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By V. G. Mooradian, John T. Norton

THE diffusion of metal atoms into the crystal lattice of another metal and the assumption of regular positions to form a homogeneous alloy are some of the most fundamental phenomena of structural. metallurgy. The mechanism of this process has been the subject of a great deal of study from many viewpoints, but the picture is still far from complete. It is generally believed that if one metal is to diffuse into another, the first must have some solubility in the second1. This means that the solvent must be able to accommodate the stranger atoms, either on points of its own lattice or in the interstices between, without losing its own crystallographic identity. It is also a general observation that cold-working is a distinct aid in the diffusion process, causing it to take place with greater rapidity at the same temperature or with the same speed at a lower temperature. There is considerable doubt, however, as to the real significance of the deformation in its effect on the diffusion mechanism. Several factors associated with the cold-working. may be responsible for the increased diffusion rate. The plastic deformation causes a distortion of the solvent lattice, which may be an aid in the assimulation of atoms of another kind. There are many references2 in the literature that suggest that some distortion or "loosening" of the lattice is necessary for atomic migration and that diffusion cannot take place in the undis-

Jan 1, 1935

By G. B. Gould

EVERY mathematical statement of a measure of anything (as distin-guished from a count) is followed by a qualification always implied if not explicity stated--that the statement is only an estimate, which may vary from absolute accuracy within certain limits, according to the accu-racy of the measuring instrument. This basic fact, so obvious to engineers, is not so well understood by many that make use of laboratory coal tests. The tolerances that must be allowed in measurements of coal quality are very important in both their commercial and engineering applica-tions-and the significance of these tolerances depends upon the use made of the laboratory coal test. Only in recent years has there been any intensive study of this ques-tion of tolerances as applied to measurements of coal quality. There is very little in our published literature on the subject, and what has been published is not, readily comprehended by those who sell coal, or buy coal and use it, unless they happen to have made a study of the subject them-selves. There is great need for more widespread understanding of what has been discovered and how it applies to the use of laboratory coal tests. What follows is an attempt to condense into a few pages the results of the major investigations so far reported, and to explain their meaning in simple nontechnical language, with the addition of some recent illustrative experiments.

Jan 1, 1937

By Paul Torrey

IN his recent article, Stanley C. Herold described some of the principles involved in oil-field rejuvenation. The purpose of this paper is to present certain facts, based upon observations of systematic water flooding of oil sands in the Bradford and Allegany fields of northwestern Pennsylvania and southwestern New York, which, it is believed, will partially substantiate Mr. Herold's opinions. The writer gratefully acknowledges his obligation to the Forest Oil Corpn., the Kendall Refining Co., the Petroleum Reclamation Co., W. J. Healey, of Bradford, Pa., and the Producers Oil Corpn., of Olean, N. Y., for information included in this article; and he is especially indebted to Jerry B. Newby, of the Petroleum Reclamation Co., for helpful suggestions and criticism in the preparation of the paper. It is obvious that, in the calculation of mathematical formulas for the prediction of oil recovery, uniform conditions must be assumed; otherwise, the applicability of the results of such work will be, by necessity, restricted to the area or individual property for which they were designed. Geologic and physical conditions are so variable throughout the fields where water flooding is practiced that it is difficult to devise methods that can be universally applicable. However, it is believed that there are certain fundamental principles which, when applied with specific modifications designed to meet the conditions existing in local areas or individual properties, may yield considerably greater recoveries of oil.

