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By M. R. Hatfield, F. J. Vosburgh

IN a recent article,† it was shown that in the blast furnaces in Germany that are lined with carbon blocks no cooling plates are used, and that shower cooling is employed on the hearth and bosh sections. While one of the authors was in Germany he was told that one furnace was being operated without even the shower cooling on the bosh section, though the hearth section was shower-cooled. In discussion of this interesting situation with a number of blast-furnace operators in this country, it was made clearly and promptly evident that shower cooling was very unpopular, probably because of its messiness and its ineffectiveness. Both of the causes for the dislike of shower coolings are reasonable ones. Shower cooling can be and frequently is messy, but the present cooling of blast furnaces leaves much to be desired on that score. Shower cooling is ineffective as compared with plate cooling, so far as its usefulness in keeping the bricks cool enough not to melt or fall to pieces is concerned. However, the introduction of carbon linings changes the situation. No one is concerned with keeping a carbon lining cool, for no temperature in the blast furnace has any effect on carbon, which is just as stable at 3000°F. as it is at 70°F. The only concern is for the shell-to keep it cool enough for safety and comfort and for that shower cooling is sufficient. Of course, with only the shell to cool, instead of the shell plus all the refractory material, much less water would be required, and the necessity for constant attention to the flow would be lessened, as the hundreds of inlets and outlets would be eliminated. Probably half of the water used in cooling a blast furnace is used for cooling the shaft and tuyeres and the remainder for the bosh and hearth sections. However, in view of the dislike of shower cooling in the United States, and particularly because at least one German blast furnace is operated with no cooling of the bosh section, thought was given to the possibility that a carbon-lined blast furnace might be operated without any cooling of the entire carbon-lined portion. For that reason a series of experiments was performed to determine what might be the temperature of the shell of a blast furnace protected by a carbon lining and operated under varying conditions up to a maximum inside temperature of 3000°F. EXPERIMENTAL PROCEDURE A schematic diagram of the experimental setup is shown in Fig. I and a photograph of the entire assembly in Fig. 2. The heating element was a carbon tube nominally 2 5/8 in. o.d. by 2 in. i.d. by 30 in., used as a resistor. Power was furnished by a 15-kva. transformer operating

Jan 1, 1941

By M. R. Hatfield, F. J. Vosburgh

In a recent article, it was shown that in the blast furnaces in Germany that are lined with carbon blocks no cooling plates are used, and that shower cooling is employed on the hearth and bosh sections. While one of the authors was in Germany he was told that one furnace was being operated without even the shower cooling on the bosh section, though the hearth section was shower-cooled. In discussion of this interesting situation with a number of blast-furnace operators in this country, it was made clearly and promptly evident that shower cooling was very unpopular, probably because of its messiness and its ineffectiveness. Both of the causes for the dislike of shower coolings are reasonable ones. Shower cooling can be and frequently is messy, but the present cooling of blast furnaces leaves much to be desired on that score. Shower cooling is ineffective as compared with plate cooling, so far as its usefulness in keeping the bricks cool enough not to melt or fall to pieces is concerned. However, the introduction of carbon linings changes the situation. No one is concerned with keeping a carbon lining cool, for no temperature in the blast furnace has any effect on carbon, which is just as stable at 3000°F. as it is at 70°F. The only concern is for the shell—to keep it cool enough for safety and comfort— and for that shower cooling is sufficient. Of course, with only the shell to cool, instead of the shell plus all the refractory material, much less water would be required, and the necessity for constant attention to the flow would be lessened, as the hundreds of inlets and outlets would be eliminated. Probably half of the water used in cooling a blast furnace is used for cooling the shaft and tuyeres and the remainder for the bosh and hearth sections. However, in view of the dislike of shower cooling in the United States, and particularly because at least one German blast furnace is operated with no cooling of the bosh section, thought was given to the possibility that a carbon-lined blast furnace might be operated without any cooling of the entire carbon-lined portion. For that reason a series of experiments was performed to determine what might be the temperature of the shell of a blast furnace protected by a carbon lining and operated under varying conditions up to a maximum inside temperature of 3000°F. Experimental Procedure A schematic diagram of the experimental setup is shown in Fig. I and a photograph of the entire assembly in Fig. 2. The heating element was a a tubc nominally 25/8 in. 0.d. by 2 in. i.d. by 30 in., used as a resistor. Power was furnished by a I5-kva. transformer operating

