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By A. B. Campbell

The mines in the eastern part of the now active region of the Tri-State zinc district of Missouri, Kansas, and Oklahoma have unusually acid water, which during periods of moderate or no rainfall As used in the mills to replace losses from evaporation, seepage, and tailings disposal. Its use has caused difficulties by corrosion of equipment and by interference with flotation. The growing importance of flotation- Which requires good water, and the increasing troubles caused by the corrosion of the milling equipment have prompted the Mississippi Valley Experiment Station of the United States Bureau of Mines, in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Mo., to investigate the action of the waters on flotation and to undertake to develop means of obviating their harmful effects.

Jan 1, 1932

Research by the National Institute for Occupational Safety and Health (NIOSH) on multiple-seam mining has resulted in two new ground control products. Information Circular (IC) 9495 In some U.S. coalfields, particularly in central Appalachia and the West, most mines are operating above and/or beneath previously mined seams. The effects of multiple-seam interactions can include roof falls, rib spalling, and floor heave. These can seriously threaten the safety of miners and disrupt mining operations. Information Circular (IC) 9495 is a proceedings document containing a variety of papers that summarize recent knowledge about multiple-seam mining. A NIOSH study that analyzed case histories collected from 44 U.S. coal mines is described in detail. The study confirmed that overmining is much more difficult than undermining, and isolated remnant pillars cause more problems than gob-solid boundaries. The study's results were the basis for the Analysis of Multiple-Seam Stability (AMSS) software package. The proceedings also contain two papers describing the LaModel family of software. The original three-dimensional version of LaModel is essential for detailed analyses of complex multiple-seam scenarios. LaM2D implements a simplified, two-dimensional model suitable for quick approximations of the multiple-seam stresses and strains. Three papers in the proceedings focus on case histories. One describes the extensive multiple-seam experience at the Harris No. 1 Mine in West Virginia, a second contains examples of "extreme" multiple-seam mining from the central Appalachian coalfields, and a third describes interactions with regard to longwall mine experiences in Pennsylvania, West Virginia, and Utah. The final paper reports on a numerical modeling study that provided some insight into the mechanics of multiple-seam mining. [ ] AMSS Software Package NIOSH has developed a simple, user-friendly computer program called Analysis of Multiple-Seam Stability (AMSS). AMSS can help mine planners to evaluate each potential multiple-seam interaction and take steps to reduce the risk of ground control failure. AMSS begins by evaluating the pillar design. It first calculates the single-seam pillar stability factor (SF)

Jan 11, 2007

By F. N. Kissell

The machine-mounted continuous respirable dust monitor (MMCRDM) is a fixed-location area sampling device developed for possible use at the working face of an underground coal mine. This device, based on proprietary technology known as the tapered element oscillating microbalance, has evolved over the past eight years through a cooperative effort of the former Bureau of Mines, MSHA, and the Rupprecht & Patashnick Company in Albany, NY. The capability to measure respirable coal mine dust levels on a continuous basis, rather than depending solely on periodic samples obtained from the traditional coal mine dust samplers, has been a goal in the mining industry for nearly two decades. Recently, an extensive series of laboratory and underground tests was conducted by NIOSH with the cooperation of MSHA and coal operators to test the performance of the MMCRDM In preliminary laboratory testing, the MMCRDM seemed to work well. However, in every underground test, when compared to reference samplers placed close to the inlet, the MMCRDM failed to meet the 25% accuracy criterion specified in the contract under which it was developed. Two reasons explain this failure: First, in most tests the bias (the relative discrepancy between the average MMCRDM concentration and the average reference sampler concentration) was too great. Second, the variability of the samplers used for reference comparison was too large. Finally, the underground testing of the MMCRDMs showed that they are quite unreliable at this stage of development. In the majority of mine tests, no more than 10 shifts of data were taken before the MMCRDM failed to function properly. Major breakdowns, requiring the return of the MMCRDM to the factory for repairs, occurred on average every 28 days. To be considered mine-worthy, MMCRDM reliability must be substantially improved. KEYWORDS Dust, coal dust, dust instrumentation, dust sampling, dust monitoring, black lung, pneumoconiosis

