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By J. H. Wiggins

In 1919 the United States was threatened with a shortage of gaso- line. In spite of this well-known fact, a detailed field investigation has shown that in one stage only of handling crude oil the volume of gasoline that evaporates is equal to one-thirtieth of the country's yearly gasoline production. This loss occurs during the few days that the oil is stored on the leases before being taken by the pipe line, and in 1919, in the Mid-Continent field alone, it amounted to 122,100,000 gallons. Large as it is, it is only a part of the loss on the lease. Investigation has further shown that the gasoline in crude oil evaporates from one-half to six-tenths as rapidly as the same gaso- line after being distilled and stored, all evaporative conditions being the same. Many wastes in the oil fields are called "necessary." By this is meant that the cost of preventing the waste is greater than the gain through saving. Evaporation losses have fallen heretofore in this category, but now they must be considered unnecessary. In other words, it is no longer economical for any handler of crude oil to permit losses through evaporation. In accordance with its purpose of seeking to conserve mineral resources, the Bureau of Mines investigated the loss of gasoline by evaporation in the storage and handling of petroleum. Inasmuch as most producers had not decided that their losses justified cor- rective measures and no evidence was available on the comparative losses in various stages of handling the oil, the investigation was limited to determining by experiment and observation the nature and magnitude of evaporation losses, where the greatest losses are, and the factor controlling evaporation.

Jan 1, 1922

By M. C. Irani

This Bureau of Mines report tabulates methane emissions from U.S. bituminous coal mines with daily emission rates of at least 100,000 cfd according to States, counties, and coalbeds. Most of the methane emitted is from mines in the Appalachian States. Total daily emission in 1975 was 216.3 MMcfd, compared with 227.0 MMcfd in 1971 and 214.5 MMcfd in 1973. Thirty counties in nine States hid daily methane emissions of 1 MMcfd or more. These emitted 93 percent of the total methane. The highest emissions were from Monongalia County, W. Va., which accounted for 18.9 percent of the total. This was followed by Marion County, W. Va., 9.6 percent; Buchanan County, Va., 8.3 percent; Jefferson County, Ala., 6.1 percent; and Washington County, Pa., 5.9 percent. The Pittsburgh coalbed emitted 45.7 percent of the total methane, followed by the Pocahontas No. 3 coalbed with 12.9 percent. The report lists 196 mines, of which 60 had daily methane emissions of 1 MMcfd or more. Included in this compilation are the identification and thickness of the coalbed, methane emission, coal production and ventilation rates, number of drifts, shafts, and slopes used for ventilation purposes, shaft depth, age of mine, and gas-to-coal ratio.

Jan 1, 1977

By Raymond G. Travis

This paper, which describes mining methods and practices at the Hurricane Creek bauxite mine of Reynolds Mining Corp. in central Arkansas, is one of a series being prepared by the Bureau of Mines on mining methods, practices, and costs in various mining districts of the United States. The Hurricane Creek mine is in sec. 12, T. 2 S., R. 14 W., and sees. 7 and 18, T. 2 S., R. 13 W., Saline County, Ark., about 4 miles east of Bauxite. (See fig. 1.) Bauxite has been mined underground at the Hurricane Creek property since 1942. The operation is notable for relatively high recovery of bauxite under the adverse conditions of unconsolidated water-bearing overburden and unstable clay floor. Controlled caving, timbered stope walls, and efficient drainage systems on the surface and underground have minimized the problems and raised ore recovery about 25 percent above that formerly obtained.

Jan 1, 1961

By A. Vilinska

Microorganisms have a tremendous influence on their environment through the transfer of energy, charge, and materials across a complex biotic mineral-solution interface. Recent developments in biotechnology have not only aided hydrometallurgical leaching operations but also shown great promise in mineral beneficiation processes. The adhesion of bacteria on minerals alters the surface properties relevant to flotation and flocculation of minerals. The biomodification of mineral surfaces occurs through the attachment of microbial cells, oxidation reactions and adsorption or chemical reaction with the metabolite products. Several types of heterotrophic and chemolithotrophic bacteria have been successfully applied in flotation and flocculation processes for the last two decades. Al-though the potential of microorganisms in minerals beneficiation has been realised by several re-searchers from their laboratory investigations, the studies were mostly confined to pure mineral systems and there is hardly any sincere effort to apply the methodologies on ores. This paper presents a brief summary of the literature in bioflotation and bioflocculation, and attempts to outline new dimensions of research for a practicable application of this technology in mineral industry.

