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By T. A. Rickard

The dictionary defines 'jargon' as "barbarous or debased language". This description does not suffice. Quiller-Couch has said, it is "a kind of writing which, from a superficial likeness, commonly passes for prose in these days, and by lazy folk is commonly written for prose, yet actually is not prose at all ". The two main vices of jargon, he says, are "that it uses circumlocution rather than short straight speech", like the Babu who reported his mother's death by saying: "Regret to inform you, the hand that rocked the cradle has kicked the bucket ". Its other chief' vice is that "it habitually chooses vague woolly abstract nouns rather than concrete ones", like the newspaper statement; "He was conveyed to his place of residence in an intoxicated condition", instead of saying, "He was carried home drunk ". Jargon is "an infirmity of speech", it is not journalese, but akin to it. "Like respect- ability in Chicago, jargo4 stalks unchecked in our midst" and renders much technical writing ridiculous. It deals in periphrasis instead of going straight to the point, it loves the abstract rather than the concrete, it dabbles in words of sound rather than of meaning. Avoid it, despise it., if you purpose earnestly to write well. "III literature as in life he makes himself felt who not only calls 4 spade a spade but has the pluck to double spades and re-double." * Jargon is rampant in technical publications. Catalogues and other advertisements are conspicuous offenders, but with these the critic is not concerned, except in so far as such 'write-

Jan 1, 1931

By E. A. Nesbitt

THE important permanent-magnet alloys 15 years ago contained carbon and depended upon it for their permanent- magnet properties. In recent years great, advances have been made in a number of new alloys substantially free of carbon. These include Remalloy,l an alloy of iron, cobalt, and molybdenum, the various iron- nickel-aluminum alloys of the Mishima2 type, and the more recent Alnico V3 in which the best properties are developed by heat-treating in a magnetic field. The Mishima and the Alnico types of alloys are very brittle and after casting must be ground to size. This article describes a permanent-magnet material4 that can be machined as cast, and when handled with some care can be .rolled to thin sheet and drawn to fine wire. Optimum magnetic properties are developed by a simple heat- treatment, and at this time the ductility A of the alloy disappears. If the cast alloy is heat-treated without cold-working the magnetic energy product is about 1.0 X 106. This material is called Vicalloy I (pronounced vicalloy, V for vanadium, I for iron, and C for cobalt). When the alloy is first hot-worked and then considerably reduced in area by cold-swaging, drawing or grooved rolling, it is found that after heat-treatment the magnetic energy product measured in the direction of previous extension can be increased to 2.0 to 3.5 X l06. These higher values have been obtained only after reductions in area of 75 to 95 per cent, and since the material hardens considerably during working, the reduction ordinarily can be accomplished only in fine wires, although larger sizes can be reduced by the use of powerful machinery. When the material has been cold- worked in such a manner as to improve its energy product substantially, it is called Vicalloy II. Commercial use of Vicalloy has been made in the recording of speech. Tape 0.002 by 0.050 in. has been found superior in quality to all others tried, and is now used in the Western Electric Mirrorphone In a variety of forms Vicalloy I or II is useful in many laboratory instruments, and in experiments in which the sizes and shapes required cannot be obtained with the other more brittle permanent-magnet materials. In 1936, during a study of other age- hardening magnetic systems, it occurred to the author that some of the iron-cobalt-vanadium alloys might be suitable for permanent magnets. The proportions of iron, cobalt, and vanadium were varied and a range of alloys of particular interest was found, as shown by the indicated area in Fig. I. The limits of this range of com- position are 30 to 52 per cent iron, 36 to 62 per cent cobalt, and 4 to 16 per cent vanadium. The compositions indicated by points outside this area were also tested. PREPARATION AND PROPERTIES OF VICALLY I The alloys were usually cast in graphite molds into bars ¾ in. in diameter and

