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By E. H. Mohr

At the McGill concentrator of the Nevada Consolidated Copper Co., all flotation operations have been carried out in Forrester cells since November, 1926. In respect to cost of operation, the new cell has proved to be superior to the Callow, which it supplanted, and its incorporation in the flow sheet has resulted in a marked improvement in the metallurgy. Before citing the advantages of the new machine over the old, it should be explained that the Forrester has not only replaced the Callow, but it has made possible the elimination of a number of tables as well. When Callow cells were in use, table concentration preceded flotation. The ball mill pulp was elevated, by means of air lifts, to roughing Wilfley tables situated two floors directly above the flotation floor. On an intermediate floor were additional tables which cleaned the concentrate from those above. The finished table concentrate constituted approximately 60 per cent. of the total mill production, and contained about 40 per cent, of the recovered copper. The table tailings were returned to the classifiers, the overflow from which went to the flotation cells and the oversize to the ball mills. As soon as the Forrester cells were installed, this tabling operation was discontinued. The ball mill pulp now discharges into the classifiers direct, without the intermediate tabling. It was impracticable to ernploy the present flow sheet when Callow cells were in use, for the reason that unless the great,er part of the heavy mineral was first removed, it accumulated on the mats and adversely affected the flotation operation. By tabling ahead of flotation, it was practicable to maintain the concentrator at 10 to 20 per cent. greater capacity (depending up on the pyrite contnt of the ore) than was possible by flotation alone. This was due to the necessity for finer grinding in the latter case. Even though the table conecntrates contained only 6 to 8 per cent'. copper content, the low smelting costs made it advantageous to operate at high mill capacity, at the cost of low grade of product. Standard Section equipment With the old flow sheet, a standard section consisted of four ball mills and classifiers, one air. lift, 20 roughing tables, 10 cleaner tables, 12 primary

Jan 1, 1928

By K. B. Nowels

"INTRODUCTION For the last several years the oil industry has been turning more and more toward conservation arid the study of related production problems. It is generally conceded that ultimate recovery is increased by holding the natural gas in thy sand which is net needed in lifting the oil. The retained gas lowers the viscosity and surface tension of the oil and helps flow the oil from the sand. Lewis states that ""while the operator can not control the original conditions of energy and resistance in the sand, he can partly control the efficiency of expulsion. As it is the energy contained in the compressed and absorbed gas rather than the oil that is exhausted, it is but logical to judge the efficiency of a producing method largely by the relative quantities of gas produced with each barrel of oil. If by a change in method the producer lessons the proportion of gas with each barrel of oil, he should increase the total recovery- of oil correspondingly, even if the rate of production is temporarily reduced somewhat.""The effect of ""pinching in"" or controlling the flow of oil wells in an effort to lessen the proportion of has never been definitely known. The general belief has been that ""pinching"" a flowing well causes the oil and gas volumes to be reduced proportionately, maintaining the same gas-oil ratio as before the reduction in flow was made. Studies of gas-oil ratios in many fields have shown that much gas has been wasted, insofar as its effectiveness in oil production is concerned. Swigart and Bopp carried."

Oct 1, 1927

By C. H. Herty, J. K. Gaines

"Nearly every piece of electrical equipment used in mines ""breathes."" In other words, motors, controllers, rheostats, switches, and other similar equipment, even though encased in seemingly tight compartments, breathe in the atmosphere that surrounds them.As the apparatus is used, the temperature of metallic parts is changed generally in positive direction through the heat by friction and the heat due to the electric current. When the apparatus is idle it gradually cools down to the temperature of the surrounding atmosphere.This increase of temperature during operation and return to normal temperature when operation stops alternately raises and lowers the temperature of the atmosphere within the compartments which, in strict accordance with Charles' law -T = VT1 V'will expand or contract in proportion to any given temperature change.As compartments are not gas-tight, such expansion and contraction will force the atmosphere out of the compartment =on expansion and suck the surround¬ing atmosphere into the compartment during contraction, hence the term ""breathing.""Investigators of explosion-proof equipment have recognized that such an interchange would take place and have designed their equipment to safeguard possible explosions within the compartments."