Jan 1, 2014

By F. W. Wessel

Manganiferous carbonate slates of the Cuyuna range, which are part of the unoxidized thin-budded iron formation, represent a large potential source of manganese. This report details recent bench-scale research by the Federal Bureau of Mines in applying mineral-dressing techniques to these materials in order to investigate their potential uses. Work outlined in the report was directed toward the production of concentrates usable as iron-blast furnace feed, but an equally important objective might have been to furnish an enriched feed for extractive processes for recovering manganese. Flotation concentrates were prepared that contained 11.1 percent manganese, 27.8 percent iron, and 12.2 percent silica, with recoveries of 73 percent of the manganese and 48 percent of the iron. Calculated analysis for a simulated sinter suggests a product containing 16.0 percent manganese, 40.2 percent iron, and 17.6 percent silica, with 31 percent recovery of the dry weight of the ore. The silica in the flotation concentrates was due to quartz and iron silicates. Substantial quantities of the iron silicates (stilpnomelane and smaller amounts of minnesotaite) were present in the slate, and the need to reject these minerals limited the recovery of iron. The sintered flotation concentrate would be usable as ferruginous manganese ore for iron blast-furnace feed because of its favorable manganese silica ratio. The unsintered flotation concentrates, representing 45 percent of the feed weight and containing manganese enriched in the ratio of 1.6 : 1, also could be used as feed to processes for extracting manganese.

Jan 1, 1961

By J. L. Eakin, J. P. Powell

"The increased costs of exploration and drilling of new oil fields and the continued success of water flooding in nearly depleted oil fields have created a demand for information on the results obtained from individual projects. The Bureau of Mines has published several reports concerning water-flood activity in the Midcontinent area and at the request of the industry has continued to collect and disseminate this information. This report was written in response to these requests. It describes in detail the water-flooding projects in Anderson, Franklin, Linn, and Miami Counties, Kans., and includes methods of water treating and the results obtained. The production histories of each county and many water-flood projects are shown graphically from the date of the first development. Maps of most of the major projects, showing their status as of January 1, 1953 are presented also.The practice of injecting water to stimulate oil production was legalized in Kansas in 1935, and the first water-flooding project authorized in this four-county area was initiated by the Texas Co. in December 1935 in Linn County. Forty-nine projects2/ initiated in the area to January 1953 are estimated to have recovered approximately 10 million barrels of oil that would not have been produced by methods used previously. About 7,900 productive acres had been, or are, flooded by these projects, and approximately 136 million barrels of water had been injected.These four counties in the eastern Kansas shallow production area3/ were an important factor in the early history of the Kansas oil and gas industry. This position has been maintained from the very beginning through the early period of vacuum and air injection and into the era of water flooding. The location of the area and the relative position of the four counties and water-flooding areas in each are shown in figure 1.The first drilling for oil in this area in 1860 resulted from investigations of the existence, and use by the Indians, of so-called tar or oil springs. The first wells drilled were nonproductive, and the impending Civil War caused the search for oil to be discontinued. In 1884 a few shallow oil wells were drilled near Paola, and completion of several gas wells near that city led to subsequent drilling of an oil well, which was completed in June 1885, having an initial flow of 10 barrels of oil daily.In 1904 the original Paola gas field became a good oil-producing field. In 1905 the Rantoul field in Franklin and Miami Counties was opened; and drilling activity spread throughout the adjoining area, resulting in development of several shallow oil pools in Linn and Anderson Counties. The first ""shoestring"" pool in eastern Kansas to produce oil was probably the Paola or Pressonville shoestring, which was discovered in 1917. The rate of oil production from the area declined until 1919, when the Centerville shoestring pool was discovered. Discovery of the Colony gas field in 1921 was followed within a few months by drilling of the Garnett and Garnett and bush City shoestring pools. The Schermerhorn pool (now part of the Centerville field) s discovered in 1927, and the Kincaid shoestring pool was first drilled in 1931. The oil-production histories of the individual counties are discussed separately."

