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By W. L. EGY, GEORGES. RICE, L. M. JONES, J. K. CLEMENT

This report has been prepared, not only for the purpose of recording the results of the first series of coal-dust tests conducted in the experimental mine of the Bureau of Mines, but also to place before the mining public a description of the mine and an account of the objects sought in its establishment. Soon after the organization of the technologic branch of the United States Geological Survey, J. A. Holmes, then chief of the branch, concluded that for the solution of various problems relating to the causes and prevention of mine explosions it would be best to carry on large-scale tests in a mine rather than in a surface gallery. The idea of utilizing the underground passage of a mine for making explosion experiments did not at' first meet with general approval among investigators in this country or abroad. Many thought a mine passage was not a proper place in which scientific tests could be conducted, as great difficulty in controlling conditions was expected. However, after all arguments for and against such an investigation had been carefully considered, plans for opening an experimental mine were definitely adopted by the Bureau of Mines in 1910, and an allotment of funds was made to carry out the project. The first endeavor was to find an existing mine suitable for the purpose, but the mines offered by owners were either worked out, were wet, had poor roofs, or presented complications of various kinds, so that it was finally decided to open a mine if a site could be obtained having natural conditions that would fill the various requirements. A most desirable location was found on property of the Pittsburgh Coal Co., near Bruceton, Pa. The president of this company, Mr. W. K. Field, the general manager, Mr. G. W. Schluederberg, and the chief engineer, Mr. E. J. Taylor, rendered every possible service in

Jan 1, 1913

By C. H. Schack

Extractive metallurgy techniques currently employed to recover silver from primary ores and secondary scrap were reviewed and evaluated to identify and delineate metallurgical problems whose resolution would increase the supply of silver from domestic materials. The survey revealed that practically all primary silver is recovered by froth flotation concentration of various types of ores, followed by smelting and refining of the separate lead, copper, and zinc concentrates. Silver losses during the complex processing are, with rare exception, inconsequential. Furthermore, any silver production gain from base metal ores, which contribute about two-thirds of the total primary silver, is directly dependent in improvement in the market for the base metals. Statistical data on new and old silver scrap are wholly inadequate to make reliable conclusions about scrap processing problems and the possibility of increasing the recovery of silver from the many forms of secondary silver- bearing materials. The available information indicates (1) that efficient silver reclamation practices are employed by the larger users of silver, and (2) that recovery of additional secondary silver involves solution of problems of collection rather than of processing. Several possibilities exist for limited increases in silver production from primary ores by improvement in metallurgical practices. Specifically, research is needed to (1) solve the problem of recovering silver from the copper ores of the Copper Range district, Michigan; and (2) devise economically feasible methods for recovery of silver from presently marginal or submarginal ores that because of grade, location, and frequently complex nature cannot presently be exploited by conventional techniques.

Jan 1, 1965

During the hydrometallurgical processing of the major base metals Cu, Zn, Ni and Co, the presence of iron is normally a serious complication, and iron separation from the pay metals usually constitutes one of the main challenges for the metallurgist. There are many instances, however, where the presence of iron is beneficial, or is even required. Two cases are presented where iron is required during the processing of base metals. The first example deals with the use of ferric sulphate to oxidize sulphides, more particularly copper and zinc sulphides, under atmospheric conditions. The results presented confirm that ferric ion leaching is efficient, particularly when the oxidant is regenerated during the process. The second case is the use of iron to solubilise refractory cobalt oxide minerals; examples, including pilot plant results, are presented for various ores from Africa and Central America. In both cases, this paper reviews the basic concepts involved and provides details of their application.

Jan 1, 2006

By Andrew McGrath, Geraldine Lyons, Sarah Barcelona

In the dynamic and challenging modern industry landscape, understanding and unleashing the true role and contribution of technical teams is crucial to business success. The cyclical nature of industries has led to shifts in the technical professional’s place within the organization and the technical skills that are desired most. This paper reframes the pivotal role that technical professionals play within complex operating assets to maximize value and realize full potential. This investigation focuses on the Rio Tinto Kennecott Technical group’s cultural journey, which is underpinned by an investment in its people. The conflict between legacy industry beliefs and the necessity for cultural change emerges. This is illustrated by a deep dive into the evolving case study of Kennecott’s Bingham Canyon Open Pit Mine Technical team. Here, a multi-faceted approach to cultural change is helping to unlock the team’s contribution to the life extension of an aging asset. Guided by a vision and strategic roadmap, this approach is part way through a 5-year implementation period and is yielding encouraging business outcomes.

