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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 J. W. Thompson

That the governor is hereby authorized to appoint a commission of seven persons, to be known as the industrial accidents commission-two of whom shall be employers of labor, two of whom shall be employees in either mines or industrial establishments of this Commonwealth, or duly accredited representatives thereof, two of whom shall be learned in the law, and one of whom shall be a person skilled and experienced in making investigations-to inquire into the causes and results of industrial accidents in the mines, mills, factories, stores, and upon the railroads, street railways, ships, wharves, and in all industrial establishments, and in all other places where men, women, and children are employed in manual labor in this Commonwealth; to study the most advanced methods for safe-guarding against these accidents; to inquire into the subject of fair compensation for those who are injured in these accidents, and for the families of those who shall be killed as a result thereof; and to study the operation and effect of the Workmen's Compensation Law of 1913. SEC. 2. The chairman of said co~mission shall be designated by the governor, and the person named on said commission as a skilled and experienced investigator shall be the secretary of the commission, The commission shall have power to employ such legal counsel and other officers and employees as it may deem necessary to properly perform its duties. SEC. 3. The secretary of said commission shall receive an annual salary of $2,400 and his actual necessary expenses; and the other members of the commission shall receive no compensation for their services, but shall be allowed their actual traveling and other necessary expenses. The salaries of any other persons employed by the commission shall be fixed by it.

Jan 1, 1920

By S. K. Kawatra

It is common in coal-cleaning operations to produce a fine waste stream which contains a considerable amount of coal, but which is not economical to recover both because it is mixed with large amounts of difficult-to-remove clay slimes, and because the fines are often heavily oxidized. Conventional froth flotation machines cannot produce an acceptable product from such material in a single stage of flotation, and even flotation columns often have difficulty cleaning this type of feed. A new type of flotation column was designed specifically to deal with these problems, and was installed and tested in a coal-cleaning plant in Ohio. The feed coal contained 39.8% ash as fine clay, and 2.83% total sulfur, and was 80% passing 176 micrometers. The coal was a thickener product which had oxidized for some time, and was very difficult to float. However, using the new column it was possible to recover up to 85% of the calorific value in a product containing less than 11% ash, and up to 60% of the calorific value in a product of less that 8% ash. The bulk of the pyritic sulfur was rejected from the coal as well. Multistage flotation tests showed that the flotation column was able, in a single stage, to produce the best froth flotation product that it was possible to recover from this coal.

Jan 1, 1994

By Chee Theng

"Getting minerals out of ores is messy, but mineral processors learn to have fun with it. Celebrating the innate joys of the industry was the theme of this year’s Colorado MPD Conference. At the same time, attendees dug deeper for insights into problems that continue to dog the community, including tailings dam crises, water resource challenges, and a dwindling number of academics to teach and train the workforce (see box).Tailings dam crisesMatt Fuller of Tierra Group International Ltd. brought some of the audience to tears with his impassioned talk on “The Infamous Legacy of Upstream Tailings Dams,” which won the conference’s Lou Cope award for best paper. The talk was especially poignant coming on the heels of the January tailings dam failure in Vale S.A.’s Córrego do Feijão iron ore mine in Brazil, the latest in a series of catastrophic dam failures over the past decade that includes the Fundão dam failure in 2015.Noting that the two dams share a common characteristic — both are upstream tailing dams — Fuller explained the three basic dam construction methods and why certain upstream tailing dams are susceptible to failure (Fig. 1). The downstream, centerline and upstream methods denote the direction the centerline of the dam crest moves with each successive raise in elevation of the dam. With the downstream dam, the foundation for future raises is essentially the same as that of the starter dam, he explained. With the centerline dam, half of the dam is constructed on the same foundation as the starter dam, and with the upstream dam, each successive raise is built out over the top of the tailings.“Downstream dams are expensive to build because each successive raise is bigger, so the sustaining capex to build them keeps growing,” Fuller said. Many decades ago, mine owners realized they could construct a starter dam, put their tailings through a hydrocyclone, generate a coarse sand fraction and stack the sand over the top of the tailings to build the next raise. “Then, there is no sustaining capex, it all comes out of operations,” Fuller added. The footprint is smaller, and it is a favorable means of retaining the tailings."