Jun 1, 1953

By J. W. Jensen

EXTENSIVE research and development was performed on the manganese-copper vibration-damping alloys to determine the relationship between the properties of the alloys and variations in composition, fabrication, Mid heat treatment. Mn-Cu alloys with unusually high specific damping capacity, 20 to 25 percent at a stress of 5,000 psi, have also the following useful properties: Tensile strength, 90,000 to 110,000 psi; yield strong, 60,000 to psi; elongation, 20 to 25 percent; hardness, 90 Rockwell B; and fatigue limit at, 28,000 to 30,000 psi. Both standard and special methods of testing were employed to obtain data on strength, modulus, hardness, resistivity, dilatation, micro-structure, crystal lattice, and damping capacity. The extensive tabular and graphical data on these properties are presented for alloys containing 50 to 85 percent as quenched d solution) and after various aging treatments. Expansion coefficients for all Mn-Cu solid solutions are graphed and a dilatometer study of contraction during aging is reported. Although high damping capacity is associated with aging to precipitate a-Mn from solid solution, with a cubic-tetragonal transformation and with the occurrence of antiferromagnetic ordering in Mn-Cu alloys, a tenable theory of the damping mechanism has not been reached.

Jan 1, 1965

By G. M. Swinkels

Sherritt Gordon and Cominco, with financial assistance from the Canadian Government through PAIT, have developed a hydrometallurgical process for refining copper from sulphide concentrates. The main objective of the project was to develop a process applicable to a wide range of concentrates with respect to copper content, other metals content and impurities, within the economic parameters set by present smelting and refining practice. Other important objectives were to recover sulphur in its elemental form and not as sulphur dioxide to assure improved hygienic conditions and a negligible impact on the environment. For the most abundant and relatively refractory chalcopyrite concentrates, the first step of the process is thermal activation with hydrogen to decompose chalcopyrite and pyrite, commonly associated with it, into more reactive sulphides more amenable to leaching. The iron is then selectively extracted by sulphuric acid leaching and subsequently rejected as jarosite. High-bornite concentrates do not require thermal activation and acid leaching; they are subjected to another hydrometallurgical iron removal step. The high-grade copper sulphide resulting from iron removal, and containing all of the initial precious metals, is then leached under oxygen pressure to produce elemental sulphur and copper sulphate solution . After suitable solution purification, the copper is recovered by high-current-density electrowinning as wire-grade product. Precious metals remain in the leach residue and are recovered after separation of the gangue materials and elemental sulphur. The laboratory and pre-piloting test work had indicated copper and precious metals recoveries comparable to those achieved in current practice. The process was shown to be suitable for handling relatively low-grade concentrates and, in addition, it was capable of high recoveries of associated zinc, molybdenum, nickel and cobalt in saleable form.

Jan 1, 1978

By Stopford Brunton

For many years it has been accepted as axiomatic that the greater number of 'veins' or 'leads' in the gold districts of Nova Scotia are of the 'interbedded' type. The corollary to this hypothesis is that the vein or lead will have a continuous hanging-wall of one kind of rock, and a continuous footwall of the same or another kind of rock; but the essential point is that the foot and hanging walls are, according to this theory, both continuous and of uniform composition throughout; and that the vein or lead conforms to the bedding of the adjacent strata. With regard to the deposition of the gold in the rocks, the probability is that the key of the problem is contained in a statement by E. R. Faribault, of the Geological Survey of Canada: "The combined effect of cleavage, jointing, and stratification is to cause the rocks, especially the quartzites, to break into rhombohedral blocks". It is essential to comprehend that the rocks of the Province are no doubt folded into anticlines and synclines; but also it must be fully realized that the gold deposits and pay-shoots do not depend so much upon these as upon the fractures resulting from the disturbance caused by the intrusion of granite masses, and controlled by the combined effect of cleavage, jointing, and stratification. These fractures would form the channels through which the ore-bearing vapours and solutions would rise, and at the junctions of these fractures, where the fracturing was greatest, the easiest passages would be afforded to the ore carriers, with the result that the ore-shoots would be found at or near the intersections of fractures. It is a significant fact that in at least thirteen different districts throughout the Province, operators have at various times remarked upon the occurrence of rich ore at the intersection of 'leads,' 'veins,' 'beds,' etc.

