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By C. Harry Benedict

This paper presents the details of milling practice and costs at the conglomerate mill of the Calumet & Hecla Consolidated Copper Co., Lake Linden, Mich., and is one of a series on milling methods being published by the Bureau of Mines. GENERAL DESCRIPTION The mines of the Calumet & Hecla. Consolidated Copper Co. are located in the Keweenaw Peninsula of northern Michigan. The mines of this district lie in a belt not over 4 miles wide and 100 miles long, which contains more or lees commercial ore. The Calumet & Hecla properties are the farthest north, except for the Seneca, of the operating mines. The district borders on Lake Superior, and by means of the Portage and Torch Lake waterways the largest lane vessels, can transport coal and other supplies from the lower Lakes directly to the company docks.

Jan 1, 1930

By Quansheng Li

Large-scale coal mining will cause environmental problems such as aquifer damage, land excavation and occupation, soil erosion, vegetation damage, and regional landscape damage. The existing coal mine environmental restoration technology is relatively simple, and there is a lack of systematic research on environmental total factors. Based on the mechanism of coal mining damage and the laws of environmental natural succession, the concept of “coal environmental protection mining” is proposed, which combines damage reduction mining and environmental element system restoration. In accordance with the environmental protection principle of “source protection, process damage reduction, and systematic restoration,” a technical system of “coal environmental protection mining” is constructed for the two types of mining damage scenarios: underground mining and open-pit mining. In view of the damage characteristics of underground mining, source environmental protection technology based on optimization of mining process parameters, stability maintenance and damage reduction technology for overlying rock bearing arch shell structure, zoning and time-sharing treatment of surface cracks, and direct drainage irrigation technology for mine water have developed. In accordance with the damage characteristics caused by open-pit mining, land-saving and source reduction damage technology, near-natural stratigraphic reconstruction, topsoil improvement, and environmental storage and utilization technologies for seasonal precipitation have developed. By applying the technology in this paper, the maximum surface settlement value of 12401 working face in Shangwan coal mine was relatively reduced by 25%, the surface cracks have been adjusted from step-type cracks to dynamic small cracks, and since the technical implementation of the Shendong mining area in 2010, the vegetation coverage has increased loss and crushing decreased by 0.06 km2 every year, the environmental restoration period of the dump site was advanced by more than one year, and the vegetation coverage rate increased by 41.78% compared with the background value in the semi-arid area of the victory open-pit coal mine demonstration area. A surface reservoir with a water storage capacity of 400,000 cubic meters has been built, and the seasonal and graded utilization of mine water has been realized. An underground reservoir with a water storage capacity of 1.22 million square meters has been built in the Baorixiler open-pit coal mine.

Jun 25, 2024

By Creelman C. A

The removal of a horizontal piIlar between Nos. 9 and 11 levels (1,116 feet from the collar of main shaft) was successfully carried out by blast hole drilling, and, to the best of the authors' knowledge, this mass blast of 40,000 tons of ore (requiring the use of 7,150 Ibs. of explosive and 5,385 feet of primacord) was the first occasion on which a task of this magnitude has been carried out underground in an Australian mine.Blast hole drilling was introduced by this company approximately fifteen months ago at New Cobar Mine in sub-level stoping.This experimental drilling and blasting gave very valuable information as to the correct technique to be adopted when the final plans were being prepared for the removal of the horizontal pillar at New Occidental Mine.The dimensions of this pillar were approximately 15 feet long, and from 40 to 60 feet wide, and 65 feet in depth.The block of ore extended to 35 feet above the level and 30 feet below, the upper section being partially excavated to form the bell-hole floor and grizzly chambers used for drawing off the broken ore in the shrink stope above the No. 10 level.Description of Ore-bodyThe main ore-body is situated almost vertically in a well-defined shear zone at the junction of sandstone and slate, the sandstone forming the eastern and the slate the western wall.The ore-body consists of highly silicified slate (chert) sparsely impregnated with sulphides, containing a small percentage of copper and bismuth.The total length of the ore-body is approximately 450 feet, with a maximum width of 60 feet in the main section, which is about 200 feet long.This is the section shown in longitudinal and cross-section (Fig. 1).The ore-body is divided by a horse of mullock in the northern end into two legs, the eastern and western, which are approximately 250 feet long and averaging 25 feet in width.This ore-body is strong, hard and abrasive with extremely strong walls, an ideal proposition for open stoping and mass blasting.MiningIn all levels above No. 9 the cut and fill method of ore extraction was adopted. On Nos. 10 and 11 levels the shrinkage method was introduced with economical results, and no difficulty had ever been experienced with shabby or bad walls.Shrink stoping had been carried upwards from No. 11 level to within 10 feet of No. 10 level, when mining hazards developed, and instead of...

