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Papers in Classes A-Metal Mining, B-Milling and Concentration, H-Industrial Minerals, and I-Mining Geology are distributed in MINING TECHNOLOGY, which is issued every other month. Papers in Classes C-Iron and Steel Division, D-Nonferrous Metallurgy and E-Institute of Metals Division are distributed in METALS TECHNOLOGY, which is issued twice quarterly. Papers in Class G-Petroleum Division are distributed in PETROLEUM TECHNOLOGY, which is issued every other month. TECHNICAL PUBLICATIONS in Classes F-Coal Division, J--Mineral Industry Education Division, K¬-Mining Administration, and 1-Geophysics, are issued as separate pamphlets. Contributions are papers that when printed or mimeographed are available but only on request.

Jan 1, 1944

Papers published by the Institute are issued in a variety of forms MINING TECHNOLOGY, issued every other month, contains the TECHNICAL PUBLICATIONS on Metal Mining, Minerals Beneficiation (milling and concentration), Industrial Minerals (nonmetallic) and Mining Geology, Mining Administration, and Geophysics papers relating to Metal Mining (A, B, H, I, K, L ) METALS TECHNOLOGY, issued eight times a year, contains the TECHNICAL PUBLICATIONS of the Iron and Steel Division and the Institute of Metals Division, and once or twice during the year those on Non-ferrous Metallurgy (reduction and refining of nonferrous metals) (C, E, and D ) PETROLEUM TECHNOLOGY, issued every other month, contains the TECHNICAL PUBLICATIONS of the Petroleum Division, together with Geophysics papers relating to -the finding of Petroleum (G, L ) COAL TECHNOLOGY, issued four times a year, contains the TECHNICAL PUBLICATIONS of the Coal Division (F ) MINERAL INDUSTRY EDUCATION DIVISION papers appear in a TECHNOLOGY according to classification of subject matter DISCUSSIONS appear in the respective TECHNOLOGY as available MINING AND METALLURGY is the monthly magazine, which contains papers of general interest and news of the membership

Jan 1, 1952

By JAMES H. McGRAW

P UBLZCLTY and engineers do not mix. In the very words of my subject, there is an apparent contradiction. In the past, publicity has been abhorrent to the engineer. It seems to be true that the engineer, because of his training or his background, has developed a state of mind which omits publicity. At any rate he has done a poor publicity job for himself. The average engineer is self-conscious; he ought to be class-conscious. If T should ask the men in this hall to get up one by one and tell who they are and what they have done, there would be an instinctive reaction in the mind of each man-a feeling that this was out of place. If I should ask each man to get up and tell something about his neighbor, I should find that each neighbor, once he got acquainted with the man next to him and understood what he was doing, would be as human and as generous-hearted in telling about his brother engineer as is any professional man.

Jan 1, 1920

The Pueblo Viejo Mine, a 7, 250 mtpd (8,000 stpd) gold-silver cyanidation plant built by Rosario Dominicana S. A., was described in Volume I of this monograph. At the time of writing that volume, Pueblo Viejo had not yet gone on-stream and operating data or costs could not be presented. Since that time this information has been obtained and several interesting modifications and an expansion have been made to the plant. Because Pueblo Viejo is the largest open-pit gold mine in the world and one of the world's leading gold-silver operations with production of approximately 31 kg (1,000 oz) gold and 125 to 155 kg (4,000 to 5, 000 oz) silver per day, the authors have updated the previous data and flow sheet. The Dominican Government, which held a 4670 interest in Rosario Dominicana S. A., completed purchase of the mine to gain full control in 1979. Rosario Resources will continue to manage the mine, at least until the end of 1980. Gold was produced at Pueblo Viejo almost 500 years ago with initial production in the year 1505. Rosario Resources became interested in the property in 1969 and found surface oxidation had rendered the upper portion of the ore body amenable to direct cyanide treatment. The treatment of the underlying gold-bearing sulfide zone is still undergoing metallurgical studies. The ore is considered to be a laterite; and because there appeared to be few boulders in the ore zone, only a 400 m (16 in. ) square grizzly was initially installed ahead of the mills when the plant went on-stream in late 1974 at a design capacity of 7,250 mtpd (8,000 stpd). Operation also proved the ore to be harder than was originally anticipated. During 1967 a 1. 25 m by 1. 5 m (48 in. by 60 in. ) jaw crusher was installed to -feed the 1, 000 mt (1, 100 st) mill bin. Minus 200 mm (8 in.) crushed ore is fed directly to two 5.5 m by 1. 8 m (18 ft by 6 ft) semi-autogenous mills re-powered with 750 km (1,000 hp) motors and 50 mm (2 in.) grates. Each mill product is screened at 13 mm (1 /2 in.) by a vibrating screen. Screen oversize from each mill is combined on a single return belt equipped with a magnetic head pulley for grinding ball removal. The non-magnetic oversize is then split into two fractions for return to the primary mills. Originally, a minus 6 mm (1/4 in ) product was made on each screen and fed to a 300 kw (400 hp) 2.6 m by 3. 7 m (8-1/2 ft by 12 ft) regrind mill. During a plant expansion in 1978, an intermediate mill of 746 kw (1,000 hp) was installed to operate in open circuit on the combined primary mill

