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1. What Is a Rock Burst? . . . . 569 Jack Spalding . . 569 A. F. Robertson . 569 W. R. Crane . 569 G. S. Rice......569 P. J. Shenon........... 569 L. C. Graton........... 569 2. What Are the Causes of Rock Bursts? 573 Jack Spalding..........573 A. B. Yates and P. J. Shenon 574, 578, 592, 596 A. F. Robertson . . . . . 575, 595 W. R. Crane. ... 579 G. S. Rice.........582 Oscar Weiss .........582 P. B. Bucky..........582 P. H. Bird.....588, 592, 593, 595 M. K. Hubbert.........593 G. Wheeler.......... .593 B. F. Tillson........593, 595 T. T. Read............594 3. How Can Rock Bursts Be Prevented?. 597 Jack Spalding..........597 A. B. Yates and P. J. Shenon ... 598 A. F. Robertson.......599 W. R. Crane....... .602 G. S. Rice............602 Page 4. How Can Rock Bursts Be Predicted?. 602 Jack Spalding.........602 A. F. Robertson.......602, 603 A. B. Yates and P. J. Shenon ... 602 W. R. Crane......602 G. S. Rice......602 B. F. Tillson...........603 5. How Can Rock Bursts Be Controlled? 603 Jack Spalding..........603 A. F. Robertson.......603 W. R. Crane...........604 A. B. Yates and P. J. Shenon 604 Oscar Weiss........605 G. S. Rice......- 604, 609 R.D.Hoffman..609, 610 R. D. Hall..........609 R. H. Cromwell . . 609 P. J. Shenon...........609 P. B. Bucky......609, 611 B. F. Tillson.........609, 611 A. B. Yates...610, 611 P. H. Bird.......610 6. General Discussion........ 611 Jack Spalding.......... 611 R. D. Parker....... . 616 C. Baring Horwood........ 618 P. B. Bucky........... 619 Foreword This symposium brings together points of view, experiences and ideas on rock bursts from a goodly portion of the globe. Some conceptions, particularly those regarding the necessity of depth, have been fairly well shattered, as we find that they are present in the water tunnels of New York, on the surface at marble quarries in Vermont, and in the coal mines of the United States, as well as in the deep mines of the South African and Kolar gold fields, and in the nickel, copper and gold mines of Canada. Their occurrence under such a variety of conditions is, therefore, a challenge, which, if successfully met and overcome,

Jan 1, 1946

By Edmund J. Pryor

DURING the war years restrictions on travel, pressure of work, and the irregular arrival of technical literature from abroad combined to severely isolate Great Britain in a period of intense war expansion of the art and practice of mineral dressing. Many British technicians were fully occupied with the day-to-day problems of improvising substitutes as regular sources of supply failed. and with mastering the strange demands and working conditions of wartime. After a long day spent between ones laboratory and production work, the rest of the waking hours were often filled with fire watching or home guard patrol activities, substituting for a night-shift manager, or "resting" in a dugout while the bombs came down. There was no time for serious study of such technical literature as survived the Atlantic crossing.

Jan 1, 1947

By K. Reinhardt

THE idea of burning blast-furnace gases directly in gas-engines, instead of under steam-boilers, as had previously been done, was first put into practice barely ten years ago, almost simultaneously in Great Britain, Germany and Belgium. The pioneers of this movement made their first experiments with small engines. After these experiments had given satisfactory results, and it had been shown that the thermal value of the poor blast-furnace gases, in spite of defective scrubbing, could with safety be directly transformed into mechanical work in the gas-engine, there very soon arose a considerable demand for gas-engines of large power, similar to the large steam-engines employed in metallurgical works. In face of these sudden requirements, the gas-engine builders were placed in a difficult position; for up to that time the gas-motor was considered as suitable for small engines only, and it was generally believed that the limit of size bad been attained with 100 to 150 effective h.p. in a single cylinder. Manufacturers of gas-motors, however, did not underrate the advantages offered by this new field for their manufactures, and it so happened that in Germany the Berlin-Anhaltische Maschinenbau-Gesellschaft, of Dessau, was the first to undertake the construction of a 600-h.p. two-cycle gas-engine, with two cyl¬inders of the Oechelhäuser-Junkers type, for the Hoerder Mining & Smelting Company. The engine was started in 1898, and, with a few improvements and alterations, is still working satisfactorily. This engine worked with astonishingly high of efficiency, considering the period. The builders were therefore

