Search Documents

By S. D. Michaelson

Open pits and quarries are the major sources of all "hard rock" tonnage mined today. Normally, ore is fractured from the pit face by blasting and then truck-hauled to a primary crusher where pro- cessing begins; overburden (or waste) is generally truck-hauled from the pit to dump areas. Truck haulage of blasted ore and overburden accounts for some 25 to 50% of total mining costs in a typical open pit and commonly is the largest single cost factor. Obviously then, cost reduction efforts should properly focus on improving existing haulage systems and developing new breakthrough techniques for material transport. Continuous flow systems for large tonnages ordinarily will result in a lower cost than batch systems such as truck or rail haulage. Continuous flow with pipelines for liquids and slurries, or conveyors for medium to coarse dry materials (in the -8-in. range) are the economic answers for bulk materials handling over reasonable distances.

Jan 11, 1968

By H. Ries

SPECIAL sands are those that are employed for special purposes. They have a limited use, as compared with sands for concrete and plaster. The sands discussed in this chapter are those used for foundry purposes, glass manufacture, filter beds, abrasive purposes, sandblasting, engine sand, sand for sheet asphalt, and furnace sand. These sands are almost invariably high in silica, consisting chiefly of quartz grains. In some-for instance, glass sands-freedom from ingredients other than silica, such as iron oxide, is important. Certain grades, like filter sand, require rather careful sizing, and in foundry sands the bond, usually clay, is important. One deposit may sometimes be used to supply several grades or types of sand by appropriate methods of screening and washing. The special sands discussed here are usually obtained from deposits of unconsolidated material but sands high in silica are derived occasionally from soft sand- stones that can be disintegrated easily. Requirements are not the same for all uses, and, while certain properties may be demanded, there are no officially adopted standard tests except for foundry sands. FOUNDRY SANDS Definition-Foundry sands include those siliceous sands that are used to make the forms for casting metals. If these are employed for making molds, they are known as molding sands; if for the cores that form the hollow spaces in the casting, they are called core sands. Naturally bonded sands are those containing a variable, though not usually large, amount of clay, which serves as a bond. Synthetic sands, now much used, represent an artificial mixture of sand with usually fire clay or bentonite. Core sands may be bonded with oil, cereal binders, resin, pitch, or other materials. The foundrymen apply the term "sharp sand" to one that is free from bond. Properties-The important properties to be tested at room temperature are texture or fineness, permeability, strength, deformation, and flowability. Those tested at elevated temperatures are compressive strength, expansion and contraction, sintering point, and durability. More attention probably has been given to research on the properties

Jan 1, 1949

By AIME

TURMOIL has been rampant in the lead producing industry during 1946. The chronic labor shortage was aggravated by various work stoppages in mines, smelters, and refineries, while shortage of materials was widespread. Price uncertainties helped to confuse the situation in many countries and particularly in the United States until the removal of price control in the latter part of the year. At the end of the first year of peace, lead, which had been comparatively plentiful during the war years, was a scarce and high-priced metal throughout the world. It is the hope of the industry that the law of supply and demand, if allowed to operate without interference, will bring about a satisfactory balance between production and consumption. Under these circumstances it is not surprising that there have been few important developments in the metallurgy of lead, though a number of items of general interest to the industry have been reported. An ore body which may prove to be of considerable importance has been discovered at Mpanda, Tanganyika. The scarcity of lead ore is illustrated by the announced reopening of the La Manche lead mine in Newfoundland, idle for 56 years. A new lead producer came into production when Rhodesia Broken Hill started up its new smelter. Lead concentrate of 75 per cent grade is smelted in Scotch hearths and the lead is refined to market grade by the Harris process without desilverizing. Production is about 1000 tons per month. One Australian lead producer, Mount Isa, has returned to lead production after having operated its lead plant for the production of copper during the war. The East Chicago plant of the International Smelting and Refining Co. has been sold to the Eagle-Picher Co.