Feb 1, 2024

By O. C. Blade

The term "Ichtnyol" is a name applied loosely to certain preparations used in pharmacy. These preparations do not occur as such in nature but are manufactured by various chemical processes. Ichthyol is the name trademarked for a product manyfactured by the Irhthyel-Gescllschaft (Cordes Hermanni & Co.) of Hamburg, Germany, and marketed in thin, country by Merck & Co., Inc., (5, 86, 87)3/. Although used in the literature rather loosely, the correctly applied word refers to the product obtained by sulphonating and then neutralizing with ammonia a distillate from the oil retorted from a certain high-sulphur bituminous shale found near the village of Seefeld in the Austrian Tyrol. Due to the fact that fossils of fish and marine animals occur in the limestone associated with the bituminous shale, these deposits have long been known as, the "lchthyolite schistc of Seefeld" ( 55) . The Greek word "ichthys"" for fish and the Latin word "oleum" for oil are the words from which the term is derived. The crude, tarry shale oil, whose distillate is the raw material for the sulphonation process, has been referred to since the Middle Ages as "Dürsten" or "Tirschen" oil, and the term "ichthyel oil" has been used occasionally in the literature to designate the retorted crude oil (92, 93, 106, 117). The first application of the name "Ichthyol" to a particular product is credited to Schröter (35, 129). Various names for products manufactured by sulphonating bituminous distillates have been coined, and in some of these names the root from the word ichthys has been retained. Some of these names can be found in New and Nonofficial Remedies under the heading, Sulphoichthyolate Preparation, and Substitutes (5).

Jan 1, 1938

By S Worden, A Lee Zhi Yi, E Sellers, G Corder, A Littleboy

The global shift towards decarbonisation is driving competition for the extraction of critical minerals such as nickel, lithium, and copper. To meet this demand, new mines are being developed while mines approaching closure are being reimagined as sites of potential resources. This reimagining challenges how mine closure is being conceptualised. In the conventional case, when a mine reaches the end of its economic life, it is closed or put into care and maintenance until it transitions to the next land use, such as agriculture, native ecosystem corridors, solar farms or integrated eco – precincts (Murphy et al, 2019; Holcombe, 2020) (the authors acknowledge that unplanned mine closures have left a devastating legacy of contamination, safety and cultural heritage impacts). Extracting minerals from closed or closing mines will extend mine life and, therefore, delay relinquishment and transition. In this context, innovative technologies are needed to make mining economically viable. In the first year of her doctoral research on improving stakeholder engagement in mine transitions, Lee Zhi Yi has coined the term ‘mine life extension technologies’ (MLETs) to describe a class of technological solutions that optimise extraction of resources after a mine reaches the end of its economic life. Examples of MLETs include agromining (van der Ent et al, 2015), in situ recovery (Robinson and Kuhar, 2018), and reprocessing or reuse of tailings (Gou, Zhou and Then, 2019). MLET extraction offers several benefits compared with conventional mining processes, such as waste remediation, value recovery of minerals, a smaller footprint and less environmental impacts (Sellers, Picorelli and Salmi, 2022). What requires further investigation is the consequences of MLET implementation to host communities or community perspectives towards the proposed technology and subsequent delays in transition.

Aug 2, 2023

By O. Bazhko, F. D. L. Uahengo, Y. R. S. Hara

Although the conventional acid-reductive leaching method effectively extracts copper (Cu) and cobalt (Co) from Cu–Co oxide ores, efforts to enhance hydrometallurgical performance are ongoing. This study evaluates the influence of sulphuric acid (H2SO4) and sodium metabisulphite (Na2S2O5) on metal extraction from Zebesha Cu–Co oxide ore using ferrous sulphate heptahydrate (FeSO4·7H2O) and ferric sulphate (Fe2(SO4)3) as lixiviants. Ore samples (<150 μm) were leached at ambient temperature for two hours, and metal concentrations were determined via X-ray fluorescence analysis. In the FeSO4·7H2O system, Co, Mn, and Ni recoveries increased w=ith Na2S2O5 concentration, reaching a maximum of approximately 80% Co at 150 kg/t, while Cu recovery remained below 5%. Conversely, with Fe2(SO4)3, Cu recovery peaked at 88% at 50 kg/t Na2S2O5, then declined to 79% at 150 kg/t. The addition of H2SO4 improved metal recoveries in both systems. Notably, 60 kg/t H2SO4 yielded 92% Cu extraction in Fe2(SO4)3, while Co, Ni, and Mn remained below 40%. However, in FeSO4·7H2O, Co recovery improved from 40% to 84%. These findings suggest Na2S2O5 is more effective for cobalt extraction with FeSO4·7H2O, whereas H2SO4 enhances copper extraction in Fe2(SO4)3.