Nov 1, 1906

By T. F. Witheree

The Fletcherville Furnace was built in 1864 and 1865, making its first blast from August until October of the latter year, when it was blown out to prevent its " bunging-up." Repairs were made in time to enable it to be blown in again December 12th, 1865, the blast ending October 7th, 1866. Total product 1921.15 tons iron, an average of 6.8.2.5 tons per day, from ores yielding 44.8 per cent. Consumption of charcoal 223.2 bushels per ton of iron. The furnace journal up to this time shows no record of furnace dimensions, or temperature of the blast, but as near as can be ascertained, they were as follows, viz.: Height of stack, 42 feet. Diameter of bosh, 11 feet. Angle of bosh, 71/2 inches to 12 inches rise, about 58°. Diameter of open tunnel head, 42 inches. Number of tuyeres 3 ; each 3 inches in diameter. Dam 15 inches high. Tuyeres 24 inches high. Tymp 224 inches high. Diameter of steam cylinder, 20) inches. } Diameter of blast cylinder, 64 inches. } Stroke 5 feet. The engine is direct-acting horizontal non-condensing. December 26th, 1866, the furnace was again put in blast, having been considerably altered in the crucible; the height of stack, bosh, and tunnel head remaining as before. Six tuyeres were put in, three in each of the side arches. The hearth or crucible was rectangular in form, 3 feet wide x 31/2 feet long x 64 feet high. Inclination of bosh 58°. Height of tuyeres 26 inches; nozzles 21/4 inches diameter. Temperature of blast estimated to be about 500°.

By AIME AIME

SOME 65 members of the Institute, including most of the Local Section delegates and several Directors and officers, were on hand for the Annual Business Meeting of the Institute held in the Engineering Societies Building on Monday, Feb. 21, at 4:30 p.m., immediately following the second session of the Local Section Delegates Conference. President Mathewson presided. The meeting was largely taken up with the presentation of committee re- ports, discussion of which was invited. F. E. Wormser presented the report of the Admissions Committee ; Philip Kraft, Papers and Publications Com-

Jan 1, 1944

By Frank L. Hess

BERYLLIUM is demanding more of the limelight, and the output of beryllium copper (containing 2% to~ 3 per cent of beryllium) seems to have grown 60 per cent above that of 1936, which was double that of 1935. There is increasing interest in beryllium-aluminum alloys and small quantities are being marketed at $50 per lb. for the contained beryllium. Other alloys also can be produced. Further price decreases for beryllium copper (now $23 per lb. for the contained beryllium) seem , possible and desirable. No difficulty has been experienced in obtaining beryl and a 'reserve stock has been built up. One supplier heretofore found reliable has offered to furnish 200 tons per month. Supplies during 1937 have come from the Black Hills in South Dakota, Colorado. India, and South America

Jan 1, 1938

SOUTHERN CALIFORNIA LOCAL. SECTION Executive Committee SEELEY W. MUDD, Chairman C. COLCOCK JONES, Vice-Chairman FREDERICK J. H. MERRILL, Secretary-Treasurer, 631 Higgins Bldg., Los Angeles, Cal. RALPH ARNOLD A. B. CARPENTER In. order to make the meetings of the, Section more interesting and fruitful, the Executive Committee has formed a sub-committee on programs for. Section meetings, which announces for the coming autumn and winter season, four dinner meetings, at intervals of two months, in which the co-operation of all Section members is urgently. requested. The subjects chosen for discussion at these meetings, with the proposed dates, are as follows: Sept. 28, 1915. Mining Geology of Mojave County, Arizona. Dec. 14, 1915. General Geology and Mining Conditions in Southern California. Feb. 1, 1916. Petroleum, its Geology and Technology. April 4, 1916. General Mining Conditions in. South America. F. J. H.. MERRILL, Secretary.

