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By F. J. Budin

Steel supports are increasingly used in metal mines for junctions, chambers, and other wide openings and for semi-permanent areas such as haulageways, shaft stations, and pump rooms. Steel lasts longer-especially in wet mines and where foul air is present-and is procurable in different sizes that will carry heavier loads than any timber of equivalent cross section. The chief advantage of steel supports is that less excavation is needed than with timber support of the same strength, so that faster progress can be made. Since there is no possible way to calculate the exact weight on supports, sizes must be chosen by experience. Any adjustment and cutting of steel supports underground would be costly and time-consuming, and it is therefore advisable to cut sets beforehand at the surface workshops. This requires standardization of sets. All these problems have been recognized at Bawdwin Mines, Burma, where mining is difficult, slow, and very expensive. The lead-silver ore is very brittle, with hanging and footwall rock of unconsolidated rhyolite tuff. During the rainy season from May to October water penetrates into the mine, and where soft rock is present disintegration into a loose mass around openings can be expected. For this reason heavy 10x10-in. timber caps break quickly in drifts and crosscuts, and timber rots in a very short time. An average increase of 50 pct in both maintenance work and costs could not be avoided.

Jan 3, 1960

New York, March 18, 1913. MR. CHARLES F. RA ND, President, New YORK, MARCH American Institute of Mining Engineers. Dear Sir: In connection with the official notice of Dr. Raymond's unanimous election by the Directors as Secretary Emeritus, we wish to place upon record certain statements concerning his services to the Institute which we think have not been published., and may not be generally known to the majority of our fellow-members. When the Institute was formed in 1871, Dr. Raymond acted as Secretary of the Founders' Meeting, and became the first Vice-President of the Institute, and, by request of the aged and beloved David Thomas, who was the first President of the Institute, Dr. Raymond discharged all the duties of the office of President, to which he was later formally elected in 1872, and which lip held for three years. During that time, he visited Europe, and through his acquaintance and reputation abroad, established those international relations of the Institute which proved so important in later years. He also enlisted the support of the mining engineers and metallurgists of the Pacific Slope, who would not otherwise have been disposed to join a society originating in the East. And for twelve years he attended; at his own expense, nearly every meeting of the Institute, wherever held, giving to it without remuneration his best service, and sacrificing for it many professional and private interests.

Jan 4, 1913

Man is born on Mother Earth without knowledge or skills. Soon he finds physical needs for food, clothing, shelter, exercise, and relaxation. His personal needs are self-expression, new experiences, and amusements, while his social needs have been classified as work, status, security, friendship, companionship, and love. He finds himself infinitesimal in comparison to the whole. Often- times when he feels smug, he is actually riding for a fall. And nothing is much worse than frustrated man. The postwar world does not provide the Utopia of peace and prosperity of which man had dreamed. In fact, it seems that the sacrifices and waste of that great struggle are being lost in the morass of stupidity, selfishness, and cupidity which unfortunately are still the most conspicuous traits of the human race. Perhaps it is too soon to expect the blessiilgs which are supposed to appear in a peaceful world, and man's thought is clouded with a pessimism engendered by the conflict itself, in which all activities tend to enhance his pessimistic nature. Must man submit that it is a law of nature for nations to go to war? The war has demonstrated that when faced with a common danger, peoples differing in antecedents, language, forms of government, and resources can unite for a time, pool their skills and abilities, and emerge victorious from a contest unparalleled in magnitude, ruthlessness, carnage, waste, and cost. This has been accomplished by great individual and national sacrifices, the