Jan 1, 1927

By I. L. Greninger

THE property of the Andes Copper Mining Co. is in the central part of the Republic of Chile, Province of Atacama, 147 km. (91.5 miles) eastward by rail from the port of Chañaral. At this point the Andean system is made up of two principal ranges. The mine is on the westerly slope of the outer, or western, range, at a mean elevation of 3250 m. (10,500 ft.). A meter-gage railroad extends from the company's port at Barquito, near Chañaral, to the reduction plant at Potrerillos. This road has a total length of 151 km. (94.0 miles), of which 93 km. (57.79 miles) are owned by the Andes Copper Mining Co. The remainder of the road is owned by the state. The company operates its trains over the portion of the road owned by the state, under an agreement with the Chilean Government. The mine is connected with the reduction plant by a meter-gage railroad, 10 km. (6.214 miles) long, which extends from the coarse ore bins at the metallurgical plant to the underground storage bins at the mine. Tunnels make up 60 per cent. of the total length of this railroad. As is characteristic of the Andean region in Chile, the topography of the locality is extremely rough, and a number of points near the mine have elevations of from 15,000 to 16,000 feet.

Jan 1, 1928

By R. Lyndon Arscott, P. Hackett

This chapter reviews the early stages of a study designed to investigate the physical behavior of the coal measure rocks around longwall panels over a relatively large area. The aim of the work is to attempt to explain a directional tendency for a certain type of underground fracture. The geological structure of the area is reasonably uniform but the effect of some local anomalies is also discussed. Although some definite tendencies have been recorded, the results so far achieved need confirmation by further experiments. The chapter deals first with some in-situ strain measurements carried out in longwall panels and continues with a discussion of the relationships between induced fractures and the natural variations in the structure of the rock mass. Finally, some light is shed upon the gas outburst phenomenon although eradication of the hazard is far from assured. STRESS AROUND A LONGWALL PANEL Considerable progress has been made during the last few years towards the determination of the mechanism of failure of small samples of rock under varying environmental conditions. Much more laboratory testing needs to be done in this field but an even greater amount of study needs to be devoted to the extrapolation of laboratory phenomena to failure around underground excavations. The problem is made more difficult because the stress redistribution around an excavation is often difficult to define, particularly when part of the rock mass fails and a

Jan 1, 1972

By R. L. Stephenson

IN plants casting electric-furnace ingots and converting them immediately into blooms, billets, slabs, bars or forgings, the criterion of quality performance is the soundness of the semifinished or finished product. When rejections are necessary, it is not always obvious whether the defects were caused by an unsound ingot or by improper treatment during the heating and forming operations. To evaluate the effects of the numerous factors involved, it is necessary to accumulate a large number of detailed observations and to analyze and interpret these data properly. Even after a thorough investigation has been conducted, it is impossible, in some cases, to isolate the cause of the defect and say that it is definitely the result of an unsound condition in the ingot or mistreatment of the ingot during further processing. Two factors that are extremely difficult to evaluate are the chemical composition of the steel and time from finish pour to charge in the soaking pits or "track time," and it is necessary to evaluate their combined effects before many other factors can be studied. Plain carbon, fine-grained steel in the range of 0.18 to 0.23 pct carbon, is very susceptible to cracking and the longer the elapsed time between the pouring of the ingots and stripping for charging into the soaking pits, the higher the billet rejections for cracks are found to be. Below 0.15 pct carbon and above 0.30 pct the track time

