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By J. F. Myers, F. M. Lewis

The paper reports the development of a large, slow speed ball mill closed circuited with a hvdro-scillator. This increased grinding efficiency 28 pct over conventional units. AS the title indicates, this is a progress report for the first year of experimental operation of a relatively large diameter, slow speed ball mill with 1-in. balls, with and without various classifiers, and including a hydroscillator. Several years ago the authors came to the conclusion that if any further progress were to be made in our flotation process, an understanding of the chemical and physical reactions and the control thereof, in the grinding circuit, was essential. It may be stated, at this point, that the preparation of a correct feed for the flotation process is still the number one objective of our grinding studies. This progress report deals with grinding "per se," and not with the chemical and physical reactions as the result of grinding. Prior to this time we had taken the naive position, that since grinding had been practiced by the industry for some fifty years or more, it had been well exploited and developed by a host of investigators. Consequently, we had given the matter only superficial attention. At the start of our study, we were aware of the fact that some difference in opinion existed, but we were not prepared for the controversial evidence that developed nor for the extent to which the experts differed in their viewpoints. There seemed nothing else to do but to tour the continent and decide for ourselves what was right and what was wrong, read all the published literature and visit with anyone who had ideas about the matter. This we did over the next few ensuing years. Since our study has met with some measure of success, we report, herewith, these data that ultimately they may be of help to other investigators. In 1944 it became necessary to increase our grinding capacity and at the same time to grind the sulphide portion a little finer. This provided the impetus to put our ideas into effect. As has been previously described, our grinding flowsheet at that time consisted of a 6x12 rod mill, followed by two 5x10 ft, and one 6x12 ft trunnion overflow ball mills, with conventional rake classifiers. Naturally, we first considered all the possibilities of altering or adding to the existing equipment. It became evident that if any appreciable increase in grinding efficiency could be obtained, it would pay to scrap the existing small mills and classifiers and install one big mill with adequate classification. Trying to determine just how much more efficient a big mill could be, in which were incorporated all

Jan 1, 1951

By John J. Borkert, Carl E. Gerity

In situ mining offers a new and proven method of exploiting sedimentary uranium deposits. The feasibility and economic evaluation of exploiting a uranium reserve by either open pit or underground mining should also include a similar study for in situ mining. This report compares the economics of mining several hypothetical uranium deposits at various depths, grades and reserve sizes by open pit and in situ mining. The evaluation process evolved establishing, where possible, common geological and logistical parameters to both methods of mining. The various assumptions that are unique to either open pit or in situ mining were also drafted, where possible, as equal and common functions to be used in each economic evaluation of the reserve models. After the various parameters were defined, they were programmed to an economic analysis of the various hypothetical uranium deposits by the selected mining method. From the vast array of cost evaluations, total capital and operating cost per pound U308 produced, DCF-ROI, and total net profits before State and Federal taxes were selected as the most meaningful results to compare. From the various geologic parameters used, it was determined that the economic viability of a mining venture is most sensitive to a depth-grade thickness ratio. The three selected evaluation products were plotted against the various depth-grade thickness ratios of the hypothetical uranium deposits. The results of the economic cost analyses show in situ mining generally to be a better method to maximize total net profits and to maximize return on investment.

Jan 1, 1979

Discussion of the paper of J. E. Johnson, Jr., The Effect of High Carbon on the Quality of Charcoal-Iron, presented at the Cleveland meeting, October, 1912, and printed in Bulletin. No. 74, February, 1913, pp. 173 to °14, and of the paper of Albert Sauveur, Notes on Cast-Iron, presented at the New York meeting, February, 1013, and printed in Bulletin No. 75, March, 1913, pp. 503 to 524. CHAIRMAN. JOHN BIRKINBINE :-Just 20 years ago I had the pleasure, when I retired from the Presidency of the Institute, of introducing my successor, and this afternoon it is my pleasure to ask my good friend Dr. Howe to open this discussion. PROFESSOR HENRY M. HOWE, New York, N. Y. :-This paper of Mr. Sauveur's is extremely interesting. It is one of those papers that one wishes to read in the quiet of one's study, where it can be read with great profit. There are many points which he makes which I think are of very great value, in particular as to the importance of getting fine ;grained graphite by a relatively rapid cooling, combined with a high percentage of silicon. That theory would seem to be very promising; how far it has actually been carried out very likely Dr. Moldenke can. tell us.