By Elaine T. Cullen

Miners, like many skilled blue-collar workers, are not traditional learners. They have not generally been successful in classroom-type settings, preferring to learn on the job in a hands-on environment. U.S. miners are required to have annual safety training, but they rarely view this positively. In fact, it has been called “safety jail” by many of them, who regard it as a time to get a little extra sleep. The challenge then, was to find a way to develop effective safety training for these people, particularly in view of the fact that their work is among the most dangerous of all occupations. Miners are born story tellers. They share “near-miss” stories, stories about master miners they have known, and stories about how things used to be. These stories not only pass along information about what will happen if a miner fails to respect the mining environ-ment, they also instruct listeners in the culture of mining and the values it embraces. Stories, it seems, are a way to get safety messages to miners, especially inexperienced ones, and using older, wiser miners in these stories is an obvious choice. This paper will discuss how the training videos created to get safety messages to miners were developed, how “master miners” and story lines were chosen, and how the resulting videos have been received in the mining industry.

By Ronald P. Hollenbeck

The value of mineral production in Alabama reached a new high of more than $246 million. 4 percent above the previous record established in 1964. New high values were reported for bentonite, portland cement, fire day, kaolin, miscellaneous clay, lime, crushed limestone, crushed marble, mica. salt, and sand and gravel. Among the States, Alabama ranked second in the production of bauxite and scrap mica and third in the production of native asphalt. The mineral industry of Alabama was dominated by the mining and processing of coal and Slone, the manufacturing of cement, and the production of crude petroleum, which together comprised 85 percent of the total value of mineral output, compared with 84 percent in 1964. The iron ore industry continued to decline. Coal production continued to increase, resulting in the State's coal-mining best year since 1948.

Jan 1, 1967

By Dean H. Ambrose

This paper presents the results of a study using computer human modeling to examine machine appendage speed. The objective was to determine the impact of roof bolter machine appendage speed on the likelihood of the operator coming in contact with. A contact means two or more objects intersecting or touching each other, e.g., appendage makes contact with the operator?s hand, arm, head or leg. Incident investigation reports do not usually contain enough information to aid in studying this problem and laboratory experiments with human subjects are also not feasible because of safety and ethical issues. As an alternative, researchers developed a computer model approach as the primary means to gather data. By simulating an operator?s random behavior and machine?s appendage velocity, researchers can study potential hazards of tasks where it is not possible to perform experiments with human subjects. Analysis information is helpful to the mining industry in terms of making recommendations that reduce the likelihood that roof-bolter operators experience injury due to contact with a moving boom. Data analysis of roof bolter simulations show that the virtual-operator?s response time has little effect on the number of contacts experienced. Based on frequency and cross-tabulation, regardless of other variables, contact incidents were always greater when the boom was moving up, were always greater on the palm, and were always greater for the boom part of the machine. Also, regardless of boom speed, the 25th-percentile-sized operators experienced more contacts than did other operator sizes. Furthermore, regardless of boom speed, the 152-cm mine seam experienced more contacts than did other seam heights tested. Results of a survival analytic approach suggest that controlling the boom speed is the most important factor in determining the risk of an operator making contact. Based on the data collected, boom speed greater than 41 cm/s results in a substantial increase in risk to the roof bolter operator and should probably be avoided. At speeds less than or equal to 25 cm/s are associated with a more modest relative risk, which represents an acceptable level of risk. Also, at speeds between 25 and 41 cm/s, there could be a particular boom speed in this range at which a significant inflection point in the relative risk estimates occurs. Based on the results, this issue needs to be addressed by future research.

Jan 1, 2003

By D. Harrington

"Coal—mine explosions are accidents that can and should be prevented. In former years hundreds of lives were lost each year in the United States as a result of such explosions, but after 1932 the numerous precautionary measures adopted had reduced their frequency and severity 75 percent or more until in 1940 several very disastrous explosions marred the good record. Unfortunately, both the number and severity of explosions seem to be tending to increase compared with the relatively good achievement from 1933 to 1940. The requisites for an explosion are ever present in all soft-coal and many hard-coal mines. A certain combination of circumstances, such as a flame or an arc in a cloud of dust or in a body of gas or both may start an explosion at any time. The fact that the frequency and severity of explosions were lowered for 6 or 7 years is no guarantee that such freedom from explosions will continue, as the bad record of 1940 has shown, and underground workers should feel honor bound to exercise the utmost care so that they will not help to bring about the circumstances that will cause an explosion.Although mine operators bear the main responsibility for preventing explosions, miners can do many things to help. As about 9 out of 10 explosions begin at a working face, it is largely within the power of workers to prevent them. All miners should do their part willingly and should not defend a fellow workman from punishment, even from discharge, for disobeying necessary rules, whose disregard may cause the death not only of the safety-rule breaker but also of many of his coworkers.When a miner is careless and is injured some other way than by an explosion he may be the only one to suffer, but if his carelessness causes an explosion he not only endangers his own life but also that of every other man in the mine and possibly the lives of persons outside the mine.Experiments have shown that ignition of as small a quantity as 150 cubic feet of an explosive mixture of methane and air under certain circumstances can start an explosion that will traverse an entire mine. Thus, ignition of an explosive mixture of gas 1 foot down from the roof and 13 feet back from the face of a 12-foot entry might cause a widespread explosion if the right quantity and kind of dust were present. Many persons have ignited much larger quantities of gas without being killed, but they survived only because dust, confinement, and other conditions were not exactly ""right."""

