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By W. E. Brigham, P. W. Reed, J. N. Dew

By AIME AIME

APOCRYPHAL, no doubt, but widely entertained is the proposition that top-flight mining geologists never agree with each other on anything. Being rugged individualists, they frequently seem intolerant of opinions that conflict with their own. However, one may suspect that controversy is often more apparent than real. For example, at last summer's meeting of the American Mining Congress, Ira B. Joralemon and Reno H. Sales, discussing "Mining Geology, Today and Tomorrow," seemed to be in serious disagreement over various phases of the subject; but much of this arises from the different angles of approach of the two distinguished and successful ore finders.

Jan 1, 1941

By A. A. Collins

When we speak of high copper on a lead blast furnace we think in terms of 4 to 5 pct, or. any lead charge carrying over 1 pct. Any copper on charge will produce its corresponding troubles such as lead well, extra slag losses, drossing problems, and the working up of the dross. This is indeed a very interesting subject and one that used to give the old-time lead metallurgists such as Eiler, Hahn and lles many worries, not so much in the actual operation of the hlast furnace but in the working up of the copper. When the American nletallurgists commenced with the American rectangular-shaped lead blast furnace in the 1870's and got away from the reverberatories such as were in use in Germany and other parts of the world, they went to greater tonnages, as 80 to 100 tons per day in comparison to the 20 to 30 tons per day in the other processes. With the greater tonnages along with insuficient settling capacity, the silver losses in some cases were increased. Hence the lead-fall was low, for there were no leady concentrates in those days to assist the metallurgist to gain lead or an absorber for the precious metals; and in some cases copper sulphides were added intentionally to the charge to produce a copper matte to lessen the silver losses through the dump slag. The operators in those days thought that where some copper was always present in the lead ores the copper should not enter into the reduced lead and alloy with it. This, by the way, is just the reverse of our present-day practice, when we try to put all of the copper into the blast furnace lead and to remove the same through the drossing kettles. Therefore the furnace was operated to produce a certain amount of matte or artificial sulphides, since, due to the great affinity of copper for sulphur, any copper present would enter the matte almost completely. Thus, the lead bullion produced was practically free from copper. The products of the furnace were metallic lead or lead bullion, containing 05 to 95 pct of the lead and about 96 pct of the silver which were in the ore—a lead-copper-iron matte which contained nearly all the copper in the ore and the slag, the waste product. In the United States, up through the year 1092, we find the small furnace 100 X 32 1/2 in. with 12 tuyeres, some 6 on each side, plagued with a small amount of poorly roasted sulphides— either from heap or hand roasters that produced matte. This matte was roasted and if poor in copper was returned for the ore smelting. Otherwise it was smelted either alone or with additions of rich slags or argentiferous copper ores, the products being lead and a highly cupriferous matte, the latter being subsequently worked up for its copper. The lead metallurgists kept trying and improving on furnace and roasting equipment designs until we find blalvin W. Iles constructing at the old Globe Plant at Denver what came to be the modern furnace. That is, in 1900 he built a furnace of 42 in. width by 140 in. at the tuyeres with a 10 in. bosh and a 16-ft ore column. This type has been more or less standard to the present time, though modified in width and length to meet the demand for large tonnages and improvements in structural details. In 1905 at Cananea, Mexico, Dwight and Lloyd developed the present down-draft sinter machine that has meant so much in producing a well-processed material for the lead blast furnace. In 1912 Guy C. Riddell came forth with double roasting at the East Helena Plant of the American Smelting and Refining Co., which removed the "zinc mush plague." Incidentally, with the introduction of double roasting, which most lead plants were forced into after 1924, when lead flotation came into its own, less matte or no matte was produced. When this stage arrived, the copper was forced into the dross and the casting of lead at the blast furnace lead-wells was stopped. In plants with a fair copper carry 1 pct or better on the blast furnace charge, the lead wells became inoperative once the production of matte stopped. The copper drosses clogged the lead wells and even with bombing, either water or dynamite, the operators could not keep them open. Thus, the lead wells were abandoned in some plants, such as at the El Paso and Chihuahua smelters of the American Smelting and Refinillg Co., and all lead taken out through the first settlers. The elimination of sulphur, espccially sulphide sulphur, from the blast furnace charge and the nonproductiori of matte resulted in a great saving of tinie, energy and equipment in the recirculation of the copper, With the copper content in the dross and dross-fall ranging in quantities from a few percent up to 60 pct, such as at El Paso, a drossing problem was created. As the old-time operators hated dross and buried the same in the shipping bullion, the modern metallurgists from 1925 on decided that with increasing dross-falls they would have to adopt the lead refiner's ideas of drossing kettles with subsequent treatment of the lead with a sulphur addition to have the shipping lead of 0.01

Jan 1, 1950

By GEO H. DEIKE

NOT much activity has been evident during the past year in the establishment of co-operative scholarships but the interest among the coal-mining companies is more pronounced than ever. This is apparent from the replies received to a letter sent out by the Committee on the Promotion of Student Interest in Coal Mining to over 120 coalmine operating officials. With that letter was forwarded a bulletin issued by the school of mineral industries of The Pennsylvania State College entitled ?Industrial Scholarships ? a Partnership of Industry and Education.? In that circular was outlined the need for trained men in the war and postwar world, and particularly as such demands pertain to the growth of the mineral industries.

