Search Documents

The world's largest steam-driven mine hoist, built by Nordberg Manufacturing Co. a half century ago, has become a major tourist attraction in Michigan's Upper Peninsula. The hoist, designed by company founder Bruno V. Nordberg, is located in the Quincy Mine Number Two, just north of Hancock. Nordberg began construction of the mammoth machine before World War I, but delayed completion until after the war. The hoist became operational in 1920 and continued running until the mine was shut down in 1931.

Jan 9, 1968

By George S. Rice

GROUND movement from mining, whether it be for coal, metal, industrial minerals, or .oil, will always present many difficult problems. These are especially serious when valuable surface improvements may be badly damaged. The mine itself, if mining methods are not suitable to the formation, is subject to heavy falls of the main roof in the working places; and with certain structural conditions the movements may cause in coal mines disastrous bumps and outbursts of gas, and in deep metal mines rock bursts. In open-cut work rock and earth slides may result. Absolute prevention of ground movement from mining is impossible unless large pillars are left unmined,

Jan 1, 1937

By AIME AIME

IN an address before the New York Section. A.I.M.E., Oct. 20, Alex L. ter Braake, speaking on the tin industry of the Netherlands East Indies, interjected a few remarks, at the chairman's request. on the mineral stock-piling project now before Congress in a bill sponsored by Senator Scrugham. The full text of Mr. ter Braake's paper was published in the Nov. 6 issue of the American Metal Market. Following mention of the buffer stock scheme as applied in the tin industry, Mr. ter Braake continued:

Jan 1, 1943

Herewith are transmitted the joint report of the Treasurer and Finance Committee for 1934 and the reports for the same year of the Chairmen of the following Committees: Admissions, Membership, Papers and Publications, Library, and MINING AND METALLURGY. TO these reports you are referred for details of the year's activities. Finances.-Income for 1934 from all sources totalled $134,967 com- pared with $121,689 in 1933. The increase is accounted for principally by four items: $6000 increase in initiation fees and dues of new members; $1800 in current dues; $4000 in "back" dues; and $2800 in the sale of publications, including TRANSACTIONS volumes and technical papers in the form of "separates." In passing, it may be remarked that income from back dues during 1935 will be less than in 1934, for the obvious reason that the total amount of dues in arrears has shrunk and consequently there is less to draw from. Income from

Jan 1, 1934

By E. C. IBBOTSON

THIS process was reported upon by the Canadian Commission in 1904, and much detailed information was also given in a paper by Chief Engineer V. Engelhardt.1 Believing that some of the latest particulars of the process will be of interest, I submit the following data. At Gysinge in Sweden during the year ending May 31, 1906, from a fixed furnace giving 1 ton (2,240 lb.) of steel per tap, there were produced 950 tons of tool-steel and special steel ingots. . In carbon and iron tool-steels all the usual tempers were made. The bulk of this steel was made from charges composed of about 80 per cent of Swedish white pig-iron and 20 per cent. of steel-scrap. The percentage of carbon was regulated by the addition of briquettes. Other charges were made from Swedish white iron and steel-scrap. The average time taken per charge, for the year, when adding briquettes, was 7* hr., and the electric energy consumed was 1,128 units (kilowatt-hours) per ton. The average time per charge for white-iron and scrap charges was 5.5 hr., and the electric energy consumed was 886 units per ton. These consumptions include all time and energy lost from various causes, such as bad water-supply, ice, etc. It is quite ordinary practice to complete the charges with briquettes in 6.5 hr., and without briquettes in 5 hr., as shown by the following typical charges White pig-iron, 1,457; steel-scrap, 439; briquettes, 220; ferrosilicon (50 per cent. of silicon), 17 ; ferromanganese (80 per cent. of manganese), 15 lb. ; and aluminum, 1 oz.=