Jul 1, 2019

By William Ives

My presentation is from the viewpoint of the industrial mineral geologist, which is a relatively rare breed. Very few geologists become involved with industrial minerals for two reasons, I think: (1) Much of the industry utilizing non-metallic minerals has developed without the use of geologists in the begin¬ning and many of the management people, who generally derive from the processing plant supervision, tend to take raw materials for granted; and (2) non-metallic minerals are a very insignificant part of the curriculum of virtually all colleges granting a geology degree. One learns about the geology of industrial minerals by working with it. This "on-the-job-training" is probably best because it brings the geologist into close quarters with the production people and the production process. And the industrial minerals field has a distinctiveness when compared with the petroleum or metal mining field in that each deposit can yield a material differing in some aspect from that in any other or within the same deposit. The petroleum from a well in a given field will be similar to that from any other well, but a limestone on one side of a hill can differ signifi¬cantly in elemental composition, calcinability, soundness, specific gravity, or some other factor from the same ledge on the other side of the hill. This characteristic of almost certain variability creates problems sooner or later and provides for much of the employment of industrial mineral geologists. My job seen from the viewpoint of management is "Find us some rock we can extract and process at a profit." The industrial non-metallic geologist has much the same problems and approach as a detective. I do not mean the TV variety with the big mouths and the unfailing knack of spotting the wanted criminal immediately in a city of ten million people. Any real detective will tell you it takes leg-work, knowhow, and persistence to make a case. The same is true for the geologist who finds rock which can be quarried at a profit. I am responsible for finding raw materials for a company which manufactures portland cement and

Jan 1, 1977

By J. W. Griffith

"The mines in the Bancroft area of southeastern Ontario, a few kilometres west of the town of Bancroft, are in Faraday and Cardiff Townships. Three companies, known as Canadian Dyno Mines Limited, Macassa Gold Mines Limited (Bicroft Division) and Madawaska Mines Limited (formerly Faraday Uranium Mines Limited), with plants capable of handling a total of 4,()()() tons (3,629 tonnes) of ore a day, were at one time in production. A fourth company, Greyhawk Uranium Mines Limited, operated a small mine whose ore was shipped for custom treatment to the nearby Faraday mill. Canadian Dyno Mines Limited ceased operations in June 1960. In June 1963 the Bicroft Mine was closed and a year later Faraday closed because of contract completion. But in 1975, Faraday (now called Madawaska) was re-opened but closed again in 1982. During 1959, the peak year, these four mines produced an estimated 1,100 tons (998 tonnes) of uranium precipitates, which represented nearly 7 per cent of Canada's output for that year(Fig. 1).The deposits occur in pegmatitic granite dykes in a region of high-grade metamorphic and metasomatic rocks. Uranium distribution is usually controlled by the distribution of mafic minerals, particularly hematite and magnetite, and by late fractures. The best visual indicators for uranium concentration are hematite staining in the pegmatite, followed by the amount of mafic inclusions or crystals. The Bancroft area orebodies are the only known deposits of the general pegmatitic class in Canada that contained economic deposits of uranium. The principal radioactive minerals are uraninite and uranothorite. By comparison with many other pegmatitic occurrences, some of the ore bodies are unusually large, persistent in depth and relatively rich in uranium minerals. At the end of 1981, total ore reserves were estimated at 1,500,00 short tons (1,360, 000 tonnes) averaging 0.11 % U3O8."

Jan 1, 1986

By Raymond Henn

Yes we have also used some however, again because of the nature of the maintenance window where we have that two hour (at best) window every night and due to the numerous other crews that are wanting to get in to do the other types of maintenance activities, we don't know if we are going to be getting into that same area from one night to the next. So even with the dormancy additives that one can add to cementitious grouts (that are good up to 72 hours) we don't know if we are going to get back in to the same locations from one week to the next. That's why I use the term "the forgiving nature of the acrylamide". It allows us to ream out the hole allowing us to use the exact same hole without having to re-drill a new hole. The program started in 1997 and we have a budget between labor/materials and equipment of 4.5 million dollars on a year to year basis. For the next few years that is going to come down drastically because the program is going to be more of an ongoing maintenance program. The program started in 1997 and we have a budget between labor/materials and equipment of 4.5 million dollars on a year to year basis. For the next few years that is going to come down drastically because the program is going to be more of an ongoing maintenance program. Up to the end of 2001 we were just over 1.7 million liters of between AV100 and AV118 grout. Of that, approximately just under 200,000 was AV100 and the remaining balance was AV118.

