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By Richard M. Foose

MOST of the roofing granules produced in Pennsylvania are made by two companies at three plants. The Advance Industrial Supply Co. has three quarries and a mill at Gladhill Station, in southern Adams County. The Funkhouser Company is actively engaged in mining, quarrying and milling at Charmian, about one mile west of Gladhill Station, and at Delta, in southern York County. These three plants produced approximately 100,000 short tons of granules in 1943. The production of roofing granules in 1937 for the whole country was only about 500,000 tons, generally indicating the large growth of the industry since that time. The fundamentals of producing roofing granules were discussed comprehensively by G. W. Josephson in a paper before the Industrial Minerals Division in October 1943 (Mining Technology, March 1944). The purpose of this paper is to describe the actual methods of mining the rock and milling it to make roofing granules, as practiced by the three Pennsylvania plants. MINING AND MILLING Funkhouser Company (Delta) The Funkhouser Company, near Delta, in southern York County, Pennsylvania, operates three joined quarries and a mine in the Peach Bottom slate. The joined quarries extend 1200 ft. in a northeast southwest direction along the strike of the slate cleavage and are about 200 ft. wide. The working face is about 45 ft. high. The quarrying operation is rather simple: Ingersoll-Rand Jackhamers, 1-in. and 1 1/4-in., with hollow drill steel, are used to undercut the quarry face with10-ft. holes. The face is "blown" and allowed to slump on the quarry floor. Loaded by a Marion electric shovel into trucks, the shattered rock is taken to the primary crusher 2500 ft. away. In addition to the normal quarrying operations, a drift into the northeast wall of the middle quarry was begun about 1935 and has advanced about 2000 ft. since then. Rooms have been driven at angles to the drift along choice beds of slate. The drifts and rooms have a roof more than 35 ft. high and the main drift and rooms are all more than 40 ft. wide. There is no cribbing at any place in the mine. Several of the rooms were driven upward on a 5º slope and in some of them there was stoping. Ingersoll-Rand Jackhamers are used, and only wet drilling is practiced. When visited in January 1940, an electric shovel was operating at the head of the drift, scooping up the slate blasted out of the working face. This, too, is trucked to the primary crusher. Some of the better quality slate is saved for making slate shingles. The primary crusher, which is a No. 30 McCulley gyratory, receives the slate from the trucks and crushes it to about 2-in. size (Fig. I). This product travels by a 30-in. belt conveyor to Niagara vibrating screens with 2-in. holes. The minus 2-in. product moves to a storage silo by bucket

Jan 1, 1945

By R. F. Yap, N. Arbiter, C. C. Harris

A fully-instrumented driving mechanism has been constructed to study the power, aerating and solid suspension characteristics of several laboratory flotation machines. Machines operating over normal flotation speed ranges give substantially constant power numbers in liquid systems indicating that they operate close to fully baffled turbulent flow conditions. Owing to lack of geometrical scaling, power numbers for different sizes of cells of the same make are different. Even larger differences occur between cells of different manufacturers. For a given impeller, varying the tank size did not significantly affect the power consumption. Tank geometry and baffling has a slight effect on power consumption with shrouded impellers. For a given impeller speed, suspension height decreases while power increases with increasing mass of solids in suspension. While power consumption is hardly affected by particle size and clearance between the impeller and tank bottom, the suspension height significantly increases as clearance increases and as particle size decreases. Aeration was found to affect not only power but also the suspension characteristics of the machine. For closely sized particles, drastic sedimentation occurred when a critical value of the air flow number was exceeded. The critical air flow number decreased with increasing particle size. This effect was less marked with a wide particle size range. The self-aerating capacity of flotation machines increases with cell size at a given speed for the same impeller-shroud system, but decreases in the presence of frother and solids. Equations have been established for correlating all of the studied variables. Data taken from the literature were also correlated with these equations. The modern mechanical flotation machine has, over a period of 60 years, displaced other designs to become the dominant type. Once the correct chemical environmental conditions have been established, the major requirement, selective mineral-air adherence, is essentially a function of two operating variables — impeller speed and air rate. The special nature of this dependence is such that in the same apparatus, but under different operating conditions, adherence can be either prevented or destroyed. Another aspect of this observation is that flotation machines though differing in detail to a considerable extent can produce similar metallurgical results. It must be concluded that having determined the correct reagent levels, establishing the correct operating conditions are at least as important as machine design. Since about 1960, after 30 years of fairly stable circumstances, manufacturers have been developing new types of machines whose major feature is emphasis on pulp flow characteristics by virtue of new im-peller-stator designs. As far as can be ascertained, these new designs necessitate radical departures from accepted impeller speed-air rate values. Performance data are still awaited. Flotation machine development has been empirical, as is selection of operating conditions. The purpose of the work at Columbia University has been to elucidate the fundamentals of the subject so that the purely mechanical aspects of the flotation process can be understood in hydrodynamic terms.1-6 Hopefully, this might lead to intelligent selection of a particular machine and its operating conditions for a specific ore based on a minimum of testing, or even to new types of flotation machines. The present investigation is the most comprehensive to date.7,8 Earlier work, which was largely exploratory, has been repeated and extended and employes the most accurate measuring techniques available. Additionally, sufficient hydrodynamic data were obtained under flotation conditions to delineate the relevant operating ranges. Attention has been given to scaling in that several geometrically scaled tanks and impellers have been constructed and tested; it has been pointed out elsewhere that undistorted geometrical scaling rarely pertains in flotation machine design.5 This paper is divided into sections dealing with relevant combinations of the three phases: liquid, air and solid. Summaries of the literature have been given in previous publications2-4 and will not be repeated here. Recently, several reviews of mixing have appeared, which can be usefully referenced.9-11 It is of interest to note that flotation is not included