Jan 5, 1913

(The following list contains the names of those members of the Institute of whose connection with military service. we have only recently become acquainted; it also includes the names of a few who have recently been promoted or transferred. A complete list was published in the Year Book, issued as a supplement of the Bulletin for March, 1918.) ADAMS, HENRY, Major, Assistant to Department Engineer, North-eastern Dept. ALINE, P. A., Co. C, 316th Supply Trains. * Low-cost cottage construction in America; a study based on the housing collection in the Harvard Social Museum, by Winthrop A. Hamlin. Cambridge, Mass., Harvard University, 1917. (Publications of the Department of Social Ethics, No. 7.) 30 pp., 4 charts. Illus.

Jan 5, 1918

By D. S. Greig

There was a decline in the Italian oil production in 1933 and also in the footage drilled. A total of about 194,500 bbl. of crude oil was produced in the Emilia district of northern Italy from the same fields in production as in 1932. New drilling to the extent of 80,700 ft. failed to find new production to compensate for the decline in old wells, and no new fields were discovered in spite of an active exploration campaign by the government-owned company A.G.I.P., which has just completed the first year of a five-year exploration program. This company drilled a total of about 33,000 ft. The majority of its tests were drilled in the Po Valley upon locations selected by geophysical methods. This company is changing over to the rotary system for all future wells. It produced about 16,600 bbl. of oil from wells near Salsomaggiore and in the Po Valley. The Petroli d'Italia, which operates the old fields of Montechino, Valleja and Gratera south of Piacenza, has been doing normal development drilling in the endeavor to extend its present fields. Also it was drilling two exploration wells in the Torino district. It drilled a total of about 13,930 ft. and produced approximately 12,645 bbl. of very high-grade oil (specific gravity about 0.765). The Societa Petrolifera Italiana was occupied chiefly in exploratory drilling in the endeavor to extend its producing fields at Salsomaggiore and at Vallezza, south of Parma. It was also drilling one exploration well at Rile dell7Olio near Voghera on the line Milan-Genoa. It drilled a total of 33,849 ft. and obtained a production from its two fields of 165,273 bbl. It also produced 123,220 gal. of casinghead gasoline from Vallezza field absorption plant.

Jan 1, 1934

Jan 1, 1943

By Carl E. Johnson

INTRODUCTION A method for predicting water-flood oil recovery was reported by H. Dykstra and R. L. Parsons' in 1950. It is now generally known as the Dykstra-Parsons method and is widely used by petroleum engineers. The method is semiempirical and consists of a correlation of four fundamental variables. These are: V, vertical permeability variation;' a, mobility ratio; Sw initial water saturation; and R, fractional recovery of oil in place at a given producing water-oil ratio. The correlation extends over a wide range in each of these variables, and may be applied to all formations with initial oil saturations of 45 per cent or greater. The method of calculation originally outlined by Dyhtra and Parsons closely follows their derivation. And this is a convenient way of illustrating the development of some rather complicated ideas. However, in actual use it is more cumbersome than necessary. The purpose of this note, therefore, is to provide a simplified method for making Dykstra-Parsons predictions. A SIMPLIFIED GRAPHICAL SOLUTION The correlation between V, a, Sw and R, corresponding to a given producing water-oil ratio, can be shown on a single graph. This is best done by plotting V against a to show lines of constant R(1 - S, . WOR-0.2). Figs. 1, 2, 3, and 4 show these plots

Jan 1, 1957

By R. W. Raymond

I DESIRE to call the attention of the Institute briefly, and by no means in the way of an exhaustive description, to the interesting developments recently made on the east bank of the Hudson River, in the mining of spathic iron ores. The mines to which I refer are those of the Hudson River Spathic Iron Ore Company, situated at Oakhill on Hudson, Columbia County, N. Y., five or six miles from the city of Hudson, and opposite the town of Catskill. The ore occurs in beds, constituting apparently members of the stratified series of rocks on that side of the river, coursing nearly north and south, parallel with the river, and dipping east. The principal outcrops are presented in a range of low hills, about one mile from the river, along the crest, on the western face of which the stratum of spathic ore is more or less exposed. The length of the line in this range, along which, at various openings the ore has been discovered in profitable quantity, is about two miles. To the northward, the hills are somewhat higher, and the stratification may possibly be disturbed, though the rapid examination of the locality which I made in November last did not, include any determination of this

