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By Thomas Fraser, Abreu Alvaro

THE work described in this paper was carried out under the sponsorship of the Foreign Economics Administration and in cooperation with the Departamento Nacionál da Produção Mineral, Rio de Janeiro. The project was undertaken to obtain complete data on the variations in washability of coal to be used for coke manufacture in the steel industry and to determine the economy of preliminary hand-sorting operations. The coal-producing industry of Brazil is in that pioneering stage in which operat¬ing practices and methods are just being developed. Increased wartime demand for fuel, coincident with a drastic curtailment of foreign supplies due to lack of shipping facilities, has put a tremendous pressure on the national industry to furnish more coal. Under this incentive, production facilities are being expanded and new methods of operation are being tested. Such changes are being developed both by improvement of existing methods that originated in the field and by adaptation and modification of methods introduced from the United States and Europe. These mining condi¬tions and mining practices in Brazil are typical of what the American mining engineer will find in many instances when he goes pioneering into the developing coal fields of the Southern Hemisphere. The producing coal fields of Brazil are all in the southern states of that country. The coal measures are in a band roughly paralleling the coast and extending in a generally southwesterly direction from northern São Paulo through the states of Paraná, Santa Catarina and Rio Grande do Sul to near the Uruguayan border in the vicinity of Bajé. The accompanying map1 (Fig. I shows the general location of these fields and also the principal routes of movement of both national and imported coal in a late pre-war year (1940). Statistical data on production by states up -to that year are given in Table I. Rio Grande do Sul is still the largest producer among the coal states; but wartime

Jan 1, 1946

By William H. Kobbé

THE CHAIRMAN (M. L. REQUA, San Francisco, Cal.).-We have had in California a great deal of trouble from the breaking. off and collapsing of well casings from shifting sand, and it is quite true with us as indicated in the paper, that no casing has been found sufficiently strong to withstand that. I know of wells in which casing that has not been in the hole over 2 or 3 days has collapsed and when that casing has, been pulled out it has been just as flat as your hand. I am also familiar with swelling bed rock in the gold drift mining ground of California. It does swell and keeps on swelling and never seems to stop. Just as long as tunnels are kept open in that kind of material there has to be a gang going through the tunnel constantly cutting out and easing up. They have put in timbers 24 in. in diameter in an effort to hold that kind of ground and it has always filled. The only way to succeed is to keep a gang of men busy all the time cutting out and easing down as it squeezes in. C. NARAMORE, Washington, D. C.-My experience has been very similar to yours in, the same field in the matter of breaking off of casing. I had charge of one well, in which I put in reënforced casing, anchored it in place and got 1 day's production, 150 bbl., out of it. The following morning my lease foreman telephoned that it had broken off. I thought at that time we would have more evidence, so I drove out to the well without ordering a new shoe joint. It had been customary to merely start from town with a new shoe joint, pull the pipe, take off the crooked bottom joint, start the casing back and sometimes never touch any iron (lost casing)- when redrilling the well. Where the flattened joints went

Jan 4, 1917

By Robert W. Hunt

I have frequently stated that while the chemical composition of steel is important, yet even greater importance is connected with the mechanical and heat treatment of the metal. During the past year I encountered such a positive example of that fact that I deem it worth putting upon record. A prominent railway system divided an order for open-hearth steel rails between two steel works, both of which are under the control of the same corporation; giving to one about 18,000 tons, and to the other 7,500 tons of the same section and to be made under the same specifications. The rolling results obtained in the two mills varied so widely that a study of the figures is intensely interesting and serves to illustrate the advantages obtained by carefu1 ingot casting, and, quite as pertinently, the possible benefits of careful subsequent heating and rolling with moderate reductions in the rolling process. The smaller order was rolled complete in four installments during the same months that the larger order was being made in six separate installments; but, to permit of exact comparisons, the totals of the four installments (completing the order with the mill which I will call A) are given with the totals of the first four installments of the larger order, made by the mill designated as B. These rolling results are: Mill A. Mill B. Number of rollings,............................................ 4 4 Total number of rails rolled................................ 18,278 27,832 Percentage of rails cut to short lengths because of flaws near ends, etc......................................... 0.7 7.6 Percentage of rails made second quality for flaws, etc. 0.9 6.3 Percentage of rails scrapped for flaws, etc............... 0.6 4.5 Percentage of rails scrapped for failure at drop test... none 3.4 It should be stated that the figures given above cover all the reasons for putting the rails in the classes stated, Thus a part of the percentage of rails cut to short lengths may have been