Jan 1, 1970

As already announced, the Arizona Meeting of the Institute is to be held from the 18th to the "25th of September. There will be a special train from New York City to Arizona and return, to take members and guests of the Institute to the meeting., The Committee in charge consists of Walter Douglas, Chairman, Cleveland E. Dodge, John C. Greenway, Arthur S. Dwight and Julius Kruttschnitt, Jr., and while the plans of this Committee are not complete, it may he announced that 'the train will be run with the requisite number of Pullman, dining and baggage cars to accommodate those who desire to go, which will accompany the party during the entire week of the Arizona Meeting as per the following program, including, of course, the visit to the Grand Canyon. It is especially desirable that the Committee should know, at as early a date as possible, the number of those who desire to make the trip; and those who desire special accommodations such as drawing rooms, state rooms, etc., are especially requested to communicate as soon as possible with the Secretary of the Institute, stating the number in their party.

Jan 6, 1916

MINERAL INDUSTRY EDUCATION DIVISION Established as a Division January 15, 1932 Harry H. Power, Chairman J R. Van Pelt, Vice-Chairman J. Donald Forrester, Secretary-Treasurer Missouri School of Mines and Metallurgy, Rolla, Mo

Jan 1, 1952

By JAS. F. McCARTHY

THE present Hecla Co. is a Washington corporation; the Hecla Co. of Idaho was the old company. The older corporation owned two claims, the Hecla and the Katie May, and was incorporated for 500,000 shares of one dollar par value. The principal shareholders and officials of the older company were among the early mining men of the camp. Among the active officials were John A. Finch and A. B. Campbell. Among the directors and share- holders were Patrick Clark, J. R. Smith, Frank Upman, F. J, Kipp, Chas. Kipp, B. A. Kipp and Carl Landsee. F. J. Kipp and Carl Landsee are now directors of the Company. All of the others mentioned have died, but the surviving members of their families retain their ownership in the Company's shareholders. B. A. ,Kipp, who recently died, was the largest shareholder at the time of incorporation and Patrick Clark was the second largest shareholder. B. A. Kipp is a brother 'of F. J. Kipp, director of the Company.