Nov 1, 1940

By W. A. Calhoun, M. M. Fine

"One of the most important wartime activities of the Bureau of Mines was the search for new sources of mineral necessary to the prosecution of the war. Part of that effort was in the form of metallurgical service extended to other government agencies engaged in purchasing and stock piling some of the more critical and strategic materials.Fluorite was one of the materials stock piled by the Metals Reserve Company. The fluorite was usually in the form of coarse metallurgical con¬centrate purchased in the United States and abroad. The material was stock¬piled to insure an adequate reserve of fluorite for the metallurgical industries. The domestic production of metallurgical fluorite containing a minimum effective calcium fluoride content of 55 percent,4/ however, gradually increased until production was at least equal to consumption. The stock-piled metallurgical fluorite, therefore, soon became a surplus commodity.On the other hand, the supply of acid-grade fluorite, containing a minimum of 97.5 percent calcium fluoride and n maximum of 1.5 percent silica,5/ was never entirely adequate. Increased consumption of acid-grade material in the aluminum, petroleum, and chemical industries kept that material on the critical list during the war.Under the circumstances, it was felt that a study of the possibility of producing acid-grade fluorite from the metallurgical stock piles would be of some benefit to the war effort. Consequently, samples of fluorite from several of the Metals Reserve Company stock piles were tested by the Bureau of Mines at the request of the War Production Board.Two groups of samples were submitted for testing. One consisted of metallurgical fluorite purchased from Mexico and stock-piled in the El Paso and Laredo, Texas, stock piles of the Metals Reserve Company. The second group of samples was from the stock piles at Gila, N. Mex.The sample submitted from the El Paso stock pile consisted of about 5,000 pounds of minus 4-inch material. Mineralogically, the sample consisted of fluorite contaminated by calcite, chert, quartz, and small amounts of iron and alumina. Although some of the fluorite was reasonably free from gangue at minus 1-inch, much of it remained locked in sizes as fine as 65-mesh.The Laredo sample was about 5,000 pounds of material from five different piles. The samples from each stock pile, A to E, inclusive, were analyzed separately to determine whether the grade of the material in the piles varied markedly. As there was little difference in the analyses, the samples were combined in proportion to the tonnage represented to make a composite sample for testing. The composite sample consisted of fluorite with small amounts of quartz, calcite, and barite. Most of the fluorite was the dark-colored, opaque variety. A small amount of iron-oxide staining was present, and traces of muscovite, clay, pyrite, and tourmaline were noted. The quartz was present as crystals in vugs, and as finely disseminated grains in the fluorite. The druzy quartz and the calcite were free at minus 10-mesh, but the disseminated grains, some of which were 1 to 15 microns in size, were not entirely free at minus 270-mesh. A petrographic estimate indicated that 65 percent of the silica was locked in the 150- to 200-mesh."

Jun 1, 1946

By J. R. Thoenen

In Progress Report 1,4/ a number of facto mere demonstrated and conclusions drawn from experimental tests and records made during commercial blasting operations at a number of quarries. For example, the tests showed (1) that vibrations received on outcrops were of comparatively