Jul 1, 1927

By Thomas Varley

"The literature on flotation of oxidized ores except for patents (especially for reagents) is very sparse. The Bureau of Mines in 1936, published a circular on the subject, by Ralston and Allen. The treatment of oxides by flotation was then in its infancy, but several of the most important mining companies in the Western United States and Mexico are now operating flotation plants for treating oxidized ores. The purpose of this present circular is to review the progress made and bring the subject up to date. One of the writers of the 1916 report (Mr. Allen) has been associated with some of the most important mining companies who have put into practical operation the process of flotation of oxidized ores; among these companies are the Shhttuck Arizona Copper Co., Bisbee, Arizona (now the Shattuck Denn Co.) and the San Francisco Mines of Mexico, Ltd., San Francisco Del Oro, Chihuahua, Mexico. His experience and other sources of information have been freely drawn on in pre-paring this paper. Mr. Ralston, assistant chief metallurgist of the Bureau of Mines, contributed many valuable suggestions and criticisms.Sulphidizing Reagents for Oxidize Ores.The various reagents and methods that might possibly be used for sulphidizing were summarized by Ralston and Allen as follows:""Sulphidizing (1) by the use of hydrogen sulphide on either the dry or the wet crushed ore, (2) by the use of solutions of the various sulphides and sulpho-compounds of sodium, (3) by the use of solutions of the various sulphides and sulpho-compounds of calcium, (4) by the use of sulphur vapor, (5) by the use of a sulphureted oil, (6) with colloidal sulphur."

Jun 1, 1927

By George Collins

AT the meeting of the Western Division of the American Mining Congress, held in Denver last September, papers were read by F. H. Brownell, a vice-president of the American Smelting and Refining Co. and chairman of its finance committee, and by H. Foster Bain, former director of the United States Bureau of Mines and now secretary of the A. I. M. E.. which dealt thoroughly with certain phases of my sub-ject. These addresses can hardly have failed to awaken serious reflection in all who listened to them; but their implications have apparently not penetrated the con-sciousness of bankers, economists and statesmen, whose business it is, or should be, to prepare for the economic and social changes which must inevitably follow, if the conclusions which I shall outline hereinafter are true. In discussing this subject I wish to disclaim any intention or desire to forecast the course of the metal markets or the immediate prospects of the mining in-dustry. The facts' adduced must inevitably influence the value of metals, the activity and profitableness of mining, and perhaps also the social status of those en-gaged in it. But my forecasts do not refer to this year, next, year, or the year after. The nearest ap-proach to a date on which I will venture is that the relative scarcity of gold may begin to make itself felt in something like ten years from now, but its effect will not culminate for several years thereafter. Scarcity of new gold is likely to be offset, to some extent, by increasing use of currencies based on credit; but unless it is found possible to dispense with the gold standard altogether, this can hardly prevent a great ultimate fall in commodity prices. This fall, moreover, is likely to be more severe in manufactured goods than in what are, popularly termed raw ma-terials; and most of all in those manufactured goods which are susceptible to the greatest degree to cheapen-ing by mass production, and which are least counter-affected by increasing metal prices; by which I mean those in which the cost of metal contained forms a relatively small, element in the total cost of production.

Jan 6, 1927

By Walter Barnum

AS a member of the Institute and as the president of the National Coal Association, I come before you today in a dual role. As an Institute mem-ber I welcome the opportunity to make complimentary reference to the growing support which bituminous coal operators are giving to programs looking to the advancement of the engineering profession, and to suggest plans whereby these programs may be enlarged to mutual advantage. As a representative of the bitu-minous industry, it gives me special pleasure to express the appreciation of the industry for the services ren-dered to it by members of your profession. Needless to say, there is a close relationship between the engineer and the coal operator. With increasing frequency and in the interests of the industry, the engineer is becoming more of a factor in the business of producing coal. I need look no further for an out-standing example of this encouraging trend than to Samuel A. Taylor, who not only is a bituminous coal producer but also has risen to such eminence in the engineering profession as to have been chosen the head of this great body of technical men, the American Institute of Mining and Metallurgical Engineers. There are many coal operators whom I might mention as having achieved distinction in the engineering world, such as Howard. N. Eavenson, chairman of the .Coal and Coke Committee. And I would be guilty of a serious .oversight if I failed to make reference to Eckley B. Coxe, one of the founders of the Institute in 1871, a prominent anthracite operator and credited with several important inventions. While it is true that a. considerable number of execu-tives of coal-producing companies in this country came up through the engineering ranks. the proportion of mine executives in England, France, and Germany who are graduate engineers is much larger than it is in the United States. In France all members of the staff are engineers and such is the case in Germany up to the owner of the mine. In Germany the owner is not so frequently an engineer as is the rule in France.

