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By Thomas. B. D.

GRAVITY concentration is a general term designating processes for separating and sorting granular material by means of forces that depend on the density, size and shape of the particles. When these forces are applied to the particles the latter are caused to move, those of a given density along one path and those of a different density along another, until ultimately they are sufficiently separated to be removed from the operation of the process. The forces producing this separation are in general complex and, unfortunately, no completely rigorous analysis of them has as yet been devised. The science of the hydrodynamics of viscous fluids deals with , the little that is known about the problem. Every observer of nature is familiar with the fact that an object moving in a fluid encounters a force of resistance. We have only to walk against a brisk wind or stir a cup of coffee, or observe the slow fall of a grain of sand in water, to experience directly the fact that such forces exist. The exchange of force between an object and a fluid in which it is moving operates on the fluid as well as on the object. Thus a sailboat may be set in motion by the force exerted by the wind on the sail; but the sail also deflects the wind-furthermore, the water in which the boat floats is set in motion by the force exerted by the boat as it cleaves through the water, The wind is thus enabled to do work on the water through the intermediary of the boat. In general, an object moving through a fluid encounters a force that opposes the motion and also acts to change the motion of the fluid. In gravity concentration we are dealing with this force of resistance acting on the granular particles that are to be separated. Furthermore, the motion induced in the fluid by a particle will in turn affect the motion of a neighboring particle. This effect will be reciprocated and in consequence there will be an exchange of forces between all the particles in the material. These effects are complex and the most that can be expected is that we may be able to determine in a qualitative way how they operate. In gravity concentration, then, the following types of forces may be distinguished as acting on the particles:

Jan 1, 1943

By O.W. Ellis

Recently there has been a considerable revival of interest in the effects of the various elements commonly added to brass for the purpose of increasing its strength. For many years the work of Guillet2 alone gave reliable information in this regard. Even today his determinations of the coefficients of equivalence of the various elements relative to zinc in brass are those universally employed in industry. This is so because these coefficients have stood the test of time—their substantial correctness has been proved in almost universal practice. It is not our intention to discuss here these coefficients or their use. Rather do we wish to emphasize the need for further systernatic studies of the mechanical properties of the ternary systems of copper, zinc, and other individual elements. Since Guillet published the results of his first investigations Millington, 16 Smalley33 and Thiband 45 have added somewhat to our information. In general they have confirmed the findings of Guillet, which may be stated in the following rather general terms: 1. The addition of aluminum to the 70:30 and 60:40 brasses progressively increases their hardness and strength and reduces their ductility and resistance to shock. 2. The addition of small amounts of iron to a 60:40 brass improves its strength without affecting its ductility. 3. The addition of small amounts of manganese to a 60:40 brass causes a progressive increase in its strength and reduction in its ductility. A considerable amount of information has been amassed in regard to the effect of nickel on brass (9, 22, 41) which it is unnecessary to refer to here, in view of the scope of this paper. The situation in regard to these alloys in 1926 was very clearly stated by an anonymous writer,47 in The Metallurgist of February of that year, whose remarks were so to the point that they are well worth quoting: It will he seen that there are still large fields remaining to be studied in each of these systems (those of the aluminum, iron, nickel and manganese brasses) before our knowledge is adequate. When we come to the more complicated systems the position is even less satisfactory, and on account of the very incomplete nature of the work which has been

Jan 1, 1929

By O. W. Ellis

Recently there has been a considerable revival of interest in the effects of the various elements commonly added to brass for the purpose of increasing its strength. For many years the work of Guillet2 alone gave reliable information in this regard. Even today his determinations of the coefficients of equivalence of the various elements relative to zinc in brass are those universally employed in industry. This is so because these coefficients have stood the test of time—their substantial correctness has been proved in almost universal practice. It is not our intention to discuss here these coefficients or their use. Rather do we wish to emphasize the need for further systernatic studies of the mechanical properties of the ternary systems of copper, zinc, and other individual elements. Since Guillet published the results of his first investigations Millington, 16 Smalley33 and Thiband 45 have added somewhat to our information. In general they have confirmed the findings of Guillet, which may be stated in the following rather general terms: 1. The addition of aluminum to the 70:30 and 60:40 brasses progressively increases their hardness and strength and reduces their ductility and resistance to shock. 2. The addition of small amounts of iron to a 60:40 brass improves its strength without affecting its ductility. 3. The addition of small amounts of manganese to a 60:40 brass causes a progressive increase in its strength and reduction in its ductility. A considerable amount of information has been amassed in regard to the effect of nickel on brass (9, 22, 41) which it is unnecessary to refer to here, in view of the scope of this paper. The situation in regard to these alloys in 1926 was very clearly stated by an anonymous writer,47 in The Metallurgist of February of that year, whose remarks were so to the point that they are well worth quoting: It will he seen that there are still large fields remaining to be studied in each of these systems (those of the aluminum, iron, nickel and manganese brasses) before our knowledge is adequate. When we come to the more complicated systems the position is even less satisfactory, and on account of the very incomplete nature of the work which has been