Oct 24, 2025

By Joan Weinberg

The economy continued to expand during the third quarter, as real GNP rose at a seasonally adjusted annual rate of 3.8%, up from 2.5% in the second quarter (table 1). Continued job gains (see below), higher incomes, and an increase in installment debt, resulted in a nearly 20% increase in consumer spending on durable goods. Consumer expenditure on nondurables fell slightly, while spending on services continued at a moderate pace. Nonresidential fixed investment climbed nearly 24%, as producers purchased more durable equipment. Residential fixed investment was adversely affected by rising interest rates, which slowed new home construction from January to August, 1987 to a rate 11.2% below a comparable period in 1986. Net exports of goods and services deteriorated slightly, after three consecutive quarters of improvement. The volume of net exports has risen 15% for the year, contributing to economic and employment growth, but large price increases on imports have slowed the improvement in the nominal trade balance. Although U.S. goods have declined in price relative to foreign goods because of the devaluation of the dollar, faster growth in exports is hampered by austerity programs in developing countries, and emphasis in Germany and Japan on curtailing inflation and fiscal deficits.

Jan 1, 1987

By S H. Begg

There is strong evidence that many major oil and gas (O&amp;G) projects are plagued by large cost and schedule overruns, or significant underperformance in productivity. Similar evidence exists for large mining projects. This paper claims that uncertainty is the underlying reason why projects fail to deliver the metrics used to justify their investment, or to deliver the economic value possible if alternative decisions had been made.Most technical and economic analyses are performed to reduce uncertainty to help make decisions. Decision-making is about ranking alternatives and choosing the best; rarely are precise predictions required, if this is even possible. Better uncertainty assessment is one of the keys to better decisions, thus better business outcomes. To get better decisions it is suggested that the focus or reward/penalty incentives be shifted away from the quality of outcomes to the quality of decisions. High-quality decisions are those that are generated from the skilled use of the tools, methodologies and processes from the discipline of decision analysis.Uncertainty is quantified by probability, which is a degree of belief in the truth/falsity of some proposition about a quantity relevant to a decision, such as volume of in-place resource, future price or action of a competitor. The probability a person ascribes to a proposition depends upon their information set; hence probability is subjective – it is not an inherent attribute of the quantity of interest or the physical system.The above simple observations have profound implications for modelling approaches, how they deal with uncertainty, the use of data to help assess uncertainty and the reliability of information provided by subject-matter experts. The limited circumstances under which frequency data (from spatial or temporal variables) can be used to assign probabilities is also reviewed.People, in general, are subject to a range of biases and cognitive errors. Research with O&amp;G subject-matter experts shows that their expertise offers little or no protection from making errors in probability assessments and other judgements.CITATION:Begg, S H, 2016. Decisions, decisions – uncertainty, variability, modelling and psychology, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 9–18 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Bernard Lewis

This report summarizes the fundamental research and technical studies conducted by the Explosives Branch of the Bureau of Mines from July 1, 1943, to June 30, 1949. It is the thirteenth of a series of annual reports, which have aimed to bring to the reader a resume of the research results that have appeared in published form during each fiscal year. The work of the Explosives Branch covers a number of activities - explosives research, explosives testing, flame and combustion research, flammability of gases and vapors, dust-explosions research, and technical studies in the experimental mine. An important part of the work of the branch is fundamental research to advance our knowledge and understanding of explosion processes. Considerable emphasis has been placed on studies of ignition and flame stabilization, as it is felt that an understanding of these processes should assist materially in alleviating explosion hazards in coal mines. The results are also finding important application in the development of jet propulsion. Studies of the explosibility of gases, vapors, and dusts saving thousands of lives and are preventing the destruction of much property. In innumerable instances in which potential explosion hazards exist, safe operating procedures have been recommended from data taken in the Laboratory. Aware of the value to national security of research results of combustion, flame, and explosion, the Army, Navy, and Air Forces are actively supporting important phases of this fundamental research.

