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By Robert G. Van Nostrand, John H. Henkel

TRANSIENT potentials obtained in resistivity prospecting can be separated into two classes. The first is electromagnetic, has a comparatively short time constant, and increases in relative amplitude as the electrode separation is increased. These electromagnetic transient potentials, of which an excellent theoretical treatment is given by Yost,1 are the result of changes in the current and can be classed as differentiated signals. The second class is electrochemical, has a comparatively long time constant, and decreases in relative amplitude as the electrode separation is increased. The electrochemical signals are generated by the current flow itself and can be classed as integrated signals. The transient potentials due to electrochemical factors are the subject of this article. The phenomenon is referred to as induced polarization. Schlumberger2 was the first worker to observe induced polarization, but he was unsuccessful in attempts to apply the principles of induced polarization in electrochemical prospecting. Other workers, notably Bleil3 have studied polarization and in some cases pointed out its possibilities, but no theory has been presented that describes polarization and its time dependence adequately. It is the purpose of this discussion to present the essence of a theory to geo- physicists and to show that it leads to results consistent with experimental evidence. The theory on which this analysis is based has existed in electro- chemical circles since 1910.4

Jan 3, 1957

By Gerhard Derge

A SERIES of studies of the corrosion of tin is under way in the Metals Research Laboratory at the Carnegie Institute of Technology. The complete program includes examination of the corrosion properties of high-purity tin and the changes produced in these properties by the addition of varying amounts of alloying elements. Other studies of this subject have been made recently under the sponsorship of the Inter-national Tin Research and Development Council, but these researches have been confined largely to the weakly acid environments commonly encountered in the canning industry.1 There is little information avail-able regarding the corrosion of tin under alkaline conditions, but such data would be of value, for a large amount of the metal is used under such conditions. The potential measurements to be described were made because they seemed to offer the most rapid method for obtaining a general view of the conditions to be encountered in such service. These experiments will also serve to establish a technique that will be of value in further studies. It must be emphasized that the results reported are those of controlled laboratory experiments and that the conclusions drawn cannot yet be applied to service conditions; rather, they point to the directions in which, more exhaustive experimental work may be clone to best advantage.

Jan 1, 1938

THE compiler, or author, of the Probierbücblein is not known, and the date of its first printing is uncertain. It was obviously not written by an assayer who wished to give a coherent description of his craft for the instruction of others; this was left for Biringuccio first to do. It is easy to believe that originally the Probierbücblein was a random collection from various sources of information useful to an assayer, probably gathered by one of the profession for his own use. It must remain a matter of speculation whether this was shown to a printer, who recognized the opportunity to turn an honest penny and made an inept attempt to give the manuscript the appearance of a coherent account by writing a preface and arranging the various items in somewhat logical sequence, or whether the assayer him- self started this job and was prevented from finishing it. That some sections of the book, especially near the be ginning, present an almost continuous story, while others are chaotic in their arrangement; that several paragraphs are printed more than once in different places; that there are paragraph headings, for which the text was never written, or lost, followed by irrelevant information-all this seems evidence of a job unfinished and points to a publisher's offering for the public's quick money. The demand must have been brisk, for metal working was a profitable profession, and the jeweler who was working with metals but did not care to become completely trained in assay methods would jump at the chance of acquiring easy knowledge. Even the great Agricola has whole sections obviously plagiarized from the Probierbücblein. Neither Biringuccio nor Ercker shows any direct influence, though they and all subsequent metallurgists will in some degree be affected by

