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By G. D. Tranter

The importance of ladle and teeming practice and its relationship to the yield and quality of the product has focused considerable attention on this phase of open-hearth operation. Inherently bad steel cannot be perfected by manipulation during teeming, but through the proper handling of "off heats" serious losses, which in many cases arise, can be greatly minimized. Conversely, good steel can be ruined as a result of poor workmanship in the pit, and rendered unsuitable for application to orders where exacting surface and physical requirements are essential. Sufficient evidence has been secured to warrant careful investigation of pit operations when an abnormal number of basic defects develop in the semifinished product or are found on the inspection table. This paper is written from the standpoint of the problems involved in making satisfactory ingots for sheet rolling. Furthermore, since rimming steel is almost universally used for manufacture of sheet, the data presented herein refer particularly to that type of steel. Going back some 30 years in open-hearth history, the word "pit" properly described the hole into which the ladle was lowered to receive the metal tapped from the furnace. The working space was necessarily limited, and the disposal of slag and metal overflowing the ladle or lost because of breakouts presented a serious problem. The equipment, of course, was rather crude in the light of present-day development. Often no ladle stands were provided, the ladle being hung on the crane beneath the runner. When delayed taps occurred, the ladle was often held in position for many hours, thus tying up pit operations and causing delays to adjacent furnaces. Because of crowded conditions, slag thimbles were not used and a network of cast-steel triangles and old tapping bars, placed before the heat was tapped, was the means for removing slag from the hole. Furnaces of different capacities were used

Jan 1, 1935

By G. D. Tranter

The importance of ladle and teeming practice and its relationship to the yield and quality of the product has focused considerable attention on this phase of open-hearth operation. Inherently bad steel cannot be perfected by manipulation during teeming, but through the proper handling of "off heats" serious losses, which in many cases arise, can be greatly minimized. Conversely, good steel can be ruined as a result of poor workmanship in the pit, and rendered unsuitable for application to orders where exacting surface and physical requirements are essential. Sufficient evidence has been secured to warrant careful investigation of pit operations when an abnormal number of basic defects develop in the semifinished product or are found on the inspection table. This paper is written from the standpoint of the problems involved in making satisfactory ingots for sheet rolling. Furthermore, since rimming steel is almost universally used for manufacture of sheet, the data presented herein refer particularly to that type of steel. Going back some 30 years in open-hearth history, the word "pit" properly described the hole into which the ladle was lowered to receive the metal tapped from the furnace. The working space was necessarily limited, and the disposal of slag and metal overflowing the ladle or lost because of breakouts presented a serious problem. The equipment, of course, was rather crude in the light of present-day development. Often no ladle stands were provided, the ladle being hung on the crane beneath the runner. When delayed taps occurred, the ladle was often held in position for many hours, thus tying up pit operations and causing delays to adjacent furnaces. Because of crowded conditions, slag thimbles were not used and a network of cast-steel triangles and old tapping bars, placed before the heat was tapped, was the means for removing slag from the hole. Furnaces of different capacities were used

Jan 1, 1935

By Evan Evans

IT is appropriate to evaluate 1947 in review as a year of a peacetime record production of about 676,000,000 tons of coal (anthracite and bituminous), closely approaching the extraordinary wartime output in 1944. Considering the general price-wage inflation, it is in point to note that the coal industry sustained the highest wages paid to workers in any major industry, but that coal prices at wholesale levels have risen much less percentage wise than the average for all commodities. The sellers' market continues to prevail. In addition to serving our own country's enormous needs, our coal industry is exporting extraordinary tonnages overseas. This unusual export demand is likely to continue for a while. Moreover, the demand in Europe for American coal mining machinery is a real tribute to the management efficiency of our modern mechanized coal industry. Competitively, the petroleum industry is concerned over its long-term supply, and already a synthetic fuels industry is being publicly advocated. In due time coal and lignite are bound to be