Jan 1, 1943

By R. Chanchani

It was reported earlier that francolite and dolomite from south Florida deposits cannot be selectively floated using conventional conditioning with sodium oleate as the collector. However, dolomite could be separated from francolite if the minerals were first conditioned at pH 10 followed by reconditioning at a lower pH. An optimum separation was achieved after reconditioning at a pH below 4.5. Reconditioning pH and collector concentration were determined to exert a major influence on the selectivity. Flotation, adsorption, and transmission infrared spectroscopic results are presented to elucidate the mechanisms underlying the observed selectivity.

Jan 1, 1986

By KENNETH W. GREENAWALT, William Greenawalt

THE patent system, through which an inventor is given exclusive right to his invention for a limited period as a reward for his industry and in reimbursement of his expenditures, originated in England in the famous "Statute of Monopolies," enacted in 1623. The first patent granted in America was to Samuel Winslow, in Massachusetts, in 1641. The basis of the patent system of the United States is a provision in the Constitution giving Congress the power to secure to inventors for a limited time the exclusive use of their discoveries. The first legislative enactment was the law of 1790, which was placed on the statute book after Washington had addressed Congress in its favor. Under this law, the Secretary of State, the Secretary of War, and the Attorney General constituted the board for the examination of patent applications and the granting of patents. The first Secretary of State, Thomas Jefferson, became the first administrator of the patent sys- tem in this country. He personally examined every application filed during his term of office.

Jan 1, 1930

By Olin M. Hart

Uranium ores occur in the Lower Cretaceous Inyan Kara group of heterogeneously stratified fluvial and fluvial-marine sandstones in the Black Hills of western South Dakota and northeastern Wyoming. There are three principal mining districts, each in the ancestral and present drainage area of a major river partially responsible for stripping the region to its present topographic form. Primary minerals in the deposits are coffinite and uraninite with minor amounts of paramontroseite and haggite. The ore minerals coat sand grains and fill interstices of complexly cross-stratified sandstone along solution fronts similar to "roll" type deposits of the other districts. Minerals of oxidized deposits are typically carnotite and tyuyamunite with different proportions of secondary vanadium accessory minerals. Ground water was the transporting medium and deposition of primary uranium and vanadium minerals occurred in reducing environments produced and controlled by physio-chemical characteristics of the sedimentary rocks.

Jan 1, 1968

Jan 1, 1883

By AIME AIME

TRADITIONALLY, the Annual New York Meetings of the A.I.M.E. cover four days, but the program is growing on each end as well as in the middle, and this year it lasted from 3 p. m., Sunday, Feb. 16, when the Education Division got under way, to 8:40 p. m., Friday the 21st, when a trainload of electrical inspectors, pro tern, got back fro111 the General Electric plant at Schenectady. The meeting has ceased to be a mere three- ring circus: on Wednesday afternoon eight sessions were being held simultaneously in the Engineering Societies Building, if one includes the Woman's Auxiliary, and according to frequent testimony one should include the W. A. as one of the most important units in Institute affairs.

Jan 1, 1936

By W. S. Morris

PETROLEUM'S importance in World War II can perhaps be better realized by the recitation of a few facts and figures: Gasoline needs in this war are already eighty times greater than in the last war. It takes nearly three pounds of gasoline to deliver one pound of bombs, filled with petroleum explosives, on an enemy objective. Every American soldier overseas requires an average of more than fifty gallons of petroleum products per week, with the oil used by Navy and supply ships and America's Allies boosting the consumption of oil per soldier to an even higher figure. Every oil well in the United States now must produce each day an average of four barrels of oil for war and combat jobs. More than fifty million gallons of gasoline, fuel oils, lubricants, and other petroleum products are now going directly to the fighting forces every day.