Jan 1, 1949

By Allan J. Clark, W. J. Sharwood

When the cyanide process came into general use, late in the nineteenth century, chlorination was quickly supplanted, but amalgamation yielded place more slowly, being still the major process at many plants, where it is followed by cyanidation of the tailings. The research work of the Denny brothers in South Africa' was probably the most important contribution of its time to the metallurgy of gold. By grading analyses of mill products, they pointed to the necessity of fine grinding to accomplish maximum extraction by cyanide. The work here described is merely an extension of the Dennys' method. Developing the fine-grinding principle, the steps of "crushing in solution" and of "all-sliming" were logical sequels, though both had been attempted early in the history of the cyanide process. Crushing in solution introduced certain complications in amalgamation; when "all-sliming " was adopted it was observed that the omission of amalgamation did not materially affect the total recovery. Thus the field of the older process has become much restricted, being at present confined to ores which, yielding freely to amalgamation, either are too low in grade to show an economic advantage in "all-sliming," or present chemical or other difficulties making the use of cyanide solution unadvisable during the crushing and preparation of the ore. South African ores are typical of the former class; Homestake ores are of both classes, but even in these instances the amalgamation work is being curtailed and greater burdens thrown on the cyanide plants. It is obvious that the time required for the dissolution of gold depends on the size of its particles. In an effort to determine the critical size, the following laboratory method was evolved. A standard amalgamation test2 had already been established, which involves the agitation of about 100 gm. of ore with 20 gm. of pure mercury, the latter then being separated and its gold contents determined. This method was applied directly to certain mill products with interesting results, a few of which may be noted here. The column "Free Gold" gives the value per ton thus amalgamated, as against the " Total Gold " determined by fire assay.

Jan 1, 1923

Iron Ores and Blast Furnace Practice Concentration of Iron Ores in the United States. By T. R. Counselman. (Metals Technolog), December 1943) Selection of Blast-furnace Refractories. By Hobart M. KrANer and E. B. Snyder. (Metals Technology, April 1944) The Washing of Pittsburgh Coking Coals and Results Obtained on Blast Furnaces. By C. 1). King. (Metals Technology, September 1943) Steelmaking The Role of Basic Slags in the Elimination of Phosphorus from Steel. By Richard L. BArrett and William J. McCaughey. (Metals Technology, April 1944) The Relative Deoxidizing Power of Boron In Liquid Steel and the Elimination of Boron in the Open-hearth Process. By B. W. Gurry. (Metals 'Technology, December 1943) Manufacture and Properties of Killed Bessemer Steel. By C. C. Wright. (Metals Technology, June 1944) Hardenability Effect of Sixteen Alloying Elements on Hardenability of Steel. By Irvin R. Kramer, Robert Hafner and Stewart L. Toleman. (Metals Technology, September 1943) Effect of Quenching Temperature on the Results of the End-quench Hardenability Test. By Clarence E. Jackson and Arthur L. Chrjstenson. (Metals Technology, December 1943) Effect of Some Elements on Hardenability. By Walter Crafts and John L. Lamont. (Metals Technology, January 1944) Effect of Several Variables on the Hardenability of High-carbon Steels. By I?. S. Rowland, J. Welchner and R. IS. Marshall. (Metals Technology, January 1944) Mechanical Properties Influence of Hydrogen on Mechanical Properties of Some Low-carbon Manganese-iron Alloys and on Hadfield Manganese Steel. By Herbert H. Uhlig. (Metals Technology, June 1944) Aging and the Yield Point in Steel. By J. R. LOW, Jr., and 14. Gensamer. (Metals Technology, December 1943) Tensile Properties of Medium-carbon Low-alloy Cast Steels. By H. A. Schwartz and W. Kenneth Bock. (Metals Technology, August 1944) Variables Affecting the Results of Notched-bar 1mpct Tests on Steels. By CLarence 15. Jackson, MYRon A. Pugancz and Frank S. McKenna. (Metals Technology, August 1944) The Notched-bar Lmpact Test. By John H. Hollomon. (Meta1s Technology, April 1944) Hardness Measurement as a Rapid Means for Determining Carbon Content of Carhon and Low- alloy Steels. By K. L. Clark and NIcHols Kowall. (Metals Technology, January 1944)