Jan 1, 1948

By W. C. Maurer

A drilling-rate formula for roller-cone bits is derived from rock crater-ing mechanisms. This formula holds for "perfect cleaning", which is defined as the condition where all of the rock debris is removed between tooth impacts. Under these conditions, the drilling rate is directly proportional to the rotary speed and to the bit weight squared, and inversely proportional to the bit diameter squared and to the rock strength squared. Under imperfect cleaning conditions, such m those usually present in field drilling, re-grinding of the cuttings occurs under the bit, and the drilling rates fall below those for perfect cleaning. INTRODUCTION Drilling with a roller-cone bit consists of two fundamental operations: the formation of craters under the bit teeth, and the removal of the broken rock from the craters. To delineate the mechanisms of drilling, it is first necessary to understand the mechanisms involved in the formation of individual craters and then to relate these mechanisms to the over-all drilling operation. CRATER FORMATION When a bit tooth impacts a rock, the rock is elastically deformed until the crushing strength of the rock is exceeded, at which time a wedge of crushed rock is formed below the tooth1, 2 as shown in Fig. 1. As additional force is applied to the tooth, the crushed material is compressed and exerts high lateral forces on the solid material surrounding the crushed wedge.- en these forces become sufficiently high, fractures are initiated below the tooth and propagate to the free surface of the rock. The trajectories of these fractures intersect the principal stresses at a constant angle,'s4, as predicted by both Mohr's and Griffith's theories of failure. It has been experimentally 3,1 .6 that the volume of an impact crater, V,, varies as where Ec is the total energy imparted to the rock during the formation of the crater, and E is the threshold energy required before cratering is initiated (Fig. 2). Indexing experiments' have shown that, when there is a second free face to which the crater can fracture, a larger volume of material is removed and that above a transition zone there is a linear relationship between V, and Eo., which has a slope equal to the relationship for the single crater. The beneficial effect of indexing tends to offset the threshold energy requirement to a large extent, as shown in Fig. 2, and the relationship is closely represented by Rate-of-loading effects have been used to explain the nonproportional relationships usually obtained between drilling rate and rotary speed. The data4, in Fig. 3 show that the Ec/Vc parameter remained constant for craters produced with impact velocities ranging from 10 to 8,000 ft/sec. Since no rate-of-loading effects were detected over this wide range of loading rates, it seems improbable that there would be detectable rate-of-loading effects present in the small changes in impact velocities produced by varying the rotary speed. The writer has shown (Fig. 4) that, for craters produced in rock by impacting spheres, where X is the depth of penetration. Simon2 has shown that this relationship also holds for craters produced in rock by penetrating wedge-shaped chisels. The energy used in crater formation is

By Wallace E. Pratt

UNDER the stimulus of war psychology the American public has grown confused and jittery in its thinking on the subject of this nation's petroleum resources. This confusion arises from the failure of the average citizen, and even of many leaders in government, in our armed forces, and in the petroleum industry itself, to distinguish between our proved reserves of petroleum in the several oil-producing states and the total petroleum re- sources available to this nation. Leaders and public alike examine the accepted estimates of our proved reserves and thoughtlessly conclude that these estimates represent the total of our petroleum resources. Our fears are aggravated if we turn to the statistics on oil-finding and observe that the discovery of new reserves has waned decidedly in recent years. This confusion is dangerous because, under its influence, ill - considered policies spring up and flourish, choking out the most valuable fruits of the long experience of the American petroleum industry.

Jan 1, 1944

Tooele Flue-type Cottrell Treater Discussion of the-paper of A. B. YOUNG, to be presented at the New York meeting, February, 1921, and printed to accompany MINING AND METALLURGY No. 162, June, 1920. HARRY V. WELCH,* Los Angeles, Calif. (written discussion).-The basic requirement in the electrostatic process of electrical precipitation is that gases containing solid particles in suspension are forced to pass through an electrical field consisting of an insulated high-potential wire, or other type of discharge member, and a grounded plate, or other, type .of collecting member. Commercial. operation and efficiency of precipitation are secured by electrical and structural arrangements to provide the maximum value of the variable factors modifying the degree of precipitation. That is to say: 1. A unidirectional flow, of high-potential current is vastly more effective in precipitation than a high potential alternating-current flow.