Jan 1, 1929

By Gerard Matthes

WITHIN the last three years, aerial mapping has made wonderful progress. Its three sources of development in North America may be enumerated as follows: (1) The work of the U. S. Army Air. Service and Corps of Engineers at the McCook Experimental Field, Dayton, Ohio. This is generally regarded as the backbone of this class of endeavor in the United States. (2) In Canada, a great deal has been accomplished in a practical way by methods that have not even been tried out in the United States. Under the leadership of the late Doctor Deville, the Dominion Land Surveyors have turned out reconnaissance maps of large areas at very, small cost. (3) Private capital has contributed a great deal toward development of aerial mapping in a practical way in the United States. Prominent in this regard stands the Fairchild Aerial Surveys, Inc. which has spent large sums in research and development work, especially in the construction of aerial cameras. Its camera is, at present, the official camera of the U. S. Army and Navy Air Services, also, of the Canadian and Brazilian governments. Aerial photographic surveying is a flexible process and adapted to a variety of uses. To date, it has proved. of direct practical value for engineering projects such as reservoir and power transmission surveys, railroad location, drainage, harbor front studies; also, for many commercial purposes, tax assessment, city planning, forest surveys, and lawsuits. In a few instances, aerial photographs have been used successfully by geologists as base maps on which to record field observations, thereby dispensing with pacing and compass surveys. There is reason to believe that, eventually, the aerial map will find wide application in the work of geologists. The reason for advancing this opinion is that aerial maps have, in other fields, proved more complete as regards detail than maps made by standard processes of surveying and drafting, and often are more accurate than the latter. At the present time, five distinct uses are being made of aerial photographs: There is the "oblique" photograph taken at an angle with the horizon; it is used extensively for illustrations in newspapers, magazines, and advertisements. Also, for reconnaissance purposes, it has been found of great practical value. For illustrating reports of engineers and geologists, it offers many obvious advantages. In the Canadian Surveys, maps have been compiled from oblique photographs.

Jan 3, 1925

By O. N. Carlson, H. A. Wilhelm, H. E. Lunt, J. M. Dickinson

On the basis of data obtained from microscopic examination, melting observations, cooling curves, X-ray analyses, and resistance measurements, phase diagrams have been proposed for the Th-Cb and Th-Ti alloy systems. Both are simple eutectic systems and have no terminal solid solubility or intermediate phases. The eutectic between thorium and columbium occurs at a composition of about 8 wt pct Cb and a temperature of 1435°C. The Th-Ti eutectic occurs at 1190°C at the composition 12 wt pct Ti. No change was observed in the transformation temperature of thorium in either system or in the titanium transformation. RECENT study of thorium and its alloys has been promoted because of the possibility of employing this metal in nuclear reactors. Their corrosion resistant properties, nuclear characteristics, and high melting points put columbium and titanium among the many metals being employed in the study of thorium alloys. Since a knowledge of the phase relationships would be important in the application of such an alloy, investigations were undertaken to propose phase diagrams for the Th-Cb and Th-Ti systems. Experimental Procedures Thorium metal sponge was specially prepared for use in this investigation. Carbon in a quantity less than 0.04 wt pct was the principal impurity. There was also less than 0.01 pct each of iron, calcium, zinc, aluminum, and nitrogen in the thorium. Columbium, both as a powder and sheet metal, was obtained from the Fansteel Metallurgical Corp. The manufacturer's specifications indicated that the metal contains less than 1 wt pct total impurities. An analysis of the metal showed approximately 0.18 pct C in the powder and less than 0.05 pct C in the sheet. The titanium used was commercial sponge, reported to be 99.5 pct Ti. An analysis showed that this metal contained 0.2 pct Fe. Preparation of Alloys—Since the metals used in this investigation are reactive and might become contaminated on melting in a refractory crucible, the alloys were prepared by arc melting. The titanium sponge was employed in the form of small lumps while the columbium additions were made either as pressed pellets of powder or as clippings from sheet. The alloying material and the thorium sponge were melted together under argon in conventional arc melting equipment employing a tungsten electrode and a water cooled copper crucible.

