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By C. W. JEFFERS

At its annual meeting on March 5, 1928, in Washington, D. C., the Joseph A. Holmes Safety Association gave to the Ford Collieries Co., Curtisville, Pa., a certificate of honor for "having worked 922,628 underground man-shifts from August 14, 1920, to December 31, 1926, producing 5,755,669 short tons of coal without a fatality." This remarkable record certainly deserved recognition. It developed that this company's freedom from fatalities continued until October 2, 1929, hence the full period during which no underground fatalities occurred was from August 14, 1920, to October 2, 1929, or 9 years, 1 month, and 18 days, the total tonnage being over 7,700,000. Table 1, shows the complete safety record of the Ford Collieries Co. since 1920 as given by the officials of the company. The first item in Table 1 shows a remarkable performance. This company since 1920 has mined 15 times more coal per fatal accident than the average pro- duction per fatal accident for the State of Pennsylvania in 1928 (255,257 tons). Excluding the two fatalities (one in 1922 and one in 1929) the severity rate for the same period has been 1.259 per thousand hours worked, a record of which the company may justly be proud. However, including the fatal accidents the rate is 2.407. This compares favorably with an average of 12.4 in 1928 for 66 mines in the National Safety Competition. The Ford Collieries Co. operates three mines located in the vicinity of Curtisville, Allegheny County, Pa. One of these mines, Benjamin No. 1, is idle at the present time. The officials are: A. R. Pollock, general manager, Curtisville, Pa., and C. W. Pollock, assistant general manager in charge of safety and operation.

Sep 1, 1930

By ALICE V. Petar

Thallium is one of the rare metals that has come into commercial use within recent years . Its comparative scarcity , combined with a resemblance to the common metal lead , have retarded the development of uses for thallium . Although production is still measured in pounds rather than in tons , it is now finding application in a number of fields . Perhaps the earliest commercial use of thallium was as a constituent of optical glass of higher refractive power than similar glasses containing lead . One of the later applications to attract attention was the use of the oxysulphide in a sensitive electrical device similar to the selenium cell . The " Thalofide " cell , which was patented in 1919 , constituted for a time the most important outlet for thallium. During the next few years the limited use of thallium and its salts in other fields was insufficient to absorb an annual production of a few hundred pounds , and the price dropped from $ 16 or $18 per pound in 1922 to $ 5 per pound in 1924 . Beginning in 1925 several new uses were developed , especially as a poison for rodents and ants , and as a result the demand for thallium increased sufficiently to cause a recovery in price to the present level of from $12 to $15 per pound .

Jun 1, 1931

By D. M. Soboroff

Etchants containing hexavalent chromium and sulfuric acid are used in a variety of surface-finishing operations. When the resultant spent solutions are discarded, substantial quantities of chromium are lost and pollution prob¬lems are created. To minimize the undesirable environmental effects while improving metal and minerals recycling technology, the Bureau of Mines is conducting research on a method for the economic inplant recycling of these waste etchants. Trivalent chromium, produced when the etchant reacts with a sub¬strate, is oxidized in the anode chamber of a diaphragm cell; other metals, dissolved during the etching operation, are transferred to the catholyte. When waste brass etchants are treated in this manner, all of the trivalent chromium is oxidized and more than 40 percent of the copper and zinc is removed. Similar copper removal and chromium oxidation are achieved with waste printed circuit board etchants and rinse waters from plastic etching operations. The electrical energy needed to regenerate 1 kg sodium dichromate is less than 9 kwhr. Regenerated brass etchants evaluated by two companies equaled or exceeded the performance of fresh etchants.

