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By E. C. Dominguez, H. B. Scharf

The Sparrows Point plant of Bethlehem Steel Co., southeast of Baltimore, is the largest Bethlehem plant, with an annual rated capacity of 6.2 million ingot tons. There is considerable diversity of product, but a high percentage is sheet, tin plate, galvanized sheets, and rod and wire. The large amount of light-weight end product requires a number of pickling installations that necessarily consume large quantities of sulfuric acid. In the coking operations sulfuric acid is also consumed in recovery of ammonia as ammonium sulfate and in treatment of recovered light oil derivatives. Total sulfuric acid consumption in the plant is currently approaching 10,000 tons per month, of which 55 to 60 pct is required for pickling. In 1951 the acute sulfur shortage caused grave concern as to future sulfuric acid supply for the Sparrows Point plant. Raw materials for acid making were already at hand in the form of hydrogen sulfide and pyrites sufficient to produce nearly half the sulfuric acid required at that time. It was also known that the Bethlehem mining activities would produce additional pyrites in the future. Late in 1951 Bethlehem management decided to build a 250-ton sulfuric acid plant at Sparrows Point to utilize these raw materials. The plant was built and put in operation in May 1953. The steel plant has expanded considerably since 1951, and it is now necessary to operate the acid plant far over rated capacity in order to supply plant demand. Production of acid in 1954 amounted to 93,000 tons.

May 1, 1956

By H. A. Wheeler

THAT lead and zinc deposits are the result of prolonged, slow deposition is the idea of most students of ore deposits, -and in many cases, where the ore-bearing solutions have been very weak or the precipitating conditions have been very feeble, the ore accumulations have undoubtedly taken a long period of time. As these two vital, conditions have been subject to great variations in the different mining camps, the following example is highly interesting in showing that deposition can be very rapid under favorable conditions, geologically speaking, and also extremely recent. In fact, the writer is inclined to regard most, if not all, of the Mississippi Valley deposits of lead and zinc as probably being very young, at least not older than Tertiary, if not Quarternary, in age. The extensive Joplin lead and zinc district, in southwestern Missouri, which is about 60 years old and has numerous mines that were abandoned from 1 to 50 years ago, shows that the lead and zinc today are in an active condition of solution and redeposition, although these two metals occur in the predominant form of sulfides. The mine waters from the older and more or less abandoned portions of the district are frequently so acid, mainly from the oxidation of associated pyrite, as to necessitate the use of wooden pipes and pumps. The first boom in the Oklahoma zinc fields, which is the southwestern extension of the Joplin district, occurred when ore was accidentally struck in drilling a water well. Among the mines then opened up was the Mission mine, at Lincolnville, Ottawa County, Okla. This mine was opened' in 1903 in lean "sheet ground," or a flat blanket formation of chert carrying disseminated zinc blende, or "jack," and galena. The ore-body was very free from iron pyrites and the concentrates were very high grade, the "mineral," or lead concentrates, assayed 80 to 85 per cent. lead and the jack, or sphalerite, assayed 60 to 65 per cent. zinc. The orebody was very shallow, occurring at a depth of 75 to 95 ft. (22 to- 28, in.) and very wet, requiring three or four pumps to handle the water. The

Jan 2, 1920

By Wilbur Nelson

IN 1839,1 Gerard, Troost, the first, State Geologist of Tennessee, reported the occurrence of zinc ores in East Tennessee, in connection with the iron ores at Embreeville; in 1844,2 he refers to the zinc deposits of East Tennessee, especially the apparently rich deposits occurring, in Jefferson and Claiborne Counties, while his ninth annual report is a ,description of the zinc deposits of Jefferson County and a description of the most improved processes by which zinc is extracted from its ores. Although. Tennessee has long known of the occurrence of its zinc deposits and has recognized their value, only during the last few years have these ores been successfully worked. As far as can be learned, prior to the systematic development of the Mascot district in 1911, no large-scale or successful operation of any of the zinc deposits was carried on. But in that year, after several companies had made considerable progress in developing the Mascot area and had proved. a relatively extensive body of low-grade sulfide ore, the American Zinc Co. entered the field. It introduced modern methods of prospecting and mining the ore and from the first was successful. Too great credit cannot be given this company for its pioneer work in a previously unimportant field. Throughout the history of its operations, the American Zinc Co. has confined its efforts to underground mining of the sulfide ore, sphalerite. This company has found that successful results in zinc mining in East Tennessee can be achieved only by expending large sums in prospecting and blocking out bodies of pay ore in sufficient magnitude for large-scale operations. At Mascot are located the mines of the American Zinc Co. of Tennessee, the mines being situated along the Southern Railway in the Holston River Valley, Knox County, about 13 miles northeast of Knoxville. Considerable mining and prospecting had been done by several companies prior to the acquisition of this property by the, American Zinc Co. Previous to 1900 only open pits, which were worked for oxidized ores, were operated. and the production was small. In 1900 the