Jan 1, 1944

By Tim O’Neil

More than 5,300 mining professionals from around the world attended the SME Annual Meeting and Exhibit, March 1-3 in Denver, CO. Seventy three technical sessions highlighted innovative technologies and applications for the development of mineral resources. And the exhibit featured 421 companies worldwide and 632 exhibit booths. The 1999 SME Annual Meeting had 10% international attendance. Professionals from outside the United States were guests at the first SME International Reception.

Jan 1, 1999

By S. X. Liang

In China, the bearing capacity predictions of the pile with Stress-Wave Theory have been developed rapidly in recent years. This paper recommended a DZH-3 Pile Driving Analyzer and its relevant computer programs. Taking Qinghai Hotel Project for example, it gave their applications in the dynamic tests of large diameter cast-in-place piles.

Jan 1, 2010

By John Wulff, Robert Kamm, Steinberg Morris

In powder metallurgy it has often been observed that shrinkage may occur in one direction and growth in another during sintering. Even in long-time sintering experiments the rate of shrinkage may be different in different parts of the compact. In the fabrication of some parts requiring a constant permeability it is even questionable in some cases whether pressing from one direction should be attempted. These observations require for their interpretation a more detailed study of green or pressed density than has heretofore been available. Usually average density measurements of the whole compact are made and in some cases carefully cut sections are measured. A different approach to the problem was first mentioned by Rakowskil and also used by Balshin.2 Balshin's diagram is reproduced in Fig I and schematically shows the result of pressing three layers of metal powder with fine intervening layers of graphite. The retarding effect of the die walls and a qualitative example of the density distribution is evident. More quantitative information about the distribution of density within a cold-pressed powder compact would be useful in showing the variation in density in as as influenced by the type of poKder, shape of die, lubricatioll during the process, and other variables. Furthermore, information about the cracking of cold-pressed compacts may be obtained from an analysis of the stress distribution within a, powder compact, and some information about the stress distribution can be obtained in turn from the derlsity and strain distributions. A more detailed report on some of the present experiments appears in reference 3. Present Investigation In order to ascertain the density gradients in cold-pressed metal powders, a deformable lead grid within the powder was employed. After pressing in cylindrical di" the ejected compact was radiographed, giving a pattern of the deformed grid. From the radiograph density and deformation from point to point is readily measured. From the radiograph strain distribution and stress trajectories were also determined. The latter also permits the determination of the coefficient of friction at the die wall. This technique indicates that the densest Part of a compact pressed from one side is at the top outer circumference and the least dense region at the bottom circumfercnce near the stationary plunger. For Some heights of compacts the density at the axis is such that the lower density is at the top rather than at the bottom. SO irregular a density distribution is due primarily to die-wall friction. As the ratio - diameter to height of compact is increased the die walls play a correspondingly smaller role. More uniform density

Jan 1, 1947

By John Wulff, Steinberg Morris, Robert Kamm

In powder metallurgy it has often been observed that shrinkage may occur in one direction and growth in another during sintering. Even in long-time sintering experiments the rate of shrinkage may be different in different parts of the compact. In the fabrication of some parts requiring a constant permeability it is even questionable in some cases whether pressing from one direction should be attempted. These observations require for their interpretation a more detailed study of green or pressed density than has heretofore been available. Usually average density measurements of the whole compact are made and in some cases carefully cut sections are measured. A different approach to the problem was first mentioned by Rakowskil and also used by Balshin.2 Balshin's diagram is reproduced in Fig I and schematically shows the result of pressing three layers of metal powder with fine intervening layers of graphite. The retarding effect of the die walls and a qualitative example of the density distribution is evident. More quantitative information about the distribution of density within a cold-pressed powder compact would be useful in showing the variation in density in as as influenced by the type of poKder, shape of die, lubricatioll during the process, and other variables. Furthermore, information about the cracking of cold-pressed compacts may be obtained from an analysis of the stress distribution within a, powder compact, and some information about the stress distribution can be obtained in turn from the derlsity and strain distributions. A more detailed report on some of the present experiments appears in reference 3. Present Investigation In order to ascertain the density gradients in cold-pressed metal powders, a deformable lead grid within the powder was employed. After pressing in cylindrical di" the ejected compact was radiographed, giving a pattern of the deformed grid. From the radiograph density and deformation from point to point is readily measured. From the radiograph strain distribution and stress trajectories were also determined. The latter also permits the determination of the coefficient of friction at the die wall. This technique indicates that the densest Part of a compact pressed from one side is at the top outer circumference and the least dense region at the bottom circumfercnce near the stationary plunger. For Some heights of compacts the density at the axis is such that the lower density is at the top rather than at the bottom. SO irregular a density distribution is due primarily to die-wall friction. As the ratio - diameter to height of compact is increased the die walls play a correspondingly smaller role. More uniform density