Nov 1, 1906

By Kenneth R. Hancock

Iron oxides are unique in that they are the only significant colored mineral found in a natural state suitable for use as a pigment after it has been pulverized to pigmentary size. The current world production of iron oxide pig¬ments is estimated by the author to be between 450,000 and 550,000 tons based on 1969 data. The fact that highly colored natural deposits of iron ore are found throughout the world ac¬counts for its use in prehistoric man's artistic cave paintings. These early artists did not realize that they had established man's first paint test fence which now has some 20,000 years of exposure. In addition to abundance, constituting about 7 % of the earth's crust, iron oxides have the advantages of low cost, permanency, and are not toxic. Through the centuries, succeeding civilizations have utilized iron oxides as a major source for decoration and protection when coloring was desired. In the last century the chemical industry has improved on nature by developing a complete range of synthetic iron oxide pigments which surpass the pigments pro¬duced from natural iron ores in uniformity, color quality, and chemical purity. In the United States alone, the combined production of natural and synthetic iron oxides produced sales of over $28,000,000 in 1970 (Stipp, 1970). Nomenclature With the increasing importance of the syn¬thetic iron oxides it is necessary to make a distinction between the natural or mineral pig¬ments and the synthetic pigments. Natural pigments are those products which are derived from selected ores and should not be confused with iron ores mined for steel production. Iron ores that are mined for steel must be capable of being mined and reduced to iron on a com¬mercial basis. These ores are selected on the basis of iron content and processing economics. It is therefore unusual when iron ores for steel production are suitable for use as mineral pig¬ments. Natural pigment ore sources are se¬lected for their special physical-chemical prop¬erties and can command a premium price. Synthetic pigments, and in this instance iron oxides, are those pigments produced from basic chemicals. Through chemical synthesis pig¬mentary sized particles are produced as opposed to comminution, the major procedure common to all natural iron oxide pigments.

Jan 1, 1975

By Y. Wang, M. M. Singh, H. L. Hartman

Knowledge of the state of stress at the bottom of a drillhole is of practical importance in rock drilling, since the induced stresses must exceed the strength of the rock in order to cause fracture. This note reports on a numerical method to determine the stress distribution at the bottom of a borehole induced by a static bit load and overburden and fluid pressures. The procedure adopted is similar to that for the plane-strain, discrete model employed by Harper and Ang.1,2 The rock medium is considered to be homogeneous, isotropic, and elastic-perfectly-plastic. METHOD OF ANALYSIS AND PROGRAMMING The discrete model adopted consists of two types of points: mass points and stress points. The configuration and numbering notation are depicted in