Jan 1, 1947

By George Cole

WHILE many parts of Canada's pre-Cambrian shield are well served by railway, it is frequently necessary for prospecting purposes to proceed farther into areas in-accessible by rail. To such areas in summer the canoe was at one time the accepted means of travel for the prospector while the dog team was much used in winter. Al-though summer travel was much improved by the development of the outboard motor, the lack of facilities for cheap transporta-tion has been a serious hindrance to the employment of capital in opening up the distant fields. The pre-Cambrian surface of Manitoba, like that of Ontario, is hummocky, with rounded hills and ridges of rock alternating with basinlike depressions and valleys oc-cupied by lakes and rivers or by many low-lying portions covered with muskeg. Routes to the mines have not usually been direct or easy and seasonal vagaries have presented problems in themselves. In summer, water transportation may be the cheapest method for the longer dis-tances but it is not every water route that will satisfy the conditions of loading freight onto a boat or scow and of conveying it without interruption to its destination. By its location, a mine may require a large program of boat transportation in summer over part of its route, to be followed by winter freighting for the remainder. In order to carry on development and produc-

Jan 1, 1940

By R. Venkateswar, G. C. Sresty

Size measurement is important in characterization of fine particles. Commonly employed size measurement techniques such as sieving, microscopy, and sedimentation are discussed in this paper. Operating principles, advantages and limitations of these techniques are discussed based on the published information and working knowledge with several of these instruments at the authors' laboratories. A brief description of the recently developed equipment for fine particle characterization is also included. At the end of the paper, a rationale is presented for selection of the size analysis equipment based on specific requirements.

Jan 1, 1980

By A. R. Gregory, M. R. J. Wyllie

The literature reveals that scant attention has been paid to the systematic experimental determination of the formation factors of unconsolidated porous media. No experiments appear to have been made on the effect of increasing cementation on the formation factor of an initially unconsolidated porous medium. Measurements have accordingly been made of formation factors as a function of porosity for aggregates of spheres in the porobity range 12-56 per cent and of cubes, cylinders, discs and triangular prisms in the porosity range 30-45 per cent. The results are examined in the light of the theoretical equations of Clerk Maxwell. Fricke and Slawinski. Aggregates of unconsolidated spheres and beach sands have been artificially cemented with silica and the formation factor-porosity relationships determined. A theory is outlined which seeks to explain the results obtained and which postulates that formation factor and porosity data for consolidated sandatones may be used to determine the original porosity of the unconsolidated sands from which the consolidated sandstones were derived. It follows also that for consolidated sandstones F' = C where F is formation factor, fractional porosity and C and k are constants. INTRODUCTION All schemes of electric log interpretation implicitly or explicitly require the use of formation resistivity factors or? as they are now generally called. formation factors. 'The originator both of the concept of formation factor and of the use of formation factor data in electric log interpretation was Archie.' More recently it has been suggested that formation factors are of value in describing fluid flow in porous media. A full discussion of this problem together with adequate reference.: has been given by Wyllie and Spangler.' In spite of the theoretical and practical importance of the subject, there appear to be remarkably few basic formation factor data in the petroleum literature. A wider search reveals that this situation is nut confined to the literature of the to industry. at various times over the last century, attempts have been made to compute the theoretical relationship between the formation factor and porosity of simple systems of unconsolidated particle.. However. the formulae derived are not all identical and the experimental evidence adduced in support of each i; not wholly convincitng. Most of the experimental work has been carried out on system. of unconsolidated spheres, although some attention has been given to systems of spheroids and cylinder. Other simple shapes have received neither theoretical nor experimental investigation. The writers feel that a better understanding of the formation factors of complex systems of practical importance requires a firm foundation of reliable experimental data applicable to simple systems. Accordingly, they have reviewed the relevant literature and have determined experimentally the relationship between the formation factor and porosity of unconsolidated aggregates of particles of regular geometrical shapes. Some experiments have also been carried out to investigate the effect of cementation on the formation factor-porosity relationship. PREVIOUS WORK Although the term formation factor was not used. the relationship between the resistivity of a solution containing dielectric solids and the resistivity of a similar solution not containing solids is an old and important problem. The formation factor of a system of dispersed spheres as a function of porosity was considered by Clerk Maxwell. Maxwell arrived theoretically at the following expression: where F is formation factor and fractional porosity. Lord Rayleigh' also examined the problem of the formation factor of systems of spheres and cylinders and concluded that for spheres Clerk Maxwell'.; expression gave a value of F whirl]. at low porosities particularly, was too small. However,