Jan 1, 1950

By Porter W. Shimer

It docs not seem to be generally known that some American pig-irons contain notable amounts of vanadium, and while the present investigation is far from covering the whole range of irons, it is hoped that, at least, it may serve to call attention to the importance of looking for this element. The majority of the pig-irons investigated were made in the Lehigh Valley and neighboring furnaces, using more or less New Jersey magnetite in their mixtures. Many of these ores, and probably all of them, contain a little vanadium as well as titanium; the ore from one of the largest of these mines contains 0.05 per cent, of vanadium and 0.60 per cent. of titanium. Dr. Thomas M. Drown was the first to detect the presence of vanadium in the incrustations1 occurring on certain pig-irons, and he also found this element in a number of magnetites, but the methods for its accurate determination had not, at that time, been well worked out. In a general way, it may be said that the Lehigh Valley pig-irons contain from 0.02 to 0.05 per cent. of vanadium and from 0.10 to 0.20 per cent. of titanium. These elements follow the silicon; that is, the furnace-conditions which produce a high-silicon, low-sulphur iron will cause the maximum reduction of vanadium and titanium, and

Jan 1, 1913

By W. P. Lass

Discussion of the paper of W. P. LASS, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 103, July, 1915, pp. 1443 to 1447. ROBERT M. KEENEY, Somersville, Conn. (communication to the Secretary *).-There is not only a possibility of improvement in present methods of treatment of the byproducts of refining in the cyanide plant by the use of the electric furnace, but also in melting and refining of gold precipitate. This interesting paper by Mr. Lass shows an electric furnace in successful operation in a large plant for the treatment of by-products. Electric melting of cyanide precipitate is a cheaper form of treatment in many cases than any of the combustion methods now used because of the high cost of oil, coke or coal in many camps, while on the other hand electric power may be had cheaply, especially in a place where there is possibility of development of high-head hydro-electric plants for power purposes. Also, if the oil-fired tilting furnace is used for direct melting of the precipitate, as is the case at many small mills, a great saving in cost is made by the use of the electric furnace because of the high crucible cost in melting with the tilting furnace. A study of this paper indicates the cost of the operation approximately. Consider all the fluxes to be turned in as byproducts and coke at $18 per ton.

Jan 12, 1915

ENGINEERS AVAILABLE. (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons.) Member, graduate of College of Mines of University of California, with 12 years' operating experience in mining and milling in California, Canada, and Mexico, is open for engagement. Speaks Spanish fluently. No. 17. Mining engineer and metallurgist open for engagement Jan. 1 as superintendent of mines or constructing engineer. Technically educated, with 14 years' experience in United States and Latin America in concentration, amalgamation, cyaniding, constructing. At present building large modern .all-sliming cyanide mill in Central America. No. 18. Member, mining and metallurgical engineer, is open to engagement. Specialty, the treatment of copper ores. Nine years' experience in the operation and also in the design and erection of copper smelteries. Four years true pyrite smelting. Able to organize the administration, accounting, etc., of a large plant. Speaks a fair amount of Spanish, Russian, German, and French. Qualified to take charge of a large smeltery, or to act as assistant to manager of a combined mining and smelting concern. No. 19. Member, technical graduate, 33 years old, 11 years' experience as chemist, metallurgist, and superintendent of lixiviation plant and in charge of construction of cyanide mill, is open for engagement. Speaks Spanish. No. 21. Member, lately with the Bishop Creek Milling Co., California, is now open for engagement as mine superintendent or superintendent of construction of mine and mill structures. No. 25.

Jan 12, 1913

By E. P. Abrahamson

The effect of transition element binary solid solution additions upon the recrystallization temperature of titanium has been investigated. All additions, except columbium and tungsten, raised the recrystallization temperature. A correlation is obtained between the logarithm of the absolute rate of change of recrystallization temperature with atomic percent solute and the number of uuter d shell electrons attributed to the free atom of the solute element in its ground state. The work of Abrahamson, et aL.1-6 on dilute binary solid solution alloys indicated a correlation between the free atom ground state electron configuration of the solute and both the brittle-ductile transition and recrystallization temperature. It is shown in these studies that the number of outer s and d electrons in the solute are of prime importance in determining the absolute rate of change of recrystallization or transition temperature with composition. Furthermore, the limit of initial linearity (in the curve of recrystallization temperature vs at. pct solute) has been shown to be a function of the number of d shell electrons in the solute for dilute iron- and vanadium-base alloys. To date no complete systematic recrystallization study of dilute binary titanium base alloys has been made. This study together with that of zirconium base alloys 6 will provide the data for the comparison of the effect of the same solutes upon two solvents with the same number of outer d shell electrons.

