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By J. M. Glass, C. D. Sholtess

We at Hughes Tool Co. are extremely proud of the quality of the hardware and techniques introduced through our efforts in tunnel-machine development and of the ready acceptance of them by manufacturers and contractors throughout the world. All of us who attended the conference and who are represented in the book, we believe, anticipate an increasing need for improved methods of underground excavation. The development of such methods will permit the further exploitation of our underground resources plus providing underground space for transportation and habitation at a rate compatible with demand. We hope that our comments, derived from the application of Hughes Tool Co.'s rotary boring experience, may provide a better understanding of the boring method as a possible avenue through which the desired improvement in underground excavation may be attained. We hope you may also become aware of some of the problems Hughes, as a pioneer developer of raise, shaft, and tunnel-boring equipment, must face prior to further major undertakings in this very interesting field. Our task is to acquaint you with the present status of the Hughes Tool Co. development program as it relates specifically to tunnel-boring machines. We feel this task can best be accomplished by a brief review of the general sequence of events leading to and constituting an equipment development program and more specifically the manner in which these events have occurred to either influence or further our boring-machine development program. The development of a machine to accomplish a certain function or series of functions is usually a very long and tedious process to which any number of individuals must contribute, perhaps over a period of centuries. Of particular irony is the fact that often those who contribute most generously do not necessarily reap the greatest immediate benefit. A marketable ma- chine will, however, result from a sequence of events such as these: 1) A problem or need is defined. 2) An idea is born to eliminate the problem.

Jan 1, 1970

By V. (“Viv”) R. Forbes

[ ] INTRODUCTION "The Liberal Party believes that the State's mineral resources belong to the people of Queensland and therefore it is essential that the state, on their behalf, obtains maximum benefit from the development of those resources." (Liberal Party, 1980 "Mineral Resources Policy" p.2). "Unless sound policies are implemented.... increased production of minerals will benefit only the already wealthy and the lucky few... A resources tax is essential to ensure that above normal profits are shared by the whole community.... Labor policies on taxation must ensure an adequate return from mining developments to the Australian people." (Labor Party Policy Paper, May 1982 "National Issues relating to rapid expansion of mineral production during the eighties". p.1, 37, 47). Judging from these statements, key political parties in Australia believe that mining profits are lightly taxed and that shareholders get most of the benefits. THE REALITY The Government Share of Income statement in Table 1 attempts to measure the government share of the income generated by the "Big Five" Australian mining companies - Broken Hill Pty Ltd. (BHP), CRA Limited, Utah International, MIM Holdings Ltd., and Western Mining Corporation ("WMC"). These companies control over 70% of Australia's mining industry including all the most profitable mining operations. They dominate the mining and processing of iron and steel, aluminum, manganese, coal, oil and gas, copper, lead, zinc, silver, nickel, gold, ferro-alloys and salt in Australia. They are also major world exporters of most of these products. They are thus a representative sample of the profit-earning side of the Australian mining industry. In their two most recent financial years these five companies had income before tax of A$6,980 million. The Government share of this income was A$6,285 million or 90%. The total market capitalisation of the Big Five is about A$8,480 million. (December, 1982). Governments thus consumed the equivalent of 82% of their total value in just two years. This was taking place while the politicians drafted the above statements calling for an "adequate" share for the people.

Jan 1, 1985

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943

By P. B. Elkin, K. C. Ten Brink, Allen D. Garrison

It is the purpose of this article to present the results of an investigation of certain clay and shale suspensions having viscosities that are materially influenced by fluid motion, and to discuss the bearing of these results upon the choice of policy in the control of drilling fluids. A previous article described the design and the characteristics of an instrument adapted to measure the viscosity of plastic suspensions during continuous uniform motion and at a variety of speeds.' It has long been recognized that the viscosity of a clay suspension depends on the past history of the fluid motion. Since an abundance of literature is available on this phenomenon,2 it is not necessary to describe it in more than general terms. It is usually observed that rapid motion reduces the viscosity of a clay suspension, and that some time is required for the viscosity to fall to its equilibrium value after the steady motion is started. On reducing the speed of motion to some lower value, the viscosity again rises, but it also requires some time to attain a steady viscosity value at the slower rate of motion. Thus clay suspensions are usually observed to be increasing in viscosity as time passes when the measurement has been immediately preceded by fluid motion that was more rapid than that employed in the measurement. And it is usually observed that the viscosity falls as time passes when the measurement has been preceded by more quiescent conditions. Reed,3 and Broughton and Hand4 have reported a condition of observation of clay suspensions in which the viscosity was observed to fall during the first few moments of steady motion, and rise thereafter. The characteristics of the new instrument are particularly well adapted to studies of this kind. With it we have been able to observe all of the phenomena described above, and it is important to understand their nature because they all occur at some time during normal drill-

