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By C. P. Watson, R. E. Collom

Various chapters already written in the history of development of the North Dome of Kettleman Hills are monotonoysly identical in the one underlying' theme of conservation of oil and gas. Discovered on Oct. 4, 1928, by Milham Exploration Co. with its wildcat Elliot No. 1, the field has been subjected to practically every modern form of production restraint in the name of conservation. The record thus far developed shows that conservation was had for a time, at a price; and that unitiza-tion must be blessed by single ownership or 100 per cent participation to be effective. In fact, incomplete unitization places a heavy handicap upon its participants in the competitive development that follows. Shut-in Agreement of July 25, 1929 Not long after discovery at Kettleman but after the Continental Oil Co. and the Standard Oil Co. had completed several producing wells in the discovery group, came the so-called Shut-in Agreement negotiated at the instance of the Department of the Interior. This agreement became effective July 25, 1929. The fundamental purpose of the agreement was to prevent bringing on production of some 30 wells then being drilled and forestall a flood of Kettleman oil on the market. A cooperative scheme was developed whereby wells in the discovery group would continue to produce. Two of them could not be shut in. Drilling wells would be completed to a water shutoff in top of Temblor and operations suspended. Producing wells would contribute the value of 10 to 25 per cent of their production to the owners of suspended qualifying wells. The percentage rate of drainage contribution was left to a committee or umpire. Some acreage was not placed under the agreement. This same acreage later did not come into the Kettleman Unit Agreement. Several wells on this acreage did not contribute to the drainage fund. The total amount of oil produced during the 17 months of the shut-in agreement, by Milham, Continental and Standard from wells in the discovery group, was 5,297,262.22 bbl. The total amount paid out in "drainage" contributions was $2,046,048.18, representing sales value of 1,266,044.06 bbl. of oil.

Jan 1, 1937

By L. G. Austin, P. T. Luckie, R. R. Klimpel, R. S. C. Rogers

1. INTRODUCTION The Bond method(1.2) for sizing tumbling ball mills has been used successfully for many years. The primary purpose of the Bond calculation is to predict the mill size and mill power to give a desired capacity (Q tph) from a wet overflow ball mill in normal closed circuit operated with a circulation ratio of 2.5. The input to the calculation is the make-up feed size characterized by the 80%-passing size in micrometers (xG), the desired circuit product size characterized by the 80%-passing size (xQ), and an empirical grindability number (the standard Bond Work Index) determined by a standard test. A series of empirical correcting factors(2) are used to convert the results to open-circuit or dry grinding in grate discharge mills. The Bond method has two major engineering advantages: (i) it is very simple; (ii) experience has shown that it works for many circumstances, as a reasonable approximation, because it is based on direct conversion of test data to results measured on industrial mills. There are four main disadvantages of the Bond method. First, there will be a range of error for any specific mill and material and set of operating conditions because the method does not explicitly include several variables which are obviously important: (i) recycle ratio and classifier efficiency (ii) mixture of ball sizes in the mill (iii) variations of residence time distributions with mill geometry and slurry density (iv) lifter design (v) slurry rheology (vi) different underfilling or overfilling of the mill as flow rate is changed. Second, the Bond method explicitly assumes that specific grinding energy E is not a function of ball load, whereas industrial practice and laboratory tests(3) show that the specific grinding energy (to go from a specified feed to a specified product) is less for lower ball loadings than the ball loading for maximum mill capacity. Third, the method uses only the 80% passing size of circuit feed and product to characterize the size distributions, whereas mill capacity in general must depend on the shape of the feed size distribution and the product size distribution. The prime example of this is the use of the reverse closed circuit which removes some fraction of the make-up feed before it is

