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By W. R. Roser, F. E. Rizzo, Wu Hu

An insight into the mechanism of electrocrystallization of copper in simulated commercial acid electrolytes has been surmised from scanning electron microscope analysis of laboratory prepared specimens. The growth takes place in three overlapping stages. In he first, lasting approximately one hour at 200 amps/sq m, a propensity to epitaxial growth is observed. During the second stage a preferred orientation developed. The crystallography of the deposit showed a strong preferred orientation with the [111] direction normal to the surface. Triangular pyramids with (111) faces and (111) texture is a common result. In the third stage, occuring at longer deposition times, side growth, dendrite-like branching is common. The obsermtions have some elements in common with published results for highly purified electrolytes. Several significant differences were observed. The truncated pyramidal and block type growth discussed in he literature is suppressed under the conditions studied. The results are briefly discussed in terms of the screw dislocation, fault, and layer type growth mechanisms of crystal growth.

Jan 1, 1973

By Campbell Osborn

From the viewpoint of practical economic engineering the main value in studies of demand and supply lies in the information they give concerning the next movement of price. The title of this discussion is too comprehensive for detailed analysis and it will, therefore, be narrowed to the question of price measurement. The oil operator is interested primarily in net profits. Prices, costs and production determine them. Production is here used in its broadest sense. It includes refining and marketing. It is an operating problem. Prices and costs are economic considerations. Though costs are an important element of prices and profits, the subject is too large to be treated in a brief paper of this sort. In the long run, costs govern prices, but for the purpose of gaging prices in the immediate future the relationship of current demand and supply are more significant. Operating, expansion, retrenchment, sales and storage policies of oil companies are largely influenced by the feeling of executives concerning this relationship. The stockholders of companies whose executives are wrong may suffer. Investors who err in their judgment may likewise lose. On the other hand, oil companies and investors who appraise these factors correctly and move accordingly will profit. It is an important subject worthy of careful consideration. The author has been asked to discuss the subject for 1928. From the beginning of the year until the first of June, as illustrated by Fig. 1, over-supply prevailed in the face of restricted production, but from June to September, with record consumption, demand slightly exceeded supply and oil came out of storage in the United States as a whole. One of the main problems of the oil man is to decide whether this condition will continue and what the next movement of prices will be. Before he can do so he must have an understanding of the underlying conditions and of the facts that led to the present situation. With these facts in mind he is in a position to measure the effect of the present relationship of demand and supply on price and is afforded a perspective that may enable him to look ahead for a short period of time. The practical