Jan 1, 1944

By Colman Goldberg

IT is customary to plot crystallographic planes or axes on a Wulff stereographic net which is ruled with parallels of latitude and meridians of longitude. If a single crystal is placed at the center of a sphere, the coordinates of a crystallographic plane or axis are the coordinates of the point where the axis intersects the sphere. The standard (HKL) projection is the projection for which the sphere is rotated so that the (HKL) pole is at the center of the projection. Schiebold and Sachs' and many others have published standard projections for the more important planes of a cubic crystal. With Tables I and 11, it is possible to plot any plane (HKL) of a cubic crystal on a standard (001) projection if the absolute values of the individual H, K, and L are nine or less, which is almost always the case. Using the methods outlined by Barrett,' the standard (001) projection can be rotated so that any arbitrary plane is at the center of the projection. The tables are believed to be important for two reasons: 1—The heretofore published standard projections usually are not of the proper size to fit the stereographic nets available. With these tables a standard projection can be made which will be of exactly the proper size for the available stereographic net. 2—With the tables, planes that do not appear on the previously published standard projections can be easily plotted. For these reasons, the tables are especially useful in the study of optical reflections from etched surfaces and can also be used to make a standard projection for the axis which is normal to the macroscopic surface. (This axis can be found by X-ray or optical methods.) Then if the crystal is etched, the effect of the etchant can readily be determined by comparing the latitude and longitude of the reflecting planes (as determined with an optical goniometer) with the standard projection that has been prepared. Use of the Tables Fig. 1 shows the meridians and parallel which have been designated as zero longitude and latitude. The tables themselves are self-explanatory. The

Jan 1, 1953

By Bruce A. Kennedy

In recent months, public hearings held by the Senate Subcommittee on Minerals, Materials and Fuels on the Stillwater copper-nickel complex in Montana have been reviewed at great length in the press. Although the meetings were well managed by the Subcommittee and questioning was kept in line with the aim of the hearings-namely, how can re- sources be developed in a manner compatible with the preservation of the environment-it was alarming to read the apparently uninformed and questionable arguments presented by some witnesses who were attempting to prohibit mining in the area altogether. One spokesman even went so far as to urge that mining of the area be rejected be- cause, even if the mining operation did not pollute the areas, the effluent and waste produced by the people themselves could constitute a hazard to the environment and to themselves. This, of course, would be true to a point. However, if this or similar types of reasoning were used to reject mining of a large number of orebodies in the future, how is the United States going to meet its future mineral demands and what effect could this have on the economic strength of the country? Fall of the Roman Empire An interesting article in a recent issue of Time magazine came up with a new theory to explain the fall of the Roman Empire. Claire Patterson of CalTec, during a recent study of air pollution, investigated the historical worldwide distribution of lead. As lead was a by-product obtained from silver mining during historical times, he turned his attention to studying the production of silver during those eras. He discovered a very interesting fact-that, I unless the stock of metal is continually being replenished from the mines, accidental loss diminishes a country's stockpile of silver at a rapid rate, as much as 2 per cent per year. Patterson, a geochemist, theorized that with an accidental loss rate of 2 per cent per year, if the country's silver supply dried up, the entire existing stockpile could disappear in about a century.

Jan 1, 1971

Iron Ores and Blast Furnace Practice Concentration of Iron Ores in the United States. By T. R. Counselman. (Metals Technolog), December 1943) Selection of Blast-furnace Refractories. By Hobart M. KrANer and E. B. Snyder. (Metals Technology, April 1944) The Washing of Pittsburgh Coking Coals and Results Obtained on Blast Furnaces. By C. 1). King. (Metals Technology, September 1943) Steelmaking The Role of Basic Slags in the Elimination of Phosphorus from Steel. By Richard L. BArrett and William J. McCaughey. (Metals Technology, April 1944) The Relative Deoxidizing Power of Boron In Liquid Steel and the Elimination of Boron in the Open-hearth Process. By B. W. Gurry. (Metals 'Technology, December 1943) Manufacture and Properties of Killed Bessemer Steel. By C. C. Wright. (Metals Technology, June 1944) Hardenability Effect of Sixteen Alloying Elements on Hardenability of Steel. By Irvin R. Kramer, Robert Hafner and Stewart L. Toleman. (Metals Technology, September 1943) Effect of Quenching Temperature on the Results of the End-quench Hardenability Test. By Clarence E. Jackson and Arthur L. Chrjstenson. (Metals Technology, December 1943) Effect of Some Elements on Hardenability. By Walter Crafts and John L. Lamont. (Metals Technology, January 1944) Effect of Several Variables on the Hardenability of High-carbon Steels. By I?. S. Rowland, J. Welchner and R. IS. Marshall. (Metals Technology, January 1944) Mechanical Properties Influence of Hydrogen on Mechanical Properties of Some Low-carbon Manganese-iron Alloys and on Hadfield Manganese Steel. By Herbert H. Uhlig. (Metals Technology, June 1944) Aging and the Yield Point in Steel. By J. R. LOW, Jr., and 14. Gensamer. (Metals Technology, December 1943) Tensile Properties of Medium-carbon Low-alloy Cast Steels. By H. A. Schwartz and W. Kenneth Bock. (Metals Technology, August 1944) Variables Affecting the Results of Notched-bar 1mpct Tests on Steels. By CLarence 15. Jackson, MYRon A. Pugancz and Frank S. McKenna. (Metals Technology, August 1944) The Notched-bar Lmpact Test. By John H. Hollomon. (Meta1s Technology, April 1944) Hardness Measurement as a Rapid Means for Determining Carbon Content of Carhon and Low- alloy Steels. By K. L. Clark and NIcHols Kowall. (Metals Technology, January 1944)