Jan 1, 1981

By E. W. Davis

ABOUT a year ago several carloads of magnetite ore from New York state were sent to the Mines Experiment Station at the University of Minnesota for grinding and concentration tests. The flowsheet used minus ½ -in. ore as feed to a 3 by 3-ft. overflow cylindrical ball mill operating at 37 r.p.m. in closed ciruit with a vibrating screen. The screen oversize was returned to the mill for further grinding and the screen undersize was concentrated magnetically. Several different screens, between 8 and 35 mesh, were used and it was desired to determine the capacity of the ball mill operating in closed circuit with each screen. From earlier tests using this flowsheet and equipment, it was known that when comparatively coarse screens were used it was necessary to increase the grinding dilution in the mill beyond that ordinarily used when grinding in closed circuit with classifiers. It was also known that after the circulating load had passed about zoo per cent of the original feed it tended to increase rapidly in amount, and grinding conditions appeared to become unstable. These conditions may be peculiar to this small ball mill but they were very marked in this series of tests. If conditions were not right, the mill would suddenly "go dead," and it was found desirable to operate so that the occasional rattle of balls against the lining of the mill could be detected. As the test proceeded, it was found that the cure for almost any difficulty that developed in the grinding circuit was to add more water to the mill feed. To begin with, the mill was operated at pulp densities of from 60 to 65 per cent solids but gradually it was found that with higher dilutions grinding conditions were more stable and the ball-mill power per ton of screen undersize decreased. Actually, the most satisfactory operating conditions were secured with a pulp density of about 40 per cent solids. The ore was hard but it was possible to grind ½ in. feed so that all would pass an 8-mesh screen with a power expenditure in the ball mill of less than 2 1/2 kw-hr. per ton and with a circulating load of less than 50 per cent. With so high a dilution in the feed to the mill, it was feared that steel wear would be very high. However, the mill was not noisy, and in order to find exactly the grinding conditions, a special test was made at the end of the main series of tests. After the mill had been in operation for several hours and grinding conditions had become balanced, the power to all the equipment was shut off at a given signal. The ball mill made about one revolution after the power was turned off, and just as soon as the mill stopped, a spout was placed at the discharge trunnion and all of the pulp that flowed out of the mill was caught in tanks. The manhole in the mill was then opened and the whole mill charge dumped into other tanks. Both of these products were weighed, dried, and weighed again. The balls were screened out and weighed, and the dry solids were sized. In this way it was possible to determine the nature of the pulp and the ore within the mill under actual grinding conditions.

Jan 1, 1945

By Werner Goldsmith

This discussion is confined to the first section of Professor Clark's paper entitled 'Elastic and Nonelastic Waves' and its application to wave propagation in rocks. Some published results by other investigators concerning measured decay of peak strain and variation of pulse duration with travel distance are cited, but the principal subject of this section is a detailed mathematical analysis of spherical (and, to a lesser extent, of plane) wave propagation in various homogeneous, isotropic media. The materials selected include an elastic substance, a Voigt and a 'modified' Voigt solid-the latter incorporating the assumption of a constant loss factor (defined here as the product of frequency and the ratio of the imaginary to the real part of the shear modulus)-and a solid friction model. While other possible representations of a solid continuum model are mentioned, corresponding solutions are not presented. The pulse inputs considered comprise exponential decay, a unit step, and steady- state sinusoidal excitation: the process of conversion from one solution to another in the operational plane is indicated. The basic problem relative to the analysis of wave propagation in rocks concerns the specification of the appropriate material behavior, since the equations of motion for a given geometry of the source and medium are well established. In principle, the required information can be deduced from two types of measurement: 1) field observations of underground explosions or seismic disturbances, and 2) laboratory tests on small samples of the pertinent rock. However, in practice both types of approaches are beset with difficulties and subject to valid criticism. Field observations must be carried out under relatively uncontrolled conditions, including, in general, a lack of knowledge of the precise arrangement of the medium, stratification, faulting. inhomogeneities, etc. Specimens investigated in the laboratory can not represent the environment found