Jan 1, 1914

By Cyril S. Taylor, Junius D. Edwards

Magnesium is the lightest metal used for structural purposes, for which reason perhaps more than usual interest is attached to measurements of its density. Although the density of solid magnesium has been det,ermined frequently, no measurements of the density of the liquid metal are available. Because of unusual experimental difficulties in measuring the density of the liquid, only a limited number of measurements of good precision were secured. The results, especially the value for the crystallization shrinkage, are of great interest in connection with the casting of the metal. A number of samples for these measurements were made available through the courtesy of the American Magnesium Corp. They were in the form of extruded bars 3/8 in- in diameter and several were of exceptional purity, as indicated by careful analyses. Table 1 gives the density values (at 20" C.) for magnesium of varying degrees of purity. The density was measured at room temperature by comparison of the weight in air, and when immersed in distilled water. The necessary buoyancy corrections were applied, so that the density could be expressed in absolute measure—grams per milliliter. The effect of the buoyancy of the immersed suspension and the surface-tension pull of the water upon the suspension were eliminated from the results by a preliminary weighing of the suspension immersed to the working depth. Great care was necessary to prevent the introduction of a significant error by the formation of gas bubbles upon the clean magnesium surfaces; these are sometimes very minute and easily escape observation. They may be detached by raising the specimen from the water and again immersing; this should be done just prior to completing the weighing. Their formation may be almost entirely prevented during a measurement by previously immersing the specimen in a solution of paraffin in petroleum ether. The thin film of paraffin remaining after the evaporation of the solvent prevents wetting of the magnesium surface by the water. In one such determination, the paraffin coating on a 22-gm. Specimen

Jan 1, 1923

Discussion of the paper of Ernest Stütz, presented at the New York Meeting, October, 1913, and printed in Bulletin No. 79, July, 1913, pp. 1257 to 1265. H. 0. HOFMAN, Boston, Mass.:-I have hunted in vain for a figure which gives a dehydration temperature of cement. I was wondering if Mr. Stütz had a figure of that kind. E. STÜTZ :-No, I am afraid I have not. H. 0. HOFMAN :-I believe some figures have been published that cement disintegrates at 400° or 500° C. It seems tome a very low temperature. Mr. Stütz just made the statement that the disintegration of this briquette begins at the temperature at which the briquette begins to sinter. E. STÜTZ :-Above the sintering point. H. 0. HOFMAN :-The sintering point would be about 1,200° C. E. STÜTZ :-Yes, roughly speaking. I am afraid I have no information about the exact degree of dehydration. H. O. HOFMAN :-I have looked a great deal for such a figure and I have not been able to obtain it. Professor Howe says I might have tried myself. But my interests were directed in another line; although-that is, perhaps, a good suggestion. CHAIRMAN RICHARDS:-Is not Portland cement sometimes used for the test in a cupellation furnace and a drying-out furnace ? H. O. HOFMAN :-Yes, it is used, but that is a higher temperature, of course. But I have been trying to get a figure as to where it loses all its water. I understand it begins to lose water at 500° C. But there are different silicates or hydrosilicates in the cement, so that one would have four or five or sit figures to show the different stages at which the cement loses its water. CHAIRMAN RICHARDS :-I would ask whether the use of this material in blast furnaces has shown increased capacity of furnace or decreased consumption of fuel.