Feb 10, 2003

By Kozo Takeda, Arashi Shimano

"Dry Jet Mixing (DJM) method as the representative deep mixing technique has been demonstrating best practice on ground mitigation works coping with complicated soil condition and limited site space. This technique plays an important role in many projects to stabilize soft ground involving troubles like sliding failure, settlement, bearing capacity etc. Serious disasters caused larger earthquakes make great demand on the application of deep soil mixing these days. Special design and alignment of deep soil mixing has been established against to liquefaction and serious failure due to liquefaction. In this paper, representative example of liquefaction mitigation by DJM method is summarized. The paper also present result of surveillance of sites installed DJM col umns after attack by Tohoku Pacific Ocean Earthquake. Performance of DJM columns suffered the earthquake is demonstrated at several sites even with conventional column alignment.INTRODUCTIONThe DJM method is a representative deep soil mixing technique of dry mixing manner in Japan. DJM can successfully install soil mixing columns trough automatically controlled binder injection based on pneumatic feeding theory and cumulative experiences.This method was joint-developed in 1978 by private organization under initiative of the Public Works Research Institute of the Ministry of Construction as the optimum method for improving the Japanese soft ground. Figure 1 shows full view of the DJM construction system. Figure 2 illustrates DJM working system indicating Binder Feeding Plant side and Mixing Machine side respectively.As typical soil mitigation method, many projects related with rivers and roads and city development has required DJM technology. The total number of the projects applying DJM has exceeded 5,000 with the total treated soil volume more than 32,000,000 m3 by the end of fiscal year 2013."

Jan 1, 2015

By Y. Maeda

Non-ferrous smelting furnaces generally install a gas cooling system for treatment of waste gas containing SO2,. From the point of view of corrosion resistance and recovery of waste heat, the high pressure boiler system is the best way to cool gas, however this system requires high initial investment and relatively higher operating costs. Because the feasibility of this boiler system greatly depends on the smelting process and scale, other lower temperature systems, e.g. water-cooled jacket system, are more suitable if the smelting process does not produce enough steam nor generate enough electricity to compensate operating cost. In additton, the water-cooled jacket system is simple in structure and easy to operate. For those reasons, it is applied widely. A new smelting furnace was planned in our factory and it was necessary to install waste gas cooling equipment. In our case, a water-cooled jacket system was more feasible because of the low gas volume and high dust content. It was also expected to operate without maintenance for ten years. On the other hand, some leakage problems with the water-cooled jacket had been experienced in the past. That is because SO2 In the waste gas changed into sulfuric acid which corroded the jacket material. As the first step, several data from actual' usage were reviewed to throw light on the corrosion process, and an appropriate procedure to determine the operating temperature of cooling water was obtained. For the basis of this study, a water-cooled jacket system was newly designed and tested for three months in a pilot plant. After this system's performance was confirmed, it was installed in a new furnace as a commercial plant. After one year of operation, the initial thickness of carbon steel jacket remains almost the same.