Jan 1, 1967

PUBLIC hearings began before the Committee for Reciprocity Information on May 24, 1950, for the purpose of unearthing data and opinion that will be helpful in the forthcoming reciprocal tariff and other trade-barrier negotiations at Torquay, England, on September 28th of this year. The conference this fall will constitute the "third round" of tariff negotiations under the General Agreement on Tariffs and Trade concluded at Geneva in 1947. The United States plans to negotiate with 17 other countries on possible tariff modifications on various articles all the way from baby carriages and bottle caps to lead and zinc-bearing ores. On May 31, June 1 and June 2, spokesmen appeared before the Committee for Reciprocity Information on behalf of the domestic lead and zinc mining industries. Producers of these metals protested the inclusion of paragraphs 391 (lead-bearing ores, dust and mattes), 392 (lead bullion, lead in pigs and bars, and scrap lead), 393 (zinc-bearing ores of all kinds), and 394 (zinc in blocks, pigs or slabs, and zinc dust) of the Tariff Act of 1930, as amended in the list of articles to be considered for possible tariff concessions at Torquay. It was pointed out that although operating costs have more than doubled since 1939 tariffs on these metals were actually higher in that year than at present. This, coupled with the detrimental effects of the recent series of devaluations, has sounded the death knell for a substantial number of domestic lead and zinc mines-a most undesirable development in the face of the ominous international situation, according to these spokesmen. It was urged that higher rather than lower tariff rates are needed on these metals. The opinion was expressed that it was inconsistent to foster a high living standard in our western areas and then, once it is attained, to undermine that condition by minimizing the protection that was partly responsible for it. The main theme of some arguments implied that although every effort should be made to close the "dollar gap" abroad, serious consideration must be given the methods employed lest our national security position be jeopardized in the process. The House Committee on Foreign Affairs completed hearings on H. J. Res. 236, to provide for United States membership and participation in the International Trade Organization. Hearings began on April 19th and ran for over five weeks. Many witnesses from industry and government presented voluminous testimony, which will not be available for public distribution for several weeks. However, it is no secret that the most controversial provisions of the Draft Charter of the ITO are: (1) Article 17 (Chapter IV on Commercial Policy) which would obligate members to negotiate for the reduction of tariffs and the elimination of trade preferences; (2) Article 20 which would prohibit the use of quantitative restrictions for protective purposes; (3) Article 16 which promulgates rules to implement the principle of non-discrimination in international trade; and (4) provisions permitting the use of protective measures for promoting economic development, particularly in backward areas, even though such provisions are inconsistent with those of the three articles cited above. United States membership in the International Trade Organization is essential to the successful operation of that body in view of this country's position as the economic giant in the present international trade pattern. Many countries are reluctant to take any action toward the ratification of the charter until it is known what course America will pursue. However desirable or undesirable the ideal of free multilateral trade may be it is unlikely that this Government's participation in the ITO will materialize soon. Advices in Washington indicate that H. J. Res. 236 will not be enacted during the present session of Congress. The legislative pattern designed to secure Congressional approval of the ITO is similar to that of the St. Lawrence Seaway project. The Seaway project was pending in treaty form for several years before the Foreign Relations Committee of the Senate and when the Administration decided to incorporate this project into bill form it was found that, while it passed the House promptly, the Senate decided to pigeonhole it because of the obvious intent to circumvent the constitutional prerogative of the Senate to advise and consent to the ratification of treaties. The ITO bill may be slated for a similar fate. It is deemed essential by western Senators and Congressmen that the present session of Congress enact some form of mining legislation before its adjournment, now set for July 31st. These legislators from prominent ore-producing states do not desire to return to their home areas in the fall emptyhanded. Aside from that, it is entirely superfluous to reiterate the necessity for maintaining a healthy domestic mining industry as a bulwark against a sharp rise in the temperature of the "cold war". Now that S. 2105 has failed a new bill is taking shape in the Senate Interior and Insular Affairs Committee. It is similar in language to H. R. 8221 (to encourage the conservation and development of the mineral resources of the United States) reported by the House Public Lands Committee on May 3, 1950, but so far has failed to receive approval of the House Committee on Rules. There are some qualified observers in high circles in Washington as well as in the mining industry who favor a tax incentive program to stimulate investment in mining enterprises, as opposed to a conservation and exploration program. The Bureau of Mines and the Treasury Department have undertaken a joint study to determine the need for modification of the tax laws as they apply to mining. The study is scheduled for completion before the end of the year, and appears to be supplementary to the investigation initiated by the National Minerals Advisory Council which culminated in the submittal of recommendations to the Secretary of the Interior in December 1949. The "cold war" is largely responsible for the increased demand for metals. Stock-pile purchases and heavy industrial demand due to military needs distort markets and disrupt normal price trends. Such activity has an unhealthy influence on metal production, luring some producers into a state of dependency on the continuation of this condition. When stock-pile objectives are met sometime in the future purchases must then come to a halt unless international "fireworks" are touched off. It can only be hoped that technological improvements and further mechanization of mines coupled with the stimulus of a rising population will offset the anticipated drop in industrial demand and cessation of stockpile purchases when the international crisis abates.

Jan 7, 1950

By S. L. Hoyt

ABOUT three years ago eight standard steels were prepared for the cooperative investigation of methods for oxygen analysis, sponsored by the Iron and Steel Division of the American Institute of Mining and Metallurgical Engineers and by the National Bureau of Standards. A preliminary report of the results was made at the annual meeting of the A.I.M.E. in February, 1936. ? This report showed the reliability of vacuum-fusion methods and further brought out certain advantages of the fractional vacuum-fusion method. The results obtained by the authors with the latter method will be discussed here, with some com-ments on the procedure for those who are interested in determinations of gases in steel. Some additional comments are offered on the use of the polarizing microscope for identifying the inclusions in the steel to check and amplify the findings of the fractional vacuum-fusion analysis. For details of the fractional method, see the paper by L. Reeve1.