Jan 1, 1950

By Willard C. Lacy

A mining operation begins with prospecting and exploration-stages with long periods of investment and high risk of failure. However, success in exploration ultimately determines survival of the mining industry. Prospecting and exploration may discover evidence of a mineral occurrence and outline its size and character, but ore deposits that support mining are "made" through the collective efforts of project geologists, geophysicists, geochemists, metallurgists, engineers, chemists, lawyers, and even politicians (Joralemon, 1975). Some deposits may go through multiple cycles of rejection and recommendation, discovery and development, decline and abandonment, rediscovery and development, etc., as economic, technological, or political conditions change or geologic understanding is improved. Peters (1987, p. 233) graphically illustrates the normal life cycle of a mine and the position of exploration in the cycle (Fig. 4.0.1). During the past fifty years, mineral exploration has evolved from comparing evidence of mineralization of prospects with that of known deposits to a more quantitative science employing many facets of geochemistry, geophysics, multispectral sensing from space, computer data storage, analysis, modeling, and most importantly, a better understanding of ore genesis. This modem approach to exploration began in the late 1940s and continues to develop. Exploration efforts peaked in the 1960s with emphasis upon the search for porphyry copper deposits, Mississippi Valley lead-zinc deposits, and volcanogenic massive sulfide copper-lead-zinc deposits. It peaked again in the middle and late 1980s with emphasis upon micron-size disseminated gold and epithermal and stratiform precious metal deposits.

Jan 1, 2008

By Sandra K. Zacharias

Brass, a deliberate alloy of copper and zinc, has been known since before Roman times. There are two main methods of making brass: (1) Cementation or calamine process - crushed zinc ore (calamine, ZnC03 , or calcined calamine, ZnO), is mixed with charcoal and small pieces of metallic copper and heated to about 900°C in a closed crucible, (2) Alloying - metallic copper and zinc are melted together in a reverberatory furnace. According to most modern authorities (e.g. Smith and Forbes 1955), the calamine process was the only one used in western Europe prior to the 18th century. At that time, the alloying technique began to take over, because metallic zinc was successfully produced on a large scale for the first time. Previously, this had been a problem because zinc vapourizes at 906°C or about the same temperature at which it can be reduced from its ore. Thus, some means had to be devised to collect and condense the zinc vapour (Tylecote 1976). Metallic zinc was known, however, earlier than the 18th century A.O. Several early finds have been made, including a rolled sheet of metallic zinc found in excavations at the Athens Agora dating to the 3rd to 2nd century B. C. (Farnsworth et al. 1949). The Chinese were producing zinc by at least the 10th century A. D. and, by the 17th century, Chinese zinc ingots were being imported into Europe by the Dutch East India Company (Needham 1974). Metallic zinc is also mentioned in several European documentary sources from the 16th century (e.g. Paracelsus, Agricola). This study traces the changes in Western brass making methods from Classical to Renaissance times by examining documentary and archaeological evidence.

Jan 1, 1999

By John D. Rockaway

Failure of the mine floor supporting coal pillars frequently occurs when the subcoal strata include "underclays" or other low strength strata. The failure process has been studied to define the response of these materials to applied coal pillar loads and to determine the applicability of bearing capacity analysis to evaluate unsafe conditions. The study has been accomplished through an investigation of both the intact and insitu geotechnical properties of the subcoal strata and through the installation of floor movement monitoring instrumentation. The results of these studies have indicated that both the shear strength of the underclay and the stratigraphy of the subcoal strata must be considered in the analysis. The shear strength was the major controlling factor determining the ultimate load carrying ability of the materials, but the thickness and stratigraphic position of the weak layers influenced the mechanism of the failure process. The methods of bearing capacity analysis were used to define pillar stability that included provisions for taking into consideration a two-layer system. Conditions assumed for a coal mine where a weak underclay overlies firmer strata. The results of the analysis compared very well with observed mine conditions, indicating marginal conditions in areas of the mine which later experienced pillar support failure. In addition, a "heave factor" was derived to predict potentially unstable floor conditions in the mines studied in detail.