Jan 1, 1929

By Robert E. Brand, Strathmore R. B. Cooke

For a study of the bonding that occurs in magnetite pellets during oxidation, cubes of magnetite, hematite, and quartz were prepared, each with one surface polished and nearly optically plane. These faces were fired together under pressure and at various temperatures to determine whether bonding would occur. Sections of surfaces that bonded were examined microscopically. An attempt was made to measure the strength effected by this treatment. EARLIER work1,2 has shown that the strength developed by fired magnetite pellets containing silica or silicates is due to three separate effects. Two of these are associated with the formation of slag in the interior of each pellet at temperatures above 1000°C, where the atmosphere is substantially though temporarily neutral. The third is independent of the silica content and is responsible for the development of a hard shell around the pellet during the initial stages of firing, a condition which permits the pellet to assume the increasing load of the overlying burden and prevents extrusion of the slagged and semi-liquid interior. Pellets made from hematite concentrates do not show these effects unless specific additives are incorporated, and it is these differences in behavior which in large part account for the difficulty in producing satisfactory pellets from such concentrates. Elsewhere it has been stated that "the most important factor responsible for the development of strength in fired magnetite pellets containing no additive is the oxidation of magnetite to hematite and the subsequent recrystallization and grain growth of this constituent."' The object of the investigation reported in the present paper was to study in detail the mechanism described above and to evaluate its contribution to the strength of the fired pellet compared with other possible mechanisms, excluding slag bonding. This was effected by placing together polished faces of two cubes prepared from specific minerals and then heating them under constant pressure at different temperatures both in air and in nitrogen. The materials used were magnetite, hematite, and quartz. The magnetite was coarsely crystalline material from western Montana, the hematite was Itabira ore from Brazil, and the quartz was of optical grade but of unknown origin. A high-grade Lebanon (Pennsylvania) magnetite concentrate was used to prepare briquets for the investigation of bonding strength. Analyses of the iron oxide materials are given in Table I. The specimens for furnace treatment were prepared with a carborundum cut-off wheel, which cut the minerals into cubes approximating % in. along each edge. Care was taken to make the sides as parallel as possible. The edges of the faces to be polished were beveled, and the cubes were mounted in brass rings with sealing wax, this being essential to prevent the specimens from rocking during polishing. To prevent excessive friction, the wax was recessed so that only the brass ring and the face of each specimen would be in contact with the polishing lap. Each specimen was then ground with No. 600 carborundum to produce a level surface before polishing. The Graton-Vanderwilt process was not used for polishing because of the long time required by this method, but several other methods were tried. Cloth laps using levigated alumina or chromium oxide did not produce the desired polish. Satisfactory results were obtained by means of a pitch lap: which was used for all the mineral cubes, with levigated alumina as the polishing medium. The lap was operated in a machine similar to those used in the preparation of single optical surfaces. It was run at low speeds and moderate pressures, and polishing was stopped occasionally to prevent overheating of the lap. A good polish with flat surfaces could be obtained in about 5 min. After polishing the sealing wax was removed either in hot water or in a solvent such as turpentine.

Jan 1, 1955

By C. F. Austin, J. K. Pringle

In view of the many large differences in structure and physical properties between metals, plastics, and most rock materials, a continuing experimental petrodynamics program has been established at the U. S. Naval Ordnance Test Station. Part of this program has been to test the concepts of scabbing and corner fracturing in a typical coarse-grained rock. The results of this experimental program have shown very interesting differences between the formation of fractures in rock and the formation of fractures in other materials such as metals and plastics which are often used as models for rock behavior studies. The gross behavior of coarse-grained brittle solids subjected to impulsive loading has undergone abundant empirical investigation by mining organizations and by mineral research agencies. However, the fundamental response of coarse-grained brittle solids to impulsive loading has received little detailed study in recent years. The various organizations and agencies interested in rock-like brittle materials have broadly applied the stress wave interaction concepts of the impulsive failure of metallic samples to the behavior of granular brittle materials 1,2,3,4,5,6 Using the metallic sample approach for stress wave induced fracturing, an understanding of the fracture behavior of brittle materials which perhaps is not always appropriate has been established in the open literature. An excellent summary of the metallic sample approach is provided by ref. 7 which summarizes the general beliefs prevalent at present regarding the impulsive behavior of brittle solids: "In the blasting process, rock breakage occurs primarily from tensile slabbing, beginning at a free face and proceeding back toward the explosive charge. The tensile waves formed by the reflection of incident compressive waves from two or more free faces will collide in the rock, resulting in large localized tensile stresses. Fractures formed by the interaction of these tensile stresses begin at the apex of the free face planes and progress back into the rock as shown...."

Jan 1, 1964

By L. Alan Weakly

The Bureau of Mines has pursued a program of research on mine illumination that has defined the coal miner's illumination needs. St. Joe Minerals Corporation, recognizing the need for improving the illumination of the working place in their mines, entered into a cooperative research agreement with the Bureau of Mines to utilize the Bureau’s expertise in this field. Some similarity in the environment, in which coal and hard rock miners work, has allowed the application of developed coal mine illumination technology and equipment to be utilized in hard rock, room and pillar mines.