Jan 1, 1940

By Lloyd Emory

THE region known as. Guyana or Guiana stretches along the north coast of South America from the mouth of the Orinoco River in Venezuela to the mouth of the Amazon River in Brazil. Politically, it is divided into British, Dutch, and French Guiana, extend¬ ing into Venezuela on the north and into Brazil on the south. Because the area is within the sweep of the northeast trade winds and of approximately the same latitude, plant' and animal life are fairly uniform throughout. The geology is very similar as far as the northern coast is concerned. The drainage is taken care of by a number of large rivers that flow northward directly into the sea. The Courantyne River, which roughly divides the area into half, is the eastern boundary of British Guiana.1 The lower reaches of this river are also the center axis of an ancient bay that at one time indented the coast-line at this point. The old shore-line and, in fact, successive shore-lines can be traced from near the present coast-line in, the northwest district of British-Guiana, south-east and inland, crossing the Essequibo River near Dahli, the Demerara near Christianburg, the Berbice at the mouth of the Kuruduni River and the Courantyne at Vaka-Kuyaha Falls. The line then swings around to the northeast and again approaches the coast near St. Lau-rent in French Guiana. This article will be confined to British Guiana and largely to the valley of the Demerara River, but for geographic names .and topographic details it might, however, apply to Dutch Guiana as well. British Guiana, which comprises about 90,000 sq. mi. and is as large as England, Scotland, and Wales combined, may be divided into three belts, the alluvial belt or coastal plain, the foot-hill area (often spoken of as the sand clay belt), and the hinterland.

Jan 1, 1928

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943

By E. W. Greene, J. B. Duke

This paper deals with the application of froth flotation techniques to the beneficiation of kaolin clay and phosphate slimes, two very fine particle sized materials. The kaolin problem involves the removal of a small amount of a contaminating mineral (anatase), while the phosphate problem involves the concentration and recovery of a much larger percentage of apatite. Due to these differences, and also different response to flotation, the two problems are discussed in separate parts of the article. An idea of what is meant by "Ultrafine Minerals Or Slimes" as used in the title can be had by an examination of Fig. 1. Particle size distributions are presented for a crude kaolin clay, a coarse fraction and a fine fraction. The crude kaolin as mined was blunged with water, degritted through a 325-mesh Tyler screen, and dispersed with sodium silicate. The dispersed crude was then centrifuged in the laboratory into the coarse and fine fractions shown in the figure. The distribution curves were obtained by the well known sedimentation technique of Casa-grande1 using a long arm centrifuge to obtain equiva- lent spherical diameters down to 0.2 p on the finer fraction. Fig. 1 shows the coarse fraction kaolin to be 50% finer than 3 p, while the crude kaolin is 509 f'lner than 1.4 p, and the fine fraction 50% finer than 0.46~. For comparison 53 p on the horizontal scale would represent Stokesian diameters which would just pass a 325-mesh Tyler screen, taking into consideration the Andreasen sieve correction factor of 1.22 times the screen opening. 2 Another helpful comparison is the surface areas, which in square meters per gram, are 0.044 for 53 p particles, 0.77 for 3p, 1.65 for 1.4 p and 5.0 for 0.46 p particles. Fig. 2 is an electron micrograph of a similar fine fraction kaolin showing the hexagonal plate-like particle shapes.