Jan 1, 1944

No records have been found of coal in the old Spanish documents, although some mention of it probably exists in manuscripts. Coal was found in Mt. Diablo, in Contra Costa County, about five miles south of the San Joaquin River in 1852, but the first mine, the Teutonia, was located in 1858. The deposits are located on both sides of a high ridge, and vessels of 1,000 tons burden could ascend the river to the nearest point to the mines.1 In 1854, coal was found about four miles from Oroville, on the Feather River, in Butte County. Development work was started and in 1856 a mine was opened. From the description the coal was likely a variety of lignite and probably never amounted to anything commercially, as it does not appear again in the records 2 The more valuable mines at Mt. Diablo were opened in 1859 and 1860. By 1867 there had been 11 mines started and at that time five were in operation. The seam conditions were much disturbed and lack of knowledge of them caused much waste of effort and money. All of the coal excepting that used locally and in nearby towns, was shipped to San Francisco, and largely used for steam purposes. The first receipts were in 1861-6,620 tons. A railroad to the river had been constructed and opened in February 1866. The Corral Hollow field in Alameda County was found and prospected to a small extent in 1862. Two mines were opened but little work was done and the field was then abandoned. Good exposures were rare and the cost of underground exploration was then prohibitive. The Commercial mine produced coal in 1869 and 1870, but a fire in the latter year destroyed the tipple and communications to the mine. The Livermore mine was abandoned after 18 months operation in 1875 and 1876 and no other work was done here until the nineties. In 1867 Hyne reported the presence of coal in workable thickness, and of good quality, on the property of the Pacific Coast Petroleum Company,

Jan 1, 1942

By Allan J. Clark, W. J. Sharwood

When the cyanide process came into general use, late in the nineteenth century, chlorination was quickly supplanted, but amalgamation yielded place more slowly, being still the major process at many plants, where it is followed by cyanidation of the tailings. The research work of the Denny brothers in South Africa' was probably the most important contribution of its time to the metallurgy of gold. By grading analyses of mill products, they pointed to the necessity of fine grinding to accomplish maximum extraction by cyanide. The work here described is merely an extension of the Dennys' method. Developing the fine-grinding principle, the steps of "crushing in solution" and of "all-sliming" were logical sequels, though both had been attempted early in the history of the cyanide process. Crushing in solution introduced certain complications in amalgamation; when "all-sliming " was adopted it was observed that the omission of amalgamation did not materially affect the total recovery. Thus the field of the older process has become much restricted, being at present confined to ores which, yielding freely to amalgamation, either are too low in grade to show an economic advantage in "all-sliming," or present chemical or other difficulties making the use of cyanide solution unadvisable during the crushing and preparation of the ore. South African ores are typical of the former class; Homestake ores are of both classes, but even in these instances the amalgamation work is being curtailed and greater burdens thrown on the cyanide plants. It is obvious that the time required for the dissolution of gold depends on the size of its particles. In an effort to determine the critical size, the following laboratory method was evolved. A standard amalgamation test2 had already been established, which involves the agitation of about 100 gm. of ore with 20 gm. of pure mercury, the latter then being separated and its gold contents determined. This method was applied directly to certain mill products with interesting results, a few of which may be noted here. The column "Free Gold" gives the value per ton thus amalgamated, as against the " Total Gold " determined by fire assay.