Jan 1, 1953

By AIME AIME

TECHNICAL achievement in mining will be rewarded at the forthcoming Annual Meeting of the Institute when the William Lawrence Saunders Gold Medal will be presented to Herman C. Bellinger. Mr, Bellinger was unanimously selected on the first ballot of the Medal Committee. Mr. Bellinger has had notable technical success as vice-president in charge of operations for the Chile Exploration Co., a position he has held since 1920.

Jan 1, 1941

By F. L. Bosqui

Discussion of the paper of F.* L. Bosqui, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 101, May, 1915, pp. 997 to 1033. SIDNEY J. JENNINGS, New York, N. Y.-I notice Mr. Bosqui says that zinc dust can be used profitably. I had occasion recently to try to ship some zinc deist to South Africa, owing to the. high price of zinc in the last six or eight months and the difficulty in getting zinc sheets We were informed that the steamship companies in England refused to accept zinc dust for shipment through the tropics on the score that it was an explosive mixture. C. W. MERRILL, San Francisco, Cal.-In the early days zinc dust was packed in wooden casks. The steamers at that time were very chary of transporting it. It was put on the deck in the wooden casks, and if the zinc dust got wet it exploded. Since that time we have used hermetically sealed cases, in which case there is no risk whatever in its transportation.. This rule of the steamship companies is perhaps another sample of their ultra-conservativeness. HENNEN JENNINGS, Washington, D. C.-Unfortunately, I have not yet read Mr. Bosqui's paper, but believing it might interest you to know something of the beginning of the cyanide process on the Rand, I will speak briefly as to my own knowledge and experience of the early initiation of this process in South Africa. I took the position of consulting engineer of H., Eckstein, the parent firm of H. Eckstein & Co., and a branch of the firm of Wernher, Belt ,C Co., at Johannesburg, in December, 1889, and at that time the Robinson Co. managed by them was the premier company of the fields. Up to this date plate amalgamation and catchment of a small percentage of concentrates by blankets, and in a few instances Frue vanners, were the main gold-saving devices used and had obtained an extraction' of only about 65 per cent of the gold contents of the ore. Also at that time the orebodies were seen to be changing from oxidized deposits to pyritic at varying depths from 50 ft. to 300 ft. below the surface, and uneasiness was felt as to future recovery. The deepest exploitation at any of the mines was not much below 300 ft.

Jan 12, 1915

By Martin A. Mayers

Five-sixths of all the coal that is mined in the United States is burned, without previous treatment other than screening, for the production of heat and power, so that its value is fixed by its suitability for this purpose. Nevertheless, the characteristics of individual coals that determine their fitness for use in particular pieces of combustion equipment are not yet well known. This condition is due not only to the small extent of our knowledge concerning coal itself, but also to our comparative ignorance of the nature of the combustion process. The following paper is an analysis of the combustion process as it occurs in industrial furnaces, based largely on the results of laboratory research on combustion rates. From this analysis it is possible to determine the characteristics of the fuel that limit the capacity of a given piece of combustion equipment. Limitations imposed by other factors than the attainable speed of combustion will not be considered, since they are subject to a different type of analysis involving the balancing of maintenance costs against fixed charges. In order to observe the relations among the various factors that affect the speed of combustion, representative particles of fuel will be followed through two types of furnaces. A pulverized-coal furnace will be considered first, because the independence of the individual particles facilitates the analysis of the effect of furnace conditions. The second example will be a grate-fired furnace in which ignition of the fuel takes place on the underfeed principle. This includes both underfeed and chain grate stokers, (8)† but does not include hand-fired furnaces and some overfeed stokers. The furnace will be considered to be large enough, the temperature high enough, and enough air provided, to burn the fuel completely, without, for the moment, specifying these quantities more completely. Furnaces Burning Pulverized Coal In a pulverized-coal furnace, the fuel particle is carried, in a stream of air, into the furnace, where it is subjected to radiation from the flame and from the hot walls of the furnace. The increase of particle tempera-