Jan 1, 1962

By F. G. Tickell, R. C. McCurdy, O. E. Mechem

The behavior of fluids in the voids of a rock is fundamental to the study of many of the problems of oil-field development and production. For it is by virtue of these openings between grains that oil and gas are able to move through the rock, to be contained by the rock, and to pass from the rock into the well. The capacity to contain fluids is measured by the porosity of the rock, and the ease of fluid movement is governed by the permeability. When the engineer wishes to estimate the amounts of oil and gas in an underground reservoir he is often concerned with the porosities of the rocks and, when dealing with problems relating to rate of production, he is more likely to be interested in the permeabilities of the rocks. Rocks are permeable because they are porous, but they may be porous without being permeable. Clays are very porous, and yet they are impermeable from a practical standpoint. Attempts have been made1 to correlate permeability with porosity for certain rock members but, where a definite relationship between these two properties is found to hold, it is purely fortuitous and local. Porosity and permeability do not necessarily bear any quantitative relationship to one another. The porosity of a substance is the percentage of void volume to bulk volume. The petroleum engineer is usually interested only in the inter-granular voids that are accessible to fluids. In measuring porosity he does not wish to include scaled openings. The measurement he desires is one of "available porosity," otherwise called "apparent porosity." The porosity of a natural aggregate of solid grains, such as a sandstone or clay, is governed by: (1) Grain-size distribution, (2) angularity of grain, (3) colloidal content, (4) degree of compaction. It is not difficult, for unconsolidated rocks, to measure the effect of any one of these when it alone is varied, and then to predict what the effects on porosity will be for such single variables. It is very difficult, however, if not

Jan 1, 1933

By K. C. Ten Brink, Allen D. Garrison, P. B. Elkin

It is the purpose of this article to present the results of an investigation of certain clay and shale suspensions having viscosities that are materially influenced by fluid motion, and to discuss the bearing of these results upon the choice of policy in the control of drilling fluids. A previous article described the design and the characteristics of an instrument adapted to measure the viscosity of plastic suspensions during continuous uniform motion and at a variety of speeds.' It has long been recognized that the viscosity of a clay suspension depends on the past history of the fluid motion. Since an abundance of literature is available on this phenomenon,2 it is not necessary to describe it in more than general terms. It is usually observed that rapid motion reduces the viscosity of a clay suspension, and that some time is required for the viscosity to fall to its equilibrium value after the steady motion is started. On reducing the speed of motion to some lower value, the viscosity again rises, but it also requires some time to attain a steady viscosity value at the slower rate of motion. Thus clay suspensions are usually observed to be increasing in viscosity as time passes when the measurement has been immediately preceded by fluid motion that was more rapid than that employed in the measurement. And it is usually observed that the viscosity falls as time passes when the measurement has been preceded by more quiescent conditions. Reed,3 and Broughton and Hand4 have reported a condition of observation of clay suspensions in which the viscosity was observed to fall during the first few moments of steady motion, and rise thereafter. The characteristics of the new instrument are particularly well adapted to studies of this kind. With it we have been able to observe all of the phenomena described above, and it is important to understand their nature because they all occur at some time during normal drill-

Jan 1, 1940

By R. Janes, F. Everard

Pilot plant studies have been conducted on a variety of iron ores of differing composition and grain size to test their amenability to dry autogeneous grinding and dry magnetic concentration. A general description of the pilot plant and its equipment is given with particular reference to the Aerofall mill and the dry magnetic separators developed by the Ontario Research Foundation. Test results are reviewed in detail with emphasis on power consumption, mill speed, the use of ball charges, types of ores, moisture content, separator speeds, and design. In 1957 the Ontario Research Foundation installed a pilot plant (Fig. 1) for the study of dry autogenous grinding and dry magnetic concentration of iron ores. A 61/2-ft Aerofall mill was installed as the dry autogenous crushing and grinding medium. The Cavanagh fast drum and the Double Helix, two dry magnetic separators developed at Ontario Research Foundation, were also installed. Iron ore samples of 10 to 150 tons have been investigated. These ores varied widely in mineralogy and grain size. Taconite (-325 mesh), fine-grained magnetite (200 to 325 mesh), and medium-grained magnetites (65 to 150 mesh) have been treated with varying degrees of success. Lately, considerable research has also been conducted on the metamorphosed magnetite-hematite complexes of the Labrador Trough. Operational and metallurgical data have been compiled from these tests. The effects of ore type, air flow, mill speed, and ball charge on mill operation are discussed. Metallurgical data are also presented to illustrate the operation of the dry magnetic separators. PILOT PLANT DESCRIPTION Fig. 2 depicts the normal flowsheet used. Minus 6-in. ore from a vibrating feeder is fed to the 6%-ft Aerofall mill powered by a 50-hp 550-v induction motor. The main blower, a 25-hp 550-v fan rated at 7000 cfm, draws air through the mill. Finely ground ore is conveyed by the air stream to a horizontal classifier, where expansion and a change in direction cause the +I50 mesh fraction to fall onto a vibrating