Jan 1, 1967

LIST OF REFERENCES COMPILED BY ENGINEERING SOCIETIES LIBRARY FUEL POSSIBILITIES IN STEEL MAKING. Iron Age, November 6, 1913, p. 1056-1059. Paper read before the American Iron and Steel Institute, by William Whigham. The author discusses the use of pulverized coal as a fuel for open-hearth furnaces. IMPROVED PULVERIZED FUEL FEED DEVICE. Iron Age, November 6, 1913, p. 1024. Brief description of the Dunn apparatus, especially intended for cement kilns, but used also in the nodulizing of iron ore. WIDER UTILIZATION OF PULVERIZED COAL, H. R. Barnhurst. Iron Age, October 23, 1913, p. 906-908. Part of discussion of paper by James Lord on The Use of Pulverized Fuel in Metallurgical Furnaces, read before the Engineers' Society of Western Pennsylvania. POWDERED COAL FOR OPEN HEARTH FURNACES. Iron Age, October 16, 1913, p. 855. Abstract from the "Coal and Coke Operator." USE OF PULVERIZED COAL AS A FUEL FOR BOILERS, R. C. Carpenter. Sibley Journal of Engineering, December 1913, p. 85. COAL-DUST FIRED BOILER. Indian Engineering, November 29, 1913, p. 301. PROGRESS IN FUEL UTILIZATION. Mining and Scientific Press, October 25, 1913, p. 638. BUFFALO GRAIN-ELEVATOR DUST EXPLOSION. Engineering News, July 31, 1913, p. 223-24. Reprinted in the National Fire Protection Association Quarterly, October, 1913, p. 149-151. Mention is made of the danger of explosions in connection with the burning of powdered coal. POWDERED FUEL AND EXPLOSIONS. Railway Age Gazette, July 18, 1913, p. 53-84. Letter by W. D. Wood. USE OF PULVERIZED COAL IN METALLURGICAL FURNACES, James Lord. Engineers' Society of Western Pennsylvania, Proc., October, 1913, p. 363-371; discussion, p. 371-417. With bibliography.

Jan 3, 1914

By E. S. Bardwell

DURING the period extending from May, 1922, to September, 1923, the copper-refining furnaces of the Great Falls Reduction Department of the Anaconda Copper Mining Co. at Great Falls, Mont., were operated exclusively with pulverized coal as fuel. The installation was made first as an experiment. It proved successful from the start and was abandoned solely because fuel oil from the Sunburst field became available at a price sufficiently low to make its use desirable from an economic standpoint. The equipment required for pulverized coal has, however, been kept intact and is available for immediate use should the oil supply fail. Inasmuch as pulverized coal had been used on two large reverberatory smelting furnaces and was, at the time we were considering its application to the copper-refining furnaces, being used on the Wedge furnaces roasting zinc concentrate for the electrolytic zinc plant, we were equipped with a coal-pulverizing plant of ample capacity to supply pulverized coal for the furnace refinery. The only problem was to devise suitable means for transporting pulverized coal from the pulverizer plant, located in the smelter building, to the refinery about 1000 ft. distant and about 150 ft. above the level of the pulverizer plant. When studying this installation, it should be borne in mind that the layout represents an adaptation suited to the existing conditions at this particular plant. The installation was entirely satisfactory and uniformly dependable but might be modified to advantage from an operating point of view if an entirely new installation were being planned.

Jan 9, 1925

A bibliography of the use of pulverized coal for the years 1917 and 1918 has been compiled by the Library for the Institute. It comprises three typewritten sheets. Copies may be obtained by those interested at $2 per copy.