Jan 10, 1915

[Separates of all the Technical Publications published in 1930 are available at Institute headquarters. All the papers are on file in public, university and technical libraries, and when so indicated in the list, may be found in the Transactions.] Metal Mining Technical Publi- Title Author Meeting Tran~. cation Volume No. and Page* 264-A.29 Quicksilver Industry in 1929. Im- L. H. Duschak San Francisco T30, 283, 319 provements in the Metallurgy of C. G. Maier and Oct., 1929 Quicksilver and Symposium on The others Present Status of the Quicksilver Industry (With Discussion) (37) 271-A.30 Observation on Ground Movement R. E. Palmer New York T30. 168 and Subsidences at Rio. Tinto Feb.. 1930 Mines, Spain (20) 274-A.31 Development and Installation of the C.L.Berrien New York T30, 139, 166 Hawkesworth Detachable Bit (29) Feb., 1930 276-A.32 Protective Measures . Against Gas 0. A. Glaeser New York T30, 129. 167 Hazards at United Verde Mine (11) Feb., 1930 287-A.33 Use and Cost of Compressed Air (12) R. S. Lewis New York Feb., 1930 314-A.34 Miami Copper Company Method of F. W. Maclcnnan New York T30, 39, YO Mining Low-grade Orebody (44) Feb., 1930 319-A.35 How Human Beings Respond to W. J. McConnell New York Changing Atmospheric Conditions Feb., 1930 (9) 324-A.36 Vertical and Incline Shaft Sinking at Arthur B. Foote San Francisco T30, 87 North Star Mine (21) Oct., 1929 32bA.37 Governmental Control of the Pro- W. E. Colby New York duction and Sale of Mineral Re- Feb.. 1930 sources (With Discussion) (16) 333-A.38 Some Recent Developments in Open- E. E. Hunner New York T30, 106, 117 pit Mining on the Mesabi Range Feb.. 1930 (25) 334-A.39 Mining Methods and Costs at Presi- V. D. Howbert El Paso dio Mine of American Metal Co. of R. Bosustow Oct., 1930 Texas (15) 339-A.40 Operation of Pressure Fans in Series W. 8. Weeks New York (8) V. 6. Grishkevich Feb., 1931 364-A.41 Top Slicing with Filling of Slices as H. Willey El Paso Used at the Charcas Unit of Com- Oct., 1930 pania Minera Asarco, S. A. (17) 373-A.42 Drill Sampling and Interpretation of H. T. Matson New York Sampling Results in the Copper G. A. Wallis Feb.. 1931 Fields of Northern Rhodesia (17)

Jan 1, 1930

By Orlando E. Romig

As metals and alloys are composed of an aggregate of allotriomorphic crystals or grains, each possessing an individual orientation, the physical characteristics of a metal or an alloy are closely related to the properties of the individual crystals. The preparation and study of single metallic crystals are, therefore, matters of considerable importance. The advent of the X-ray spectrograph as a valuable metallurgical tool has magnified the importance of this subject, because the interpretation of some X-ray spectrographs is difficult unless single crystals are used in these studies. Previous Work The first paper, as far as the writer knows, on the behavior or preparation of single crystals of metals is by Baker.' He describes the behavior of extruded wires of sodium and potassium. These wires, when pulled in tension, instead of showing the usual conical fracture common to most metals, had a chisel-shaped fracture when they were broken. I and 11, Fig. 1, have a similar fracture. Baker checked his results by preparing single crystal wires from molten sodium and potassium and observing their properties. He pre- pared the wires by filling glass tubes, under oil, with the molten metal. The surfaces of the strained wires showed slip bands of remarkable clearness of which photographs are shown in his paper. He concluded that these wires were single crystals and "that the portions of the metal brought into play are cubes. Such cubes, when placed so that a plane through two opposite edges was parallel to the axis of the wire, would allow of lateral contraction by faces gliding over one another in one direction only and not in the direction at right angles."