Jan 1, 1924

By John Jermain Porter

(San Francisco Meeting, October, 1911.) THE value of any particular ore, coke, or limestone, for iron-making, depends upon its effect, first, upon the quality or value of the resultant product; and second, upon the cost of smelting. The factors under the first head are the percentages of phosphorus, manganese, and other elements, which remain in the pig-iron ; while those under the second head are the percentages of iron, carbon, or lime, the slag-forming constituents, which must be fluxed, and any other ingredients which give rise to variations in cost of fuel and flux. The first of these criteria of value is perhaps not capable of being reduced to a general formula embracing all cases, since it must vary to a great extent with market-fluctuations. For example, Bessemer pig is worth sometimes more and sometimes less than foundry-pig ; and the premium paid for high manganese varies within wide limits. The second, or smelting-value, however, can be expressed numerically with a fair degree of accuracy; and it is with this phase of valuation that the present paper is concerned. The utility of a means of comparing numerically the relative smelting-values of different ores, cokes, and limestones, is self-evident, although it may not have importance in Northern practice, where materials are largely standardized. On the other hand, there are, especially in the South, many furnace-managers who must use a great variety of materials of widely varying grade; and it is with special reference to this district, and in connection with the efficiency-methods which I have elsewhere proposed,1 that the methods herein described were devised.

Mar 1, 1912

By R. V. Lundquist

Leaching manganese-bearing materials with NaOH to remove caustic-soluble silica has been demonstrated as a method for up- grading manganese. Those materials containing opaline varieties of silica respond most readily. Spent leach liquors are regenerated by treatment with lime to precipitate calcium silicate and to reactivate the NaOH for leaching.

Jan 4, 1953

By Sir Albert E. Kitson

The manganese ore deposits of the Gold Coast, British West Africa, occur in very ancient rocks, of both sedimentary and metamorphic types. In certain respects they have a strong resemblance to those of India and Brazil, as contrasted with those of Tertiary age in Georgia, but in this paper no careful comparison with them can be made. Viewed from the present condition of the manganiferous rocks, the oldest deposits are in the sediments. Later than these are the progressively metamorphosed representatives of these sediments. Youngest are the products of decay and degradation with the concentration of manganese oxide in the rocks of both groups. The oldest occurrences are in argillaceous and siliceous phyllites and slates, which show only a moderate degree of metamorphism. They belong to a series which also includes mudstones, sandstones, grits, conglomerates and subordinate limestones, with tuffs and lava-flows, largely of basic types. This has been named the Birrim System. Its age is unknown, for no definite fossils have been discovered in it. Since these non-fossiliferous strata at many plaees are of a character which in many parts of the world are suitable for the preservation of fossils, and which contain them, it is assumed that the Gold Coast deposits are pre-Cambrian. These rocks of the Birrim System have normally a northeast-southwest strike, and are folded, but not to any very great degree except in certain belts. From the Eastern Province of the Gold Coast they may be traversed diagonally across their strike for upwards of 600 miles, to the extreme northwestern corner of the Northern Territories. Thence they probably extend much farther into French territory.

Jan 1, 1927

Discussion of the paper of E. G. Woodruff, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 78, June, 1913, pp. 1001 to 1010. F. A. LINFORTH, Butte, Mont.:-I have not had an opportunity of reading this paper thoroughly, but I would like to call attention to the possible use of the contours on fault planes. It is obvious that if the contours of fault surfaces call be determined, we will be able to determine the axes of the hollows in the fault surface. It seems probable, and there are examples to point to the accuracy of, the assumption, that the axes of these hollows may be the direction of movements on the faults, and if that is true it will aid materially in locating faulted ore bodies or the shoots of ore on the opposite sides of faults. A few such contour maps of faults have been attempted on some of the faults of the Butte district, and those faults which are believed to have the nearly normal movement exhibit for the axes of these hollows a line nearly up and down in the plane of the fault, but in those cases where the throw is believed to bee nearly horizontal we find that the axes of the hollows are almost horizontal lines. In other words, the movements on faults, I believe, would be more nearly indicated by the larger grooves in the fault surfaces than by the small slickensides and minor hollows that are seen, so that contour maps might be valuable in geology in that way. C. W. GOODALE, Butte, Mont.:-I received a letter from Mr. Woodruff asking me to take part in the discussion of his paper, but I have not had time to give the paper any study. I can certainly add my opinion to that of all the engineers here that the topographic maps of the government are of great aid to the engineer. When I visit a new district, the first thing I do is to see if that district has been covered by the U. S. Geological Survey avid if topographic map has been issued. And I find that some of the younger engineers frequently come into my office to see if I have such maps. I know in some cases the reports made out by engineers contain copies of these topographic maps, or clippings from them. I am sure that. the topographic maps furnished by the government are of very great value to our engineers.

