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By Arthur Taggart

Recent jig practice has shown such marked departures from the pronouncements of the textbooks, particularly as to particle size recovered and size range of feed, as to make it desirable to reexamine the mechanism of jig action. This paper presents the results of such a study. The general conclusions of the Paper are: I. A jig bed is a bi-functioned as well as bi-parted body. The upper layer comprises a plastic stream moving slowly in a substantially horizontal direction from feed lip to tail board. It serves to rough out tailing and light middling and to pick up heavy middling and lift it out 01 the jig box. The lower layer acts as the ultimate separating means by absorbing concentrate and rejecting heavy middling. 2. The separating function of the lower layer is performed in three definitely diflerent ways, depending upon the relative sizes of the grains presented to it and those composing it. Experimental The experimental work consisted of close and long-continued visual observations of operating beds in a plunger jig, eccentric driven, and in determinations of the settling rates of various metal spheres through a quartz bed under various conditions of operation. Falling velocities were measured by an ingenious method devised by A. 6. Dorenfeld, a student in the Mining Department at Colum- bia. Spheres of different metallic alloys, 3/8-in. diameter, were cast with a short piece of fine copper wire frozen in to Serve for suspension-A short piece of black cotton thread was looped to the top of the wire to serve as an indicator. The set-up for a test is shown in Fig. I. The thread should be boiled, if necessary, to make it freely water absorbent. The piece of clean plate glass D is supported rigidly at the proper height in a vertical position. The white scale E is similarly supported behind the glass. At the beginning of a test, D is filmed with water by holding it (best with clean rubber finger cots) under running tap water. It is then clamped in approximate position and C, already wet, is laid across it and drawn straight and vertical with the upper end at or near the top of D, and the ball A slightly above the top of the expanded bed. The water film holds the string to the glass. For a test the string is released, its upper end position noted just after the top of the ball becomes submerged, when the corresponding time is read, and thereafter simultaneous readings of position and time are taken as desired. Results of the visual studies of the bed are given at the pertinent places in the following discussion. Results of the settling tests are summarized in Figs- 2 and 3. Definitions The name bed as used herein refers to the entire mixture of solids and water filling the jig box. A layer is a stratum of a bed composed of particles of substantially the same specific gravities. A granular product is long-range when it approximates a crushed or ground product limited as to upper size only; a short-rafzge product is one closely sized. A bed is loaded when operating with continuous feed and discharge of products; it is unloaded when pulsating norma11y but neither being fed nor

Jan 1, 1943

By Ted C. Briggs

Nitrogen exists in two broad categories commonly designated as elemental nitrogen and fixed nitrogen. Elemental nitrogen is found in nature as a diatomic molecule and constitutes about 78%, by volume, of the earth's atmosphere. Fixed nitrogen is a common term used for nitrogen that is chemically bound to other elements. Although elemental nitrogen is very abundant, nonleguminous plants cannot utilize nitrogen unless it is in the chemically combined form. The content of this chapter is confined to fixed nitrogen since the uses and properties of elemental nitrogen and the fixed nitrogen compounds are different. Bacteria associated with legumes are able to fix atmospheric nitrogen, but not to the extent or in the locations required by modem agriculture. The need to use fertilizers containing fixed nitrogen compounds to grow food crops has been recognized for hundreds of years, and from antiquity farmers have used organic wastes such as animal manures, vegetable wastes, sewage sludge, fish scraps, etc., containing these compounds for fertilizers. The organic materials have a low nitrogen content, however, and cannot support large-scale food production. Known commercial-size deposits of natural nitrates containing much higher nitrogen content exist only in Chile, and the possibility of the discovery of other significant deposits is remote. The Chilean deposits were the major source of nitrogenous fertilizers until about 1913, when the Haber-Bosch process for the production of synthetic ammonia was developed. In the Haber-Bosch process, nitrogen reacts with hydrogen, at high temperatures and pressures and in the presence of a catalyst, to form ammonia. At present Chile is the only country in the world with a nitrate mining industry, and, although the mining of natural nitrates is an important industry in Chile, natural nitrates are relatively unimportant, worldwide, because of the adoption of fixed nitrogen processes. The relative amount of the world demand for fixed nitrogen that is derived from natural nitrates has declined in recent years and will continue to decline. Modern farmers are sophisticated in economic calculations such as cost to benefit ratios and, for the most part, they purchase plant nutrients which give the highest return on their investment. Natural nitrates cannot compete on a fixed-nitrogen cost basis with anhydrous ammonia and its derivative products. In a limited sense, the fixed nitrogen industry is mining the air. Modern plants use air, water, and, in most cases, natural gas to produce the ammonia that is now the key building block of the fixed nitrogen industry. To present an accurate picture of the industry, this chapter on nitrogen follows a format somewhat different from that of other chapters in this volume.