Jan 2, 1921

By R. E. Allen

ONE of the most unusual oil field engineering accomplishments of the past two years is the development and rapid advance in the directed drilling of wells. Directed drilling as referred to herein is the controlled steering of the drill stem in the required direction to a given location in the oil sand. The deliberate drifting of holes is an act so far removed from what has been considered good drilling practice that all of the old questions of correlation, drillability and production difficulties are revived. Only a few years ago, during the boom days of Seminole and Santa Fe Springs, the crooked-hole problem, as it was then called, occupied a primary position among the topics of the day in the fields of California and the Mid-Continent. The net result of all the discussion and study at that time was the conclusion that oil wells should be drilled with as little deviation from

Jan 1, 1933

By Martin Rubenstein

CdS crystals have been grown from a number of metallic solvents such as bismuth, tin, lead, and cadmium. Etching studies have shown that plastic deformation occurs if the crystals are not removed from the solvent prior to the solidification of the solvent, on cooling. The deformed crystals show a umique exciton fluorescence as a function of edge dislocation density. If one grows the CdS in the eutectic alloy of the above four metals (commonly called Wood's metal) the crystals can be removed from the solvent with hot water and no plastic deformation occurs. In this paper, the liquidus solubility measurements of CdS, as a function of temperature, are presented. The data were obtained using a high -temperature filtration technique. CADMIUM-SULFIDE crystals have been grown from a number of metallic solvents1 such as cadmium, bismuth, tin, and lead. Liquidus solubilities of CdS in cadmium,2 bismuth,3 and tin4 have already been measured. Crystals of CdS, in all four metals, have been grown by solution growth: 1) by cooling a saturated solution and 2) by a solution transport method.1'"1 CdS crystals grown in these four solvents have a few characteristics in common: 1) 1.8°K photolumines-cent emission consisted mainly of the radiative recombination of the bound exciton commonly known as I,, 2) slip lines which could easily be seen by the naked eye, and 3) edge dislocation densities in the order of l05 per cu cm.1 It was decided that these slip lines and the high edge dislocation densities were caused by a plastic deformation of the CdS crystals. It was felt that this plastic deformation did not occur during the growth of the crystals nor during the cooling of the solution, but did occur when the solvent which was in contact with the crystals froze. If these assumptions were valid, the slip lines and the high number of dislocations could be reduced or eliminated by removing the crystals from the solvent before the solvent froze. Since crystals of CdS had already been grown separately in such solvents as bismuth, lead, tin, and cadmium, it was felt that crystals could be grown in a eutectic mixture of these four metals. In this work a eutectic (or near eutectic) mixture of bismuth, lead, tin and cadmium in the proportion 50, 26.5, 13.5, and 10 wt pct, respectively, was used to grow CdS crystals. Such a mixture has a melting point of about 70°C and is close in composition to the alloy commonly known as Wood's metals. If the crystals could be grown from this mixture of solvents, and if hot water (>75°C) could be used to separate the crystals of CdS from the metallic solvent, it was hoped that CdS crystals could be grown with little or no plastic deformation which had been ob- served when crystals were grown from these solvents uncombined. CdS crystals were grown from this low melting eutectic mixture of bismuth, lead, tin, and cadmium using the solvent transport method. CdS powder and the appropriate amount of metals were sealed in a quartz tube under a pressure of about 5 X 10-6 torr. This ampule was then placed in a vertical position in a furnace. The temperature was raised to about 900°C. The furnace was designed so that the top of the liquid column within the ampule was between 10° to 40°C higher than the bottom of the liquid column. These temperatures were measured on the outside of the quartz ampule. The ampule was maintained at temperature for 7 to 14 days (depending on the temperature at which transport was taking place) and then the furnace temperature was lowered until the temperature was about 125°C. The ampule was then removed from the furnace, placed in water maintained at about 90°C, and opened in this 90°C environment. The crystals could then be removed from this two-phase liquid (Wood's metal and water) by mechanically picking them out. Alternatively, the crystals could be quantitatively removed by adding an excess of mercury to the mixture of metals, crystals, and hot water. The hot solution of metals and the hot water could be evacuated using a small diameter tube connected to a vacuum. Small amounts of mercury and water could be removed by heating the crystals in vacuum. Crystals prepared using this technique showed no evidence of slip. However, some of these crystals did show edge dislocation densities as high as l04 per cu cm. Some few selected crystals showed no dislocations. Single crystals of CdS were grown as large as 5 by 5 by 0.5 mm. The ampules for the growth of these crystals were 13 mm O.D., 11 mm I.D., 150 mm! LIQUIDUS SOLUBILITY MEASUREMENTS The CdS starting materials was G.E. 118-8-2 powder which was fired in H2S at 1000°C, and then a vapor transport technique5 was applied to produce a "sound" mass of CdS. The Wood's metal was prepared by weighing out bismuth, lead, tin, and cadmium in the proportions of 50, 26.5, 13.5, and 10 wt pct, respectively. The bismuth, cadmium, and lead were from the American Smelting and Refining Co. (ASARCO) and all had purities of 99.999+ pct. The tin was 99.9999 pct spectroscopic grade from the Vulcan Materials Co. The appropriate mixture was placed in a quartz tube, evacuated to a pressure of 5 X 10-6 torr, melted to a liquid, cooled to room temperature under this same vacuum. This ingot was then placed in another quartz tube, evacuated to 5 x l0-6 torr, and sealed off under vacuum. The ampule was then horizontally placed in a furnace. The temperature was raised to 600°C, and over a period of several hours the ampule was vigorously shaken several times. The ampule was then removed from the furnace, and the metallic liquid was