Jan 12, 1913

By H. C. Kenny

The annealing or softening temperature of cold-worked copper is appreciably increased by almost unbelievably small amounts of silver. As indicated by some data in this paper, the softening temperature of high-conductivity, tough-pitch copper may be increased from 200" to 350" C. by the addition of only 15 oz. per ton (0.052 per cent) of that element. Because it has this higher annealing temperature as compared with the silver-free metal, silver-bearing copper finds considerable use in industry. For example, when hard-rolled copper is used in operations that involve soldering or tinning, silver-bearing copper insures against loss of strength, whereas silver-free copper becomes "dead soft." Yet—though several investigators, beginning with Caesar and Gernerl in 1916, have shown that small amounts of silver do definitely raise the softening temperature of copper—data are lacking on the problem: What is the specific influence of different amounts of silver on this temperature? It was to help in filling this gap in the knowledge of what might be termed "alloy coppers" that the data given herein were obtained. The softening of cold-worked copper depends, of course, on a number of factors, of which the composition of the material is only one. Other highly important factors are the degree to which the material is cold-worked and the time it is held at the annealing temperature. The method of cold working and the grain size of the metal produced are also significant. All these variables were taken into account in the investigation reported here, and the influence of silver on the electrical conductivity and on the working was also considered. The coppers used in the softening tests were Lake coppers melted and cast by the Calumet and Hecla Consolidated Copper Co. The ires were fabricated by the Roebling Wire Co. and the sheets were rolled at the Battelle Memorial Institute. Partial analyses of some of the coppers are listed in Table 1, with their electrical conductivities.

Jan 1, 1934

By Leonard B. Griffiths

In a recent communication, Smith and Wood described some results of 800°C compression/creep tests on WC-12 wt pct Co alloys in which plastic flow in the WC particles was believed to have occurred. The deformation observed in the WC particles was found to be a function of the rate of loading. The authors suggested that their data constituted support for the Ansell6-Lenel theory of yielding in dispersion-strengthened alloys. I do not agree with this interpretation since the Ansell-Lenel theory does not apply to the type of alloy in question. In this alloy, the dispersoid is present to the extent of about 80 vol pct. Even where there is no continuous skeleton, which apparently is the case in this instance, the simple fact is that nearly all of the load is carried elastically by the stronger material (wc).7 The constraint imposed upon the matrix, by virtue of the differences in Young's modulii and Poissons ratios, severely limits the stress level to which it may be subjected (assuming that the interfaces remain intact). If one allows for the constraint and then performs the same computation as in Smith and Wood, one finds that the stress on a WC particle is about 4 x 105 psi. This is about 21/2 times lower than the predicted fracture stress for WC. I would completely agree with the final paragraph of Smith and Wood, namely, that loading rate is of considerable significance. However. a more likely interpretation of their data is, I submit, that in the absence of stress relaxation (by secondary slip or climb) those WC-Co interfaces subjected to a normal tensile stress begin to fail. Once this occurs, the stress distribution will change rapidly and "premature" fracture of the WC then becomes quite probable. Tne serrated edges shown in Fig. 1 may very well be fine, interface fissures.

Jan 1, 1970

By Junius D. Edwards, Cyril S. Taylor

Magnesium is the lightest metal used for structural purposes, for which reason perhaps more than usual interest is attached to measurements of its density. Although the density of solid magnesium has been det,ermined frequently, no measurements of the density of the liquid metal are available. Because of unusual experimental difficulties in measuring the density of the liquid, only a limited number of measurements of good precision were secured. The results, especially the value for the crystallization shrinkage, are of great interest in connection with the casting of the metal. A number of samples for these measurements were made available through the courtesy of the American Magnesium Corp. They were in the form of extruded bars 3/8 in- in diameter and several were of exceptional purity, as indicated by careful analyses. Table 1 gives the density values (at 20" C.) for magnesium of varying degrees of purity. The density was measured at room temperature by comparison of the weight in air, and when immersed in distilled water. The necessary buoyancy corrections were applied, so that the density could be expressed in absolute measure—grams per milliliter. The effect of the buoyancy of the immersed suspension and the surface-tension pull of the water upon the suspension were eliminated from the results by a preliminary weighing of the suspension immersed to the working depth. Great care was necessary to prevent the introduction of a significant error by the formation of gas bubbles upon the clean magnesium surfaces; these are sometimes very minute and easily escape observation. They may be detached by raising the specimen from the water and again immersing; this should be done just prior to completing the weighing. Their formation may be almost entirely prevented during a measurement by previously immersing the specimen in a solution of paraffin in petroleum ether. The thin film of paraffin remaining after the evaporation of the solvent prevents wetting of the magnesium surface by the water. In one such determination, the paraffin coating on a 22-gm. Specimen

