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By Charles Clayton

IN connection with certain coöperative work carried on between the Ordnance Department of the U. S. Army, the U. S. Bureau of Mines, and the U. S. Geological Survey during the year 1918, it was the writers' privilege to make metallographic examinations of a great many test bars and other pieces of nickel-steel gun forgings. The material studied came from many different steel plants throughout the country and consisted both of forgings that had been accepted by the Ordnance Department and those that had failed to pass the specified physical tests. In general, these tests require a minimum tensile strength of 95,000 lb. (42,091 kg.), an elastic limit of 65,000 lb. (29,483 kg.), an 18 per cent. elongation, and a 30 per cent. reduction in area. An average chemical composition of the steel studied is 0.38 per cent. carbon and 2.9 per cent. nickel. The steel was of both basic electric and basic open-hearth manufacture. The object of the metallographic work was two-fold: to assist in detecting defects in the steel and, if possible, to suggest remedies for the same; and to obtain as much information as possible in regard to the relation of the microstructure of the metal to its physical properties. The greater part of the investigation was devoted to defective metal that failed to pass the ordnance specifications. Many types and kinds of more or less serious defects thus came under observation, but most of these were due to the attempts by the manufacturer to meet the enormous demand for ordnance steel with more or less inadequate equipment, and were soon remedied. Two defects, the so-called "flakes" or "snowflakes" and a certain "fibrous" or "woody" fracture, were encountered so frequently and were so disastrous to the steel that the greater part of the study was devoted to them. As a result much information as to their nature and their effects

Jan 2, 1919

By C. S. Smith, L. W. Kempf, C. S. Taylor

The thermal conductivity of aluminum alloys is of considerable industrial importance. This is particularly true in such applications as internal-combustion engines where one of the principal reasons for the use of these alloys is their relatively higher thermal conductivity. In spite of this, relatively few data are available on this property of aluminum alloys. The reason is quite apparent to anyone concerned with the experimental determination of coefficients of thermal conductivity. This determination, in theory so simple, is extraordinarily difficult if any high degree of precision is desired. Fortunately, some .knowledge of the relationship between thermal and electrical conductivity has permitted the use of the latter physical property in deducing the relative approximate values of the thermal conductivities of metals. This fundamental relationship, first enunciated by Wiedemann and Franz' as applying to metallic elements and later shown by Lorenz2 to be applicable to alloys within a single metallic system, has been of service in the industrial application of metals. The electrical conductivity of metals is easily determined with a high degree of precision. It is, therefore, quite desirable that the relationship between electrical and thermal characteristics be determined with the greatest possible precision. This paper presents data on the electrical and thermal conductivities of a number of aluminum alloys of industrial importance. Literature on Thermal Conductivity of Aluminum Alloys Masumoto3 determined the electrical and thermal conductivities of 18 aluminum alloys. His results indicated a relatively constant relationship between thermal and electrical conductivity.

Jan 1, 1937

By R. E. Ricksecker, W. M. Baldwin, R. McC. Baker

INTRODUCTION THE development of residual stress in strip during rolling has not been systematically studied. A few scattered papers1-3 mention the existence of residual stresses in rolled strip or touch upon some of their consequences,4 but there is no report of experimental studies in the literature describing the effect of roll diameter, strip thickness, reduction per pass, metal or metal temper on the magnitude of residual stresses developed in strip. A knowledge of the effect of these factors is of utmost importance since the present trend in some mills to roll thicker castings brings the rolling operation directly into that set of conditions which, as will be brought out in the present paper, can develop residual stresses of a high order of magnitude. Fundamentally, residual stresses are developed when a metal is inhomogeneously unloaded from a plastic stress state. A quantitative treatment of the problem requires a reasonably complete understanding of both the plastic stress state existing in the metal during deformation and the elastic stress state that would exist in the metal if the metal deformed as a perfectly elastic body. Our knowledge of either state during rolling is so meager that we can make no more than certain limited predictions. The external stress state* operating between the roll and the metal consists of compressive stresses acting almost perpendicularly to the strip surface but vary [ ] ing in intensity both across the width of the strip and along the length of contact between the roll and the strip. An example of such a stress distribution is shown in Fig I. The nature of the internal stress state, produced by this distribution, is not known. Various investigators,5-7 however, have felt that a qualitative similarity must exist between the internal stress state so produced and that produced in a wide strip that is compressed between two flat-nosed punches. In the latter case the external stress state is represented by a uniformly distributed compressive stress acting perpendicularly over the face of the tool. The elastic internal stress state in this case is complex-the principal stresses showing