Jan 1, 1975

By William R. Barton

It is generally conceded as axiomatic that the aggregate producer and the average urban resident have mutually incompatible goals. The producer wants to be near his mass market and the average resident wants him as far away as possible. The traditional economic decision to mine local material to avoid transportation costs is increasingly challenged by zoning and planning bodies and by citizens' groups. This conflict generated much written and spoken word and offered opportunity for great flights of rhetoric. The pressure on the producer also has forced re¬appraisal of the need for the classic confrontation with indications that much of the conflict is more apparent than substantive. In New England several factors combine to increase complexity of the siting problem. It is a region of high land values and population density. Due to the proximity of metropolitan areas, even rural communities have experienced a prolif¬eration of environmental groups with concomitant enthusiastic regional planning and critical watch over land use. In New England where there is little public understanding of the necessity for, and the realities of, mineral production a sophisticated approach to aggregate production site location is required.

Jan 1, 1975

By J. D. Livingston, H. E. Cline

Cu-Pb alloys in the vicinity of the monotectic composition have been directionally solidified under a high temperature gradient at rates up to 2 X l0-' cm per sec. Over a wide range of compositions, high growth rates yield a composite structure consisting of continuous rods of lead in a copper matrix. This range of compositions increases with increasing growth rate, in agreement with arguments based on the relative velocities of composite growth and the growth of copper dendrites or lead drops. The breakdown of the composite structure at slow growth rates is explained in terms of the relative interphase surface energies. The observed interrod spacings of the composite structure are large compared with the predictions of the Jackson-Hunt equations of eutectic growth. ThE directional solidification of many eutectic alloys produces fine composite structures of parallel lamellae or rods. There has been considerable interest not only in the fundamentals of this two-phase solidification process,'-3 but also in the interesting physical properties produced by such regular and aniso-tropic microstructures. Composite structures can be grown only over a limited range of composition, beyond which coarse primary dendrites of one phase appear. In organic eutec-tics, this composition range of composite structures has been shown to increase with increasing growth rate.7"10 These results were explained in terms of the relative velocities of composite (coupled) growth and dendritic growth. Although similar arguments should apply to metallic eutectics,11-13 suitable experimental results are lacking. In contrast to the work on eutectics, the directional solidification of monotectic alloys has received little attention. (The monotectic reaction is similar to the eutectic reaction, except that one of the resulting phases is a liquid, which subsequently solidifies in a separate reaction at a lower temperature.) Directional solidification of some monotectic alloys'4715 yields regular rodlike microstructures, whereas in other cases macroscopic separation of solid and liquid phases occurs.16 chadwick17 rationalized these results in terms of the probable relative magnitudes of the various interphase surface energies. A recent study of chill-cast Cu-Pb alloys18 revealed a fine rodlike microstructure in alloys near the monotectic composition. It was decided to investigate the directional solidification of such alloys, and to determine the range of composition and growth conditions yielding composite structures. The Cu-Pb system is convenient for such a study, both because it is simple metallurgically, with no compound formation and negligible solid solubilities, and because its basic properties are well-documented. Recent literature on the Cu-Pb system includes studies of bulk thermo-dynamic properties,'g surface energies,20"21 densi-ties,25 and diffusion constants.a6 A similar study of the directional solidification of Cu-Pb alloys was recently undertaken, independently, by Kamio and Oya." EXPERIMENTAL Alloys were prepared by melting 99.999 pct Cu and 99.999 pct Pb in a graphite crucible, stirring well, and pouring into a cold graphite mold. Rods 0.175 in. in diam were machined from the ingots. Alloy compositions studied ranged from 25 to 55 wt pct Pb. Samples were placed in graphite crucibles 5 in. long with 4 in. OD and 0.035-in. walls. They were melted under flowing argon in a vertical, two-zone. platinum -wound furnace. A voltage stabilizer was used to minimize fluctuations in input power. The narrow specimen diameter minimized convection. Directional solidification was achieved by driving the crucible downward into a +-in. hole in a water-cooled copper toroid. The toroid was located immediately below the narrow end zone of the furnace. The end zone was separately powered to maintain high local temperature. Therefore a high temperature gradient (approximately 300 deg per cm) was maintained in the specimen throughout the run. The crucible motion was screw-driven. and a wide range of drive speeds were available. The limited rate of heat removal caused a thermal lag in the specimens at high drive rates. However. temperature-time curves from thermocouples imbedded in a representative sample indicated that the average growth rate still approximately equaled the drive rate. Although the specimens were initially homogeneous, melting and re solidification redistributed the lead. producing composition variations of several percent along the specimen length. (During melting. lead melted first and ran down the sample surface. Rapid freezing tended to reproduce the resulting composition gr~dient, but slow freezing did not because a slow-moving interface tended to reject lead. as discussed later.) To determine local composition. ;-g samples were cut from regions exhibiting various microstructures and were chemically analyzed for lead content. Micrographs were taken on as-polished or lightly etched surfaces. Three-dimensional structure of the lead network was viewed with a scanning electron microscope after removal of some of the copper matrix with nitric acid. RESULTS Several different microstructures are observed, depending on composition and drive rate. Because melting and resolidification produced composition gradients, results are best presented in t&ms of final local composition, rather than initial or average composition. The ranges of local compositions and drive