Jan 1, 1928

By Arthur F. Hagner

The titaniferous magnetite deposit at Iron Mountain, Wyoming, is in Precambrian anorthosite. Individual ore bodies are lenses, commonly arranged en echelon, conformable to the platy crystal structure and compositional layering of the anorthosite; a few transect these features at various angles. The ore bodies are on the east flank of the principal anticline in the anorthosite mass. Magnetite and ilmenite, accompanied by spine!, are the ore minerals. The principal gangue minerals are olivine, which was introduced with the ore, and plagioclase, the chief constituent of the anorthosite. The anticlinal region appears to have been a structurally weak zone, and westward-bowing curves of the axis were especially favorable sites for localization of the two largest massive ore bodies. These bodies are synclinal and plunge southeast. The proportion of magnetite-ilmenite to olivine and to anorthosite appears to be related to structural features. Where magnetite-ilmenite is present with olivine, the magnetite-ilmenite is encountered along the most pronounced parts of a fold where anorthite content is highest, whereas olivine is associated principally with more gently folded portions. During granulation and recrystallization of the anorthosite mass, temperature and pressure changes furnished the energy required to release and mobilize iron and other elements that migrated to areas of low pressure, the ore zone. Some iron and magnesium may have combined with silica from partly dissociated plagioclase to form olivine. The ore formed by replacement of anorthosite as indicated by: (1) the marked changes in mineralogy along strike, dip, and plunge of an ore body; (2) the concentration of massive ore in folds and olivine on limbs; ( 3) the halo of low-grade mineralized rock that transects the structure of the anorthosite in the hanging wall; and ( 4) the layering in the large southern ore body, that strikes more easterly than the trend of the body.

Jan 1, 1968

In flotation, particulate materials are separated by controlling the hydrophobicity of the particles using appropriate collectors. In this regard, contact angle (?) is the most important process variable. However, the flotation models used in industry today do not include ? as a parameter. As result, flotation circuits are designed based on the first-order flotation rate constants (k) determined from laboratory experiments. A problem with this approach is that laboratory experiments usually give substantially higher k values than achievable in full-scale operations, which makes it difficult to use the model for plant design. In the present work, we have developed a model from first principles using both surface chemistry and hydrodynamic parameters, such as ?, ?-potentials, surface tension (?), particle size, energy dissipation rate, etc. The basic approach is similar to the one developed previously for bubble-particle interactions under laminar flow conditions (Yoon and Mao, J. Colloid and Interface Science, 181, 61, 1996) except that the model parameters have been modified by considering the turbulence in a flotation cell. In addition, the model describes the recovery processes in froth phase, including bubble-coarsening due to coalescence. Based on this model, we have developed a computer simulator (FlotSim) that can be used to design flotation circuits from the mineralogical (or liberation) data on the feed and the hydrodynamic characteristics of a flotation machine. Since the model is dynamic, it can also be used for process control. Further, the simulator has predictive capacity as it is based on a first-principles model. The model-based simulator has been validated in a carefully controlled bench-scale flotation experiments. Keywords: flotation kinetics, flotation model, contact angle,?-potential, size-by-size recovery, liberation, DLVO theory

Sep 1, 2012

By Robert R. Walden, LeMont West

K ENTUCKY'S first acid-grade fluorspar flotation Kmill, shown in Fig. 1, was placed in operation Aug. 1, 1952, by the Pennsylvania Salt Manufacturing Co. at Mexico, Ky. During 1951 a critical shortage of acid-grade fluorspar developed and it became necessary for the company to produce part of its fluorspar requirements. In 1951 the company purchased the Crider and Lennen metallurgical fluorspar mill and an adjacent stockpile of tailing at Mexico, Ky. The tailing, assaying about 26 pct calcium fluoride, originated from log washer and jig mill concentrators in the area. As the mill did not have a fluorspar dryer or convenient rail facilities, the company leased the Burleson concentrator at Marion, Ky., where these facilities were available. At Marion, Ky., on the Illinois Central Railroad, dry acid-grade fluorspar is transported direct to the company's Calvert City, Ky., hydrofluoric acid plant. The Mexico flotation plant was reconditioned and designed to produce acid-grade fluorspar from the jig tailing stockpile. The new plant flowsheet is shown in Fig. 2. The ore feed, old tailing, which contains 10 pct of waste rock and coarse gravel assaying approximately 8 pct CaF,, is bound together by sticky clay

Jan 1, 1955

By J. Baz-Dresch

A custom-designed shotcrete system, consisting of an 8-m3 (10-cu-yd) transit mixer and a shotcrete spray boon carrier, is used by a two-man crew to transport and place up to 25 m3 (32 cu-yd) of steel fiber reinforced, dry, silica fume shotcrete per 11-hour shift. Shotcrete is custom blended by a local supplier and delivered predampened. Mix design and quality control are performed with a computer program that develops and graphs a properly balanced mix based upon the materials sieve analyses.