Jan 1, 1945

By H. J. Ramey

The wellbore acts as a storage tank during drawdown and build-up testing and causes the sand-face flow rate to approach the constant surface flow rate as a function of time. This effect is compounded if non-Darcy flow (turbulent flow) exists near a gas wellbore. Non-Darcy flow can be interpreted as a flow-rate dependent skin effect. A method for determining the non-Darcy flow constant using this concept and the usual skin effect equation is described. Field tests of this method have identified several cases where non-Darcy flow was severe enough that gas wells in a fractured region appeared to be moderately damaged. The combination of wellbore storage and non-Darcy flow can result in erroneous estimates of formation flow capacity for short-time gas well tests. Fortunately, the presence of the wellbore storage eflect permits a new analysis which can provide a reasonable estimate of formation flow capacity and the non-Darcy flow constant from a single short-time test. The basis of the Gladfelter, Tracy and Wilsey correction for wellbore storage in pressure build-up was investigated. Results led to extension of the method to drawdown testing. If non-Darcy flow is not important, the method can be used to correct short-time gas well drawdown or build-up data. A method for estimation of the duration of wellbore storage effects was developed. INTRODUCTION In 1953, van Everdingen and Hurst generalized results published in their previous paper3 concerning wellbore storage effects to include a "skin effect", or a region of altered permeability adjacent to the wellbore. Later, Gladfelter. Tracy and Wilsey4 presented a method for correcting observed oilwell pressure build-up data for wellbore storage in the presence of a skin effect. The method depended upon measuring the change in the fluid storage in the wellbore by measuring the rise in liquid level. To the author's knowledge, application of the Gladfelter, Tracy and Wilsey storage correction to gas-well build-up has not been discussed in the literature. It is, however, a rather obvious application. Gas storage in the wellbore is a conlpressibility effect and can be estimated easily from the measured wellbore pressure as a function of time. Several approaches to the wellbore storage problem have been suggested. As summarized by Matthews, it is possible to minimize annulus storage volume by using a packer, and to obtain a near sand-face shut-in by use of down-hole tubing plug devices. Matthews and Perrine have suggested criteiia for determining the time when storage effects become negligible. In 1962, Swift and Kiel' presented a method for determination of the effect of non-Darcy flow (often called turbulent flow) upon gas-well behavior. This paper provided a theoretical basis for peculiar gas-well behavior described previously by Smith. Recently, Carter, Miller and Riley observed disagreement among flow capacity k,,h data determined from gas-well drawdown tests conducted at different flow rates for short periods of time (less than six hours flowing time). In the original preprint of their paper, Carter et al. proposed that the discrepancy in flow capacity was possibly a result of wellbore storage effects. Results of an analytical study of unloading of the wellbore and non-Darcy flow were recorded by carter.14 In the final text of their paper, Carter et al.!' stated that they no longer believed wellbore storage was the reason for discrepancy in their kgh estimates. In view of the preceding, this study was performed to establish the importance of non-Darcy flow and well-bore storage for gas-well testing. In the course of the study. a reinspection of the previous work by van Everdingen' and Hurst' was made, and the basis for the Gladfelter, Tracy and Wilsey' wellbore storage correction was investigated and extended to flow testing. WELLBORE STORAGE THEORY As has been shown by Aronofsky and Jenkins,11-12 Matthews," and others, flow of gas can often be approximated by an equivalent liquid flow system. The following developnlent will use liquid flow nomenclature to simplify the presentation. Application to gas-well cases will be illustrated later. First, we will use the van Everdingen-HursP treatment of wellbore storage in transient flow to establish (1) the duration of wellbore storage effects, and (2) a method to correct flow data for wellbore storage. DURATION OF WELLHORE STORAGE EFFECTS When an oil well is opened to flow. the bottom-hole pressure drops and causes a resulting drop in the liquid level in the annulus. If V. represents the annular volume in cu ft/ft of depth, and p represents the average density of the fluid in the wellbore, the volume of fluid at reservoir conditions produced from the annulus per unit bottom-hole pressure drop is approximately: res bbl-- (V, cu ft/ft) (144 sqin./sq ft) psi -(5.615 cu ft/bbl)(pIb/cuft) ........(I)