Jan 1, 1947

By Morris Steinberg, John Wulff, Robert Kamm

IN powder metallurgy it has often been observed that shrinkage may occur in one direction and growth in another during sintering. Even in long-time sintering experiments the rate of shrinkage may be different in different parts of the compact. In the fabrication of some parts requiring a constant permeability it is even questionable in some cases whether pressing from one direction should be attempted. These observations require for their interpretation a more detailed study of green or pressed density than has heretofore been available. Usually average density measurements of the whole compact are made and in some cases carefully cut sections are measured. A different approach to the problem was first mentioned by Rakowski1 and also used by Balshin.2 Balshin's diagram is reproduced in Fig r and schematically shows the result of pressing three layers of metal powder with fine intervening layers of graphite. The retarding effect of the die walls and a qualitative example of the density distribution is evident. More quantitative information about the distribution of density within a cold-pressed powder compact would be useful in showing the variation in density in compacts as influenced by the type of powder, shape of die, lubrication during the process, and other variables. Furthermore, information about the cracking of cold-pressed compacts may be obtained from an analysis of the stress distribution within a powder compact, and some information about the stress distribution can be obtained in turn from the density and strain distributions. A more detailed report on some of the present experiments appears in reference 3. PRESENT INVESTIGATION In order to ascertain the density gradients in cold-pressed metal powders, a deformable lead grid within the powder was employed. After pressing in cylindrical dies the ejected compact was radiographed, giving a pattern of the deformed grid. From the radiograph density and deformation from point to point is readily measured. From the radiograph strain distribution and stress trajectories were also determined. The latter also permits the determination of the coefficient of friction at the die wall. This technique indicates that the densest part of a compact pressed from one side is at the top outer circumference and the least dense region at the bottom circumference near the stationary plunger. For some heights of compacts the density at the axis is such that the lower density is at the top rather than at the bottom. So irregular a density distribution is due primarily to die-wall friction. As the ratio of diameter to height of compact is increased the die walls play a correspond¬ingly smaller role. More uniform density

Jan 1, 1947

By Diego Ruben Martin

Este trabalho objetivou comparar, por meio de experimentos desenvolvidos em uma fundição, através da adição de três inoculantes diferentes (IM-22 com FeSi-Ba/Zr, G 20 com FeSi-Ba) e IMSR 75 com FeSi-Sr), para observar as características da vida util de ferramentas na usinabilidade das peças, microestrutura e propriedade mecânica. A metodologia da pesquisa se baseou em analisar principalmente pelo processo de fresamento o ferro fundido cinzento GG-25 inoculado diferentemente, denominado de acordo com a Norma DIN EN 1561. As formas de avaliação dos resultados terão como base uma análise quanto ao desgaste da ferramenta, acabamento superficial, análise microestrutural, composição química e propriedades mecânicas do material da peça. Os resultados mostraram que dentre os inoculantes aplicados o com Sulfeto de Estrôncio (SrS) apresentou-se mais estável termodinamicamente que as amostras inoculadas com os outros dois inoculantes, pois ele levou a uma variação da energia livre de Gibbs mais negativa e portanto mais favorável a formação de núcleos com raio crítico (rc) maiores, o que permitirá uma solidificação com nucleação heterogênea. Todavia o respectivo inoculante também foi mais eficiente na formação de uma microestrutura mais estável, com maiores quantidades de células eutéticas e vida útil do inserto mais longa quando usinado.