Jan 1, 1947

By E. H. Rose

THE question is often pondered whether the flotation process is still an art or has become a science. The fact is that flotation is a science in so many variables that only art can blend them. It is demonstrable that no less than one hundred variables are involved in any flotation operation, most of them immeasurable on a routine basis. The behavior of every one of them is always governed by orderly and unchanging law, as no man can doubt. There is nothing truly indefinite about that behavior; the only indefiniteness is in our knowledge of it, either in general or from hour to hour in the circuit. In dealing with a simultaneous equation in, say, one hundred variables, all not only affecting the outcome to some degree but many influencing each other as well, it is small wonder that the mineral-dressing profession presents a case history of debate and controversial opinion. The statement of the subject of this symposium-a symposium on flotation machines-seems to delimit and define the matters to be considered and at least the general nature of the conclusions sought. Nevertheless, in such a meeting it is not possible to meditate upon all the variables that do in one way or another affect performance of flotation machines. To attempt it would be much like trying to operate a hundred-ring circus. Perverse variables being what they are, one could expect the elephant in ring 36 to squirt a trunkful of water at the tightrope performer in ring 37 to ruin that artist's act, just as our learning to depress pyrite in the early 1920's ruined the act of the formerly faithful old Callows. HONEST DISAGREEMENTS Selective flotation dates from 1922 or 1923, when several plants established their regular flotation operations on a selective basis. Since then, two decades of efforr have gone into the development of better and better flotation machines. Many have come and gone. The competition has simmered down to perhaps a dozen machines, each one of which is staunchly defended by some operators as being the best for their particular jobs, and as scornfully dismissed by at least a few others elsewhere as being positively the poorest for theirs. These disagreements are honest disagreements, honestly arrived at after plenty of sweat. In many a flotation plant, one machine has been tried out against another under conditions as fair as they could possibly be made. Sometimes the results are on a par but more often one machine shows a consistent and unmistakable margin of superiority over the other. In equally honest and enlightened tests, machine A may win over machine B in one place, and machine B over machine A by as great a margin in another. This paper purposes to identify some of the more prominent reasons why this is so,

Jan 1, 1944

By W. Shockley

THIS lecture can best begin with a statement of the chief conclusion: The metallurgical industry will find profit in supporting fundamental research on dislocations. This support should be done both in their own laboratories and in universities. My lecture consists of an exposition of the basis for this conclusion. The experience on which I base it is drawn largely from two fields in solid state physics—one field is transistor electronics and the other is dislocation theory. At present the relationship of solid state physics to technology is different in these two fields. In electronics without question, the physics has led the technology. In metallurgy, on the other hand, the technology in the form of metallurgical art is far ahead of the fundamental science. In transistor electronics, physics has suggested and can still suggest previously unachieved combinations of matter that will have new and useful properties; that is, the physicist can make specific predictions. The physicist can also have some confidence that the predicted devices will actually come into existence in a matter of months or years and that they will live up to the predictions. In metallurgy, the physicist cannot to a comparable degree make predictions and have the same hope that they will lead to something new and valuable. There are a number of reasons for this difference. The first is simply historical. Transistor physics is young. It may be regarded as dating from the announcement of the transistor, in which case it is about four years old, or from the first real control of semiconductors as materials (this was accomplished largely by metallurgists, by the way) in which case it is about ten years old. Metallurgical art, on the other hand, is thousands of years old. There is no doubt that the advance of this art has been and will be hastened by a good fundamental understanding of the quantum theory of atomic phenomena. It, is too much to expect, however, that theory will soon catch up with the lead that practice has gained in a thousand years, and that theory will then point out specific pathways to better materials. It seems more probable that modern atomic theory will serve to interpret and organize information much as thermodynamics has done through phase diagrams. In this lecture, I shall emphasize an important feature common to both solid state electronics and to metallurgy. This common feature is the harmonizing principle that justifies discussing electronics and metallurgy as related topics in solid state physics. In both cases the important properties of the materials arise from imperfections. By imper- fections I mean deviations of the materials from perfect single crystals. The imperfections may be of many forms. From the point of view of utility they may be either good or bad, and a given type may be good or bad depending on circumstances. The technical material of my lecture will be divided into two parts. The first will be chiefly concerned with four types of imperfections in germanium crystals. The control of these imperfections makes possible the fabrication of useful electronic devices. A good example of such control is the junction transistor, which I shall discuss from this viewpoint later. The junction transistor, as some of you may have heard, can be used as an amplifier of electrical signals and in a number of respects surpasses what has hitherto been achieved with vacuum tubes. The second part of my technical material will be concerned with dislocations. For about fifteen years the theoretical physicist has had dislocations in mind as the most important kind of imperfection in metals. He has, however, until recently had experimental material of a highly speculative nature to back up his assertions. I am fortunate in the timing of this lecture to be able to describe some recent results that put dislocations on a far more definite basis than has been the case in the past. In fact there are now some experiments which reveal the characteristic properties of dislocations almost as clearly as experiments in transistor physics reveal the properties of holes and electrons, properties that I shall soon describe. It is this advance in the status of dislocations that emboldened me to make my initial assertion that the metallurgical industry will profit from supporting fundamental research on dislocations. Transistor Electronics In order to discuss imperfections in semiconductors, it is necessary to visualize a reference condition that may be regarded as perfect. In the cases of silicon and germanium, which find application in transistor electronics,' the perfect structure is the diamond structure shown in Fig. I. In this structure, each atom is surrounded by four neighbors with which it forms four covalent or electron-pair bonds. These bonds use all of the four valence electrons possessed by each of the silicon or germanium atoms. The electronic structure of the crystal is thus complete and perfect. A crystal of silicon or germanium with a perfect electron-pair bond structure would be an insulator, In order for electrical conduction to occur, it is necessary for imperfections to arise in the electronic structure. In this lecture, I shall discuss four possible imperfections whose symbols and relationships are indicated in Table I. We shall consider first, as an example, a crystal of silicon containing an arsenic atom as an impurity.