Jan 1, 1942

By E. W. McAllister

The decision of the California Oil Umpire's' office to accept well potentials established from subsurface-pressure data has brought to the attention of many operators for the first time the application of such data to production problems. This paper reviews the development and application of subsurface-pressure data in kettleman Hills, where these data have been used in production work since 1932. The Kettleman Hills field was discovered in October 1928. The first subsurface-pressure surveys were made early in 1932 and by the middle of 1933 the two major operators in the field were making routine pressure runs in thcir respective wells. Shortly therefter, these companies agreed to exchange pressure data, and later a third company entered into the agreement. This made it possible to analyze the effects upon the reservoir pressure of past production practices, which are discussed in the latter part of the report. It is interesting that many of the applications of subsurface-pressure data discussed herein were anticipated by C. L. Clark and C. B. Kimberlint in a report2 dated March 1933. PRODUCTIVITY Index In the majority of individual well problems involving the use of subsurface- pressure data, it is necessary to use a factor known as the "productivity index," which indicates the ability of a well to produce and represents the number of barrels of oil or oil and water per day that will enter the well bore for each pound per square inch pressure drop made opposite the producing interval of the well. The productivity index may be determined from pressure and production data for one or more rates of flow and a static or shut-in pressure survey or from production and pressure data for two or more rates of flow. Productivity indices may be based upon either net oil or total fluid production. All indices referred to in this report are based upon net oil. The value of the productivity index for Kettlcman Hills wells decreases generally with time and it is not uncommon for the index to vary in value at any specific time fur various rates of flow. The decline of the productivity index may be attributed partly to the loss of reservoir pressure. As the reservoir pressure decreases, gas originally in solution is released from the oil, congesting the flow of fluids through the formation and increasing the viscosity and surface tension of the oil; thus the flow resistance of the fluids through the formation is increased, resulting in a decrease of the productivity index. For convenient reference, the productivity indices for each well are plotted against time and a curve is drawn through the points showing the trend of the average index value. Plotted on Fig. I are index values for five

Jan 1, 1941

By W. A. West

One who attempts to collect and classify equilibrium data from various iron-alloy systems is soon struck with the absence of any quantitative theory that can serve as a general background against which to compare and contrast results from different systems, at different temperatures, and with different concentrations. It is not necessary to wait for a perfect theory; investigation of divergences of theory from observation may prove of great value in acquiring understanding of the subject. For example, one has only to think of Raoult's law as applied to aqueous solutions. The equations developed by Zener1 represent an effort to provide such a quantitative theoretical background, and it is therefore desirable to subject this theory to such tests as can be applied. The present article is intended to be an application of available tests, and may thus be considered as a supplement to Zener's paper. It is assumed that this paper is available to the reader. The equations make it possible to calculate the effect on the equilibrium concentration of one alloying element due to the presence of one or more other elements. In particular. they are intended to give, for alloy steels, the carbon concentrations in alpha and gamma phases in equilibrium with each other, and in gamma in equilibrium with cementite. They may, however, be modified for use for carbon-free alloys. A summary is given later of the equations used in analyzing the data in this paper, and the symbols are there defined. About 125 papers have been examined for experimental data suitable for this investigation. An effort was made to look up all available reports of ternary systems including iron and carbon, as well as similar systems of higher order. Supplementary material was also obtained from a number of binary systems. A few noncarbon ternary systems were also found to which these methods could be applied. A comparatively small proportion oi the papers read provided usable material. In many systems the number of quantitative observations made in the iron-rich region is extremely small, and the smoothed curves to be found in most published phase diagrams are entirely useless for quantitative treatment. This opinion is confirmed by the authors of the series on Alloys of Iron Research, whose remarks show clearly that they have no illusions as to the accuracy of many diagrams that they present. A further difficulty arises from the fact that these equations apply only to rather low percentages of alloying elements. The result is that at the lowest concentrations, where the best agreement might be hoped for, the errors of observation become relatively very large. The experimental difficulties in measurements of this kind of equilibrium are, of course, an old story.