Jan 1, 1962

By Van H. Manning

In substance, the international aspects of the petroleum industry, as these relate to the United States, are as follows: The domestic production is not keeping pace with the domestic demands; our best engineering talent warns us of the imminence of a decreased production by our oil wells, although more oil is needed; and the only practical source whence this increasing demand can be supplied for some time to come will be the foreign fields. Other nations have given thought to the future and, in recent years, have shown a tendency to adopt strong nationalistic policies regarding their petroleum resources, policies that hinder or prevent the exploitation of these resources by other nationals. In consequence, we find that, facing a probable shortage of the domestic supply, our nationals are excluded from foreign fields; and this in spite of the fact that foreign nationals have been permitted to enter into and exploit our own oil resources on an equality with American citizens and without hindrance or restrictions. This country has supplied the larger part of the petroleum consumed by the world and yet, with a failing supply imminent, it finds that those countries that, have been drawing upon our resources to supply their needs are showing a tendency to exclude us from their resources. In this way we shall be transferred from a position of dominence to one of dependence; and only by sufferance of those countries that are now seeking financial or political control of petroleum supplies, shall we be able to obtain the oil we will need. Impoetance of Petroleum Petroleum has become, during recent years, one of the essentials of our social and industrial life. All civilized countries recognize that the world is dependent on petroleum as on nothing else except textiles: foodstuffs, coal, and iron. Today, the tendency is toward an ever-increasing consumption of petroleum and its products as new and more efficient uses are found for them. The utilization of petroleum is extending more and more into the structure of our civilization. Consequently,

Jan 1, 1921

By William L. Saunders

Many members of the Institute, who participated in the visit made, during the Bethlehem meeting of February, 1906, to the shops of the Ingersoll-Rand Company, at Phillipsburg, N. J., inspected with interest the new Electric-Air drill, which the company had set up for the purpose of showing it in actual operation to American mining engineers. At the request of the Secretary of the Institute, I promised at that time to prepare a paper for our Transactions, describing the construction and advantages of the machine. But such a paper would then necessarily have contained much that was only expected or claimed by the designers and manufacturers of the drill, and not yet incontrovertibly proved by varied and long-continued practice. However moderate such statements might have been, they would have given inevitably to the paper, to some extent at least, the air of a prospectus, rather than of a technical contribution. I therefore decided, with the Secretary's approval, to postpone the writing of the promised paper until it could set forth the results of adequate actual practice, as well as the latest details of construction, etc., based upon practical experience. That period has now arrived. The Electric-Air drill has been exhaustively tested in the field, under varied and arduous conditions and upon the hardest rocks. It is now fairly in the field; its merits and performances are matters of unimpeachable record, and its place among established competitors can be definitely determined. As a representative of the Ingersoll-Rand Co., as well as a member of the Institute, I may be permitted to add that my company, being largely interested in the manufacture of air-coxpressors and machinery driven by compressed air, has no desire to injure its own business by claiming for this new machine that it should immediately supersede all existing applications of pneumatic transmission of power for drilling. On the