Jan 1, 1923

By Gram Curtis

The apparatus described below for the handling of plates upon their delivery from the rolls, embodies features believed to be of interest to those contemplating the building of new plate-mills, and also to such owners of existing mills as may be considering the improvement of their works. The points to which attention is called are the small space required for the finishing-end of the mill, and consequently the very moderate size of the building for the amount of plates handled; the directness and ease of manipulation, and therefore the mall amount of labor required; the distribution of plates; the facilities and time allowed for their cooling. These, together with other features of detail and general arrangement scarcely less important, will become apparent when the descriptions and illustrations herewith given are understood. As these devices deal with the finishing of the plates only, they may be added to any plate-train when the floor-space and the building are large enough to permit their introduction; and it will be obvious that the features of this method, more or less modified, are applicable to any existing mill. Figs. 1 and 2 show a three-high 32-and 19- by 120-inch Lauth mill, with hydraulic lifting-tables, served by four heating-furnaces, with hydraulic cranes for charging and drawing. Upon leaving the rolls, the plate is allowed to rest with its forward edge projecting somewhat beyond the end of the catcher's table. Here it is seized by the automatic tongs, A, suspended from a buggy travelling in the overhead trough, B, and actuated by the hydraulic cylinder, C. These tongs are operated by a boy, who stands several feet from the heated plate, and controls the long light handle, D, shown in the plan, Fig. I. His duty is merely to advance the tongs by means of .the hydrulic cylinder, C, to raise or

Jan 1, 1892

By Arthur E. Hall

Tax operation of "softening" in lead refining is designed, as the word implies, to separate from the bulk of the lead the elements that tend to make lead hard. These elements, which invariably are present in argentiferous lead, interfere with the desilverization, and must be almost entirely absent in refined desilverized lead. They are mainly copper, antimony, arsenic and tin. The properties utilized in accomplishing this separation are the low solubility of copper or copper sulphide in lead at its freezing-point temperature, and the greater and selective affinity for oxygen of the other elements at temperatures of the order of 700° to 900' C., or, in the prcsence of sufficient, alkali, at a temperature of about 500' C. The major problems of softening lead bullion lie in the necessary subsequent treatment of the by-products of the primary operation, which contain, either chemically or mechanically, lead or reagents that must be isolated for market or re-use. Therefore an important objective of the primary operation must be the highest practicable concentration of these elements in the by-products. Within the past three decades, during which the writer has been engaged in lead refining, the technique of softening lead bullion has had as many variations as there were lead refineries. This was the result of the variation in composition and character of lead bullion recived. The writer has received for refining shipments of lead bullion varying as widely as indicated by the following table: Sb, Per CEnt As. Per Cent Sn, Per Cent Cu. Per Cent Ag. Oz. per Ton 1.00 0.05 nil 0.05 70 0.50 2.50 2.00 0.50 200 3.50 0.50 nil 0.30 350 At times these have been received uniformly and at other times irregularly with a variation from week to week as wide as those shown. Under such conditions, establishment of a universal softening technique presented many problems. Such variations existed because refinery tolls too often were based on a ton of bullion, whatever its composition, and