Jan 1, 1946

By Reinhardt Thiessen

During the last few years a type of coal called "splint coal" has been brought to the attention of the United States Bureau of Mines, through numerous inquiries concerning its nature. Until recent years it appears to have escaped general notice. The term "splint coal" is of long standing, but was thought to be merely another expression applied by the miner to coal having certain minor characteristics. When closely examined, however, these coals were found to form a marked and distinct type, with distinctive characteristics that cannot be mistaken. Because splint coals produce a hot cheerful flame, possess a clean blocklike nature, and have a high volatile content, they have lately become much valued for domestic, gas-producer and steaming purposes, and have attracted considerable attention. Mattkohle For many years we have heard from the Germans about Mattkohle and Streifenkohle, in contradistinction to Glanzkohle, but have not realized that they were of a different type from the coals with which we were most familiar. This type of coal was first brought to general notice by Muck, in 1881, who gave a good description of it.' Because this coal is often intercalated with thin sheets of brightly shining cod, Schondorff, who was more familiar with the Saar coals, called it Streifernkohle. This term was later used by Muck also. Still later Potoné² used this term exclusively for the whole group in contradistinction to a class called Glanzkohle, and considered these coals to be composed alternately of Humuskohle and Faulkohle or Mattkohle (Pig. 20). Not knowing the nature of the German coals and not realizing that the term Streifenkohle was applied to a distinct class of coal, the terms of its components as used by Potonié and others were translated to "bright Coal" and "dull coal" and applied to the components of our

Jan 1, 1930

By FRANK RIEBERS

IN DISCUSSING the selection of a geophysical method, much of what the writer will say is applicable to any of the various methods and to their use in prospecting, whether for oil or for other minerals. Specifically, the writer's subject is the problem, particularly pressing on the Pacific Coast, of checking the rising cost of the discovery of new fields by the proper employment of geophysical methods. Table I was prepared from statistics published by the California State Milling Bureau. The writer selected five of the largest a:ld most active companies operating in California, segregated the number of wild-

Jan 1, 1930

By H. M. Chance

Discussion of the paper of H. M. Chance, Bi-Monthly Bulletin, No. 23, September, 190S, pp. 791-808. CHARLES CATLETT, Staunton,Va. (communication to the Secretary *):-Mr. Chance's suggestions that the brown hematite ores of the Potsdam formation are due to the alteration in place of iron sulphide, and that their extension may reasonably be expected to contain valuable deposits of unaltered sulphide, are interesting; but the facts marshaled by him are too limited to justify more than the hope that they may serve as a commercial source of sulphur. It is true that these deposits have been the source of large amounts of iron-ore; and it. is common, as stated by him, for the mining operations to extend to a shallow depth only; but this is largely due to the fact that the surface-material represents an accumulation from the breaking down and collection of the ore which formerly reached a much higher level. With, increasing depth comes a decreasing thickness of valuable material. This is especially appreciated by a glance at Mr. Chance's drawings. This is the reason why so many disappointments have resulted when these ores have been followed to greater depths. Even if the ore is largely derived from oxidation in place, it is impossible to ignore the great number of concretionary forms, as well as those showing the evidence of secondary solution and deposition now taking place, such, for instance, as the part replacements of fragments of quartzite derived from the underlying beds. Concretionary form does not necessarily mean long transportation, and may be a variation of material in place; but commonly it is an evidence of collection, and tends to imply that more or less concentration has taken place. This fact would also argue against an equally extensive develop¬-