Jan 1, 1979

By J. O. Lewis

"The significant facts in the problem of the relation between the production of crude petroleum, and the ever-increasing demand for petroleum products are that in spite of continually increasing production, improvements in methods of refining and utilization, and heavy increases in imports, demands grow still more rapidly and we seem always faced with a shortage at hand or lust ahead. On the other hand, our foremost authorities warn um of entirely inadequate domestic reserves. Looking abroad we find some large fields and many of speculative promise, 'tut the situation is complicated by international relations and demands by other countries which promise to be even more insistent than oars. This is the situation, then. We can not rely upon our own Crude Petroleum to meet the Ever Increasing Demand for Petroleum Products.I wish to follow this somewhat alarming statement by saying at once that the Bureau of Mines is not pessimistic in facing this situation. To my mind those who discuss the oil situation may be placed in three categories; the pessimists, the optimists, and the super-optimists. The pessimists I call those who see darkly and will concede no possibility of solution. According to them a few years will see the automobiles piled in windrows of 'dilapidated junk, I have no sympathy with this point of view and deem it vicious and entirely unwarranted.The optimists I term those who believe that there is a solution and that we shall be able to meet all of our reasonable requirements for as far into the future as can be foreseen, yet who recognizes that this desired end can not be attained without prevision and energetic effort.The super-optimists are those who will say to you, ""There is nothing to this talk of shortage, whenever we have needed oil we have always found it and always will."" To these gentlemen the possibility of an inadequate supply of oil is as incomprehensible as the possibility of the extinction of the passenger pigeon was to the early settlers who saw flocks that hid the sun for days during their passage. The passenger pigeon disappeared within two generations thereafter, and I deem this point of view as being perhaps more vicious than that of the extreme pessimist. It seems to me it is nothing less than improvidence lulling us into a false sense of security. There is an old proverb to the effect that ""The Lord helps him who helps himself."" I believe that we shall solve the oil problem, but I do not think it will be solved by vague optimism. It is going to call for our most energetic efforts and I believe we shall have to do a lot of ""helping ourselves."""

Oct 1, 1920

By W. H. Coghill, B. W. Gandrud, F. D. DeVaney

"The self-fluxing iron ores of Alabama are the foundation of the thriving iron and steel industry of that State. In addition to these deposits of self fluxing ores there are seams containing practically the same percentages of iron but too much silica. These ores at present are valueless, but if they could be concentrated by reducing the silica content, the ore reserves of the Birmingham district would be greatly augmented. A detailed report on the iron-ore deposits of the district, describing the types of ore and their extent, has been published.In forwarding its mineral conservation policies the United States Bureau of Mines has given some attention to the siliceous ores of this district.The low cost of gravity concentration gives this process first rank in the beneficiation of iron ores. For this reason many experimenters have tried to concentrate the Alabama iron ores on tables. In the face of the early failures a new trial has been made and the results have justified the effort.In this work more attention than formerly has been given to the physical, properties of the ores. The removable siliceous gangue is in the form of oolitic grains which ""shell"" out like corn, leaving the hematite as rich high-grade ""slime"" and as clean granular grains. The ""slime concentrate"" may be recovered by well known desliming processes. The oolitic grains and granular hematite are separated on tables."

May 1, 1929

By R. V. Ramani

"The importance of adequate mine ventilation for good health and safety conditions has been recognized since miners first ventured underground. All over the world, governmental actions on mine health and safety arc directly connected with mine atmospheric environments their assessment and control. These governmental actions have been, and continue to be, motivated by the repeated experience that potential threats from inadequate control can evolve, either suddenly or in the long-term, into unpleasant reality, with catastrophic health and safety consequences. These governmental actions arc also an indication of the remarkable professional progress being made in the field of mine ventilation.Surely, no developed country allows underground mines to operate without strong measures for the control of ventilation under legislation specific to the mining industry. In the United States, the federal government's responsibility for mine safety has evolved over the years through a series of legislative actions beginning in 1865 and continuing through 1910, 1941, 1947 and 1952.The passage of the Federal Metal and Nonmetallic Mine Safety Act of 1966 (the 1966 Metal Act), the Federal Coal Mine Health and Safety Act of 1969 (the 1969 Coal Act) and the Federal Mine Safety and Health Amendments Act of 1977 (the 1977 Mine Act) arc the most important milestones in this long legislative history. The 1977 Mine Act adopted many of the stronger features of the Occupational Health and Safety Act of 1970, perhaps the most significant piece of legislation on workers' occupational health and safety in US history.It is worthwhile to ask, ""How far has the United States come in mine ventilation since the enactment of the 1969 Coal Mine Health and Safety Act?"" This Act and its associated regulations defined in great specificity many standards for healthful and safe operation of a mine and. in some cases, what constitutes good ventilation practice."

Nov 1, 1995

By John W. Finch

The present epoch in human history has been variously described as the age of coal, of oil, of iron and steel, and of power. All agree, however, that it is a great industrial period. Power is of course the vital force in the industrial organism; but power is derived chiefly from mineral fuels or from harnessed and controlled water - also a mineral substance although usually not so classified by industry. However, the latent energy of fuels cannot work for men until it is changed to active energy by combustion and until this active energy is converted into motion. This motion is just as indispensible as the energy itself. Likewise, the latent energy of water cannot be utilized until it, too, is converted into motion; out the mechanisms and devices for converting latent energy into motion, as well as the structures in which they are operated, would not be possible without metals and other minerals. Consequently, minerals are fundamental in industrial civilization.