Jan 1, 1966

By M. E. Fine, A. A. Henderson

Investigation of the tensile properties of silver based aluminum alloy crystals was undertaken because it appeared attractive for studying strengthening effects due to Suzuki locking with minimum complication. Yield drops were observed in all alloy crystals (1, 2. 3. 4, and 6 at. pct Al) after strain aging at room temperature. No yield drops were found in similarly grown and tested silver crystals. The yield effects are attributed to Suzuki locking but the major portion of the solid solution strengthening to other mechanisms. INVESTIGATION of the tensile properties of single crystds of silver alloyed with aluminum was undertaken because it appeared to be a system in which segregation at stacking faults associated with partial dislocations1 would be the dominant factor in anchoring dislocations. First, silver and aluminum have closely similar atomic sizes and thus solute atom locking of a dislocation due to elastic interactions should be unimportant. Second, while both X-ray2 and thermodynamic3 investigations show short-range ordering in silver-based aluminum alloys, the degree of local order is quite small (X-ray measurements give v = EAB - 1/2(EAA + EBB) = - 0.025 ev and thermodynamic measurements give v r -0.007 ev) and should not be important in strengthening dilute alloys. Third, the stacking fault energy of silver is probably low (as indicated by the profusity of annealing twins) and is very likely diminished further and quite rapidly by aluminum additions since the A1-Ag phase diagram shows a stable hexagonal phase at only 25 at. pct Al. Also, a careful investigation in this laboratory4 has shown that the ratio of twin to normal grain boundaries in recrystallized alloys increases with aluminum content. Thus, with minimum complication from other factors, Ag-A1 alloys seem attractive for studying strengthening effects due to segregation at stacking faults of extended dislocations. EXPERIMENTAL METHOD Single crystals measuring 250 by 5 by 1.5 mm of pure Ag (99.99 pct) and Ag-A1 alloys (A1 of 99.999 pct purity) of nominal compositions* 1, 2, 3, 4, and 6 at. pct were grown in high-purity graphite molds from the melt under a dynamic vacuum (1 x l0-5 mm Hg). The technique consisted of moving a furnace having a hot zone (which melted about 0.5 cm of alloy) over a horizontal, evacuated quartz tube con- taining the mold and alloy at a rate of 3/8 in. per hr. Chemical analysis showed roughly the first inch of the crystal to be solute poor, the last inch solute rich; and the center section uniform in composition within the sensitivity of the analytical method (± 0.2 at. pct Al). The center section of the crystal was cut into five specimens. Gage lengths of reduced cross section, measuring from 1.5 to 2 cm in length, were mechanically introduced by means of jeweler&apos;s files and fine abrasive cloth with the crystal firmly held in polished steel guides. One-third of the cross section was then removed by etching and electro-polishing, the crystals were all subsequently annealed for several days at 850°C in a dynamic vacuum (<1 x 10-5 mm Hg) and furnace cooled to 200°C. The crystal orientations were determined using the usual back-reflection Laue technique. The Laue spots were sharp and of the same size as the incident beam. However, microscopic examination showed the crystals to contain substructures with subgrains of the order of a micron in diameter. The details of this substructure are presently under investigation. Tensile testing was done with a table model Instron using a cross-head speed of 0.002 in. per min. For testing at various temperatures the following media were used: 1) 415oK, hot ethylene glycol; 2) 296ºK, air, acetone, water; 3) 273ºK, ice water; 4) 258ºK, ethylene glycol "ice" in ethylene glycol; 5) 200°K, dry ice in acetone; 6) 77ºK, liquid nitrogen. EXPERIMENTAL RESULTS A) Yield Behavior—A portion of an interrupted stress-strain curve for a 6 at. pct A1 crystal of the indicated orientation tested at room temperature is shown in Fig. 1. Initially, at (a), there is a small, gradual yield drop of about 10 mg per sq mm2. However, on stopping the test, and aging for a few minutes at (b), a sharp yield drop is found. Aging for longer times at (c) and (dl results in larger yield drops (and larger AT&apos;S). At, defined in Fig. 1, is usually larger than the yield drop by about 20 pct; however, this increase in the lower yield is transient since extrapolations of the flow stress curves join as may be seen from Fig. 1. (Both Laue and low-angle scattering photographs revealed no evidence of precipitation in a strain-aged 6 at. pct A1 crystal.)

Jan 1, 1962

By G. Cartaud, F. Osmond

WE have already devoted two previous memoirs to this question. In the first we collated and discussed the existing literature on the subject; in the second, we described the crystalline forms obtained by the reduction, at different temperatures, of ferrous chloride by hydrogen or by zinc-vapor. The conclusion from these researches was that the three allotropic states of iron-a, stable below A2; 19, stable between A2 and A3; and 7, stable above A3-all crystallize in the cubic system. The differences observed were such as are customarily encountered in the crystallographic records of many minerals of which allotropic varieties or isomerides are not known, but did not conform to the ordinary definition of polymorphism. It is, however, improbable that allotropic transformations, which are placed beyond doubt by a series of positive facts, do not involve some changes in the intimate structure. As a matter of fact, the crystals we did obtain were too small to allow of a precise examination, and this might introduce an element of uncertainty in the firm establishment of our conclusions. Professor H. Le Chatelier was even led to think from some of our results that iron could very well be a rhombohedron simulating a cube, and not a true cube, and it will be remembered that the crystalline form of bismuth was for a long time incorrectly regarded as cubic. Allotropy does not, however, necessarily involve such a deduction. Without departing from the cubic system at all, a whole