Jan 1, 1927

By R. E. Heithecker

Almost every oil well drilled into limestone formations in Kansas is treated with hydrochloric (muriatic) acid upon completion: to increase potential capacity of well and thereby increase its "daily allowable" production; to shorten time required to produce recoverable oil; and to increase quantity of oil recovered ultimately from reservoir. Acid treating marked a forward step in the producing fields of Kansas; in fact, many old limestone fields that almost had reached their economic producing limit were "rejuvenated" with acid and their capacities to produce increased several times. It also caused a marked increase in the ultimate oil recovery of some old and nearly depleted fields of Kansas. The effect of the acid was due to the cleaning-out action by the acid at the face of the limestone, the enlargement of the small drainage channels, and the apparent penetration of the acid to previously undrained porous and saturated strata. Studies of the effects of acid were made in the Fairport field, three groups of wells in the El Dorado field and the Shutts field. Estimation of increased recoveries resulting from acid in these fields and groups of wells ranged from 1000 to 2400 bbI. per acre. Limestone structures that had been tested by drilling and found noncommercial were later completed as commerical oil-producing formations through the use of acid. The Kansas City formation, Valley Center field of Kansas, is an example. Increased oil production and revenue from the old fields justified the reconditioning of equipment, which in most cases had become in poor mechanical condition. The first treatment with hydrochloric acid of an oil well in Kansas was in October 1932, and by the end of 1937 almost 6000 wells had been treated. Many wells were treated more than once and the total number of treatments exceeded 8000 by the end of 1937. Approximately 12 3/4 million gallons of acid was required for these treatments. The report includes 15 illustrations and 16 tables.

Jan 1, 1939

By R. E. Heithecker

Almost every oil well drilled into limestone formations in Kansas is treated with hydrochloric (muriatic) acid upon completion: to increase potential capacity of well and thereby increase its "daily allowable" production; to shorten time required to produce recoverable oil; and to increase quantity of oil recovered ultimately from reservoir. Acid treating marked a forward step in the producing fields of Kansas; in fact, many old limestone fields that almost had reached their economic producing limit were "rejuvenated" with acid and their capacities to produce increased several times. It also caused a marked increase in the ultimate oil recovery of some old and nearly depleted fields of Kansas. The effect of the acid was due to the cleaning-out action by the acid at the face of the limestone, the enlargement of the small drainage channels, and the apparent penetration of the acid to previously undrained porous and saturated strata. Studies of the effects of acid were made in the Fairport field, three groups of wells in the El Dorado field and the Shutts field. Estimation of increased recoveries resulting from acid in these fields and groups of wells ranged from 1000 to 2400 bbI. per acre. Limestone structures that had been tested by drilling and found noncommercial were later completed as commerical oil-producing formations through the use of acid. The Kansas City formation, Valley Center field of Kansas, is an example. Increased oil production and revenue from the old fields justified the reconditioning of equipment, which in most cases had become in poor mechanical condition. The first treatment with hydrochloric acid of an oil well in Kansas was in October 1932, and by the end of 1937 almost 6000 wells had been treated. Many wells were treated more than once and the total number of treatments exceeded 8000 by the end of 1937. Approximately 12 3/4 million gallons of acid was required for these treatments. The report includes 15 illustrations and 16 tables.

Jan 1, 1939

By James O. Elton

This paper covers, besides laboratory work, a study of actual operation at the Washoe Smelter over a considerable period of time, together with the results of a visit to the Midvale plant of the United States Smelting & Refining Co., near Salt Lake. For the latter privilege, as well as permission to publish the resulting data herein given, I am indebted to George W. Heintz, General Manager of the Midvale plant, and here take pleasure in expressing my appreciation for the many courtesies extended to me by Mr. Heintz and members of the technical staff at the smelter. Almost all of the world's supply of arsenic is recovered as a byproduct in the smelting of other metals. It is seen 'on the market in various forms, the most common being arsenic trioxide, the " white arsenic " of commerce, which is sold as a heavy white powder, or in white, glassy, translucent masses. The trioxide is used in the manufacture of pigment, glass, and insecticides. About 50 per cent. of the domestic consumption is supplied by imports. Statistics of Arsenic Trioxide in United States.' Production. Consumption. Price Per Pound. Year. Tons. Tons. Cents. 1907..........1.010 5.471 5 1908,.........1,302 6,098 33/4 1909,.........1,007 4,600 2 7/8 1910,.........1,526 5,428 2 1/2 1911,.........3,081 6,539 2 1912,2........ 2,926 Closed at 4 7/8 Arsenic occurs in combitlation with sulphur and the metals in a large number of minerals. It is present in small amounts in many ores. In the roasting and smelting furnaces many of its compounds break down, liberating arsenic trioxide, which is volatilized and carried by the gases into the flue system, where a part is condensed and settles with the flue dust.