Jan 1, 1979

By William P. Lohden

INTRODUCTION It is recognized that, for a variety of reasons, some companies in the mineral industry today are by no means cash-rich and, in fact, are reporting a growing proportion of long-term debt in their capital structures. A review of recent balance sheets of small, medium-size, and some larger companies, indicates that a fair number still have substantial positions in cash equivalents such as U.S. government issues and other short-term money market instruments. In part, this paper concerns itself with companies which have sufficient cash and equivalents and/or cash generation to internally finance mining projects or expansions but which, for some reason, choose to borrow funds. Misconceptions which appear to frequently underlie so-called "leveraging" decisions are explored in this paper. Also considered are those circumstances under which any company, including one that is cash-rich, should consider borrowing for a project in an amount beyond what would otherwise be necessary based upon its internal financing ability. I do not 'attempt to cover the raising of equity capital in public markets in this paper. OVERALL RETURN ON TOTAL POOL OF INVESTABLE CASH SHOULD INFLUENCE FINANCING DECISIONS If you approach an individual with an investment which can be financed from his savings, or by borrowing at a rate higher than he is earning on his savings, he will quickly tell you that to pay interest at a rate higher than he is earning would reduce his overall income. Assuming he is not currently considering any additional investment

Jan 1, 1977

By Oliver B. Hopkins

Peru produced approximately 17,466,620 bbl., of oil during 1937, or slightly less than the record high of 17,593,700 bbl. established during 1936. As in 1936, the entire output of the country was derived from the La Brea-Parinas, Lobitos-Restin and Zorritos fields in the northwestern part of the country. Outside of the proven areas, drilling was 'continued by the Peruvian Government in the northern province of Tumbes on the reserved zone at Zorritos. Drilling was carried out on three locations, two of which are understood to have been abandoned during the year. In southern Peru, further attention was given by Government engineers to the Pusi and Saman districts and plans are being worked out for the commencement of drilling operations in the near future in the vicinity of Pirin. Activities in the montaiia region in eastern Peru were continued by the Compafiia Petrolera El Ganso Azul. This company acquired the interest of the Selden Breck Co., and holds some 90,000 acres along the Pachitea River a few miles above its confluence with the Ucayali. During the year, the preparation of a landing place, the cutting of a 12-km. (71/2-mile) road from the river to the drill site, and the construction of a camp were undertaken. Equipment for drilling on this company's concessions has already arrived in South America. La Brea-Parinas Estate.—Production of crude oil on the La Brea-Parinas Estate of the International Petroleum Company Limited amounted to 14,722,754 bbl. during 1937, a decrease of 403,736 bbl. from the all-time high reached during 1936. The total production from 1890 to Dec. 31,1937, was 178,390,767 bbl. During 1937, a total of 141,653 ft. was drilled, 129,516 ft. in new wells and 12,137 in deepening existing wells. In all, 57 wells were completed, 47 of which produced oil, 2 were gas wells and 8 dry. holes. Twenty-nine wells were cleaned out or deepened during the year. The average depth of new wells completed during 1937 was 2367 ft. compared with 1984 ft. for the new wells completed during 1936. There was an increased use of rotary tools during the year and this method is now used to a greater extent than the cable-tool method, which formerly predominated. Of the 57 wells completed during the year, 31 were