Jan 1, 1908

By W. Mostowitsch

Lead sulphate occurs as anglesite, and is formed in every roasting of lead sulphides or sulpho-salts containing lead. In smelting in the blast furnace an ore containing natural or artificial lead sulphate, a large part of the sulphur present goes to the formation of the intermediary product matte which requires further treatment for the recovery of the values it contains. It is therefore of importance to study the behavior of lead sulphate at elevated temperatures, both without and with reducing agents, especially as the information available gives data which are more or less conflicting. 11. Decomposition of PbS04 by Heat The dissociation of PbSO4 into PbO and SO3 or SO2 and 0 has been discussed by many metallurgists. The following data are considered to be representative. Doeltz and Graumannl found that PbS04 was not affected-by heat at 800" C.; that dissociation began at 900" C., and was rapid at 1,000° when the salt lost in 1 1/2 hr. 14.3 per cent. of its weight, the dry salt containing 26.43 per cent. SO3. Hofman and Wanjukow2 summarize their work upon the dissociation of metallic sulphates with the statement that the decomposition of PbS04 begins at 195' C., but progresses very slowly, with the formation of the basic salt 6PbO.5SO3 at 705"; that this salt undergoes a transformation at 847") begins to be decomposed at 888") to sinter at 896", and to fuse at 910"; rapid dissociation begins at 952") and is accompanied by volatilization of PbO; retardations at 958" and 962" indicate an acceleration of decomposition which, however, is not complete. Proske3 found that PbSO4 gave off at 900" C. in 30 min. only 0.63 per cent. of its 803, and that the loss increased with

Jan 1, 1917

By Allen Garrison

IT is the purpose of this article to present. the results of an investiga-tion of certain clay and shale suspensions having viscosities that are materially influenced by fluid motion, and to discuss the bearing of these results, upon the choice of policy in the control of drilling fluids. A previous article described the design and the characteristics of an instru-ment adapted to measure the viscosity of plastic suspensions during continuous uniform motion and at a variety of speeds.1 It has long been recognized that the viscosity of a clay suspension depends on the past history of the fluid motion. Since an abundance of literature is available on this phenomenon,2 it is not necessary to describe it in more than general terms. It is usually observed that rapid motion reduces the viscosity of a clay suspension, and that some time is required for the viscosity to fall to its equilibrium value after the steady motion is started. On reducing the speed of motion to some lower value, the viscosity again rises, but it also requires some time to attain a steady viscosity value at the slower rate of motion. Thus clay suspensions are usually observed to be increasing in viscosity as time passes when the measurement has been immediately preceded by fluid motion that was more rapid than that employed in the measurement. And it is usually observed that the viscosity falls as time passes when the measurement has been preceded by more quiescent conditions. Reed,3 and Broughton and Hand4 have reported a condition of observa-tion of clay suspensions in which the viscosity was observed to fall during the first few moments of steady motion, and rise thereafter. The characteristics of the new instrument are particularly well adapted to studies of this kind. With it we have been able to observe all of the phenomena described above, and it is important to understand their nature because they all occur at some time during normal drill-

Jan 1, 1939

By M. W. Von Bernewitz

AN important regional meeting of the American Institute of Mining and Metallurgical Engineers was held, at Salt Lake City on Aug. 22 to 26, jointly with the fifth annual meeting of the Western Division of the American Mining Congress. The whole meeting was marked by enthusiasm, keen attention to the subjects under discussion, and many renewals of personal contacts. The trips to the various plants were well attended and the local press paid much attention to the meeting. The A. I. M. E. sessions began Aug. 23, with a non-technical morning session. J. 0. Elton, manager for the International Smelting Co., presided. The purpose of this session was to present in a non-technical manner the relation of flotation to mining, smelting, and the State. Ernest Gayford, metallurgist with the General En-gineering Co. of Salt Lake City, gave the definitions of flotation as suggested by Rickard, the dictionary, Weinig, and Taggart. The active agent in flotation is the air bubble, and the two prime requisites are the formation of bubbles and the creation of selective action of the bubbles for metallic particles instead of for gangue particles. Broadly, all the sulfides are floatable minerals, but the oxides, carbonates, silicates and sulfates are not. As far as Utah is concerned, flotation has been one of the greatest means of conserving its natural re-sources, because it has converted millions of tons of waste rock into pay ore; it is recovering millions of pounds of metal formerly lost in tailings; it has con-verted the zinc from a liability into an asset; and has kept thousands of men at work and distributed millions in dividends for the benefit of the State. As to the future of flotation, Mr. Gayford can con-ceive that the next 5 or 10 years may see as much, if not more, advance than was made in the preceding period. The big problem is dressing oxides, carbonates, silicates, and sulfates, and simplification of the number of reagents, also the separation of different gangue min-erals from one another.