Aug 16, 2017

By W. J. Fene, J. J. Forbes

Through education, investigations, and studies and an expanded coal- mino inspection program the Bureau continued to dischargo the responsibility placed on it by Congress 39 years ago for promoting safety and health in the mineral industries. Although much still remains to be dono, definite progress was made in combating physical and psychological hazards in mines and plants. Accident-prevention cours os for coal-mine supervisory officials and special courses for coal-mine safety committeeman were inaugurated. First- aid, mine rescue, and other safety training was conducted for those engaged in all branches of the mineral industries. Assistance was given in recovery work after mine explosions and fires. Studies to reduce the danger of roof falls, the greatest single cause of fatal mine accidents, resulted in the development and adoption of new coal-mine roof-support techniques. Knowledge of the explosion and health hazards of mine and plant dusts and ways of pre-. venting them were advanced. Electrical equipment was tested for safety of operation in gassy coal mines, and emergency mine communications apparatus was developed and tested. More progress was made in the study of controlling flood waters that threaten life and property in the Pennsylvania anthracite region. More coal-mine inspections were made than in any previous year, and an impressive number of improvements resulted from the Federal inspectors' recommendations, even though many of them went unheeded. A program of con- trolling fires in inactive coal deposits on the public domain and private property was instituted during the year.

Apr 1, 1950

Ilmenite production in Western Australia commenced in 1956. There are now five producers, all in the Bunbury-Capel district, and current total production capacity is about 450,000 t.p.a.The deposits occur near the surface and average between 10 and 50 per cent heavy mineral. About 70-85 per cent of the heavy mineral is ilmenite. Other heavy minerals present include leucoxene, zircon, rutile, monazite, and garnet. The ilmenite contains 52-60 per cent Ti02. and is very low in chromium (0·03-0·04 per cent CrS03)Mining is done by sluicing, drag line excavation, or dredging. Primary concentration of the heavy minerals is achieved by spirals, revolving cones, or Reichert cones. After drying and screening, ilmenite is separated from the heavy mineral concentrate by various types of magnetic separator.Separate leucoxene, zircon, rutile, and monazite concentrates are also produced. Each plant uses a different technique and the processes used include chemical attritioning, screen plate electrostatic separation, high tension rolls, air tables, and dry launders.INTRODUCTIONThe treatment of beach sands in the Bunbury/Capel area for the extraction of ilmenite is a very recent development in the mining industry in Western Australia. Nevertheless, since the commencement of production in 1956, ilmenite has become the sixth most important mineral produced (Table 1).The increasing world recognition of Western Australia as a major producer of ilmenite (Table 2) is due primarily to the low chromic bxide content of the mineral (0' 03-0' 04 per cent Cr203), combined with a medium to high titanium dioxide content (54-60 per cent Ti02), supported by large reserves, a stable government, and close access to good shipping facilities. Ilmenite is. produced from these deposits at low cost which enables the industry to compete on world markets despite high rates for sea freights because of the distance from major markets.

Jan 1, 1965

By John D. Godfrey

Geological mapping on the Canadian Shield in northeastern Alberta outlined severalgranitoid rock massespotentially suitable as building stone. A particularly attractive prospect, the Chipewyan Red Granite, was subjected to an aerial survey and ground check. The petrologic and fracture characteristics critical for quarrying and use as a building stone were assessed in the course of detailed mapping at two of the most favourable sites. The extension of good rock was tested to shallow depths at one site by shallow diamond-drill coring. , The Chipewyan Red Granite displays a warm red colour, medium grain size and fairly massive texture, and takes a good polish. Deleterious geologic features studied in outcrop and subjected to structural analysis included regular joint systems, quartz veins, pegmatite dykes, basic shear zones and fault zones. Many of these key geologic features are systematic and hence predictable for stone quarrying purposes; other features, such as irregular fracelM tures, are non-systematic and arefar less predictable. The megascopic structural features studied show similar preferred orientations which appear to be collectively related to the tectonic history.