Nov 1, 1906

By P. L. De Bruyn, R. J. Charles

THE transfer of kinetic energy of translation into other forms of energy by impact is a fundamental process in most crushing and grinding operations. During and after the impact process the original source energy may be accounted for in any of the following possible forms: 1) Kinetic energy of translation of both the impacted and impacting objects. 2) Kinetic energy of vibration of the components of the impact system. 3) Potential energy as strain energy of the components of the system or in the form of residual stresses. 4) Heat generated by internal friction during plastic deformation or during damping of elastic waves. 5) New surface energy of fractured materials. At any instant during the impact process only the strain energy of the components of the system can contribute directly to the brittle fracture process. If fracture is the desired result, as in comminution, it would seem advantageous to choose or arrange the conditions of impact so that a maximum amount of the original kinetic energy could be converted to strain energy at some moment during a single impact. The present work deals with determination of these desirable conditions for a simple case of impact and application of the principles involved to general cases of impact. Experimental Method: Longitudinal impact of a rod with a fixed end was chosen as the impact system for investigation. The rod was mounted horizontally and the fixed end was formed by butting one end of the rod against a rigidly mounted steel anvil. The rod, of pyrex glass, was 10 in. long by 1 in. diam with both ends rounded to a 6 in. radius. The rounded ends permitted reproducible impacts on the free end of the rod and assured a symmetrical fixed end. Pyrex was selected as the rod material because of the marked elastic properties of such glass and the similarity of fracture between pyrex and many materials encountered in crushing and grinding operations. The frequency of natural longitudinal oscillation of the rod was 10 kc, and thus simple electronic equipment could be used for observation of strain changes occurring in the rod at this frequency. As shown in Fig. 1, impacts on the free end of the rod were obtained either by a pendulum device or by a spring-loaded gun. Relatively heavy hammers (100 to 600 g) of mild steel were used in the pendu- lum impacts, while fairly light projectiles (20 to 80 g) were fired from the spring-loaded gun. One of the main objects of the experimental work was to obtain the strain-time history of the rod as a function of the mass and kinetic energy of the impacting hammers. For this purpose a technique involving wire resistance strain gages and a recording oscilloscope was employed. Five gages were applied at equidistant sections along the rod, and by means of a switching arrangement the strain-time history at any section, and for any impact, could be obtained in the form of an oscillograph with a time base. The equation relating strain and voltage change across a strain gage through which a constant current is flowing is as follows: e = ?v/iRF [1] ? = strain, ?v = voltage change, i = gage current, R = gage resistance, and F = gage factor (from manufacturer&apos;s data — SRA type, Baldwin Lima Corp.). With the above equation an oscillograph depicting voltage change vs time on a single trace can be converted directly to a strain-time diagram if a calibration of the vertical response on the oscilloscope screen for specific voltage inputs is available. In the present case the calibration was obtained by photographing precisely known audio frequency voltages on the same oscillograph as that on which a voltage-time trace from a strain gage had been made. Synchronization of the beginning of the single trace with the beginning of the impact was accomplished by permitting contact of the impacting objects to close an electrical circuit from which a voltage pulse, sufficient to initiate the trace, was obtained. The struck end of the rod was lightly silvered for purposes of electrical conduction so that it would form one of the electrical contacts. Markers every 100 micro-seconds on the traces served for a time base calibration. Determinations of the kinetic energies of translation prior to impact were made in the case of the pendulum hammers by measuring the height of fall of the hammer and in the case of the projectiles by measuring the exit velocity from the gun barrel by means of an electrical circuit employing light sources, slits, and phototubes.&apos; During the experimental work it became evident that the time of contact between the impacting object and the rod was an important variable in the impact process. Measurements of the times of contact were made, therefore, for every impact for which a strain-time record was obtained. The time of contact was determined by permitting the impacting components, when in contact, to act as a closed switch and discharge a condenser at relatively constant voltage. The discharge was observed and photographed with a time base on the oscilloscope screen.