Jan 1, 1938

"The U.S. Bureau of Mines established on August 15, 1983, The Generic Mineral Technology Center for Respirable Dust (Dust Center) within the Mining and Mineral Resource Research Institutes (MRIs) at The Pennsylvania State University and West Virginia University, and in association with participating MRIs at Massachusetts Institute of Technology and the University of Minnesota. In 1986, Michigan Technological University (MTU) was awarded a grant through the Dust Center. The center's research program has been developed with recognition of the stated objective of the Federal Mine Safety and Health law, which is ""... (to) permit each miner the opportunity to work underground during the period of his entire adult working life without incurring any disability from pneumoconiosis of any other occupation-related diseases..."" The Dust Center's program is designed to foster an accelerated attack through fundamental research on problems confronting the control of respirable dust in mines. The interactions of the universities and the research program components in the characterization of coal seams, respirable dust particles and the workers lungs are depicted in the logo of the Dust Center.The primary goal of the Dust Center is to reduce the incidence and severity of respirable dust disease through advancing fundamental understanding of all aspects of respirable dust associated with mining and milling, and the interaction of dust and lungs. The Dust Center's research program explores these concerns with the objective of refining existing strategies and developing new respirable dust control techniques that are consistent with the fundamental dust-lung interaction processes that lead to mine worker disability. The work concentrates on: (1) control of dust generation; (2) dilution, dispersion and collection of dust in mine airways; (3) characterization of dust particles; (4) interaction of dust and lungs; and (5) the relationship of the mine environment, geology, and seam characteristics to dust generation and mobility. The fundamental aspects of this work are applicable to the control of respirable dust problems in both hard rock mines and coal mines, and to other dusts such as those generated by diesel equipment. Achieving the Dust Center's goals also involves the training of engineers and scientists, graduate students, and undergraduate students through their respective institutions, and technology transfer to industry. The distribution of personnel in the various universities are presented in Table 1. A directory of Dust Center principal investigators is presented in Appendix 1. A summary of degrees granted and mineral sector employment is presented in Table 2. The subjects of theses developed under the various research projects are presented separately in Volume 7. The center research is fully compatible and complementary with the existing and ongoing U.S. Bureau of Mines activities (see Volume 2). Additionally, the expertise and facilities of the NIOSH--Division of Respirable Disease studies are available as a result of the existing relationship between NIOSH and West Virginia University. Figure 1, Respirable Dust Center Projects and Activities, presents the various projects in the five major areas of investigation and the scope of characterized dust samples, the suite of tests, the sampling and dust generation methods, and the size, chemical and mineralogical analysis performed in the center. Table 3 presents a summary distribution of the 95 publications and presentations that have emanated from the center. In addition there are more than thirty presentations made at each annual Dust Center review meeting. The titles, authors and location of presentation for publications supported by the Dust Center are presented in separate publication volumes for 1984 (Volume 3), 1985 (Volume 4), 1986 (Volume 5) and 1987 (Volume 6)."

Jan 1, 1988

By W. H. Ode, W. A. Selvig

Low-temperature distillation tests at 200°, 350°, and 500° C. were made on a subbituminous coal from Boulder County, Colo., and a subbituminous coal from Weld County Colo., in connection with a survey of carbonizing properties of American coals 4/ and investigations of their chemical and physical properties. 5/ The coal represented by the sample from Weld County was reported to give off combustible volatile matter at unusually low temperatures when placed on a fuel bed. The yields of tar and oil and the composition of the as from this coal, as obtained in the distillation tests, did not confirm this report. These yields and the gas composition of the Weld County coal differed but little from those obtained from the coal from Boulder County. Both coals yielded tar and gas in amounts considered to be normal for coals of their rank.

May 1, 1937

By M. J. Ankeny

All bituminous-coal mines, by the nature of their product and inherent gassy tendencies, are subject to explosions or mine fires. The evolution from large, hand-loading sections employing numerous men and containing open-type equipment, lights, and nonpermissible explosives to small, concentrated mechanical sections with but few well-supervised men utilizing modern preventive equipment has not altered this premise. Mine catastrophes such as Centralia and New Orient No. 2, as well as recent disasters of less magnitude, have refuted the trend of thinking that modern equipment, will prevent or localize explosions and prevent widespread or loss of life.