Jan 1, 1979

By J. Geertsma, F. de Klerk

During the hydraulic fracturing treatment of an oil or gas well the liquid pressure in the borehole is increased until tensile stress in the surrounding rock exceeds tensile strength. Once a tensile fracture is initiated, it is penetrated by liquid from the borehole and fracture propagation under continuous hydraulic action takes place. The fracturing liquid carries a propping agent to ensure a highly permeable flow channel after pressure release. Field results range from failure to obtain increased production to outstanding success. In all cases, however, it unfortunately remains uncertain whether the values chosen for the operational parameters, such as injection rate, pumping time and fluid viscosity, were in fact the ideal ones. Though experience provides a lead, a more satisfactory way to predict results would seem to be to subject the fracture propagation process to a theoretical analysis that (1) makes the maximum use of the relevant physical information and (2) so simplifies the resulting calculations that the field engineer gets practical data that he can handle comfortably. We are attempting here to do this in connection with the prediction of fracture width and areal extent before pressure release. What remains of the fracture afterwards depends on the distribution of the propping agent between the fracture walls, and that is a separate story. Idealization of the Problem To keep the problem tractable, a number of simplify- ing assumptions have had to be made: 1. The formation is homogeneous and isotropic as regards those of its properties that influence the fracture-propagation process. 2. The deformations of the formation during fracture propagation can be derived from linear elastic stress-strain relations. 3. The fracturing fluid behaves like a purely viscous liquid; i.e., any peculiar flow behavior due to the addition of gelling agents or other additives is neglected. Moreover, the effect of the propping agent distribution on the distribution of fluid viscosity in the fracture is not taken into account. 4. Fluid flow in the fracture is everywhere laminar. 5. Simple geometric fracture-extension patterns are assumed — either radially symmetrical propagation from a point source (Fig. 1A) or rectilinear propagation originating from a line source (Fig. 1B). In the first case the periphery of the fracture is circular, in the second case it is rectangular. 6. A rectilinear propagation mode can be accomplished only by injection over a large perforated interval, thus forming a line source. Such a rectilinear fracture must therefore be located in the vertical plane. A circular propagation mode might be expected from injection through a narrow band of perforations. This forms a point source. Because gravity effects are excluded from our considerations, the fracture propagation plane may in this case assume any angle with respect to the wellbore as far as the

Jan 1, 1970

By Juan Lizana

El presente trabajo describe el proceso del sistema de gestión estratégica en la mina San Rafael, Puno. En este sentido, la empresa como parte introductoria de sus operaciones, ha propuesto la solución integral, donde la herramienta principal son los índices de gestión por unidades estratégicas de negocio y los índices de gestión por unidad operativa, los mismos que permitirán evaluar el desempeño de su organización frente a sus metas, objetivos y responsabilidades. En este sentido, el establecimiento de este sistema busca crear una cultura en la organización, a través del seguimiento de cada uno de los índices, permitiendo a la alta gerencia y a los demás niveles ejecutivos de la empresa hacer control de gestión, así como una reducción de los costos operativos en el Área de Mina y mejoras en los resultados de voladura.

Sep 12, 2005

By Miguel Cochachi, Wilson Chavez, Germán Sovero

El presente trabajo está enfocado en recuperar los metales como plata y plomo de las escorias, mediante el proceso metalúrgico de lixiviación ácida/super ácida y flotación. Estas escorias son pasivos ambientales generados en los años 80’s, JS Consulting en el área de investigación metalúrgica desarrollo el proceso de lixiviación y flotación para lograr recuperar la Ag y Pb de las escorias y de esta manera darle valor en el mercado de dicho material que no tenía valor. Los resultados obtenidos fueron muy favorables, en la lixiviación de las escorias se logro separar hierro, silice, zinc, cobre de la plata y plomo, estos dos últimos elementos quedaron en el solido logrando una concentración comercialmente en el mercado.

Sep 29, 2023

By Jane Li, Kevin Tom

"Research has shown that broken rock on conveyor transport systems can contribute upwards of 50% towards the overall heat load in underground mines. However, few studies have made significant efforts to predict the temperature distribution of the ore and air simultaneously, which can help implement heat management strategies. The present investigation explores a transient, analytical heat transfer model to track ore-pile temperature distributions, along conveyor systems in an example underground mine. Production rate, ambient conditions, ore pile thickness and belt velocity are adjusted to evaluate the effect on dry and wet bulb temperatures.INTRODUCTIONWith an ever increasing demand on Earth’s resources due to a multitude of factors like population growth and step changes in technology, pressure on the mining industry to bring out more ore with improved margins is a persistent challenge. Typically, high-volume producing mining methods (i.e., exceeding 5000 tons per day (tpd)) such as sublevel and block caving, room and pillar, and longwall shall utilize belt conveyors instead of trucks as the primary haulage method to surface to save on operational costs (de la Vergne, 2014). However, studies have shown that when such material transport systems are installed at mine depths with virgin rock temperatures (VRT) above 40oC, the heat dissipated by the conveyed ore can account for over 50% of the underground heat-load (Pareja, 2000; Bluhm, Jones, Moreby, & von Glehn, 2012; van den Berg, Moreby, & Kok, 2015).Unlike other types of heat sources encountered in underground mines, such as diesel machines, strata, electrical devices, and autocompression, heat transfer by conveyed broken rock is much more difficult to estimate. The seminal work of McPherson (1993) states that broken rock heat transfer is a function of its surface area, and the air’s psychrometric condition. It is additionally a function of the VRT, its specific heat, production rate, heat transfer coefficient and the residence time (Bossard, 1997; Ross, Tuck, Stokes, & Lowndes, 1997). Consequently, few studies have attempted to analytically quantify the significance of ore heat flow."