Jan 1, 1947

By F. L. Robertson, C. H. Bacon, J. W. Till

A description is given of the development of a process for making low sulphur steel on furnaces fired with 2 1/2 pet sulphur oil. Slag and metal are analyzed at melt. Slag weight is estimated. A simple method for calculating necessary lime additions for making 0.025 and 0.035 pct sulphur steel is given. DURING the last 15 years John Summers & Sons have been confronted increasingly by the problem of producing a low sulphur steel from high sulphur materials. The principles adopted, the processes used, the data collected on a furnace specially set aside to study this problem, and speculation on future developments are dealt with in this paper. This study is limited to two melting shops which make sheet steel only, of the following analysis: C, 0.06 pct; Mn, 0.33; S, 0.04, 0.035, 0.03, and 0.025; and P, 0.02 and 0.015. All the processes described have reference to the manufacturing of this steel and are not necessarily applicable, without modification, to other steels. The raw materials used are given in Table I. Development of Process About 1934, Schenck's work on phosphorus was applied to frame quantitative rules for the removal of phosphorus, with great success. We could however, neither in our own work nor in the voluminous literature, find any assistance to frame quantitative furnace rules to remove sulphur. Perhaps, we should have persevered with Schenck's outstanding chapter on sulphur in The Physical Chemistry of Steelmaking, but we missed the importance of one (Ss) sentence on p. 478. "Evidently this ratio -------- is [S] the important quantity to be considered from the point of view of chemical reaction; it is clear that the sulphur content of the steel alone, as frequently given in the literature cannot suffice for judging the success of the reaction unless special details are given regarding the sulphur charge and the amount of slag."' We were not however very successful in getting values for Schenck's "n" that agreed with (S) arrived at by our direct analysis. [S] In addition to Schenck's work much attention was given to V value. The formula selected for V was: (SCaO) — 1.57 (2 P2O5) (S SiO2) After plotting many charges a curve was obtained, based upon the relationship between the percentage sulphur in the finished steel and V value, Fig. 1. For a long time this was used as standard with about a 60 to 70 pct success on producer-gas fired furnaces, if all uprising scrap was used and no bought scrap used. An inspection of this curve shows clearly that it is not a quantitative manufacturing process, and that it was not sure enough to go to the trouble and expense of doing stage analysis for P,O,,

Jan 1, 1952

By L. Kaufman

An equation is derived relating AF a", the difference in free energy between austenite and martensite, to temperature and composition in the iron-chrmnium and iron-chromium -nickel systems. This equation is used to calculate at M,for low-carbon stainless steels. A method for utilizing the energetic equations to calculate M, in stainless steels is suggested. In addition, an explanation is given for the anomalous effect of chromium in forming a y loop concurrent with the lowering of M, in iron-base alloys. It has been demonstrated that the effect of alloying elements on the Ms temperature is strongly dependent upon the influence of the alloying element on the thermodynamic properties of the y and a phases. Notwithstanding the fact that alloying elements affect the Ms temperature by changing the lattice parameters, elastic constants, and inter-facial energies of the a and y phases, their primary role is a thermodynamic one. Thermodynamic analyses have been presented for the iron-carbon'-4 and iron-nickele systems in which equations are derived for Fa and FY, the free energies of the b.c.c. (or b.c.t.) and f.c.c. phases. These equations, which can be obtained with the aid of the equilibrium diagrams, can be used to help predict the Ms vs composition curves. This paper deals with a calculation of the thermodynamic properties necessary to compute AFffLY for iron-chromium alloys. In view of the lack of direct information concerning the activity of chromium in the a and y phases of iron, the regular solution approximationa,g was utilized to bridge the gap. After the necessary equations were derived for the iron-chromium system they were used to calculate AFff— Y for stainless steels by combining them with the previous results obtained for iron-nickel alloys. The results of these calculations offer a means of rationalizing the anomalous behavior of chromium in iron-base alloys. The latter depends on the regular solution approximation in contrast to the explanation offered by zener , which is based upon the "magnetic specific heat effect." THERMODYNAMICS OF THE IRON-CHROMIUM SYSTEM If y represents the atomic fraction of chromium in an iron-chromium alloy, then the free energy of the b.c.c. phase Fa, the f.c.c. phase FY, and the difference in free energy between the f.c.c. and b.c.c. phases of the same composition are given through [3] and Fmy represent the free energies of mixing of the a and y phases; while @era -' and uFea 4Y represent the difference in free energy between f.c.c. and b.c.c. chromium and iron respectively. The values of AEFe0ff4Y in the temperature range between 0" and 900K ( .