Jan 1, 1938

By J. O. Nomland

DuRing the year 1939 the program of the California Arabian Standard Oil Co. in eastern Saudi Arabia consisted of drilling wells to increase the production of Dammam Dome. (This structure is also sometimes referred to as Dhahran Dome.) In addition, in other areas of the concession, wildcat wells are being drilled on geologically favorable structures. In the early wells drilled at Dhahran, production was at a depth of 2000 to 2200 ft. Since discovery of the "Arab zone" below 4300 ft., all of the later wells have been drilled to the deeper productive members. At present there are at Dhahran fivc wells in various stages of drilling or completion. In addition, 15 wells previously were drilled to the upper or lower zones. Although some of the early locations are exceptions, in general the spacing of the wells is at 3000 feet. Prospect testing consisted in drilling one well at Abu Hadriya and one at Ma'agala, about 100 miles northwest and 120 miles west of Dhahran. The first had attained a depth of 8655 ft. without encountering the main Darnmam productive zone, while the second was at a depth of 1372 ft. Both of these wildcat wells are on large dome structures. Production.—During the year 3,933,903 bbl. of approximately 35" gravity oil was produced, all from flowing wells. A part of this production was shipped in barges to the refinery at Bahrein. In early May a 40-mile 10-in. pipe line was completed to the deep-water terminal at Ras Tanura. The ceremony of first opening the valve for flow of oil into an ocean tanker was performed by King Abdulaziz Ibn Saud. Since that time tanker shipments have continued, both to Bahrein and to world markets. Only sufficient gas for camp purposes has been produced. Equipment.—A stabilization plant has been completed at Dhahran and plans have been made for a refinery at Ras Tanura. A modern camp is being built including power plant, central air-conditioning plant, radio station, employees' club and housing facilities for both married and single employees. Both the offices and dwellings are being air-conditioned. There is a hospital, with medical staff and nurses, providing facilities for both Saudi Arabs and Americans.

Jan 1, 1940

By J. O. Nomland

DuRing the year 1939 the program of the California Arabian Standard Oil Co. in eastern Saudi Arabia consisted of drilling wells to increase the production of Dammam Dome. (This structure is also sometimes referred to as Dhahran Dome.) In addition, in other areas of the concession, wildcat wells are being drilled on geologically favorable structures. In the early wells drilled at Dhahran, production was at a depth of 2000 to 2200 ft. Since discovery of the "Arab zone" below 4300 ft., all of the later wells have been drilled to the deeper productive members. At present there are at Dhahran fivc wells in various stages of drilling or completion. In addition, 15 wells previously were drilled to the upper or lower zones. Although some of the early locations are exceptions, in general the spacing of the wells is at 3000 feet. Prospect testing consisted in drilling one well at Abu Hadriya and one at Ma'agala, about 100 miles northwest and 120 miles west of Dhahran. The first had attained a depth of 8655 ft. without encountering the main Darnmam productive zone, while the second was at a depth of 1372 ft. Both of these wildcat wells are on large dome structures. Production.—During the year 3,933,903 bbl. of approximately 35" gravity oil was produced, all from flowing wells. A part of this production was shipped in barges to the refinery at Bahrein. In early May a 40-mile 10-in. pipe line was completed to the deep-water terminal at Ras Tanura. The ceremony of first opening the valve for flow of oil into an ocean tanker was performed by King Abdulaziz Ibn Saud. Since that time tanker shipments have continued, both to Bahrein and to world markets. Only sufficient gas for camp purposes has been produced. Equipment.—A stabilization plant has been completed at Dhahran and plans have been made for a refinery at Ras Tanura. A modern camp is being built including power plant, central air-conditioning plant, radio station, employees' club and housing facilities for both married and single employees. Both the offices and dwellings are being air-conditioned. There is a hospital, with medical staff and nurses, providing facilities for both Saudi Arabs and Americans.

Jan 1, 1940

By H. W. McCue

In 1945 the number of oil wells drilled was less than in 1944 but the number of gas wells was greater. The oil wells numbered 176, completed for an initial production of 25,214 bbl., an average of 143 bbl. per well as against a total in 1944 of 245 drilled for 32,886 bbl., or 134 bbl. per well. All of these wells were in proven areas and no new discoveries

Jan 1, 1946

By R. V. Whetsel, V. R. Garfias

The production of petroleum in Mexico during 1933 totaled 33,430,-000 bbl., or 625,000 bbl. more than in the previous year. This is the first time since the peak in 1921 that the declining trend of output has been reversed. Drilling activity in the proven areas of the Isthmus of Tehuantepec and the Northern fields increased substantially during the year. The completion of two producers in the Poza Rica area south of Tuxpam and a shallow gas well in the Camargo district near the American border were the outstanding features of development. Late in September the Northern fields and the oil port of Tampico were swept by a hurricane followed by floods which caused loss of life and heavy damage to the City of Tampico and to transportation, tank farms and refineries. For three weeks, owing to the silting of the Tampico Bar and destruction of terminal facilities, no oil could be shipped for export. About half the wells of the Northern fields were closed for a period of 30 days. The prompt and effective steps taken by General Macias, chief of military operations, prevented the spread of epidemics and any serious aftermath of the catastrophe.