Jan 3, 1927

By W. H. De Blois

Introduction In the contact process for ?the manufacture of sulphuric acid, sulphur dioxide gas - produced by the burning of sulphur or of sulphur-bearing ores, or as a by-product in the treatment of sulphide ores - is made to combine with the oxygen of the air to form sulphur trioxide, which then only requires the addition of water to form sulphuric acid. The substance, as for example platinum, causing this combination is usually referred to as a catalyst, a convenient term, in the definition and explanation of which many pages have been written. Catalysis is now a comparatively common means of effecting chemical combination, but if the question were raised here tonight as to what actually goes on when this apparently innocent third party unites the parties of the first and second . part, without itself being altered in any way, I am afraid even our most learned members would have to confess their inability to entirely explain the phenomenon; for although the subject is under investigation, there is still much to learn. The contact process, however, is one of the outstanding achievements in chemical engineering. ? From the standpoint of the difficulties involved and the time absorbed in their solution, it probably stands alone in the field of technical chemistry. In fact, the manufacture of sulphuric acid has, from the earliest days, been surrounded with problems which have interested the ablest chemists. The Chamber System Although this paper has particularly to deal with the contact process, it may not be amiss to refer briefly to the chamber system, which was, and still is, a most important factor in the sulphuric acid industry.

Jan 1, 1927

By Davenport, Edmund S.

THE specific aim of this work has been to study certain forms of internal deterioration which occur in tungsten filaments when subjected to high temperatures under various conditions, and to determine the cause of such deterioration. This would naturally lead to a consideration of methods of control or means of prevention of the phenomena. The deterioration was first noticed as a peculiar condition in the grain boundaries of certain tungsten filaments which had been burned t for long periods in lamps. In these cases it was noted that the grain bound aries contained a number of minute black dots which were at first thought to be non-metallic inclusions. It was demonstrated later that these dots or pits, as they were designated, could be readily produced by burning filaments in an atmosphere of flowing hydrogen. This method was convenient and adequate for the purpose, and was adopted for most of the work discussed in this paper. The evidence accumulated to date indicates that these pits arc actually small voids between the grains. The purpose of this paper is to, present the information on this interesting subject gathered during a period of about 3 years. As applied to tungsten, the subject appears to be of considerable importance, experience having shown that this pitting is frequently associated with poor performance of filaments in lamps.

Jan 1, 1927

By R. S. Dean

THE numerous theories of hardening which have been advanced in recent years are all satisfactory in accounting for some of the phenomena observed in hardening metals, but none so far presented account for all of the facts observed. Some years ago one of the authors, R. S. Dean,1 presented a theory to account for some of the properties accompanying work hardening. The present paper develops this theory further in the light of recent experimental, work and extends it to other forms of hardening. Many of the ideas included have come from the writings and personally communicated thoughts of others. We have attempted to give proper credit in every case, but it is possible that we have not always done so. As an historical basis it is desirable here to review very briefly the hardening theories which have been current. The first comprehensive theory of work-hardening phenomena was due to Sir George Beilby.2 He contributed the idea that with cold work part of the structure of the metal was rendered amorphous and that it was to this amorphous material that the cold-worked metal owed its difference in properties. According to Beilby's theory this amorphous material was a super-cooled liquid and, therefore, had the characteristics of a vitreous material. That such a theory is not capable of explaining the property changes in metals has been repeatedly pointed out. This theory also allowed a slip to take place only once on a given plane, which, as has been pointed out by Jeffries and Archer,3 is not consistent with the observed length of an individual slip and the amount of elongation which can be obtained by wire drawing. The modifications, which have been proposed to this hypothesis to make it coincide with the experimental facts, have to a considerable extent robbed the theory of its clean-cut characteristics. The commonest of these modifications replaces the amorphous phase with an