Jan 1, 1937

By F. Banemann

In discussing the problem of abnormal magnetic polarization, C. A. Heilandl† emphasized the unfortunate fact that our knowledge of the geological and physical conditions relating to such occurrences is very limited and that a more detailed insight into their physical causes would be extremely valuable for interpreting measured anomalies. He also pointed out that to arrive at quantitative physical formulas that would express the conditions that cause abnormal polarization many more occurrences of the kind would have to be recorded. The first part of this paper is a contribution to such descriptions. Abnormal Magnetic Polarization in South Africa The occurrence was mapped in the course of a magnetometric survey carried out about 70 miles to the east of Johannesburg and east of the Witwatersrand gold field, for the purpose of detecting the position of the suboutcrop of certain magnetite-bearing shales that occur in the lower portion of the Witwatersrand system of sediments, shales whose position in section in relation to the ore-bearing members of the same system of sediments are known. In this case the shales are covered by younger strata several hundred feet thick. Lines of magnetometric traverse were run at right angles to the strike for a strongly magnetic body. This body is a shale zone in the Witwatersrand sediments and has a strike of N.20°E. (magnetic) and dips 15" to the east. The field work was done by a vertical intensity field balance (A. Schmidt principle). The plotting is done in such a way that the sign is reversed from that usually employed in the northern hemisphere, so that a positive profile is obtained in abnormal cases while the same conditions in the northern hemisphere would give a negative one. This method of recording should be kept in mind in reading what follows.

Jan 1, 1940

By F. Banemann

In discussing the problem of abnormal magnetic polarization, C. A. Heilandl† emphasized the unfortunate fact that our knowledge of the geological and physical conditions relating to such occurrences is very limited and that a more detailed insight into their physical causes would be extremely valuable for interpreting measured anomalies. He also pointed out that to arrive at quantitative physical formulas that would express the conditions that cause abnormal polarization many more occurrences of the kind would have to be recorded. The first part of this paper is a contribution to such descriptions. Abnormal Magnetic Polarization in South Africa The occurrence was mapped in the course of a magnetometric survey carried out about 70 miles to the east of Johannesburg and east of the Witwatersrand gold field, for the purpose of detecting the position of the suboutcrop of certain magnetite-bearing shales that occur in the lower portion of the Witwatersrand system of sediments, shales whose position in section in relation to the ore-bearing members of the same system of sediments are known. In this case the shales are covered by younger strata several hundred feet thick. Lines of magnetometric traverse were run at right angles to the strike for a strongly magnetic body. This body is a shale zone in the Witwatersrand sediments and has a strike of N.20°E. (magnetic) and dips 15" to the east. The field work was done by a vertical intensity field balance (A. Schmidt principle). The plotting is done in such a way that the sign is reversed from that usually employed in the northern hemisphere, so that a positive profile is obtained in abnormal cases while the same conditions in the northern hemisphere would give a negative one. This method of recording should be kept in mind in reading what follows.

Jan 1, 1940

By William L. Fink, L. A. Willey

Since so many different curves have been published for the solid solubility of zinc in aluminum, it seems desirable to definitely establish the correct curve by two or more independent methods. The curve published in part I1t was based entirely upon X-ray measurements because the other methods employed at that time were not satisfactory. The present paper (the seventeenth of this series on high-purity aluminum alloys) describes the determination of the solid solubility of zinc in aluminum by the measurement of electrical resistivity at temperature and by microscopic examination. Since the publication of our part I in 1932, an investigation of the solubility relations in the aluminum-zinc system has been reported by Schmid and Wassermann2, who obtained their solubility results from lattice-parameter measurements on heat-treated and quenched specimens. The diagram that they published is shown in Fig. 1. In this investigation they also found by X-ray measurements that the parameter of the gamma phase changed continuously with zinc content and at such a rate that it would be identical with that of the beta phase at 60 atomic per cent zinc. It was concluded therefore that the beta and gamma phases, from the point of view of structural relationship, are one single phase. They also suggested a gap of immiscibility between 270" and 350" C. The complete boundary in this region could not be determined satisfactorily by the method employed and therefore was not shown in their diagram. Aluminum-zinc Alloys Materials Used.—Electrolytically refined aluminum3 was used in preparing the alloys for the work reported in this paper. Chemical analysis showed the following impurities: 0.004 to 0.005 per cent silicon, 0.006 to 0.008 per cent iron and 0.005 to 0.006 per cent copper. Also,