Jan 1, 1953

By M. Muskat R. D. Wyckoff

The phenomenon called "water-coning" is that, observed in many oil wells, in which bottom water gradually and frequently sudderlly displaces a part or all of the oil production when a certain rather critical production rate from the well is exceeded. To follow in detail the process of the formation of a water cone as it breaks through the oil zone and enters the well bore is a problem so complex as to make a theoretical analysis practically impossible. However, an analytical treatment of the flow system before the water has broken through and during the time that it lies statically beneath the oil zone with an elevated or "coned" surface can be carried through under certain approximations. To present an analysis which shows the essential characteristics of the coning mechanism is the purpose of the present discussion. Physical Basis of Theory and Meaning of Approximations As will always be true for flow systems where true water-coning is at all possible, the water will be supposed to lie beneath the oil zone because of its density contrast with respect to the oil. In fact, tinder the usual field conditions, when the pay horizon is reasonably homogeneous, the water most frequently enters the well through the lower zones, but even when it enters from intermediate zones it may, in the later life of the well, displace the bottom layers of oil, thus resulting in a system wherein the oil is effectively floating on the water.

Jan 1, 1935

By J. H. Wernick

IN temperature-gradient zone-melting1 a molten zone is moved through a solid or across a solid surface by the establishment of a temperature gradient. This technique has both practical and fundamental aspects. One practical application is to make p-n junctions for semiconductive devices, particularly for devices in which the junctions are desired within the semiconductor. From a fundamental point of view, the technique is being investigated as a method for determining diffusivities in liquid alloys, and preliminary diffusivity results have been reported by the writer." In this paper, the effects of crystal orientation, temperature, and molten zone thickness in temperature-gradient zone-melting, and the bearing of these effects on diffusivity measurements and n-p-n junction formation are discussed. Experimental Procedure An effect of crystal orientation was noted in early experiments. To facilitate its study, movements of wire zones across a surface, rather than through the body of a single crystal, were observed for various surface planes and travel directions. The experirr-entai setup is illustrated in Fig. 1. The graphite end-section for the high temperature heater has an apron about 1/16 in. above the upper surface of the crystal. This apron insures that the surface temperature of the block is equal to or greater than the temperature within the block at every point, Thus, the zone does not penetrate the block and convection in the liquid is minimized. The experi-through a block is shown in Fig. 2,

Jan 1, 1958

By Dermot Ross-Brown, Brian Stimpson

The use of point load test data by the authors to estimate rock mass cohesion is a very ingenious approach. It must be emphasized that this estimate is indeed only an estimate since the point load strength index employed to predict the uniaxial compressive strength (and subsequently predict the cohesion) is likewise only an estimate.