By Gerald Sherman

In the southern field of the anthracite region of Pennsylvania, many of the coal seams dip at angles of 40" to 50" from the horizontal. For transportation purposes, "tunnels" are driven across the coal measures and, occasionally, "rock gangways," beside the seams and parallel with them. The use of gangways driven in country rock appears to be increasing, as they avoid the maintenance of long gangways in coal, which eventually are driven to the colliery boundaries, and permit mining from a number of intermediate blocks without interference. The rock consists of slates or sandstones of moderate hardness, which may range into very hard, highly siliceous, fine-grained conglomerates. In this distinctly bedded formation, the direction of the heading, whether parallel with or across the structure, makes it necessary to distribute the drill holes in a different pattern to break the ground, but does not change loading conditions. In 1932, practically all the mucking was done by hand, and it was the established custom to use four men on two drills for drilling and breaking the ground, and five for loading it out. A driver and mule was needed in addition, to assemble the rock cars at a siding or branching track in the rear, pending their final disposal. This might occupy the driver's whole time, or if the length of haul were short, he might be able to do other useful work. It was thought possible in 1932 to reduce the cost of driving such headings in rock by mechanical loading, and to investigate this subject a scraper loader was used in a section of tunnel then being driven. Operations while driving 195 ft. of this tunnel using a scraper loader were carefully observed. Time studies were made of the loading, and records made of the routine of breaking ground, but not in such detail. Tunnels or gangways in the colliery are 7 ft. high above the rails, by 10 ft. wide, which requires a minimum of 8 ft. in height, broken to allow for rails and ties. This cross section is of sufficient size to permit the use of any one of several types of power loaders, but for this demonstration it was found most convenient to use a scraper loader.

Jan 1, 1937

By F. W. Bloecher

DETERMINATION of the surface area of finely divided minerals is of interest to mineral engineers engaged in flotation, comminution, and de-watering studies. In the industrial minerals field, many materials are classified as to fineness according to their specific surface (surface area per unit weight). A method of surface area determination has been tested and used in the Richards Mineral Engineering Laboratories at M.I.T. It involves low temperature krypton adsorption measurements using the technique described by Beebe.' During the past fifteen years a number of new surface measurement techniques have been developed. Those that are broadly applicable to materials dealt with by mineral engineers include the permeability method in which a gas or liquid is passed through the sample, and the low temperature gas adsorption methods first described by Brunauer, Emmett, and Teller."" Efforts to make surface determinations from size distribution curves have long been attempted"."." but because of the uncertainty of sub-sieve size distribution and inaccuracies in screen analyses, the method is at best only a rough approximation. The most widely used gas adsorption method utilizes nitrogen gas." Nitrogen adsorption, however, is not particularly suited as a tool for most mineral engineers because the method is not applicable for surface determinations on coarse materials, that is, materials coarser than approximately 150 to 200-mesh. Other gases have been used in mineral engineering studies, particularly ethane."' lo The use of ethane gas, however, involves .a technique that is too sensitive for most mineral engineering work. The permeability method of surface area determination has the disadvantage of not being sensitive enough to detect the surface represented by minute cracks, the so-called internal surface of a particle. The low temperature krypton adsorption method described by Beebe1 utilizes apparatus and techniques that are essentially the same as those used in the ethane adsorption method."1° The surface area is calculated by the B.E.T. method."-' The krypton adsorption technique is particularly suited to the needs of the mineral engineer because: (1) The method can be used for making surface area measurements of rather coarse materials (35 to 48-mesh), as well as extremely fine materials, such as clays or colloidal slimes with specific surface that might be as high as 20 to 30 mb er g. (2) The use of krypton gas offers the advantage of low saturation pressures (2-3 mm) at the conveniently obtained liquid nitrogen temperature. Therefore the krypton vacuum system need not be designed to measure or withstand internal gas, pressures above one atmosphere as is the case with the nitrogen gas method. (3) The krypton technique offers the safety feature of employing liquid nitrogen, as contrasted to the ethane technique in which liquid oxygen is required. Furthermore, ethane vapor pressure at liquid oxygen temperatures is low (about 10 microns), and a high sensitivity McLeod gage is required for pressure readings. (4) The measurement technique with krypton gas is much simpler and faster, and the apparatus is less elaborate than that required with either nitrogen or ethane gases. Apparatus A krypton surface measurement apparatus like that used at M.I.T. is shown in Fig. 1. It is constructed of pyrex glass. A vacuum is maintained by two mercury diffusion pumps in series backed by a mechanical vacuum pump."' The vacuum thermocouple gage is used for checking the vacuum within the system. This type of gage is quite sensitive down to a pressure of 1 micron of mercury," but may be used to indicate pressures much lower than that