Jan 1, 1936

By T. A. Rickard

The notion prevails that writing is a knack, that the skilful use of the pen is a gift of nature. This is an error. Dogberry may be responsible for it; he said: "To be a well-informed man is the gift of fortune, but to write and read comes by nature". Because Dogberry said it, we may be sure that Shakespeare thought otherwise. Ability of any sort may be partly innate, but my own observation and experience lead me to conclude that most of the easy writers have become so by constant practice. As I recall the names of men successful with the pen, I remember that most of them have written a great deal and have taken particular pains to improve their style. The suggestion that proficiency in the difficult art is a happy accident provokes a sardonic smile. The larger part of the great writing in our literature is the result of persistent effort. An easy fluency has been the undoing of many; their flamboyant and fantastic scribbling has proved as perishable as froth. This criticism applies to technical writing also; in order that a technical description or discussion may hold the interest of the reader, at least long enough to cause him to read it to the end, the writing must be done carefully and systematically; otherwise it will fail in its purpose of conveying information. Clearness is absolutely essential. "It is not enough to use language that may be understood; it is necessary to use language that must be understood."* The purpose of writing, at least of that which is meant to be read by others, is not only to express ideas but to communicate them. Lack of perspicuity may prove as %ad as

Jan 1, 1931

By N. A. Zeigler

Considerable work has been and is being done on the changes of physical properties that take place in alloys at elevated temperatures, and much information on this subject is published. Much less is known, as pointed out by Rickett and Woodll about reactions between the alloys and atmospheric gases and still less is known abut changes within the alloy itself under the influence of heat and given atmosphere. Moreover, most of the work published has been done on the alloys of "heat-resisting" type, in which chromium is an essential ingredient, the behavior of all other alloys being quite unknown, except perhaps of decarburization produced at the surface by oxidizing atmospheres. It has been shown2 that iron, with total amount of foreign ingredients not exceeding 0.01 per cent, if heated in an oxidizing atmosphere at above 900" C., may be saturated with oxygen to 0.1 per cent. It was suspected that something of a similar nature may take place in iron-silicon alloys (transformer material), the mechanism of such processes being either a direct diffusion of oxygen into the alloy, or oxygen combining with silicon to form SiO2 or more complicated (silicate) inclusions. Another possibility to be considered was that during annealing in oxidizing atmospheres, when scale is being formed, silicon may oxidize preferentially at the surface, thus impoverishing the alloy in silicon. In collaboration with Dr. T. D. YensenP3 the writer set out to investigate this problem about two years ago in order to settle these questions. Testing Procedure In the first part of the investigation, two pieces of 4 per cent silicon iron, prepared in hydrogen atmospheres and forged to 3/4-in. square bar,

Jan 1, 1934

By Lyle L. Marsh, David L. Douglas

CORRELATION was made between the heat treatment and hardness of three U-Ti alloys ranging in composition from 8.5 to 50 atomic pct Ti. The following important observations were made: 1) A direct quench of y U-Ti solid solution resulted in the formation of a hard martensitic phase in low-titanium alloys. 2) Subsequent tempering initially increased the hardness by the precipitation of a fine dispersion of U2Ti; further precipitation of U2Ti with tempering time eventually resulted in softening. 3) High-hardness levels were obtained also by isothermal transformation of an 8.5 atomic pct Ti alloy at 400º and 500°C. 4) The crystal structure of the phases present at the solution-treating temperature (one region in the phase diagram excepted) and the temperature within a given phase region affected the hardness of both quenched and isothermally transformed alloys. Introduction It has been known since 1887 that the mechanical properties of metals were dependent upon their microstructure. Sorby pointed out in that year that annealed gray iron castings were softer than chilled iron castings by virtue of the graphite which had replaced hard cementite in the microstructure. Over the years, interest has increased in the effect of microstructure on the mechanical properties of metals, and now high-strength levels may be achieved by bringing about the dispersion of a second phase or by other microstructural adjustments. The nature of a second phase in an alloy strongly influences the properties. For example, the size, shape, amount, and distribution of a second phase plays a very important role in the ultimate properties of an alloy. Microstructural control is achieved by heat treatments. Hence, any alloy system of potential use should be understood in terms of its response to heat treatment and the resultant effects upon the properties.