Jan 1, 1962

PURPOSE OF STUDY The case study was initiated because of the very real need to provide the best mineral inventory block estimates possible for the relatively new Sacaton mine. Sufficient mining had been done and records kept whereby it was possible to test the various estimation methods against detailed blasthole samples taken during mining. Three estimation methods were selected for testing: (1) the polygonal method, (2) the inverse distance squared method (IDS), and (3) the geostatistical kriging method. The results of the comparative analysis was thought to have very practical application to the selection of extension functions for future estimation of grade for mineral inventory blocks. GENERAL GEOLOGIC DESCRIPTION The porphyry copper deposit of the Sacaton open pit mine is related to small quartz monzonite intrusives of Laramide age which have been intruded into Precambrian granites. Both rock types act as host for the mineralization, which has been secondarily enriched sufficiently to constitute ore. The chalcocite enriched zone has been subjected to postenrichment oxidation processes with consequent partial destruction of the chalcocite blanket. Several mineralogical populations are represented in the total ore zone, but the blocks on the mine benches involved in the study were restricted to the top of the enriched zone. COMPUTATION OF MINERAL INVENTORY BLOCK ESTIMATES In order to make valid comparisons among the three estimation techniques, all of the inventories were prepared from diamond drill assay data used in the original engineering feasibility study. The data was taken from ex-

Jan 1, 1980

By V. R. Garflas, J. W. Ristori, R. V. Whetshel

Preliminary estimates indicate that world consumption of petroleum products and related fuels in 1937 shattered previous records with a figure of 1,920,000,000 bbl.; that is, 124,000,000 bbl. more than the 1936 total. The writers, as in previous years, have been unable to account for all the available supply in 1937. This "unaccounted-for" supply, which formerly was thought to go largely into storage in foreign countries, was close to 53,000,000 bbl. in 1933; 93,000,000 in 1934; 111,000,000 in 1935; 75,000,000 in 1936 and 148,000,000 in 1937. As this discrepancy between supply and demand continued year after year, it became evident that other reasons than additional foreign stocks were responsible for it. It can now be stated that the "unaccounted-for" supply (see Table 1) goes to take care of: (1) consumption of petroleum products and related fuels for military purposes, the figures of which have been and are kept confidential by foreign countries, (2) additions to stocks to be consumed for military and nonmilitary purposes in foreign countries on which likewise no information is available, (3) errors incurred in the conversion of figures of production of crude oil, its products and related fuels from "weight" units, as used in Russia, for instance, to their American or "volume" equivalents and vice versa, and (4) to the lack of reliable statistics on production and consumption, particularly from Russia, the