Jan 1, 1957

By M. L. Millican

The objective of this study has been to develop a method of log interpretation in the Delaware sand whereby the effects of the shale contained within the sand can be recognized and accounted for in a quantitative solution for porosity and water saturation. Both theoretical and empirical considerations are discussed. A simplified interpretation chart is presented which provides a means of amending the conventional porosity resolution of the Sonic log to compensate for the presence of shale. The amount of shale within the sand and its degree of lamination may be inferred from a calibrated gamma ray log. The resulting porosity value may then be used in conjunction with a knowledge of the formation resistivity to determine water saturation. Of added interest, particularly in the Delaware sand, is an approximation of permeability which may be derived empirically from the simplified chart. The discussion is illustrated by field examples. INTRODUCTION The performance of the Sonic log in defining the porosity fraction in clean, consolidated formations is well known, particularly in sandstones that are well compacted and free of shale. An approach to Sonic log porosity determination in shaly sands has been recently developed.' This method involves correcting the Sonic log readings by means of an a factor, where a is the ratio of the pseudo-static SP to, the static SP, and is a function of the amount of shale present. This method is dependent upon a contrast between the salinities of the drilling fluid and the connate water in the formation, inasmuch as this contrast produces the SP effect. In wells drilled with salt mud, the contrast, and with it the means of obtaining the a correction, disappear. In the Delaware basin, the large majority of rotary wells drilled to the uppermost sands of the Bell Canyon group employ salt mud as the drilling fluid. These sands have been the objective of most of the drilling exploration in the basin to date. A comparison of porosity values in these sands, as determined by core analysis, to Sonic log readings has indicated that a correction for the shaliness of the sand is needed. In the absence of an SP curve to determine the correction factor, the porosity resolution of the Sonic log in these sands has been questionable.

By C. W. MacGregor

THE observation of the flow layers, or Lüders' lines, produced in mild steel when it is stressed into the plastic range often provides considerable useful information for the study of the fundamental mechanism of the plastic flow of metals. It is a commonly observed fact that as soon as the upper yield point in a mild-steel tensile-test bar is passed, an unstable condition develops in the equilibrium, the load on the testing machine drops and if the surface of the bar contains a thin mill scale, the latter begins to flake off rapidly along certain "lines." These "lines" are in reality traces of wedge-shaped flow layers and are formed by the intersection of the surface of slip and the surface of the bar. The average plane of the flow layer itself has been found by various experimenters to be inclined at an angle of approximately 45° to the axis of the test bar. In a body of more complicated shape stressed in possibly a different man-ner, the tangent planes to the flow layers at each point seem in many cases to be inclined at an angle of about 45° to the principal stress direc-tions at the point. As examples of the latter may be mentioned the logarithmic spirals obtained when a rivet hole is punched in a thin plate, or when a tube is subjected to internal pressure only, etc. Hence if the flow layers are observed from an experiment, the shear-stress trajectories -the curves indicating the directions of the maximum shearing stresses in the body-may then be approximately determined. Since the latter curves form an orthogonal family inclined at 45° to the principal stress directions, the family of principal stress trajectories, or the curves indicating the directions of the principal stresses, may be thus obtained. Although the discontinuous type of stress-strain curve at the yield point is commonly observed with test bars of mild steel, more recent experiments have shown that this is by no means the only material exhibiting this interesting phenomenon. A similar effect has been observed in zinc and cadmium crystals, by Becker and Orowan;1 in duralumin and other aluminum alloys, by Dawidenkow,2 Elam,3 Fell, and others; in copper and copper-alloy crystals, by Elam;5 in brass by Elam;5 in brass wires by deForest;6 in higher carbon steels, tungsten steel, and

Jan 1, 1939

By J. T. Eash, N. B. Pilling

As a group, the alloys of iron, nickel and carbon are, in application, one of the most versatile of the ferrous alloy family, and while many investigations have been made of their properties and structure only a few attempts have been made to show the microstructural relation over a wide range of composition. It is necessary at once to be clear about the kind of structural relation with which we are concerned. The equilibrium diagram provides quantitative data regarding structural make-up and its variation with temperature, but equilibrium structures often are far different from the technologically significant ones. This is particularly true of steels and cast irons, and some of the most important components of their structure may have no place in the diagram of equilibrium. The fugitive phases that result from transformation are dealt with in a highly detailed and descriptive manner in the S-curves originated by Bain. The present effort lies in a still different field, which is to portray the relation between sweeping changes in composition and in resultant structure, under controlled but nonequilibrium conditions of thermal treatment. The Guillet1 diagram presented in 1903 was the initial attempt at such a correlation and frequent references to this diagram can be found in the literature even though later work has shown it to require considerable modification. Kase2 published in 1925 a diagram that was based upon observations of furnace-cooled melts. At low carbon contents this diagram agreed fairly well with experience in showing pearlite to exist in alloys containing up to 6 per cent nickel, and completely austenitic steels at 24 to 28 per cent nickel. At high carbon contents, however, irons were indicated as being martensitic at around 2 per cent nickel and austenitic at 12 per cent nickel; these interpretations are open to serious question. Based upon experience with steels and cast iron, Wickenden3 suggested a diagram that agreed fairly well with Kase's in the steel range but which presented a wide departure from it in the higher-carbon, high-nickel regions. In its broad picture, the Wickenden diagram is an approach to "practical" structures. [ ] Reference may be made at this point to the efforts of Marshy to construct an iron-nickel-carbon equilibrium diagram by the coordination of scattered data, which are described at length in the monograph cited. None of these preceding attempts has appeared to meet the need for an exposition of the structural sequence that is encoun-