Jan 1, 1936

By Martin A. Mayers

Five-sixths of all the coal that is mined in the United States is burned, without previous treatment other than screening, for the production of heat and power, so that its value is fixed by its suitability for this purpose. Nevertheless, the characteristics of individual coals that determine their fitness for use in particular pieces of combustion equipment are not yet well known. This condition is due not only to the small extent of our knowledge concerning coal itself, but also to our comparative ignorance of the nature of the combustion process. The following paper is an analysis of the combustion process as it occurs in industrial furnaces, based largely on the results of laboratory research on combustion rates. From this analysis it is possible to determine the characteristics of the fuel that limit the capacity of a given piece of combustion equipment. Limitations imposed by other factors than the attainable speed of combustion will not be considered, since they are subject to a different type of analysis involving the balancing of maintenance costs against fixed charges. In order to observe the relations among the various factors that affect the speed of combustion, representative particles of fuel will be followed through two types of furnaces. A pulverized-coal furnace will be considered first, because the independence of the individual particles facilitates the analysis of the effect of furnace conditions. The second example will be a grate-fired furnace in which ignition of the fuel takes place on the underfeed principle. This includes both underfeed and chain grate stokers, (8)† but does not include hand-fired furnaces and some overfeed stokers. The furnace will be considered to be large enough, the temperature high enough, and enough air provided, to burn the fuel completely, without, for the moment, specifying these quantities more completely. Furnaces Burning Pulverized Coal In a pulverized-coal furnace, the fuel particle is carried, in a stream of air, into the furnace, where it is subjected to radiation from the flame and from the hot walls of the furnace. The increase of particle tempera-

Jan 1, 1936

By Frank H. Riddle, Wilfrid R. Foster

GENERAL treatment of the various minerals of importance in refractories appears in the chapter entitled "Refractories" elsewhere in this volume. The present chapter is restricted to a discussion of minerals of the sillimanite group and brings up to date the excellent information contributed by Prof. Paul F. Kerr to the first edition (1937). Since the appearance of that edition, the status of the group has changed some- what. Kyanite remains the preferred source material for mullite refractories but total consumption of kyanite has increased considerably.85 The exigencies of World War II forced an increased dependence on domestic sources and led to an intensification of the search for higher-grade deposits of kyanite and allied minerals. The first discovery of massive kyanite similar to that of India has been reported from Georgia.37 British East Africa has joined India as a substantial supplier of our imported kyanite, but that from India continues to hold preference.85 During World War II, prices of both domestic and foreign grades reached peaks unparalleled since the earliest years of the use of kyanite and as yet have shown no tendency to return to prewar levels. Topaz, by virtue of the deposit outlined in South Carolina, merits inclusion in the group.20,36,95 Large andalusite deposits, which threaten to rival our one large domestic occurrence, have been found in Russia.69,88 Sillimanite has not yet attained an important position among these useful minerals because of the lack of accessible deposits of high-quality material in adequate supply.37,50,58 Tests by the Bureau of Mines have indicated the possibilities of economically beneficiating low-grade sillimanite and kyanite.105.106,140 Government, university, and industrial