Nov 1, 1908

By W. Rostoker, R. P. Elliott, B. W. Levinger

Phase equilibria in the Ti-Mn-Mo system have been investigated in the composition range 100 to 60 pct Ti and in the temperature range 550 to 1150°C. Three out of ten isothermal sections are presented as well as seven vertical sections, projections of the beta space and the surface of incipient melting. A STUDY of the system Ti-Mn-Mo was undertaken as part of a program to aid in the development of titanium-base phase equilibrium diagrams of potential technical importance to alloy development. The scope of the investigation included the composition range 100 to 60 wt pct Ti (all compositions refer to weight percentages) and the temperature range 550" to 1150°C. A surface of incipient melting was constructed from measurements of a large number of alloys. In the binary system Ti-Mo,' the high temperature modification of titanium generally spoken of as the p phase is stabilized to successively lower temperatures with increasing alloy content. There are no known intermediate phases, and complete miscibility exists between body-centered cubic titanium and molybdenum. The u solid solution is limited to less than 0.8 pct Mo at temperatures between 885" and 600°C. An equilibrium diagram for the binary system Ti-Mn has been published.' Manganese behaves as a p stabilizer but undergoes a eutectoid transformation at about 20 pct Mn and 550°C to a plus an intermediate phase. The structure of this phase has been found to be isomorphous with the a phase FeCr." Accordingly, the phase is assigned the formula TiMn, although its actual location on the composition scale has not been determined and may well be not exactly at the equiatomic composition. In disagreement with ref. 2, the origin of the TiMn phase has been shown' to be a peritectoid transformation at a temperature between 900" and 1000°C. A second intermediate phase occurs at the atomic proportions TiMn,. The structure of this phase was originally established by Wallbaum" as having a hexagonal lattice (C 14 type, 12 atoms per unit cell) isomorphous with MgZn,. In this work, the structure determination was confirmed and lattice parameters determined to be: a = 4.815 kX, c - 7.901 kX. Because of the extensive range of the P phase, the ternary system was suited to the determination of the phase boundaries by the parametric method of Andersen and Jette." During the course of the investigation, this method was found applicable only to the P/a+P boundaries but not to P/P+ compound boundaries. Metallographic methods were used alternatively for delineating these phase boundaries. Preparation and Treatment of Alloys Over 70 alloys were prepared for the study of this system. Ten gram alloy buttons were arc melted in a nonconsumable electrode furnace using inert atmosphere protection, and a water cooled copper crucible. The construction and operation of this type of melting unit has been described.' To insure complete solution of alloy additions, especially molybdenum, the buttons were remelted alternately on top or bottom as many as five times. This was accomplished by a suitable mechanism for "flipping" the ingots over. It was very difficult to obtain homogeneous melts in the region of less than 75 pct Ti because of the very high melting point of molybdenum and Ti-Mo master alloys and the comparatively low boiling point of manganese. Thus, the arc conditions for insuring complete solution of molybdenum were incompatible with the prevention of heavy losses of

Jan 1, 1955

By Hallet R. Robbins

KOREA, the ancient " Hermit Kingdom," is a peninsula jutting out from the coast of eastern Asia. By the natives it is called " Chosen," which, translated, means " Land of the Morning Calm." It lies between the Yellow sea and the Sea of Japan. On the north it is separated from Manchuria and the Russian province of Primorsk by the Yalu and Tiumen rivers ; on the south the Korean straits interpose a rough voyage of 120 miles to the nearest point in Japan. The entire country is situated between the parallels of 34° and 42° N. latitude. The surface of the country is made up of successive ranges of unglaciated mountains, separated by narrow, fertile, and more or less densely populated, valleys. Through all the obscure centuries of its history, Korea has succeeded in maintaining a monastic seclusion, over which, from time immemorial until the late Chino-Japanese war in 1894, China exercised a shadowy sovereignty. Although Korea had been forced into slight foreign contact previously, her first foreign treaty was signed with Japan in 1876. Under the restraining guardianship of China, the Japanese treaty bore but insignificant innovations for Korea; but when, in 1883, a treaty was made with the United States, the first of the western nations, a decade after the American gunboats, under Commodore Rodgers and Lieutenant Schley, forced their way up the Salee river, shooting daylight through the ancient walls and fastnesses, Korea awoke from her sleep of 4,000 years. The Korean peninsula suddenly became the arena where rival nations' enterprises and individuals met in fiercest conflict. Out of this struggle grew two singularly successful American