Jan 11, 1913

By M. J. Bradley, P. H. Dike

THE art of melting nonferrous metals, in smelting, casting, and in compounding of alloys, is highly dependent on a knowledge of the temperature of the metal. This knowledge may reside in the experience and judgment of the melter, or it may be based on measurement by suitable instruments. It-is our purpose to discuss briefly the instruments available for such measurements, and more at length the present, practice in molten metals, without recommendation. In the limits of time and space allotted, we can do little more than mention the available methods of measurement that are directly applicable in this field. In the 1939 edition of the Metals Handbook, issued by the American Society for Metals, pages 285-310, there is a more extensive discussion of pyrometry than can be attempted here, which should be referred to for details we must omit. For reasons that will appear, thermoelectric pyrometry will constitute the major portion of our discussion of the subject, only limited attention being given to radiation or optical pyrometry. METHODS OF MEASUREMENT THERMOELECTRIC PYROMETRY A thermocouple consists of two dissimilar wires, or a wire inside a tube of a dissimilar material, joined together at one end, which is placed in the region or medium where the temperature is to be measured, while the other ends are connected through suitable lead wires to a voltage-measuring device, which may be a millivoltmeter or a potentiometer. An electromotive force is generated in the circuit, which is proportional to the difference in temperature between the hot junction and the junctions of the lead wires to the measuring instrument. If this latter temperature is maintained constant, the e.m.f. measured varies only with the temperature of the hot junction. Every thermoelectric pyrometer is calibrated for a particular cold-junction temperature such as 0°F., 32°F. or 75°F., but usually it is more practical to compensate instrumentally over the probable range of cold-junction temperatures than to maintain the junction at the particular temperature for which the instrument was calibrated. Thermocouple Materials Only a very few pairs of metals are in frequent use for pyrometric measurements. The most generally used are iron-constantan for temperatures up to 1500°F. in oxidizing and up to 1800°F. in reducing atmospheres and chromel-alumel, which may be used in oxidizing atmospheres at temperatures up to 2400°F. for intermittent service. The accuracy of the latter deteriorates rapidly at temperatures above 2200°F. Platinum vs. platinum-rhodium thermocouples may be used up to a temperature of 3000°F , but they are easily contaminated by slow absorption of

Jan 1, 1946

By Persifor Frazer

The accompanying diagrams represent a lamp provided with certain improvements which render it more serviceable for the use of the engineer or other mining official who is often compelled to visit several mines a day remote from each other, and may be called on to use the magnetic needle in any or all of them. These requirements demand that the material of which it is made should be copper, and that it should be capable of being closed oiltight, for emptying and refilling the lamp at each mine would be a less expeditious as well as a less cleanly process, and transporting a lamp of the ordinary kind over rough roads on horseback or in wagon, would result in spilling the greater part of its contents. The general form of the lamp, including the false back to keep

Jan 1, 1882

HOW the Engineers' Memorial clock and carillon at Louvain has impressed the people of that city is indicated by the following letter sent by the Secretary of the University of Louvain to the Secretary of the United Engineering Society. We are still full of the memories of that splendid July 4, when we came into such .delightful contact with our American friends and more specially with the representation of the engineering societies of the United States. It was a great joy for all the members of the University to see those, American friends who have given to us such a splendid memorial in honor of- the brave men who fell in the Great War.