Jan 1, 1992

By P J. Howard

Atlas Iron Limited’s McCamey’s North project lies at the eastern end of the Hamersley Basin, approximately 50 km east of Newman, Western Australia, and 3 km northeast of BHP Billiton’s Jimblebar Mine. The presence of significant surface iron mineralisation identified during field reconnaissance, has subsequently been further defined by detailed mapping and RC drilling.The project area is dominated by outcrops of moderate to steeply north and south dipping banded iron formation, cherts and shales of the Boolgeeda Iron Formation overlying rhyolites and rhyodacites of the Woongarra Volcanics. In lower lying areas recent colluvium and alluvium mask the Archaean geology. Drilling and downhole geophysics has allowed a composite stratigraphic section to be compiled through almost the entire Boolgeeda Iron Formation.Surface orientations and subsurface stratigraphic correlations using natural gamma logs indicate large scale open folding about east-west trending fold axes across the project area; while small scale tight to isoclinal folding with similar fold axis orientations are visible at the outcrop scale. These folds are cut by a number of moderate to steeply south-dipping normal faults defining a series of north-dipping fault blocks which repeat the stratigraphy across the project area.Bedded iron mineralisation consists mainly of haematite-martite and goethite ores with best results of 78 m @ 60.5 per cent Fe. Vitreous goethite is observed at the surface of the mineralised horizons. The mineralisation exhibits a strong stratigraphic control and extend down-dip up to 120 m below surface. The strike extent of the mineralisation is still to be determined. An inferred resource of 39 Mt at 58 per cent Fe has been defi ned to date (ASX: AGO 3 February 2011).The fi ndings at McCamey’s North indicate that there is potential for economic iron mineralisation to exist in other areas of Boolgeeda Iron Formation within the Hamersley Basin.

Jul 11, 2011

By L. Filippov

"Nickel is an important metal with the total global consumption of about 2 million tons per year. It is sourced from both sulfide and laterite ore, but currently laterites are becoming more attractive for nickel production due to the depletion of high grade nickel sulfide ores. Laterites are generally processed by hydro or pyro-metallurgy and therefore, pre-concentration of nickel before such processes is very important. In this paper the effect different physical methods (including flotation) on the pre-concentration of nickel in laterite ores will be discussed. The ore used in this study was a laterite from South East Asia. Nickel was upgraded using different methods such as magnetic separation, flotation and sizing. The effect of ore mineralogy on choosing the best strategy to upgrade nickel will be discussed. The findings of this project will help to unlock a substantial volume of nickel with significant value from laterite ores.INTRODUCTION Nickel is an important metal with the total global consumption of about million tons per year which has grown rapidly during last decades (Mackey, 2011). Nickel is sourced from two different types of ores, sulfide and laterite. The majority (about 70%) of the world’s nickel resources occur as laterite ores which are often complex, and low grade, and therefore expensive to treat using conventional methods (Xu et al., 2013). Today, nickel laterites are more attractive for production of nickel as the amount of high grade nickel sulfide ores has diminished (Janwong, 2012). Therefore more economic processes to recover nickel from these resources should be developed.It should be noted that nickel laterite mineralogy is complex, and nickel often presents as ultrafine inclusions in a number of mineral phases. Because of the low nickel concentration and variable distribution in these phases, effective upgrading by physical separation processes would be challenging. Researchers have tried to improve nickel laterite flotation recovery by using a number of feed preparation techniques. A summary of the nickel grades obtained using flotation and magnetic separation as reported in the literature is presented in Table 1. It can be seen that only minor nickel upgrades have been reported. Quast et al. (2015) have concluded that the complex mineralogy of nickel laterite ores makes it difficult to achieve any significant nickel upgrading by physical techniques, including flotation. They achieved 40% increase in the nickel content (from 1.0% to 1.4%) at a nickel recovery of 43% (Quast et al., 2015). Various attempts in USA, New Caledonia, India and Australia, to upgrade nickel in laterite using magnetic separation have not been successful (Quast et al., 2015). A recent comprehensive review on topics influencing nickel laterite flotation has shown that further investigations in the flotation of laterite ores are undoubtedly warranted (Farrokhpay & Filippov, 2016)."