Jan 1, 1938

By R. D. Leitch, W. P. Yant, A. C. Fieldner, R. R. Sayers, S. J. Pearce

"The detection of leakage is a recognized problem in the safe and economic distribution and use of natural gas. Natural gas is practically odorless and therefore lacks he property of indicating significant leakage by the sense of smell, the means most widely used by gas employees and consumers for detecting leaks of the more odorous types of fuel eases. In view of the recognized value of the odor of gas for indicating leakage at the time of occurrence the Bureau of Mines has studied' the possibility of adding small amounts highly odorous substances to types of fuel gas (such as blue water gas and natural gas) that lack warning properties. These studies revealed that the mercaptans were promising substances to accomplish this purpose, not only for odorizing fuel gases but for other purposes° where it was desired to give warning through the sense of smell.Since completing the studies mentioned, the Bureau of Mines jointly with the American Gas Association has conducted further investigations dealing with the use of warning agents for fuel gases. The results of this work will be published later.The Bureau of Mines had been desirous of observing the practical use of ethyl mercaptan for detecting leakage of natural gas, particularly to determine whether the odor would permeate the ground and give indication of lea's in underground pipes. Opportunity for making these observations was recently given by E. A. Munyan, manager, gas department, Union Gas t Electric Co., who requested the bureau's cooperation in making leakage surveys of the company's distributing systems at Franklin and Middletown, Ohio."

Jun 1, 1930

By R. V. Ramani, J. M. Mutmansky, P. C. Luna, V. A. Marple, Honglin He, B. A. Olson

The development of a sampling instrument for the assessment of an underground coal miner’s exposure to airborne respirable coal mine dust on a continuous and real-time basis has been long identified as essential for timely initiation of control actions. A respirable dust dosimeter (RDD) which operates on the principle of increasing pressure across a filter media with increasing dust mass on the filter has been developed by the National Institute for Occupational Safety and Health. Comparisons of the performance of the RDD with an U.S. approved gravimetric respirable dust sampler (GRD) have shown that the RDD may meet the requirements for measuring miners’ exposures on a cumulative, near real-time basis such as mid-shift and end of shift exposures. Recently, the performances of the RDD and GRD were compared by conducting side-by-side area sampling experiments in a controlled experimental environment in the laboratory and in underground coal mines under normal operating conditions. In this paper, the results from the in-mine study are presented and discussed. The experimental design for the in-mine study included two mines in different coal seams in different geographic coal regions. To ensure a wide range of concentrations, the experiments were conducted in a continuous miner section in Mine 1, and a longwall face in Mine 2. Airborne dust sampling was conducted for four different shifts at each mine. In each shift, two samples of different exposure durations were collected from two different locations. Each sample consisted of the readings of three dosimeters and the exposed filters from the three paired GRD samplers. As a result, a total of 96 comparative samples were obtained, 48 for each mine. The data were analyzed for the precision of the RDD and GRD measurements and for the relationships between the differential pressure of the RDD and the mass of dust on the paired GRD filter. The analyses indicate that, on the average, the RDD and the GRD track the airborne respirable dust concentrations well, exhibiting both a high correlation between the two measurements and a reliable predictive relationship of one from the other. Details of the experimental design, data analyses procedures, results, conclusions and recommendations of the underground experiments are presented in this paper.

By Floyd G. Anderson

This report reviews and summarizes information on prevention and suppression of dust in mining, tunneling, and quarrying published in the United States from 1961 through 1967. Unpublished pertinent data developed or assembled by the Bureau of Mines during this period also are included.

Jan 1, 1969

By Nicholas T. Zilka

Mineral resource studies by the Bureau of Mines indicate three areas within the Selway Bitterroot Wilderness have mineral resource potential. Regional studies suggest that a granitic stock on the south side of the Wilderness has high potential for a Climax-type stockwork molybdenum deposit (pl. 1, no. 8); but detailed surface investigations failed to recognize a deposit. The Elk Summit area on the north side of the Wilderness contains subeconomic resources of columbium (niobium)-bearing ilmenite in placers (p1. 1, no. 19). Subeconomic silver-copper-lead resources occur in a vein on the northeast side of the Wilderness at the Clift Mine (pl. 1, no. 2-5). The study area has no known deposits of oil and Haas, coal, geothermal resources, or other energy-related commodities.