Jan 1, 1937

By A. B. Kinzel

SINCE the exposition of the behavior of certain iron alloys by Sykes1 involving the existence of an austenite loop and the discovery of such a loop in the chrome iron system by Bain,2 there has been much conjecture both on his part and on the part of metallurgists in general as to the exact shape and location of this loop. In previous work commercial steel has been used and the microscope has been employed to locate the critical points so that the position of the loop has been quite approximate. Numerous attempts have been made to measure the critical points of the carbon-free alloys but all of these for one reason or another have failed. A satisfactory method for studying these phenomena is presented here. MATERIAL The first difficulty in this study was to obtain pure chromium-iron alloys. This has been overcome by melting in a vacuum electrolytic Eton and chromium analyzing 99.84 Cr, Fe and C. A pure magnesite crucible was used and the melt allowed to solidify in the crucible. A typical analysis is chromium, 10.10 per cent., carbon, 0.006 per cent., silicon and manganese nil. To overcome the problem presented by segregation, ingots were made into wire 0.04 in, in diameter. This was accomplished by hand-forging the ingots into rods, using an oxyhydrogen flame for heating, in order to avoid carbon. Subsequently the rods were swaged to wire, the heating being carried out in hydrogen. Thus local segregation was eliminated although differences in analysis between portions 50 ft. apart were noted. An electric-resistance method was first tried to determine the critical points, but due to the physical defects in the wire this failed. Bain had previously shown the presence or absence of critical points in a qualitative way by observing the sag in a catenary. The author has devised the following method which gives an accurate determination of the critical points from expansion-temperature curves of suspended wire, a special telescopic dilatometer being used for the purpose.

Jan 1, 1928

By H. M. Wolflin

SOMEWHAT more than a year ago the writer collected some extensive notes on metal-mine fires and a paper on metal-mine fire prevention and fighting, a summary of these notes, was hastily pre-pared, with the assistance of G. Chester Brown, chief mining engineer, Industrial Accident Commission for the National Safety Council meeting. This summary, which is admittedly incomplete, is submitted in the hope that it will evoke some discussion that may result in a reduction in metal-mine fire hazard along the line. To accomplish such a reduction does not require the application of complicated scien-tific data. The use of just a little care, a small amount of thoughtfulness and a bit of common sense will work wonders. UNDERGROUND FIRE FIGHTING There may be some interest in a short list of con-clusions of a rather general nature that were reached in connection with some recent mine-fire fighting opera-tions. No effort has been made to cover the field; the items have been jotted down loosely, and very hastily, in the order in which they occurred to the writer. Originality is claimed for, only a few of them. 1. Temperature readings and analyses of mine-air samples, systematically taken, are invaluable aids to effective metal-mine fire fighting and recovery opera-tions. The analysis of the return-air samples fre-quently gives a surprisingly accurate indication of conditions existing underground. 2. Employees must be thoroughly trained in the use, of mine rescue apparatus, because a relatively slight difference in the amount of training makes a vast difference in the amount of work they can per-form under oxygen. In general, slender, wiry men make better apparatus men than those of heavy, more muscular physique, although there are frequent excep-tions to any such general statement. 3: Surprisingly high temperatures, up to 165° F. or 170° F. pan be endured for short periods by wearers of mine rescue apparatus if the air is dry, but lower temperatures, 135° to 140° F. are almost unbearable if the air is very moist.

Jan 2, 1922

By A. M. Starfield

The study of strain waves in rock over the past decade has, for the most part, been an investigation related, but not applied, to rock blasting; the design of rock blasts has proceeded on a basis that is independent of strain wave research. This duality is reflected in the paper by Dr. Clark.1 While the greater part of the paper is devoted to a discussion of spherical waves in elastic and visco-elastic media, it is in an entirely unrelated section, the section on scaling and cratering, that the practical approach to rock blasting is found. Work done by the U. S. Bureau of Mines, as described in the paper by Duvall, Atchison, and Fogelson,2 has established a correlation between crater dimensions and the peak compressive strain in the rock. Strain wave measurements have thus been used to compare explosives but have not, as yet, been applied to the planning of a production round once an explosive has been selected. The optimum burden, for instance, is still determined either by experience, empirical formulae (e.g. that of Langefors 3), or a cratering experiment and the theory that has been developed around that proposed by Livingston.4 Even then there is some ambiguity in applying deductions from short, concentrated explosive charges to the long charges often used in practice (although Bauer 5 reports doing this with considerable success) and wave theory has until recently thrown no light on this problem, being confined, with only a few exceptions, to spherical charges. The hesitation in applying strain wave theory has probably been due to two questions that have not been answered satisfactorily: just how important is the strain wave in rock breakage, and if it is important, under what conditions will the wave break rock? This paper is an attempt to answer the first question, to avoid the second question by an admittedly oversimplified assumption, and then to investigate the implications of this assumption for blasting with long cylindrical charges.