Jan 1, 2019

By A. M. Gaudin, J. H. Brown

In a survey of the effects of heat treatment on the comminution of various rocks, it was found that unusual size distributions often characterize the broken products, and that this is related to a great increase in intergranular fracture1. It is the purpose of the present paper to contribute to an understanding of this effect. In a thesis by one of use, critical consideration was given to many mechanisms which could conceivably be responsible for the increased intergran-ular fracture. It was shown that neither gross chemical changes nor intergranular corrosion are required. Among non-chemical mechanisms the most likely appeared to be (1) Uneven expansion due to thermal gradients, giving spalling (2) In a manner similar to that prevailing in metals, the appearance at high temperature of intergranular weakness. (3) Unequal thermal expansion of adjacent grains. Experiments were designed and conducted to permit a choice among the many alternative mechanisms and in particular among the three listed here. EXPERIMENTAL MATERIALS Tests were made on the materials listed in Table 1. Of each material, only lumps similar in composition and grain size were used. The three marbles listed in Table 1 were analyzed to assure that their chemical compositions did not differ greatly (Table 2). On the basis of the chemical analyses, of differential thermal analyses, and of X-ray powder diffraction patterns, it appeared that the marbles were very similar except for their grain sizes.

Jan 1, 1961

By Peter Faust

The foundations for the new South Viaduct Bridge in San Francisco were extremely challenging due to the requirement for very large and deep piles installed adjacent to historic structures. Drilled shafts up to 12? foot in diameter were constructed to a maximum depth of 200? feet in alluvial soils and Franciscan Bedrock using an oscillator system for the installation of the permanent steel casing. This paper provides an overview of the construction techniques, the equipment, and the challenges associated with constructing 12? foot diameter shafts on this very complex project in one of the nation?s nicest landscape setting.

Jan 1, 2011

By Y. Wang, E. Forssberg, A. Johansson, B. Chan

A super-conducting high gradient magnetic separator with matrix vibration in dry separation mode is a powder purification device, which has been used to remove weakly magnetic impure particles from fine calcite powders below 53 µm in this study. A fundamental question concerned is the evolution of the matrix clogging under gas-solids loads. This paper presents the improvement of the separation selectivity using a method of mechanically based vibration on the matrix in the separator. The functions of the matrix vibration are discussed. The results indicated that the mechanically based vibration on the matrix within a high intensity magnetic field while a feed was introduced in an air stream, was found to be effective for the dry purification of fine powder materials.

Jan 1, 2001

By Francis Gray

Mr. F. W. Gray: It is not my intention to read my paper as it is too long, so I will touch only on the high lights. The Sydney field is the most favourable example of undersea coal mining that exists, and I have not been able to find anything like it elsewhere. The nearest approach to it is a field in England where the Whitehaven collieries are operating, but it has a lot of faults. The net result of these faults so far met with in the seaward advance of the workings has been to increase, by something over 100 feet, the gain in depth of cover, in a distance of approximately three and three-quarter miles. In the Sydney field there are no faults of any consequence. On the east side, the English measures rise. In Australia the sea bottom fell and the cover became too light. On Vancouver Island the coal ran out, and in Japan the seams are steep and contorted. The Chilian fields resemble our own to some extent. An inundation of two collieries took place there some time ago, due, it is said, to the rise workings being allowed to approach the sea bottom too closely in the vicinity of a fault. The Cape Breton undersea field has been proved over a frontage of about thirty miles and has been attacked and penetrated for a considerable distance along that front. We have passed the prospecting stage and now generally use developed land areas as points of attack to win the undersea coal. Of our mining under the sea, it can be said that, with the exception of No. 1-B and Princess colliery, Sydney Mines, no real attempt has been made to win the undersea coal.

Jan 1, 1927