Jan 1, 1957

By E. W. Felegy

THE need for improved mine communication to increase efficiency and to insure greater safety has long been recognized. General and unrestricted communication between all points underground, and between the surface and all points underground, is probably the least advanced phase of the mining industry. An ideal system of mine communication must require no fixed wire installations. The equipment must be small, lightweight, and readily portable, and the power requirements low. A system that can be used not only under normal circumstances but also in an emergency, when the continuity of wires, tracks, and pipelines may be disrupted, must function independently of any aid furnished by standard installations. Radio communication offers possibilities of meeting all the requirements necessary for an ideal communication system in underground mines. Transmission of signals must be achieved through one or both of two mediums, through the air in mine openings or through the strata. The results or lack of results obtained by early investigators showed conclusively that radio communication by space transmission cannot be accomplished effectively beyond line-of-sight distances in underground passageways. A radio system underground therefore must depend solely upon transmission through soil and strata. The application of radio to underground mine communication was investigated by many individuals and agencies at different times in the last several decades, but little success was achieved before World war 11.2-0, The results of experiments during the war, and further knowledge gained in experiments with vastly improved communication methods and equipment after the war provided the background for additional research in radio communication in underground mines. During 1950 to 1.952 the University of Minnesota sponsored an investigation to determine the possibility of developing: a system of radio communication universally applicable in underground metal mines in the Lake Superior district. The possibility of using radio equipment to determine the imminence of rock bursts in deep copper mines in that district also was investigated. The investigation supplemented previous and concurrent emergency mine communication studies of the U. S. Bureau of Mines. Testing equipment and laboratory facilities maintained by the Bureau of Mines at Duluth, Minnesota, were used in the research program, which was conducted as a mining engineering graduate research problem by the present writer under the direction of T. L. Joseph and E. P. Pfleider. The radio units used in the research program were designed and built to specification solely to conduct tests of radio communication in mines. Two identical units were used in all tests. Each unit contained a transmitter section, a receiver section, and a power-supply section, mounted on a single chassis. The entire unit was enclosed in a single 10x12x18-in. metal case provided with a leather-strap handle for carrying purposes. The front of the case was hinged to open upward and provide easy access to the single control panel on which all controls were mounted. Storage batteries supplied the operating power for all tests. Standard 6-v automobile batteries were utilized to provide adequate capacity to conduct tests for a full day without exhausting the battery. A frequency range from 30 to 200 kc was covered in eight pre-fixed steps on each unit. The carrier frequencies were crystal-controlled and amplitude-modulated. The receiver employed an essentially standard superheterodyne circuit and was sufficiently sensitive to detect signal strengths of 5 micro v. A heterodyne circuit was employed in the transmitter to obtain the low-carrier frequencies used in the units. Power output of the transmitter, usually less than 2 w, rarely exceeded 3 w in any test. Tests were conducted in mines on the Vermillion iron range in Minnesota, the Gogebic iron range in Wisconsin, the Menominee and Marquette iron ranges in Michigan, and a copper mine in the upper Michigan peninsula. All tests were conducted when the mines were operating normally, and usual mining, maintenance, and transportation activities were in progress, so that any interference caused by normal production activities could be evaluated during the tests. Tests were made between different points underground in each mine, and between underground and surface points at some mines. Test readings obtained at any one mine were calibrated in the laboratory before another series of tests were begun at the next mine. The transmitter and receiver were separated by one or more levels in each test, and generally there was no other means of communication between test points. Two 100-ft lengths of rubber-covered wire were used for antenna wires on each unit in both transmission and reception. The ends of the wires were connected to ground points in one of several methods, depending upon physical conditions at each test site. The wires were clipped to metal rods about 200 ft apart in the back, side, or bottom of the mine opening where the character of the rock permitted driving rods. Both wires were clipped to points about

Jan 1, 1954

By W. Philippoff

ALTHOUGH Gaudin1 and more recently Sutherland2 have calculated the probability of collision of a falling mineral particle with a rising bubble, there is no published information concerning the details of the mechanism of attachment of a collector-coated particle to a bubble. During the past year the writer has developed a theory for the mechanism of attachment, which has been substantiated experimentally.&apos; Funds for the investigation and for some of the equipment used have been supplied by the Mines Experiment Station of the University of Minnesota. Motion picture studies of the phenomena involved in the collision between mineral particles and bubbles, such as those of Spedden and Hannan,3 show that the contact can be completed within 0.3 millisec. Formulas developed for rigid bodies have hitherto been used&apos; for the calculation of the motion of bubble and particle, but it is obvious that a bubble cannot be regarded as a rigid body. On the contrary, Spedden and Hannan&apos;s pictures show a great degree of deformation during the collision. The time of attachment was calculated as the time the particle drifted past the bubble. Time of Collision The theory presented in this paper enables calculation of the time of collision; using the concept that the bubble, or more generally, a liquid-air interface, acts as an elastic body. The elasticity, defined as the restoring force on a mechanical deformation, is caused by, the surface tension and is the result of the principle of the minimum of free surface energy. It is well known that an elasticity together with a mass determines a frequency of vibration. The vibrations of jets and drops caused by the elasticity of the interface are known to comply exactly with the classical theory of capillarity.5 However, the vibrations of isolated bubbles, as distinct from foams, have not been investigated previously. The following equation, presented elsewhere,&apos; has been deduced for these frequencies: [3fB = 9.20•&apos;./V•Vn- (n-1) • (n+2) /8[1]] in which fB is the frequency of a harmonic of the bubble in cycles per second, V the volume of the bubble in cc, n a number determining the order of the harmonic, and n = 2 the basic vibration. The first (basic) harmonic describes a change of the spherical bubble to an ellipsoidal bubble. The higher harmonics are more complicated, for the circumference of the bubble is divided approximately into as many parts&apos; as the order of the harmonic. As an example, Spedden and Hannan&apos;s published motion picture of, a vibrating bubble corresponds to the sixth harmonic. Eq 1 shows that only the first and third harmonics are simple multiples (1 and 3), all the others being irrational fractions of the basic frequency. This means that the shape of the vibration can change with time and is in general unsymmetric in respect to the time axis. Such conditions prevail when there is a distributed elasticity or mass, as in the case of vibrating membranes or rods. The constant 9.20 is valid for water at room temperature, but a general solution involving the physical constants of the liquid has not been found. The case of the floating particle is much easier to treat I than that of the bubble. It can be assumed that the elasticity is caused exclusively by the interface and that the mass is concentrated in the particle together with some adhering water. The following expression for the frequency of a system, of one degree of freedom can be applied: [1E/m[2] fP = 27] Here f, is the frequency of the particle vibration in cycles per second, E the elasticity in dynes per cm, and m the mass in grams. The classical theory of impact phenomena gives the time of collision during the striking of a spring (in this case the surface of the bubble) by a mass, as: [t~ = 2/f = 7r\/m/E[3]] It is now possible to develop an expression for the elasticity of a floating cylindrical particle. The force equilibrium of a cylinder floating end on at the air-liquid interface is given by the well-known equation (Poisson&apos; 1831) [aP = 4 D2.pL•g•h +7rD•y sin a[4]] which accounts for the buoyancy and the action of the surface tension where P is the force acting on the particle in dynes (weight-buoyancy), D the diameter of the cylinder in cm, pL the density of the liquid in grams per cc, g the acceleration of gravity = 981 cm per sec2, h the depression of the cylinder below the surface of-the liquid in cm, y the surface tension in dynes per cm and a the supporting angle&apos; or the one required to insure equilibrium, a being smaller than the contact angle ?. Although demonstrated by Poisson, it has not