Jan 7, 1908

By I. L. Barker

ALTHOUGH valuable information has been pub-lished on the important problems of slag losses with which every copper metallurgist has to contend, a great deal of money is still being wasted in copper smelters all over the world, through metal being irretrievably lost in reverberatory slags. When smelting a relatively low-grade pyritic concentrate together with a proportion of direct-smelting oxi- dized ore, as is done in Oroya, slag volumes are of necessity high, and even a relatively clean slag, say of 0.5 pct Cu, means a loss of almost 4 pct of all the copper charged, or over $1,000,000 annually at present output and prices. While it is known that such losses can often be reduced by allowing the slag time to settle, with or without addition of a reducing agent such as coal or pyrite, the facilities for such treatment are not always available in a plant of old design working to capacity under severe space limitations. Nor is it easy under such conditions to run large scale tests which may endanger the smooth flow of production for considerable periods without yielding

Jan 1, 1958

By A. W. Brune

Conventional methods of calculating the duty cycle of a mine hoist are awkward in that a number of items must be remembered or that they must be collected together in order to have all the calculated data in one place. A more convenient way is to tabulate all factors involved, permitting a ready evaluation of the problem. An example illustrates the convenience of such a table for either of two types of drums, cylindrical and conical. Assume the following conditions: The hoisting depth is 600 ft. Balanced hoisting is used. The weights of empty skip and ore are 6000 lbs and 12,000 lbs, respectively. Production is 3600 tons per shift. Net hoisting time per shift is six hours with a rest period of eight sec, top and bottom, per trip. Acceleration and retardation are each six sec. The diameter of the drum is seven ft; its face is four ft. The sheave has the same diameter. The equivalent effective weight of the drum reduced to rope center is 15,400 lbs. The weight of each sheave is 2100 lbs. 1 The rope is 1 1/4-in. improved plow steel weighing 2.50 lb per ft.

Jan 9, 1961

By A. O. HAYES

SYSTEMATIC methods of ore-finding are looked to the more as increasing production requires greater supplies of raw materials. Unrelenting search for new sources of supply is necessary, and all the skill of science must be displayed both in methods of discovering and recovering the minerals necessary to the demands of present-day life. To this end most national governments have some sort of a geo- logical survey and there is a growing understanding of the desirability for cooperation between federal and state or provincial organizations and also financial assistance, from state and private universities, mining companies, railroads and manufacturers. Such surveys are now being directed by well trained geologists selected from federal, state and university departments. Large-scale maps are being prepared and better geo- logical interpretation made, more thorough chemical and physical examinations are being made and original search is fostered, with the result that successful prospecting is better directed, new mining regions are more likely to be discovered, and the life of. old camps lengthened.

Jan 1, 1931

By J. T. Ryan

POISONOUS, irritating, or explosive gases are found in almost every industry, and manufacturers of gas masks are called upon to provide gas mask protection for a great variety of conditions, such as operators in horseradish factories, fumigators of homes and ocean liners, and men engaged in the manufacture of tetra-ethyl-lead, the new motor fuel. The modern type of gas mask and respirator, to provide protection against all such industrial gases, is an outgrowth of the gas mask developed during the World War to protect the soldiers against the poisonous war gases. So far, it has been possible to develop ample mask protection from all known noxious gases and fumes present in atmospheres encountered in mines, metallurgical works, and chemical and other industries, so long as there is sufficient oxygen present to support the flame of an oil lamp. The most important development of the gas mask was in providing protection against carbon monoxide- which is the noxious gas that mining men are most concerned with and, in fact, is the noxious gas that man is most frequently exposed to. This paper will be con- fined largely to the discussion of masks for underground use in metal mines. Gases that contaminate the normal air in mines can be divided into two classes: those that are given off normally by the workings, and those that are produced in mine operation.