Jan 1, 1970

The beginning of Colorado's mining industry is linked on one side with that of the Appalachian districts and on the other side with that of California, because the first discoveries were made by pioneers when on their way from Georgia to California. In the summer of 1849 a party of seven Georgians were taking a herd of thoroughbred horses across the continent to the Pacific coast. They reached Camp Lyon, on the Arkansas river, in October, and, meeting James Dempsey, a Government guide, they were persuaded by him that it was too late to cross the mountains that season. His advice was accepted, and, moving northward, they established a winter camp at the junction of Cherry creek with the Platte, close to the site of the city of Denver. Upon a sand-bar, lining the south side of the river, they built two cabins. During the closing months of 1849 they prospected the alluvial banks of Cherry creek, but they made no attempt to penetrate into the mountain canyons, near them, westward, for fear of the Indians.* They found gold in several places along Cherry creek, and particularly at a spot 16 miles up the stream from their camp. From the feathers of the wild geese that they shot they obtained quills in which they placed their gold-dust. This party of Georgians consisted of Dr. L. J. Russell and his brother, Green Russell, also A. T. Lloyd, G. W. Kiker, and P. H. Clark. Early in 1850 they crossed the main range of the Rocky Mountains by the Bridger pass and went on to California. They mined near Downieville, and were successful. Occasionally mention was made by them of the gold

Jan 1, 1932

By Gustav Egloff

AN unexpected and unprecedented demand for its products now challenges the petroleum industry. Between 1939 wand 1946, domestic oil demand increased nearly 45 per cent and in the first half of 1947 it was 10 per cent higher than in 1946. In 1939 the United States produced 1,264,962. 000 bbl of crude oil and indications are that about 1,860,000,000 bbl will be produced in 1947, a 47 per cent increase. Runs to stills are more than keeping pace with production. The crude capacity of 365 operating refineries is rated as 5,400.000 bbl daily and almost 100 per cent of this capacity was running crude oil in August 1947. The oil industry is cognizant of our need for a greater volume of petroleum products and is expending the huge stun of four billion dollars on exploration. production. transportation, refining. and marketing of petroleum. Of this amount about half will be spent on exploration and production. a billion on refining. and another billion on transportation and marketing facilities.

Jan 1, 1947

By Irwin H. Cornell

BRIEFLY stated, the history of the St. Joseph Lead Co. is the story of how a group of men, working for ten years as officers without salaries and stockholders without dividends, developed a small mine in Missouri into what became a large and prosperous corporation. Their courage and faith in the scattered surface deposits of lead coupled with the management's engineering vision and sound financial judgment should prove an inspiration to present-day mining operators and investors. In 1717, John Law's company, known as "The Company of the West," was formed in France and letters patent were granted, for a period of 25 years by Louis XV, for exploration in the Mississippi River Valley. One of the underlying purposes of the expedition, headed by Mr. Renault and Mr. La Motte, a French metallurgist, was development of the lead mines in the area now known as Southeast Missouri.