Jan 1, 1914

By Paul F. Kerr, Donald M. Hausen

Fine colloidal gold near Carlin, Nevada is disseminated in leached carbonate strata of the Roberts Mountains Formation in the Lynn "window" of the Roberts Mountains thrust fault. The ore body is generally stratiform and is more or less conformable to altered beds near the top of the formation, underlying Devonian limestones. Two sequences of mineralization are recognized: ( 1) an earlier base metal-barite assemblage related to early Cretaceous intrusives (121 ± 5 m.y.), and (2) a later low temperature Au-As-Hg-Sb assemblage of near surface emplacement. The earlier sequence consisting of sparse galena and sphalerite in barite with anomalous amounts of zinc, lead, nickel and copper, associated with dikes of dacitic composition, is of little economic importance. The later sequence of gold, realgar, cinnabar, and stibnite associated with extensive silicification and argillic alteration of limestone beds, has resulted in important deposits of gold. Argillic alteration of hydrothermally leached carbonate strata has provided the environment in which the most prominent gold deposition took place. Carbonate minerals in the limestone host rock have been replaced by microcrystalline quartz and chalcedony to form stratiform silica masses and recrystallized lenses of euhedral quartz. Zones of porous silicification are light gray to white, elliptical in shape, and more or less follow bedding. Silicification is bordered by argillic alteration and pyritization. Deposition of gold usually lies in a zonal pattern that encircles chimney areas of silicification.

Jan 1, 1968

US 4,132,758-Leaching of copper sulfide ore using nitrogen dioxide as the oxidant A slurry of ore in sulfuric acid is contacted with a nitrogen dioxide-containing gas at a temperature below 11 5" C and a pressure of from atmospheric to 35 PSI, the slurry agitated, and the resulting nitric oxide from the slurry regenerated to nitrogen dioxide for reuse About 90% of the copper In the ore IS dissolved, and the leach solution is separated for further processing. This procedure is also useful for sulfide ores of silver, molybdenum, nickel, cobalt, and zinc T C Franklewicz and R E Lueders, assigned to Kennecott Copper Corp Jan 2, 1979 7 pp (423-27) Filed 1 1-30-77 (855,983) (Drawings below ) US 4,138,231-Wet-cleanlng of gases from the roasting of copper sulfide ore, zinc sulfide ore, pyrite, or arsenopyrite The gases are washed in dilute sulfuric acid circulating in a closed system, the wash water treated to remove arsenic, the washed gas condensed by cooling; and the condensate separated, purified of residual arsenic, and neutralized B G V Hedenas, J E Wiklund, T R H Johansson, and KA Melkersson, assigned to Boliden AB Feb 6, 1979 7 pp (55-71). Filed 3-30-77 (782,908) Priority Sweden, 4-9-76 (76/04,219) (Flow diagram at right ) US 4,148,862-In the acid-leaching of silicate-bearing calcined zinc sulfide ore, finely divided calcine is leached at elevated temperature with sulfuric acid, and additional calcine is added at an optimum rate to precipitate SI~ICIC acid in the same stage In an easily settling, readily filterable form Reactions take place at a silica concentration so low that the solution is not greatly oversaturated An anionic flocculant- may be added to the slurry immediately before the filtration step S. P Fugleberg and J T. I Poijarvi, assigned to Outokumpu Oy Apr. 10, 1979 4 pp (423-106). Filed 10-6-77 (840,041) Priority Finland, 10-8-76 (76/2880)

Jan 1, 1980

For the year ending February, 1923 PRESIDENT ARTHUR S. DWIGHT, District 0 NEW YORK, N. Y. PAST PRESIDENTS HERBERT HOOVER, District 4 WASHINGTON, D. C. EDWIN LUDLOW, District 0 NEW YORK, N. Y. FIRST VICE-PRESIDENT J. V. W. REYNDERS NEW YORK, N. Y. TREASURER CHARLES F. RAND NEW YORK, N. Y. SECRETARY FREDERICK F. SHARPLESS,. . . . . NEW YORK, N. Y. ASSISTANT SECRETARY PERCY E. BARBOUR NEW YORK, N. Y.