Jan 11, 1979

By Donald P. Richards

The use of point load test data by the authors to estimate rock mass cohesion is a very ingenious approach. It must be emphasized that this estimate is indeed only an estimate since the point load strength index employed to predict the uniaxial compressive strength (and subsequently predict the cohesion) is likewise only an estimate.

Jan 1, 1980

By T. M. Morris

The forces acting between a small rod, one end of which was made water repellent, adhering to a much larger air bubble in water were measured. An equation is deduced which correlates these forces and the influence of each force is discussed. The importance of the size of bubbles in a flotation cell is emphasized.

Jan 1, 1950

INTRODUCTION TO SAMPLING THEORY Before specifically discussing mineral sampling and sampling procedures, let us briefly consider broader and more universal concepts of modem sampling theory. A sample is de- fined as a representative part or a single item from a larger whole, being drawn for purpose of inspection or shown as evidence of quality. In modem theory the sample is a part of a statistical population whose properties are studied to gain information about the whole. The theory of sampling is built around the concept that if enough representative units of a larger overall population are selected without bias, the average value of the units will approximate that of the total population. Modem theory attempts to answer the question of how many samples are enough, given certain limits and constraints, and seeks to apply methods of sample selection and of estimation that provide, at the lowest possible cost, estimates that are precise enough for the purposes at issue. In order to meet these objectives the designer of a sample survey must rely heavily upon statistical theory. Statistics has been defined as the collection, presentation, analysis, and interpretation of numerical data. Statistical methods are primarily concerned with making valid inferences about a population based upon samples taken from the population. For most statistical applications, the total sample is in terms of number of items, attributes, or things; whereas mineral samples are usually in terms of weight or volume of mineral particles. Certain steps are involved in a well designed sample survey without regard to the particular field of application. Because the desired characteristics of an unmined mineral deposit can- not be known other than by sampling, we will consider these principle steps in terms of a mineral sample survey: 1) Clear definition of the objectives of the survey. In the case of mineral sampling this step is so apparent as to be almost ridiculous. However, it is surprising how often the overall objective of a sampling program is overlooked when decisions are made on a day-today basis. 2) Definition of the population to be sampled. The word population is used to designate the aggregate from which the sample is chosen. A sampling program may be designed to determine the grade of a single stope within a mine, the grade of a particular zone within a complex ore body, or the total value and extent of a mineral deposit. Since mineral sampling is usually done in phases, it is well to

Jan 1, 1980

By W. N. Best

This paper is not intended as a scientific discussion of the combustion of oil but is written from the standpoint of an operator who has the experience and qualifications necessary to guide others in producing the most economical results in the use of liquid fuels. Oil, in this paper, usually means petroleum or its products but incidental reference is made to other liquid and gaseous fuels, so that the term may be considered as referring to all liquid and gaseous hydrocarbons in comparison with solid fuels, as coal and wood. However, only a few of the principal factors in the use of oil as a fuel can be given. The present, and prospective, high price of coal is causing users of fuel to renew inquiry as to the merits of other forms of fuel for industrial purposes. Crude oil (petroleum) is proving to be one of the world's most valuable mineral resources. The recent discovery that oil underlies a considerable area of the United States, Mexico, and other parts of the world to a greater extent than was formerly believed and the large production of some of the wells in these areas shows the probable quantity of fuel oil that may now be available. Through the energy of Lord Cowdrey, who was one of the pioneers of the oil industry in Mexico, oil has been discovered in England; some prominent geologists believe that it may be found in quantity in Great Britain. For years, oil has been known to be of great value in the manufneture of metals. It has proved incomparable in forge shops, steel foundries, heat-treating furnaces, and wherever accuracy of temperatures is essential, or where a maximum output is desired as well as quality of metal. In some types of equipment, the output produced with oil as fuel is double that obtained with coal and at a reduction of 50 per cent. in the cost of the fuel. For example, in drop-forging plants, the metal is always waiting for the man when oil is used as fuel, whereas with coal, the man must wait for the metal to become sufficiently heated. It has only been since January, 1919, that the oil supply could be relied on for boiler service, owing to the war conditions and the inability to get oil tankers for the delivery of the oil from Mexico to Atlantic ports; but now a constant supply is assured, and many manufacturers are installing it in their power plants. The cost varies with the size of the