Jan 1, 1942

By James Norman, O. C. Ralston, John Dasher

MOST mineral products are used in the finely divided state, but some are sold in larger sizes. Coal, gravel, metallurgical fluorspar, phosphate rock, hematite, chromite, and other products are sold in sizes coarser than can be treated by many mineral-dressing methods. Gravity separation of coarser sizes by log washing and jigging is probably as ancient as any process now in use. The performance of jigs on a feed with sufficient difference in density of the minerals is excellent, but many families of minerals are too similar in density to be separated effectively by this method. The use of heavy suspensions of fine solids to separate coarse coal from bone and slate has been in use for some years. This separation by sink-and-float was limited until recently to light minerals. Development of galena and ferrosilicon as suspension media, by Minerals Beneficiation, Inc., at Mascot, Tenn., Pitcher, Okla., and Crosby, Minn., under patents granted during and since 1938, has permitted excellent results to be obtained on minerals of very similar densities up to 3.3. This process has been put in the hands of American Cyanamid Co. for exploitation, and further research now in progress may increase the density of suspension obtainable so that separation, at a density of 4,0 may be practicable before this is published. The Huntington-Heberlein dense-medium process, developed in England, is also being commercialized in the United States by Sink and Float Corporation. Du Pont has developed a sink-and-float separation using halogenated hydrocarbons as parting liquids; at this writing, the method is used commercially only on coal but has been successful in the pilot plant on many other minerals using tetrabromethane at densities up to 2.95. While these processes were being developed to extend the range of separation by difference in density to the coarser sizes, the Bureau of Mines was engaged in developing a process that will extend the range of separation by difference in wettability up to 2-in, size. War work has pushed aside its further development indefinitely. The results are published here with the hope that some use may be suggested that will justify post-war development, and so that readers that may be able to make immediate use of the scheme may have the information. EARLIER WORK It has been known since the time of Herodotus (B.C. 484(?)-425) that water-repellent particles will adhere to sticky surfaces. That early historian reports the

Jan 1, 1942

By Richard McCaffery

THERE has been some discussion among blast-furnace operators regarding the relative merits of tuyeres of the converging type and tuyeres designed in an attempt to produce a diverging jet of air. An article1 on Progress in German Blast Furnace Practice indicates the interest in this subject abroad. This article illustrates a diverging type of tuyere which is shown here in Fig. 1A. The design appears to be rather poor as regards known properties of air flow. The adoption of this. tuyere, the article states, resulted in a decrease of blast pressure of about 4 lb. per sq. in. and an increase of the output of the furnace. If the improvements mentioned are due entirely to the change in tuyere design, the subject of tuyere design seemed worthy of investigation and this paper is a report of such work. Because of the gain in efficiency brought about by the use of a diverging tuyere in the German plant, it was thought desirable to investigate the shape of the air streams issuing from various-types of tuyeres to ascertain whether the gain was due to the tuyere itself or to the distribution of the air in the furnace. Since it is difficult to do experimental work on a full-sized furnace, or even on full-sized tuyeres, and because of the equipment available for the work, it was decided to carry out the work on scale models of tuyeres. Therefore, in this work, single tuyeres were used and the blast discharged into the atmosphere. The shape of the air stream was determined by means of a Pitot tube suitably supported in the air stream at various positions. The air was. furnished by a Roots blower driven by a 10-hp. direct-current motor having field control, and capable of discharging 250 cu. ft. per min. with a pressure on the discharge of 4 in. of mercury. A modern blast furnace with 21-ft. hearth requires about 50,000 cu. ft. per min. of free air at from 16 to 23 lb. per sq. in. pressure, depending upon the type of burden. This pressure is the total pressure required to force the air through the burden and through the tuyeres. Upon computation the pressure drop through the tuyeres is about 1 to 2 lb. per sq. in. By making the tuyeres to a one-fifth scale, and by using a pressure of 1.5 in. of mercury, the shape of the air streams should be