Jan 1, 1952

By K. J. Anusavice, R. T. DeHoff, A. G. Guy, T. B. Lindemer

As one oi the approacizes to understanding multicorn-ponent dimsion, an expevinzental sturly is being jnade of tracer diffusion in the copper corner of the CLI-Ni-Zn syste?n, out to 30 at. pct each of nickel and zinc, and in the 150°C range oJ temperature just below tlze solidts te?rlperature. The reslts obtained using the Znm isotope are reported heve, while studies with nickel and copper isotopes are planned for a future paper. The fifteen alloys investigated were melted in sealed wear lubes, sroaged, homogenized, and then analyzed, using the conventional isotope-plating plus lathe- sectiorzing teclzniqlte. The data obtaiued show that the difJusion coeflcient of the zinc isotope increases titlz increase in zinc content, and decreases t'itlz incease in nickel content. The correlation xith solidus temperature is particularly strong. Diffirsiui-ties ranged fro u sq cm per sec nt tlze Iiigh-zinc, low-nickel compositions. The activation energy /or tracer diffusion ravied j.or 31.000 to 54,000 calper mole. It is now generally recognized that diffusion data and theories are needed for multicomponent systems, where extensive practical developments and even some theoretical studies have already been made. For example, much recent work on precipitation from solid solution has been concerned with ternary solid solutions such as A-M-Z' while Zener relaxation has been studied on Au-Ag-Zn alloys,' although adequate diffusion data are available for neither of these systems. Actually, the only ternary systems for which systematic diffusion studies have been begun, in addi- tion to the one reported here, are CO-i-cr3 and Cu-A-Au. Since the theory of multicomponent diffusion is still in the stage of active development5 it is important to distinguish the various kinds of diffusion data that can be determined. An oversimplified approach, widely used prior to 1950, was to determine the influence of a third element, such as nickel, on the diffusion behavior of a binary alloy, such as CU-Z. Later it was recognized7 that four diffusion coefficients can be used to describe ordinary interdiffusion in a ternary system, while as many as six coefficients may be required to include the Kirkendall effect. It is likely that the number of independent coefficients will be shown to be less than four and six, respectively, through the application of the thermodynamics of irreversible processes.5 The simplest type of diffusion in a multicomponent system is tracer diffusion, since each component is characterized by its own tracer-diffusion coefficient in an alloy of a given composition. Thus, in a ternary alloy there are three tracer-diffusion coefficients, each a function of composition and temperature. The present research program is a study of tracer diffusion in the copper corner of the Cu-Ni-Zn system out to 30 at. pct each of Ni and Zn in a 150°C range of temperature just below the solidus temperature. The

Jan 1, 1967

By H. F. Easter

The lead department of the El Paso Smelting Works at El Paso, Tex., is operated strictly on a custom basis. The ores treated are drawn from the surrounding territory, comprising New Mexico, Arizona, western Texas, and northern Mexico. Ores received from the last-named section originally amounted to a very large tonnage, but. of recent years have dwindled into comparative insignificance so far as this plant is concerned. This has been due partly to the establishment of a lead-smelting plant at Chihuahua, which is much closer than El Paso to most of the important mines, and partly to the recent revolutionary troubles in Mexico. There are no mines of either lcad or copper in the immediate vicinity of El Paso. In general, it may be said that the lead-ore supply of recent years has been uncertain and precarious, with a general tendency toward an excess of silica and a shortage of iron. This latter requirement has been met in large part by the use in El Paso lead furnaces of considerable amounts of roasted leady copper matte from the Chihuahua smeltery and of converter slag from the El Paso converters. These two materials, coupled with complex lead-copper ores from Bisbee, Ariz., have introduced into the lead-smelting operations a most unusual amount of copper, which has had an important bearing upon the smelting practice of the plant. his matter will be discussed later. The ore, loaded in either box cars or gondolas, enters the storage yard on four tracks elevated about 8 ft. above the ground. As all unloading is done by hand, unloading platforms at the height of the car floor parallel the tracks on each side to afford a runway for wheelbarrows. At frequent intervals these lengthwise platforms are joined together by others running crosswise to facilitate the distribution of the ores evenly over the beds, which are located below and between the tracks. At present much of the bedding space formerly used for lead ores is given over to the copper department, but 20 bins of various sizes are retained for the use of the lead furnaces and the Huntington & Heberlein roasting plant. The largest of these holds about 1,000 tons, while the smallest holds not over

