Search Documents

By W. P. Lass

The gold precipitate from the zinc-dust presses in the cyanide plant of the Alaska-Treadwell Gold Mining Co., Treadwell, Alaska, is treated, in the refinery adjoining, by the Tavener or lead-smelting method. About 3 or 4 tons of this precipitate is produced monthly having 'a gold assay value of $40,000 to $60,000 per ton. It was formerly the practice to treat the byproducts from this process, consisting of 2 tons of slag, 300 lb. of matte, 500 1b. of refinery refuse, flue dust, etc., in a 24-in. water-jacketed blast furnace. This practice was discontinued in the summer of 1914 by reason of the difficulty of keeping the lead-well open when treating a high-grade lead product; of preventing the loss of gold in the flue dust; and of avoiding injury to the general health of the refinery operators; a plain single-phase electric furnace was substituted for the blast furnace. The furnace was constructed from an old steel acid drum by cutting off the top and introducing a cable, made from strands of bare copper wire, through the bottom and spreading the strands out fan-shaped on the inside of the drum. Powdered graphite, obtained by grinding up old crucibles, mixed with 10 per cent. cement, was tamped wet into the bottom of the drum, around and completely covering the copper wires. The graphite was carried up to the bottom of the furnace, or lead-well, and acted as the lower electrode. The sides were built up of ordinary firebrick forming a melting chamber 14 in. in diameter by 20 in. high. The upper electrodes, of graphite or carbon, are 3 in. in diameter and 40 in. long, arranged with joints enabling new electrodes to be connected without shutting down or wasting stubs. A screw feed was arranged for raising and lowering the upper electrode. (Figs. 1 and 2.) The cover for the furnace had three openings, one for feeding the charge, one for the escape of gases, and one in the center for the introduction of the electrode. It was later found more practical to enlarge this center opening to 6 in. in diameter, to allow of a central feeding of the charge around the electrode.

Jan 1, 1916

By M. S. Miller, R. H. Mullennex

The growing need for development of thinner, more erratic, or less easily-mined coals in the Appalachian region requires more detailed analysis of conditions and factors controlling or influencing deposition of these seams. The value of depositional modeling in evaluation of such coals has been demonstrated in many recent studies and publications. Such modeling may be applied to allow prediction of factors varying from regional coal occurrence trends to very local areas of seam discontinuities but requires thorough we of all available types of data. Mapping of general depositional energies, as derived from basic geophysical and driller's logs, can be applied to specific prediction of coal occurrence, and projection of particular facies as representative of unique depositional features or conditions may prove more applicable to coal character delineation than mapping of the coal itself. Depositional modeling and trend projection may also serve as a guideline in reserve classification and confidence levels in reserve estimations.

Jan 1, 1983

By P. Barnes

The object of this paper is to make a brief comparison of the outlines of several forms of ports for steel-melting turnaces, in reference chiefly to the proper mixture; of the gas and air, and to the direction in which the flame is thrown down into the interior of the furnace. In the illustrations on the accompanying plate, Fig. 1 shows a form of port designed by M, Pernot, of St Chamond, France. This is used with the dome roof preferred by him fur the revolving bottom that bears his name. From No. 1 has been derived No. 2. This is shown on the plans of Mr. A. L. Holley, and from them three large furnaces have been built and put into operation by the Springfield Iron Company. Fig. 3 shows an outline proposed by Messrs. Richmond & Potts for the Pernot furnace. In this the ports are brought in under an arched roof of nearly the ordinary form, instead of over the top of the roof, as with the dome of M Pernot, Fig. 4 shows a furnace as built by Krupp of Essen, Prussia, for fluid refining, or " washing "-—to use the briefer French term. in this the gas and air come into contact in broad sheets one above the other, Fig. 5 shows the form used by Messrs. Richmond & Potts