Jan 1, 1947

By Dr. O’Neil Thomas J., Donald W. Gentry

"There are two characters to the value of mining properties-one mine may have a value, owing to its real intrinsic worth; an- other (having no intrinsic value) may have a value by being so situated as to harass the working of the really valuable mine-in mining camps one is looked upon as much of ligitimate enterprise as the other.'' -Victor Clement to Simeon Reed, Wardner, Jan. 11, 1890, Reed Mss. APPROACHES TO VALUATION Value and costs are two terms basic to financial analysis which cause, perhaps, the greatest amount of misunderstanding in mine valuation studies. When discussing the value of an asset or the costs of producing a product, it is absolutely essential that the speaker define the terms being used. There are many types of value and many categories of costs. Without specific accompanying definitions, value and cost data are not very meaningful. Value refers to a measure of the desirability of ownership of property. Some of the types of value which might be encountered in a mine valuation study are: 1) Market value 2) Full cash value 3) Salvage value 4) Replacement value 5) Capitalized value 6) Book value 7) Assessed value 8) Insured value Each of these has a specific meaning which can be applied to determine a monetary amount in a specific situation. The major item of interest here is the broader question of "what is the value of the mine?" or "what is the mine worth?" In this case, we are speaking of market value. Market value is the value (price) established in a public market by ex- changes between a willing buyer and a willing seller when neither is under duress to complete the transaction. Market value fluctuates with the degree of willingness of the buyer and seller and with the conditions of the sale. The use of the term market suggests the idea of barter. When numerous sales occur on a market, the

Jan 1, 1984

By E. J. Krokroskia

Fletcher Mill is located in the southern part of the New Lead Belt in Southeastern Missouri, in the northwestern part of Reynolds County. Shaft sinking began in July, 1964. The mill went on stream in February, 1967, and reached the designed rate of 5,000 tons per day in July, 1968. The ore occurs approximately 1,000 feet below the surface as disseminated deposits of galena, sphalerite and chalcopyrite. There is no oxidation within the ore body and dissemination is not fine enough to present liberation problems with a normal grind. Mining is by the room and pillar method with rubber-tired diesel- propelled drilling and loading equipment. The ore is dumped through a 27-inch square grizzly into a 5,000-ton pocket. The underground primary crusher is automatically fed by a vibrating feeder and discharges directly into skip measuring bins. Hoisting is automatic, in balance, with 8. 5-ton skips dumping into a 1,000-ton mill bin. MILL The concentrator is a 5, 000 tons-per-day single section plant equipped to produce lead, zinc and copper concentrates. Contained under 35, 347 square feet of roof, without fine ore storage or remote crushing, and with sufficient automation to be operated by one man, the plant is compact, unique, and efficient in operation. The design

Jan 1, 1970

By C. A. Heiland

IN the third year of war, geophysical oil exploration broke all records to keep pace with the demand for increased reserves. Geophysical prospecting for strategic and other minerals also grew in scope. The trend of geophysical oil exploration throughout the war is indicated in Fig. 1. This figure resembles the one presented in the last annual review issue of M&M (February 1944, p. 62), corrected for data on-operations in the last months of 1943 and extended into 1944. The average number of geophysical oil prospecting crews in the field in 1944 was 451, whereas the total in 1943 was 340. An upward trend in the use of all geophysical methods is clearly evident throughout the year. Seismic operations were 67 per cent, gravimeter surveys 28 per cent, and other methods 5 per cent of the total. Seismic reflection and refraction crews increased 181/2 per cent over the 1943 average, gravimeter operations increased 73 per cent, and other methods gained 92 per cent. The increase in seismic and gravimeter operations, particularly the latter, is probably due to an increased production of equipment and the organization of new service companies. Miscellaneous methods gained largely through a revival of magnetometer work, and an increase in the use of torsion balances and electrical equipment. In comparison with the prewar average of 1941, it is noteworthy that seismic operations increased 58 per cent, gravimeter operations 88 per cent, and miscellaneous other methods gained as much as 283 per cent. Unfortunately the expansion in the number of geophysical crews does not indicate a proportionate increase in efficiency or in areal coverage, as will be brought out later.