Jan 1, 1960

By V.K. Zworykin

Throughout its development the science of electronics, like so many other branches of science and industry, has been indebted to the metallurgist. Metallurgy has provided the electronic engineer with conductors to furnish passage for electrons outside of his evacuated tubes: it has developed tungsten and tantalum wires for emitting electrons and various refractory metals and alloys suitable for electrodes, which receive them and guide them within the tube; finally it has supplied ferromagnetic materials both for shielding electronic apparatus from magnetic fields and for forming highly concentrated fields for deflecting electron . Today I hope to show you that electronics has not been altogether ungrateful for this assistance. More specifically, I wish to indicate the role that the electron microscope, a relatively recent product of electronic engineering, is playing even now in the study of metals. Every metallographer is aware that his standard metallographic microscope will not reveal structural detail involving separations smaller than a certain fraction —at the very best a tenth—of a micron. This limitation, he knows, is a consequence of the fact that the wave length of the light employed for forming the image has this order of magnitude. It is, thus, a property of all light microscopes. TO overcome it, a different imaging medium must be employed, The existence of such a medium became evident when it was demonstrated1 that electrons were affected by magnetic and electric fields with axial symmetry just as light is affected by glass lenses; these fields, or "electron lenses," curve the paths of electrons reaching them from an object located on the axis of symmetry in such a manner that, at some distance from the lens, a true image of the object is formed. Furthermore, although a wave length may . be ascribed to electron beams just as to light, this wave length is much shorter; for electrons accelerated through a difference of potential of 50 kilovolts, the wave length is only about one hundred-thousandth of that of visible light. Actually, the elcctron microscopes of today resolve detail one hundred times as fine as light microscopes; if the maximum useful magnification of the latter is taken to be a thousand, that of electron microscopes is one hundred thousand. The Electron Microscope Since electrons are readily scattered and absorbed by matter, specimens to be observed in the electron microscope must be prepared to be less than one micron in thickness; furthermore, the interior of the microscope must be carefully evacuated to prevent collisions between the clectrons and the molecules of the air. Finally, as already mentioned, the lenses are formed by axially symmetric magnetic or electric fields, and not by any material medium such as glass. Apart from these basic differences, the electron microscope closely

Jan 1, 1943

By V. K. Zworykin

Throughout its development the science of electronics, like so many other branches of science and industry, has been indebted to the metallurgist. Metallurgy has provided the electronic engineer with conductors to furnish passage for electrons outside of his evacuated tubes: it has developed tungsten and tantalum wires for emitting electrons and various refractory metals and alloys suitable for electrodes, which receive them and guide them within the tube; finally it has supplied ferromagnetic materials both for shielding electronic apparatus from magnetic fields and for forming highly concentrated fields for deflecting electron . Today I hope to show you that electronics has not been altogether ungrateful for this assistance. More specifically, I wish to indicate the role that the electron microscope, a relatively recent product of electronic engineering, is playing even now in the study of metals. Every metallographer is aware that his standard metallographic microscope will not reveal structural detail involving separations smaller than a certain fraction —at the very best a tenth—of a micron. This limitation, he knows, is a consequence of the fact that the wave length of the light employed for forming the image has this order of magnitude. It is, thus, a property of all light microscopes. TO overcome it, a different imaging medium must be employed, The existence of such a medium became evident when it was demonstrated1 that electrons were affected by magnetic and electric fields with axial symmetry just as light is affected by glass lenses; these fields, or "electron lenses," curve the paths of electrons reaching them from an object located on the axis of symmetry in such a manner that, at some distance from the lens, a true image of the object is formed. Furthermore, although a wave length may . be ascribed to electron beams just as to light, this wave length is much shorter; for electrons accelerated through a difference of potential of 50 kilovolts, the wave length is only about one hundred-thousandth of that of visible light. Actually, the elcctron microscopes of today resolve detail one hundred times as fine as light microscopes; if the maximum useful magnification of the latter is taken to be a thousand, that of electron microscopes is one hundred thousand. The Electron Microscope Since electrons are readily scattered and absorbed by matter, specimens to be observed in the electron microscope must be prepared to be less than one micron in thickness; furthermore, the interior of the microscope must be carefully evacuated to prevent collisions between the clectrons and the molecules of the air. Finally, as already mentioned, the lenses are formed by axially symmetric magnetic or electric fields, and not by any material medium such as glass. Apart from these basic differences, the electron microscope closely

Jan 1, 1943

By Fuad S. Maayeh, Robert J. Evans, Paul M. Yavorsky

A description and capabilities of the Mine Roof Simulator at the Pittsburgh Mining Technology Center is illustrated for testing longwall roof support equipment. This unique Mine Roof Simulator has the capacity to exert 3 million lbs. of compressive force vertically and 1.6 million lbs. of force horizontally to simulate loads on hydraulic supports typically found in longwall mining. The supports that undergo testing are instrumented with strain gauges and photoelastic coatings such that critically strained areas become readily apparent. These critically strained areas are redesigned or retrofitted with appropriate reinforcement and retested. A data base will be accumulated from several support designs that will lead to an optimized design that will have the potential to reduce downtime by malfunctions of supports and thus increase productivity. A typical test procedure and analysis is given for a two leg 350 ton shield along with a description for placement of strain gauges, displacement gauges, and hydraulic pressure monitors for critical sites.