Jan 1, 1931

By E. A. Smith, E. R. Parker

METALLURGISTS and engineers have always been interested in the mechanism of high-speed deformation because metals are rapidly deformed in various applications and manufacturing processes. The deformation of metals by impact loads has recently engaged the attention of a number of investigators. Many of their results have not been disclosed but some of the published investigations1-8 have shown that the tensile strength, yield strength and elongation generally increase with increasing strain rate. The investigation reported herein is an attempt to determine the reason for this increase in strength and elongation. Single-crystal copper specimens were broken in tension at impact velocities up to 100 ft. per sec. The distribution of slip bands in the fractured crystals was found to depend upon the strain rate. In the bars broken at high speeds, the slip bands appear to be more numerous. This might account for the higher strength as well as the greater elongation. EXPERIMENTAL PROCEDURE Single crystals of copper (approximately 99.98 per cent) were made in graphite molds by the conventional method of lowering the mold out of the hot zone of a hydrogen furnace at a rate of one inch per hour. Solidification progressed from the bottom upward, forming a single crystal. The crystals were about 0.30 in. in diameter and 4 in. long. They were made into test bars by sliding threaded steel bushings over each end of a crystal and then flowing silver solder between the crystal and the bushing. The inside diameter of the bushings was slightly greater than the diameter of the crystals, to allow space for the silver solder. The bushings were placed so that the gauge length of the crystals was one inch. The assembly is shown in Fig. I, with two views of a fractured crystal. Annealed polycrystalline copper bars of similar shape were machined from solid stock. X-ray measurements were made on all single crystals to determine their orienta¬tions. The results are shown in Fig. 2, where the location of the axis of each specimen is indicated on a standard projection. The bars were broken in a commercial variable-velocity tension im¬pact machine, which has been described in detail elsewhere.7,8 The stress and strain were recorded by means of wire strain gauges and a special commercial oscillo-raph, also described in detail elsewhere.9,10 The equipment and method can be briefly described as follows. The impact machine consists of a motor-driven flywheel containing a two-pronged hammer. This hammer is held retracted in the flywheel

Jan 1, 1944

By Hugh S. Spence

In the winter of 1941-42, muscovite mica was discovered by a young prospector, Justin Purdy, in the township of Mat-tawan, Nipissing District, Ontario, a few miles north of the small settlement of Eau Claire, which lies on the main Transcontinental Highway (No. 17) between Mattawa and North Bay. Muscovite had been known for many years to occur in the general Mattawa region, and various small efforts at production had previously been made by individuals working scattered deposits in the area. These minor activities, however, had never led to production of any consequence or the discovery of any important mica bodies. The Purdy finds were made in a heavily timbered, mountainous area lying about three miles north of the low-lying settled land along the highway, and in a section not hitherto prospected. The mica taken by Purdy and two partners from surface outcrops proved so remarkable in point of size of trimmed sheets that the find attracted considerable attention, and the area surrounding the three claims taken up by the prospectors was quickly blanket-staked by various interests. Though a number of other mica-bearing pegmatite dikes were found later on these stakings, none proved as rich as those on the original Purdy ground; very little commercial mica was obtained from them and attempts to develop them were short-lived. Purdy and his partners sold their initial production to dealers in Ottawa and Hull, where the Canadian mica industry long has centered. Young Purdy, unfortunately was killed in a motor accident in the early summer of 1942. His father continued mining operations for a few months and produced and sold a considerable amount of mica. In October 1942 the Purdy holdings were acquired by lnspiration Mining and Development Co. of Amos, Quebec, which had been active in staking in the area. This company formed a subsidiary, Purdy Mica Mines, Limited, to develop the property. Under the energetic management of Joseph R. Norrie, rapid progress was made, and production soon attained important proportions. Realizing from the outset the unusual character and potential value in the war effort of the Purdy discovery, the Metals Controller, Department of Munitions and Supply, at once arranged with the Department of Mines and Resources for an official geological report on the area, and also drew the attention of the War Production Board in Washington to what seemed likely to prove a highly important source of strategic-quality mica. Officials of WPB were sent up in the Summer of 1942 to inspect the property, and so impressed were they with the possibility that it might become of high

Jan 1, 1948

By Hugh S. Spence

In the winter of 1941-42, muscovite mica was discovered by a young prospector, Justin Purdy, in the township of Mat-tawan, Nipissing District, Ontario, a few miles north of the small settlement of Eau Claire, which lies on the main Transcontinental Highway (No. 17) between Mattawa and North Bay. Muscovite had been known for many years to occur in the general Mattawa region, and various small efforts at production had previously been made by individuals working scattered deposits in the area. These minor activities, however, had never led to production of any consequence or the discovery of any important mica bodies. The Purdy finds were made in a heavily timbered, mountainous area lying about three miles north of the low-lying settled land along the highway, and in a section not hitherto prospected. The mica taken by Purdy and two partners from surface outcrops proved so remarkable in point of size of trimmed sheets that the find attracted considerable attention, and the area surrounding the three claims taken up by the prospectors was quickly blanket-staked by various interests. Though a number of other mica-bearing pegmatite dikes were found later on these stakings, none proved as rich as those on the original Purdy ground; very little commercial mica was obtained from them and attempts to develop them were short-lived. Purdy and his partners sold their initial production to dealers in Ottawa and Hull, where the Canadian mica industry long has centered. Young Purdy, unfortunately was killed in a motor accident in the early summer of 1942. His father continued mining operations for a few months and produced and sold a considerable amount of mica. In October 1942 the Purdy holdings were acquired by lnspiration Mining and Development Co. of Amos, Quebec, which had been active in staking in the area. This company formed a subsidiary, Purdy Mica Mines, Limited, to develop the property. Under the energetic management of Joseph R. Norrie, rapid progress was made, and production soon attained important proportions. Realizing from the outset the unusual character and potential value in the war effort of the Purdy discovery, the Metals Controller, Department of Munitions and Supply, at once arranged with the Department of Mines and Resources for an official geological report on the area, and also drew the attention of the War Production Board in Washington to what seemed likely to prove a highly important source of strategic-quality mica. Officials of WPB were sent up in the Summer of 1942 to inspect the property, and so impressed were they with the possibility that it might become of high