Jan 1, 1921

By D. A. Woodford

A number of observations have now been reported where the steady-state creep rate is apparently linearly dependent on the applied stress at high temperature and low stresses. This results in a creep rate greater than that predicted by extrapolation of high-stress data and has obvious practical implications. However, some of these observations are open to question. For example, the analysis by Harris and Partridge17 of the data of Greenfield et a1.18 was dependent on strain rates which, according to the original authors, were too low to be measured. Dr. Bernstein appears to have demonstrated a linear stress dependence at low stresses in two zirconium alloys. There are, however, a number of discrepancies in his treatment of the data and the subsequent theoretical analysis which require clarification. 1) It is incorrectly stated that steady-state conditions are revealed by a slope of unity on a plot of log i vs log (time). This objection is trivial if the author meant to say a slope of zero, although it is unclear how subsequent extrapolation was made to determine the steady-state creep rates at low stresses for the zircaloy-2. If the plot used was actually log c vs log (time), it is unlikely that a slope of unity would represent a constant creep rate. A plot of log (c - co) vs log (time), where c0 is the extrapolated intercept sf the steady-state creep rate on the strain axis, would have a slope of unity during steady-state creep. However, eo cannot be determined unless is is already known. 2) The author chooses to interpret his results based on the equation: where A, and B, are structure-sensitive parameters, Ql and Q, are the activation energies for the particular creep process, and n describes the sensitivity of the creep rate on stress. The first term represents a slip creep process and the second a diffusion creep process. However, it is stated later that "two distinct processes acting in parallel are involved". Eq. [I] surely represents two processes in series since each reacts to the total applied stress and t, is the sum of the individual creep rates. If the processes are acting in parallel, then the effective stress in each would be less than the applied stress. The component stresses would be given by sl + s2 = a but it is not clear how the magnitude of either, or the corresponding stress exponent, could be determined.

Jan 1, 1969

By Walter H. Bucher

THIS symposium is designed to lay the basis for a general discussion of the place of geophysics in the training of geologists. As there is danger that in the ensuing debate individual interests may be given emphasis out of proportion to their place, we shall do well to view the whole field of geological inquiry in order to see the problem in true perspective. THE NATURE OF GEOLOGICAL INQUIRY "Basic" and "Complex" Sciences It is convenient to divide all science into two major divisions, the basic and the complex sciences. The basic sciences separate out from reality such entities as "substances" and "movements," describe their behavior in terms of arbitrary units of measurement and derive from them by progressive abstractions concepts and patterns of behavior that exist between them, so-called general "laws" and "properties" of nature. The complex sciences, on the other hand, deal, with little or no abstraction, with those objects of reality that are accessible to man in the atmosphere, the hydrosphere, the lithosphere and the biosphere.† Their work comprises two types of inquiry. One is concerned with abstractions to the extent of dealing with types rather than individuals-that is, with such things as plants, animals, protoplasm; clouds, streams, glaciers; volcanoes and mountain ranges. It comprises the search for general properties and patterns of behavior or "laws" that characterize the objects and their reactions to each other. These properties and laws apply always, everywhere. They are independent of the stream of time. We may call the results of this sort of inquiry timeless knowledge. The other type of inquiry is concerned with the objects themselves-that is, with this animal and that plant; this river system and that mountain chain; this glacier and that valley. Like all concrete objects in nature, they are subject to change with the passage of time, especially when it is measured in years, centuries, eons. The characteristics by which we recognize them -indeed, their very existence are dependent on their position at this point in the stream of time. This we may call time-bound knowledge. The so-called descriptive sciences are all bound to the past of which the objects of their study are the product and through which alone their present properties can be understood. They are historical sciences. This obvious fact is easily overlooked, which leads to serious misunderstanding, as we shall see later. Dynamic Geology With this broad picture in mind, let us now examine the nature of geological inquiry, defining, for the purposes of this discussion, geology as the science of rocks. Air is not a rock; water is. Meteorology and climatology are, correspondingly, gen-