Jan 1, 1952

By A. N. Rogers

Jan 1, 1883

By M. S. Azun

I do not at all agree with the basic points of the author&apos;s conclusion. The use of lognormal or normal model to respond to the attribute distribution function should be carefully questioned. If fitting a distribution function of regionalized variables is the main purpose, one may employ one of certain well-known families of distributions, such as Tukey&apos;s lambda functions. For instance, the distribution function of gold assay values studied by Krige (Krige, 1978) may fit the lognormal model well, but one should not exclude that the basic idea of using the distribution function of observed data is to have insight of the physical mechanism that gives rise to the regionalized variables. In Applied Geostatistics, there are many examples considering only lognormal or normal model for the distribution function of geostatistical data even if the observed distribution function has more than one mode. Of course, using lognormal or normal model always brings easy computation for the statistical properties of attribute under investigation. Still, I object to adopting any of those models without having any "statistical inference." As seen from the author&apos;s paper, lognormal and normal model produce the same average grade (0.746% copper) and almost the same sample variance. Therefore, which model explains the probabilistic behavior of ore deposit is always an important question that should be replied by the geostatistician using not the common sense but the statistical and probabilistic methods. For kriging procedures, such as linear kriging, one should describe either second order stationary properties or bivariate properties of regionalized variables. Second order properties, such as correlogram function or semivariogram function, are the inputs of the so-called kriging equations. Selecting one of any useable models for the observed second order properties, such as spherical model, is not easy since the models are not based on the correlations structure of the regionalized variables. How those models being used in Applied Geostatistics can be distinguished is another important problem. One may develop many fitting models to respond to the observed second order properties of regionalized variables. However, I suggest that the model should be based on the probabilistic behavior of geologic process. The author used spherical model for copper, wolfram, and silver grades from isotropic sector (Fig. 2, 4, 3b) and exponential model for silver grades obtained along raises in isotropic sector (Fig. 3a). It seems that those semivariograms given in Fig. 3b for isotropic sector and Fig. 4 may be described by the random model implying that regionalized variables do belong to renewal process (Azun, 1983). If I knew the total number of data points used in estimation, may prove that my conclusion is correct. Recalling the test for the first order sample correlogram value, the test procedure is introduced such that the independence is rejected if [Ir(1) I > Za/2 N1/2] where Za/2 is the a/2 percentile of standard normal random variable and N is the total number of samples used in estimation (Azun, 1983). For the other observed semivariogram functions I suggest the author might try to use the so-called "Markovian model" describing not only the correlation structure of regionalized variables, but also the physical mechanism that produces the regionalized variables. The Markovian model for correlogram function is, [p (h) = T 1ih , h>1 ,] The Markovian model for the other second order properties of ReV are also derived. [T veß], in the above equation, show, for example, structural change and mineralizational variation in a considered deposit, respectively (Azun, 1983). In selecting any model, it is not easy to search for the "best" response to the observed second order properties of ReV&apos;s. The Markovian model, based on a theoretical understanding of underlying mechanism, gives more information about the occurrence of regionalized variables and respond to all properties. Random model and the so-called hole effect structure can be easily defined as a special form of the Markovian model (Azun, 1983). An estimation of any second order properties of regionalized variables may be computed through (N-1) lag. However, the dependency between the regionalized variables may be deemed to have "died out" after the so-called stationarity width (range). In practice, the estimation is carried out through 25% of the total number samples available. Therefore, the large fluctuations around the zero level and variance for correlogram or covariogram function and semivariogram function, respectively, cannot be observed. Since the number of pairs involved in the estimation of higher second order properties is small, the estimation variance at those lags is large. There is no need to show higher order estimated second order properties. After using one of any kriging procedure for block estimation, the distribution function of average grades has the same mean as the drilling sample grades but