Jan 1, 1952

By J. D. Ramsdell

The study described in this report was undertaken to obtain information on the character and effect of antimony additions to titanium. The availability of high-purity, low-hardness titanium metal, resulting from fused-salt electrorefining techniques, permitted a reassessment and evaluation of the physical behavior of titanium-antimony alloys. Alloys, based on several grades of titanium containing up to 10 percent antimony, were arc-melted and processed to sheet by hot and cold rolling. Properties and characteristics were evaluated by hardness tests, hot and cold rollability, annealing treatments, metallographic examination, and tensile tests.

Jan 1, 1960

By A. W. Ambrose

"Those having an intimate knowledge of the relation between production and consumption of crude oil in the United States have realized for some time that production will not be able to keep pace with consumption. The American public has had this called forcibly to its attention by the increased prices of gasoline and crude oil, and by the recent shortage of gasoline on the Pacific Coast. In substance, each year we are consuming millions of barrels of oil more than we produce, and this deficit must be made to by importations. A careful analysis of the situation makes it evident that we need every barrel of oil that can be produced.Need for the Petroleum Production Engineer.Under present production practices perhaps 80% of the oil still remains in the sand. (See Lewis, J.O., Methods for increasing the recovery from oil sands, U. S. Bureau of Mines, Bulletin 148 p. 8.) Many wells are making water, and even whole pools are being flooded. The burning of fuels under field boilers is not generally efficient, and often gas is not made to do its full duty in bringing the oil to the well.In the past the producer has had to combat these and other problems single-handed. He has been too busy to give them special attention, and he has had little competent engineering advice. Oil, gas, and water occur underground according to certain natural laws. Undoubtedly an engineer, who is familiar with production practices and understands the fundamentals of the accumulation of oil and gas, can be of service to the producer by specializing on certain problems with a view of getting mare oil from the sand. In every other enterprise of similar magnitude the engineer is regarded as a necessary unit to its operation, and he should be so in the production of oil. His field of work should extend to every phase of production in which science and engineering and geology"

Sep 1, 1920

"As stated earlier the primary goal of the Generic Mineral Technology Center for Respirable Dust is to reduce the incidence and severity of respirable dust disease through advancing the fundamental understanding of all aspects of respirable dust associated with mining and milling and the interaction of dust and lungs. While initial work was directed to coal dust the charge to the dust center has been expanded to include diesel particulates and asbestosis, the latter of deep concern not just to workers in the mineral sector of the economy but also to the general populace.A major facet of Dust Center research has been the analysis and documentation of comprehensive research protocol and procedures that are appropriate state-of-the-art in the various areas of respirable dust. In addition to definition of standardized research protocols and procedures which would be utilized by center personnel for uniformity and reproducability there is a considerable need for utilizing standardized respirable dusts in experiments with consistent, reproducible characteristics which simulate those of actual mine dust. This respirable dust needs to be available in large quantities for a wide variety of research uses that include animal and medical experiments. The dust must be free of the lubricating oils and grinding wheel contaminants that are frequently encountered in laboratory generated dusts.The holistic approach to establishing standardized protocols and procedures applicable to the five major research areas of the center is presented in Figure 5.In one hypothesis, range in coal volatility is considered to be a major causal factor in the incidence and severity of pneumoconiosis. Therefore a suite of characterized standard respirable dust samples have been prepared for researchers from coals representing the western (high volitile A bituminous), central (medium volatile bituminous) and eastern (anthracite) mining areas of Pennsylvania. Quartz, limestone (rockdust) and kaolin clay samples, representing important mineral constituents of coal dust have also been prepared.A suite of medical investigations have been developed utilizing small and medium size animals as well as non-human primates in a variety of dust/lung interaction projects which will be discussed in the next section. A number of respirable dust sampling and dust generation methods have been investigated and selected techniques utilized for both in-mine and in-laboratory research investigations. These will also be discussed in more detail later. A wide range of respirable dust size, chemical and mineralogical analyses have been investigated, standardized and documented for use in various research investigations.This interaction and documentation of various respirable dust sample procedures, animal and medical tests, sampling and dust generation methods, plus size, chemical and minerological analysis applied in the five major areas of research investigation have served to create a very favorable synergism and rapid technology transfer in the respirable dust center."