Jan 1, 1926

By JOHN R. SUMAN

COMMENCEMENT exercises this year have a peculiar significance because the graduating students are entering upon their life's work at the most critical time in the history of the United States. We are engaged in a great struggle the outcome of which is none too clear even to the best informed students of international affairs. We are starting late in a vicious world conflict where it is generally recognized that our adversaries have distinct superiority over us in armament on the land, on the sea, and in the air. We have the gigantic task of building up our armed forces and armament and at the same time supplying our allies with equipment which they must have. We can do this job if we are given sufficient time, but there is a possibility that the war will be over before we are ready. Few realize the seriousness of this situation. If this fight is to be won-and we dare not try to visualize the future of this country if it is lost-all dissension and bickering between Congress, capital, labor, and agriculture must cease. When and where voluntary co-operation proves inadequate for the successful conduct of the war effort, laws must be enacted or strengthened to achieve our purpose.

Jan 1, 1942

By John Treweek

FOR many years the Homestake Mining Co. has devoted serious attention to the elimination of accidents, and ground is steadily being gained in this direction. In accident prevention work it is line-plunging with perfect teamwork and not the spectacular forward pass that brings progress toward the goal. In both surface plants and under- ground workings we regard "good housekeeping" as a first requisite for safety as well as efficiency. Under this term are included all types of safety guards and protective devices as well as cleanliness and orderliness it working places. Perhaps the most important factor in safety work is to arouse and maintain employee interest. The general morale and contentment of employees is of particular importance.

Jan 1, 1938

By Willis H. Carrier

PARTICULAR interest in the ventilation of deep mines, especially those in South Africa, has been created by a very complete system of cooling of the world's deepest mine, the Turf shaft of the Robinson Deep in Johannesburg. The writer visited this mine in January, 1936, and again in 1937. During these visits and subsequently, a considerable part of the theory involved in rock cooling in tunnels was developed and this has been checked by practical observations of the rates of rock cooling made within mines. The purpose of this paper is to set forth the method of attack of the mine problem. The cooling or air conditioning of mines by the use of mechanical refrigeration was not wholly new 1-5 when the Robinson Deep installation was made. The first mine to be cooled was the Morro Velho mine, in Brazil. The first installation in this mine was put into operation in December 1920, the refrigerant being ammonia.5 The surface cooling gave considerable benefit but it proved inadequate as greater depths were reached, therefore in 1929 two centrifugal refrigerating machines were installed at the 6000-ft. level. These were used in conjunction with the surface cooling system to furnish additional cooling at the lower levels. This later installation used Carrene as a refrigerant. This nonflammable refrigerant, having a boiling point of 104º at sea level, insured reasonable safety, since all parts of the machine operated at subatmospheric pressure. Very favorable reports have been received on the effectiveness of this installation, but no recent data are available. An interesting feature of that plant is that the condenser water is cooled by spraying it into the exhaust air from the mine at the base of the ventilation upcast, which permits the water to be cooled within a few degrees of the wet-bulb temperature of the air entering the upcast, and the only water that has to be supplied for condensing purposes is that lost by evaporation, or about 0.5 per cent of the volume circulating through the condenser. This plan affords an ideal means for the removal of the heat load from the refrigerating system, and of course also from the mine itself. In many mines, however, especially those in South Africa, there is no

Jan 1, 1938

Discussion of the paper of Robert R. Abbott, presented at the New York Meeting, October, 1913, and printed in Bulletin No. 82, October, 1913, pp. 2389 to 2400. ALBERT SAUVEUR, Cambridge, Mass.:-Mr. Abbott has certainly made a strenuous effort to ascertain the influence of the various elements on the absorption of carbon by steel-a subject of great importance to those dealing with the case hardening of that metal. Because of the extensive and careful character of Mr. Abbott's experiments, one is all the more disappointed that his results, as he himself recognizes, are not more satisfactory; for, indeed they leave us just about where we were,-still entertaining uncertain views in regard to the carbon-absorbing power of various alloy steels. It might be asked whether Mr. Abbott's method of estimating the amount of carbon absorbed-namely, by weighing the specimens before and after the carburizing treatment-was the best one to select. Are not serious sources of error. inherent to such procedure because of the difficulty of satisfactorily removing the earburizing material attached to the specimen ? The method of least squares has certainly failed to solve the problem satisfactorily. By manipulating Mr. Abbott's results in a different manner I have obtained the following expression: P = 100 - 50 C - 7 Ni + 20 Cr, in which P represents the carbon-absorbing power; C, the percentage of carbon; Ni, that of nickel; and Cr, that of chromium. It is assumed that the carbon-absorbing power of pure iron, or what might be called its carburizability, is represented by 100. Applying the formula, for instance, to a steel containing 0.15 per cent. C, 3 per cent. nickel, and 0.50 per cent. chromium, its carbon-absorbing power would be 100-50X0.15-7X3+20X0.50=81.50; that is, 81.50 per cent. of the carbon-absorbing power of pure iron.