Jan 1, 1958

By Philip D. Anderson, Ralph Hultgren

Heat contents of extremely pure iron were measured over the range 300"to 1433"K, using a diphenyl ether calorimeter. Results from three samples containing widely differing impurities agreed with one another and with Previously reported results at higher temperatures (1184 ° to 1809°K) by Olette and Ferrier. From these data a table of heat contents of iron has been Prepared which is believed to be more accurate than those previously available. CP values have been derived which are consistent with these heat contents, with the best experimental Cp data, and with the thermodynamic conditions of equilibrium between bcc and fcc iron. The opinion is expressed that low-temperature extrapolations of presently known Cp values for y-Fe are not reliable. It would seem that the thermodynamic properties of iron, which is by far our most important metal, should have been well established long ago. This is not the case, however. As discussed by Olette and Ferrier,' there is objection to every earlier heat content measurement. While the best true Cp determinations agree well at temperatures below the Curie point, there is wide divergence at higher temperatures. Several investigators have examined available data and attempted to calculate thermodynamic functions for iron that are consistent with the two equilibrium temperatures of bcc and fcc iron. The two primary efforts were those of Austin' in 1930 and Darken and smith3 in 1948. The recommended values differ considerably; integration of Austin's Cp values leads to a heat content at 1100°K which is 300 cal per g-atom higher than the value recommended by Darken and Smith. The compilation of Fisher4 in 1949 was based on the selection of Austin. In 1956, Weiss and Tauer obtained yet another set of values by resolving Cp values into components due to dilation, lattice vibration, electronic excitation, and magnetism. The magnitude of contribution by each component and its dependence on temperature was estimated by semiempirical means. Their values are not self-consistent in that they do not form smooth curves when plotted vs temperature; moreover, their calculations cannot easily be repeated since they do not give the values of some of the parameters used. Clearly, experimental values for iron were in a most unsatisfactory state. The presently described measurements of the heat content of iron were therefore undertaken, covering temperatures as high as 1433°K. While the work was in progress, the high-temperature (1193" to 1789"K) heat content measurements of Olette and Ferrier' were published; in the region of temperature overlap the present results agree with Olette and Ferrier well within experimental accuracy. It is believed that the present results, combined with those of Olette and Ferrier, provide for the first time a reliable set of heat contents of iron from room temperature to the melting point. From these data, guided by available Cp measurements, it proved possible to derive Cp, entropy, and free energy function values for @-iron from room temperature to the melting point, and for y- iron in the temperature region of its stability. Exhaustive study led to the conclusion that extrapolations of y-iron functions to room temperature were not reliable enough to be useful; hence these have been omitted from the tables. EXPERIMENTAL Materials. Three samples of extremely high purity iron from different sources, containing widely different impurities, were measured. The first of these, designated "Chipman", was kindly supplied by Dr. K. K. Kelley of the U. S. Bureau of Mines from a lot which was made many years ago by Dr. John Chipman of the Massachusetts Institute of Technology. The second, designated6'Teddington", was supplied by the National Physical Laboratory, Teddington, England, from a lot zone-refined by them. The third sample, designated "Irsid", was supplied by the Institute de Recherches de la

Jan 1, 1962

By J. M. Sands

THE state of Kansas had a daily average crude-oil production of about 87,000 bbl. at the beginning of the year. This showed a steady but consistent decline during the 12 months, so that the daily average production at the end of the year was slightly over 68,000 barrels. GREENWOOD COUNTY THE most active development in Kansas during the year was in Greenwood County, in a line from near Sallyards in T 25-R 9 to east of Madison in T 22-R 11. The main part of this development has been in a succession of pools beginning at the south with the Polhamus pool in 34-24-9 and 3 and 4-25-9; Thrall pool in 28, 29, 32 and 33-23-10; Burkett pool in 13, 23, 24 and 26-23-10; Seeley and Wick pool in 22, 27, 28,. 32 and 33-22-11 and 5, 6, 7, and 8-23-11; Frohm pool in 11, 14 and 15-22-11; Madison pool in 31 and 32-21-12 and 6, 22, 12 and 1-22-11. Some of these pools have two or more sands, locally called Bartlesville and Burgess Sands. They range in depth from 1850 ft. near Madison to 2450 ft. near Sallyards, the general dip being to' the west. The thickness of these sands run from 20 to 100 ft., the initial production of the wells being 50 to 1000 bbl of 40-gravity oil or better.