Jan 1, 1927

By E. S. Moore

To properly understand industrial conditions in Spain it is necessary to consider the early history of the country. Spain is very backward in many lines. They use the sickle for cutting grain, and plows for cultivating the land, which resemble those of Biblical days. In the great mining camp at Bilbao only one steam-shovel is in use, although about two hundred million tons of ore has been produced, and this almost entirely from open cuts. It is the lack of industrial development, such as is found in many other countries, which permits large mining enterprises to be controlled almost entirely by foreign capital, although Spain is such an old country, and which permits mines opened in the days of the Phoenicians to still operate. Such deposits in America would be exhausted in a comparatively few years. The Phoenicians are supposed to have reached Spain about 1100 B.C. and to have worked some of the properties in the Rio Tinto district. The Carthagenians invaded the country about 236 B.C., and they were driven out about 205 B.C. by the Romans. The Romans ruled until 483 A.D., when they were overthrown by the Visigoths. Then, about 711 A.D., the Moors from Africa became prominent and they were finally expelled by the Spaniards in 1492. Spanish power reached its zenith under Phillip II, during the latter half of the 16th century, and since the close of that century the country has lost its prominent place among the nations. There are some evidences of revival in the development of good roads, the construction of a satisfactory network of railways, and the building of magnificent thoroughfares through the capital city, Madrid.

Jan 1, 1927

By W. A. Toohey

Introduction From the earliest times it has been an inherent trait of man to build or create something for his own use or convenience. The need of some form of shelter other than that of the caves led him to bind together stones and other materials to form walls for his abode. Moistened clay which hardened upon drying was no doubt first employed. The Assyrians and Babylonians appear to have employed it or the bitumen found in their country. The early Egyptians and Greeks used some form of lime in their construction work. In addition to these shelters, other structures received attention, and, long before the Roman Empire was established, the Carthaginians made use of a natural cement as binding material. Portions of an aqueduct, seventy miles long, in Northern Africa, built in those early days, are still in use. The Etruscans were the first people in Italy to employ a mortar in their buildings. The Romans, learning the art from the Etruscans, improved the mortar by using a mixture of lime and volcanic ash, called 'puzzolan', and built not only roads but those famous structures, the ruins of many of which exist to this day. The Pantheon at Rome, built by Hadrian about 120 A.D., is perhaps the finest example of the early use of cement in building construction. With the decline of the Roman Empire, the art of making cement seems to have been lost, and for centuries the builders of Europe used only lime mortar. Pure limestones were selected for making the lime and great care was taken in the preparation of the mortar, the supply for one year being made the previous season and left to thoroughly slake or 'ripen' in pits covered with earth. The mortar thus produced gave excellent service above ground or where it was exposed to the hardening action of the air, but would not harden under water.

Jan 1, 1927

By G. M. Carrie

Introduction The subject of basic refractories is daily becoming of increased importance in metallurgical processes, and there is a constantly growing necessity for the development of better materials. This fact, together with the realization that Canada possesses one of the best sources of such refractories in the British Empire, if not in the world, made it appear? advisable that the subject be presented to the Empire Mining and Metallurgical Congress at the 1927 meeting. Having been in close touch with developments in the Canadian product during the past five years, G. M. Carrie was requested to prepare such a paper. The Canadian producers of magnesia refractories have succeeded in developing the product to a place where it has almost entirely displaced imported materials from the Canadian market. These developments were made possible by a close study of the methods of preparation of the material, and by an exceedingly careful control of the manufacturing process so as to obtain a thorough blending of the different constituents with the resultant uniformity of composition. This point is very important to the metallurgist, as un-uniform materials are a potent cause of difficulties in most manufacturing processes and the constant trend is towards their elimination. The temperature at which the Canadian material is burned ensures high specific gravity and thorough shrinkage. The grain size of the product is so controlled that the voids are only just sufficient to allow of proper bonding, thus making possible a dense, hard bottom affording high resistance to erosion and shock. Careful proportioning of the constituent elements absolutely prevents disintegration.

Jan 1, 1927

By J. J. Beeson

For the past fifty years or more, the structural features of the Cordil-leran mountain system of western United States have presented some most interesting problems. Any geologist or engineer living in this region, or even making occasional examinations of the mines, will lose much of interest and importance if he is not familiar with the literature. Some of the greatest works on geology have been the result of studies carried on in sections of this region. Among the more important of the earlier works are those of Dutton,l King,2 Gilbert3 and Powell;4 of the more recent Lindgren,5 Ransome,6 Spurr,7 Butler8 and others have contributed much. Many of the papers are largely of scientific interest but even these lay the foundation for the commercial application of the broader features of the geology. I have read many of these works with the keenest interest and pleasure; in fact, some have been read until some of the more important findings seem to be my own. In this paper, however, it is my aim to accept credit for little more than the labor of assembling some of the ideas of others. This is done with the hope that an interesting and valuable discussion will be the result. If some of the ideas presented should

Jan 1, 1927

By Dean, R. S.