Jan 1, 1979

A unity of viewpoint emerged from the workshop. The concept that transmission is via characteristic modes was a common theme in many of the presentations. Also, the confusion an the meaning of monofilar and bifilar to describe these dominant modes was cleared up. But, there was still a healthy divergence of opinion on what constitutes an optimum system. It was generally agreed that further analytical and experimental work is definitely needed. In particular, it was stressed that independent measurements of the constitutive properties of the electromagnetic environment are needed. Also, there was considerable concern that laboratory measurements of rock samples could lead to misleading results for the effective conductivities. Also, there was a general recognition that over simplified propagation theory should not be used to interpret field data. From a theoratical and practical point of view, it was realized that mode coupling plays a vital role in the transmission channel. One must not only understand which and how many propagation modes are excited by the transmitting antenna, but the conversion of energy from one mode type to another must be accounted for. This conversion can either be done intentionally (by fixed mode convertors) or non intentionally (by random wall roughness). In fact, mode conversion can be quite complicated when various propagation paths exist such as when insulated cables, leaky feeders, grounded rails, coal seams, etc. all convey portions of the electromagnetic energy. However, this state of affairs should be regared as an. opportunity for extended communication coverage in mines rather than a limitation of a desig. procedure based on preconceived notions of the dominant propagation mechanism.

Jan 1, 1978

By W. F. RITTMAN, E. W. Dean

This report presents the results of an investigation conducted by the Bureau of Mines for the purpose of assisting in the establishment of a satisfactory standard method for the analytical distillation of petroleum, a problem of great importance to the petroleum industry. Experiments were performed for the purpose of studying the charac- teristics of methods typical of those in use; comparative studies were made of the efficiencies of the principal types of fractionation ap- paratus available to the petroleum chemist; and the characteristics of a type of apparatus that the results of the experiments seemed to indicate was best adapted to the purpose were investigated in detail. Also, some experiments were made to determine the effect of cracking as a factor in the analytical distillation of petroleum in still heads.

Jan 1, 1916

The U.S. economy continued to expand during 1986, although at the slowest pace since 1982 when the current business expansion began. Real gross national product (GNP) grew about 2.6%, slightly below 1985 growth but significantly below that of 1984. The continuing expansion was fueled pre-dominantly by rising personal consumption expenditures as well as growing Government purchases of goods and services. Fixed investment, although positive, failed to grow at the rate of the overall economy. The trade deficit, which increased more than 30% over the record 1985 level, continued to depress economic growth despite significant declines in the price of petroleum and the value of the dollar. On a more positive note, domestic employment continued to grow--increasing over 2 million from the 1985 level--and inflation and interest rates declined. The unemployment rate dropped slightly to 7.0%. Of direct importance to the mineral-producing industries, expenditures for consumer and producer durables as well as investment in residential construction each grew faster than the overall economy, but investment in nonresidential structures fell more than 10% from the 1985 level. The level of real capital spending declined about 3% in 1986, following strong gains in 1985 and in 1984. Capital expenditures for new plant and equipment bottomed out in the second quarter and expanded in the third and fourth quarters. The decline in the first half of the year was partially attributed to uncertainty arising from the then-proposed tax bill. Also, there was little impetus for corporations to invest in new capacity since factories were operating at less than 80% of capacity during most of the year, in part because of continued competition from imports.