Jan 1, 1948

By L. F. Terry, H. K. Ihrig, D. J. Sabin, Ralph E. Davis

This paper presents the results of a study of the comparative values of the several fuels commonly used by industrial plants. It shows that the energy actually recovered from any fuel and turned into useful work is dependent upon several factors: (1) the total energy available in the fuel, (2) energy losses resulting from combustion reactions and (3) energy losses dependent upon the mechanics of the firing operation. The chemistry of combustion and the losses resulting therefrom are discussed. The Advantages and disadvantages of the several mechanical methods of firing and the resulting heat losses in each are developed. Data obtained from several typical fuel operations, where careful records have been maintained, are presented to show that the practical results in the actual operation are in harmony with the theoretical results developed in the earlier part of this paper. Water power and solid, liquid or gaseous fuels are at present the only commercial sources of energy. The economic utilization of any one of them depends, in the final analysis, on the cost of energy per unit of finished product to which the energy is applied. The location of the plant utilizing the particular fuel chosen is a large factor in the original choice. The cost per unit at its original natural source, or even in its delivered form, is not always the final measure of its worth. The use of electricity as a source of energy illustrates this to the extreme. Electric current produced from water power is very cheap in certain localities. In Norway, current is sold as low as ½0# per kw-hr., while in dry cells it costs as much as $10 per kw-hr. Yet the sale of dry cells is a large business. The selling price of gas also varies widely. In some localities natural gas for the manufacture of carbon black sells for as low as $0.02 per million British thermal units, while artificial gas for domestic purposes sells for as high as $6 per million B.t.u. Obviously the cost per unit of energy is not the final determining factor in its purchase. Any discussion of the economic utilization of fuels must include costs in relation to the units of finished material manufactured. In large central power generating stations, this is the over-all cost per kilowatt-hour, and in ceramic firing the cost per unit of finished product of a certain quality is the criterion of economic utilization.

Jan 1, 1931

We have seen that the first coal development in Pennsylvania was in the Pittsburgh bed in the southwestern corner of the state. The next mining, in point of time, was done in Clearfield County along the West Branch of the Susquehanna River, but the amount of mining done was quite small for a number of years and was soon exceeded by that from the area north of the Susquehanna River in Tioga, Bradford and Lycoming Counties, which will be considered now. It is claimed that coal was first noticed in Tioga County, in 1792, by Robert and Benjamin Patterson who were leading a party of settlers from Williamsport to southern New York, and while clearing a road near the site of Blossburg, found coal, which was said to be good. About 1815 David Clemons made an arrangement with Aaron Bloss, owner of the land, to work some of the coal and hauled the first load down the river to Painted Post, N. Y., as there were no available markets in his own state. Smiths found it an excellent fuel and apparently he found a ready market for the small amount he could transport by wagons and sleighs. As wood began to become scarce around the towns in New York State, the knowledge of the coal deposits in the mountains at the head of the Tioga River attracted attention to the field and the necessity, for means of transportation from it. Some coal had been floated down the river, but navigation was uncertain and dangerous. In 1827 an iron plant was built, and to ship its product and coal, it was proposed to build a canal along the river to reach Corning, N. Y. A company had been chartered in 1826 in Pennsylvania to "make a navigable canal or slack-water navigation" to the state line and coal was shipped on rafts of logs, both being sold, during highwater. In 1828 the company was authorized to build a railroad instead of a canal, and in September 1840, the railroad was completed from Corning to Blossburg.1 That some coal from Pennsylvania had been reaching southern New York towns prior to the improved means of transport is shown by the report of a committee to the New York Assembly: "the bituminous coal has been brought to us either from Great Britain or from that part of our own country which borders on, and lies west and south of the Susquehan-