Jan 1, 1881

By P. Barnes

THE object of this paper is to make a brief comparison of the out-lines of several forms of ports for steel-melting furnaces, in reference chiefly to the proper mixture of the gas and air, and to the direction in which the flame is thrown down into. the interior of the furnace. In the illustrations on the accompanying plate, Fig. 1 shows a form of port designed by M. Pernot, of St Chamond, France. This is used with the dome roof preferred by him for the revolving bottom that bears his name. From No. I has been derived No. 2. This is shown on the plans of Mr., A. L. Holley, and from them three large furnaces have been built and put into operation by the Springfield Iron Company. Fig. 3 shows an outline proposed by Messrs. Richmond & Potts for the Pernot furnace. In this the ports are brought in under an arched. roof of nearly the ordinary form., instead of over the top of the roof, as with the done of M Pernot, Fig. 4 shows a furnace as built by Krupp of Essen, Prussia, for fluid refining, or “washing” -to use the briefer French term. In this the gas and air come into contact in broad sheets one above the. other. Fig. 5 shows the form used by Messrs, Richmond & Potts

Jan 1, 1881

By C. A. Wert, K. C. Hsieh

Mineral particles in coal have enormous variation in size. Some are large enough to be seen by eye, others can be seen with the optical microscope and still others are so small that they can be resolved only by electron microscopy. We paid particular attention to particles of clays and sulfides less than 1 pm in size. This paper describes typical minerals and reports on the application of the techniques of electron microscopy to coal.

Jan 1, 1984

By James J. Olson, Richard A. Dick

Blasting practices have shown a recent trend toward larger blastholes and larger burdens and spacings, although some operators, after reconsidering the situation have gone back to smaller blasthole sizes. The greater pull-down capabilities of larger drill rigs and the greater bearing strength of large diameter drill bits give penetration rates for large diameter blastholes approaching, and sometimes exceeding, penetration rates for smaller holes. In practically all cases, large diameter holes can be drilled more quickly and cheaply, based on volume of hole, than small diameter holes. The industry's shift to dry blasting agents and slurries, products which perform more dependably and efficiently in larger diameters, gives an additional advantage to larger boreholes.

Jan 3, 1972

By E. E. Thurlow

The Geology Div. of Northern Pacific Railway Co. has adapted to its exploration efforts field procedures for geochemical sampling and semi-quantitative analysis which have been developed through research by the U. S. Geological Survey. The sampling is done in conjunction with reconnaissance geologic mapping on aerial photographs or during field checking of maps which have been prepared largely by photo-geologic interpretation. Stream sediment or soil samples are taken and readily soluble combined heavy metals are extracted with ammonium citrate followed by colorimetric titration with dithizone at the sample site. The effectiveness of this approach has been demonstrated both in positive and negative results, thereby assisting in the elimination of large areas of land from further immediate attention and in providing targets for followup exploration. An occa sional sample is submitted for spectrographic analysis as a check on the possible presence of other elements of economic significance. Field laboratory procedures are also being implemented for determining molybdenum, mercury, and other metals which may be valuable in themselves or useful as pathfinder elements in outlining mineralized areas. A lead-zinc occurrence in Oregon and a copper deposit in Montana were readily detected and outlined by stream sediment and soil sampling and a heavy metal anomaly that lacks obvious interpretation has been found in northwestern Montana. Detailed mapping and additional sampling are followed by other exploration techniques if warranted. Northern Pacific's program of reconnaissance mineral evaluation of company-owned lands and adjoining areas was outlined in a paper presented at the American Mining Congress meeting in Las Vegas four years ago. That report included policies and procedures with respect to mineral development on Railway Co. lands and may be referred to for information on these matters.1 In a sense this paper is a progress report on the use of geochemical prospecting in Northern Pacific's continuing mineral evaluation program. At this time there are positive results but as yet there is no real success story in the form of a minable ore body. GEOCHEMICAL PROSPECTING PROCEDURES The decision to use geochemistry as a reconnaissance exploration tool must be followed by research into sampling and analytical methods and into the interpretation of results. Various analytical methods were tried and evaluated by the Geology Div., including hot and cold acid extraction with and without fusion of the sample, panning and magnetic separation followed by dithizone testing of the magnetite, and cold aqueous extraction of metallic ions followed by indicator tests. Samples were first sent to the laboratory for analysis; later field laboratories were established and now virtually all testing is done at the sample site. It was concluded that, where applicable, the quickest dependable methods for reconnaissance use are the dithizone field tests for readily extractable heavy metals. This involves the simultaneous treatment of a sample, usually of soil or stream sediment, with two immiscible liquids; one a cold aqueous extractant (ammonium citrate) and the other a solution of dithizone in toluene or xylene.2 Dithizone is a colorimetric indicator that reacts quantitatively with copper, lead, zinc, and several other metals to form colored complexes in organic solvents. Results may be expressed in ml of 0.001 pct dithizone that are required to reach the blue end point, or calibration of the test results can be carried out with standard solutions of zinc; conversion factors would then be expressed in ppm, zinc equivalent. Calibration of dithizone solution with zinc standards indicates that 1 ml of 0.001 pct dithizone is equivalent to approximately 0.25 ppm of zinc. An authoritative report on dithizone field tests authored by H. E. Hawkes in the June-July 1963 issue of Economic Geology* states "The appeal of these techniques has been the simplicity and speed of the determinations as compared with more tedious laboratory determinations of trace metals in weathered rocks, soils, or plant materials. This obvious appeal, however, has often been more than matched by misuse of the method in such a manner that the results are