Jan 1, 1986

By A. E. Wraith, J. Protheroe Jones, P. J. Mackey

The world’s first copper electrorefinery started production in 1869 at Burry Port in South Wales. Built within the Pembrey Copper Works which had commenced smelting operations in 1849, the new refinery was based on principles described in the British patents issued to J.B. Elkington in 1865 and 1869. Refining principles and practices pioneered there were key to the foundation of modern electro-refining practice in what is now a dominant international industry producing over 16 Mt of electrical grade copper annually. This paper explores the background to this pioneering application of the new, early 19th century, science of “electro-metallurgy” and examines its links to the contemporary decorative electro-plating industry and to the shortcomings of 19th century fire refining. The beginnings and early years of the Pembrey electrorefinery are briefly discussed in relation to the quality, applications and pyrometallurgy of copper at the time. More than a decade would elapse before the birth of the electrical age: the Pembrey refinery may be seen as one of its vital precursors. Note: This paper was originally published as part of the Copper 2013 proceedings (A.E. Wraith, P.J. Mackey and J. (formerly R.) Protheroe Jones, “Origins of Electrorefining: Birth of the Technology and the World’s First Commercial Electro-Refinery”, paper in Electrorefining, Vol. V, Book 2, (Eds. R. Abel and C. Delgado), Cu 2013 International Conference, pp. 19-33, IIMCh, Santiago, Chile, 2013). It is reproduced here together with a new Appendix and supporting references that lists the year of commencement of the first electrolytic copper refinery by country, 1869 to 1956. It all, the year of the first electrolytic copper refinery established for 15 countries is included. These 15 countries now produce more that 70% of world refined copper (for 2018). INTRODUCTION In the 1840s, the new science of ‘electro-metallurgy’, a term coined by Smee in 1841 (Smee, 1841), was being adapted to the decorative electro-deposition of silver in a thin, bright adherent coating that was evidently equal in appearance to traditional silverware (Williams, 1976). Chief among innovative manufacturers of decorative objects who took up the new art of silver electro-plating was the acclaimed firm of G.R. Elkington and Co. of Birmingham, England. The company, which vigorously developed all aspects of electro-metallurgy for the decorative trade, entered the field of ‘electrotyping’, a technique in which the surface features of a mould are copied on an electro-deposited copper layer which, when stripped off, can be used to reproduce an imprint of the mould. In essence, it is a form of casting by electrodeposition, invented in 1837 independently by Jacobi in Russia (Pavlova, 1968) and Spencer in England (Wyatt, 1851).

Jan 1, 2019

By N. R. Paterson, D. G. MacKay

"The geology of the Mattagami mining camp, while of particular economic significance, is unfortunately obscured by a very thick mantle of overburden. For this reason geo-physical methods have been relied upon heavily in exploring the area. Geophysical data over five important sulphide discoveries show how targets are selected for drilling and how effective geophysics has been in assisting subsequent development programs."

Jan 1, 1960

The mineral Industry, following the economy as a whole, experienced little growth in 1992. However, with modernized plants, efficient workforces, and lower operating costs, the industry is well positioned to take advantage of possible improvement in the national economy during 1993. In addition to the significant 1992 events highlighted below, important events, trends, and issues within individual mineral industries are addressed in the commodity sections that follow. The value of processed materials of mineral origin is estimated to have been about $310 billion in 1992. The value of U.S. raw nonfuel minerals production in 1992 is estimated at approximately $32 billion, a 3% increase over 1991. The value of domestic minerals production has increased in all but 4 of the last 32 years.

Jan 1, 1993

By E. E. White

(Cleveland Meeting, October, 1912.) IN, August, 1911, I read a paper before the Lake Superior Mining Institute&apos; on surveying and sampling diamond-drill holes. The present paper gives a more thorough description of these methods, together with a few changes and notes suggested by further experience. Since August, 1911, the methods, used constantly by the Cleveland-Cliffs Iron Co., have been developed to a higher degree of efficiency, and have given great satisfaction. Until a few years ago but little attention was paid to the determination of the actual course of drill-holes, to the accurate sampling and analysis of the material, or to the scientific location of the drill-holes. It has now been common practice for several years in many districts to test the inclination of drill-holes by etching glass tubes with hydrofluoric acid, but the direction of deviation from the vertical has not often been determined. Methods of determining the direction by means of a compass were first developed in connection with drilling in Victoria. The latest method used on the Rand in South Africa has been recently described by John I. Hoffman.2 In the same paper Mr. Hoffman describes an ingenious method of wedging-off a drill-bole so as to start new holes at several successive points. By this means a hole can be deflected in any desired direction, and the curvature can be controlled to a considerable extent, provided the rock is soft enough to permit the hole to be wedged off. Unfortunately, in the Lake Superior district, the jasper iron-formation is so hard that it is very difficult, if not impossible, to do this. I tried to deflect one hole so as to avoid drill-rods stuck in the hole, by using a 1 Proceedings of the Lake Superior Mining Institute, vol. xvi., pp. 100 to 120 (1911). 2 Recent Practice in Diamond-Drilling and Borehole Surveying, Bulletin No. 91, Institution of Mining and Metallurgy (Apr.. 11, 1912).

Nov 1, 1912