Jan 5, 1919

By John C. Nigro

The Bureau of Mines is investigating the use of pulverized coal as a fuel for iron ore pelletizing to determine its effectiveness as a substitute for natural gas and oil. Experimental data illustrates the application of both a gun-type suspension burner and a cyclonic-type slagging burner to a grate-kiln pelletizing unit. In addition, experimentation with a cyclonic fired external combustion chamber for possible adaptation to a shaft or straight grate pelletizing furnace is discussed. The tests were conducted in the Bureau of Mines Twin Cities Metallurgy Research Center's pilot plant with high rank bituminous coals from Kentucky and Colorado and low rank subbituminous coals and lignites from Montana, Wyoming and North Dakota. Although combustion was excellent with the suspension burner, the low ash fusibility temperature coals and lignites caused some kiln ringing and accretion buildup in the grate kiln transfer section which were not encountered when firing with the high ash fusibility temperature Kentucky coal. Pellet contamination by coal ash was not deemed substantial. Problems with the cyclonic burner and external refractory combustion chamber centered around (a) maintaining complete combustion of the coal within the burner, (b) molten slag attack on the lower refractory chamber resulting in erosion of the lining and increased slag viscosities, and (c) freeze-up of the slag tap hole.

Jan 1, 1977

By James A. Barr

PUMICE and pumice are varieties of volcanic ejecta formed from lavas of the more silicic types. Chemical analyses of pumice, pumicite and perlite, from which synthetic pumice is now produced, will generally fall within the limits 65 to 75 pct silica, 9 to 20 pct alumina, less than 8 pct combined alkalies (sodium and potassium oxides), less than 3 pct calcium and magnesium oxide, less than 3 pct iron oxide, with smaller amounts of manganese, titanium, phosphorus and other oxides. Perlite is characterized chemically by having, in addition to the percentages of oxides given above, as high as 6 pct combined water. PROPERTIES Pumice is a natural silicic foam glass produced by volcanic eruptions. The molten glass foam, upon rapid cooling, trapped the steam and volcanic gases that caused it to remain extremely porous and vesicular in structure. Pumice is found in the form of large lumps several cubic feet in volume and also in grains only a few millimeters in diameter. Chemically, pumicite is of the same range of composition as pumice. The distinction between pumice and pumicite is one of particle size; the coarser materials are pumice; the fine particles, an appreciable percentage of which is in the range of 100 to 325-mesh or finer, are pumicite. If the erupting volcano ejects a silicic lava containing much gas and water vapor, the sudden release of pressure tends to free the gas. The viscosity of the lava, its rate of cooling and the amount of gas evolved, all have part in determining the degree of expansion of the glassy particles and the fineness of the vesicle. If the lava is of the correct viscosity and there is not too much gas, a pumice may be formed. Large amounts of gas may cause complete disruption into pumicite.30 In 1916, Barbour gave the name "pumicite" to the volcanic ash of Nebraska and since then the name has been widely used in industrial circles for the finer-grained commercial varieties. The glass of pumice and pumicite is transparent and colorless. It

Jan 1, 1949

By N. V. Peterson, R. S. Mason

Pumice, pumicite, and cinders are all products of explosive volcanic eruptions. Pumice and pumicite are produced by the violent expansion of dissolved gases in a viscous silicic lava such as rhyolite or dacite. Pumice is a light-colored, cellular, almost frothy rock made up of glass-walled bubble casts. It may occur as coherent, massive blocks composed of highly vesicular glassy lava in either a flow or vent filling, or it may be more or less fragmented by violent eruption. Pumicite has the same origin, chemical composition, and glassy structure as pumice differing only in particle size. Particles less than 4 mm in diam are designated pumicite. Pumice is usually found relatively close to the vent from which it was erupted while pumicite may be carried by winds for great distances before settling as an accumulation of fine-grained ash or tuffaceous sediment. Volcanic cinders are the reddish to black vesicular fragments that pile up during explosive eruptions of volcanoes of basaltic composition. Most deposits of cinders occur as cones or mounds of stratified fragments that range in size from a fraction of an inch to several inches in diameter. Individual cones or mounds of cinders may be several hundreds of feet in diameter and as much as 500 ft high. Properties The properties that make pumice and pumicite useful in industrial applications include: low-bulk density, good heat and sound insulating properties, and excellent abrasive capability. Cinders, even though less cellular and somewhat heavier, also have a variety of industrial uses. Uses The main use of pumice and cinders continues to be in the construction industry as road-surfacing material, railroad ballast, building block aggregate, in lightweight structural concrete, and as plaster aggregate. Both pumice and pumicite continue to be used as abrasives for polishing glass, metal, leather, stone, and wood. Some scouring powders and soaps also contain pumicite. Minor uses include fillers, absorbents, carriers for insecticides, catalyst carriers, filters, and soil conditioners. Pumicite is also used in sizable quantities as a pozzolanic additive in monolithic concrete where it increases the workability, strength, and durability of the concrete and reduces the heat of hydration. Volcanic cinders are generally denser and more coarsely cellular than most pumice. Markets for cinders include aggregate for road construction and surfacing and in lightweight concretes, particularly blocks. Some producers having access to both pumice and cinders offer a variety of blends of the two materials to block manufacturers. Most pumice deposits are unconsolidated and usually have a minimum of overburden. Mining is by open pit and can be easily carried out with conventional loading equipment. Sometimes air-drying precedes hauling to a crushing and screening plant which yields the size product desired. Multiple bins at railroad hauling facilities permit blending if desired. Pumice for abrasive use may require more sophisticated processing by fine grinding and air classification before being bagged for market. Block pumice in economic quantity and quality is limited to a few geologically young