Jan 1, 1938

By F. B. Foley

IT is with an unusual degree of personal satisfaction that I find myself in a position to pay tribute to the memory of Henry Marion Howe. One could not have spent any length of time in the presence of Dr. Howe without profiting intellectually. I do not hesitate to say that my years of association with him were the most stimulating of all my years of metallurgical study. He always impressed one with his own eager search for knowledge. Never dependent on the written word alone he sought information from anyone whose opinion he valued. His ability to piece together bits of apparently conflicting data from various sources so as to build up a logical hypothesis was unique. A small slight man with the intellect of genius he would have gone to the top in any endeavor he undertook and it was fortunate for metallurgy that its study attracted him as it did. Howe was a modest man. I like to recall an incident which left a lasting impression with me. The lab- oratory in his home, "Green Peace," was in the basement and access was by way of stairs leading down from his secretary's room. In using these stairs my attention was attracted many times to an ordinary cardboard shoe box which reposed on the shelf above the landing. It was crudely labeled on its side in black ink "Vanity Box." My curiosity was aroused to the point that I finally asked his secretary what it was. With some amusement she took the box from its shelf on the stairway, opened it and showed me its contents—numerous letters, from the foremost men of science of every civilized country throughout the world, commending his "Metallography of Steel and Cast Iron." I recall that in reply to one who thought there was not enough of Howe's own researches in his book he wrote, "Primarily I am a writer, secondarily an investigator." Howe wrote to make his readers think. No one ever strove harder than he to be right but above all, whether his viewpoint proved ultimately to be right or wrong, he was always content if by his stand, he provoked a reader to take the next step along the path to greater knowledge. I doubt that he was ever afraid to be wrong for he was always secure in the thought that his effort was guided by a sincere search for the truth. One continually searching for truth is entitled to occasional excursions up the wrong alley. A glance backward to the metallurgical confusion of some thirty to forty years ago, or need one go back so far, provides convincing proof of what a host of companions one may have in a common acceptance of ideas which the future will prove to be wholly untenable. Well over a hundred years have passed since investigators have interested themselves in the effect of increasing the temperature of iron and steel on their mechanical properties. We are told by Charles Walrandl in "Industrial Annals" for June 11, 1822, that bend tests, conducted in a Russian steel works of Prince Demidoff, on steel bars "highly heated" and bent during cooling became brittle when bent at an iris blue color. He concluded, "That when steel is heated to a temperature between 473°F and 662°F the mettle was more brittle between these limits than at a much lower or at a much higher temperature." It was a curious bit of information recognized as true to this day and still not explained satisfactorily. In 1878 Charles Houston in Annales de Mines associated this brittleness with an increase in tensile strength at 572°F. When this relatively low temperature is exceeded it is recognized that steel becomes weaker as temperature is increased up to the melting point, where no strength of practical importance remains. It is easy to believe, in fact it goes without saying, that this weakening as the temperature of a metal is increased is the result of the motion of the atoms making up the metal, a motion which itself is evidence of the temperature increase. However, if we are considering iron or steel we find that this decrease in strength is not a steady one, for, besides the increase in strength just referred to, one comes to a temperature, the critical temperature, where results of tests indicate the metal to be extremely weak and then as temperature increases to become sensibly stronger again. This apparent anomaly was made the subject of the first Howe Memorial Lecture, delivered by Albert Sauveur in 1924. It may be of interest to review these findings of Sauveur. He used two methods of investigation. One involved the twisting of bars. The bars were heated in an

Jan 1, 1951

By W. N. Poundstone

The mining and ventilating system used in development work in the Pittsburgh Seam in northern West Virginia is discussed. The seam conditions and the nature of the accompanying methane gas are described. The type of equipment and the mining cycle will be discussed, showing how they are well suited for very gaseous development work. Face ventilation in development work is possibly the fastest growing problem of the industry. The coal mines of the future will be faced with the prospect of mining from under increasing depths of cover. Consequently, larger and larger amounts of methane gas probably will be found. The Pittsburgh Seam, in northern West Virginia, is an example of an area already faced with this problem. At the present time, most of the development work being done in this seam lies beneath 500 to 1200 ft of cover. The Pittsburgh Seam in this area has always been very gassy—even near the outcrop—and the recent development work has been accompanied with extremely large volumes of gas. In many cases, a single development section has liberated in excess of 1,000,000 cfm in 24 hr. This problem of heavy gas liberation was the chief concern, several years ago, when continuous mining equipment was first considered at Christopher Coal Co. All of us were apprehensive about the liberation that would accompany rapid extraction in a single working place. However, the experience during the past few years has shown that this ability to mine only one place at a time, is actually the key to working this type of coal. With all of the mining or advancement concentrated in one place, the ventilation can also be concentrated. By this it is meant that continuous mining permits the active working place to be ventilated with a maximum amount of fresh air, taken directly from the intake source without first passing another working place. Continuous mining (and a good ventilating system) also permits a much greater concentration of attention or vigilance to the actual working place. There are two things that are very important to the mining of coal having high rates of liberation. First, adequate volumes of air are necessary. Second, and perhaps more important, a mining and ventilating system must be used that will provide an uninterrupted flow of air to every portion of the working section. Liberations of this magnitude take only a few seconds of interruption for a dangerous accumulation of gas to occur. With adequate volumes of air available, the ability to concentrate ventilation more than offsets the concentration of gas emission that is inherent with continuous mining. The mining system used with continuous mining equipment at Humphrey Mine is similar to the system used at many mines in the area for development work. This system is designed to favor ventilation, realizing that other efficiencies are meaningless if the equipment must stop because of ventilation difficulties. This plan is especially well suited to minimizing ventilation interruptions. Basically, the overall plan of mining is to develop headings into virgin coal and encircle or block out large areas. These blocks are generally at least 2000 ft sq. The purpose of this blocking out is to bleed gas from the area before pillaring. Experience has shown this method to be quite effective, even in the most gassy areas. The gas in this field seems to migrate or flow readily from the solid coal into the outside return headings of the development work. The numerous clay veins and slips that are found in the area are extremely good avenues for gas flow. A block of coal, surrounded with development headings, usually bleeds off readily; and since it is cut off from the virgin coal, it is not subject to gas migration, through the seam, from this source. However, the outside return of the encircling development work, adjacent to the virgin coal, may liberate gas for years. This liberation from the outside ribs in the virgin coal is the reason split ventilation is used in development work. If split ventilation were not used, there would, in many cases, be a serious build-up of gas in the intake before it could reach the working face. Fig. 1 shows a typical development section having seven headings. The two outside places on each side are returns, and the three center headings serve as intakes. This section is equipped with a ripper-type continuous mining machine. An off-track loading machine is used to load from a surge pile on the