Jan 1, 1982

By Thomas Fraser, H. F. Yancey

BefoRe a new coal-washing plant is installed, or an existing washery is remodelled and improved, considerable experimental work on the coal to be washed should be done. A thorough examination of a coal, to determine whether it can be washed successfully and the best and most economical process for securing a satisfactory grade of washed coal, calls for mine sampling, analytical work, and experimental coal-washing tests which may require several months' time and the expenditure of considerable money. Having collected the required data on the characteristics of the coal and the results secured with different types of machines under different sets of conditions, it is necessary to decide what method of treatment should be used. The interpretation of the experimental data is no small part of the problem. The first step in the investigative work is to determine from the characteristics of the coal and the manner of occurrence of the impurities whether it is possible to separate the dirt from the coal and produce a washed coal of the required quality. Then it is necessary to select the type of washer or the system of treatment that will produce the greatest amount of washed coal of this grade for the least cost. To secure this information, tests may be made at laboratories operated by consulting or contracting engineers, at the testing plants of machinery manufacturers, at commercial washeries, or in an experimental washery erected on the site of the proposed plant. Such tests will produce figures in which every factor, including analyses of raw coal and washed coal and yield of washed coal, may vary widely. To reduce these results to a common basis for comparison is very difficult. A number of plans

Jan 1, 1923

By William Grady

FACTORS entering into the market value of coal are its grade, and the cost of labor, material, and capital. Reduction in these costs cannot be expected in the future, and it therefore follows that greater economy in their use must be accomplished if it is desired to hold the present markets; more tons of product per unit must be obtained in a given time from both men and material, and means devised for increasing the percentage of lump and domestic sizes. This paper is presented for the purpose of inviting discussion and stimulating thought in regard to the influence of methods of procedure and plans of mining, upon the quality of coal, the economical use of labor, material, and capital, and the cost of production. Even the better methods of the. present day leave much to be desired, and a review of the reasons and necessities for their use may be of value in pointing the way to more economical mining. The writer does not attempt to discuss untried methods of mining, but rather to state clearly and concisely a summary of the results obtained under the several methods of procedure that have been adopted. In some instances a high degree of concentration has been effected, and comparisons of the results obtained with the results of lesser degrees of concentration form an interesting study. It is believed that much may be accomplished in improving the quality, and in the more economical use of labor, material, and capital, by concentration, and it is to concentration in particular that your study is invited. The writer, who .has occasion to visit many mines, most of which ire under different management, has been inclined to the opinion that improvement has been retarded in many ways and that mining has not as yet been entirely freed from the early-day practices which were forced upon it.

Jan 5, 1915

By Thomas Fraser, H. F. Yancey

BefoRe a new coal-washing plant is installed, or an existing washery is remodelled and improved, considerable experimental work on the coal to be washed should be done. A thorough examination of a coal, to determine whether it can be washed successfully and the best and most economical process for securing a satisfactory grade of washed coal, calls for mine sampling, analytical work, and experimental coal-washing tests which may require several months' time and the expenditure of considerable money. Having collected the required data on the characteristics of the coal and the results secured with different types of machines under different sets of conditions, it is necessary to decide what method of treatment should be used. The interpretation of the experimental data is no small part of the problem. The first step in the investigative work is to determine from the characteristics of the coal and the manner of occurrence of the impurities whether it is possible to separate the dirt from the coal and produce a washed coal of the required quality. Then it is necessary to select the type of washer or the system of treatment that will produce the greatest amount of washed coal of this grade for the least cost. To secure this information, tests may be made at laboratories operated by consulting or contracting engineers, at the testing plants of machinery manufacturers, at commercial washeries, or in an experimental washery erected on the site of the proposed plant. Such tests will produce figures in which every factor, including analyses of raw coal and washed coal and yield of washed coal, may vary widely. To reduce these results to a common basis for comparison is very difficult. A number of plans

Jan 1, 1923

By Herbert Clark Hoover, Lou Henry Hoover

THE third book has explained the various and manifold varieties of veins and stringers. This fourth book will deal with mining areas and the method of delimiting them, and will then pass on to the officials who are connected with mining affairs'. Now the miner, if the vein he has uncovered is to his liking, first of all goes to the Bergmeister to request to be granted a right to mine, this official's special function and office being to adjudicate in respect of the mines. And so to the first man who has discovered the vein the Bergmeister awards the head meer, and to others the remaining meers, in the order in which each makes his application. The size of a meer is measured by fathoms, which for miners are reckoned at six feet each. The length, in fact, is that of a man's extended arms and hands measured across his chest ; but different peoples assign to it different lengths,