Jan 1, 1964

By Edward W. Parker

THE agreement of September, 1922, between the anthracite operators and the United Mine Workers of America, which followed the 54.5 months strike during the summer of that year, contained the following provision : The parties unite in a recommendation to Congress that legislation be forthwith enacted creating a separate anthracite coal commission with authority to investigate and report promptly on every phase of the industry and the parties hereby ask the President to request the enactment by Congress of the recommended legislation. The continuance of production after Aug. 31, 1923, shall be upon such terms as the parties may agree-upon in the light of the report of the Commission.

Jan 1, 1924

By K. Thirumalai, D. P. Schlick

Longwall Technology has a potential of resulting in safety and productivity improvements of U.S. underground coal mining similar to those experienced by the introduction of continuous miner systems. The study presents a comprehensive national evaluation of longwall technology to assess the potential of longwalls to improve health and safety and coal productivity. The study was conducted by the authors during the spring of 1980 as part of MSHA New Technology Coordination activities and with a view to examine the factors that may limit the acceptance of longwall technology in the U.S. coal mining operations. The study points out areas where adjustments need to be made in MSHA regulations and enforcement to help Longwalls. A two-entry longwall system appears to offer a practical method of improving underground coal productivity and safety. Applying regulations that are primarily designed for room and pillar methods to longwall mining, in some instances, reduces the effectiveness and productivity benefits feasible by new technology application. Controlling dust is the single predominant problem in the design and operation of longwalls in the United States. The results of this study points out a need for a coordinated program between government and industries on dust control technologies for examining acceptable technological options to control dust in longwalls without restraining the production capability of the system.

Jan 1, 1981

A method has been developed to remove calcite from the leaching circuit in the uranium in situ leaching system. The process involves injecting the leachate and a pH control agent tangentially into an inverted cone reactor containing calcite seed catalyst. The leachate can be treated at high throughput to obtain clear effluent containing 5 ppm or lower Ca. Both lime and ammonia are effective pH control agents and consumed according to stoichiometry.