Jan 1, 1942

By R. S. McCaffery, D. E. Krause

There has been some discussion among blast-furnace operators regarding the relative merits of tuyeres of the converging type and tuyeres designed in an attempt to produce a diverging jet of air. An article1 on Progress in German Blast Furnace Practice indicates the interest in this subject abroad. This article illustrates a diverging type of tuyere which is shown here in Fig. 1A. The design appears to be rather poor as regards known properties of air flow. The adoption of this tuyere, the arlicle states, resulted in a decrease of blast pressure of about 4 Ib. per sq. in. and an increase of the output of the furnace. If the improvements mentioned are due entirely to the change in tuyere design, the subject of tuyere design seemed worthy of investigation and this paper is a report of such work. Because of the gain in efficiency brought about by the use of a diverging tuyere in the German plant, it was thought desirable to investigate the shape of the air streams issuing from various types of tuyeres to ascertain whether the gain was due to the tuyere itself or to the distribution of the air in the furnace. Since it is difficult to do experimental work on a full-sized furnace, or even on full-sized tuyeres, and because of the equipment available for the work, it was decided to carry out the work on scale models of tuyeres. Therefore, in this work, single tuyeres were used and the blast discharged into the atmosphere. The shape of the air stream was determined by means of a Pitot tube suitably supported in the air stream at various positions. The air was furnished by a Roots blower driven by a 10-hp. direct-current motor having field control, and capable of discharging 250 cu. ft. per min. with a pressure on the discharge of 4 in. of mercury. A modern blast furnace with 21-ft. hearth requires about 50,000 cu. ft. per min. of free air at from 16 to 23 Ib. per sq. in. pressure, depending upon the type of burden. This pressure is the total pressure required to force the air through the burden and through the tuyeres. Upon computation the pressure drop through the tuyeres is about 1 to 2 lb. per sq. in. By making the tuyeres to a one-fifth scale, and by using a pressure of 1.5 in. of mercury, the shape of the air streams should be

Jan 1, 1931

By R. W. Raymond

Franklin Guiterman was born March 7, 1856, in Cincinnati, Ohio, where his father, William Guiterman, was at that time engagcd in the wholesale dry-goods business. Both of his parents were natives of Bavaria, but the inspiration of America was upon them, as they gave to their son a peculiarly American name, symbolizing thrift, individualism and scientific knowledge. Franklin Guiterman received his general education in the grammar schools and the Hughes High School of Cincinnati. He finished the latter course in the early 70's of the last century, when the great demand for mining and metallurgical experts in this country naturally led his parents to direct his further studies in that direction. Accordingly, he went to Europe, and studied at the Royal Saxon Mining Academy of Freiberg, where he completed the course in 1877, at the age of 21, and returned to the United States to engage in mining and metallurgical practice. Going to Colorado, he became assayer for the Terrible mine, at Georgetown, and in 1878, for the Little Chief mine at Leadville. The position of assayer, particularly at that period and in that region, was the door to much valuable knowledge of mines and ores. Besides learning the nature and value of the different classes of ore from the mines of his own company (if he was employed by a company) the assayer, had the first chance, through his outside customers, of seeing and testing the specimens brought by prospectors, and thus learning of important new discoveries. Moreover, if he possessed metallurgical knowledge, he might advance to the position of a metallurgical manager. Guiterman stayed in Leadville four years, and during that period was assayer or chemist for several different companies. Then for about a year he superintended copper-mining operations at Hartville, Wyo. In 1884, he had charge of sampling works at Silverton, colo.—an admirable opportunity for gaining wide knowledge of the varied ores of the San Juan country. In 1885, he was Superintendent of the Mingo plant of the Pennsylvania Lead Co., at Sandy, near Salt Lake City, Utah. The foregoing list of employments, each occupying not more than a year, certainly looks like the history of a rolling stone, gathering no moss. But the cause of these frequent changes was not inefficiency in each new position. In that time and period, a man who lost his place for such a reason was not likely to get another in the same neighborhood might away. And as for gathering "moss," the kind of "moss" that