Jan 1, 1928

By H. B. Goodrich

Anthony I?. Lucas died suddenly at his home in Washington, D. C., on Sept. 2, 1921. Captain Lucas, as he was known to us, was born in Dalmatia, Austria, in 1855, of Montenegrin ancestry. He was graduated as an engineer at the Polytechnic of Grate and served in the Austrian Navy as second lieutenant. In 1879, he obtained leave of absence and visited an uncle in the United States. After an extension of this leave of absence, in order to undertake an engineering engagement in the lumber district of Michigan, where he resided, he decided to become an American citizen. He was naturalized in May, 1885. His name was Luchich, but as his uncle had adopted the name of Lucas, which was more easily pronounced by Americans, from his entrance to this country, he used this Anglo-Saxon form. Without knowing this fact, upon first meeting him a person was sometimes surprised to note the rather Germanic pronunciation of the Captain. Although he subsequently revisited Austria with Mrs. Lucas, he made his permanent home at Washington, D. C. His son served with distinction in the A. E. F. during the World War. His activities in this country as a mining engineer were at first in Colorado and later in salt mining at Petit Anse and Belle Isle, La. During his salt investigations, his attention was directed toward the possibility of oil in the Gulf Coast region and in January, 1901, his well, the "Lucas Gusher," on Spindle Top, Tex., started a new era in the oil business and his reputation as discoverer made him famous throughout the world. Captain Lucas became a member of the A. I. M. E. in 1895. During 1914, 1915, 1918, and 1919, he was chairman of the Petroleum and Gas Committee of the Institute and was at all times prominent in Institute affairs. As to the personality of Captain Lucas, the lasting impression is of a courteous hospitable gentleman, genial, affable, obliging, and helpful with his advice br assistance to any colleague. He was sincere, honest, firm against all obstacles, backing his judgment with his own hard work along any course which he had determined to be correct. His value in the engineering world lies mainly in the petroleum industry. In the oil business all wild-catters are pioneers that deserve credit and gratitude upon their success. There are, however, names that particularly stand out in our history. Drake conquered such obstacles as ridicule, lack of finances, and started the oil business. In 1901, Captain Lucas had the conviction that Spindle Top, a dome rising about 12 ft. above the coastal prairie south of Beaumont, Tex., contained commercial oil. He was scoffed at by practical oil men of the East. Noted geologists

Jan 1, 1921

Established as a Division February 22, 1928 J J Golden, Chairman M Tenenbaum, Past Chairman Gerhard Derge, Chairman-Elect R W Shearman, Secretary-Treasurer AIME, 29 West 39th Street New York 18, N Y

Jan 1, 1960

By William Hume-Rothery

MR. CHAIRMAN, LADIES AND GENTLEMEN: I need not say how much I appreciate the honor of being asked to lecture to you, and how much I would thank you for your kind invitation. It is encouraging to feel that the abnormal restrictions of the war have been relaxed sufficiently to allow a free exchange of scientists between our two countries, and I hope that some of you will be persuaded to go to England, and to visit us at Oxford, so that I may repay a little of the kindness I have received from you. As this is one of the first lectures since the end of the war, I have thought it well to describe some of the advances in the theory of alloys which were made in the years between the two World Wars. From the point of view of theoretical science, these years have been of outstanding interest in the history of metallurgy. They have been years in which the development of new and more accurate experimental methods has led to the revelation of many new facts. At the same time, the theoretical developments have enabled some of these facts to be viewed as parts of a general scheme, and we may say that some of the foundations of metallurgical science have been laid. This work was naturally stopped by the Second World War, and it can therefore be reviewed as one definite stage in the development of our Science. To illustrate the new advances, I shall deal mainly with the alloys of copper and silver, since these have revealed many of the general principles. SOLID SOLUTION At the beginning of our period, the first steps in X-ray crystal analysis had been taken, and copper had been found to crystallize in the face-centered cubic structure (Fig I). The determination of this structure naturally was of immense importance in the understanding of our subject, because it meant that we were at last in a position to appreciate the underlying structure out of which the crystal of copper was built. The earlier science of metallography had shown that in many alloys of copper the addition of a second metal in not too large proportions resulted in the formation of a homogeneous alloy which was regarded as a solid solution of the one metal in copper. Fig 2, for example, shows the so-called equilibrium diagram of the copper-zinc alloys, and here you will see that there is a solid solution of zinc in copper extending to something of the order 35 to 40 at. pct zinc.