Jan 1, 1975

By N. V. Peterson, R. S. Mason

The violent explosion of Mount St. Helens in the state of Washington on May 18, 1980 showered volcanic ash over vast areas of the Northwest. It was another eruptive episode in a long history of similar occurrences in the region, which extends from Canada to California and reaches several hundred miles inland from the Pacific Ocean. Pumice, pumicite, and cinders are products of explosive volcanic eruptions. Pumice and pumicite are produced by the violent expansion of dissolved gases in a viscous silicic lava such as rhyolite or dacite. Scoria is the mafic counterpart of pumice. Pumice is a light-colored, cellular, almost frothy rock made up of glass-walled bubble casts. It may occur as coherent, massive blocks composed of highly vesicular glassy lava in either a flow or vent filling, or it may be more or less fragmented by violent eruption. Pumicite, the diminutive of pumice, has the same origin, chemical composition, and glassy structure, differing only in particle size. Particles less than 0.16 in. in diam are designated pumicite. Pumice usually is found relatively close to the vent from which it was expelled, while pumicite may be carried by winds for great distances before settling as an accumulation of fine-grained ash or tuffaceous sediment. Mount St. Helens lofted an estimated 5 billion cu yd of ash and pumicite. The volcano, unlike most of the High Cascade peaks, is composed largely of dacitic material with only minor amounts of andesite and basalt. Volcanic cinders are the reddish to black vesicular fragments which pile up during explosive eruptions of volcanoes of basaltic composition. Most cinder deposits occur as cones or mounds of stratified fragments ranging from a fraction of an inch to several inches in diameter. Individual cones or mounds may be several hundred feet in diameter and up to 500 ft high. Properties and Uses Low bulk density, good heat and sound insulating properties, and excellent abrasive capabilities make pumice and pumicite useful in industrial applications. Cinders, though less cellular and somewhat heavier, also have a variety of industrial uses. The main use of pumice and cinders continues to be in the construction industry as road-surfacing material, railroad ballast, and building block aggregate. Pumicite is used in sizable quantities as a pozzolanic additive to monolithic concrete where it increases workability, strength, and durability of the concrete and reduces the heat of hydration. Volcanic cinders generally are denser and more coarsely cellular than most pumice. Markets for cinders include aggregate for road construction and surfacing and use in lightweight concretes, particularly blocks. Some producers having access to both pumice and cinders offer a variety of blends of the two materials to block manufacturers. Table I lists the principal applications of industrial pumice. Tables 2 and 3 show US sales and uses of volcanic products. Most pumice deposits are unconsolidated and usually have a minimum of overburden. Mining is by open pit and can be easily carried out with conventional loading equipment. Sometimes air drying precedes hauling to a crushing and screening plant which yields the size product desired. Multiple bins at railroad hauling facilities permit blending if desired. Pumice for abrasive use may require more sophisticated processing by fine grinding and air classification before being bagged for market.