Jan 1, 1934

By J. L. Jernegan

In this paper I propose to give a short and, I must confess, a rather incomplete description, as regards many details, of the process used in Chicago, Ill., for smelting the argentiferous ores of the far West, and shall confine myself in this description, principally, to the process used at the Chicago Silver Smelting and Refining Company's Works, known as the Balbach process, as all the other smelting works in that city follow the same method, with the exception of one, which has the Cordurié process for the desilverization of argentiferous lead. In all, there are five silver smelting and refining works in and near the city of Chicago. The Chicago Silver Smelting and Refining Company's Works are situated at the little station of South Lynne, about seven miles south from Chicago. The plant at these works consists of one horizontal steam-engine, principally used for running the ore pulverizer, four reverberatory smelting-furnaces, connected by horizontal flues with a common chimney 85 feet high, three lead-softening furnaces, one so-called zinc or mixing furnace, one separating furnace or liquation hearth, one lead-refining furnace, three zinc distillation retorts, one English cupellation furnace, supplied with blast by a No. 3 Sturtevant blower, which is run by a small steam-engine having a vertical tubular boiler, and an assay office, in which there are two windfurnaces of the ordinary construction, and also a small muffle furnace. The assay office is supplied with all the necessary apparatus and reagents for fire assaying. There are also a superintendent's office, various store-rooms for coke and charcoal, and for the preparation of fire-clay, etc. Recently a small slag hearth (Krummofen) with one tuyere, has been put up for the purpose of working over such slags as assay too high in silver and lead to be thrown away, of which there are large amounts. The principal ore worked while I was in the employ of the company was that of the well known Emma mine in Utah, and also small quantities of Colorado ore. The character of the Emma ore is well known to most members of the Institute. In consists principally of ferruginous mixtures of carbonate and oxide of lead, oxide

By L. M. Barker, E. G. Lewis

THE literature of milling is replete with papers devoted to the subject of ball milling, all of which no doubt have contributed in one way or another to progress in that art. In this paper reference will be made to only a few of the many authors, but the value of the contributions of all who have written on that subject is hereby acknowledged. With a few exceptions the efforts of most students of the subject have been devoted to laboratory investigations of principles. Davis1 was one of the first to report on plant-scale investigations and to present to mill men certain criteria for the guidance of ball-milling practices. His conclusions with respect to the significance of sizing analyses of classifier sands in their relation to the factors of mill speed and ball sizing are particularly referred to. Those conclusions were: I. If the balls are large or the speed of the mill is high, crowding will appear at the finer sizes in the classifier sands. 2. If the balls are small or the speed is low, crowding will appear at the coarser sizes in the classifier sands. 3. The indications are that best efficiency is obtained when the screen analysis of the sands show a minimum crowding at any size. The last conclusion was qualified by the statement that it had not been proved conclusively. It is surprising, however, that the literature of later years reveals little evidence that millmen have made any serious attempt to apply those criteria. This may, perhaps, be explained by the fact that the average plant-scale ball-milling problem presents so many variables that an investigation of any one of them encounters the problem of control of the others-a problem that often is unsurmountable in a small plant. In a large plant, in which there is a duplication of grinding units in parallel operation, opportunity may be afforded for determining the value of such criteria. Nevertheless, a study of published data from grinding circuits of both large and small plants suggests that either Davis' criteria have been tried and found inapplicable or have never been given consideration. For the purpose of testing Davis' conclusions and with improvement of ballmilling efficiency as the final objective, a test program was initiated in the concentrator of the New Cornelia branch of the Phelps Dodge Corporation early in 1938. The practices of that plant have already been described.2 The fine-grinding units are arranged so that any one of eight units may be operated as a test unit and its results compared with those of the remaining units. All units receive similar feed from a common storage bin, in which the product of the fine-crushing plant is bedded by traveling tripper. The ball mills are all similar in size and operated at the same speeds, and are individually metered. The feeder conveyors of each unit are equipped with Merrick weightometers. The test program as initially outlined proposed investigation of the following:

Jan 1, 1941

By S. W. Hazen

The use of operations research and computer techniques continued to expand during 1967. A number of mining companies either obtained computers or were experimenting with their use through service bureaus. This trend was also evident in the Canadian mining industry. Although the annual Symposium and Short Course on Computers and Operations Research in Mineral Industries was not held in 1967, technical periodicals like MINING ENGINEERING, Mining Congress Journal and Engineering and Mining Journal stepped up their coverage on the subject. The annual AIME meeting had eight papers in two sessions and one session on Operations Research was held at the SME Fall Meeting in Las Vegas.

Jan 2, 1968

By Adrian Brown

INTRODUCTION The primary tool which is available to improve the stability of an open pit mine at a given slope angle is control of groundwater pressure. This paper sets out the methods by which water pressure control can be achieved in large mines in different materials. The emphasis of this paper is on large mine slopes because. these slopes exhibit the greatest need for groundwater control, the greatest economic benefit from groundwater control, and the greatest technical challenge in achieving groundwater control. STABILIZATION USING MTER PRESSURE CONTROL Groundwater pressures reduce the stability of slopes in two fundamental ways, as shown schematically in Figure 1. In the example, a horizontal failure surface intersects a vertical joint or weak zone. Water pressure acts: o On the base plane to reduce the normal force on the sliding surface and hence reduce frictional resistance to sliding, and o On the vertical back plane, to create a driving force for the system.

Jan 1, 1983

By F. J. Haller

The need for permanent, fireproof support indicated structural steel sets. Experience over the past six years, involving more than five miles of permanent underground openings, has proved that steel is permanent, safer and, in the long run, cheaper than either treated or untreated wood supports. Excavation is reduced, as are installation, transportation, and handling costs. A number of hazards are reduced or eliminated by the use of steel.

Jan 4, 1950

By Harold L. Walker

ENGINEERING educators have recently been discussing the advisability of extending the undergraduate curricula to five or six years, and a plan has also been proposed requiring a preliminary period of study in the liberal arts college before admission to the engineering college. Extension of the undergraduate curricula has been suggested as a means of more fully covering the subject matter in the major field of study. Interest in this proposed plan of requiring a preliminary period of study in the liberal arts college has been heightened through a bill recently introduced in the legislature of the State of New York. This plan intends to give a more professional status to engineering, and credit for these additional years of study would be allowed to those engineers applying for professional licensure. As a result of the interest in engineering curricula and due to the impetus given by these proposed plans a general reexamination of curricula has been conducted by a large number of schools with the stated purpose of determining if the present curricula are meeting the aims and scopes of engineering education.

Jan 1, 1940

By Russell A. Carter

Although significant phosphate mining activity has occurred in four western states-Idaho, Montana, Utah, and Wyoming-southeastern Idaho contains the largest, most easily mineable reserves, and mining has focused there. More than half of the western phosphate field's economic reserves are within a 32 x 96-km (20 x 60-mile) rectangle bounded by Montpelier, Idaho, on the south, Soda Springs on the west, and Grays Lake on the east. A large amount of this land lies within the boundaries of the Caribou National Forest.