Jan 1, 1923

By V 7. 0 / 300 dpi

THE cams at present universally used in stamp mills lift the tappets with an involute form of curve, to which the surface of the tappet is always tangent; moreover, the line of contact between tappet and cam, if produced, would pass through the center of the stem. This is no doubt a desirable feature, but the writer has long believed that it would be much more desirable if the cam were to pick up the stamp without shock, and gradually increase the upward velocity of the stamp throughout its upward movement. The involute form of cam attempts to impart instantly a considerable upward velocity to the stamp, starting it from a state of rest, and the result is a destructive blow, a great deal of noise, and much wear and vibration. The writer has developed a form of cam which will lift the stamp with a motion similar to that of the piston of an engine between the end and middle of its stroke; in other words, harmonic motion, from the point. of zero to maximum velocity. The curve will give this ideal motion only when the stamp is set for the exact drop for which the cam was designed, but the improved cam will not be as bad as the involute cam until the drop is reduced one-half. In other words, if a cam is designed for a 6-in. drop, it will be some improvement over the usual form of cam until the drop is only 3 in. Any cam, whatever its form, must of course lift the stamp in the same number of degrees of revolution; therefore, with this new form, since the stamp starts more slowly on its upward course, it must end up by going faster, the average speed being the same as with the involute cam. The stamp, after it is no longer in contact with the cam, keeps on going up a certain distance, which is easily calculated. It is therefore possible to hang up a stamp without a cam stick, if the fingers are not more than 1/8 in. longer than necessary to hold the tappet above the cam.

Jan 12, 1914

By R. C. Canby

The difficulty of exact neutralization by ammonia of the acid solution obtained in the determination of arsenic by the method of fusion with carbonate of soda and nitrate of potassium, led me to try the effect of neutralization by oxide of zinc. I obtained most satisfactory results, and found a great saving of time. The oxide of zinc being added in excess, there is no delicate testing with lit? mils paper and tedious alternate adding of dilute ammonia arid acid until the proper point is reached. The excess of oxide of zinc, too, seems to hold, from the filter, the gelatinous silica and alumina, which are usually precipitated upon neutralization, and thus to render the washing of the precipitated arseniate of silver almost invariably much more rapid. Except the substitution of the neutralization by oxide of zinc for the more tedious method by ammonia, the details of the process are practically the same as those published by Mr. Richard Pearce, of Argo, Colorado (Proceedings of the Colorado Scientific Society, vol. i.), who shows what very accurate results can be obtained by the fusion process. I have made numerous tests of comparison between the two methods of neutralization, and find that those by the oxide of zinc agree almost exactly with the old method. Increasing the quantity of nitric acid, even to considerable excess, to be neutralized by the oxide of zinc did not affect the precipitation of arseniate of silver. The process may be outlined as follows : Take 4 to 1 gramme finely pulverized ore, and mix in a porcelain crucible with eight to ten times its weight of a mixture of equal parts of carbonate of soda and nitrate of potassium (Kerl. Metallurgische Probirkunst gives 4 to 5 nitre to 14 soda). Gradually bring to fusion and keep so, three to five minutes. Cool. Disintegrate in hot water. Filter and wash with hot water. Acidify the filtrate with nitric acid, and boil to expel carbonic acid and nitrous fumes. Cool. Add an excess of an emulsion of oxide of zinc. The bottom of the beaker should have quite a layer of oxide of zinc, after stirring.