Jan 10, 1924

By K. J. Richards, W. J. Schlitt

A combination of industrial and laboratory data is used to explain the interrelationships between operating parameters and cementation plant performance as measured by copper recovery and iron consumption. The chemical factors considered are the relative concentrations of copper and ferric ions in solution, acid concentration, the possible buffering action of other dissolved salts and solution temperature. The effects of flow conditions, solution oxidation, the presence of metallic copper and retention time are also considered. Based on the various relationships developed, possibilities for plant optimization are discussed.

Jan 1, 1974

By Ray W. Amstutz

The shaft was drilled on US government land m the Piceance Creek basin and was funded by the US Bureau of Mines (USBM). It was drilled to 723 m to provide access to rich deposits of oil shale, nahcolite, and dawsonite for geotechnical test work and environmental mining research. Rotary drilling and dual-string, reverse-air, jet-assist circulation methods were used. Drilling required eight months. Site preparation, running, and cementing the casing required another four months. A 2.44-m ID steel welded casing, 508 mm thick was installed and 2.7 kt of cement were slurried and pumped into the annulus.

Jan 1, 1982

(Under this heading will he published notes sent too the Secretary of the Institute by members or other persons introduced by members.) Management or superintendency desired by member, graduate mining engineer of large practical experience in the details of mining, milling, concentration and cyaniding. Experienced in the efficient mechanical equipment and operation, and in the general business management of a mining property. No. 444. Metallurgist and operator who has specialized in the hydrometallurgy of. gold and silver, particularly stamp milling and cyaniding, desires change from present position. Ten years' experience in Western U. S. Thirty-six years old, married, in best of health and will go. anywhere. Available in 30 days. No. 445.

Jan 4, 1918

By Earle E. Schumacher

THE elements silicon and germanium are not metals within the usual, intuitive association of the word, nor are they so within a stricter definition based on the electronic binding. Two properties associated with metals are plasticity and high electrical conductivity. These elements crystallize in the diamond cubic structure, an arrangement apparently not very favorable to slip, and are therefore brittle rather than ductile. Their electrical conductivity is not like that of metals the atoms are locked together by the covalent bond, which in pure and perfectly arranged material leaves but few electrons free to act as electrical carriers.† In further contrast to metals, their electrical conductivity can be greatly increased by raising the temperature. Yet silicon and germanium are not ideally nonmetallic. They are hard, solid, and possess a metallic luster. They exhibit that peculiar brand of electrical conductivity conveniently termed "semi- conduction," wherein, as shall be seen, lies much of their importance. Both, but silicon in particular, are important components in real metallic alloys and the methods of their reduction and preparation lie clearly in the province of the metallurgist. From their duality of physical and chemical properties, silicon and germanium, along with such elements as boron, diamond, gray tin, selenium, antimony, and arsenic, are considered semimetals or metalloids. Because of their importance to metallurgy and the im-

Jan 1, 1953

By Theodore Nagel

Fuel-oil, natural gas and coke oven gas, producing the higher temperatures of open-hearth current practice, have been gradually displacing producer gas the lowest cost fuel for open hearth operations. The lower temperatures of combusts on products from producer gas is caused by nitrogen dilution. Practical Application of Combustion Thermochemistry One pound of carbon burned to CO produces 3,960 B.T.U. and one pound of carbon burned to C02 produces 14,140 B.T.U. The second unit of oxygen uniting with gasified carbon (CO) produces (14,140 - 3,960) 10,180 B.T.U. which is (10,180 - 3,960) 6,220 B.T.U. more heat than produced by the first unit of oxygen forming CO by uniting with solid carbon. A review of the relative combustion heating values of commercial gaseous fuels reveals CO requires a minimum of air for combustion and because of minimum nitrogen dilution and the high thermal release from CO higher temperature combustion products are produced from CO than from natural gas or from coke-oven gas under similar combustion conditions. Inert nitrogen diluent lowers the calorific value of fuel gas and its diluting effect is cumulative in lowering the temperature of the products of total combustion. It is not only logical but practical in partial combustion, converting bituminous coal to gas, to generate the gas with reduced nitrogen dilution.