Jan 1, 1916

By Henry H. Otto

The anthracite industry can be divided into two parts—the underground, or mining, and the outside, or preparation or manufacture. To understand recoveries in the two branches, some of the history of the industry and the changes that have taken place in the past century should be considered. It is a long step from 1807, when 55 tons were produced in the Wyoming field, to 1917, the peak year, when 80,841,223 tons were shipped to market from all the fields. In 1820, the Lehigh Coal Co., the predecessor of the Lehigh Coal & Navigation Co., shipped 365 tons in arks down the canal of the Lehigh Navigation Co. The Schuylkill field was not opened until 1822, when 1480 tons were shipped. The Wyoming field really became a producer in 1829, when 7000 tons were mined and shipped. It is well to note, at this time, the passing of the Coleraine colliery after a life of 88 years; in collieries of this age will be found the romance of the region, as well as the history of the changes to date. Mining Methods In the Lehigh region, the first coal came from the old quarry mines at Summit Hill; a little later the open-cut workings, or quarries, east of Jeansville, and near Beaver Meadow were opened. In the Wyoming field, it was necessary to resort to underground mining almost from the very first. Ashmead1 has described the changes in outside preparation methods, dl tending to increase the percentage of coal shipped to market. A description from the days when the lump coal was raked and screened out in the quarries or mines, to the modern breaker of today, shipping as high as 6000 tons of at least eight sizes of coal in an 8-hr. day is a very interesting story. Each size is a step toward increasing the yield from the property. With the belief that the supply was inexhaustible, the early mining was conducted with the thought of getting the maximum amount of coal on first mining. The superintendent was his own foreman and engineer.

Jan 1, 1925

By H. M. Bannerman

IN the past few years the mineral raw materials problem has risen from comparatively obscurity to great national significance. The transition has come so rapidly that the nature of the problem and what it portends have not yet been clearly defined. Consequently there are wide differences of opinion among the experts as to what can, or should be done to insure a continuing, adequate supply. On one hand, it is said that depletion of known domestic deposits and lagging discovery of new ones will bring about an imminent decline in mineral production and that in future U. S. mineral-using industries will have to depend on foreign sources for more and more of the major mineral raw materials. On the other hand, it is argued that domestic mineral resources are virtually inexhaustible if there were only legislation against competition from low-cost foreign producers. Still another school of thought contends that within the past decade the country has entered a period of unprecedented mineral discovery that is rapidly solving the problem of depletion. Only time will tell which of these widely divergent views is nearer the truth, for mineral resources are, after all, the result of research and adaptation, and resources of the future, as of the past, will depend largely on human response to circumstances. Of 18 substances now termed reactive metals, only 8 (boron, thorium, potassium, sodium, lithium, uranium, molybdenum, and tungsten) were considered of commercial significance at the turn of the century. Except for hafnium and rhenium, the other ten were well known to chemists and mineralogists before this, but none had found use commercially, whereas some, like titanium, were looked upon as nuisances in the ores of other metals. Of these ten elements, several were considered of minor commercial significance, and others were of little more than academic interest as recently as 15 years ago. Before World War II only a few of the better informed spoke of uranium or thorium as possible sources of power. Still fewer talked of converting boron into a super- fuel, and the time had not yet arrived when hafnium, rhenium and even zirconium were thought of as critical to U. S. welfare and safety.

Jan 10, 1957

By W. A. Cole, E. L. Derby, J. F. Wolff

Exploration of Lake Superior iron ores is done principally by drilling. The soft iron ores are churn drilled and the harder ores are diamond drilled. The churn drill used is the Mesabi type and its operation should be described as "water jetting." The drill rods are washed down by the combination action of the water jetting from the bit at the lower end of the rods and the churning motion given the line of rods. The water, which is forced down through the rods, comes up between the wash rods and the casing, bringing the choppings to the surface. It is caught in three or more barrels, each of which has a stoppered hole 8-10 in. from the bottom. These barrels are successively filled, allowed to settle, and drained to the hole, until the desired depth is drilled. The sediment from each barrel is transferred to a settling tub in which it is allowed to settle; the water is then drawn off and the wet sample is collected and dried. The number of barrels used depends on the character of the ore. For example, when drilling sandy ores, all the wash water is caught and settled for the proper length of time without refilling any of the barrels. Thus, the sediment held below the stoppered hole in any one barrel is not disturbed. The casing is kept as near the bottom of the hole as practicable to prevent the caving of the hole from jeopardizing the sample. While the casing is being driven down and the hole is being washed clean after casing, the return water is not run into the sample barrels. In exploratory work in the harder formations, where the diamond drill is used, the sample comprises both core and cuttings. The care given in handling and preserving the core depends on the importance that may be attached to certain characteristic strata in different formations. The following instructions for the care of core samples are issued by the Ogle-bay Norton Co. for diamond drill work done for them on the Gogebic Range of Michigan:

Jan 1, 1925

By H. E. Crum, W. E. Hubbard

This review covers the northern 32 counties of the Texas Panhandle, an area 180 miles square. The westerly three-fourths of the district lies wholly within that great area known as the Llano Estacado or "staked plains." Six of the counties produce oil and gas and three produce gas alone. All of the production is associated with the Amarillo arch, a huge anticline superimposed upon a buried mountain range which is undoubtedly a continuation of the Wichitas of southwestern Oklahoma. Oil Production The production of the Texas Panhandle up to Jan. 1,1930, was slightly over 157 million barrels, 90 per cent. of which came from Hutchinson and Gray counties. About 33,000,000 bbl. was produced during 1930. Though this was about 9 per cent. above the 1929 production, it was over 8,000,000 bbl. less than was produced during the peak year, 1928. The present daily production is slightly over 40,000 bbl., which is the allowable production under state-wide proration. The assumed potential for the purpose of proration is 124,500 bbl. and the actual capacity of the wells probably would be in the neighborhood of 100,000 barrels. The total initial production of the oil wells completed in 1930 was 157,289 bbl. from 308 wells, or 511 bbl. per well, as compared to a 734-bbl. average from the 350 oil wells drilled during the preceding year. The completions in Gray County numbered 232, with an average initial of 614 barrels. Completions During 1930, 526 wells were completed in the Panhandle as compared to a total of 503 during 1929. Of the year's completions, 308 were oil wells, 169 produced gas and 49 were dry holes. Of the 3027 wells drilled in the Panhandle to date, 2780 have produced oil, gas or both, making the ratio of dry holes to producers about 1:11.3. Ignoring the 63 dry holes drilled in nonproductive counties, the ratio becomes 184:2780 or 1:15.1 which is slightly less favorable than that which obtained at the end of 1929.

Jan 1, 1931

By S. D. Brady

In Monongalia County, West Virginia, the Pittsburgh and Sewickley beds lie west of the Monongahela River and underlie practically all the western end of the county. The average thickness of the Pittsburgh bed is 8 ft., where it is being mined at present, sometimes running up to 9 ft. The Sewickley bed is 4½ to 6 ft. thick and lies 90 to 100 ft. above the Pittsburgh bed. As the Pittsburgh bed had a known value, a large part of it was bought up without consideration of the Sewickley bed. When the Monongahela Railway was built up the west side of the Monongahela River, other interests bought up the Sewickley bed, as it was found to be equal in quality to the Pittsburgh, with slight local exceptions. The two beds, therefore, were owned by different people, and naturally each owner opened his mine and ran it without regard to the working of the other bed. Consequently, considerable portions of the upper bed were seriously affected for economical mining, especially on Scotts Run. In recent years there has been a tendency, influenced by the decision of the West Virginia Supreme Court, on the part of the operators in Monongalia County to try to coordinate their projections in the layout of their mines. A typical geologic section, according to the report of the West Virginia State Geological Survey on Monongalia County, agrees with Fig. 1. It is apparent that the rock above the Sewickley bed and between the Sewickley and Pittsburgh beds is of a rather friable ~lature, therefore it is easily broken in pillaring. About the only difference between this section and the geologic section in the Lowsville district is that in the latter district the rock between the coals is a denser sandstone and contains little shale and limestone and no evidence of Redstone coal. It is a laminated sandstone, and although it makes a harder mass, it is easily broken. While working in the Lowsville district, the author had an opportunity to examine a neighboring mine in the Sewickley bed, which was over a section being pillared in the Pittsburgh bed. The two mines belong to dif-