Jan 1, 1950

By Robert Archer

THE proper material of construction for a given purpose is that material which meets the requirements satisfactorily at the lowest ultimate cost. It is consistent with this principle that most aluminum castings are made of an alloy containing about 8 per cent. copper. This alloy possesses mechanical properties satisfactory for general engineering purposes together with manufacturing characteristics leading to the production of finished castings at low cost. It is to the aluminum industry what gray iron is to the iron and steel industry. Just as some services require "semi-steel," malleable castings or steel castings instead of gray iron, there is a certain and growing demand for aluminum castings of superior strength or ductility, or both. Since the beginning of the industry producers and others have sought to develop alloys or processes by which such castings could be made. Out of these efforts have emerged many alloy compositions and special processes, of which only a few have had sufficient merit to survive. It is the purpose of this paper to describe those which seem to the authors to offer the greatest promise for the production on a commercial scale of aluminum castings of superior mechanical properties, with special reference to heat-treated castings. The suitability of an alloy or process for actual manufacture is affected by so many factors that the problem of appraisal is not a simple one. Since this is such an important part of the whole subject it is proposed to discuss briefly some of the requirements. The final verdict is of course the result of commercial trial and experience. It will therefore, perhaps, be profitable to employ a somewhat historical method of treatment in discussing the subject of alloy development.

Jan 9, 1926

By F. R. Archibald, C. F. Jackson

THE prospect of winning aluminum from clay was recorded almost a century ago at a time when the metal was no more than a curiosity.? As the industry developed, and it has probably developed faster than that of any other metal, the expanding need for raw materials was adequately met by the ample supplies of bauxite ore. As with the other metals older in industry, however, lower grade ores have gradually entered the raw-material field through improvements in ore dressing, insufficienoy of high-grade ore supplies, favorable geographic location, or national necessity for domestic supply. So with aluminum, or alumina, which has been established as the requisite intermediate, the time may have come when a satisfactory process, with favorable location and suitable raw materials, can hold a sound place both in metallurgy and economics. It is the purpose of this paper to describe the Ancor process and its proposed application in treatment of clay in a plant now under construction at Harleyville, South Carolina, by the Defense Plant Corporation. DEVELOPMENT OF THE ANCOR PROCESS The Ancor process has developed through successive stages of laboratory investigation, pilot-plant demonstration using nepheline syenite and pilot-plant demonstration using kaolin-type day from South Carolina, and is now in preparation for unit trial on an operating plant basis using the latter material. The laboratory studies were carried out over a number of years in the laboratory of the American Nepheline Corporation in Rochester, N. Y., and for the same company in the ore-dressing laboratory of Beattie Gold Mines, Que. Ltd. at Duparquet, Quebec. Both companies are associated with Ventures Ltd., Toronto, and its associated American companies. The work was originally undertaken with a view to recovery of alumina and alkalies from nepheline syenite as an adjunct to the American Nepheline Company's established business in the glass and ceramic trades, but as a process developed the possibility of application to clay and other aluminous raw materials become apparent and the laboratory studies were broadened to include these as well. Under the more pressing impetus of wartime needs and possibilities, pilot-plant operations were undertaken at the Canadian Bureau of Mines Ore Dressing Laboratories in Ottawa, and for purposes of demonstration under joint sponsorship of the Canadian Bureau of Mines, The American Nepheline Corporation, and The Aluminum Company of Canada Ltd.