Jan 7, 1922

By Herman Dykstra, R. L. Parsons

A numerical method for solving partial differential equations in steady state fluid flow is described. This method, known as the "relaxation method," has two advantages over analytical methods: (1) practically any problem can be solved, and (2) a solution can be obtained quickly. A disadvautage is that the solution is not general. The method is applied to core analysis and relative permeability measurement to calculate constriction effects and to calculate the true pressure drop measured by a center tap in a Hassler type relative permeability apparatus. Further applications are suggested. INTRODUCTION Many problems in fluid flow cannot be solved analytically because of the nature of the boundary conditions. For many problems, however. an exact answer is not necessary because boundary conditions are not exactly defined or the parameters describing the porous medium are not accurately known. The relaxation method can be used to obtain an approximate answer easily and quickly for the flow of incompressible fluids in porous media. The method can also be used for other types of problems, such as determining the stress in a shaft under load. or the temperature distribution during steady state heat flow. In this discussion only calculations concerned with the flow of fluids in porous media will be considered. The method was introduced by R. V. Southwell in 1935.' THEORY The treatment given here follows that given by Enimons.2 Consider a porous medium to be replaced entirely by a net of tubes of equal length and uniform cross-sectional area as shown in part in Fig. 1. Assume that the net of tubes behaves exactly like the porous medium which it replaces; that is, the net can be made fine enough to reproduce exactly the porous medium. Assume also that Darcy's Law can be used to calculate the flow from one point to another point through these tubes. The flow from point 1 to point 0 is KA . ------ P-P) .......(11 where a is the distance between points: K is the "permeability" of a tube; A is the cross-sectional area of a tube; is the viscosity of the liquid in the porous medium; and (P1 — P0) is the pressure difference between point 1 and point 0. In like manner the flow can be calculated from points 2, 3, and 4 to point 0. The net flow into point 0 is Qo = KA/µa (P1 + P2 + P33 + P4-4P0) . . (2) MB For an incompressible fluid the net flow into point 0 will be zero or, Q. = 0. This says that at point 0 fluid is neither being accumulated nor depleted. 'Therefore. P1 + P2 + P3 + P4 - 4P0 = 0 .... (3) . If. now. with specified boundary conditions. the pressure i.; known at a finite number of points in a given region, as at the points shown in Fig. 1, Equation (3) will be satisfied at every point. If, on the other hand, the pressure is not known, the pressure can be guessed at these points. Then. unless the guess is perfect. Equation (3) will not be satisfied at all of the points. When Equatiol~ (3,) is not satisfietl. let d = P1 + I?, + P, + P, - If' .,....(4) where 6 is an apparent error and is called the residual at point 0. Equation (4) shows how much the pressure guess is in error at point 0 with respect to the surrounding points. A positive residual means that the pressure is too low, and a negative residual means that the pressure is too high. To bring the residual, 6. to zero in order to satisfy Equation (3). it is necessary to make changes in the pressure guesses. Equation (4) shows that a +1 change in Po will change the residual at point 0 by -4. A +1 change in the pressure at any of the four surrounding points will change the residual at point 0 by +l. Thus it can be seen that a change at any point will affect the residual at that point and the four surrounding points. By changing the pressure from point to point, all of the residuals can eventually be brought nearly to zero and the problem will be solved. This procedure is the essence of relaxation methods and is used to relax the residuals so that Equation (3) is satisfied at every point. The procedure can be most easily explained in detail by solving a simple problem. as Southwell says, "To explain every detail of a practical technique is to risk an appearance of complexity and difficulty which may repel the reader. A