Jan 1, 2018

By A. V. Rasskazova

"The oxidized and mixed ores are processed by heap leaching. Primary ores with high gold content are floated. In recent years mining of primary ores with the low gold content (up to 4 ppm) has increased. Extraction of gold from these ores by floatation is technologically ineffective. Gravity concentration is ineffective for fine gold particles because of their floatability. The research objective was assessment of the viability of processing gold-bearing ore with combined gravitational and hydrometallurgical methods and testing of recovery of metals from a gold-copper oxidized ore chloride-hypochlorite leaching solution. The advantage of chloride-hypochlorite lixiviant is the low cost of reagents which is produced by the electrochemical synthesis of NaCl solution with the addition of HCl. The adsorption of chlorine compounds by a mineral matrix and its ability to oxidize the refractory ore components and allows for the application of chloride-hypochlorite systems for gold recovery for both oxidized and primary ores. The complexity and problem in using a gold–chloride system is the strong adsorption of gold–chloride complexes onto mineral surfaces, such as goethite, quartz, and alumina. In preliminary testing, gold recovery from gravity circuit gold bearing concentrates processed by agitation leaching in chloride-hypochlorite solution, gold recovery has reached up 82% after 4 hours of leaching. Chloride-hypochlorite leaching of copper-gold oxidized ore with preliminary processing by sulfuric acid provided for 94 % gold recovery to solution. Understanding of ecological hazard of cyanides is the motive power of researches in the field of search non-cyanic chemistries to provide for technologically and economically effective solvents of gold. Soluble compounds of chlorine with a suitable oxidizer are one of the alternatives to cyanides. Basic researches of gold extraction by chloride-hypochlorite solution have shown high rates of gold recovery.INTRODUCTION Because of the continued and growing environmental concern for the use of cyanide for gold processing, interest for the use of non-cyanide lixiviants, especially with halides has renewed recently (Tran et al., 2001; Ferron et al., 2003; Bhaghalha, 2007). Leaching solutions based on halides (chloride, bromide and iodide) are viable alternative to cyanide (Kwang et al., 2008). The major disadvantage of the chlorine–chloride system is the high reactivity of chlorine in reaction with sulfide and gangue carbonate minerals. It is believed that only high grade materials may be treated by chlorine–chloride systems economically (Baghalha, 2007). Another important problem of the application of gold–chloride complex is that it tends to be rather unstable and may re-precipitate upon contact with a reductant, such as sulfidic minerals of ore. It is well known that Au(III)–chloride hydrolysis species are strongly adsorbed by goethite, quartz, and alumina (Machfsky et al., 1991). To minimize adsorption of gold–chloro complexes, it works best to minimize the adsorption time."

Jan 1, 2018

By Jeffrey T. McGinty, Frank M. Wheeler

Plant layout is the arrangement of equipment, process areas, departments, infrastructure, and support facilities. Plant logistics is the flow of parts, people, resources, and information throughout the production process. This chapter: outlines key factors and provides checklists to facilitate layout development; presents risk management approaches to test the logistics and functionality of alternative layouts; and uses real-world examples to illustrate effective simulation modelling to assess plant layouts.

Jan 1, 2015

By James S. Grichar

Interest in mergers in the nonfuel mineral industry developed when 5 were listed among the 50 highest valued mergers in the United States in 1981. This report presents a Bureau of Mines study of trends in merger activity from 1960 to 1979 and explores motives for mergers in the nonfuel mining and mineral industry. The objective was to determine precedent for or a trend toward the 1981 acceleration in merger activity and to examine certain financial motives for non fuel mineral mergers. Data indicate that the relative value of non fuel mineral mergers has grown since 1972 although the number of mergers has remained proportionate to historical trends for all mergers. Since 1974, the assets acquired in "large," nonfuel mineral firm mergers, those of $10 million or more, have comprised at least 93 pct of assets acquired. More nonfuel mineral firm mergers involved mineral companies as the acquiring firm than vice versa but mining and minerals firms acquired were of higher value than nonmining firms. A major motivation for mergers involving large mineral firms was the acquisition of assets at less than replacement costs. Univariate statistical testing, a methodology chosen for its applicability to the data, confirms this hypothesis while rejecting other financial motives. The remainder of the work is devoted to a discussion of suggested areas for future study.

Jan 1, 1984

By Michael Rieber

In this study a generalized specification and costing model for high tonnage coal carrying conveyor belts of 3.5 to 100 miles is presented. These belt systems, in modular units or flights, of up to 9 miles in length can be considered in terms of gathering systems. The study format is sufficiently open to allow users to insert their own requirements and parameters. A specific case study is provided. Because conveyor belts are feasible almost anywhere, this study has not investigated any specific route or geographic location. Rather, it has concentrated on setting up an heuristic programming model for conveyor belt facility optimization and cost minimization. The analysis starts with the principle factors involved in the design of the system and their optimization for various cases. This is followed, in Section 5.4, with a factor by factor cost analysis based on industry data and the preceding optimization. The next step is the development of both facility and costing models suitable for computer analysis. Logic flow diagrams are presented at each major analytic step.