Jan 1, 1945

By D. L. McElroy

It is too broad a statement to say that the mine car is the most important unit in a haulage system, but almost every mining man will admit that it is one of the most important. The mine car is to the mine haulage system what the railroad car is to the railroads; the main purpose in each instance is to move the greatest number of ton-miles of material at the least cost. The data presented in this paper are taken from a study of mine haulage conducted by the School of Mines of West Virginia University at 42 mines in 8 coal fields of Wrest Virginia. The study was made possible by a graduate fellowship of the School of Mines and the cooperation of the mining companies of the state. Three important factors in the use of mine cars in West Virginia are: (I) the number of mine cars in use per loader; (2) the capacity of mine cars; (3) the distribution of mine cars. ("Loaders" in this paper refers to all men loading coal, whether manually or mechanically.) During the World War many mine managers were annoyed by the reduction of efficiency and production caused by railroad-car shortages. Today relatively little complaint is heard about a shortage of mine cars, yet possibly 50 to 75 per cent. of the mines in West Virginia are suffering from this cause of reduced production and increased costs. The railroads have solved their car shortage by placing in service more cars of larger capacity and better design. Many coal mines in West Virginia should solve a part of their cost problems by the same simple procedure. Such a procedure requires an initial outlay of capital, but there is little doubt that this will be repaid, with a good return on the investment. Determining Number of Cars Needed There can be no mathematical rule to determine the number of cars which should be in use per loader in a coal mine, because numerous factors such as concentration of mining, system of haulage, car capacity, speed of haulage, distance of working places from tipple, and so forth, affect materially the number of cars in use. These factors in turn are more or less determined by height of bed, character of roof and coal,

Jan 1, 1931

By Robert M. Keeney

Important recent developments in the melting and annealing of non-ferrous metals include: 1. Melting of nickel silver in the vertical ring induction furnace. 2. Electric melting of stereotype metal. 3. The rotary-drum gas-fired brass melting furnace. 4. The low-frequency coreless induction furnace. 5. Finishing annealing of brass sheets with city gas1 replacing wood in the large brass-rolling mill. 6. Electric annealing of brass and copper tubing and sheets. 7. Replacement of oil by gas and electricity in the annealing of nickel-silver shells and stampings. Melting Nickel Silver in Vertical Ring Induction Furnace Although over 90 per cent. of the output of the brass rolling mills in the United States is now melted in electric furnaces,2 until recently a considerable part of the output of nickel silver has been the product of the pit fire. The application of the electric furnace to the melting of nickel silver has been slow for several reasons: (I) Until recently no lining has been available that gave a satisfactory life in the vertical ring induction furnace when melting nickel silver; (2) the rocking arc furnace so widely used in the foundry does not appear to have been favored by the rolling mill for melting nickel silver, possibly because the gases present may affect the quality of the alloy; and (3) the exclusive rights to the use of the high-frequency coreless induction furnace (which has proved very satisfactory for melting nickel silver) for the wrought brass industry are controlled by one concern. A little over one year ago the first vertical ring induction furnace to be used for melting nickel silver in the Naugatuck Valley was placed in operation. This was followed by two more in the same mill, and by