Jan 1, 1951

By R. L. Parsons, Herman Dykstra

A numerical method for solving partial differential equations in steady state fluid flow is described. This method, known as the "relaxation method," has two advantages over analytical methods: (1) practically any problem can be solved, and (2) a solution can be obtained quickly. A disadvautage is that the solution is not general. The method is applied to core analysis and relative permeability measurement to calculate constriction effects and to calculate the true pressure drop measured by a center tap in a Hassler type relative permeability apparatus. Further applications are suggested. INTRODUCTION Many problems in fluid flow cannot be solved analytically because of the nature of the boundary conditions. For many problems, however. an exact answer is not necessary because boundary conditions are not exactly defined or the parameters describing the porous medium are not accurately known. The relaxation method can be used to obtain an approximate answer easily and quickly for the flow of incompressible fluids in porous media. The method can also be used for other types of problems, such as determining the stress in a shaft under load. or the temperature distribution during steady state heat flow. In this discussion only calculations concerned with the flow of fluids in porous media will be considered. The method was introduced by R. V. Southwell in 1935.' THEORY The treatment given here follows that given by Enimons.2 Consider a porous medium to be replaced entirely by a net of tubes of equal length and uniform cross-sectional area as shown in part in Fig. 1. Assume that the net of tubes behaves exactly like the porous medium which it replaces; that is, the net can be made fine enough to reproduce exactly the porous medium. Assume also that Darcy's Law can be used to calculate the flow from one point to another point through these tubes. The flow from point 1 to point 0 is KA . ------ P-P) .......(11 where a is the distance between points: K is the "permeability" of a tube; A is the cross-sectional area of a tube; is the viscosity of the liquid in the porous medium; and (P1 — P0) is the pressure difference between point 1 and point 0. In like manner the flow can be calculated from points 2, 3, and 4 to point 0. The net flow into point 0 is Qo = KA/µa (P1 + P2 + P33 + P4-4P0) . . (2) MB For an incompressible fluid the net flow into point 0 will be zero or, Q. = 0. This says that at point 0 fluid is neither being accumulated nor depleted. 'Therefore. P1 + P2 + P3 + P4 - 4P0 = 0 .... (3) . If. now. with specified boundary conditions. the pressure i.; known at a finite number of points in a given region, as at the points shown in Fig. 1, Equation (3) will be satisfied at every point. If, on the other hand, the pressure is not known, the pressure can be guessed at these points. Then. unless the guess is perfect. Equation (3) will not be satisfied at all of the points. When Equatiol~ (3,) is not satisfietl. let d = P1 + I?, + P, + P, - If' .,....(4) where 6 is an apparent error and is called the residual at point 0. Equation (4) shows how much the pressure guess is in error at point 0 with respect to the surrounding points. A positive residual means that the pressure is too low, and a negative residual means that the pressure is too high. To bring the residual, 6. to zero in order to satisfy Equation (3). it is necessary to make changes in the pressure guesses. Equation (4) shows that a +1 change in Po will change the residual at point 0 by -4. A +1 change in the pressure at any of the four surrounding points will change the residual at point 0 by +l. Thus it can be seen that a change at any point will affect the residual at that point and the four surrounding points. By changing the pressure from point to point, all of the residuals can eventually be brought nearly to zero and the problem will be solved. This procedure is the essence of relaxation methods and is used to relax the residuals so that Equation (3) is satisfied at every point. The procedure can be most easily explained in detail by solving a simple problem. as Southwell says, "To explain every detail of a practical technique is to risk an appearance of complexity and difficulty which may repel the reader. A

Jan 1, 1951

By Frances H. Clark

IN a concern with the varied interests of the Western Union Telegraph Co., where practically all types of metals, both ferrous and nonferrous, are utilized, many types of failures of materials occur. These have to do not only with outside plant construction, such as corrosion and fatigue of line wire and cable, but also with inside plant equipment operating at such high speeds that rapid deterioration of metal. parts due to fatigue and wear results. Both corrosion and fatigue affect the life of copper wire so its normal life in any particular locality is largely dependent on the atmospheric conditions. Tensions vary widely owing to changes in temperature and ice and wind loadings and the wire is Subject to a great range of vibration caused by wind gusts aril vibration front trains or other heavy vehicles transmitted through the earth. High frequency low-amplitude vibrations are sometimes audible as singing in the wire. The other extreme is the vertical slashing or dancing of the wire observed during severe storms where amplitudes of 9, ft. or more at low frequencies have been observed.