Jan 1, 1948

By L. D. Godshall

The latest revised edition of Mr. C. A. stetefeldt's book on the Lixiviation of Silver-Ores, which appeared very recently, contains no mention of the volatilization of silver in chloridizing-roasting—an omission which is the more remarkable in view of the fact that in former editions of the work this important subject was noticed. Moreover, Mr. Stetefeldt has discussed it to some extent in his paper on " The Stetefeldt Furnace," * in which he criticised certain statements made by me before the Colorado Scientific Society in May, 1893, in a paper entitled " A Review of the Russell Process;" ? and Mr. Morse, in his paper on " The Lixiviation of Silver-Ores by the Russell Process at Aspen, Colorado," $ has given statistics showing the loss of silver by volatilization (including the dustloss, which Mr. Morse estimates at not more than 1 per cent.) on more than 30,000 tons of ore roasted, to have been 9.16 per cent. The matter must certainly be deemed important enough to warrant me in returning to it, and offering, with the aid of the figures made public since my first paper, a reply to the criticisms of Mr. Stetefeldt. The passages of my paper which he deemed to be " ques-

Jan 1, 1897

By Joseph C. Kieffer

The Duquesne property of the Callahan Zinc-Lead Co. is about 20 miles east of Nogales, in southern Arizona. One mine is near the mill, but most of the mill feed is hauled in by truck from a number of small mines. The same sulphides are found in all the ores, in general, but the amounts vary considerably. All ores contain silver, copper, lead and zinc minerals but one mine ships ore high in silver and lead and low in copper and zinc; while another mine ships ore high in copper and zinc, and low in silver and lead. The common sulphides are galena, carrying most of the silver; chalcopyrite; sphalerite, carrying iron in solid solution; and pyrite, in a gangue consisting of limestone, quartz and garnet. Mineralization is fairly coarse. At the present grind of about 66 per cent minus 200 mesh most of the sulphides are liberated A small amount of chalcopyrite is locked up with the sphalerite and cannot be liberated at an economic grind, and the copper carried into the zinc concentrate with the sphalerite accounts for the comparatively poor recovery of copper in the copper-lead concentrate. Production oF Two Concentrates The milling problem, which was complicated by the extreme variation in the grade of the feed, was first attacked with the idea of producing a silver-copper-lead con- centrate and a zinc concentrate, both with satisfactory grades and recoveries. By February 1941, it was felt that these objectives had been attained, when the grades of the various products and the recoveries were as shown in Table I. A rough outline of the flowsheet and reagents used is as follows: Minus ¾-in. feed to a 7-ft. by 36-in. Hardinge ball mill working in closed circuit with a 36-in. Wemco classifier. The classifier overflow passes to the second cell of an 8-cell bank of No. 18 Special Denver Sub-A flotation machines (volume, 22.5 cu. ft. per cell). A rougher concentrate is removed from the second to the fifth cells inclusive, and returned to the first cell, which is the cleaner. A scavenger concentrate is removed from the sixth, seventh, and eighth cells, and returned to the third cell. Consump-

Jan 1, 1943

By Joseph C. Kieffer

The Duquesne property of the Callahan Zinc-Lead Co. is about 20 miles east of Nogales, in southern Arizona. One mine is near the mill, but most of the mill feed is hauled in by truck from a number of small mines. The same sulphides are found in all the ores, in general, but the amounts vary considerably. All ores contain silver, copper, lead and zinc minerals but one mine ships ore high in silver and lead and low in copper and zinc; while another mine ships ore high in copper and zinc, and low in silver and lead. The common sulphides are galena, carrying most of the silver; chalcopyrite; sphalerite, carrying iron in solid solution; and pyrite, in a gangue consisting of limestone, quartz and garnet. Mineralization is fairly coarse. At the present grind of about 66 per cent minus 200 mesh most of the sulphides are liberated A small amount of chalcopyrite is locked up with the sphalerite and cannot be liberated at an economic grind, and the copper carried into the zinc concentrate with the sphalerite accounts for the comparatively poor recovery of copper in the copper-lead concentrate. Production oF Two Concentrates The milling problem, which was complicated by the extreme variation in the grade of the feed, was first attacked with the idea of producing a silver-copper-lead con- centrate and a zinc concentrate, both with satisfactory grades and recoveries. By February 1941, it was felt that these objectives had been attained, when the grades of the various products and the recoveries were as shown in Table I. A rough outline of the flowsheet and reagents used is as follows: Minus ¾-in. feed to a 7-ft. by 36-in. Hardinge ball mill working in closed circuit with a 36-in. Wemco classifier. The classifier overflow passes to the second cell of an 8-cell bank of No. 18 Special Denver Sub-A flotation machines (volume, 22.5 cu. ft. per cell). A rougher concentrate is removed from the second to the fifth cells inclusive, and returned to the first cell, which is the cleaner. A scavenger concentrate is removed from the sixth, seventh, and eighth cells, and returned to the third cell. Consump-