Jan 1, 1985

By B. H. Bergstrom, J. J. Gilvarry

Previously the authors showed that the Gilvarry equation correctly describes the distribution of fragment size in single fracture, provided the exoclastic particles showing original surface of the specimen are removed from the distribution. In the present work this conclusion has been strengthened in two respects. First, it has been shown that the existence of two peaks in the differential distribution for the endoclastic particles, corresponding to the effect of surface and volume flaws in the interior of the specimen, can be demonstrated from the average of data for a large number of specimens. Second, it has been shown by means of a Coulter counter that data obtained from specimens fractured in gelatin display the behavior at fragment sizes approaching 1 p which is demanded by the limiting form of the Gilvarry equation in this case. In previous work, a rigorous derivation of the proper distribution function for fragment size in single fracture of a brittle solid has been given by Gilvarry,' based on a closely defined physical model and deduced strictly by the laws of probability. Experimental work has been reported by Gilvarry and Berg-str~m,~ confirming the theory in its broad outlines. Subsequently, Gilvarry and Bergstrom extended the theoretical discussion to include comminution and presented experimental data bearing on this point. They have described further experimental results for the case of single fracture recently. The experimental evidence regarding single fracture was rather convincing. However, it was based on only five specimens for which fragment sizes were determined by sieve analyses and three for which measurements in the finer sizes were made on a Coulter counter. The purpose of the present paper is to extend the experimental results as obtained by means of both sieve analyses and the Coulter technique. In the former case, sufficient specimens are included so that the average data should vield ac- curately the detailed behavior of the distribution function for the coarser fragment sizes. In the latter case, measurements for the finer sizes are reported which correspond to single fracture more closely than prior results and fill a lacuna left in the experimental verification. In addition, an extension of the theory given recently bGilvarry for the case of fracture of a two-dimensional solid will be outlined, and experimental results obtained by him will be discussed.6 THREE-DIMENSIONAL CASE Gilvarry' has shown that the Schuhmann size modulus is a measure, in a sense specified later, of the number of activated edge flaws in a specimen undergoing single fracture. Single fracture is defined as that resulting from a single instantaneous application of energy, such as the blow of a hammer whose motion is halted when fracture begins. Plural fracture consists of a short sequence of single fractures, as in a jaw or gyratory crusher; multiple fracture obtains when many applications of energy are made, as in a ball mill. The Griffith flaws associated with fracture of a specimen are flaws occurring within the volume of the body, on the new surfaces created within its interior and on the new edges (intersections of two surfaces) within the body. Fracture proceeds by activation of flaws in the volume of the specimen, in the fracture surfaces throughout its interior, and in the edges produced by intersection of fracture surfaces. If all the flaws and all groups of flaws are distributed at random, independently of other flaws or groups thereof, it has been shown by Gilvarry that the distribution function for fragment size has the form of a Poisson distribution. The fraction y, by weight or volume, passing a sieve of mesh size x is given by where k is an average spacing of activated edge flaws, j2 is an average amount of surface containing one activated surface flaw and i3 is an average volume corresponding to an activated volume flaw. The averages in question are referred to the mean dimension x of a fragment. On the basis of the theoretical

Jan 1, 1962

By R. M. Asimow

The magnetization curves for specimezs containing superparmagnetic particles are considered. It is shown that the curves may differ from a Langezlin function because of particle anisotropy, particle interactions , and the presence of a size distribution of particles. The various causes of particle anisotropy are considered, and magnetization curves for specimens with cubic and uniaxial anisotropy are presented. The magnetization curves depend on the In the particle-size below 100A it is quite difficult to obtain quantitative size and shape information on precipitate particles. All of the available techniques have their limitations; however, quantitative applications of superparmagnetism have not been developed as fully as possible due to a lack of analysis of the complete magnetization curve. With such an analysis it appears possible to obtain from a single magnetization curve of a specimen containing randomly oriented SPM (superparamagnetic) particles a quantitative volume distribution and a description of the particle shape.* sign of the anisotropy energy and in the case of a negative uniaxial anisotropy (prolate spheroids) the resulting curves may differ very considerbly from a Langevin function. A graphical technique is developed whereby it is possible to separate out the effects of the size distribution, the particle interaction, and the particle anisotropy. Thus it is possible to obtain quantitative values for both the particle shape and the size distribution. Langevin function2 I/Is = ctnh(HVIs/k T)-k T/HVIS [ 1 ] where I, is the saturation magnetization, V the particle volume, H the applied field, T the particle temperature, k the Boltzmann constant, and I the magnetization in the direction of the applied field. Such behavior is rarely if ever observed in actual systems. One explanation for this is that the SPM particles do possess a significant anisotropy and thus the magnetic energy associated with the particle depends on the direction of magnetization in a more complicated way than for the isotropic particle of Eq. [I]. In general the magnetic energy E of an isolated SPM particle embedded in a nonmagnetic matrix can be expressed as a sum of several contributions: E = Eh + Ed+Es+Ec [2] where Eh is the external field energy, Ed the energy resulting from the particle demagnetizing factor, E, the magnetostriction energy, and E, the crystalline anisotropy energy. In each term we consider only the part dependent on the orientation of the magnetization vector and the particle axes as the shape of the magnetization curve will be determined by these contributions. Following the same procedure used in deriving the Langevin function,