Jan 1, 1949

By Frederic P. Dewey

At the Seventh International Congress of Applied Chemistry I presented a paper,' The Assay and Valuation of Gold-Bullion, in which are briefly mentioned a few illustrations of different methods of sampling gold-bullion, particularly cyanide-bars. Since then I have carried on an extensive investigation upon the sampling of gold-bullion in relation to its effects upon the assay-results, in connection with the statement of accounts between the smaller assay-offices of the United States which purchase gold-bullion and the mints where the purchases are re-deposited. Under the name of gold-bullion are included metals of widely different composition. We may have practically pure metal, 999.75 fine or even more in gold; alloys of .gold and silver with only trifling amounts of base metal; alloys of gold and copper with trifling amounts of other metals; ternary alloys of gold, silver, and copper, or gold, silver, and lead; and most complex alloys of from five to eight or more constituents of ordinary occurrence, besides some of the rarer metals occasi'onally. In any one or all of these classes we may have one or more of the metalloids, which may add to our difficulties. Of course, with metal 999.75 fine in gold there is only slight opportunity for different samples to differ in fineness, but on such fine metal we expect the assays to agree very closely, and the sampling must be done with the utmost care. When possible, dip- or granulation-samples of the molten metal should be taken; but when it is necessary to sample bars, the chief point to guard against is surface-dirt.

Jan 1, 1913

By M. A. Olade

Biotite, magnetite and quartz feldspar separates from rocks around porphyry copper deposits in the Highland Valley have been analyzed for copper, zinc and other related trace and major elements. Results show high copper concentrations in mineral samples close to mineralization, with a strong positive correlation with whole-rock copper contents. Zinc, on the other hand, shows no cleat-cut systematic relationship to mineralization, although there is a subtle decrease in the dues obtained for anomalous biotite samples. Manganese, cobalt and nickel in biotites show similar patterns as zinc. Using a sulfide-selective leach, it is show that the enhanced copper dues in mineral samples proximate to mineralization can be accounted for by the presence of minute inclusions of sulfides. In contrast zinc seems to occur in isomorphous substitution for femic elements, in a form that is leachable by hydrothermal activity. Results also show that copper content of biotite has a positive correlation with the modal proportion of biotites and their iron contents, whereas a negative relationship with manganese is apparent Geochemical contrast for copper between background and anomaly is not better in mineral fractions than whole rocks, consequently the use of minerals as sampling media shows no obvious advantage for mineral exploration purposes in the Highland Valley district.

Jan 9, 1979

By T. PH. D. Egleston

THE origin of gold both in placer deposits and in veins, and especially the origin of nuggets, has been the subject of repeated discussions and investigations, which have been recently brought to my attention by several extremely interesting specimens sent to me for examination, and more especially by the one exhibited at the meeting of the Institute in February, 1880.* In the year 1874 I made some examinations of the hydraulic mines of Califor¬nia, and was very much struck with the distribution of the gold throughout these deep placers, which were almost invariably poor on' the surface, while gradually growing richer towards" the bed¬rock. The constant presence of fossil wood, and the large quantity of organic matter contained even low down in these beds, was also remarkable. Not being satisfied with the various theories advanced to account for the formation of these deposits, I began an investiga¬tion early in the year 1879 on the conditions of solubility of gold and the causes of the loss in working gold ore in a large way: The researches which I have undertaken show that gold must be considered a soluble rather than an insoluble metal, and that the conditions of solution are such as will be found anywhere where gold is likely to occur, and the solution may take place even under the ordinary cir¬cumstances of surface drainage, and may be going on freely even where the presence of gold has never been suspected, and that there are causes enough in nature to produce the solution of the gold in sufficient quantities to account for all the phenomena of both the vein and placer formations. The general theory with regard to the formation of these placer deposits and nuggets has been that they were the result of the de¬struction of pre-existing- vein-matter, which does not accord with the facts as shown in the deep placer deposits. The gold in such case would be distributed in layers of unequal richness throughout * Transactions of the American Institute of Mining Engineers, vol. 8, p. 451.