Jan 1, 1936

By Z. Moser, W. Ptak

The experiments were carried out by the method of measuring the electromotive force of concentration cells having zinc as a reference electrode, the second electrode being the liquid alloy Zn-Sn-Cd-Pb. The electrolyte consisted of liquid chlorides and had zinc ions. The measurements were made for seventy -five alloys of different mole fractions within the temperature range of 714° to 877°K. The experimental results enabled the calculation of the activity of zinc in tested solutions. The activities of zinc were calculated by means of Krupkowski's formulas.3 In addition, the formulas for coefficients of activity of zinc, tin, cadmium. and lead as the function of composition and temperature were given. Activity of zinc was compared with the values obtained from experimental results, and good agreement has been observed. On this basis it can be stated that the theoretical formulas are suitable for determining the thermodynamic properties of liquid quaternary metal solutions. IN the metallurgical processes being carried out at present multicomponent liquid metal solutions take part. For the thermodynamic analysis of these processes it is necessary to know the thermodynamic properties of these solutions. Therefore, many experimental and theoretical papers deal with this problem. The theoretical papers are generally based on the assumption that the structure of liquid metals is similar to their structure in the solid state. In this manner the model of liquid solution, consequently described by means of statistical thermodynamics, has been accepted. This method is being lately developed, especially for solid solutions. Statistical thermodynamics was applied among others by Guggenheim 1 for describing the thermodynamic properties. Unfortunately, the formulas of statistical thermodynamics are often not suitable for the interpretation of experimental results. Attention should be drawn to the relations obtained by means of formulas of phenomenological thermodynamics which always have constants derived with the aid of experimental methods. In the case of the multi-component solutions which contain some additions of impurities besides the basic metal, wagner2 introduced interaction parameters. Equations for the relationship between the activity coefficients and composition were also given by Krupkowski." he application of these formulas requires a good knowledge of the thermodynamic properties of the corresponding binary systems. In these formulas, as in Wagner's, there appear constants which should be determined from ex- perimental data. Nowadays, different experimental methods are applied for evaluating the thermodynamic functions of solutions, for instance: vapor pressure measurements, calorimetric methods, and the measurements of electromotive force of concentration cells. In the present paper this last method for evaluating the thermodynamic properties of four-component systems, Zn-Sn-Cd-Pb, was applied. For instance in the case of Zn-Sn solutions Alabyshev and Landratov, 4 Fiorani and Valenti, 5 and ptak6 performed the investigations. The Zn-Pb system was worked out by Kleppa 7 and Cd-Pb and Cd-Sn by Elliot and chipman.' This method was also applied for determining the activity of zinc in ternary solutions. 1) EXPERIMENTAL METHOD The experimental arrangement with detailed description is given in Fig. 1. It consists of resistance furnaces, one serving for melting samples and the other containing the flat-bottomed, measuring quartz tube with the liquid electrolyte. Liquid metals and alloys are in glass supremax tubes, which have an opening in their lower part above the metal level. This opening allows the filling of the tubes by the electrolyte. In these tubes tungsten wires are placed which by means of suitable conductors are connected with a potentiometer. It is assumed that tungsten dissolves Fig. 1—Schematic diagram of the experimental arrangement for the investigation of the thermodynamic properties of liquid metal solutions: 1, resistance furnaces; 2, autotransfor-mers; 3, galvanometers; 4, regulator of temperature; 5, gas purifier with concentrated H2SOP; 6, U-tube with P2O5; 7, thermostats; 8, steel block for thermostating; 9, supremax tubes for alloys; 10, tungsten electrodes; 11, inlet and outlet of argon; 12, measuring quartz tube; 13, tube for melting samples; 14, tube for thermocouple; 15, cover of quartz tube; 16, rubber seal; 17, bottom cover; 18, outlet of electrodes to potentiometer; 19, outlet of thermocouples to potentiometer; 20, upper view of the quartz tube cover; 21, orifices for cover screws; 22, orifice for argon inlet; 23, orifice for thermocouple; 24, orifices for tubes containing liquid metals; 25, inlet for water-cooling system.