THE numerous theories of hardening which have been advanced in recent years are all satisfactory in accounting for some of the phenomena observed in hardening metals, but none so far presented account for all of the facts observed. Some years ago one of the authors, R. S. Dean,' presented a theory to account for some of the properties accompanying work hardening. The present paper develops this theory further in the light of recent experimental work and extends it to other forms of hardening. Many of the ideas included have come from the writings and personally communicated thoughts of others. We have attempted to give proper credit in every case, but it is possible that we have not always done so. As an historical basis it is desirable here to review very briefly the hardening theories which have been current. The first comprehensive theory of work-hardening phenomena was due to Sir George Beilby.2 He contributed the idea that with cold work part of the structure of the metal was rendered amorphous and that-it was to this amorphous material that the cold-worked metal owed its difference in properties. According to Beilby's theory this amorphous material was a supercooled liquid and, therefore, had the characteristics of a vitreous material. That such a theory is not capable of explaining the property changes in metals has been repeatedly pointed out. This theory also allowed a slip to take place only once on a given plane, which, as has been pointed out by Jeffries and Archer13 is not consistent with the observed length of an, individual slip and the amount of elongation which can be obtained by wire drawing. The modifications, which have been proposed to this hypothesis to make it coincide with the experimental facts, have to a considerable extent robbed the theory of its clean-cut characteristics. The commonest of these modifications replaces the amorphous phase with an

Jan 1, 1927

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

By W. H., Bassett

IN January, 1926, the writer began a study of the commercial value of beryllium in its relation to copper. The purpose of the investigation was not to make a mere laboratory study of the characteristics of beryllium-copper alloys, but to determine under mill conditions the behavior of copper when alloyed with beryllium and when other metals were added to such alloys; in other words, it was considered important to know whether the alloy bars could be hot-rolled or cold-worked, and what limits in composition would have to be established for these two methods of working. Consequently, more stress has been placed on the practical application of the alloys in engineering and commercial use than on a discussion of the metallography of the specimens examined, although this part of the matter has not been entirely neglected. Credit should be first given to G. Oesterheld,1 who, in 1916, published the copper-beryllium equilibrium diagram. Fig. 1 has been copied from the original article with the simple substitution of English words. It will be noted from Fig. 1 that alpha solid solutions are formed, up to about 1.5 per cent. Be (10.5 atom.). The freezing-point curve, after falling from 4.2 per cent. Be (23.5 atom.), enters into a very complicated form over the entire beta region. There is a possible compound, Cu2Be, at about 6.5 per cent. Be (32.3 atom.). The pure gamma range extends from 11.2 to 12.2 per cent. Be. (46.5 to 49 atom.), after which the liquidus rises rapidly to 30 per cent. Be. (75 atom.). The delta solution extends from 25 per cent. to an unknown percentage of beryllium. There is a eutectoid point at 575" C., extending from 1.5 to 11.2 per cent. Be., the maximum time interval of which occurs at 6 per cent. Be. Below this line the beta solution is described as breaking up into alpha and gamma. Microscopically, the eutectiferous alloy thus formed closely resembles pearlite, and requires a high magnification for its resolution.

Jan 1, 1927

By E. D. Gardner

Open-cut mining of copper ores in the western United States is a relatively new industry. At first the mining methods were mainly adapted from those used at open-cut iron mines and at quarries, but now efficient practices that are more suitable for the copper deposits have been developed. The pioneer in this field is the Utah Copper Co., of Bingham, Utah, which deserves great credit for working out much of the early procedure. Stripping began at that mine in 1906, and the large Garfield concentrator was put in commission in 1908. Next in order of development were the Nevada Consolidated Copper Co., at Ely, Nev. ; the Chino mine of the Ray Consolidated Copper Co., at Santa Rita, N. Mex. ; the New Cornelia Copper Co., at Ajo, Ariz. ; the Sacramento Hill mine of the Copper Queen Branch, Phelps Dodge Corporation, at Bisbee, Ariz.; and the open cut of the United Verde Copper Co., at Jerome, Ariz. The Sacramento Hill mine began to produce in 1923, and the United Verde open-cut mine has produced ore mainly in connection with stripping. The writer visited the Utah Copper mine in September, 1923; the Nevada Consolidated in August, 1923; the Chino in July, 1924; and the New Cornelia, the Sacramento Hill, and the United Verde open cut at various times during 1922, 1923, 1924, and 1925, mostly in connection with other work.