Jan 1, 1944

By Joseph Perry

MAGNESITE is found in 22 California counties, but many of the deposits are too small or too impure to be of commercial value. Several of sub-stantial size and quality were entirely exhausted by wartime operation. At present, three properties comprise the only known workable deposits in the state. Of these, the Western mine and the Patterson mine have been known and worked for many years, and have been described in con-siderable detail in various publications, therefore need only brief mention here, because of their proximity to the Bald Eagle mine. The latter, recently developed, is unusual in type of ore deposit, plant design and operation, as well as products made, and very little has been written concerning it. WESTERN MINE The Western mine, 32 miles south of Livermore, Calif., was formerly operated by C. S. Maltby. It has been a consistent producer for many years.1 The ore is of amorphous variety, occurring along fracture zones in serpentine. The veins vary greatly in width, the average being perhaps 8 ft., with the maximum indicated in one early stope of 40 ft.; 2 ft. is considered the minimum for economical mining. The strike of the veins is predominantly north and south, with dip to the west varying from 40° to 75°. Walls are well defined and as a rule firm and easily supported, Veins range in length from a few hundred feet to 1000 or more. Their maximum vertical extent is about 350 ft., but many run less. Early mining consisted of open-cut and glory-hole work on the larger outcrops. This was followed underground by a modified shrinkage system, the waste and low-grade horses being removed by hand sorting on the tramming levels and transported to surface dumps. Filled-stope mining is used now, in order to eliminate the handling of waste, which has

Jan 1, 1938

By Arnlf Muan, Bert Phillips

The quenching technique has been used for- a study of phase velntiorzs within the composition triangle 2CaO.Fe2O3-FeO.Fe2O3 Fe2O3 of the system Ca-Fe-O. Desired total compositions of sanzples were attained by weighing of starting materials in required proportions and keeping them in sealed 80 pct Pt 20 pct Rh tubes during equilibration .runs. The liquidus surface has been delineated. the existence of two ternary compounds has been established, and seven ternary inwariant situations have been determined. ONE unit within the research program on refractory oxides in progress in our laboratories is the study of phase relations in the system Ca-Fe-Si-O. The present paper deals with the ternary system 2CaOFe2O3-FeO.Fe2O3-Fe2O3, which is only a small part of the enormously complex quaternary system. Many of the phases occurring in iron ore sinter products have compositions which can be closely approximated within this ternary system, and a knowledge of stability relations existing among these phases may be expected to be a useful guide for improving sintering operations. Two fundamentally different experimental approach es are commonly used in studies of systems containing iron oxides, both permitting control of the oxidation state of Fe. One method consists in keeping constant the oxygen partial pressure of the gas phase in equilibrium with condensed phases (liquid and crystalline). In the other method, which is the one used in the present investigation, the total composition of condensed phases is kept essentially constant by keeping the samples in a gas-tight container. The details of this experimental procedure will be described in a later section. PREVIOUS WORK Extensive studies of phase relations in the bounding binary system FeOFe2O3-Fe2O3 have been reported by Greig, Posnjak, Merwin, and Sosman,' by Darken and Gurry,2, 3 and recently by Phillips and Muan.4 A diagram summarizing the results of these studies is shown in Fig. 1. Particular attention is

Jan 1, 1961

By O. W. Bilharz

INTRODUCTION ACID mine-water drainage is a serious problem with many mines in the Tri-State zinc and lead mining district. Particularly is this true when large volumes must be considered in unwatering old mines that have refilled with water which has dissolved the products of oxidation and has become chalybeate in character. The experiences discussed in this paper have to do specifically with the unwatering of a comparatively small area west of the town of Baxter Springs, Kans., where the pumping job was complicated by water of this type and where the extremely high sulphate content particularly effected that phase of mine drainage having to do with stream pollution. LOCATION, GEOLOGY AND HISTORY The Baxter Springs area of the Tri-State mining field is situated just west of the town of Baxter Springs and is a northeasterly extension of the main mineralized zones of the Oklahoma part of the district (Fig I). The mining area is traversed with well defined shear zones which provide easy circulation of ground waters and the ore bodies are found along these shear zones as localized enrichments wherever the structural conditions are favorable (Fig 2). The ore-bearing strata is Mississippian with an overlain capping of shale of Pennsylvanian age. This shale strata carries much pyrite and marcasite at its base and undoubtedly was a contributing factor to the subsequent high iron content of the water. The area originally contained a sulphide water which discharged as an artesian flow in springs within the town and gave Baxter Springs its name. These springs were famed for many years for their mineral water. This original sulphide water was first removed about 1917 and active mining was carried on west of the town during subsequent high metal price periods. Many small mines were opened, with each localized enrichment becoming a separate mine. During the depression mining ceased and all mines in the west Baxter area were allowed to flood. No serious effort was made to again unwater until higher prices caused from the demand for metal for World War II once more focused attention on this part of the field. ORIGINAL MINING RESULTS IN OXIDATION As plans for unwatering progressed, it soon developed that the mine-water pools had become strongly acid in character and carried large amounts of sulphates in solution. This occurred in the following way. When the original sulphide water was removed, shafts sunk, and mining carried on over a number of years, ferrous sulphate was formed by the spontaneous oxidation of the pyrite beds in contact with air admitted through churn-drill holes and mine openings. These products of oxidation can be seen today in the old mines of the district as crusts of crystalline sulphates