Jan 1, 1969

By Charles J. Deegan

The purpose of this paper is to point out some features of the position of fuel oil and it's relationship to the economic balance and price structure of the petroleum industry. The term "fuel oil" as used in this paper includes crude used as fuel as well as refined gas oil and fuel oil. The period covered, from 1922 to date, may be characterized as the new normal era after the post-war inflation and deflation. In order to establish a proper perspective, the figures on consumption of the principal products of petroleum are shown in Table 1. This table shows that fuel oil and gasoline made up the bulk of the total demand in 1928 just as they did in 1922. There has been so much comment about the enormous increase in gasoline consumption that it may come as a surprise to some people to find that fuel oil is still at the head of the consumption list, in point of volume at least, and seems likely to hold that place for at least another year. Having established the fact that gasoline and fuel oil are by far the most important products, the remainder of this paper will deal almost entirely with these two items.

Jan 1, 1929

By Charles H. Jacoby

In 1774 a Swedish chemist, C. W. Schule, first recognized manganese as an element. That same year Schule's associate, J. G. Gahn, isolated the element manganese for the first time. In 1856 the Bessemer process of steelmaking gave birth to the economic importance of manganese. Later, in 1882, Robert Hadfield discovered high manganese steels. Although the primary use of manganese is in the ferroalloy industry, two additional important uses for manganese are making chemicals and dry cell batteries. Manganese is also vital to plant and animal life. Various chemical compounds of manganese are used in fertilizers, feeds, glass manufacture, paints, varnishes, and for numerous medicinal and chemical purposes. For the study of industrial minerals and rocks, only the chemical and battery grade material is of- concern, but for the sake of comparison, metallurgical aspects are included in this presentation. Although currently the world's largest consumer of manganese, the United States is producing only minor amounts of ore at the present time. This is due primarily to the fact that although huge deposits of manganese occur within our borders, all are of such low grade as to be economically unfeasible to mine. For many years various government agencies and segments of private industry have devoted sizable sums of money and time in an attempt to upgrade ores from the various deposits, and also in an attempt to recover manganese from blast furnace slags. In view of current world prices, and the quantity of high grade material available, there is little likelihood that any of these approaches will be found to be economically feasible in the near future. Geology and Mineralogy Mineralogy There are over one hundred minerals that contain manganese. These minerals vary from those with compositions that are predominantly manganese to those having only minor percentages. [Chemical Mineral Composition % Mn Hausmannite Mn304 72 Polianite MnO2, 63.1 Pyrolusite MnO24 60-63 Cryptomelane KR8O16R (R=Mn) Variable PsilomelaneBa Mn Mn8O16 (OH).45-60 CoronaditePb R8O16R (R=Mn) Variable Hollandite Ba R8O16R (R=Mn) Variable Manganite Mn2O3•H20 62 Braunite 3 Mn2O3•MnSiO3 62 Tephroite 2 MnO•SiO2 54.3 Rhodochrosite MnCO3 47 Rhodonite MnSiO3 42 Spessartite 3 MnO•AI2O3•3SIO2 33.3 WadHydrous Mn OxidesVariable Franklinite(Fe Mn Zn)O(Fe Mn)sO3 Variable Asbolan Cobaltiferous wad Variable AlabanditeMnS63.14] Geology From a geological standpoint most manganese deposits are complex. In general, it can be said that all primary deposits of manganese are carbonates or silicates. The most productive and profitable have been those of sedimentary origin and residual concentrations. Examples of these residual types of deposits are associated with the metamorphosed lodes of Madhya, Pradesh, India, and the lateritic deposits of Orissa and Bihar, India; nodules in the residual clays of the Philippine Islands, US southern Appalachians and Arkansas, Ghana, and Brazil. Sedimentary manganese deposits are best exemplified by the Nikopol district of Russia and the Tchiatouri area of Georgia, USSR. Hydrothermal replacements are characterized by the rhodochrosite deposits of Butte and Phillipsburg, MT. In general, the hydrothermal type deposit has not resulted in any large tonnages being produced, but may have given

Jan 1, 1983

By P. B. Venuto, E. T. Strom, S. A. Dixon, W. F. Johnson, T. C. Vogt

Prior to assessing potential for in-situ leaching, it is advantageous to identify the nature of the probable reactants in the ore horizon, including both the uranium species and those in the gangue material. We report mineralogical data on an areally-broad suite of samples from the Westwater Canyon Member of the Jurassic Morrison Formation in the Crownpoint area of the Grants Mineral Belt. Optical microscope, electron micro-probe, X-ray diffraction, spectroscopic and wet chemical analyses were conducted. In these samples, the uranium occurs predominantly as either coffinite or uraninite. The host rock is arkosic sandstone, comprised mainly of detrital quartz and feldspar. The minerals kaolinite and chlorite are present in claystone clasts and calcite occurs as a cement. Major trace elements include molybdenum, vanadium, iron, selenium and sulfur. Carbonaceous organic material is present in the ore and is intimately associated with the uranium mineral when it is coffinite. Geochemical, pyrolytic and 13C NMR analyses indicate organic material is probably a very mature, coaly-type kerogen derived from plant components.