Jan 1, 1978

By J. D. Price, W. M. Bertholf

A. C. RICHARDSON*—First of all, [ think that the paper represents a lot more work, study, and correlation than has been indicated by the brief talk by Mr. Price. I like the way he started out and described the areas from which the samples were obtained, the locations of the washing plants, the available tonnages, and other background information with which to evaluate the data he submitted later on. Then I like the way in which he described the various types of washing plants, the tonnages handled and the difficulties of the washing problems; showing the amount of material that lies close to the specific gravity at which the washing separation is made. Later he gave figures from washing plant operations showing recoveries and cleaning efficiencies. He then discussed his own plant at Pueblo. It is the same old plant, I think, that I worked around a good many years ago. It is unusual to find a plant treating nearly 5000 tons of coal a day on tables. But this table plant is, I believe, more efficient than is indicated by the figures that Mr. Price gave. To determine the efficiency of a cleaning operation or to compare it with another it is necessary to consider the quantity and character of the material close to the specific gravity at which the separation is made. It is not fair, I believe, to penalize the table operation by something like 4 pct of out-of-place-material as he has done here. The variety and difficulty of the coals that he has to wash, the continuous shift and change in their composition make a very difficult cleaning problem and the table performance is excellent. I believe that the information in this paper will be of interest and value to anyone operating or planning to build a coal cleaning plant in this or other areas; particularly where the cleaning of fine coal is a problem. The data may be used for comparative purposes in determining the relative efficiencies of other cleaning plant separations. E. D. HAIGLER*—What is a Baum jig? J. D. PRICE (authors' reply)—A Baum-type jig is one in which the pulsations of the water is secured by means of a pulsating air current applied on top of the water. I imagine you are all familiar with the old plunger-type jig which is in effect a U tube in which a plunger on one side of the U, moving up and down, causes a corresponding pulsation on the far side of the jig. In the Baum jig, the pulsating air current is applied on the surface of the water on one side of the U tube of the jig and gives a corresponding pulsation on the other. It is also commonly known as a pneumatic jig. The control of the rise and fall of the water in the jig body proper is under much better control than it is in any of the other type jigs. Mr. Richardson could enlarge on that feature, for I know that he has had considerable experience with these jigs. A. C. RICHARDSON—You have asked how to control a Baum-type jig. The pulsations in a Baum jig can be modified and regulated to a marked degree by the amount of water admitted to the jig and by the adjustments of the valve which regulates the manner in which air is admitted. The number of pulsations per minute is controlled by the number of cycles of the air valve. Thirty to forty cycles per minute is a good speed for large jigs treating coarse sizes of cod. With an air valve it is possible to modify the time-velocity curve of the pulsating water to some extent which in turn determines the action in a jig bed. Within limits the following parts of the air valve cycle may be regulated: (1) the rate and period of air admission, (2) the period of air expansion, (3) the rate and period of air exhaust, and (4) the period of air compression. The rate and period of air admission determines the acceleration of the water at the beginning of the pulsion stroke and the amplitude of the stroke. The period of air expansion, after inlet port is closed, is one in which the water has reached the desired velocity, positive acceleration reduced, and the bed held in a mobile condition. The rate and period of the air exhaust can be adjusted to modify the degree of suction and so modify the manner in which the particles in the bed stratify. The compression period, alter the exhaust port closes and before the intake port opens may be used to advantage in retarding the downward velocity of water during the suction stroke. An ideal jig stroke is one in which during the up stroke the bed is lifted slowly in a mass and opens up like an accordian with the bottom layers dropping away first. With the bed open and mobile the particles adjust themselves according to their hindered settling rates. During the down stroke, while the bed is still open the particles of high specific gravity are accelerated toward the bottom layers. It is possible to approach this stroke with all types of jigs but it is less difficult to approximate it with a Baum jig.

Jan 1, 1950

It appears that Utah is about to add another mining district to its already impressive roster. This time it is the Great Salt Lake, whose high-mineral content waters are being subjected to intensive study aimed toward the recovery of potassium, magnesium and lithium compounds by solar evaporation techniques. Among the firms conducting such experiments is Lithium Corporation of America, which, in a joint venture with West Germany's Salzdetfurth A.G., is operating evaporating ponds and running engineering tests at a site near Little Mountain, about ten miles west of Ogden. Here, on the clay flats along the northern portion of the lake, LCA holds leases and options totalling about 55,000 acres in the Bear River Basin.

Jan 7, 1966