Jan 1, 1918

GEORGE F. COMSTOCK (author's reply to discussion*).-Mr. Thum's description of the effects of butt welding and spot welding on the micro-structure of steel are interesting and timely. The speed with which the changes noted by Mr. Thum must take place is indeed remarkable, but the writer has noted a similar very rapid diffusion of carbide in annealing a t a rather high temperature certain samples of soft sheet steel containing massive cementite segregated on a small scale. The massive cementite in such steel can be dissolved and distributed very quickly if the proper temperature is attained. Mr. Thum's explanation of the structure he found in the spot welds seems entirely reasonable, but the mystery of the decarburized material in the butt weld is one that might well be the subject of further research. The possibility of decarburization by air ,might perhaps be worthy of a little more consideration than he gives it, for the oxides formed would be gaseous on account of the presence of carbon, and hence not visible in the microscope, and the effect of the pressure might be to squeeze the carbon oxides, which would normally form blow-holes, out of the metal or possibly into such small volumes as not to be noticed The removal of carbon by liquation and squeezing into the fin would be an effect similar to the "bleeding" of a steel ingot that is rolled while the center is still liquid, giving a soft low-carbon interior in the finished section while the segregate was removed in cropping the pipe. This effect in Mr. Thum's butt welds could, however, only be obtained if the weld was heated to near the melting point of the steel, and if the carbon was considerably segregated in the bars at the start, for the first effect of the high temperature would be to promote diffusion rather than the contrary segregation and Equation. It is gratifying to learn from Dr. Ruder's remarks that his researches have resulted in no disagreement with the few points brought out by the writer's experiments. In addition to the three forms in which nitrogen may occur in iron that he mentions, it would seem that a fourth form is often found; This is apparently a eutectoid, like pearlite, and sometimes almost as coarse as the massive cementite seen in soft steel sheets that have been annealed for a long time. One of the things needed in the metallographic study of steel is an etching reagent that will distinguish definitely between nitride in this form and the more common pearlite or cementite.

Jan 6, 1919

SULPHUR is a very well known mineral and apparently is produced in many places. It is engendered from an unctuous earthy and powerfully hot substance so that it is considered among experienced workers to bear a resemblance to the element of fire. This is called by these same men the masculine seed and the prime agent of Nature in the composition of metals. Because of its great dryness and heat it has, as experience shows, affinity with fire, which is easily introduced in it when brought near. And once introduced the fire is quenched only with difficulty before its unctuousness is wholly consumed. Although it shows itself to us of such a hot and dry nature, we must not think that sulphur is a substance so pure that it can stand by itself or that in order to attain its form it has no need of its portion and part of moisture like every other mixture. This is shown to us by its easy fusion, in which it resembles the metals. This thing is found in many places and in many varieties of color; some are white, others yellow and orange, and some others between gray and black. They also say that some red is found. It does not occur in that arrangement of veins like other minerals, but most liberal Nature makes whole mountains of it as is seen in the Aeolian islands, [26] near Sicily, in Etna or Moncibello which is the island of Sicily, at Pozzuoli, in the territory of Rome, in the Sienese domain at San Filippo, and in many other similar places. It is a substance that has a very strong odor and is most unpleasant to smell. It is very fixed in its substance so that it is never corrupted by time, by boiling, or by the moisture of water. For although it may stand in water a long time it never becomes soft nor does it ever decrease or increase in weight. It is brittle and easily crushed very fine. It is said that a trace of garlic rubbed on the mortar helps anyone who wishes to reduce it to impalpability. Its ores have a form more like earth than like stone although they some¬times have the color of a certain soft rock. The places where it is found are easily recognized by the great odor that they give out and by the very hot baths that often spring forth near it. What I have already told you about quicksilver that is contrary to the

Jan 1, 1942

By Coopers &. Lybrand

INTRODUCTION From a tax viewpoint, United States mining companies are at a substantial disadvantage in the international mining area compared with companies in other major capital-exporting countries, according to a 1975 study by Coopers & Lybrand for the American Mining Congress. The study compared the relative tax position of a United States investor with investors from Belgium, Canada, France, Germany, Japan, the Netherlands, Switzerland, and the United Kingdom. The comparison was based on average rates of return realizable by investor companies on four mine-model investments in twelve capital-importing countries. The countries in which these investments were assumed to be made are varied in their tax systems so that a wide range of possibilities was included in the analyses. Each mine model was standard so that the rates of return for each investment by each investor were affected solely by the respective tax systems of the capital-exporting and capital-importing countries. UNITED STATES POSITION The study found that the United States competitive position, in terms of the average rate of return on an overall basis, ranked next to last among the nine capital-exporting countries in the study. Further, the United States overall rate of return is more than 20% below that of the country (Japan) with the highest overall rate of return. On an average return-on-equity basis, the United States' position among the nine investor countries, for each of the mine investments studied, was: copper, eighth; iron ore, sixth; nickel, fifth; manganese, a tie for last place. Figure 1 shows the overall results realized by each capital-exporting country on the basis of average return on equity. [ ] The frequency with which a given capital-exporting country attains the highest or next highest rate of return in a capital-importing country provides further insight and another basis for comparing the tax laws of the capital-exporting countries. Of the situations compared in the study, the United States never attained the highest rate of return, and reached the second and third highest rate of return in only two instances. The tables showing the frequencies of rankings are given in Table 1 for each of the four mine models. In summary, the United States mining company does not have a competitive advantage under the tax rules when competing for mineral concessions in other countries. The United States company, in fact, appears to be at a clear disadvantage. The study also considered the effect of the following recent tax proposals on United States investors in international mining ventures:

Jan 1, 1985