Jan 1, 1988

By Gwendolyn D. Hood

The U.S. Bureau of Mines developed a dewatering technique for treating wastewater that was tested on waste slurry from a commercial tile company in Alabama. Raw wastewater samples were pretreated with 10 Ib calcium chloride and 10 lb Wyoming bentonite per 1,000 gal of slurry. After pretreatment, polyethylene oxide (PEO) at dosages varying from 0.05 to 0.20 lb per 1,000 gal was mixed with the waste slurry, forming strong, tough floes that were separated from the clarified water using a trammel. The flocculated slurry was dewatered to a consistency that could be handled for subsequent disposal in a landfill. The clarified water quality was equivalent to that of the company's present treatment system.

Jan 1, 2010

By John B. Umhau

In 1930 , 65,448 long tons of virgin or primary tin were consumed by 1,292 establishments in the United States , representing about 91 per cent of the total consumption as computed from imports , exports , and stocks at the beginning and the end of the year . The reported consumption was equivalent to 38 per cent of the world's tin production in 1930 , estimated at 171,000 tons , and was 12 per cent less than the 74,369 tons consumed by 1,307 establishments in 1928 . Decreased consumption of new tin in 1930 ás compared to 1928 was a reflection of the general industrial depression . All of the tin- consuming industries showed substantial decreases except tin plate and terneplate , white metal , and tinning , which showed small tonnage increases aggregating only 1,200 tons . The largest tonnage decrease was in the use of new tin in babbitt which declined 33 per cent in 1930 as compared to 1928. This was largely attributable to the decreased production of automobiles and trucks , which was 24 per cent lower in 1930 than in 1928. Percentage decreases in other important tin- consuming industries were as follows : Solder 18 per cent , bronze 19 per cent , tin foil 40 per cent , chemicals 23 per cent , tin oxide 44 per cent , and type metal 46 per cent . The distribution of the amount consumed by various uses during 1927 , 1928 , and 1930 is shown in table 1 . Consumption studies indicate the fact that variation in tin consumption from year to year parallels the fluctuations in demand for the already wellestablished tin products . For example , the manufacture of motor cars and trucks3 required only 11,000 tons of tin in 1930 compared to 19,000 tons in 1928 ; the canning industry continues to require the greater portion of the tin plate and much of the solder . Recently developed industries , while affecting total consumption of bearing metals , solders , etc. , to some extent , have made little change in the relative importance of these commodities as consumers of tin .

Jan 1, 1932

By A. W. Ambrose

A few years ago, (March 3, 1915) Congress passed a law providing for the establishments of ten mining experiment stations under the supervision of the Bureau of Mines. In 1917 the Secretary of the Interior decided that one of these stations should be devoted to Petroleum, and in the early part of 1918, approved the establishment of the Petroleum Experiment Station at Bartlesville, Oklahoma, upon the condition that the city furnish the site for the buildings and guarantee $50,000. for the erection of the buildings. A building site of 5 acres and the necessary building fund was furnished by the Bartlesville Chamber of Commerce.The buildings consist of an administration and laboratory building, both of brick construction. The former is a two-story structure of eight rooms. A large room occupying over half of the main floor is devoted to the library, reception room, and clerical force. The remaining rooms comprise a drafting room and six offices occupied by the staff assigned to this station. The laboratory is a one-story brick building and contains a well-equipped chemical and physical laboratory, also a machine shop and mechanical laboratory. In addition to the main buildings there now are on the property an experimental refinery, a blue-print house, and a store house. These latter buildings are all of sheet-iron construction.

Oct 1, 1920

By Ellis S. Hertzog

The data published in this report cover only one phase of a special study of the physical and chemical properties of Alabama coals made by the Bureau of Mines. In addition to determinations of friability, the survey included determinations of grindability, B.t.u. value, end ash-fusion temperature. Assay distillation tests, both for high- and low-temperature carbonization, and proximate and ultimate analyses were made also. However, this preliminary paper is concerned only with the results of friability tests and is issued to expedite the release of this information to the public. The friability test measures the liability of a coal to break into smaller pieces when subjected to repeated handling, as occurs in the mining, preparation, and transportation operations. Friability depends on many physical characteristics of the coal that vary not only between different seams but also in the same seam. The laboratory methods of determining friability have been developed to give a practical means of estimating degradation of size. So far as is known to the authors, no data on the friability of Alabama coals have ever been published. This paper makes available for the first tine fairly comprehensive information on this subject. Because the procedure for the tumbler test for determining the friability of coal is relatively new to the coal operators, the authors have included a complete description of it in this report.