Jan 1, 1992

By James R. Boyle

The value of Alabama's nonfuel mineral production in 1985 was $405.9 million, a slight decrease from the record high of 1984. With the exception of clays, output of most nonfuel minerals increased over that of 1984. Alabama was second in the Nation in production of crushed marble and bauxite; third in firre clay; fourth in masonry cement and kaolin; fifth in portland cement and lime; and sixth in ferroalloys and recovered sulfur, Alabama ranked 20th in the Nation in value of nonfuel minerals produced, but ranked 13th in value of industrial minerals. Valuewise, Alabama produced 2.4% of the Nation's industrial minerals.

Jan 1, 1987

By John G. Kelly

"In 1982 an extensive study was carried out to determine the best means of size reduction for the ore to be hoisted through the borehole hoisting system at Sherritt Gordon's Fox Mine.The study examined three alternatives:1. a jaw crusher,2. pneumatic rockbreaker(s) at a grizzly, and3. hydraulic rockbreaker(s) at a grizzly.The final decision was a compromise between alternatives 2 and 3. Two rockbreakers, one pneumatic and one hydraulic, were installed over a single grizzly. Some modifications have been made to the system, but over-all it has operated at acceptable levels since its installation in July 1983.As all the ore passes through a jaw crusher before being hoisted to surface, an evaluation of the relative performance and cost-effectiveness of the jaw crusher and the two types of rockbreakers is possible. This paper outlines the initial study, and compares the three breaking systems in operation at Fox Mine.IntroductionThe Fox Mine of Sherritt Gordon Mines Ltd. is located 800 kilometres north of Winnipeg near Lynn Lake in Northern Manitoba. Production at the copper-zinc orebody began in 1970 at a rate of 3,000 tons per day. Over 12.5 million tons will have been hoisted from the underground mine when the ore reserves are depleted in October 1985.The mining method at Fox Mine is sub-level open stoping with delayed backfilling are from the upper level stopes, above the 2000 level, is mucked on the main levels established at 400-ft elevation intervals, and is fed through a central orepass to the crusher located on 2100 level. Production in the lower levels commenced in 1975, and ore from the 2200 and 2400 level stopes was hauled up a 15010 ramp by 26-ton trucks to the 2000 level orepass dump. Projected production rates from the 2600 and 2800 levels using the trucking system were too low, and therefore, in 1983 a borehole hoisting system was commissioned to hoist that ore'!'. One thousand tons per day of ore are skipped through an 8-ft diameter borehole from the 2650 level loading pocket and dumped on the 2000 level. The ore is transferred by LHD to the main orepass for crushing before being conveyed to the main shaft for hoisting to surface (Fig. 1)."

Jan 1, 1986

By V. I. Lakshmanan

Crown ethers are gaining importance in separation technology specifically for rare earth elements (REE, La to Lu plus Y) and precious metals (Au, Ag, Pt, Pd, Rh and Ir) due to their specific binding ability, metal complex stability and high extraction efficiency. The selectivity of crown ethers in extraction of these metals depends on different factors, including the cavity diameter and nature of a donor atom of the crown ether, size and charge of the metal ion, diluents and counter ion. Demand for strategic REE and precious metals are consistently increasing in the world while the separation of these metals is most challenging tasks. In this paper, the use of crown ethers in separation of REE and precious metals, reaction mechanisms and simplified process flowsheets will be elucidated. New reagents with high selectivity for the separation of these metals are further expected to produce high purity metals.