Jan 1, 1927

By George S. Rice

Potash is riot only an important ingredient in the manufacture of many products of modern industry, such as chemicals, explosives, medicines, paints, soap, matches, glass, paper, aniline dyes, bleaching agents, and a host of others, but is indispensable in agriculture. Justus von Liebig is credited with being the first to discover, about 1858, that potash salts in the soil constitute an essential plant food which is not replaced by nature when exhausted through continued cultivation, that this exhaustion results in a decreasing yield of crops, and that the virgin productivity of the soil may be restored, and indeed even increased, by the addition of suitable potash fertilizers. The fact is now well established that wherever intensive cultivation is employed, whether for the raising of cereals, cotton, tobacco, fruit, or garden truck, the replenishment of the potash content of the soil is essential to the maintenance of production. Hence potash is of primary importance in modern life, not only for the economic welfare of industry but for the production of valuable raw materials and the very food supply of the nation itself. SOURCES OF POTASH The main sources of commercial potash are: (1) The solid deposits of soluble potash minerals, such as carnallite, sylvinite, and kainite; (2) sea water, brines, and salt-lake deposits containing appreciable amounts of potash salts associated with sodium salts; (3) vegetable substances, such as wood ashes, bee sugar residues, seaweed, and sunflower stalks; (4) animal material, such as wool washings; (5) products resulting from the decay of organic nitrogenous matter, such as Indian niter; (6) dust in flue gases from cement kilns or in the top gases of iron blast furnaces; and (7) insoluble potash minerals, including alunite, feldspar, leucite, muscovite, and glauconite, all of which contain a considerable quantity of potash.1

Jan 1, 1927

By Norman L. Wimmler

Active placer mining in Alaska began near Juneau in 1880, but the first gold rush did not start until 1896; then the discovery of the Klondike brought gold seekers from all parts of the world. A few of the newcomers were experienced miners, but the majority knew nothing whatever of placer mining. Even those who were placer miners of much experience found entirely new conditions, notably frozen ground, that presented many difficult problems. As a result, numerous methods of mining and of thawing frozen ground were tried. From these trials the practice described in this bulletin has been developed. All known placer fields in Alaska have been mined to some extent, and some have been virtually exhausted. In most districts, however, there remain large quantities of low-grade gravel and also some small isolated areas of comparatively rich gravels which could not be successfully mined because of adverse physical conditions. These districts are now the scene of most placer mining, including dredging, hydraulicking, drifting, mechanical methods of open-cut mining, and ground sluicing (or booming) followed by " shoveling-in."

Jan 1, 1927

By Francis W. Gray

Introduction Extensive undersea coal-mining has developed on both the east and west coasts of Canada, and at this time some four million tons, or 25 per cent of the total output of Canadian coal, representing a pit-mouth value of $14,000,000 per annum, is coming from coal seams lying under the sea. Of the coal now being mined in Nova Scotia, 55 per cent comes from under the sea, and this proportion is likely to increase. The Province of Nova Scotia is at this date receiving in royalties paid upon coal ?removed from undersea areas a sum exceeding $400,000 per annum. The subject is, therefore, one of special interest to the Mining Society of Nova Scotia and the Canadian Institute of Mining & Metallurgy, and while this paper will deal chiefly with undersea coal-mining in Nova Scotia, an attempt has been made to summarize the development of mining practice in the winning of undersea coal in other parts of the world, with the hope that such a recital may assist in the assessment of local problems. The connection between the mining of coal under the sea and an insular or maritime geography is obvious in regard to Great Britain, Japan, Vancouver Island, Australia, and Cape Breton Island, and also in regard to the curious conformation of Chile; the tendency towards growth of a mercantile marine and naval eminence is equally obvious where coal is mined at tidewater. But, there is the further and less favourable significance that the mining of coal under the sea is associated with poverty rather than with abundance of coal reserves.

Jan 1, 1927