Jan 1, 1941

By Eugene C. Robertson

INTRODUCTION A direct proportionality between the observed displacement of a fault and its thickness of breccia and gouge has been proposed recently (Robertson, in press). To validate this finding, an explanation of the mechanics of continuous breccia formation is needed and is offered in this paper. A summary of evidence for the finding will show why an explanation is needed. The correlation between fault displacement [d] and accompanying breccia- plus-gouge thickness [t] seems to be linear and reasonably well established over 6 orders of magnitude, with a range in [d] from 1 mm to 1 km, on a trend of [d/t]= 100, shown in Figure 1. Most of the points are for faults observed underground in mines. The [d] – [t] relation is limited to normal and reverse faults, that have a flat to steep dip and a displacement less than 5 km. It is not applied to large strike-slip and low-angle overthrust faults, whose displacements and breccia thicknesses are widely variable and uncertain. Undisplaced jointed rock is not included in the thickness measurement. A complete description of sources and analysis of the data is given in Robertson (in press). One would intuitively expect that continued movement on a fault would grind up the previously formed breccia and gouge and not produce any more, but the evidence (Fig. 1) indicates otherwise. A physical model to explain continuous formation of gouge and breccia from the wall rocks can be obtained from laboratory experiments on friction.

Jan 1, 1982

By Ralph Sweetser

THE present state of iron blast-furnace practice is metallurgical rather than mechanical; the tend-ency is toward intensity rather than toward ex-tension. The engineers have built blast furnaces big enough and strong enough, and have furnished accessory equipment ample and accurate enough for the present state of the art, but the metallurgical side has been too much neglected; the metallurgist, rather than the engi-neer, is now the man on whom the present and future progress in iron blast-furnace practice depends. The mining engineer has produced great tonnages of iron ores, and has kept ahead of the demands for quantity; now the metallurgist is improving the chemical and physical qualities of this product by ore-dressing and other forms of beneficiation. For a generation or more, the principles of mechanics have had most influence in the advancement of iron blast-furnace practice; atten-tion now is given more to the principles of metallurgy, chemistry, and ore-dressing. This metallurgical progress is taking place inside and outside the blast furnace. The two great determining factors of the inside operation are the slag, and the rate of combustibility of the coke. Outside the fur-nace, the progress is, and will be, along the lines of more careful mixing of ores and iron-bearing materials, in the sizing and washing of limestone, and in the char-acter and structure of byproduct coke.

Jan 3, 1922

Discussion of the paper of E. J. Hall and C. W. Drury, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 78, June, 1913, pp. 1059 to 1066. A. M. SMOOT,* New York, N. Y. (communication to the Secretary +) :-The nails method is given in many text books on assaying as a standard method for gold or for gold and silver in ores. It appears to be taught in the laboratories of technical and scientific schools as a standard method, and to some extent it is used by assayers in actual practice, although the class of ores to which it may be applied is limited to those free from reducible metallic compounds, the metals of which would enter the lead button. The experiments of Messrs. Hall and Drury show the inaccuracy of this rnethod for silver, in heavy sulphides, but not so clearly the short-comings with regard to gold. It seems certain that low silver is caused by the solubility of silver in iron-alkali sulphide as compared with its solubility in molten lead; that is, silver is distributed between iron-alkali sulphide and metal in the charge in proportion to solubility at the particular temperature of the fusion. Lead is a fixed quantity in these assay charges, but iron-alkali sulphide increases with increased sulphur, so the more sulphur in the charge, the lower the silver results.

Jan 11, 1913