Jan 1, 1889

A. M. CANDY,* Pittsburgh, Pa.-I think more stress should be laid upon the question of welding with the carbon electrode, which we ordinarily call graphite arc welding. Mr. Miller's photograph indicated that the original parent metal had been decarburized to a marked degree. It would be interesting to know the carbon content of the parent metal, and whether or not Mr. Miller has made any investigations to determine if the metal is always decarburized or whether in some instances we actually have carbon injected into the weld, which has been the understanding that has been quite prevalent. There were one or two other points that Mr. Miller brought out concerning which I desire to ask one or two questions: The illustrations that he presented were obtained with what, I suppose, would be termed a real low-carbon steel welding wire, which gives in the deposited metal grains that are more or less symmetrical, whereas the Roebling electrode, which is a mild steel of higher carbon content, apparently gives a columnar structure. I do not know which-of these I structures is more desirable, but assuming that the structure produced by the really low-carbon steel wire is the more desirable, would it not be true that the very low carbon content would, probably owing to high temperatures that prevail in the arc, result in a greater amount of oxidation and probably result in either carrying into the weld more oxide or producing more oxide on the surface as the operator progresses? The short arc is an advantage in all cases. Whether Mr. Miller's trouble is oxide or nitride, the short arc helps him out, because the closer the end of the electrode is to the work the less chance there is for either oxygen or nitrogen to get in. And whichever is the cause of the trouble, the short arc keeps it out by lessening the time in which the steel is molten and the amount of air that gets in. It also makes sure that the molten metal will not fall into the crater. Everything is in favor of the short arc.

Jan 4, 1919

By Walter M. Stephen

MODERN developments in alloy steels have been so rapid and diverse that engineering practice has scarcely had time to re-appraise all items of past experience wherein conclusions became axiomatic under conditions that no longer apply. A case in point is the wet screening of abrasive ores within the fine range still looked upon as belonging exclusively to classifiers. By virtue of the development of stainless steels (18 per cent Cr, 8 per cent Ni), it is no longer true that classifiers are more economical than screens in closed circuit with large-tonnage ball or rod mills at 65 or even 100 mesh, provided a selective overgrind of the higher-gravity constituents of the ore is not desired. Wet screening of ores is a highly corrosive as well as an abrasive operation, because of the inevitably high degree of oxygenation of the water. Screen cloth of ordinary or spring-steel wire almost at once becomes pitted arid covered with a film of corrosion products, which causes rust-blinding of fine-mesh screens and offers high frictional impedance to the flow of ore particles. On the other hand, the well-known properties of stainless steel enable it to maintain a bright surface, and so to eliminate blinding either by ore particles or by corrosion products. That a large-tonnage mill grinding hard ore to 65 mesh can be operated economically in closed circuit with screens instead of classifiers has recently been demonstrated at the Copper Cliff concentrator of the International Nickel Co.; in the test to be described, a 6 ½ by 12 ½ -ft. Marcy rod mill ground from 625 to 820 tons of ore per day to approximately 65 mesh, operating in closed circuit with three 4 by 5-ft. Hum-mer screens, without any classifier. Stainless-steel cloth gave an indicated life of several months. There was no difficulty with blinding, yet dilution and spray water could be controlled so that screen undersize averaged not less than 40 per cent solids. In contrast, ordinary carbon steel was pitted and blind with rust within 40 hours.

Jan 1, 1938

By C. D. Starr

IT is well known that the martensite reaction can be induced to occur isothermally above the M, temperature by plastic deformation of an alloy in its austenitic state, and also that as the test temperature is increased above the M. temperature, plastic deformation under a given set of conditions merely causes additional slip with a corresponding tendency toward the formation of less martensite per unit of strain. Thus it appears that a maximum temperature exists above which martensite cannot be formed isothermally by plastic deformation. This temperature is commonly designated as the equilibrium temperature Te. Attempts to determine experimentally the equilibrium temperature have indicated that a critical temperature is observed, under a given set of conditions, above which martensite cannot be formed isothermally by plastic deformation. But the observation of a "so called" critical temperature, Te, should not be confused with the equilibrium temperature, Te. In order to clarify this anomaly, true stress-strain curves were obtained for a series of type 304 stainless steel specimens (manufacturer's analysis, 0.08 pct C, 18 to 20 pct Cr, 8 to 10 pct Ni, balance Fe) over the temperature range 67" to 300°K.' Since martensite is magnetic, a quantitative measure of the amount of martensite that was produced by plastic deformation was obtained by determining the magnetic permeability as a function of strain. The results of these tests are given in Fig. 1. They appear to indicate that a plastic critical point does exist at about 240°K for the stainless steel under investigation here. But that 240 °K is not the equilibrium temperature nor even a true plastic critical temperature can be seen from Fig. 2 wherein the permeability of the same material is shown to increase with cold rolling at 293 OK. Consequently the observation of a "so called" plastic critical temperature is dependent on the mode of deformation and has no theoretical significance. Acknowledgment This work was sponsored by the Office of Naval Research. Permission to publish this note is gratefully acknowledged.