Jan 1, 1943

By Joseph C. Kieffer

THE Duquesne property of the Callahan Zinc-Lead Co. is about 20 miles east of Nogales, in southern Arizona. One mine is near the mill, but most of the mill feed is hauled in by truck from a number of small mines. The same sulphides are found in all the ores, in general, but the amounts vary considerably. All ores contain silver, copper, lead and zinc minerals but one mine ships ore high in silver and lead and low in copper and zinc; while another mine ships ore high in copper and zinc, and low in silver and lead. The common sulphides are galena, carrying most of the silver; chalcopyrite; sphalerite, carrying iron in solid solution; and pyrite, in a gangue consisting of limestone, quartz and garnet. Mineralization, is fairly coarse. At the present grind of about 66 per cent minus 200 mesh most of the sulphides are liberated. A small amount of chalcopyrite is locked up with the sphalerite and cannot be liberated at an economic grind, and the copper carried into the zinc concentrate with the sphalerite accounts for the comparatively poor recovery of copper in the copper-lead concentrate. PRODUCTION OF TWO CONCENTRATES The milling problem, which was complicated by the extreme variation in the grade of the feed, was first attacked with the idea of producing a silver-copper-lead concentrate and a zinc concentrate, both with satisfactory grades and recoveries. By February 194I, it was felt that these objectives had been attained, when the grades of the various products and the recoveries were as shown in Table I. [ ] A rough outline of the flowsheet and reagents used is as follows: Minus ¾ -in. feed to a 7-ft. by 36-in. Hardinge ball mill working in closed circuit with a 36-in. Wemco classifier. The classifier overflow passes to the second cell of an 8-cell bank of No. I8 Special Denver Sub-A flotation machines (volume, 22.5 cu. ft. per cell). A rougher concentrate is removed from the second to the fifth cells inclusive, and returned to the first cell, which is the cleaner. A scavenger concentrate is removed from the sixth, seventh, and eighth cells, and returned to the third cell. Consump-

Jan 1, 1942

By W. H. Emmons

MANY mineral veins occupy faults, and movements on certain warped fault planes have resulted in openings. On normal faults the [ ] steeper parts have the widest openings, and on reverse faults the flatter parts have the widest openings. Theoretically the width of the opening is the sine of the angle of deflection times the amount of movement on the fault plane, but actually the widths of some of the openings are probably less because of readjustments of walls along joints or of other readjustments. The first treatment of the subject seems to have been in a book on mineral veins by John Leithart, published in Newcastle, England, in 1838. Later the subject was treated in various texts published in Germany, in England, and elsewhere. The subject was not given much prominence in the earlier American literature on economic geology, but has interested several workers in that field in the past decade. In this paper examples of districts showing ore shoots on warped faults, with relations noted, are described. Fault veins of the three depth classes of veins are noted. Many epithermal veins are in normal faults, and commonly the larger ore shoots are in their steeper portions. Many mesothermal veins are in reverse faults and many others are in normal faults. The flatter parts of veins in reverse faults are commonly wider than the steeper parts, although they are not always as rich as the steeper segments of the veins. There are not many hypothermal veins in faults of measured displacement.