Jan 1, 1970

By W.C Ellis, Earle E. Schumacher

Nonferrous alloys upon which desirable properties can be conferred by heat treatment are becoming of increasing industrial importance. The alloys of copper with a constituent which has a solubility varying with temperature are materials of this character. Some of the constituents which are effective in producing a change in the mechanical properties of these alloys upon heat treatment are, according to Corson,' nickel and silicon, iron and silicon, cobalt and silicon, and chromium and silicon. In addition to these elements, Gregg2 states that the combination of beryllium and silicon is effective in producing age-hardening characteristics in copper. The effect of these elements, however, as dispersion-hardening constituents in the copper alpha solid solutions does not seem to have been studied in any considerable detail. This paper deals with the heat treatment and properties of three alpha brasses containing 3 per cent. of nickel plus silicon in the proportion necessary to form the compound nickel silicide, Ni2Si. Some information of a preliminary nature in regard to the hardening by heat treatment of phosphor bronze containing the same percentages of nickel and silicon is included. The method of hardening the alloys, which is effective in increasing the tensile strength and proportional limit, is similar to that used in the case of duralumin type aluminum alloys. It consists of a quench from a temperature at which the hardening constituent is in solid solution, followed by an aging at a lower temperature to precipitate the dissolved constituent in a dispersed condition. This results in an increased resistance of the alloy to deformation with an attendant improvement in the tensile properties.