Jan 1, 1986

By J. T. Norton, N. J. Grant, A. R. Chaudhuri

MOST of the recent work to establish the mech-anism of creep in metals at high temperatures has utilized aluminum as the experimental material. It was thought desirable to initiate an investigation of a hexagonal close-packed metal, because of the relatively simple slip system, and compare the observed deformation characteristics with those that have been observed for the face-centerd cubic metals. High-purity magnesium was chosen for this purpose, first, because its strength and other mechanical properties are similar to those of aluminum in the same temperature range, and second, because the existing equipment was ideally suited to observe magnesium during creep. It is proposed in this paper to present a pictorial and qualitative account of the changes that high-purity magnesium undergoes during creep at 500°F. The characteristics of deformation of aluminum described below have been observed by various workers and accounts of these may be obtained from the papers of Chang and Grant.&apos;- These characteristics are: slip, subgrain formation, grain boundary sliding and migration, fold formation, deformation bands, and kink bands. It is well known that in a flat magnesium specimen, slip on the basal plane (0001) in the [1120] direction results in the formation of straight bands on the surface of the specimen. Schmid and co-workers&apos; have shown that this system is operative in the temperature range of -185" to 300°C (-300° to 572°F). They have also shown that a second system, slip on the pyramidal planes {1071} or {1012} in the [1120] direction, is operative at temperatures higher than 225°C (437°F). Between 225° and 300°C (437" to 572°F), therefore, deformation by both these systems is expected. Bakarian and Mathewson5 confirmed the occurrence of pyramidal slip on the {1011} plane and found that it resulted in irregular markings on the surfaces of their specimens. Burke and Hibbard6 obtained evidence of pyramidal slip in single crystals of magnesium deformed at room temperature. Bakarian and Mathewson5 suggested that the irregular appearance of these bands was due to slip on both of the pyramidal planes occurring simultaneously but in the same direction, the close angular relationship between the planes making this process possible. Furthermore, since neither of these planes is close enough to the basal plane, slip on the latter does not exhibit the irregular appearance of slip bands resulting from pyramidal slip. Experimental Procedure High-purity magnesium, supplied by the Dow Chemical Co., was used in these experiments. The analysis was as follows: Al, 0.0002 pct; Mn, 0.0018; Fe, 0.0024; Cu, 0.0002; Sn, 0.001; Ca, 0.01; Ni, 0.0003; Zn, 0.01; Pb, 0.0005; Si, 0.001; and Mg, 99.972. The magnesium was supplied in the form of 1/2 in. diam rods. The specimens had an overall length of 21/4 in., the round ends being threaded to fit the specimen holders. The previously round 3/16 in. diam gage section of the specimen had two parallel flats machined on opposite sides for microscopic observation, yielding a test zone having the dimensions of lx3/16x7/64 in. The specimens were electrolytically polished (without prior mechanical polishing of the machined flats), in a solution composed of 375 ml of ortho-phosphoric acid and 625 ml of ethyl alcohol.&apos; The cathode was a stainless steel sheet bent so that the specimen was completely surrounded. The voltage for successful polishing was 1.5 v at 100 to 300 milli-amp current. Electropolishing for about 45 min sufficed to obtain a good metallographic surface on the specimens after they had been machined. The creep tests were performed under constant load, and two types of equipment were used. In the first, designed by Servi and Grant,V he specimens were beam-loaded, and a furnace could be lowered to surround the specimen. As the microstructural changes could not be observed during the course of the test, the tests had to be interrupted periodically by removing the specimen for microscopic examination. The second unit was a high temperature microscopy furnace designed by Chang and Grant.&apos; The furnace was fitted with an optically flat quartz window having area dimensions 1.25x0.5 in., so that the whole test portion could be viewed through it at magnifications up to x240. The metallurgical microscope had three mutually perpendicular axes of motion, and, in addition, it was possible to measure angular displacements by rotation of the eyepiece. It was thus possible to make precise observations of the specimen during creep, and micrographs could be taken by attaching a camera to the eyepiece of the microscope. The average grain size of the specimens that were tested was about 1 to 3 mm. This grain size could

Jan 1, 1954

By John V. Beall

HEAVY-DENSITY separation processes, a commercial application of the sink-float test used in mineralogical laboratories for the separation of mineral particles by their difference in specific gravity, are the biggest development in mineral dressing since flotation, which was at about the same stage of development thirty years ago. The scope of their application has broadened and, though still in the development stage, they are being accepted in a constantly increasing number of commercial installations. This progress in mineral beneficiation is especially satisfying when we realize that our high-grade ore deposits are fast disappearing and a big factor in determining whether a hole in the ground is being sat upon by a liar or an honest citizen is how economically the ore dressers can concentrate comparatively low-grade ores. As early as the middle of the nineteenth century attempts were made to use aqueous salt solutions in a heavy-liquid separation for cleaning coal. But the original and recovery costs of these liquids were high and further, the fact that they were corrosive, unstable, and toxic added to the difficulty in using them.

Jan 1, 1948