Jan 1, 1965

By D. A. Woodford

In a constant-load creep test, if the density of nlobile dislocations is assumed constant for strains exceeding that corvesponding to the minimum creep rate, it is shown that the creep rate may be approximated by the equation where E is the nominal strain, o0. is the initial stress, and a' the stress fov unit dislocation velocity. The constant C contains the mean density of mobile dislocations and n is a measure of the stress sensitivity of dislocation celocity. This equation is shoum to be applicable to published data on an alloy steel and on nickel. The degree of plastic instability and hence the creep ductility is dependent on the calue of n for these materials. When instability becomes gross and local macroscopic necking occurs, the assumptions are no longer valid. On the basis of this equation, and the strain-time relation derived from it, a method of predicting the creep behavior at different stresses is suggested. MOst analyses of creep data have been concerned with time-dependent transient creep or time-independ- ent secondary creep in constant-stress tests. The far more widely used constant-load test has been neglected in terms of a mechanistic approach. In general, since the strains involved are usually small, the same laws for transient creep may be applied to both types of tests. However, there is no steady-state creep in a constant-load test since the stress increases continuously. Any apparent steady state observed on a strain-time plot is either fortuitous or illusory, and is generally revealed as a continuously varying creep rate on a carefully constructed strain rate vs time plot.* Transient creep may be understood in terms of a simple differential equation representing the change in mobile dislocation density with time:' where p is the density of mobile dislocations. The first term on the right is related to first-order kinetics of dislocation multiDlication and the second to second-order kinetics of exhaustion. On the basis of this equation, several authors2-4 have found good agreement with experimental transient creep curves for a number of materials. When k1p = k2p2, a steady-state creep

Jan 1, 1968

By AIME AIME

THOUGH the Annual Meeting of the Institute-officially numbered 158 on the records was delayed a bit at the start by low steam pressure on the locomotives bringing members to New York, the crowd that finally arrived more than lived up to expectations, and the technical program had few difficulties because of absent authors or lack of competent discussers. The transportation difficulties were occasioned by the fact that Monday, Feb. 15, was the third coldest day in the 72 year history of the New York Weather Bureau, the official temperature being 8 below zero. The New York Central's premier train, the 20th Century, due at 9:30 a.m., arrived about 6:30 p.m., and the Commodore, another crack train from Chicago, was about equally late.