Jan 1, 1967

By Roy Neal

THERE are two main sources of the water that floods productive oil or gas sands. The water may rise from the lower depths of the producing stratum, or it may come from beds above or below the oil-bearing formation. Usually the recovery of oil is decreased by water entering the oil sands, and most oil-field waters, especially those of deep wells, tend to foster the formation of an emulsion, which is expensive to treat. This paper deals with a method of distinguishing between waters that encroach upon oil-bearing, beds from sources in the same stratum and waters .that reach the oil sands from horizons above. In order to remedy effectually water difficulties in oil and gas wells, it is absolutely necessary to determine the source of the invading water. Sometimes evidence such as the structural relations between the strata penetrated by neighboring wells and those found in the well under investigation is not adequate; also, data from drill logs and well records, from mechanical tests made on the wells by plugs, testers, drilling tools, etc., and from tests by chemical indicators such as eosin and Venetian red, may he unsatisfactory, for such data may fail to locate the source of the infiltrating waters. As a resort in such cases, the application of chemical analyses, that is, the comparison of an analysis of the water in, question with that of typical waters from the various water horizons in that particular district, has in certain instances proved of value. This method has been used to advantage in the Westside Coalinga field of California, where the source of water may be fairly definitely determined from its composition. The chief conclusions concerning the chemistry of the oil-field waters in California by G. S. Rogers1 are: "Oil-field water is not necessarily salty, as is generally believed, and may not be even slightly salty to the taste. The degree of concentration of chloride in such water is governed primarily by local conditions and is not affected by the position

Jan 1, 1919

By Douglas Bunting

IN THE anthracite fields of Pennsylvania, mine fires occur with more or less regularity and their existence is an ever-present hazard in coal mining. In all probability 90 per cent. of the mine fires can be ascribed directly or indirectly to the ordinary miner's open lamp. Other causes may be smoking, electrical installations, gas explosions, gas feeders, and the communication of fire to the outcrops from ash dumps, culm banks, timber and brush fires. Fires in pump rooms, engine rooms, and barns have been largely eliminated as a result of the Act of .Assembly, approved June 15, 1911, which provides that all inside buildings, including engine rooms, pump rooms, barns etc. shall be constructed of incombustible materials. Smoking of pipes, cigars, and cigarettes should be prohibited in the mines and too much care cannot be exercised in preventing fires by enforcing all rules designed for that purpose. Mine fires that involve underground fighting are invariably dangerous, and all fires, irrespective of the method pursued in extinguishing them, involve property loss and expense. Each fire generally presents a more or less original problem, dependent on the particular conditions. Generally mine fires may be divided into two classes: Those occurring in inaccessible workings and those occurring in accessible workings. The methods pursued in extinguishing or controlling mine fires are as follows: (1) direct attack, (2) smothering by sealing, (3) flushing with silt or other solids, (4) flooding with water, (5) cutting off, (6) surrounding with incombustible materials, (7) digging out by stripping from the surface. Most fires are extinguished in their incipiency by direct attack and failure to extinguish by this method is due to late discovery, lack of water, and facilities for fighting, or improper procedure in the initial attack. Should the method first pursued be unsuccessful, careful consideration should be given in determining next the method to be adopted; then the work should be carried on as rapidly as possible and under the supervision f the most competent persons. Materials and supplies should be fur-