Jan 1, 1954

KARL A. PAULY,* Schenectady, N. Y.-We are deeply indebted to Mr. Hobart for a record of the actual experience of the Lehigh Coal and Navigation Co. with electrification. One of the essential features of this test is that it was made under actual operating conditions. In one of the western mining districts I was once discussing the electrification of a large hoist with a mining operator, who told me that they had made a very thorough test and that the results were such as to indicate that electrification was not warranted. When questioned regarding the test, he said that they had called on the mining college in the Territory for assistance, and one of the instructors and a group of students had made the test. They first cleaned the boilers and then operated them at a' continuous load, using the maker's guaranteed steam consumption per indicated horsepower as a guide in estimating the steam consumption under actual hoisting conditions. Such a test is absolutely valueless. The efficiency of the boilers 'is affected by the intermittent demands on the steam. The standby losses, as indicated by Mr. Hobart's paper, are quite equal to the actual fuel consumption required to do the work; very frequently, also, the cost of repairs is either omitted or underestimated. One noticeable feature of Mr. Hobart's tabulation is that there is no mention of steam consumption. Intentionally or otherwise, the steam-hoist builders have befogged the question by making a great point of the steam consumption of hoists. The operator is not at all concerned in steam consumption; it is the actual cost of operation that he is interested in, and it is a comparison between the cost of operation of the two systems, all factors being considered, that should determine the choice. The steam consumption, or its determination by test, is only one step in the problem of estimating the fuel consumption, which, in an actual installation, can be directly measured much more accurately, as was done by Mr. Hobart.

Jan 4, 1918

By Robert Linton

IN 1898, Joseph L. Giroux and J. A. Snedaker organized the Pilot Knob Copper Co. and began developing the Pilot Knob mine at Kimberly, Nev., for high-grade copper ores, carrying good gold and silver values that the formation had disclosed. At that time the nearest railroad was over 150 mi. distant. The high-grade ores did not prove to be extensive at this point-at least to the depth. (240 ft.) to which the work was carried-but development of neighboring claims indicated extensive deposits of sulfide porphyry ore of concentrating grade lying at shallow depth, and deeper deposits of direct-smelting oxidized ores occurring in limestone near the limestone-porphyry contact. The properties passed through the hands of several organizations, with only meager development, until acquired in 1913 by Consolidated Coppermines Co., whose holdings now comprise 3480 acres of mining claims in the Robinson district. Since that time development has been prosecuted more actively; and for the purpose of determining the most efficient and economical method of treating the ores, considerable testing work has been done during the past three years, both in the laboratory and in actual mill operations. At first, the shipments were of ore high enough in grade to be profitable even with the long wagon hauls to the railroad and prevailing freight and smelting charges. In 1905, a blast furnace and a concentrator were erected at Kimberly. On account of insufficient ore supply, the blast furnace was never blown in and later was dismantled. The concentrator as originally equipped wag operated for only about two months, both because the ore supply was not sufficient and because gravity concentration did not yield satisfactory extraction. The location and arrangement of the mill further entailed high operating costs. In 1908, the Nevada Consolidated Copper Co. began to mill successfully, on a large scale, its sulfide porphyry ores, which are similar in character to the adjacent Coppermines ores. After that time, all of the ores and concentrates produced by Coppermines Company were