Jan 1, 1982

By Robert J. Morris, John N. Butler

A series of organic collectors has been developed which successfully float synthetic secondary uranium minerals, such as autunite, carnotite, and torbernite. Recoveries up to 97 pct have been obtained. With cleaning of rougher concentrates, ratios of concentration as high as 15:l are possible on head assays of 0.10 to 0.50 pct U308. Additions of certain base metal salts aid in recovery and materially in- crease the rate of flotation and selectivity of the collectors for the synthetic minerals. Flotation tests on natural uranium minerals have not yet equaled results obtained on the synthetics, although these collectors do give better results than conventional collectors for nonsulfide minerals.

Oct 1, 1956

By M. R. Klepper, H. Landsberg

Many of the sedimentary rocks contain small amounts of radioactive constituents. These vary in quantity in different layers. Some recent deposits show rather high activity as; for example, the deep sea oozes and some lake deposits.lv2 Measurements made in boreholes have also shown considerable changes in activity from horizon to horizon. The first to publish data on this fact was Ambronn,3 and recently Russian geophysicists have shown remarkable variations of activity from one layer to the next in various wells. Spak4 felt even that he was able to line up horizons from data measured in two neighboring wells.‡ The measuring of radioactive radiation is fairly difficult. Large errors are possible by the circulation of gaseous emanations in the well and porous strata. It is, therefore, never certain whether the activity of the layer where the instrumental device or collector is located will be measured, or that of some adjacent layer. For this reason it seemed to be advantageous to take samples of rocks into the laboratory and test them there for their contents of radioactive material. Such a method has been followed in the past to distinguish radioactive ore from other rocks. Radioactivity of rocks, especially of the igneous type, was also determined in the laboratory by numerous authors for absolute age investigations.= Corresponding data from studies of sedimentary formations are scarce. Specimens taken from a core of the Bradford oil sandstone were tested by Landsberg and Ingham,7 with the results illustrated in Fig. 1, which shows that within relatively small vertical distances the differences of relative activity were considerable. If one assumes that the distribution of radioactive material is fairly uniform throughout a layer, measurements of radioactive radiation in various horizons would offer additional information for stratigraphic

Jan 1, 1940

By M. R. Klepper, H. Landsberg

Many of the sedimentary rocks contain small amounts of radioactive constituents. These vary in quantity in different layers. Some recent deposits show rather high activity as; for example, the deep sea oozes and some lake deposits.lv2 Measurements made in boreholes have also shown considerable changes in activity from horizon to horizon. The first to publish data on this fact was Ambronn,3 and recently Russian geophysicists have shown remarkable variations of activity from one layer to the next in various wells. Spak4 felt even that he was able to line up horizons from data measured in two neighboring wells.‡ The measuring of radioactive radiation is fairly difficult. Large errors are possible by the circulation of gaseous emanations in the well and porous strata. It is, therefore, never certain whether the activity of the layer where the instrumental device or collector is located will be measured, or that of some adjacent layer. For this reason it seemed to be advantageous to take samples of rocks into the laboratory and test them there for their contents of radioactive material. Such a method has been followed in the past to distinguish radioactive ore from other rocks. Radioactivity of rocks, especially of the igneous type, was also determined in the laboratory by numerous authors for absolute age investigations.= Corresponding data from studies of sedimentary formations are scarce. Specimens taken from a core of the Bradford oil sandstone were tested by Landsberg and Ingham,7 with the results illustrated in Fig. 1, which shows that within relatively small vertical distances the differences of relative activity were considerable. If one assumes that the distribution of radioactive material is fairly uniform throughout a layer, measurements of radioactive radiation in various horizons would offer additional information for stratigraphic

Jan 1, 1940

By Robert M. Rudio

Montana is leading the way in the field of mined-land reclamation with new laws and new ideas. The Montana Department of State Lands is combining new legislation and practical application techniques to all mining operations in the state. Road building, stream relocations, or settling systems can be designed to meet the environmental problems. Mineral exploration now requires a new and closer look at drill site locations, road gradients, and exploration tools. The problems and costs of land rehabilitation must be thoroughly understood by the exploration geologist in order to satisfactorily conduct exploration in Montana.