Jan 10, 1927

By Orson Shepard

TEXTBOOKS on fire assaying list the following standard methods of assaying sulphide ores: (1) scorification, (2) litharge-niter, (3) soda-iron, (4) roasting, (5) combination wet and fire. The litharge-niter method has proved the most satisfactory, and is the usual method for assaying sulphide ores and concentrates. It gives good results when suitably conducted and when lead buttons of uniform size are produced so that the cupellation temperature can be properly controlled. The main objection to the method is the inconvenience of determining the amount of niter to add to each assay charge to produce lead buttons of suitable size from a set of fusions. For the assay of different materials, the niter requirement varies with the particular sulphide minerals present, the amount of sulphide minerals present, the slag composition, and the rate of heating the charge in the furnace. Except for some materials, so uniform in composition that the same amount of niter can be used in assaying all samples, the amount of niter must be determined for each sample to be assayed. This is done by either: (1) calculation from an estimate of the kind and amount of sul-phide minerals present in the sample, or (2) a preliminary fusion. Some assayers use one method and some the other. The estimation method takes the least time; but much experience is required to obtain close estimates on a wide variety of materials. At best, the sizes of the lead buttons obtained vary considerably. The preliminary fusion method usually gives lead buttons of fairly uniform size, although sometimes there is a variation because the oxidizing power of niter varies a little with the charge. This variation can be eliminated by two preliminary fusions: one to determine the reducing power of the ore, and the other to determine the oxidizing power of niter in the charge. The objection to the prelimi-nary fusion is the extra time and expense involved.

Jan 1, 1939

By Leroy Gardner

EVERY reader of this paper is well aware of the fact that the prolonged inhalation of large amounts of free silica dust results in fibrosis of the lungs, and that other inorganic dusts, except those of asbestos and the mineral poisons, are thought to be relatively harmless. But probably few have had opportunity to visualize the effects of silica, asbestos and other minerals upon living tissues. The ideal demonstration would be based upon sections of lungs from human beings that had inhaled com-parable concentrations of different dusts for a unit period of time. Such material is generally difficult to obtain and in some instances is of ques-tionable value because the subject has been exposed to more than one kind of dust. A demonstration could be prepared from the lungs of animals. However, so many months or even years are required to com-plete the exposure to each kind of dust that enough material has not been accumulated. For a general survey of the action of different types of dust, I am therefore compelled to use the tissues of animals that have been injected with suspensions of dust particles. The injection method offers certain advantages. The quantity, the particle size and the state of dispersion can be controlled with sufficient accuracy so that the tissue responses to different minerals can be accu-rately compared. The method insures contact between the tissues and the mineral particles; protective mechanisms, which may prevent the inhalation of certain types of foreign body, never come into play. If the pathway of injection be one that minimizes nonspecific injury, the tissue responses may simulate those produced by inhalation but they develop somewhat more rapidly. It should always be remembered that injection methods merely demonstrate the capacity of various kinds of minerals to provoke reaction in the tissues; whether the same substances are inhaled from atmospheric suspension and accumulate in the lungs in dangerous quantities can be demonstrated only by inhalation.