Jan 1, 1931

By T. K. Perkins, L. E. Bartlett

Values of rock surface energy (i. e. energy required to form a unit area of new surface) are useful for interpretation of drilling and fracturing phenonema This paper describes the adaptation of a cleavage technique (splitting of large rocks under controlled conditions) for measuring surface energies. Values of surface energy obtained at room temperature and at low crack extension rates are reported for a variety of sandstones and limestones. Elastic moduli, tensile strengths and compressive strengths of the samples are also reported. The values of Young's moduli (measured in bending) are relatively low, probably because of the low stress levels imposed. Measured values of surface energy me generally higher than anticipated and probably reflect inelastic yielding near the extending tip of the crack. INTRODUCTION The technology of petroleum production includes many operations such as drilling and fracturing, which involve rock breakage. One of the fundamental properties of a rock needed to fully explain breaking and fracturing phenomena is the surface energy (i. e. the energy required to form a unit area of new surface). In this paper we describe an adaptation of the cleavage method (splitting of the rock under controlled conditions) to utilize large rock samples. Application of the theory of elastic cantilever beams and the Griffith concept of mechanical stability permits the calculation of surface energies from simple measurements. Values of surface energies obtained at room temperature on dry samples and at low crack extension rates are reported for a variety of sandstones and limestones. Measured values of Young's Moduli, compressive strengths and tensile strengths are also reported for the rocks. THE EXPERIMENTAL METHOD Equipment designed to cleave large rock samples is shown on Fig. 1. This equipment consists essentially of two steel blocks cemented to a rock sample and forced apart with a steel rod. A ball joint and a pivot prevent bending stresses in the rod. A differential thread arrangement permits the rod to advance only 0.012 in./revolution of the driving nut. The axial force in the rod is measured with type FA-50-12 Baldwin Lima Hamilton strain gauges and a BLH type 20 strain gauge reader. Separation of the blocks is measured with a Starrett 656617 dial gauge. The massive nature and design of the equipment minimize the amount of elastic energy stored in the steel parts as the stress in the rod is increased. This will permit the rock to split under controlled conditions as will become clear later. Fig. 2 shows a sketch of the rock sample during cleavage. Guide slots are cut longitudinally along the rock sample as suggested by Berry.1 An initiating slot is also cut across the top of the block to a depth of 1 to 2 in. During cleavage, elastic energy is stored in the flexed beams of rock of length C. If the length of steel rod L is held constant and the crack extends in length, then the elastic potential energy stored in the rock decreases. However, surface energy must be supplied as the crack extends in length. Griffith6 has proposed the following criteria for mechanical stability. The crack will extend as long as the potential energy available is greater than the surface energy required. However, the crack will stop extending when the change in potential energy with change in crack length is just equal to the change in surface energy with change in crack length. See Eq. 1.

By K. W. Nelson, John N. Abersold

INDUSTRIAL hygiene has been defined by Patty' as "the science and art of recognizing, evaluating, and controlling potentially harmful factors in the industrial environment." This definition implies thorough study of operations, evaluation of potentially harmful factors through air sampling, micro-analyses and other means and finally, appropriate medical and engineering control wherever indicated. The prevention of industrial health injuries is a vital part of operations of American industry today. Progress and interest in this field has increased steadily for many years, the most rapid progress having been attained, perhaps, during the last three decades. It is significant to note that there are now official agencies in 46 states actively concerned with industrial health problems and that a western field station has been established recently in Salt Lake City by the U. S. Public Health Service to augment its industrial hygiene services directed from headquarters of the National Institute of Health, Bethesda, Md. Many of the larger industries have found it advantageous to establish their own industrial hygiene departments. The American Smelting and Refining Co. is a world-wide organization engaged in the mining, smelting, and refining of lead, copper, zinc, silver, gold, by-product metals, including cadmium, arsenic, and others. In the United States there are 13 smelters and refineries, 11 secondary smelters or foundries, and a number of mines. Approximately 9000 workers are normally employed. It has long been the established company policy to seek out occupational hazards and provide safeguards for employee health. Protective equipment has been supplied to individual workers and exhaust ventilation installations have been in use in some operations for more than 40 years. All of the major units have their own medical departments which provide employees with excellent medical and hospital care. In 1937 full scale industrial hygiene studies were undertaken at the Selby Plant and were extended to most of the other smelters during the next three years. In 1945 the Department of Hygiene was organized with Professor Philip Drinker of Harvard University as Director and with Dr. S. S. Pinto as Medical Director. The department is responsible for coordinating and maintaining a program for the good health of all employees from top management down to the lowest paid day worker. It is essentially a service organization serving all of the United States plants regardless of location or size. Full and part-time physicians employed in all of the company's American plants and working in close cooperation with the Medical Director are responsible for de- termining the state of health of all the employees and giving treatment when necessary. In general, medical care is confined to accidents or illnesses occurring while the men are on the job. Among the duties of the doctors is the making of careful physical examinations of new employees and routine check-ups of old employees. In addition to medical care a primary responsibility of the department is the prevention of occupational illnesses. In this the main concern is with the working environment in relation to its effect on the worker. Environmental factors may be dusts, fumes, gases, toxic materials, heat, humidity, radiation, or noise. The objectives are: (1) Immediate control of these factors through the education of the worker, through providing the wearing of respirators or other protective devices, and through careful medical examinations and regular analysis of urine specimens; (2) a long range control program which may be accomplished by local exhaust ventilation, wetting of materials, changes in metallurgy, changes in methods of handling, or by use of special devices and special equipment. To accomplish these objectives a fine industrial hygiene laboratory was built in Salt Lake City and equipped to do routine and experimental work. Trained and experienced industrial hygienists obtain the facts by making frequent hygiene surveys. These surveys include tests of the air, studies of all processes, and careful investigation of ventilation, lighting, and general working conditions. Except in emergencies, the air contaminants and often the substances handled by the worker are sent to the laboratory for analysis by chemists and technicians specially trained in industrial hygiene methods. The findings are evaluated in terms of limits recommended by various State and Federal agencies, and in light of all available medical data. The methods used for studying the working environment involve all of the usual chemical and physical procedures employed in industrial hygiene. The Impinger, electric precipitator, thermal pre-cipitator, and filter paper sampler have been used to collect atmospheric dust and fume samples. Of special interest here is the filter paper sampler, shown in Fig. 1, which was developed by Dr. Silver-man at Harvard University. The instrument has been improved and is used very extensively in field studies. A water manometer connected behind an orifice is used to determine the rate of air flow. Calibration is effected by use of a standard gas meter or rotameter. The dust or fume is collected on a filter paper clamped between two rings, as shown in Fig. 2. The filter paper, such as Whatman No. 52, collects both dust and fume with a very high efficiency. The instrument is very convenient and easily transported. The solids collected on the filter paper are analyzed in the laboratory usually by use of a polar-ographic procedure. By this procedure it is possible to measure quantitatively in a single analysis the