Jan 1, 1961

By B. J. Dotson, P. N. McCreery, R. L. Slobod, James W. Spurlock

A core sample porosity-check program is described. A number of laboratories participated in the investigation. which comprised measuring the porosities of ten selected natural and synthetic core samples. Each laboratory employed its own method (or methods) of measurement. These included Boyle's Law, water-saturation. and organic liquid-saturation methods. Brief descriptions of each method employed are given. In general, the measured values of porosity were in reasonably good agreement. The average deviation of porosity from the mean or average values for the group of samples was ±0.5 porosity per cent. The results of these measurements are compiled and presented in graphical form. INTRODUCTION The total hulk volume of a porous sample is derived from the sum of two volumes, the void or pore volume and the solid* or grain volume. The porosity fraction of the sample ia defined as the ratio of the void volume to the bulk volume. Multiplication of this ratio by 100 converts it to per cent porosity. Distinction is made here between total porosity and effective porosity. The former includes all void space, both interconnected and isolated, while the latter includes only those voids which are interconnected. This investigation deals only with the effective porosity.* Numerous cases had been noticed in which there appeared to be appreciable discrepancies in the results of porosity determinations on core samples. Differences of as much as 10 to 15 porosity per cent had been reported from different sources

Jan 1, 1951

By H. R. Thresh, A. F. Crawley, D. W. G. White

The densities of liquid tin, lead, and Sn-Pb alloys have been measured over a range of temperature above the liquidus. In all cases, data can be adequately represented by an equation of the type p = a + bT. For pure tin, the values of a and b are, respectively, 7.139 and 7.125 x 10-4, and for pure lead, 11.060 and 12.220 x 10-4. At constant temperature, molar volumes in the Sn-Pb system vary linearly with composition. DURING the course of a long-term program at the Department of Energy, Mines and Resources, Ottawa, Canada, the densities of liquid tin, lead, and Pb-Sn alloys were studied. The work reported herein draws on two sets of results independently achieved by Thresh, on the one hand, and by Crawley and White, on the other. EXPERIMENT The method and apparatus were originated by Thresh and have been described in detail in Mines Branch reports.172 In operation, the 14 cu cm graphite pycnometer is put in the furnace as shown in Fig. 1 after a machined charge has been placed inside the pycnometer and the lid screwed down. The dimensions of the charge are such that, upon melting, a small excess of liquid metal is discharged through the capillary hole to displace the weighted float above. When the pycnometer has been equilibrated at the experimental temperature, the