Jan 1, 1947

By C. S. Matthews, H. C. Lefkovits

The purposes of this study are (a) to determine the accuracy of a previously proposed method for calclrlating average reservoir pressure and (b) to find a method for estimating the shape of the drainage area of each well in a bounded reservoir. Both numerical and experimental methods are used to determine the pressure distribution and the location of drainage bounrlaries in idealized reservoirs at steady state. A number of photographs are included which show flowlines and drainage areas in reservoir models of various shapes. Results from these studies are then compared with those from the previously proposed method for calculating average reservoir pressure.' It is concluded that the previously proposed method is sufficiently accurate for most reservoir engineering purposes. In addition, some simple methods are given for estimation of .shapes of drainage boundaries. INTRODUCTION A method for the determination of the average Pressure in a bounded reservoir was previously developed by Matthews, Brons, and Hazebroek,1 and presented at the Petroleum Branch Fall Meeting in 1953.† In aP- plying this method, the reservoir was first divided into drainage volumes; second, the average pressure in each drainage volume was calculated; and third, these drainage volume pressures were averaged volumetrically to give the average pressure in the reservoir. It was shown that each well's individual drainage volume, at steady state, is proportional to the well's production rate; however. the question of how to estimate accurately the shape of these drainage volumes could not be answered. Furthermore, in calculating the average pressure for each drainage area, the actual drainage areas, which are in general quite asymmetric in shape, are replaced with one of the symmetric prototypes given in T.P. 3876. A question may then be raised as to how accurately the symmetrical figures depict the pressure behavior of the actual unsymmetrical drainage areas. The study reported on in the present paper was made in an attempt to shed light on the above questions. METHODS It was shown in T.P. 3876 that after a period of steady rate of withdrawal the rate of pressure decline becomes constant at every point in a bounded reservoir containing a single-phase fluid whose compressibility is small and constant and whose viscosity is con-

Jan 1, 1956

By Harry L. McNeill

THE Selective Media Process was developed by the author in a laboratory provided by The Steårns-Roger Manufacturing Co. It is the outcome of an [ ] investigation into the possibilities of coarse beneficiation by sink and float without using the conventional heavy media. Commercial work to date has been limited to the treatment of minus 3/8-in. iron ore at the Hill Trumbull washing plant of the Cleveland Cliffs Iron Co., at Calumet, Minnesota. Two cut away prints of the machine are shown (Figs. I and 2). A rotary conical impeller is mounted within a stationary cone (Fig. 2). This impeller is adjustable vertically by a 12-ton screw jack. The speed of the impeller can be varied from 14 to 32 r.p.m. by the Reeves variable-speed motor pulley mounted on the 7 ½ -hp. motor drive. Attached to the bottom of the stationary cone is the automatic control valve for sink product, actuated by a ¼ -hp. gear motor. The sink product is dewatered in a conventional drag driven by a 7 ½ -hp. motor and discharged onto an inclined conveyor containing from 6 to 10 per cent moisture. Two plants are operated at the Hill Trumbull property. All the ore is first treated in a typical washing plant (Fig. 3). When treating "wash ore" a finished concentrate can be produced by the log washers and Akins classifiers, as the separation involves only fine silica (minus 48-mesh) and free iron. However, when "jig ore" is fed to the washing plant the coarse