Jan 1, 1947

By J. L. Kenty, J. P. Hirth

The concept of a critical super saturation, below which the nucleation rate is essentially zero and above which it is essentially infinite, is discussed with reference to vapor-solid nucleation. The necessary and sufficient conditions deduced for observations of this type of behavior are: 1) the nucleation rate must exhibit a sharp dependence on super saturation, 2) the growth rate must be sufficiently large that nuclei become observable in the time period of the experiment, and 3) the number of highly preferred nucleation sites must be small. Experiments reveal that the nucleation of silver on sodium chloride is visually detectable at all experimentally accessible super saturations and does not exhibit critical nucleation behavior. Failure to observe a critical super saturation is attributed to the insensitivity of nucleation rate to supersaturation as a consequence of the particular values of the contact angle and the surface free energy for this system. THE concept of a critical supersaturation, below which the nucleation rate is essentially zero and above which it is essentially infinite, arises naturally in homogeneous nucleation theory. Experimentally this type of behavior has been found by Volmer1 and others for water and other low surface tension liquids, as reviewed by several authors.2'3 The same type of behavior has been predicted and observed for heterogeneous nucleation of solids by Yang et al.4 and others,596 as also recently reviewed.2,7,8 In the work reported here on the heterogeneous nucleation of silver on NaC1, however, no critical super-saturation was found. Similar observations have been made recently for other systems.9-11 These results led to a reexamination of nucleation theory which revealed that there are conditions for which critical behavior is not predicted, either for homogeneous or heterogeneous nucleation. Although heterogeneous nucleation is of primary importance in this paper, some insight into critical behavior for such a case can be gained by considering homogeneous nucleation. Accordingly both types of nucleation theory are reviewed briefly. The requisite conditions for critical supersaturation behavior are then considered. The experimental results for the nucleation of silver on NaCl are presented and interpreted in terms of the theoretical presentation. REVIEW OF NUCLEATION THEORY There are essentially two approaches to nucleation theory, the so-called classical theory involving the concepts of bulk thermodynamics, and the statistical mechanical theory in which nuclei are regarded as macromolecules. The classical theory is based on the work of Volmer and Weber12,13 and Becker and. Doring14 and has been extended by Pound et al.15 The crucial assumption in the classical theory is that the small clusters or nuclei can be characterized by the same thermodynamic properties as those of the stable bulk phase. Thus, the nuclei are assumed to have a surface free energy, y, and a volume free energy of formation (relative to the vapor phase), ,, identical to that of the bulk. For deposition under low super-saturation conditions, the nuclei are large and this assumption is satisfactory. However, in many cases of interest, the nuclei contain only a few atoms and this assumption is highly questionable. The statistical mechanical models originated, for the specific case of a dimer as the critical nucleus, with the work of Frenkel16 and were extended later to larger sizes by Walton,17,18 Hirth19 and, more recently, Ht Zinsmeister. These models describe the nucleus in terms of a partition function, the estimation of which is tractable for clusters of 2 to 10 atoms, but extremely difficult for clusters larger than 10 atoms. Although the classical and statistical mechanical models are expected to apply for the limiting cases of large and small nuclei, both are uncertain for intermediate sizes. In this paper we shall treat only the classical model, recognizing that it is exact only for large nucleus sizes and regarding it as a phenom-enological description for small nucleus sizes. When analyses of experimental data using bulk properties show the nucleus size to be small, the resulting parameters should be regarded as largely empirical parameters describing the relative nucleation potency of the system. Considerable justification for the continued use of classical theory is provided by its general success in predicting nucleation behavior as a function of supersaturation and temperature. We emphasize that the qualitative features of the statistical mechanical models, particularly the critical super-saturation behavior that is central to the present work, are the same as those of the classical model. Of course, potential energy terms and surface partition functions replace the volume and surface energy terms of the latter model. The most recent versions of classical nucleation theory have been extensively reviewed.2,3,7 so that only the results are presented here. For homogeneous nucleation of a condensed phase from the vapor phase, the volume free energy change is ?Gv=vrT = =^ln£ [1] where v is the molecular volume of the condensing species. The supersaturation ratio,

Jan 1, 1970

By George Holderer

THE Enos Coal Mining Co. owns an area underlaid by coal, of approximately 5000 acres. This property is situated 9 miles from Oakland City, in the southern part of Indiana. The mine has been in operation 5 years, during which time some 350 acres have been stripped, and stripping is now proceeding at the rate of about 100 acres per year. TOPOGRAPHY These coal lands consist of gently-rolling agricultural fields which in times past were farmed for wheat. There is no timber and but very little brush to contend with. The overburden varies from 10 to 60 ft. in depth. A thin bed of slate overlies the coal, followed by limestone, which varies from 3 to 15 ft.; this, in turn, is followed by sandstone, slate, shale and clay. There is a very wide variation in the thickness of all of these beds. The coal has an average thickness of 5 ft., and is a good grade of high-volatile bituminous. MINING OPERATIONS Briefly, the sequence of operations is: drilling holes with churn drills; blasting with L. 0. X.; stripping overburden to uncover coal and, finally taking up the coal, which is sent to a tipple for cleaning and sizing. In order to show what is being accomplished by the use of L. 0. X., results will be shown from May to November, 1926, inclusive, and compared to the same period in 1925. No work was done in No. 1 pit during May, 1925, hence all figures are unduly low for this month. Drilling There are in use 8 No. 44 Loomis clipper drills, caterpillar traction with gasoline engines; recently these were equipped with extra heavy stems, measuring 26 ft. overall and 4 ½ in. dia., to increase the speed of drilling. In addition, 4 No. 1 ½ G non-traction drills have been acquired, and are used to save the time of the larger drills when recleaning is necessary.