Jan 1, 1929

By Earle E. Schumacher, W. C. Ellis

Nonferrous alloys upon which desirable properties can be conferred by heat treatment are becoming of increasing industrial importance. The alloys of copper with a constituent which has a solubility varying with temperature are materials of this character. Some of the constituents which are effective in producing a change in the mechanical properties of these alloys upon heat treatment are, according to Corson,' nickel and silicon, iron and silicon, cobalt and silicon, and chromium and silicon. In addition to these elements, Gregg2 states that the combination of beryllium and silicon is effective in producing age-hardening characteristics in copper. The effect of these elements, however, as dispersion-hardening constituents in the copper alpha solid solutions does not seem to have been studied in any considerable detail. This paper deals with the heat treatment and properties of three alpha brasses containing 3 per cent. of nickel plus silicon in the proportion necessary to form the compound nickel silicide, Ni2Si. Some information of a preliminary nature in regard to the hardening by heat treatment of phosphor bronze containing the same percentages of nickel and silicon is included. The method of hardening the alloys, which is effective in increasing the tensile strength and proportional limit, is similar to that used in the case of duralumin type aluminum alloys. It consists of a quench from a temperature at which the hardening constituent is in solid solution, followed by an aging at a lower temperature to precipitate the dissolved constituent in a dispersed condition. This results in an increased resistance of the alloy to deformation with an attendant improvement in the tensile properties.

Jan 1, 1929

By T. K. Perkins, L. E. Bartlett

Values of rock surface energy (i. e. energy required to form a unit area of new surface) are useful for interpretation of drilling and fracturing phenonema This paper describes the adaptation of a cleavage technique (splitting of large rocks under controlled conditions) for measuring surface energies. Values of surface energy obtained at room temperature and at low crack extension rates are reported for a variety of sandstones and limestones. Elastic moduli, tensile strengths and compressive strengths of the samples are also reported. The values of Young's moduli (measured in bending) are relatively low, probably because of the low stress levels imposed. Measured values of surface energy me generally higher than anticipated and probably reflect inelastic yielding near the extending tip of the crack. INTRODUCTION The technology of petroleum production includes many operations such as drilling and fracturing, which involve rock breakage. One of the fundamental properties of a rock needed to fully explain breaking and fracturing phenomena is the surface energy (i. e. the energy required to form a unit area of new surface). In this paper we describe an adaptation of the cleavage method (splitting of the rock under controlled conditions) to utilize large rock samples. Application of the theory of elastic cantilever beams and the Griffith concept of mechanical stability permits the calculation of surface energies from simple measurements. Values of surface energies obtained at room temperature on dry samples and at low crack extension rates are reported for a variety of sandstones and limestones. Measured values of Young's Moduli, compressive strengths and tensile strengths are also reported for the rocks. THE EXPERIMENTAL METHOD Equipment designed to cleave large rock samples is shown on Fig. 1. This equipment consists essentially of two steel blocks cemented to a rock sample and forced apart with a steel rod. A ball joint and a pivot prevent bending stresses in the rod. A differential thread arrangement permits the rod to advance only 0.012 in./revolution of the driving nut. The axial force in the rod is measured with type FA-50-12 Baldwin Lima Hamilton strain gauges and a BLH type 20 strain gauge reader. Separation of the blocks is measured with a Starrett 656617 dial gauge. The massive nature and design of the equipment minimize the amount of elastic energy stored in the steel parts as the stress in the rod is increased. This will permit the rock to split under controlled conditions as will become clear later. Fig. 2 shows a sketch of the rock sample during cleavage. Guide slots are cut longitudinally along the rock sample as suggested by Berry.1 An initiating slot is also cut across the top of the block to a depth of 1 to 2 in. During cleavage, elastic energy is stored in the flexed beams of rock of length C. If the length of steel rod L is held constant and the crack extends in length, then the elastic potential energy stored in the rock decreases. However, surface energy must be supplied as the crack extends in length. Griffith6 has proposed the following criteria for mechanical stability. The crack will extend as long as the potential energy available is greater than the surface energy required. However, the crack will stop extending when the change in potential energy with change in crack length is just equal to the change in surface energy with change in crack length. See Eq. 1.