Jan 1, 1881

By T. Sterry Hunt

THE geognostical relations of the metals and their ores present many problems of great interest, alike for the geologist, the chemist, and the mining engineer. The association with certain rock-formations of characteristic mineral species may help to guide the geologist in the identification of geological horizons, and throw light on the chemical activities which have been especially manifested in certain periods; while it is clear that such relations, if established, must be of great utility to the miner, and especially to the explorer of new regions. In inquiries of this kind, however, it is only by careful observations over wide areas, and by the collocation of a great number of facts, that anything like a safe basis for induction can be attained. The effects of hasty and imperfect generalizations in this field have already in many instances been felt to the prejudice of scientific progress. I come before you to-night, therefore, not to lay down any laws or general principles, but to call your attention to certain facts, many of them doubtless known to you, which have forced themselves on my attention, with regard to the associations of various metallic ores and other useful minerals with different series of stratified rocks, and to ask you to aid the progress of this branch of geognostical inquiry. Your observations in the various regions to which you may be called by your professional duties will enable you to determine how far these associations are mere coincidences, and how far they are chemical and geological constants. The associations here to be noticed concern only those mineral species which occur, either distributed through the strata in such a manner as to show that they are contemporaneous deposits, or occupy rifts or gash-veins in these strata, and may be supposed to have been

Jan 1, 1873

By T. Sterry Hunt

THE geognostical relations of the metals and their ores present many problems of great interest, alike for the geologist, the chemist, and the mining engineer. The association with certain rock-formations of characteristic mineral species may help to guide the geologist in the identification of geological horizons, and throw light on the chemical activities which have been especially manifested in certain periods; while it is clear that such relations, if established, must be of great utility to the miner, and especially to the explorer of new regions. In inquiries of this kind, however, it is only by careful observations over wide areas, and by the collocation of a great number of facts, that anything like a safe basis for induction can be attained. The effects of hasty and imperfect generalizations in this field have already in many instances been felt to the prejudice of scientific progress. I come before you to-night, therefore, not to lay down any laws or general principles, but to call your attention to certain facts, many of them doubtless known to you, which have forced themselves on my attention, with regard to the associations of various metallic ores and other useful minerals with different series of stratified rocks, and to ask you to aid the progress of this branch of geognostical inquiry. Your observations in the various regions to which you may be called by your professional duties will enable you to determine how far these associations are mere coincidences, and how far they are chemical and geological constants. The associations here to be noticed concern only those mineral species which occur, either distributed through the strata in such a manner as to show that they are contemporaneous deposits, or occupy rifts or gash-veins in these strata, and may be supposed to have been

By T. Sterry Hunt

BUT little was known of the coals of Southeastern Ohio until the present survey of the State under Dr. Newberry began its work. The results of the geological investigations of Prof. E. B. Andrews in this region, and of the chemical investigations of Prof. T. G. Wormley, both of which appear in the reports of the survey for 1869 and 1874, and more recent special reports by the former, together with some data for which I am indebted to the kindness of Dr. Newberry, and my own limited observations, have served me for the preparation of the following notice of the coals lying on the western border of the great Appalachian coal-basin in the region drained by the Hocking River and its tributaries, and belonging to the Lower Coal-Measures. Some uncertainty exists as to the place in the succession of the lower coals to be assigned to the seams known and mined in the Hocking Valley. It is the opinion of Prof. Andrews that the inequalities of the original surface were such that we cannot identify in that region the lowest coals known in Northwestern Pennsylvania and the contiguous parts of Ohio, but that we must rather count from above downwards. These conclusions Dr. Newberry is not prepared to accept, and further researches will be necessary before certainty can be attained in this matter. Meanwhile it seems, from a study of its relations to the Pomeroy or Pittsburgh seam, that what is known as the great vein of the Hocking Valley, occupies the horizon of the Upper Freeport coal, E of the Pennsylvania survey, or No. 6 in Dr. Newberry's enumeration, counting from the base. This seam, in the region in question. assumes certain characteristics which, taken in connection with its geographical position, give it a great importance among the coals of the State. The area to be noticed includes the whole or parts of several townships in Perry, Hocking, Vinton, and Athens Counties, lying near the margin of the basin over which the vein in question assumes the character of a dry-burning or splint coal, and has a thickness varying from six to ten and even twelve feet. Its precise limit southward cannot at present be clearly defined, but it has been found as far south as the line of the Marietta and Cincinnati Railroad, with a thickness of six feet, and is mined at various points along the valley of the Hocking River, near Nelsonville, where it attains six or seven feet. To the northward, along the tributaries of this river, Sunday and Monday