Jan 1, 1938

By R. P. Heuer, Paul M. Tyler

THE literature on refractories, although fairly extensive, is so scattered through books and periodicals as to be difficult of access to the general reader and most of the individual papers serve merely to illuminate some particular phase of the industry. Two general treatises by American authors8.16 are available, also the somewhat older works by a well-known British authority, 12,13 but these make their appeal to the technically minded ceramic engineer. Another small group of publications deals with the use of refractories, mainly in the iron and steel industry.1, 3,5,6,11,15 Raw materials utilized by the refractories industry have been covered by sundry books and articles. For the relatively nontechnical reader and economist, however, there appears to be no single review that purports to describe the industry as a whole. Furnace linings and other products that are classed as "refractories" are designed primarily to withstand high temperatures but this important property is by no means the only requirement; a suitable refractory material must likewise withstand slagging (chemical' action), abrasion (physical wear), and spalling, as well as the various other stresses and physical phenomena induced by heat, of which softening or incipient melting is only one phase. Nevertheless, subject to these highly practical considerations, the definition of a refractory material is based upon temperature resistance. Broadly speaking, any material that shows obvious signs of fusion after being heated slowly to 1500°C (2732°F) cannot be classified as a refractory material. The characteristic properties and requirements of refractory materials are conveniently summarized in Fig 1, prepared on the American Refractories Institute Fellowship at Mellon Institute, Pittsburgh, Pennsylvania. Most of the factors of service and properties of refractories given in this chart are interdependent and are greatly affected in degree by the functions of temperature and time. The factors in the chart are believed to cover the commoner questions.

Jan 1, 1949

By C. W. Hall

Owing to its isolation and comparatively small tonnage, the Yoquivo district is not widely known; though financially important and, geologically, quite interesting. San Francisco dc Yoquivo, the center of the mining district, is in the western part of the state of Chihuahua, Mexico; about 35 miles west of. San Juanito, on the Kansas City, Mexico & Orient R. R. The town can be reached from the railroad by a good trail over a rugged country. The elevation of Yoquivo is 6500 ft., and peaks surrounding the town are 2000 ft. higher. The mining towns of Concheno and Ocampo are 25 miles northwest, and Uruachic is 20 miles southwest. The climate, temperate and healthful, is almost ideal. The rainy season begins in July and ends the latter part of September. There is usually, though not always, some precipitation in all months except April, May, and June: The mountains are covered with pine and scrub oak. Water, wood and lumber are plentiful for all ordinary purposes, and hydroelectric power is available for. about six months of the year, when wood for steam, power is utilized as an expedient. The district has been worked: recurrently for over 60 years. The Yoquivo province lies on the steep western-slope of the Tara-humara division of the Sierra Madre range of mountains. The province is traversed by many deep canyons, most of which flow west. The town is situated on the San Francisco arroyo, which makes a confluence with the Huevachic stream 212 m. southwest; the Huevachic in turn joins the Candemeña river farther down and these two drain the western flank of the Tarahumara mountains and form the headwaters of the Mayo river. The claims of the Yoquivo Development Co., which, is the only organization in the district with a record of any considerable production,: lie within an area roughly 112 m. square. The area extends from the, San Francisco arroyo north, and from the Dolores arroyo west, and is confined to the andesitc formation.

Jan 2, 1926

By Quentin D. Singewald, B. S. Butler

Some of the broader relations between structure and ore deposition along the London fault, deduced from a thorough study of the geology of the eastern part of the Mosquito Range, should be of general interest to economic geologists. The first part of this paper is a generalized statement of the geology of the region in which the London fault is located; it may be supplemented by reference to several earlier publications by the writers and to the U. S. Geological Survey's Professional Paper 148, on the Leadville district. The second part deals with the structure of both the fault and the disturbed zone adjoining the fault. The third part discusses the salient features of the ore deposits, particularly emphasizing structural control. The two generalized maps are complementary to one another but contain too many data to show on a single small map. The London fault is between Leadville and Alma, and the ore deposits along it are said to lie in the Alma district. Field work in this district, during six summers since 1927, has been a part of the cooperative work of the U. S. Geological Survey, the State of Colorado, and the Colorado Metal Mining Board. The writers have made use of work by R. D. Butler, J. W. Vanderwilt and R. E. Landon. G. F. Loughlin and C. H. Behre, Jr., who have worked on the west side of the range, have contributed valuable suggestions. Mining men of the district have aided in many ways. General Geology Pre-Cambrian Rocks.—The oldest rocks in the district are schists, correlated with the Idaho Springs formation of the Front Range. Quartz-mica schist predominates, but other types occur locally; almost everywhere the rocks show considerable lit-par-lit injection. Intrusive into the schists are two varieties of granite, only one of which is widespread. It is a fine-grained, porphyritie, gray granite correlated with the Silver Plume granite of the Front Range. Near the head of Buckskin Gulch a

Jan 1, 1937