By James C. Ray

The age classification of the mineralized veins of the Butte district, as given by Weed and Sales, was tacitly accepted for many years. Weed, whose field work was completed in 1906, divided the copper veins into groups of four ages.' In 1913, Sales modified Weed's classification and assigned all mineralized veins (including the silver-zinc veins of the border or "peripheral" zones) to three periods of fracturing and mineralization. Both writers based their classifications mainly on the relative ages of the observable faulting whereby the veins of a so-called "earlier" system are intersected and offset by those of a "later" system. Nevertheless they possess structural and mineralogical characteristics in common which indicate that they are of the same age. The writer has maintained since 19143 that these vein systems were formed during one general period of mineralization along a network of intersecting fractures of approximately simultaneous origin and that the existing offsets are largely due to postmineral faulting. Leith,* takes cognizance of the accumulating mass of data relative to the simultaneous formation of intersecting fracture systems and says, referring to ~utte: "It now appears that the mineralization accompanying them (individual structure systems into which the veins have been grouped) is substantially of one period, indicating that the successive structural movements took place mainly within the period of mineralization." This paper presents the results of certain structural experiments which suggest a modified interpretation of the published data on the Butte district. The interpretation is substantiated by the writer's observations in the Butte mines and is offered with the hope that it will reconcile the structural with the mineralogical conditions existing in this most interesting district; also, that it will emphasize the importance of a

Jan 1, 1931

The Raymond Memorial Volume, which the Members of the In-stitute have been so anxiously awaiting since the beloved man's death, is nearly ready for publication. It will contain about 45,000 words and some illustrations and a frontispiece portrait. This book promises to fill every expectation of the contributors to the volume and the host of admirers of the genius who so long guided the destiny of the Institute. It will contain one of Doctor Raymond's best stories, entitled "James and Jim;" his famous article on "Job on Mining;" and one of his poems entitled "The Grand Canyon." A biography of Doctor Raymond has been written by his daughter, who is the wife of a member of the Institute. The memorial addresses delivered by Dr. Henry F. Drinker and T. A. Rickard at the annual meeting in New York in 1919 will be included. There will also be very interesting reminiscences by H. M. Howe, A. S. Dwight, C. W. Goodale, R. W. Hunt, Lyman Abbott, J. F. hemp, T. A. Rickard. The volume has been edited by T. A. Rickard, which promises all that can be wished for the volume from a literary standpoint. The edition will he limited so that it is very desirable that orders for this volume be sent in to the Institute as promptly as possible. The price will be $5.00.

Jan 12, 1919

By H. P. Greenwald

IN the year just passed the Coal Division's Committee on Rock-Dusting reviewed the status of this safety measure in American coal mines and prepared a paper thereon which will be presented at the February meeting of the Institute. This paper supplements one appearing in Vol. 139 of the "Transactions," page 87 (1940). Because that paper will be issued soon, only a summary is given herein.

Jan 1, 1944

By John H. Holloman

In recent papers, O'Neill,' Vivian, and Zener and Hollomon3 have reviewed some of the information concerning the relations between stress and strain during plastic deformation. Since further information has been obtained since these reviews were published, this paper attempts to further coordinate and amplify the knowledge concerning the plastic deformation of metals in simple tension. Ordinarily the results of tensile tests of metals are presented as graphs in which the load divided by the original area is plotted as a function of the percentage of elongation measured over some specified gauge length. The interpretation of graphs of this sort is limited, since the stress required to deform the metal at any stage of the deformation is actually the load divided by the instantaneous rather than the original area. Furthermore, each increment of the deformation is performed on metal that has been previously deformed, and, as pointed out by Ludwik,4 the strain could be more effectively defined: where e is the strain and AO and A are, respectively, the original and instantaneous areas. The results of the tensile tests can be more effectively presented and interpreted if the stress* (load divided by actual area) is .lotted as a function of the strain as defined above. A schematic curve of this type is presented as Fig. I. In a previous paper,6 the concept of Ludwik7 concerning the flow and fracture of metals was successfully employed to explain some of the puzzling results of notched-bar impact tests of steel. It appears that the use of this concept ii; very fruitful and should be kept in mind in any study of the deformation charactcristics of metals. Ludwik considered that a flow stress-strain curve of a metal was essentially a locus of points that described the stress required for plastic flow of an infinite numbcr of specimens, each with a different strain history determined by the preceding part of the flow curve Each of these specimens can also be considered to have a fracture strength. Uniortunately (or fortunately depending upon the point of view), all the specimens, except the one deformed to the fracture strain, flow and do not fracture. Even though the metals do not fracture, the concept of a fracture-strength curve seems