Jan 1, 1969

By Robert Lindsay

A NUMBER of detailed investigations of the physical changes accom-panying age-hardening have raised the question as to the possibility of some phenomenon preceding the actual process of precipitation. There is considerable evidence to indicate that in the first stages of the aging process there is a pronounced distortion of the crystal lattice. This is particularly marked in duralumin. It would be of considerable theo-retical interest to know the nature of this distortion as compared with that produced in other ways and to find out whether, in supersaturated alloys, it is a necessary antecedent to the formation of a second phase by precipitation. It was believed that a study of the age-hardening char-acteristics of a normally aged alloy compared with one that had been mechanically distorted might supply some useful information on these points. In addition, information would be obtained regarding the effect of a mechanical distortion on any subsequent stage in the aging process. Duralumin was chosen as the material for this investigation because the various aspects of its aging behavior can be shown in detail by suit-able variations of the aging temperature. Also, probably more work has been done on this class of alloys than on any other. In spite of the many published results, it was felt that the experiments would be significant only if all of the work were done on samples from the same source and if they were examined under identical experimental conditions.

Jan 1, 1939

By Alan D. Randolph

INTRODUCTION The production of fines is an unwanted side-effect in most crystallization processes. The definition of “fines" is relative to the size of the desired product and varies from <30 mesh for coarse KC1 fertilizers to subsieve organic material produced by salting-out pro- cesses. Sometimes a well-developed fines distribution is necessary in the production of large crystals, e.g. the fines removal stream from a potash crystallizer. The production of fines is usually not desired in a crystallization separation step. However, product purity can either improve or degenerate with a decrease in crystal size depending on the relative importance of product washing vs mother liquor occlusions in determining over-all purity. Typically, both washing efficiency and mother liquor occlusions decrease with decreasing particle size. Fine crystal distributions have historically been difficult to measure and categorize; however this situation is changing rapidly with the use of electronic particle counters of the electrical zone- sensing or light scattering type. In fact, fine-crystal measurement is perhaps the key to better understanding and control of coarse- crystal crystallization processes. The fine-crystal distribution carries much useful information from which nucleation and growth rates can be inferred. The purpose of this paper is to briefly discuss a few crystallization processes in which production and/or measurement of fines is important and to categorize the process conditions which yield a fine- crystal product.

Jan 1, 1980

By P. N. McCreery, R. L. Slobod, B. J. Dotson, James W. Spurlock

A core sample porosity-check program is described. A number of laboratories participated in the investigation. which comprised measuring the porosities of ten selected natural and synthetic core samples. Each laboratory employed its own method (or methods) of measurement. These included Boyle&apos;s Law, water-saturation. and organic liquid-saturation methods. Brief descriptions of each method employed are given. In general, the measured values of porosity were in reasonably good agreement. The average deviation of porosity from the mean or average values for the group of samples was ±0.5 porosity per cent. The results of these measurements are compiled and presented in graphical form. INTRODUCTION The total hulk volume of a porous sample is derived from the sum of two volumes, the void or pore volume and the solid* or grain volume. The porosity fraction of the sample ia defined as the ratio of the void volume to the bulk volume. Multiplication of this ratio by 100 converts it to per cent porosity. Distinction is made here between total porosity and effective porosity. The former includes all void space, both interconnected and isolated, while the latter includes only those voids which are interconnected. This investigation deals only with the effective porosity.* Numerous cases had been noticed in which there appeared to be appreciable discrepancies in the results of porosity determinations on core samples. Differences of as much as 10 to 15 porosity per cent had been reported from different sources