Jan 1, 1982

IT is not very necessary for those who work ores to return the litharge to lead, because they use litharge in place of lead ore and they use it the more willingly when it still contains some trace of silver. For the cupeling hearth can never be so well made or so cleanly operated that some little bit of silver does not remain in it, and some particle of it is also necessary by its very nature. But for one who has to use very much lead at one time, like someone who smelts sweepings or cements, or for someone who wishes to bring his operations to a conclusion and withdraw his investment, it is possible to have the lead again. In order to do this, the litharge is taken and ground. Cupeling hearths are washed in addition to being ground. Then these powders are made into a paste by wetting them with salt water, and they are made into large

Jan 1, 1942

Reports from the Geological Survey, Department of the Interior, indicate that although considerable drilling has been clone in the state of Utah, no oil has been produced in commercial quantities. Sandstone saturated with asphalt and other hydrocarbon compounds and small showings of oil in wells at several places suggest that oil may be found, in commercial quantities where the rocks are favorable for oil accumulation. In some places the structure appears to be very favorable for the storage of oil which may probably be reached by drilling to a depth of 3000 to 4000 ft. It is admitted that this will be wildcat drilling for it is not known whether the unexposed rocks carry oil and there are no surface indications of oil. This entire subject is discussed in United States Geological Survey Bulletin No. 711-A, and most of the report will be found to be contrary to the claims that have recently been advanced for oil properties in Utah.

Jan 9, 1919

Plans for the fall meeting of the AIME, to be held in conjunction with the Centennial of Engineering -marking the 100th anniversary of the Society of Civil Engineers-indicate that the Chicago gathering will be one of the most significant in Institute history. Headquarters for the six divisions represented will be the Palmer House. Twenty technical sessions will be held from September 3 to 6, with papers of industry-wide impact to be presented. The papers will follow the theme of the celebration-a century of engineering progress. The MBD will start the ball rolling with morning and afternoon sessions Thursday, September 4. A luncheon also will be held. MBD has scheduled morning and afternoon sessions for the following day as well. MGGD, Iron and Steel, and the Coal Div., will hold sessions Friday afternoon. The Industrial Minerals Div. plans an executive meeting, 5 pm, Friday. Geology Subdivision is slated for morning and afternoon sessions Saturday. The Coal Div. will meet again Saturday morning.

Jan 1, 1952

The income of the Institute is derived from dues, subscriptions to MINING AND METALLURGY sale of publications. These sources are fortunately supplemented by the interest from invested funds now amounting to over $500,000, a considerable portion constituting endowments for especial purposes. Aside from the medal funds the principal endowments are the James Douglas Fund for support of the Library, the Rocky Mountain Fund and the Seeley W. Mudd Memorial Fund. The income from the two last named is available for the support of research and a variety of other purposes. It is allocated by the Board of Directors upon recommendation of standing. committees in each case. An active effort is being made to increase the endowments of the Institute, it being felt that unusual opportunities exist for research and public and professional service through the organization and at a minimum of expense. J. V. W. Reynders is chairman of the Endowment Committee.

Jan 1, 1929

By A. E. Himebaugh

A SEMI-AUTOMATIC hoist has been installed at the 2966 station of the Copper Queen mine, since neither the bulk of supplies handled nor the number of men engaged in developing the 3100 level justifies the constant attendance of two cagers and two hoist operators. The connecting service shaft between the 2966 and 3100 levels is actually a two-compartment raise. Below the 2966 level the shaft is 7x13 ft-slightly oversize to permit downcast ventilation and provide space for the 16-conductor flexible control cable. The raise extends 52 ft above the 2966 level for a 3-ft diam head sheave. Another 3-ft sheave is mounted as an idler between the hoist and head sheave, eliminating the need for an inclined cableway. The main compartment serves as a cageway; the other compartment provides a manway and space for service lines. Since vertical travel is limited, rope speed is of minor importance.