Jan 1, 1942

Accessions AMERICAN ELECTROCHEMICAL SOCIETY, TRANSACTIONS, vol. 33. Bethlehem, Pa. 1918. AMERICAN ASSOCIATION OF PETROLEUM GEOLOGISTS, BULLETIN, vol. 2. 1918. (Gift of the Association.) AMERICAN YEAR BOOK: 1915. Edit by Francis G. Wickware, New York. 1919. (Gift of D. Appleton & Co.) ANNUAIRE DE LA HOUILLE BLANCHE FRANCAISE. ` By M. Auguste Pawlowski. 2d year. 1918-1919. Paris. (Gift.) BLACK DIAMOND, Vol. 60, Jan.-June, 1918; vol. 61, July-Dec., .1918. (Gift.) Chicago. CANADIAN MINING INSTITUTE, TRANSACTIONS, vol. 21. 1918. Montreal, Quebec. COMPTES-RENDUS DE L'ATHÉNÉE LOUISIANAIS, vol. 4, No. 3. (Gift of Wm. Beer.) EFFICIENCY OF NATURAL GAS AT Low PRESSURES. Abst. of testimony of Samuel S. Wyer before the Corporation Commission of Oklahoma, February 4, 1919. Printed by Empire Gas & Fuel Co., Kansas City, Mo. GEOLOGICAL. INSTITUTION OF THE UNIVERSITY OF UPSALA, BULLETIN. Edit. By Hj. Sjögren. vol. 14, 1917; vol. 15, 1916; vol. 13, pt. 2, 1916. (Gift.) HYDROGENATION OF OILS. Catalyzers and catalysis and the generation of hydrogen and oxygen. By Carleton Ellis. 2d edition. New York. 1919. (Purchase.) INSTITUTE OF METALS, JOURNAL, vol. 26. No. 2. Edited by G. Shaw Scott. London. 1918.

Jan 6, 1919

J. J. MCLELLAN, Webb City, Mo.-The Media mill, at the time it was built, was the largest mill that had been designed in the Joplin district. It was put up in a hurry, to take advantage of the high prices for zinc ore in 1915, by the owners of an adjacent plant, which had been very profitable. They owned a compound Corliss engine, and to take advantage of a single-unit drive it was necessary to build the mill in the form chosen, which involved making the hopper feed directly through the breakers and rolls, the undersize from the screen passing at once to the jigs, the oversize going through the rolls and returning to the original trommels. The mill was built in fairly good proportion; crushing was done by jaw breakers, Webb City pattern,' and three sets of 42-in. (106.7-cm.) Cornish rolls for reducing the oversize. The jigs were larger than the usual practice. The roughers were two six-cell jigs, with 42 by 48-in. cells. The cleaner jig was the largest ever constructed in the district up to that time, having seven 36 by 48-in. cells, for treating the rougher jigs. There was also a chat rougher. "Smittem," as used in our district, is the partly concentrated product from the rougher, which is finished on the cleaner jigs. "Chats" are the middlings proper, that is, they are the grains of chert with included particles of sulphide; the very low-grade smittem is sometimes included among the chats. When drawing chats from a jig, we also draw about ten times greater quantity of barren chert in order to insure complete recovery of mineral. This mixture of middlings and tailings is taken to a set of 30-in. rolls, the crushed product then going to a chat rougher, a comparatively small jig, with 26 by 36-in. cells. The principal departure of the Media mill from the usual practice was to build a hopper sufficiently high to give gravity feed to the jigs, without using elevators. The sludge plant, for table treatment of sand and slime, also contained several innovations in the manner of distributing the feed. The tables were arranged in two rows and the feed ran around the outside in a launder having two or three cone classifiers

Jan 1, 1918