Jan 1, 1946

By E. O. Bennett

When oil is takcn from a subsurface structure it is generally accompanied by gas. The gas thus produced represents the 1ighter hydrocarbons present in the original petroleurn accurnulation, which arc, insoluble at the reduced pressures created around a well when it is producing. In some cases the gas accompanying the oil may come from a gas-bearing stratum not in immediate contact with the oil. The amount of gas from the formation accompanying each barrel of oil is called the natural gas factor. Energy Causing Well to Flow The force causing the flow of fluid into a well when it is drilled into an oil-bearing structure is the pressure differential between the well bore and the formation. A pressure differential between the formation and the well may be set up in three different ways, as follows: (1) pressure due to gas in solution or in contact with the oil, (2) hydrostatic pressure due to water in contact with the oil (it may be either bottom or edge water); (3) pressure difference due to forcc of gravity. The greatest source of energy for producing oil from most oil fields, and the one over which the greatest control can be exerted, is the poten-tial energy in the gas under pressure in the formation. In any pool there is but a definite amount of gas available. Part of this gas may be in solution and a part in contact with oil. The amount of gas in solution in each bard of oil depends on the pressure and temperature in the formation and the characteristics of the oil. Whether the gas is in solution or in contact with the oil it is necessary to use the energy it, contains as efficiently as possible in order to obtain the greatest ultimate recovery from the pool. Bush1 states: Gas being the most efficient aid in moving the oil, it is important to prevent more of it from escaping than is necessary to remove the maximum amount of oil from the sands. The conservation of this energy is far more important to the producer of oil than his returns from sales of gas to distributing companies. The flowing life of the well is the most profitable period, and keeping the gas-oil ratio low, or keeping the

Jan 1, 1928

By A. N. Diehl

IT is the object of this paper (1) to deal with the elements in blast-furnace gas from the standpoint of their importance, and the part they are to play in future consumption, and (2) to give detailed information about the construction and operation of a plant designed among the first in this country for washing gas on a large scale.

Jan 5, 1914

By Finn Ouchterlony

A simple bilinear R-curve description of crack extension resistance is applied to the testing of sub-size rock core specimens. The K-curve consists of a linear sub-critical part and a flat post-critical part. Formulas for the apparent energy rate resistance quantities Gm, Jm, and [R] are developed. Experiments on notched cores of Ekeberg marble, Bohus granite, and Stripa granite are compared with these predictions. The R-curve model gives reasonable results for Gm -data but fails essentially to describe the Jm and [R]-data. Another model with a sharply increasing linear post-critical part could possibly account for the [R]-data, but direct R-curve measurements seem a better approach.

Jan 1, 1982

By John W. Stevenson

At Jim Walter Resources Alabama coal property, the first of twelve projected longwall mining systems started to operate In March, 1979, at the No. 3 Mine. The second longwall started to mine adjacent to the original workings in June, 1980. At the end of 1980, 2 ½ panels had been extracted using the same basic ventilation plan. A single split of air ventilates each longwall panel with intake air traveling the headgate across the face to the tailgate where it is directed and controlled to a 1500 foot deep fan shaft specifically located to exhaust from the longwall area and the gobs associated with longwall extraction. The simplicity of the system makes it easy to understand, apply and control In a relatively gassy coal bed.