Jan 1, 1945

By C. L. Mantell

ALTHOUGH SO common and well known a metal, tin is really a less abundant element than many of those less familiar and usually ranked with the scarce or rare elements, such as cerium, yttrium, lithium, beryllium., titanium, zirconium and vanadium. The color of tin is white, with a slightly bluish tinge. When it is compared with nickel, the latter metal is brown. When placed alongside of tin, chromium is definitely blue. Tin is whiter than silver or zinc. Exceedingly thin films of tin show various shades of brown by transmitted light. The metal has a brilliant luster, and when mirror-polished, has high light reflectivity. The luster depends to a large extent upon the pouring temperature at which the metal is cast. If the temperature be, too high, iridescent colors may show on the surface. These are the result of oxide film formation. If the pouring temperature be too low, the surface is dull. Small amounts of foreign metals, such as lead, arsenic, antimony and iron, decrease the luster of tin and impart a yellowish tinge to the metal. The structure is decidedly crystalline. The cast metal is a mass of crystals. When a bar of tin is bent, it emits a characteristic creaking sound. This is called the "cry" of tin, resulting from the grinding of the crystals one against the other during the bending of the metal. Tin metal may lose its crystalline structure by cold working, but grain growth occurs rapidly under the influence of heat. Metal which has been cast at a low temperature may become amorphous as the result of mechanical work. If such material be heated to temperatures well. below the melting point, say at 110° C. for a half hour or for a few minutes at 150° C. recrystallization occurs. If the surface of tinned plate, tin foil, or tin metal in cast form be etched with hydrochloric acid containing a little free chlorine, attack occurs at the intercrystalline faces. The surface shows patterns resembling the frost flowers on window panes in winter. The etched appearance is called moiré metallique. Fine dendritic surface crystals of tin may be obtained by casting the metal on a surface of polished steel. In commercial tin plate, the intercrystalline boundaries are shown by fine grooves or channels, which result from the method

Jan 1, 1929

NEW MEMBERS The following list comprises the names of those persons who became members during the period Sept. 10, 1916, to Oct. 10, 1916. BLOOMFIELD, EDWIN CHARLES, Min. Engr., 1012 Standard Bank Bldg., Vancouver, B. C., Canada. BRINGS, HENRY, Min. and Met. Engr., Chief Engr., and Geol., Mollet-Mesrine, 1212 Mills Bldg., El Paso, Texas. CHASE, MARCH F., Vice-Pres., Commercial Acid Co., 1906 Boatmens Bank Bldg., St. Louis, Mo. CUMMINGS, ALVIN M., Asst. Mine Supt., Witherbee, Sherman & Co., Inc., Mineville, Essex Co., N. Y. DOUGLASS, GEORGE M., Genl. Safety Inspector, Amer. Smelt. & Ref. Co. 120 Broadway, New Fork, N. Y. EMRICH, CLARENCE T., Chief Chemist, Old Dominion Copper Min. & Smelt. Co., Box 1163, Globe, Ariz. GARDANIER, SUTTER ALBERT, Assayer, Mgr., Douglas Assay Co., Douglas, Cochise Co., Ariz.