Jan 1, 1983

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Jan 1, 1938

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Jan 1, 1938

By John Birkinbine

IN all metallurgical processes and mining operations, water is an element which receives attention from the management ; and provision is required either for a means of supply, or for the disposal of accumulation. In many works the quantity of water to be furnished is sufficiently large to place the item of water supply of equal importance to the reception of material or disposition of product ; and the means to be employed receive, or should receive, the most careful investigation. There are exceptional cases where mines or quarries possess a natural drainage, but a large majority of the useful ores and the fuels delved from the earth are obtained from workings in which water accumulates and must be removed. Often the quantity to be

Jan 1, 1877

By Julian Nardi

Pumping solids through a pipeline is not new but until very recently other means of transportation were cheaper. Many proposed pipelines for transporting solids, while technically feasible, have not been attractive enough to warrant the financial risk involved. In some instances, the difference in transportation cost was negligible. In others, the threat of pipeline competition resulted in a slashing of rates on existing transportation to the point where a pipeline could no longer be justified. In others, a competitive product was cheaper. FIRST IN PLACERS The earliest record of solids being transported in a pipe was in the late 1850s in California placer mines. Water under pressure was used to force gold-bearing gravel up through a pipe, from 30 to as much as 55 ft, to a point where it could be discharged into a flume or sluice.

Jan 9, 1959

By Wilbur T. Stuart

To assist the mining industry in attacking problems of water control, the U. S. Geological Survey has begun a program of research in mining hydrology. In certain fundamental respects water control is similar to development of water supplies from wells or to the drainage of agricultural lands, as many of the tools developed in recent years for quantitative ground-water problems are applicable, with modification, to mine-water problems. In 1952 a 30-day pumping test conducted jointly by the Eureka Corp. Ltd. and the Defense Minerals Exploration Agency provided an opportunity to gain knowledge concerning water movements around a flooded mine shaft. The methods of analyzing the data may be used as a guide for the evaluation of similar problems elsewhere.

Jan 2, 1955

By M. L. Brashears, R. G. Slayback

The host dolomite of the Pine Point lead-zinc ore is a prolific ground-water aquifer that occurs locally under watertable and artesian conditions. Mining schedules and severe climate require rapid and thorough dewatering of open pits. Pumping-test methods, common to ground-water supply studies, were applied to dewatering design for a model ore pit in 1968. Procedures for testing and design at other ore bodies were established and have been carried out successfully by mine personnel. At the inception of ground-water studies, parts of ore bodies were below prevailing ground-water levels by 35 to more than 150 ft. Movement of ground water through the coarsely recrystallized dolomite occurs largely through fractures and solution openings. Because the overburden deposits consist mainly of glacial till, it is estimated that the recharge to the aquifer is about 25% of the 13-in. annual precipitation. Natural groundwater flow is northeastward toward Great Slave Lake. Background data included extensive diamond drill hole logs and cores and static level data for a number of ore pits. An ore pit, known as N-42, that required 40 ft of dewatering was selected for the initial application of the pumping-test method. Production wells, cased with 14in. pipe, were drilled to a depth of 300 ft on the rim of the ore pit. A suitable pattern of observation wells was obtained by lining 21/8-in. diamond drill holes with perforated electrical conduit. A two-stage pumping test

Jan 1, 1973

A knowledge of the principles of punctuation is essential to effective and intelligible writing, for the ease and pleasure of the reader, and even his understanding, may depend upon the choice and the placing of punctuation marks. To 'punctuate' is to mark with stops or points; the word comes from the medieval Latin punctuare (punctuatus), which in turn is derived from the Latin punctum, a point. The purpose of punctuation is to show the manner in which the writing is to be understood; to indicate the relations between parts of a sentence and between successive sentences. To some extent "it does for the eye what vocal stress does for the ear", but especially it marks logical relations. Some punctuation marks, such as those indicating admiration, exclamation, and interrogation, are rhetorical as well as grammatical, but most of the common ones are logical or grammatical. My discussion will be confined to grammatical punctuation in ordinary writing. "The problem of punctuation in text matter", as George Summey * says, "is to employ words, points, and paragraph breaks in such a way as to achieve at the same time clearness, proper distribution of emphasis, and the desired kind of movement." The criticism of the punctuation of a sentence or of a group of sentences is not final until the context, within the paragraph, is read. A paragraph is a sentence or a group of' sentences forming an independent unit of the composition; it represents a unit of thought. A multiplicity of paragraphs produces a choppy effect; on the other hand, paragraphs of excessive length are tiresome, because the belaboring of one unit of thought wearies the reader. The aim should be to

Jan 1, 1931