Jan 1, 1981

By Damon H. McFadden

5.1-1. Geographic and Geologic Factors. Surface mines are located where the coal seam can be economically uncovered and where the product can be utilized competitively with other fuels. The planning and designing of a pit may follow various procedures. The sequence for consideration of the influential factors as considered here may not be complete for every pit, nor will it be necessary to be completely used in each design. It is suggested as a check and outline for the engineering approach. Controlling conditions for the layout should be listed and considered with the facilities and equipment for the exploitation. After these items, as listed below, have been discussed and the feasibility agreed upon, then the actual planning and design of the pit can be done. GEOGRAPHIC FEATURES. The location of the coal area sets the climatic stage. The rainfall, the temperature extremes, and the general weather conditions all affect the design of the pit. Overburden soil when wet may not be stackable and may be impossible to move by standard procedures. The coal seam itself may be so soft that it must not be traveled on when wet, as the losses may be the difference between a profitable venture and an unsuccessful one. Some equipment will work well on dry soil only, just as a dredge works only in the wet. The conditions must be checked and analyzed. Some equipment cannot handle frozen soil (wheel excavators), so temperature extremes must be noted. The extreme weather conditions may also govern the expected working days and therefore the ultimate production. The altitude (atmospheric pressure) may affect the equipment, and this should be checked. All of these conditions should be noted on the preliminary map of the area. GEOLOGIC FACTORS. The geologic and surface conditions of the coal field dictate the type of pit generally feasible. Rough terrain, rolling terrain,

Jan 1, 1968

By L. E. Young

THE purpose of this paper is to start a discussion on: (1) methods of supporting the immediate roof, particularly of local areas of poor roof, during the mechanical loading of coal; (2) methods of increasing the rapidity of the movement of the mining faces so that, without the use of cribs, jacks, pack walls, and filling, there will be no danger to men, equipment,, and working places from the subsidence of the overlying strata. In the Pittsburgh district the application of mechanical loading devices in mines working in the Pittsburgh seam, has been retarded by the difficulties of holding and handling the draw slate. Normally the thickness of this slate averages about 8 in. but the hardness varies, and a cut of coal cannot always be loaded without placing posts or crossbars to support the slate. Locally, the slate may be thicker and special methods of support may be required. If crossbars are placed to hold the slate when the coal averages 5 ft. in thickness, the standard methods of transporting the coal cannot be followed, and the use of conveyors may be desirable. Very little information is available on the effect of increasing the rate of movement of advancing or retreating break lines or longwall faces. A few British publications have presented some data but all such data relate to longwall faces that have moved not more than 6 ft. a day. The most rapid rate of movement of longwall faces in Germany is 6 ft. per day. In the ordinary hand-loading mine in western Pennsylvania break lines on full retreat will move about 2 ft. per day. If loading machines are used under similar conditions the, rate of retreat may reach 4 ft. per day. In a mine where coal is loaded by hand on conveyors three shifts per day, the rate of retreat has ranged from 11 to 16 ft. per day, with an average of 13 ft. If mobile loading machines could be used to load on con-veyors on break lines, the rate of retreat should be increased substantially.

Jan 1, 1938

By John F. Blandy

With the Report of Mining Statistics, for the year 1872, there was published a geological map of the United States and Territories. This is, I believe, the only map which represents the geology of Arizona, and is, as far as my observations go, correct. It is, however, on so small a scale as to be of little practical value to the miner. I know of no other maps, even of localities, of this Territory. The topographical maps are also on so small a scale as not even to serve as guides from place to place; the largest, that of Eckhoff and Ricker, being only 30 by 30 inches to represent a territory of 135,000 square miles. For these reasons, it makes it exceedingly difficult to describe the various mining centres in an intelligent manner, and equally so to examine such a hilly country as it is intended to describe in this paper. When I first came into this Territory I soon realized the troubles I had to encounter in trying to form an opinion, or even to get the needed information on the geological contour. I have, therefore, labored as best I could to get a topographical diagram of the section of country represented by the map which accompanies this paper.* The lines run by the Land Department up the valleys of the Aqua Frio, and those west of the Hassayampa, and connected east and west to the north of Prescott, enabled me to inclose correctly the space covered by the Bradshaw and Sierra Prieta mountain groups, but the territory covered by these mountains, and the most difficult part, I have had to fill up as best I could. I have met with such success as to meet the approbation of those most familiar with the country, and, with the map in hand, any one would he able to cross it in any direction. As there has not been a single line of survey made across it, this has been no small undertaking, and I have had to depend upon sights from prominent points with the pocket-compass, or, in the absence of that, to make observations, with watch in hand, and guess as near as possible the meridian direction. Rut one main wagon-road passes through the district, that from Prescott to the Peck mine.

Jan 1, 1883