Jan 1, 1951

By Raymond Sanford

IT IS difficult to know just when a hoisting rope should be removed from service and a new one substituted. It is desirable to utilize the full life of a rope but, on .the other hand, the damage and possible loss of life, resulting from delay in replacing it may amount to many times the cost of a new rope. In the present methods of inspection the inspector must rely upon accumulated experience and a certain sixth sense or intuition in addition to any rules that may be laid down regarding the number and distribu-tion of broken wires. This condition does not neces-sarily arise from lack of interest among users or makers of rope, but is due rather to the lack of satisfactory or adequate methods for testing ropes to determine their exact condition. The main difficulty in devising a physical test lies in the fact that a number of causes, all operating in different ways, contribute to the deterioration of a rope in service, and affect not only the external conditions but also the inner structure of the material of which the rope is constructed. Wear and broken wires on the outer part of the rope are not difficult to detect, but a test is needed which will clearly indicate the presence of broken wires in the interior portions and the change in strength due to alterations in the structure and properties of the material itself.

Jan 7, 1923

By John W. Pack

At present the manufacture of metallic zinc, or spelter, in Missouri, is carried on only at the establishments located at Carondelet, or South St. Louis. Although the development of the industry has not yet reached that fulness which it has attained elsewhere in the United States, still the commanding advantages of position of these establishments are so evident that the prospective importance and magnitude of spelter manufacture in this State, and especially at this locality, can hardly be doubted. A study of the chemical and technical aspects of the business of these points cannot be without interest to the metallurgist as well as to the capitalist. I have endeavored to investigate, as far as was practicable, within the limits of a paper of this character, some of the problems connected with this industry, at the same time making a few comparisons of the results attained at some of the Carondelet works with those of other establishments with regard to which information could be obtained. In the prosecution of these studies I have been kindly aided by the managers of Carondelet establishments, and by Prof. Charles P. Williams, Director of Rolla School of Mines. To the latter I am especially indebted for assistance in regard to methods of analysis. To all these gentlemen I return my thanks for their valuable aid. Other sources of information will be duly credited in their proper places.

By Gloyd Wiles

THE eastern section of the Park City dis-trict is drained to an elevation of 6300 ft. by means of the Ontario drain tunnel owned and maintained by Park Utah Consolidated Mines Co. This elevation represents a depth of 920 ft. in Park City Consolidated Mines Company&apos;s property. When development below the goo-ft. level was commenced, sinking was at-tempted through an incline winze in the fissure. The intensely fractured quartzite forming the walls of the vein could not be held after water was encountered, so it was decided that further sinking should be done in a vertical winze far enough in the foot-wall to be in the more solid quartzite out-side the fractured zone containing the vein. Progress was good until a depth of 200 ft. below water table was reached, where the flow of water became serious. Sinking pro-gressed 300 ft., to the 1200-ft. level, and there approximately 750 gal. of water per minute was being pumped. The last 20 ft, of sinking cost more than $200 per foot direct charges, whereas the over-all cost for the 300 ft. was $100 per foot. This high last cost was caused by excessive lost time in pumping. Crosscutting to the vein disclosed the fact that the 1050-ft. level had been devel-oped only after drainage had been effected from the 1200-ft. level, but that the 1200-ft. level could not be opened because of the

Jan 1, 1940

By W. A. Vine

WHEN a hole is made in a stressed solid, such as rock pierced by mine openings, equilibrium of the solid is destroyed. To re-establish that equilibrium the stress condition in the rock surrounding the opening becomes rearranged. This rearrangement may or may not develop local stresses in the vicinity of the opening which exceed the elastic strength of the rock. Since stability of the opening depends, therefore, on the strength of the naturally occurring rock surrounding the opening, this rock is an engineering material of construction, and all rock affected by the associated opening or system of open- ings may be considered a structure. The term invert is chosen to describe the formation of the structure —built from the inside, as it were, and a consequence of mining rather than an entity built for a purpose. By definition, an invert structure is formed when openings are made underground and is composed of that material on the solid side of a rock-air interface wherein the stress condition is affected by the associated opening or system of openings. The shape of an invert structure is never clearly defined; the skin of the structure may be mapped, and even described, but the boundary of the structure within the solid rock mass must be arbitrarily set. The name geomechanics is proposed to describe a branch of scientific knowledge which will encompass principles and working hypotheses for behavior and design of invert structures. It is foreseen that study

Jan 1, 1956