Jan 1, 1927

By D. Argyriades, G. Derge, G. M. Pound

The electrical conductance of molten FeS was studied as a function of temperature and composition. It was found that stoi-chiometric FeS (36.5 pct S) shows a minimum specific conductance of 400 ohm-1 cm-1. For the Fe-rich melts the conductivity increases with increasing amount of iron to about 4850 ohm-1' cm-I at 26 pct sulfur. For the sulfur-rich melts the conductivity increases with increasing amount of sulfur until it reaches a maximum of 1300 ohm1 cm-1 for 37.4 pct S and decreases to 800 ohm-1 cm-1 for 38.3 pct sulfur. It is concluded that molten stoichiometric FeS is an intrinsic semiconductor in which the forbidden gap in the electron energy level diagram is quite narrow. Excess sulfur acts as an acceptor impurity in providing a component of positive hole conduction, while excess iron acts as a donor impurity to increase the n-type conduction. K. Bornemann and G. von Ftauschenplatl used a four-terminal, direct-current cell to study the electrical conductance of molten copper sulfide. Their measurements showed a high conductivity, of the order of 100 ohm-1 cm-" and a positive temperature coefficient. From electrolysis studies, Savelsberg2 concluded that molten Cu2S and molten FeS are electronic conductors. Further. he found that molten FeS has a high specific conductance, of the order of 1500 ohm-' cm-', and a small negative temperature coefficient. Pound, Derge, and Osuch,3 using an ac Kelvin circuit and a four-terminal cell, measured the specific conductance of molten Cu,S, molten FeS, and various mixtures. They found that the specific conductance of the solutions followed a roughly additive rule of mixtures. Yang, Pound, and Derge4 showed from electrolysis measurements that the mechanism of electrical conduction in molten Cu2S, FeS, and mattes is primarily electronic. Further, they observed that small additions of CuCl suppress the electronic conduction whereupon the system behaves ionically.

Jan 1, 1960

By W. Mostowitsch

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

Jan 1, 1917

By Victor De Ysassi

THE iron mines of Spain are located on the mountain ridge forming the boundary between the, Teruel and Guadalajara provinces, called Sierra Menera. They form a property of 25 mines extending over an area of 1,677 hectares (4,140 acres) situated at a height varying from 1,200 m. (3,940 ft.) to 1,500 m. (4,920 ft.) above sea level. The deposit follows the direction north to south; huge masses of ore are being found both on the slopes and at the summit of the Sierra. The ore occurs among quartzites and magnesite limestone, in some places overlaid by quartzite 15 in. (50 ft.) thick; in some others (and this is more general) the ore is overlaid by earth and boulders of quartzite origin,; this layer is about 8 m. (26 ft.) thick. The ore beds occupy the geological horizon of the Superior Trias or Muschelkask, which are here in direct contact with the Silurian quartzites. The lime-stones have been more or less transformed. There is ample evidence to show that these mines were worked in very ancient times-objects and tools employed in mining by the ancient Romans and Arabs are to be found plentifully in old workings which extend down into the deposits. It has been estimated that more than 10,000,000 tons of ore were mined in the old days in this district and carried to the primitive forges in the vicinity where iron of much renown in Spain was extracted. Remains of more than 20 of these forges are found in the neighborhood of Sierra Menera and are usually situated near waterfalls and forests. Much investigation has been carried on for the purpose of determining the quantity of ore to be found in these mines, but no exact calculations can be made at present. When the investigation is completed it will surely be found that the deposit contains a much larger quantity than the 100,000,000 tons indicated by the present workings.

Jan 2, 1916