Jan 1, 1982

By Richard S. Gaps

The Derby and Alexander Claim, located within the Tunnel Ridge Wilderness Study Area (WSA), has placer gold resources. No lode deposits are known within the area, but lode gold deposits are found within 1 1/2 mi of the WSA. In additon, rock units which contain lode gold deposits north of the WSA are found within the northern portion of the study area. INTRODUCTION The Tunnel Ridge Wilderness Study Area (WSA), CA-030-402, encompasses 4,623 acres of BLM administered public land in Trinity County, California, about 35 mi west-northwest of Redding (fig. 1). Major access to the Tunnel Ridge vicinity is by U.S. Highway 299. Ac-cess to the WSA boundary is by a secondary paved road from Junction City and several light duty dirt and gravel roads (fig. 2). The WSA is on the southwest slope of Weaver Bally Mountain. The topography is rugged with moderate to steep slopes; elevations range from about 1,600 ft to 5,900 ft.

Jan 1, 1983

The combined production value of natural abrasives, which consist of tripoli, special silica stone, garnet, and emery, decreased in 1985. Shipments of processed tripoli increased slightly in quantity but decreased 6% in value, Production of garnet, an abundant iron-aluminum silicate, increased 24% in quantity and 20% in value. There was an 11% increase in the quantity and a 7% increase in the value of refined garnet shipped when compared with 1984 shipments, a new record high. Production of crude special silica stone decreased 10% in quantity and 14% in value, and shipments of finished special silica stone products decreased 85% in quantity and 68% in value. Both the quantity and value of special silica stone finished products sold or used were the lowest since 1981. Production of emery, an impure aluminum oxide, decreased 56% in quantity and 61 % in value of product mined and shipped. [ ]

Jan 1, 1987

West Virginia ranks second in the nation in coal production, surpassed only by Wyoming, and usually accounts for 15 to 20percent of the nation's total annual production. Cod occurs in seams of minable thickness in all but nine of the state's 55 counties. There are two coal- producing regions, the northern field and the southern field. West Virginia coal is mined by both underground and surface methods. Underground mines in West Virginia account for a major portion of its coal production. Surface mines are generally contour operations and, especially in the southern field, are in steep slope areas, with slopes greater than 20 degrees. Many of the surface mines remove multiple seams. Recoverable reserves in West Virginia total in excess of 55 billion tons of bituminous coal. West Virginia's regulatory program was conditionally approved on January 19, 198 1. Its Abandoned Mine Land Program was approved February 23,198 1, with emergency authority granted on August 26,1988.

Jan 1, 1992

By F. W. Smith

To determine whether preheating coals before carbonization would improve the coking properties of the coals, particularly the weaker coking coals, 3 coals, 1 each from Illinois, Kentucky, and Pennsylvania, and a blend of the Illinois with a Pocahontas coal were preheated before testing for coking properties in the Bureau's BM-AGA pilot oven. The effects of preheating on the chemical and physical proper-ties of the coals and on the yields of carbonization products and strength of the coke produced from the preheated coals were determined, as were also the effects of bulk density, gaseous atmosphere, and residence time during preheating. Most benefit from preheating was found with weaker or oxidized coking coals, whereas the more strongly coking coals and blends showed little effect. Direct charging of preheated coal to the coke oven without cooling gave better coke, increased yield of tar, and decreased yield of gas. INTRODUCTION Although 94 percent of today's coal production comes from fields east of the Mississippi, the Eastern States have only about one-third of the Nation's recoverable reserves. West Virginia, which now produces more than any other State, has much smaller reserves than Utah, Colorado, and Wyoming.5/ However, the manufacture of iron and steel in Western States, which has increased greatly since World War I, is handicapped by the scarcity of high-grade coking coals, such as are plentiful in the Appalachian region. Unless a practical method of improving the cokemaking property of local coals is developed, ferrous metallurgical industries in the West must continue to use inferior coking coals and to pay high shipping charges for better coals.