Jan 1, 1975

THE CHALRYAN.--I think that we have set the stage for the balance of the sym- posium. Most of the emphasis has been placed on the immediate value of every- thing we can do and everything we can learn for the furtherance of the war effort. I believe that ought to be first, but I also believe that this is the time for us to con- sider very seriously not only what these improved methods and techniques do to form a closer approach to ideal segregation but what effect these great quantities of scrap metals and alloys that are going to be produced this year and next, are going to have-what their impact will be-on post- war industry in general and in particular ,, on the primary metals fields. In some cases we have been hearing in the last month or two of the law of diminishing returns coming to the fore. We find alloy simplification growing and certain alloys being produced in great quantities, which will perhaps drop out of the picture some- what as the war ends but never to the lower ( stage they had before. We have I think a pretty good cross- section of the producers, the refiners, the reclaimers and ingot makers, the ultimate users here, and there ought to be some good and helpful discussion. The papers are open for discussion. Mr. Beattie, do you want to make any 1 comment? H. J. BEATTIE.*-To start the discussion I might ask Mr. Deitz what they do with manganese bronze turnings? We segregate the manganese bronze turnings from the other bronze turnings. The value of it seems to be much out of line with the price of ingot, that is, as compared to some of the other alloys like 88-10-2 or 85-5-5-5. I assume it is because they can only use a

Jan 1, 1943

By P. Somasundaran, K. P. Ananthapadmanabhan

A knowledge of the role of effects and interactions of chemical species is important in developing an understanding of the behavior of mixed minerals and natural ores in beneficiation processes such as flotation and flocculation. In this study the role of such species was examined for the calcite-apatite system by conducting flotation of each mineral in various supernatants prepared by mixing with water. Supernatants of apatite and even that of calcite depressed the flotation of calcite markedly in the pH range of 5 to 13. Addition of Ca(NO3)2, K2C03, and K3P04 also produced definite effects under various pH conditions. Apatite flotation was also affected by the mineral supernatants and by carbonate and phosphate solutions. The results are analyzed in terms of the surfactant's solubility properties and the mineral's electrochemical and dissolution properties. While depression of calcite flotation by the dissolved species is found to be governed by depletion of oleate by bulk precipitation, the depression of apatite flotation is caused by the carbonate and phosphate species in the system. Turbidity measurements and a thermodynamic analysis of possible interactions in the system support these considerations. The effect of the supernatant of minerals on their own flotation suggests the important role of kinetics of various surface interactions in comparison to that of mineral dissolution.

Jan 1, 1985

By H. M. Chance

The great outspread of the coal measures over portions of thirtyone of the sixty-seven counties of Pennsylvania, and the large number of workable seamy comprising the coal series,—together with some workable seams lately shown to belong to the (so-called) barren measures,—-create the impression that these fields contain a practically inexhaustible supply of fucl, and those who have estimated or attempted to estimate their available tonnage have generally promulgated this view. But the actual total contents of this coal-field is of no importance to us at present; calculations including all seams, whether thick enough to mine or not, whether pure enough to furnish a marketable fuel or not, whether accessible at reasonable depth or not, are of no practical value. As coal producers, we are interested not in the total contents, but in the total amount of easily accessible coal of good quality contained in beds thick enough for remunerative mining. The estimates contained in this payer refer exclusively to workable and accessible coal of commercial value,—we may call it available" coal. I am not aware that any one has as yet attempted to estimate in

Jan 1, 1882

By H. M. Chance

THE great outspread of the coal measures over portions of thirty-one of the sixty-seven counties Of Pennsylvania, and the large number of workable seams comprising the coal series, together with some workable seams lately shown to belong to the (so-called) barren measures, create the impression that these fields contain a practically inexhaustible supply of fuel, and those who have estimated or attempted to estimate their available tonnage have generally promulgated this view. But the actual total contents of this coal-field is of no importance to us at present; calculations including all seams, whether thick enough to mine or not, whether pure enough to furnish a marketable fuel or not, whether accessible at reasonable depth or not, are of no practical value. As coal producers, we are interested not in the total contents, but in the total amount of easily accessible coal of good quality con-tained in beds thick enough for remunerative mining. The estimates contained in this paper refer exclusively to workable and accessible coal of commercial value, we may call it "available" coral. I am not aware, that any one has as yet attempted to estimate in

Jan 1, 1882