Jan 12, 1913

By Oliver Bowles

THE ADVERSE CONDITIONS that have gripped industry during recent years have to some extent submerged technical developments under the more pressing demands of economic problems. Progressive operators, nevertheless, have given attention to improvements in processes and equipment even when sales were at a low ebb. The array of facts relating to technical advancement here presented, although doubtless incomplete, is sufficient to indicate that the spirit of inquiry and research has not been quenched by adversity. During the latter part of 1933 a new element has focused interest more fully on improved methods of quarrying, mining, and preparation of nonmetallic minerals. Codes established under the NRA have fixed minimum wages, reduced working hours, and tended to establish selling prices .on a basis of reasonable profit. Labor adjustments will in many instances increase the cost of production, and stabilization of selling prices will tend to emphasize quality and service rather than price as sales arguments. These new conditions point to a growing necessity for improving technique in the interest of reducing cost of production and improving the quality of products. Thus, technology is linked with economics more firmly than ever.

Jan 1, 1934

By J. B. STEWART

T HE position of each hole of any series of holes was carefully located by the surveyor, plotted in plan and elevation, and numbers assigned to them. The second series was staggered halfway between the first and so on for each succeeding series. Two and a, half to three months was frequently required to grout a series of holes calculated to insure safety for sinking a distance of 10 meters or say 33 ft. Naturally the initial operation called for drilling and grouting two series of holes but thereafter each sinking campaign required only one series of holes as shown in Fig. 8. The pump handling about 75 gal. per minute corresponds to 46 tons of grout or 6 tons cement delivered as a fair over-all average for the 24 hours. Thus 600 to 800 tons of cement was used for a single section of 33 ft. depth of shaft. One campaign used nearly 1100 tons of cement. Some holes were effectually sealed with as low as 30 tons, while many required 60, and some 80 to 90 tons.

Jan 1, 1926

By Harlowe Hardinge

AN extensive recent trip throughout the mining districts of the Southwest, Central West, an Northwest,' reveals a numbes of interesting conditions that have influenced operators, in both large and small mills, to modify their flow sheets insofar as they pertain to crushing and grinding. The changes made and planned for the future should be of interest. It is interesting to note when traveling through the country, how ideas change and practice is modified, and it is rather amusing to see how milling methods seem to run, more or less, in cycles. New ideas and developments are brought about which run through the industry and are taken up by many of the best and most well informed operators. Some of them will change, sooner or later, back to their old practice; for, like everything .else, what will work well in one place will not necessarily be suited to another. On the other hand, it is often difficult to establish. other practices known to be of value, owing to the natural resistance to make a change, but on the whole, the western mill men seem to be more alive to possible benefits of various modifications than any other engineers with whom I have come in contact in all parts of the world. Mill men in other parts of the world always keep in con- tact with what is being done in the western part of the United States, but it does not necessarily follow that those in the western part of the United States are always right. Some of these changes that have been made and afterward abandoned will be referred to later.