Jan 8, 1920

By J. H. Frye, D. L. McElroy, E. E. Stansbury

The rates of growth of pearlite in high-purity Fe-C alloys have been measured as a function of the transformation temperature. These and other data have been correlated in terms of a derived rate equation. Activation energies for the growth were found to be 24,200 cal per mol of austenite for the 0.78 pct C alloy and 27,600 cal per mol for the 0.93 pct C alloy. Theoretical implications are discussed. AN excellent review of the the theoretical and experimental studies on the mechanism and kinetics of the eutectoid reaction has been presented recently by Mehl and Dube.' They have pointed out that these investigations have followed two lines of approach: 1—experimental studies and derivations of expressions for the overall transformation characteristics, and 2—derivation of expressions for the nucleation and growth rates in terms of fundamental processes. Investigations of the latter type have been concerned for the most part with the nature of the growth at the austenite-pearlite interface in plain carbon and alloy eutectoid steels. They discuss two theories of the rate of growth of pearlite from aus-tenite—those of Brandt and of Zener. Both derive rate equations which are based on the assumption that carbon diffusion is the controlling mechanism. Mehl and Dube,' Zener,2 and Brandts. " have attempted to calculate growth rates by use of these equations together with thermodynamic and diffusion data. The results are encouraging, but agreement is not so good as to constitute verification of the theories. Furthermore, it Is not clear how these equations are to be used to study the effect of alloying elements which apparently exert little influence on carbon diffusion, but markedly decrease growth rates. It is not clear whether or not the addition to iron of an alloying element which does not diffuse during transformation can alter the rate of growth of body-centered from face-centered cubic iron. That it can greatly decrease the overall transformation rate has

Jan 1, 1954

By G. S. Brooks, L. G. Duncan

During the past few years, the Mineral Point Zinc Co. has had under consideration the improvement of various types of gas-filtering apparatus used in the removal of dust from crushing and milling plants, in the manufacture of oxide, and on blast-furnace fume and sintering furnaces. The original equipment of the various plants of the company was, of course, along lines of the standard stationary bag house. These houses required large surfaces, hand shaking, and varied only in the manner of the collection of solids and in the distribution of the gas. , Early in 1908, the first trial of a mechanical bag house was made at Nassau Plant at Depue, Ill. The duty of this installation was on dust-laden gas from a fine-crushing mill. The Printz and Rau bag machine was finally adopted and put into operation. This ingenious machine embodied what were then to us two novel features in bag-house practice: 1. An intermittent crinkling and snapping of the filtering fabric to free the meshes of solids. 2. A reversal of gas flow for a short period by a temporary connection with the suction trunk. This equipment worked fairly well except in cold weather, when we ran into condensation troubles. Had we at that time understood more fully some of the limitations of fabric filtering work, these might well have been remedied. We were impressed by this experience, however, with the efficiency of sudden tension on the fabric under suction. After a study had been made of some of the western blast-furnace houses using the reversal-of-flow feature, experiments were started early in 3 914 with a view to developing an automatic equipment along the best lines of our past experience. The objects sought were: 1. Keeping labor out of the houses for hygienic reasons. 2. Reduction of labor costs. 3. Reduction in size of bag houses. 4. Accessibility. 5. Ability to handle relatively hot gases where required.

Jan 1, 1918

By John V. Beall

Homeland of the Republic of China, the island of Taiwan looks on the map like a seal, muzzle pointed south, resting complacently on the emerald waters of the China Sea. Any notion of placidness is quickly dispelled by going to that country where the visitor gains the impression of almost violent busyness in tearing up streets, pushing up buildings and tilling the fields. Driving from the airport downtown to Taipei, the capital city, one sees roads, streets and thorough-fares which seethe with bizarre traffic. From water buffaloes to buses, transportation takes every conceivable shape, size and color in between. The load being transported need not conform in any way to the capabilities of the vehicle. Twenty- foot lengths of pipe may be trans- ported on a bicycle. A family of five may go to town on a motor- cycle. Impossible? Count them. The streets and buildings of the city appear unrestrained, or without margins. Shops do not end at the doorway but overflow with a variety of goods onto the sidewalks and into the streets where the marginal traffic, on foot or on wheels, intertwines unconcernedly with the flotsam from the shops. Signs, dry goods, hardware and the continuous hubbub make the view colorful, lighthearted and fascinating. The island is 230 miles long by 75 miles wide with a central mountain spine. To the east, the mountains descend steeply to the ocean whereas to the west, beyond the foothills, there is a broad coastal plain. Only about 25% of the land is suitable for cultivation but the tropical climate permits several harvests a year. At the same time the mountains, which are high enough to sometimes have snow, offer an agreeable change of temperature. In this setting, society has created an economy that is growing at such a rate on all fronts that it would seem to be fairly bursting at the seams.

Jan 9, 1969