look at this as a case of the solidification of the hot-

Jan 1, 1910

By GEORGE W. HARHIS

IN the earlier period of anthracite-ruining, much coal was wasted, both underground and in the culm-banks on the surface. Such waste is common in the development of new mining districts, in which, as a rule, only the richest material can be profitably treated. In the anthracite-region, special causes operated to increase this evil. The mines were generally operated under 20-year leases, and royalties were paid upon such coal only as was actually marketed. The lessees consequently cared for immediate profit only. They were- not bound to win all the coal they exposed, or to leave it in such condition that their successors could win it. Nor was it their interest or duty to educate consumers in the use of their product. The market called for coal of large sizes ; and such coal they furnished, throwing away the rest. Any pains taken by them to bring about a more rational use of coal by their consumers would have borne fruit, after their leases had expired, to the benefit of somebody else. A full statement of the situation wits given in 1893, in the report of the State Commission, appointed in 1889 to investigate the subject.` That body included the names of Heber S. Thompson, William Griffith and the late Eckley B. Coxe.2 Its report gives special attention to the utilization of the old culm-banks.

Nov 1, 1905