Jan 9, 1921

By J. T. Hayward

Studies of the forces and conditions governing the recovery of petroleum from natural reservoirs indicate that a low gas-oil ratio increases ultimate recovery, retards the encroachment of water and tends to reduce lifting costs. Methods for controlling and reducing gas-oil ratios in producing wells consequently have been given considerable attention during the past few years. However, during this same period, the production from wells in nearly all fields has been fixed by proration agreements and it is the opinion of the writer that where a well is required to produce steadily at a predetermined rate, less than its "potential" or maximum capacity, the gas-oil ratio will depend only upon the rate of production, and will be independent of the method of production and of the design of equipment in the well. If no change in the rate of production is contemplated, efforts directed to improving the gas-oil ratio by altering the diameter of the flow string, changing the position of the choke, assisting the flow with gas-lift or pump, etc., will be unsuccessful. This viewpoint is not new. It was presented by H. N. Marsh and B. H. Robinson in 1929,' but it has not been generally accepted. Although engineers believe that the rate of withdrawal and not the equip ment used governs the water-oil ratio, a similar opinion regarding the gas-oil ratio is not so commonly admitted. The rates of flow of oil and gas into the base of an oil well depend upon the following conditions: 1. The characterist-ics of the oil and gas. 2. The characteristics of the underground reservoir. 3. Temperature and pressure conditions in the reservoir. 4. The back-pressure held against the face of the sand. In operating a well, the only one of these conditions over which control may be exercised through operating procedure and the use of equipment above the sand is the back-pressure at the face of the sand. Strictly speaking, the back-pressure varies over the face of the sand, owing

Jan 1, 1932

By D. Harrington

Efficient ventilation of metal mines consists in having such complete control of air currents that there is always supplied at placcs where men work sufficient moving air to allow working at maximum capacity without injury to health; and in case of underground fire or of surface fire in the vicinity of mine openings, underground air currents may be quickly reversed if desired, or air may be sent into or excluded from any region and fire fumes confined to only part of the mine workings, instead of penetrating practically the entire mine. Health and safety of workers in mines as well as proper safeguarding and operating efficiency of mining properties are so intimately associated with proper ventilation of mines (both coal and metal) that they are inseparable, yet ventilation is only too frequently neglected, especial1y in metal mines. The metalliferous operator, generally not confronted with inflammable gas or explosive dust which so frequently force ventilation of coal mines, usually disregards air supply altogether except such as may be obtained from compressed air; and generally, even when attention is given to metal-mine ventilation, the air currents rarely are found where they are needed, namely, the working places, especially the working faces. After several years' study of miners' consumption, the writer is convinced that long continued breathing of air impregnated with large quantities of any kind of finely divided dust, such as is found in a large number of the working places of our mines, will ultimately produce some respiratory disease, whether it be asthma, bronchitis, or phthisis; and the progress of these diseases is hastened if there are also present high temperatures, high humidities, or harmful gases or if there is present (and allowed to remain to be breathed) large quantities of the finely divided dust when air temperatures are low, hence favorable to maximum performance of work with accompanied maximum breathing into the respiratory passages of the harmful material. It is generally accepted

Jan 1, 1923

CONTENTS PAGE THOENEN, J. R.-Limestone Production as a Mining Problem. Discussed by Oliver Bowles, J. T. Singewald, S. R. Russell 1 GRIGGS, C. C.-Engineering in Limestone Production. Discussed by W. C. Phalen, John Rice, Samuel M. Shallcross, Oliver Bowles, Nathan C. Rockwood, George Milliron 2 WILDER, FRANK A.-Rotary Calciners for Gypsum. Discussed by L. K. Arm-strong 9 PORTER, JOHN J.-Manufacturing Problems of Cement Industry. Discussed by Samuel M. Shallcross 9 KIRKHAM, VIRGIL R. D.-Phosphate Deposits of Idaho and Their Relation to the World Supply. Discussed by F. A. Wilder, S. L. Willis, G. R. Mansfield, R. W. Stone, L. K. Armstrong 9 Limestone Production as a Mining Problem Discussion of the paper of J. R. THOENEN, presented at the New York Meeting, February, 1925, and issued, as Paper 1417-H, with MINING AND METALLURGY, February, 1925. OLIVER BOWLES, New Brunswick, N. J.-I am so thoroughly convinced of the growing importance of underground work in the production of limestone that I had the author make a detailed study of limestone mining for the Bureau of Mines and prepare a report on the principles of limestone mining. Many limestone operators, long accustomed to open¬pit work, are being forced to mining. About 6 months ago I thought there were twenty-five or thirty underground limestone operations in the United States but the author has been finding new ones until his list now runs nearer sixty. Some of these are very extensive; one at least has 4 ½ miles of underground workings. There is an ever-expanding field for the engineer in the operation of limestone mines and quarries. Some of the larger companies realize the need of skilled engineering advice, but many of the companies regard the engineer as an unnecessary expense. Although almost every metal mine, even those handling only a few hundred tons of ore per month, employs a mining engineer, many limestone operations ten times as large employ no mining engineers. Few mining engineers are at all familiar