Jan 1, 1874

W. ROWLAND Cox,* New York, N. Y. (written discussion?).-The process described by Mr. Malcolmson undoubtedly represents a great stride toward conservation of our natural resources. Without discussing the subject from an economic standpoint, I wish further to emphasize the fundamental principles of the Smith process in order that its economic value may be fully appreciated. The process is essentially a means of producing an ideal fuel, as regards its combustion qualities, by the removal of the so-called volatile matter from the coal, in the form of byproducts, which have value for other purposes far in excess of their fuel value. In other words, coals which contain. large amounts of gas, tar, and ammonia, and are not suitable for domestic or industrial fuel, or for treatment in byproduct coke ovens or gas retorts; because they possess poor coking qualities, can he prepared for commercial use by the. Smith process with a very high degree of efficiency. Much work has been done along this line, both in this country and in Europe, in developing a means of preparing coal, as the economic advantages have long been recognized. To the best of my knowledge, the Smith process is the only one that has proved its commercial adaptability. Distillation of coal at 900° to 1000° F. (480° to 540° C.) yields a large amount of tar and oils. The residue of the distillation, however, is a very friable semi-coke, wholly unsuitable for use as a fuel, unless it can be charged directly into a byproduct gas producer. The problem which confronted the inventor was then to convert this carbon residue into a commercial product, and it is in this step that the Smith process has overcome the obstacles which prevented a number of other methods from becoming commercially practicable.

Jan 10, 1918

By Shawn T. Sorrell, Carl Hrovatic

Land is a precious resource and should be treated as such by all members of our society. The soil covering this earth is only a very thin outer layer, varying in thickness from a few inches to a few feet and covering the rocks and minerals lying beneath the surface. The wise use of this valuable commodity is the responsibility of everyone. Many everyday activities disturb the earth's surface. Examples are highway construction, housing and commercial developments, agriculture, and surface mining. This chapter discusses the relationships of the environment to land as it applies to surface operations ill the coal industry. Mining by surface methods disturbs, for a brief period of time, thousands of acres of land annually. In addition, refuse piles, slurry ponds. abandoned mine structures, unprotected mine openings, and unsightly cleaning plants can also adversely affect land unless properly handled. ACTIVE SURFACE MINING OPERATIONS Mining by surface methods includes rock quarries; sand and gravel pits; huge open pits to extract iron, copper, phosphate, and other ores: and coal mining. Production of coal by surface methods is now approaching 300 million tons annually, amounting to almost 50% of the total coal output. Surface coal mining can be classified into the following four broad categories: Open pit mining is practised where the coal beds are extremely thick, as in some western states, or where the coal beds are sharply pitching, as in the anthracite region of the eastern United States. A typical open pit mine, with coal beds of 10 to 100 ft or more thickness and a relatively small ratio of overburden, generally employs large scraper-loaders to re-

Jan 1, 1973

By J. B. Mackintosh

THE quantitative determination of copper, by means of electro-deposition, offers so many advantages, that it is to be preferred, when properly executed, to all other methods for ease and accuracy. The object of the present paper is to give the results of a number of experiments made during the past few months, and to indicate some sources of error, which must be avoided in order to attain the necessary accuracy. In 1867, C. Luckow, in competition for a prize offered by the directors of the Mansfield Copper Works, submitted the following

Jan 1, 1882