Jan 1, 1943

By R. T. Hukki, P. Voutilainen

This paper describes a new apparatus for continuous wet fine-screening. Its preferred size range seems to be from 0.1 to 1 mm. The supercritical trommel screen is a short cylindrical trommel of wedge-bar type construction operated at a speed greater than the calculated theoretical critical speed and at a speed lower than the speed at which particles introduced into it will centrifuge. The paper describes results obtained with the prototype supercritical trommel screen in pilot plant scale. The results point to a high capacity and simultaneously to a high sharpness of screening. Finally, an analysis is presented of the forces acting in screening on a supercritical trommel screen. In the era of high speed, high capacity processing of raw materials the conventional slowly rotating trommel screen is often considered a relic from the times passed. A typical trommel screen is the cylindrical trommel rotated about a horizontal or slanting axis at a relatively low speed. Its screening characteristics are well known. Trommel screens of various types of construction, methods of operation, performances and other characteristics have been described in detail by Taggart.1 The theoretical critical speed of a trommel screen is defined by the same well known equation as that applied for grinding mills: where ncritical = the numerical value of the theoretical critical speed in rpm, D 1 = the inside diameter of the trommel in feet, and D2 = the inside diameter of the trommel in meters. ncritical corresponds also to the centrifuging speed provided that the coefficient of friction f between the trommel surface and the outer layer of the charge is = 1.0. In a general case: From Eq. 2 it is seen that in all cases where f < 1.0 the centrifuging speed of the trommel is greater than the theoretical critical speed. The supercritical trommel screen concerns screening operations within that speed range which is between the theoretical critical speed defined by Eq. 1 and the centrifuging speed defined by Eq. 2, under conditions such that the coefficient of friction f<1.0. It is reported by Taggartl that the optimum speed of a conventional cylindrical trommel screen 36 in. in diam was experimentally found to be about 16 rpm. From Eq. 1, the critical speed of this trommel is 44.2 tpm. The indicated optimum speed corresponds to (16/44.2) x 100% = 36.2% of the theoretical critical speed. The optimum speed range based on information available seems to vary from 33% up to 45% of the theoretical critical value. The trommel screen operated at a supercritical speed: operates at a speed greater than the calculated theoretical critical speed; operates at a speed lower than the speed at which the charge introduced into it will centrifuge; operates within the supercritical speed range in such a way that the coarse fraction of the charge must slide in respect to the inside surface of the trommel; the outer layer of the said fraction next to the screen tends to proceed in the same direction as any selected point on the trommel surface, but now at a lower speed, and indeed at a subcritical speed; allows to a certain degree adjustment of the maximum determining particle size x of the fine product simply by a variation of the speed of the trommel within the supercritical speed range. With increasing trommel speed, finer and finer material only will get the opportunity to find its way into the fine product while the screen opening remains constant. In conventional practice, the low speed trommel is generally used for sizing of coarse and medium coarse material, but seldom for fine screening. The characteristic feature of the product passed through the conventional trommel is that the determining size x of the biggest particle is barely smaller than the nominal size of screen opening. The supercritical trommel screen, on the other hand, is best suited for sizing of relatively fine material. Furthermore, the characteristic determining size x of the biggest particle in the fine product can be substantially smaller than the nominal width of the screen opening or slot. In the trommel screen best suited for the applications

Jan 1, 1965

By A. E. Powers

YEARS of experience and research have shown that molybdenum, tungsten, and vanadium are among the most useful and effective elements in augmenting the high-temperature strength of heat-treatable, ferritic steels. Grün, for example, in conducting an early survey of the strengthening effects of various elements in annealed, low-carbon steel at 750° and 930°F (400° and 500°C), found molybdenum and vanadium to be the most effective.&apos; Holtmann comprehensively studied the strengthening effects of molybdenum and vanadium in quenched and tempered steels at 930°F as a function of microstructure and carbon content.&apos; He found creep strength to be related to the saturation of the austenite at the austenitizing temperature, such that strength is increased by alloying until the y loop is reached—the terminus of complete austenitization. Beyond this degree of alloying, the inability to heat treat will result in lower strength, at least for low and moderate creep temperatures. Tungsten, owing to higher cost than molybdenum, has been little used in ferritic high-temperature steels. As a result, very few investigations have been made of its high-temperature strengthening ability, and reliable data on its effectiveness are not available. Grün rated tungsten far less effective than molybdenum at 930°F (500°C) on a weight-percentage basis.&apos; However, Tammann has found that tungsten is as effective as molybdenum in raising the recrystallization temperature of iron. For this reason Smith, in a review of the subject, has advocated a re-examination of the influence of tungsten on the high-temperature strength of steel.&apos; In any study of the effects of alloying additions on high-temperature properties, recognition must be made of the many variables involved, some of which can be controlled but have been ignored in innumerable investigations of the past, and some of which are difficult or even impossible to control. One cannot, for example, assign a definite strengthening index to any one alloying element, for this will be dependent upon the microstructure (heat treatment and mechanical treatment), testing con- ditions (temperature, time, and stress), and the complete composition of the steel (accompanying alloying elements, impurities, etc.). One ever-appear ing variable, hardness or tensile strength at room temperature, may be eliminated by heat treating all of the alloys to a single hardness level. An attempt may be made to control the variable of primary quenched structure by oil or water quenching the test specimen. The control of such variables may not be possible in cases of widely varying compositions, but at least such deviations should be recognized. Material and Procedure The alloys, made as 30-lb ingots in an induction furnace, all had the same base composition of about 0.18 pct C, 0.85 pct Mn, and 0.48 pct Si. They were grouped as follows: Mo Group—Containing up to 5.2 pct Mo. W Group-Containing up to 6.0 pct W. V Group—Containing up to 3.3 pct V. Mo-V Group—Containing up to 2.7 pct Mo and up to 1.4 pct V. Mo-W Group—Containing up to 2.5 pct Mo and up to 2.5 pct W. The steels, listed in Table I, were forged to ¾ in. sq bars and the material for the high-temperature, rupture-test specimens was further swaged to %-in. round bars.