Jan 10, 1916

By Nelson Severinghaus

Crushed stone leads all industrial mineral, except cement in annual value of production in the United States. It is also interesting to note that crushed stone value is exceeded only by that of fuels, cement, and iron ore among all mineral products of this country. An industry which started with hand-sledging to produce smaller sizes of broken stone for hard surfaced improvement of roadways as designed by McAdam in England about 1815 has grown into a complex industrial giant. Most of this growth started with the invention of a mechanical rock crusher just under one hundred years age (1858) by Eli Whitney Blake. This invention made possible the production of greater tonnages of smaller sizes of broken stone and greatly accelerated its use for Macadam road pavements and for railroad ballast. Stones Used for Crushing All three of the major geologic classifications of stone, sedimentary, igneous, and metamorphic, are widely used in the production of crushed stone. Satisfactory physical and chemical properties can be found in each type so that economic availability becomes the prime determinant for development. Table 1 lists more common rocks of the three main groups with average values of specific gravity and toughness as measured by Deval test. This widely used classification was suggested by C. E. Lord, of U. S. Bureau of Public Roads. The physical properties were compiled by D. O. Woolf in "The Results of Physical Tests of Road Building Rock," U. S. Department of Agriculture, Bulletin 76. It should be noted that the figures given in Table 1 are averages. Very substantial variations in the physical properties of rocks within any one classification will occur. The solid surface of the earth was first made up of igneous rocks resulting from the solidification or crystallization of molten material upon cooling. These igneous rocks were disintegrated into sand, clay, and gravel by the weathering action of wind, water, chemicals, [ ] and temperature changes. The products of weathering were transported by wind and streams until they reached less turbulent areas such as oceans or lakes and were deposited. Chemical deposition between grains of sand or clay or the physical action of pressure and heat then solidified them into sedimentary rocks

Jan 1, 1960

By AIME AIME

THERE is a constant reiteration in some quarters that technical societies are autocratic and that democracy is utterly lacking and that members would welcome democratic societies in which they had full, control of affairs. While we may not speak for other societies, than our own, in so far as th's Institute is concerned such charges- can only come from people uninformed as to the circumstances. It. is no curtailment of the democratic privileges of the members that a -slate is prepared by the Nominating Committee to be voted on at the annual meeting. The Constitution of the, institute stipulates how the nominating committee shall; be chosen and who shall compose it, which prevents anything like- a- clique controlling- the situation. The Constitution further provides how the nominees shall be distributed geographically and the by-laws specify geographical boundaries: for-these nomination districts. Further more, any man or complete ticket can be placed in nomination by means of a petition signed-by only; twenty-five members,- and three or four times such an independent slate has been so nominated and elected.

Jan 1, 1920

Elected Died 1895 ABBOTT, AI ATTHUR 1908 1882 ABBOTT, ARTHUR V 1906 1905 ABE, MASAYOSHI 1909 1903 ADAMS, CHARLES C. 1905 1906 ADAMS, JOHN C. 1913 1905 ADAMS, WILLAMS 1909 1903 ADAMS, W. EDWARDS 1910 1884 ADDY, MATTHEW 1896 1906 AFFLECK, WILLIAM A. 1911 1889 AKERS, WILLIAMS A. 1906 1905 ALABASTER, RUPPERT C. 1911 1899 ALBERGER, LOUIS R. 1911 1894 ALLEN R B 1896 1905 ALLEN, R. SCOTT 1906 1886 ALLISON, ROBERT 1916 1874 AMIOT, H. 1892 1886 AMSLER, CARL 1894 1898 ANDRSON, JOHN W 1905 1895 ÅNGSTROM, CARL 1901 1887 ARCHBALD, JAMES 1910 1900 ARLETT, GEORGE H 1906 1895 ARMSTRONG, JOHN F 1898 1905 ARNOLDS, LEO F. 1917 1882 ARNOLDS, HUGO 1886 1875 ASHBURNER, CHARLES A 1889 1872 ASIIBURNER, WILLIAM 1887 1883 ATKINS, C M , JR 1885