Jan 1, 1930

By P. D. P. Hamilton

In any mining district where benefication of the ores is practiced, one can usually observe several types of flow sheets even though the various producers are milling ore from the same geological formations. It is obviously impossible to describe all the mills in the Porcupine district. However, the following description of some of them is of particular interest in that it shows where one mill has paid particular attention to corduroy blanket practice; one to gravity concentration of sulfides for intensive cyanidation of the values therein contained; one to flotation of values and cyanidation of this product only; and others where small variations of standard all-slime cyanidation practice prevail. In all cases it will be seen that cyanidation is the basic principle. Discussions involving the difference in the flow sheets and the reasons for them will always be of value to those interested in the art. The author of this article, however, believes that such discussions should originate from the operators of the mills under discussion. For this reason no comparisons or discussion will be included in the description of the mills mentioned. Should any reader of this article obtain information therefrom which will be of value to him in helping to solve his own particular problems, the author will consider that the article has satisfactorily served its purpose. All values mentioned throughout this article are based on the value of gold at $20.67 per ounce. Coniaurum Mines, Limited The ore of the Coniaurium mines consists of a mineralized schist and quartz containing about 2.5 per cent sulfides. Owing to the low grade of ore developed in the mine, extreme care has had to be exercised throughout the entire mining and milling operation in order that an operating profit might be obtained. The management, however, has been able to keep costs down, with the result that at present the outlook for the property is considerably brighter than it has been in the past. This is partly due to the fact that it is now known how to mine and treat

Jan 1, 1935

By Charles Mitke

EXCLUDING top-slicing, and sublevel caving, large production caving methods may be divided into two general classes, the branch raise, or undercut caving method, and the combined shrinkage and caving method, each of which has a number of variations, the result of continual efforts towards obtaining lower costs and better extraction, by the introduction and substitution of minor improvements and modifications. EARLY CAVING METHODS Present caving methods are the cumulative result of developments covering a period of many years, with the most rapid growth during the past 15 years. They originated, presumably, from early English stoping methods, and, as far as is generally known, were first introduced in the Michigan iron district. They have had their greatest expansion and application in the large low-grade porphyry coppers. In their present form, they are probably a development and combination of sublevel caving and shrinkage (back-stoping on ore) with gravity handling of broken material. Sublevel caving, as practiced in the Michigan district today, is a combination of drift, or crosscut, mining, with top-slicing, and caving, supplemented by later refinements in the shape of mechanized handling of broken ore. A height of anywhere from 16 to 20 ft. is generally taken, and the ore is drilled and blasted along the drift or crosscut for half this height (say 8 to 10 ft.), after which the upper 8 to 10 ft. caves and breaks of its own weight, with comparatively little assistance from drilling. This

Jan 1, 1928

By Wasyl Kunda

High grade jig and low grade flotation concentrates used in the following experiments, are produced from silver ore at the mine. The study was carried out to recover the silver and other metals from these concentrates by hydrometallurgical methods. The concentrates were subjected to two stage oxida¬tion leaches in a HNO3-H2SO4 medium. The dissolved metals were recovered by selective precipitation of: (a) silver chloride, (b) iron-arsenic-bismuth residue, (c) copper sulphide, (d) cobalt-nickel sulphide. The effluent solution contained only ammonium sulphate and ammonium nitrate. The silver chloride was further processed to the high purity silver powder by the AgCl ? Ag2S ? Ag2SO4 ? Ag° route. The recovery of silver from the concentrates was over 98% and other metals from 95 to 99%.

Jan 1, 1984

By Sylvan Cromer

The need for a clear understanding of the physical nature of the flow of gas-liquid mixtures in vertical pipes is ever becoming more apparent. This type of flow is encountered when gas and oil are produced from a well; when water is removed from gas wells with siphon lines and when liquids are elevated by means of air or gas lift. Although a number of investigator1-7 have published data on the flow of gas-liquid mixtures, in only a few cases has the experimental setup been devised to permit visual study. In the fields of heat transmission, such as the boiling of liquids and the study of the critical phenomena of the hydrocarbons, researchers have been able to throw additional light on heretofore unexplainable happenings through actual observation in glass apparatus. This investigation was therefore undertaken in order to obtain qualitative as well as quantitative results for air-water flow. Experimental Apparatus and Procedure The flow column used in these tests was made of standard 2-in. pipe and was approximately 98 ft. in height. Pyrex observation sections 2 ft. long having the same internal diameter as the wrought-iron pipe were placed at 14-ft. intervals in the column. The bottom of the tube was cut off square and terminated in the mixing chamber. No perforated nipple or footpiece of any kind was used. To the top of the column was fastened a semicircular return bend having a 4-ft. radius. The flow column was supported by a standard cable-tool drilling derrick (Fig. 1) into which were built observation platforms at each Pyrex section.

Jan 1, 1940