Jan 1, 1958

By WILLIAM F. McMURRAY, James O. Lewis

The Bureau of Mines is investigating the technology of petroleum and its products, the investigation including well-drilling methods and the transportation, treatment, and utilization of petroleum and of natural gas, with especial reference to the prevention of waste and to increased efficiencyin the development of oil and gas resources in land belonging to or controlled by the Government. During. the winter of 1912-13 the enormous waste of the gas encountered while drilling for oil in the Cushing field, Oklahoma, called forth protests from various sources, and appeal was made to the President of the United States and to the Secretary of the Interior in behalf of the landowner and of the public in general. The facts were wanted regarding the amount of waste and the technical conditions that were responsible for practices causing it. An investigation was ordered and conducted under the direct supervision of the late J. A. Holmes, the first Director of the Bureau of Mines. R. S.Blatchley was sent to investigate the amount of waste going on in the Mid-Continent flelds.s In the latter part of March, 1913, J. A. Pollard and A. G. Heggem were sent to Oklahoma to study well-drilling methods with reference to the waste of gas from wells on Indian lands and to suggest means of preventing the waste of natural gas on such lands. Pollard and Heggem decided that the mud-laden fluid process, which had been used successfully for some years in Texas, Louisiana, and California was the method that would meet the situation most efficiently and economically. The method was accordingly demonstrated in Oklahoma. In 1914 Congress provided for the employment of six oil and gas inspectors to supervise oil and gas mining operations on lands of the Five Civilized Tribes in Oklahoma and to conduct investigations with a view to the prevention of waste. Positions under this appropriation have been held by William F. McMurray, James O. Lewis, Harry D. Aggers, Ralph R. "Weed,George W. McPherson, James C. Fowler, Louis W. Courtney, and Carl H. Beal, the technical work of these men being directed "byW. A. Williams, chief of the petroleum division, Bureau of Mines. After careful and impartial investigation of conditions in Oklahoma, these men also decided that the mud-laden fluid process was the one best adapted to prevent further wastes. In 1915 laws were passed by the State of Oklahoma that provide for the conservation of natural gas and oil, authority being given to the corporation commission to make rules and regulations and to employ agents to enforce them. After hearings and investigations, the corporation commission reached substantially the same conclusions as the Federal agents regarding the importance of the wastes and the best methods of conserving the gas. Technical Papers 66a and 68b were published by the Bureau of Mines in December, 1913, and January, 1914, respectively. Technical Paper 66 deals with the mud-laden fluid process in general and No. 68 with its application in Oklahoma. The interest aroused by these publications has been so widespread that within two years the first editions have been practically exhausted. Rather than reprint these publications, it has been considered advisable to replace them with the present report, which includes the results of more recent investigations. The methods of using the mud-laden fluid are an outgrowth of the rotary drilling system, which was developed in Texas and later employed in Louisiana and California. Some of the principles of the use of mud fluid had been observed and used to a limited extent for a long time in cable-tool drilling. So far as known it was first used successfully with a circulator and cable tools in the Coalinga field, California, in 1906,Harry D. Aggers, one of the contributors to this paper, working on the well. The part of the Bureau of Mines has been to call attention to its merits and to demonstrate its practical use in fields like those of the Mid-Continent.

Jan 1, 1916

By David E. Kaslow

In sampling dust laden air by drawing the medium into an inlet, some larger particles fail to follow the air and a true sample is not obtained. Inertia prevents particles from accelerating with the air as well as from turning sharp bends; also the particles' weight causes them to fall relative to the air. An analytic solution to the sampling efficiency calculation by Levin gives particle paths and sampling efficiencies for various particle sizes when the inlet can be treated as a point sink. However, the flow field in the neighborhood of an aspirating tube is quite different from a point sink flow. Employing Levin's solution in the outer field, trajectories in actual flow fields have been calculated by computer to locate the critical trajectories separating the entering particles I paths from those paths where the particles hit the tube wall or escape. Sampling efficiencies are presented in terms of 3 variables--a dimensionless particle size coefficient, a dimensionless orifice size coefficient and the tube orientation--for the no-wind case. Over most of the range of sampling conditions, the Stokes drag law can be used and dependence on the variable--particle Reynolds number--can be ignored. A procedure for achieving maximum efficiency in design of a sampler is proposed. Whether these results apply when typical room-sized eddies constitute the ?calm air? environment is not known.

Jan 1, 1974

By Oliver C. Ralston

The minerals that enter welding-rod coatings and fluxes are the main subject of this report. Few mineral producers know just what minerals and what grades and quantities of minerals are required by the welding trade, and it is for their information that this report has been prepared. The various methods of welding are discussed extensively enough to inform this type of audience. Specialists in welding probably will find little on welding that is of value to them, but they may learn something more about the minerals or mineral products that they use. The authors did not find it easy to prepare this publication, and any needed corrections will be welcomed. Regarding welding, research, Jenks4/ 1 points out that while the process of welding in simple in operation, the phenomena attending its use are extremely complicated, and the efficient and safe use of welding requires an understanding thereof. Although the fluxes and the coatings used have solved many problems, many other problems require the joint effort of the whole industry; therefore, it is hoped that this report will be found of practical value.

Jan 1, 1940