Jan 1, 1957

By H. B. Small

The Ottawa river, the northeastern boundary of the Province of Ontario, and the dividing line between the latter and the Province of Quebec, has long been famous for the rafts of timber floated over its waters from the depths of the forest, and other poets besides Moore, have immortalized its beauties in verse. But with the ad vent of the railway which now pierces the forest solitudes, the days of rafting were numbered ; and the boat song is now heard no more on "Ottawa&apos;s tide," or at such long intervals only, that, when heard, it seems an echo of the past. The lumber trade is fast leav ing Ottawa City, the old headquarters of the business; and such square timber as is now cut is gradually finding other outlets than shipment to Great Britain, and other channels of transportation than the Ottawa river. Skirting the northern shore of this great river runs a vast chain of hills, assuming at times the altitude of mountains. Their geological character marks them as remnants of the earliest land of this conti nent. Following the course of the St. Lawrence from the Gulf of that name to the confluence of the river with the Ottawa, the course of which latter they then pursue, the range has been styled " the Lau rentians." Rolling in long undulations, with rounded, rather than rugged or pointed summits, they leave a margin of 8 or 10 miles, dipping in a gentle slope to the water&apos;s edge, rich for agricultural use, and dotted here and there with farms and settlements. Beyond this margin bold hills stretch northerly to blue mountains, rich in iron, lead, plumbago, and other minerals. The Apatite District.—One of these minerals is apatite, or phos phate of lime, the use of which as a material for the manufacture of superphosphate as a fertilizer has become the basis of the industry bidding Fair to prove ere long one of the chief elements of Canadian trade. So rapid has been the growth of this new industry that if the lumber business were to disappear from this mineral district, its void would be filled by that which has sprung up in connection with phosphate.