Jan 1, 1923

By C. Chiou, M. E. Fine

While Gunier-Preston zones are growing in Al-4.2 pct Cu at room temperature, Young's modulus, measured dynamically, increases about 0.4 pct. From the change in modulus with time the exponent of time in the rate equation for growth of the zones was deduced to be %. From a comparison of the rates of increase of modulus at 1, 28, and 42°C an activation energy of 12 to 14 Kcal per mole is computed. These findings support the idea that copper atoms are supplied along dislocation channels to growing zones. In alloys the elastic constants will be functions of the distributions of the atoms. If the degree of ordering or clustering is changed, one expects a corresponding change in the elastic constants. During age-hardening of aluminum-copper alloys at room temperature, the copper atoms cluster on 100-type planes in the aluminum lattice forming

Jan 1, 1959

By A. M. Talbot, John T. Norton

TheRe is still considerable controversy as to the exact nature of the mechanism of the age-hardening process, in spite of the many experiments already performed. For this reason, a considerable number of typical systems should be examined in detail and their results correlated. Furthermore, the methods of studying the changes that take place during the progress of this phenomenon should be carefully scrutinized and the different methods applied to the same samples, preferably at the same time. The experiments described in this paper are presented to supply information on one age-hardening system and to show how the various methods of investigation compare in their indication of what has happened. In brief, the progress of aging in magnesium alloys containing about 10 per cent by weight of aluminum at different temperatures was followed by measurements of hardness, electrical resistivity, dilation and lattice parameter, and by microscopic observation. Previous Work Meissnerl,$ Archer?, and Gann3 have investigated the changes in mechanical properties of magnesium-aluminum alloys during aging and have shown the optimum condition for the age-hardening treatment. Meissner's results are particularly interesting because when replotted so that they represent hardness as a function of aging time, the curves of 125" and 150" C. show two hardness peaks. This result was not confirmed in the present work. Schmid and Siebe14 have reported an investigation that is similar to the present one but it was not published until the present work had

Jan 1, 1936

GENTLEMEN Submitted herewith are the report of the Treasurer for the year 1938 and reports for the same year of the following standing committees: Admissions, Membership, Papers and Publications, Mining and Metal¬lurgy (Magazine), Library, Speakers for Local Sections and Student Societies, and Student Relations. To these reports members are referred for further details. Membership.-The end of the year 1938 saw Institute membership at an all-time peak: 12,474, made up of 2898 Student Associates and 9576 members of other classifications. The next highest level had been reached at the end of 1921 when corresponding figures were: total, 10,329; student members, 1450; all other classifications, 8879. The net gain for the year was 1495, of which 751 were Student Associates and 744 in the other categories. Two factors contribute to the growth of membership: (1) the enrolment of new members; and (2) the retention of members already on the roll as reflected in a relatively small number of resignations and suspensions for nonpayment of dues. For the first, much credit goes properly to the general Membership Committee that functioned for a second year under the chairmanship of Clyde E. Williams. With the cooperation of Institute members in general, to whom Mr. Williams expresses appreciation in his report, the Committee has been successful in acquainting eligible nonmembers with the purposes, activities and advantages of the Institute. The result has been the receipt during the year of 1162 applications, exclusive of Student Associates. This compares with 1212 during 1937 and 1266 during 1936. However, in considering this modest decline, account must be taken of the somewhat less prosperous conditions prevailing in the mineral industries and, consequently, among engineers engaged ?in those industries.

Jan 1, 1939

By FORTUNATO PEREIRA

(San Francisco Meeting, October, 1911.) I. GENERAL DESCRIPTION. The Department of Narino (formerly included in the Department of Cauca) is a narrow band about 170 km. (100 miles) wide in the southern part of the Republic of Colombia, FIG. 1.-SKETCH-MAP OF THE SOUTHWESTERN PART OF COLOMBIA. near the boundary of Ecuador, as shown in the sketch-map, Fig. 1. Its capital is Pasto, a small city of 25,000 inhabitants; the principal towns are Túquerres, Cumbal, Ypiales, Barbacoas, and Tumaco. The port on the Pacific ocean is Tumaco, and traffic in the interior is carried partly on the Patia river (steam navigation to the fluvial port of Barbacoas), and afterwards overland over poor roads by human bearers or on mule-back.

Aug 1, 1912