Jan 1, 1938

By Ellis S. Hertzog

The material published in this report is part of a special study of some of the chemical and physical properties of Alabama coals. The complete study included friability and grindability determinations, high and low temperature assay distillation tests, and ash fusion-temperature determinations. Proximate and ultimate analyses and. calorific values of the coal samples also were obtained. This paper is concerned only with grindabilities, although proximate analyses have been included to give a better picture of the problem as a whole. The growing interest in grindabilities of coals is a result of the increase in use of pulverized fuel in rescent years. The tenative ball-mill grindability method D408-35T4/ was used in making all the determinations. The method of sampling and the technic of the testing procedure is described in Considerable detail in this report because the procedure was established quite recently. The ball-mill grindability index is a measure of the ease with which coal may be ground, which may be an important factor in estimating pulverizing costs. Up to the present time few data on the grindability of Alabama coals have been published. The data in this paper show that the Warrior and Cahaba fields exhibit a wide range of grindability in their coals. The mines tested are well distributed throughout the productive areas of these fields, and it is possible to make rough estimates of the grindabilities of coals not listed in this report from the data given for mines situated in the same vicinity.

Jan 1, 1938

By W. A. Calhoun

A method for treating high-iron Arkansas bauxites for recovering both abrasive and metal-grade bauxite has been developed by the Bureau of Mines. Present practice usually produces a reject containing appreciable quantities of metal-grade bauxite; however, the processing renders the alumina in the reject unsuitable for the Bayer extraction treatment. Thus the Arkansas abrasive bauxite industry has, in the past, produced little or no metal-grade bauxite. The present investigation was made to determine the possibilities of batter utilization of those particular bauxites through recovery of the wasted metal-grade portion. The large expansion of aluminum-production facilities planned for 1951-53 makes recovery of metal-grade bauxite from presently treated abrasive and marginal abrasive ores en especially timely objective and a welcome addition to our aluminum potential. The quality of the Arkansas bauxites and the inherently associated titania content have made this material particularly attractive to the abrasives industry. however, the gradual depletion of natural abrasive-grade bauxite reserves in this area, the comparative scarcity of high-grade ore, and the difficulty of maintaining adequate reserves have necessitated blending different grades of bauxite calculated to meet specifications. Production of abrasive-grade bauxite from tile, high-iron reserves 13 becoming, increasingly necessary. In one commercial operation, producing abrasive-grade from ores averaging slightly less than 10 percent Fe2O3, approximately 2.7 tons of ore are required to produce 1 ton of abrasive-grade bauxite. The reserves of ore of this grade, however, have been considered inadequate for a long-range production, and ultimately ores averaging 12 to 15 percent Fe2O3 will have to be treated to moot the continued demands of the abrasive industry.

Jan 1, 1952

By Edward Thomas

In 1947 the Bureau of Mines, as an accident-prevention measure, decided to advocate the adoption of roof bolting (suspension roof supports) in coal mines where it appeared to be applicable. Subsequent experience has disclosed that the applicability of this support is more general than was first suspected; moreover, comparison of the accident records of mines before and after adoption of the roof-bolting method shows results that more than justify the effort and funds expended. The industry has responded enthusiastically, because roof bolting proved to be not only an accident-prevention measure but also one to increase productive efficiency. In some instances this increase in the productivity of men and machines has been almost incredible and has led many mining men to conclude that through some hocus-pocus they can now cast aside many or all of the time-proven rule of good mining practice. If this tendency is not counteracted, it could easily result in an increase of roof-fall accidents, which may outweigh the benefits of roof bolting and discredit an innovation in roof control that shows great promise of materially reducing our mining accidents. From an economic standpoint it may represent the margin between profit and loss in many mining operations. The purpose of this manuscript is not to propose an inflexible code or set of rules but to summarize the experience to date as a guide for those who have the responsibility for the installation and inspection of roof bolts. This experience consists of approximately 250 investigations of roof failure in which roof bolting was involved either directly or indirectly. It should be pointed out that many of these failures were controlled, occurring during experimental periods, and comparatively few of the accidental failures actually resulted in personal injury, yet a significant number represented potential hazards.

Jan 1, 1951