Jan 1, 1893

By W. H. Yarroll

This paper presents a general discussion of the utility of the statistical technique known as multiple correlation, and gives three specific examples of its application. The first demonstrates the most simple form, or straight-line, multiple correlation. The other two demonstrate multiple correlation analysis in best-fitting third-degree parabolas. With the increasing availability of digital computers, the method becomes entirely feasible where heretofore its use was impractical. The advantages of the method are discussed, and curves are presented which were developed by computerizing the regression equations developed in the examples. The method described in this paper is for use with complex systems, and the examples given are complex metallurgical systems. This subject falls under the general classification of cybernetics, which is defined&apos; as "the science of control and communication, in the animal and the machine." Machine, in this case, can include chemical and physical processes which take place within machines and processing equipment of all kinds. The classical approach to scientific investigation has been the construction of simple models and the changing of variables one at a time. This method is wholly inadequate for obtaining useful information from the complex systems of modern technology including many of our flotation and hydrometallurgical processes. Cybernetics offers the method by which complex systems which have been implemented as an art in the past can now be analyzed with all the discipline of a science. Mathematical techniques for achieving multiple correlation analysis have decided advantages over some of the other statistical methods.2-4 Multiple correlation does not require a series of experiments that have been rigidly planned as do many of the other statistical methods. For this reason, it can be used effectively for interpretation of information from op- erating plants, where planned experiments are impractical, as well as for laboratory experiments. First-degree multiple correlation has been used for many years, and was useful, but limited to linear or nearly linear relationships. The technique described in this paper provides a method for analyzing systems which may be non-linear. This particular technique is multiple correlation analysis in best-fitting third-degree parabolas. It is quite possible that lack of reference to the technique has been due to the overwhelming mass of computations it requires even for relatively simple problems. With the advent of computers, however, its use has become entirely feasible. For the benefit of those who may not be familiar with the subject, it might be well to pause at this point to discuss multiple correlation analysis — what it is and what it achieves. To go back to the old familiar fitting of a set of points with a best-fitting straight line by the least squares procedure, it is conceded that this a good method where there is only one independent variable influencing the dependent variable under consideration, and providing that the relationship is linear. In most fields of investigation, however, there are usually a number of factors exerting important influence, and they frequently bear relationships with the dependent variable other than straight line. Under these conditions, it is easy to see how misleading a simple correlation study might be. Multiple correlation can be used for any number of variables. Within the experience of the writer, this technique has been used to establish regression equations for determination of carbon rate, burden permeability, and production rate on iron blast furnaces, production rate on open hearth steel furnaces, life of molds for steel ingots, rolled steel tensile strength and various defects in rolled products, the performance of ore dressing equipment, and optimization of extractive metallurgical process variables. The discovery of mathematical correlation does not prove, per se, true cause-and-effect relationship, but simply establishes a hypothesis. If the regression equation can be used to make successful predictions of what will happen with future arrays of independent variables, then one can feel reasonably assured that true cause-and-effect relationships have been discovered.

Jan 1, 1968

By Lawrence A. Soltis

Senior engineering or executive management positions are filled by engineers who are evaluated on their performance, knowledge, skill, and maturity. Not only is technical expertise required but a knowledge of sales and marketing, finance, law, industrial relations, and public affairs is necessary. The University of Wisconsin-Extension offers an innovative post-baccalaureate degree program blending technical and professional subjects the Professional Development Degree in engineering (PDD)-designed to bring various opportunities for learn-

Jan 4, 1978

By Rudolf Gahl

SOME time ago the Detroit Copper Mining Co. had to decide the question whether it would pay to re-treat slime-tailings, and several machines were tested in order to ascertain the type of construction which would give the greatest saving. In previous tests on the ore of this company, several tables proved far inferior to the Frue vanner, and for this reason they did not receive any serious consideration. In the late tests, however, one table was found to surpass the vanner in the percentage of saving made. The Frue vanner used in these tests had been adjusted approximately to the slope which the slime-vanuers in the concentrator of the Detroit Copper Co. had at that time, about 2 in. between the inside of the wooden posts, or 0.272 in. per ft. It had not been determined, however, if this slope was the most economical one for treating the slime-feed in the mill, or for re-treating the tailings from the slime-vanners, and I was instructed to ascertain by test-runs, under different conditions, the best adjustments for the work to. be done. In order to determine if a change in the adjustments of the machines would improve the results, it seemed sufficient to continue running the tests between the vanner and the table before mentioned, keeping the feed and all other conditions the same, but. varying the adjustments of the vanner .from run to run. I employed a vanner-man of long experience to operate these machines, who expressed the opinion that a slope between 2 3/8 and 2.5 in. between the posts (0.323 and 0.340 in. per ft.) would give the best results. Some runs made this way gave a considerable improvement. While for a slope of 2 in. (0.272 in. per ft.) the saving had been only 40.5 per cent. of that of the table, it .was 49.2 per cent. for 2.5 in. (0.340 in. per ft.) slope. A decrease of

Sep 1, 1909