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5. The medal committee may invite nominations from the membership of the Institute, such nominations to be accompanied by an argument in favor of the award and details sufficient for a proper citation to be drawn. This medal has been awarded as follows: 1927—David William Brunton. 1929—John Hays Hammond. 1928—Herbert Hoover. 1930-Daniel C. Jackling. Miscellaneous Prizes Many of the Local Sections have established or administer prizes for the best paper presented within the year by any junior member. Annual Lectures Howe Memorial Lecture The Howe Memorial Lecture, in memory of Henry Marion Howe, Past President of the Institute, was authorized in April, 1923, as an annual address to be delivered by invitation under the auspices of the Institute by an individual of recognized and outstanding attainment in the science and practice of iron and steel metallurgy or metallography, chosen by the Board of Directors upon recommendation of the Iron and Steel Division. The following were the Howe lectures and lecturers for the years indicated: 1924 What is Steel? By Albert Sauveur. 1925 Austenite and Austenitic Steels. By John A. Mathews. 1926 Twenty-Eve Years of Metallography. By William Campbell. 1927 Alloy Steels. By Bradley Stoughton. 1928 Significance of the Simple Steel Analysis. By Harry D. Hibbard. 1929 Studies of Hadfield's Manganese Steel with the High-power Microscope. By John Howe Hall. 1930 The Future of the American Iron and Steel Industry. By Zay Jeffries. Institute of Metals Lecture An annual lectureship was established in 1921 by the Institute of Metals and it has come to be one of the important functions of the Annual Meeting. A number of distinguished men from this country and abroad have served in this lectureship. The roll is quoted below: 1922 Colloid Chemistry and Metallurgy. By Wider D. Bancroft. 1923 Solid Solution. By Walter Rosenhain. 1924 The Trend in the Science of Metals. By Zay Jeffries. 1925 Action of Hot Wall: a Factor of Fundamental Influence on the Rapid Corrosion of Water Tubes and Related to the Segregation in Hot Metals. By Carl Benedicks. 1926 The Relation between Metallurgy and Atomic Structure. By Paul D. Foote. 1927 Growth of Metallic Crystals. By Cecil H. Desch. 1928 Twining in Metals. By C. H. Mathewson. 1929 The Passivity of Metals, and Its Relation to Problems of Corrosion. By Ulick R. Evans. 1930 Hard Metal Carbides and Cemented Tungsten Carbide. By 8. L. Hopt.

Jan 1, 1930