Jan 3, 1924

By L. J. Howell, H. H. Kellogg

AN a previous paper' the phase diagram and vapor pressure of melts in the systems NaC1-ZrCl,, KC1-ZrCl,, and NaC1-KC1 (1:1 molar)-ZrC1, were reported. This note supplements the earlier paper with the results of electrical conductivity measurements on NaC1-ZrC1,and NaC1-KC1 (1:l molar)-ZrC1, melts. The design of the conductivity cell is shown in Fig. 1. Tungsten electrodes, A, were sealed into the Pyrex cell, C. That portion of the electrodes in contact with the melt was covered with a tight-fitting platinum cap. The electrodes were sur-

Jan 1, 1960

By Ernest F. Burchard

(Pittsburg Meeting, March, 1910.) IN connection with the work of testing structural materials for the use of the U. S. Government at the laboratories of the technologic branch of the U. S. Geological Survey at St. Louis, Mo., from September, 1904, to April, 1909, and since then at Pittsburg, Pa., large quantities of sand, gravel, and crushed stone have been needed from time to time, besides samples of building-stone, clays, and other quarry-products. In many instances it has been necessary to obtain single samples of sand, gravel, or crushed stone in lots of a car-load or more. For obvious reasons all these collections have had to be made by a representative of the Survey. As the work progressed it was found essential that numerous geologic data should be gathered regarding the materials collected, in order that they might be properly classified as to kind of material, source, geologic age, etc., and that they might be rated according to quantity available, accessibility to transportation facilities, approximate costs, suitability for special purposes, etc., and that notes might be taken regarding undeveloped deposits of possible value. Furthermore, it was desired that the selection of materials for tests should be made broadly, so as to cover, first, the representative types of material, and later, if possible, the typical materials of the more important building-centers in the United States. In order to insure a certain degree of uniformity in this work and economy of effort and expense, it was decided that as much of the sampling as was practicable should be done by a member of the. geologic branch, whose regular field-trips could be combined conveniently with those necessary for procuring materials for the laboratory. During parts of the last three years I have been engaged in field-work of this sort.

Jun 1, 1910

By Bunting S. Crocker

DISCUSSION Fred C. Bond (Allis-Chalmers Manufacturing Co., Milwaukee)—This is a very complete description of the screened ore fine grinding installation at Lake Shore. The only important data which might be desired are the operating screen analyses and power consumption in each stage. The statement that the energy consumption, or kw-hr per ton, remains constant for all mill diameters is of great interest, but the opinion is widely held that the kw-hr per ton decreases as the mill diameter increases. More definite test work is needed to establish this point. Screened ore fine minding has been successful on hard Lake Shore ore &d on about equally hard South African Rand ore. However, it is still not determined whether it would be successful on ores of average or less than average hardness. It is possible that with softer ores the consumption of ore pebbles might be exceedingly high, or might even exceed the available supply. Also, the softer feed might result in a rapid buildup of harmful intermediate sizes in the mill circuit. These factors can be determined only by a full scale or long pilot mill test. In any case the Lake Shore staff is to be congratulated for this pioneering work. Bunting. S. Crocker (author's reply)—As requested, the operating screen analyses and Bower consumption for each of the four stages of pebble milling are given, see Table XII. The fist three stages are in series circuit; the last stage is in closed circuit. The primary circuit had rock feed averaging 124 g per piece and the final stages rock feed weighing 63 g. The intermediate stages had mixtures of the two. Regarding Mr. Bond's statement that "the opinion is widely held that the kw-hr per ton decreases as the mill diameter increases," I would say that I have frequently been told this but have never yet been shown any evidence or seen any evidence published that would prove this statement. It may be true that some of the big mills recently installed have mechanical power savers such as micarta bearings and better lubrication, but as far as the power consumed inside the mill is concerned, we at Lake Shore think that it varies as D2 .", and that is all. We published extensive information on this point in our 1939 paper. Recently Mr. Banks at Consolidated published the figures on his 10 ft 8 in. x 12 ft 0 in. rod mill. As reported in this discussion by the writer: we calculated the power necessary to run this mill based on our 7x6-ft rod mill to within 1 pct of the actual power reported by Mr.

Jan 1, 1953