Jan 6, 1925

By William Emmons

THE problem of the metalliferous veins has always been an outstanding one in the science of ore deposits. In recent years interest has been stimulated by Spurr, who maintains that veins have consolidated from magmas that have densities as great as the densities of ordinary rocks. Lindgren published a noteworthy paper1 in 1926, in which he supports the theory that veins are deposited chiefly by hot waters. Lindgren's paper was discussed by Singewald, Spurr, Kemp, Anderson, Colony, Bateman, Porter and others. The discussion, in the main, was centered on the interpretation of fragments that are included in veins. This paper also treats the problems of fragments in veins and includes a reply to a review by Spurr2 of a bulletin by Larsen, and myself published by the United States Geological Survey on the geology and ore deposits of Creede, Colorado. Mineral veins containing fragments of the wall rock are common. At many places the fragments are completely, isolated, one from the other, and are entirely surrounded by vein matter. It has been stated that the vein matter around the fragments was heavier than the fragments and that the latter were floated in a magma. J. E. Spurr, who is the leading advocate of this hypothesis,4 urges that normal mineral veins were deposited by solutions heavy enough to float fragments of the country rock, and it is mainly on this relation that he bases his theory that veins are deposited by solidification of magmas. If it can be shown that vein-forming solutions have a specific gravity greater than rock (2.77), one is justified in regarding them as true magmatic solutions. It is shown later in this, paper,. however, that at Lead, S. D., water not more highly concentrated' than ordinary drinking water is depositing vein matter around fragments of schist and of steel in such a manner that the fragments are completely isolated and completely surrounded by the mineral cement.

Jan 1, 1928

By D. Harrington

Efficient ventilation of metal mines consists in having such complete control of air currents that there is always supplied at placcs where men work sufficient moving air to allow working at maximum capacity without injury to health; and in case of underground fire or of surface fire in the vicinity of mine openings, underground air currents may be quickly reversed if desired, or air may be sent into or excluded from any region and fire fumes confined to only part of the mine workings, instead of penetrating practically the entire mine. Health and safety of workers in mines as well as proper safeguarding and operating efficiency of mining properties are so intimately associated with proper ventilation of mines (both coal and metal) that they are inseparable, yet ventilation is only too frequently neglected, especial1y in metal mines. The metalliferous operator, generally not confronted with inflammable gas or explosive dust which so frequently force ventilation of coal mines, usually disregards air supply altogether except such as may be obtained from compressed air; and generally, even when attention is given to metal-mine ventilation, the air currents rarely are found where they are needed, namely, the working places, especially the working faces. After several years' study of miners' consumption, the writer is convinced that long continued breathing of air impregnated with large quantities of any kind of finely divided dust, such as is found in a large number of the working places of our mines, will ultimately produce some respiratory disease, whether it be asthma, bronchitis, or phthisis; and the progress of these diseases is hastened if there are also present high temperatures, high humidities, or harmful gases or if there is present (and allowed to remain to be breathed) large quantities of the finely divided dust when air temperatures are low, hence favorable to maximum performance of work with accompanied maximum breathing into the respiratory passages of the harmful material. It is generally accepted

Jan 1, 1923