Jan 5, 1958

POSITIONS VACANT (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons.) General manager .for a pyrite mine in Virginia, with experience in the mining and particularly in the washing of pyrite, required. Salary at start, $250 per month with perquisites. No. 28. Assayer and cyanide man for a Costa Rica plant. Salary $100. No. 29. Mine manager to develop gold-mining property in Witwatersrand, Transvaal. Salary £2,000 to £4,000, according to the experience and ability of the engineer. No. 31. Mine superintendent for a mine in Arizona containing copper, gold, silver ore. Will have entire charge of operation and development. Salary to start, $200 per month with perquisites. No. 32. .Mining engineer to make complete report and suggest necessary machinery for development and operation of a placer property; also to examine a copper property. Both properties in Peru, South America. No. 34.

Jan 4, 1915

By W. M. Corse

W. M. CORSE,?Mansfield, Ohio.-The conservation of tin, in view of the shipping situation; is one of great importance. Several methods of conservation can be employed: 1. Reduction of the amount of tin in an alloy or compound. 2. Substitution of an entirely different metal or compound for tin. 3. A combination of the first and second methods. The second method is the one that I wish to discuss. Metallic aluminum has been known for a long time, and its use in copper alloys was discovered about 1855 by Lord Percy. The high cost of production of metallic aluminum retarded its commercial development, and it was not until the discovery of the electrochemical processes for its production that it came to be known as a common metal. I have been particularly interested, for the past few years, in working with the alloy known as aluminum bronze, which is usually composed of approximately 90 parts of copper and 10 parts of aluminum, by weight.

Jan 12, 1918

By W. R. Wardner

During 1928 low prices in the East greatly restricted the Atlantic market for California petroleum. The situation was made difficult by only partial control of production. The month of December is estimated in the figures presented here and it is hoped that the differences in the final figures will be immaterial. Daily averages are used throughout. Production Daily average crude production for 1928 was 633,942 bbl., very little more than 1927. Natural gasoline production was 35,453 bbl. daily and the supply (crude and natural gasoline) was 669,395 bbl. However, potential supply was 785,621 bbl. daily, 47,436 more than that of 1927. This is accounted for by more production being shut in so that 116,000 bbl. daily was conserved in 1928 which would otherwise have been produced. Fig. 1 shows production by months for 1928. It will be noticed that while crude production held fairly uniform from January to October, the

Jan 1, 1929

By B. K. Mozumdar

This paper describes the development and application of a dynamic simulation model of ground movement in an underground mine. Ground movement and related stress distributions with or without stowing are computed as the mining face advances. Pressure profiles plotted for different face positions indicate the presence of a front abutment with a maximum value of four times the original ground pressure but no back abutment in the gob. The surface strain is considerably reduced with increase in packing density in the gob up to a certain value. Beyond this value, the reduction in the strain is minimal, indicating an economic level of packing. As a result of model experiments with different physical systems and geological parameters, it has been concluded that when one of the coordinates for the subsidence and the strain curves is made dimensionless in terms of the critical width, the relationship will hold true for all physical situations. This was in agreement with the NCB observations for different panel lengths.

Jan 1, 1977

By B. Stoughton, H. O. Hofman

Before examining a fire-clay in the labori~tory for its resistance to heat or to fluxes, the sample is always ground to an impalpable powder. But when the clay is actually used for the manufacture of bricka, blocks, pots, etc., it is not ground to a uniform size, the particles varying from coarse grains to the finest slimes. The natural inference is that the tests with finely-ground substances mill give lower results than if the materials are tested just as they are going to be used. The, following experiments were made to find out how far this inference is justified. The method employed for fusion was Seger's direct method,* and, for fluxing, the modified Bischof method, described in the paper on that subject presented at the present meeting, The first question to be decided was, how large the test-cones ought to be made, to include representative proportions of the diflerentrsized particles colnposing the mixture. This was subjected to a screenanalysis with the following results :

Jan 1, 1899

By H. Maleki

Gob pressure measurements were made in a Western U. S. coal mine as part of a long-term program to evaluate cave progress and to determine the influence of geological discontinuities on caving conditions, load transfer, and resulting instabilities. Gloetzl cells were selected for the measurements due to their simple, robust construction and a history of being able to monitor pressures in a broken medium. A methodology was developed for the successful installation and protection of the cells and hydraulic lines in the gob as the face retreated. The measurements indicated a cave progress controlled by the frequency of major faults. The pressure-mining progress profile was compared to those observed in other parts of the world. It was concluded that the significant differences in profiles was caused by the thick-bedded strata, the existence of high lateral stresses, and the spacing between faults. Recommendations are given for future applications of Gloetzl cells for gob pressure measurements.

Jan 1, 1984