Jan 1, 1977

By Noel N. Moebs

Five LANDSAT lineaments in the coal mining region of southwestern Pennsylvania were investigated by the Bureau of Mines to determine their geologic character, relation to subsurface conditions, and the means of discriminating one from another. The investigation included earth resistivity and very low frequency (VLF) electromagnetic traverses, soil moisture sampling, and a correlation with coal mine roof conditions. The lineaments could not be detected by the methods used, suggesting that they might be a surface phenomenon unrelated to subsurface geologic structures or roof stability in coal mine workings beneath.

Jan 1, 1987

By M. R. Geer

Traditionally, fine coal is more troublesome than the coarser sizes at every step of the coal-preparation process--screening, cleaning, dewatering, and drying. Therefore the present trend toward a higher proportion of fines in the run-of-mine product, brought about by changes in mining practice necessitated to increase productivity, has added greatly to the task of preparing coal for the market. One of the more difficult and costly problems involved is that of recovering fine solids from the washery water. These fine solids should be recovered in the interest of conservation, and they must be removed to provide recirculating water of proper quality. If there is a plant effluent, it must meet increasingly stringent requirements against stream pollution. Vacuum filtration has been used for years at a few plants to recover the extreme fines, but its additional cost discouraged general adoption until recently. Now, with growing emphasis on better solids recovery, filtration is becoming more widespread. Many coal slurries filter readily, giving high cake rates and clean filtrates. Others, however, particularly those containing either a high proportion of material finer than 200-mesh or an appreciable amount of clay, are much more difficult to filter. Many of these refractory slurries can be rendered more filterable by flocculation. A previous report of Bureau of Mines research dealing with flocculation alone was published in 1940.5/

Jan 1, 1959

By Michael Hood

High-volume, low-pressure water jets have been employed for erosion of loosely consolidated rocks for centuries. This excavation method finds application in specialized circumstances even today. The use of high-pressure, low-volume water jets for rock cutting is more recent and was made possible by the development of high-pressure water pumps. Despite the benefits often claimed for these systems, high-pressure water jets still have not found widespread application. In this report, the U.S. Bureau of Mines has reviewed the various methods that have been employed using water jets to break rock and has focused on one method, termed "jet-assisted cutting," which was determined to be the closest to commercial development. The current state of knowledge based on laboratory and field experiences using this cutting method is reviewed, and possible future developments for this approach to excavation are assessed.

Jan 1, 1990

By F. L. Wideman

This report describes the sinking of No. 3 shaft at the Westvaco mine. It is one of a series of publications of the Bureau of Mines on mining methods and practices in the United States. The Westvaco mine is in Sweetwater County, Wyo., approximately 23 miles northwest of the town of Green River (fig. I), There are no permanent habitations in the vicinity of the mine, and employees live in Green River or Rock Springs, Wyo., 14 miles us t of Green River. The mine plant is on a windswept, treeless plain, from which low buttes and flat-topped ridges rise. The altitude at the collar of No. 3 shaft is 6,351 feet. The climate is arid, with temperatures as low as 40° below zero in the winter. Blacks Fork, a tributary of the Green River and a perennial stream, flows near the mine.

Jan 1, 1959

By W. R. Donaghue, R. L. Robinson, C. Scott

Whilst spontaneous combustion has never been considered a major problem in south Durham, certain collieries in the area have a history of heatings and precautions are essential. Three collieries are affected - Shotton, Vane Tempest and Seaham - and in the case of the last two, there are huge areas of high quality coal to work under conditions where spontaneous combustion is a real hazard. The seam being extracted has an immediate roof in goaf left by the incomplete extraction of a contiguous seam worked before the turn of the century. The presence of residual coal stocks and old roadways and cavities adds to the difficulty of preventing unwanted air movement. The main preventive measures adopted are the construction of airtight gateside packs and the use of sprayed surface coatings in the gate. Sampling systems and sampling points are described and, in particular the field of continuous monitoring from the surface is examined. The resulting possibility of a quantitative as well as qualitative assessment of the preventative measures required is discussed.

May 23, 1905