Jan 1, 1929

By Guillermo Mariaca, Jorge Muñoz Reyer

As far as technology is concerned there has been no development in Bolivia during the year 1936, because the country, just emerging from the war with Paraguay, is only beginning to rebuild its economic foundations. Great steps, however, are being taken in order to secure a rapid and sound development of its oil resources, as follows: 1. The new Petroleum Law, which contemplates the problem of proration and conservation of natural resources, prohibiting the wasteful use of gas, and regulating the number of wells, their spacing and the permissible output per well, for each particular pool according to the conditions prevailing therein. 2. The creation of an official entity with the object of developing and exploiting a large petroliferous area. This entity has been called Yacimientos Petroliferos Fiscales Bolivianos (Y.P.F.B.), and the region assigned to it is all the sub-andean zone, which is approximately one hundred miles wide and borders the eastern part of the Oriental Andean range, from Argentine to Peru. It is said that drilling will be started immediately in various localities. At the present time a wide geological survey of part of the area is being made in order to find out which regions offer the best possibilities of commercial development. Y.P.F.B. has been authorized by the Government to draw up contracts with private companies for the exploitation of limited zones. Production The only company that has been producing in the country in 1936 is the Standard Oil Company of Bolivia, and only from two of its fields: Camiri and Sanandita. New wells were not drilled. During the first nine months of the year 12,762,958 liters (80,275 bbl.) was produced, 34,985 bbl. from the Camiri field and 45,290 bbl. from the Sanandita field. Reports for October, November and December are not yet available. The total for the year 1935 was 25,978,737 liters (163,388 bbl.).

Jan 1, 1937

T.P. 1958 D. H. DAVIS.*-Mr. Carris has ably pre¬sented the problems of coal preparation, particularly those brought about as the result of increased mechanical loading. Many mines are now crushing the run-of¬-mine raw coal through 12 or 15 in. immediately after it is dumped from the mine car and before it is handled by conveyors. At certain mines the removal of large slate mechanically has been solved by the installation of scalping screens consisting of bars or rails set at spacing of 12 to 15 in. on the top deck of the main raw-coal sizing screen. At the plants where these are in use, the plus 12 or I5-in. raw material contains 60 per cent or more free rock or slate, so that it is easier to pick coal than to pick rock. After the screening at 12 or 15 in. is accomplished, the oversize material is diverted to one side of the shaker, where a picker allows the refuse to pass off the shaker into a chute and guides the coal back onto the shaker. After the large rock has been removed, it is then advisable to reduce the size of rock by crushing before putting it onto a conveyor. A great saving in picking labor has been made by the use of such scalping screens, which in addition has maintained the plant capacity when handling a dirtier feed. The great increase in percentage of coal under 1/4 or 3/8 in., coupled with a greatly increased percentage of free impurities in this size, is the most serious problem that has been brought about by mechaniced loading. Many plants that formerly prepared good quality 1/4-in. to o or 3/8-in. to 0 slack by air¬cleaning are faced with installing facilities for wet-cleaning mechanical and heat-drying and water clarification. The change to wet prepa¬ration of fines usually affects the marketing problems for many coal companies. There will also be problems involving wastage of fine solids and stream pollution. Much work will be necessary for improvements in present practice. Pneumatic and electrostatic methods for cleaning fine coal should receive consider¬able attention in an attempt to avoid wet¬cleaning of fines. The preparation supervisor and the plant personnel should not be satisfied merely to run the cleaning-plant machinery and assume that the job will be done for them. Coal is a heterogeneous substance and in many instances is constantly changing. This is more true when full-seam methods are in use. Only persons trained to observe closely and make the necessary changes in plant operation will be able to solve the many problems that will be imposed on the preparation plants. The plants will require skillful and observant operating men. With full-seam mining methods, seams of roof coal will often be mined. Under the former mining systems these strata were not mined and frequently they contain a high per¬centage of bony and banded partings. The mining of this coal will greatly alter the washability and specific gravity characteristics of the feed to the plant. Often the percentage of 1.40 to 1.60 sp. gr. increased from 3.5 to 7.5 per cent, or nearly a 1.0 per cent increase in the ash content of the 1.60 sp. gr. float coal. Thus the cleaning problem is much more difficult, and it is unlikely the same ash content of cleaned coal can be produced as before without a decrease in recovery or the produc¬tion of a "middlings" product. Mr. Carris had this in mind when he said "The quality of the

Jan 1, 1946