By S. Pastor, S. Hahn

"As the concept of autonomous haulage systems (AHS) moves from prototypes to production-ready applications, the operating performance of the haul road will become critical to the overall success of autonomy in mining. Deterioration in road performance will require remediation, human intervention and significant, albeit temporary, changes to operating procedures, to accommodate road maintenance. With autonomous trucks comes the opportunity to reduce road formation and operating width. This will, therefore, generate potentially significant reductions in stripping ratios and improvements to mine economics, but only if the design of the road, and its associated deterioration rate, is predictable and manageable, based on the materials used to construct the road and the maintenance interventions to be carried out on the road.This article presents the assessment of a digital photogrammetric approach to the characterization of a mine haul road surfacing, or wearing course material. Design and maintenance parameters for these roads are currently determined partly from physical particle size distribution (PSD) assessments of ‘in-road’ material. However, this approach does not accommodate the need, nor leverage the benefits from, AHS. The digital imaging approach is assessed in this article, using two standard digital analysis software tools, together with in-service mine haul road wearing course samples and images that are analyzed to determine the applicability and reliability of the approach to deliver a real-time assessment of haul road surfacing conditions and thus to identify the road maintenance interventions required to address deterioration.Enhancements in mine road design, construction and management for the past 20 or more years has largely been focused on short-term tactical needs. These improvements have not been matched by advances in the fundamental technologies that underpin mine road design and management and, although the quality of mine roads have probably"

Jan 1, 2015

By S Bluhm, L van den Berg

In planning mine ventilation systems, heat issues are normally associated with deep-level mines where auto-compression and virgin rock temperatures play a major role. However, a number of mines suffer from high ambient temperatures and humidity, very steep virgin rock temperature gradients and an influx of hot groundwater. Mines in Australia and, particularly, South-East Asia have to deal with these environmental conditions, both in the operational and planning phases. These operations normally have to take heat into consideration during the planning stages at much shallower depths. In high rainfall regions, the water table is saturated and groundwater flow rates are particularly high, which add significant water heat load potential to the mine ventilation system.This paper considers the ventilation challenges associated with hot groundwater conditions in mechanised mines. The paper is based on specific project experience gained from a number of projects in the United States, Australia and South-East Asia and draws on data from mines that experience hot groundwater conditions. For one site, actual decline temperature survey measurements, modelling techniques, management strategies and design considerations are presented.CITATION:Van den Berg, L and Bluhm, S, 2015. Ventilation planning considerations when dealing with hot groundwater, in Proceedings The Australian Mine Ventilation Conference, pp 211–218 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By F. M. Goodwin, Campbell. John, W. J. Hiffs, G. W. Jones

"INTRODUCTION In cooperation with The Edison Electric Illuminating Co. of Boston, Mass., and the Boston Consolidated Gas Co. a survey has been conducted continuously since 1929 by the United States Bureau of Mines to determine the general hazards of combustible gases and vapors in manholes of the Edison Electric Illuminating Co. The New England Telephone & Telegraph Co. also has cooperated in the investigation, and tests have been made in its manholes since May 1, 1933.Yearly reports 6 giving the results obtained since the start of the survey have been published.The method and procedure of conductin, the survey in 1935 were the same as heretofore.ACKNOWLEDGMENTSThe cooperative investigation was arranged through the interest and effort of F. D. Comerford, president of the Edison Electric Illuminating Co. of Boston; E. N. Farnesworth, Jr., vice president and general manager of the Boston Consolidated Gas Co.; and A. C. Fieldner chief engineer, Experiment Stations Division, U. S. Bureau of Mines. Thomas H. Haines, superintendent, Distribution Department, of the Edison Electric Illuminating Co., cooperated in furnishing men and information for the work,"

Oct 1, 1936

By William P. Shinn

It is almost exactly seven years since the last previous meeting of the Institute in this city. In a paper on " Pittsburgh, its Resources and Sorroundings," read at that meeting, I showed that Allegheny County had produced in 1878, " one-twelfth of all the pig-iron,.... two-ninths of all the rolled iron (except rails), over one-eighth of all the Bessemer and open-hearth steel, two-thirds of all the crucible blister and puddled steel, one-fourth of all the glass, one-eighth of all the coal, and one-sixth of all the pig-lead produced in the United States;" and the object of this paper is to show that, great as the record then was, it has been greatly surpassed since.* Population. In my former paper I expressed the opinion that the census of 1880 would show the population of Allegheny County to be in excess of 300,000. The census report made it 355,869. The following shows the growth of the county in population from 1790 to 1880: 1790,...........10,309 1800,........... 15,087 1810,...........25,317 1820,...........34,921 1830,...........50,552 1840.............81,235 1850............138,290 1860............178,881 1870,...........262,204 1880,...........355,869 This makes Allegheny County, in 1880, rank sixth in population of the counties of the United States, whereas in 1870 its rank was ninth. The population of Pittsburgh in 1880 was 156,359, being twelfth

Jan 1, 1886