Jan 1, 1943

By James E. York

AT a meeting of the American Society for Testing Materials at Atlantic City, June, 1908, Dr.. C. B. Dudley, in his presidential address,' showed the vital necessity of not only making a steel rail as good as in the past, but of making it considerably better in order to meet the present and prospective require¬ments of railroads. Doctor Dudley requested the co-operation of all who from personal experience could give information that would result in bringing about the production of a steel rail that could be relied upon to meet the present requirements. I have had considerable experience in the practical manufacture of steel of almost every grade, during the past 40 years, and I shall suggest changes that will bring about the results desired. Doctor Dudley has had a long experience as chemical and metallurgical expert for the Pennsylvania railroad, but he frankly admits that up to the present time both he and other metallurgical experts lack the practical knowledge of steel-making that is necessary to state correctly the reasons for the unreliability of the steel rails now produced. The necessity is self-evident for more positive practical knowledge on the part of these experts of what is possible and what is impossible regarding the practical manufacturing of steel rails from the ingot to the, finished product. Chemical knowledge in steel-making is far in advance of what it was years ago, and might be said to cover every requirement (in that department) for producing reliable steel. The study of the metallography of steel has been of great value, also the physical testing of steel, but this knowledge will only de-

May 1, 1909

By Joseph C. Kieffer

THE Duquesne property of the Callahan Zinc-Lead Co. is about 20 miles east of Nogales, in southern Arizona. One mine is near the mill, but most of the mill feed is hauled in by truck from a number of small mines. The same sulphides are found in all the ores, in general, but the amounts vary considerably. All ores contain silver, copper, lead and zinc minerals but one mine ships ore high in silver and lead and low in copper and zinc; while another mine ships ore high in copper and zinc, and low in silver and lead. The common sulphides are galena, carrying most of the silver; chalcopyrite; sphalerite, carrying iron in solid solution; and pyrite, in a gangue consisting of limestone, quartz and garnet. Mineralization is fairly coarse. At the present grind of about 66 per cent minus 200 mesh most of the sulphides are liberated. A small amount of chalcopyrite is locked up with the sphalerite and cannot be liberated at an economic grind, and the copper carried into the zinc concentrate with the sphalerite accounts for the comparatively poor recovery of copper in the copper-lead concentrate. PRODUCTION OF TWO CONCENTRATES The milling problem, which was complicated by the extreme variation in the grade of the feed, was first attacked with the idea of producing a silver-copper-lead concentrate and a zinc concentrate, both with satisfactory grades and recoveries. By February I94I, it was felt that these objectives had been attained, when the grades of the various products and the recoveries were as shown in Table I. [ ] A rough outline of the flowsheet and reagents used is as follows: Minus ¾ -in. feed to a 7-ft. by 36-in. Hardinge ball mill working in closed circuit with a 36-in. Wemco classifier. The classifier overflow passes to the second cell of an 8-cell bank of No. 18 Special Denver Sub-A flotation machines (volume, 22.5 cu. ft. per cell). A rougher concentrate is removed from the second to the fifth cells inclusive, and returned to the first cell, which is the cleaner. A scavenger concentrate is removed from the sixth, seventh, and eighth cells, and returned to the third cell. Consump

Jan 1, 1942

By L. P. Teas

In spite of the influx of operators into the Gulf Coast anxious to retrieve their depleted production in other fields, and in spite of very active application of the most scientific geophysical methods to locate new producing areas, the results have been very discouraging and the year has failed to produce more than the average results for a Gulf Coast year. During the year seven new oil fields, some of which are still of very little importance, and one new gas area have been discovered. These fields are Tom Ball, Greta, Cleveland, Raisin and Garwood in Colorado County; Louise and Premont in Jim Wells County, and the new producing gas area near Ace in southern Polk County. During the year salt has been found for the first time at Carlos and Esperson. New producing areas have been developed on East Stratton Ridge, Hockley, Hull, Port Neches, near Pettus in Bee County, and on the O'Connor Ranch in Victoria County. The total production for the Gulf Coast for the year was 62,837,435 bbl., an increase of 18,589,000 bbl. over 1932. During the year, 1307 wells have been drilled of which 207 were wildcats, compared with 653 wells and 141 wildcats the previous year. The total daily production at the end of the year was 165,201 bbl. At present there are 3100 oil wells producing. The average production per well is 55.5 bbl. per day. The price of crude fluctuated considerably during the year, beginning at 80c per barrel and closing the year at $1.04 per barrel. Completion data for 1933 are as follows:

Jan 1, 1934

By John W. Langley

In the summer of 1888 it was the fortune of the writer to present the subject of the desirability of establishing a set of samples of steel, which should be analyzed with extreme care, in order that they might become standards to which scientific and commercial analyses of iron and steel could be subsequently referred; also, that greater uniformity in the results of analyses might be brought about, since these standards would bear towards analytical methods somewhat the position which the original units of weight and length, the gramme and meter, or the pound and yard, preserved in Paris, London, and Washington, do to the mechanical arts. The plan met with hearty co-operation, with the result that com mittees were appointed in Sweden, Germany, France, England, and America, to receive the material and to see that the necessary au alyses were executed. In England, the British Association for the Advancement of Science appointed a committee, which subsequently published a plan

Jan 1, 1891

FRank FirmstoNe, Easton, Pa.: The effect of lead on brass seems to have been recognized by Berthier, and the facts published by him as early as 1818 (Ann. des Mines, 1st ser., iii., 1818, p. 347 et seq.). He there says expressly that copper containing lead makes " dry " (see) brass, and that, for the same reason, blast-furnace

Jan 1, 1898

By C. R. Van Hise

Introduction.............29 The Three Zones of the Lithosphere ..30 Zone of fracture............31 Zone of flowage............ 31 Factors influencing depth at which flowage occurs.. 32 Zone of combined fracture and flowage.. 33 The Water-Content and Openings in Rocks....36 Condition of rater in the zone of fracture.. 36 The openings in rocks...........38 Size and number of openings..... 40 Ore-deposits derived from zone of fracture..45 The source of underground water......... . 47 The cause of the flowage of underground water..47 Belts of underground circulation.. 51 Upper belt of underground circulation.. 51 Lower belt of underground circulation.. .... .52 Capacity of water for work in the lower belt of underground circulation........... 53 Movementsof water in the lower belt of underground circulation. 54 The preferential use by water of large channels.. 60 Physico-Chemical Principles Controlling the Work of Under ground Waters..........62 Chemical action............63 Underground aqueous solutions..64 The relations of solution and temperature..... 65 The relations of solution and pressure..66 Precipitation........... 67 Precipitation by change in temperature..68 Precipitation by change in pressure..69 Precipitation by reactions between aqueous solutions.. . 69 Precipitation by reactions between liquid solutions and solids. 70 Precipitation by reactions between gases and solutions. and solids............71 The General Geological work of Underground Waters.. . 71 Division of the zone of fracture into a belt of weathering and a belt of cementation............72

Jan 1, 1901

Executive Committee, Board of Directors Augustus B Kinzel, Chairman, J L Glllson, Vice-Chairman, A W Thornton, Howard C Pyle, Grover J Holt Finance Committee, Board of Directors Andrew Fletcher, Chairman, J S Vanick, Gall F Moulton Investments Gail F Moulton, '60, Chairman, Henry Krumb, '59, J Loveloy, '61, C R Dodson, ex off as Treasurer, Andrew Fletcher, ex off as Chairman, Finance Com¬mittee Endowment Andrew Fletcher, Chairman, N G Alford, H DeWitt Smith, W J Coulter, J V N Dorr, R B Gilmore, J B Haffner, O H Johnson, D H McLaughlin, J R McMillan, L F Reinartz, C E Weed, Wilfred Sykes, J R Suman Honorary Memberships H DeWitt Smith, '59, Chairman, C E Reistle, Jr, '59, Grover J Holt, '59, L F Reinartz, '59, M L Haider, '60, D H McLaughlin, '61, John M Lovejoy, '62, Augustus B Kinzel, ex off as President

Jan 1, 1958

By Donald K. Weaver

THERE have been eight different oil zones identified and produced at Santa Fe Springs, of which three or four are in turn divided into two or three parts. These zones are, from top to bottom, the Foix, difference of opinion over this nomenclature, with reference to the different zones referred to as Clark, it has no particular bearing on the water problems. Each of these oil zones has had waters of varying salinity associated with it, either within or at the bottom of the 'zone. Table 1 is a tabulation of the zones, their maximum thicknesses, salinity and heads of various waters. Surface waters are fresh, and of high head, giving artesian flow in some instances.

Jan 1, 1930

By O. O. Laudig

It is a well-established fact that some ores do not reduce as readily in the furnace as others, thus seriously affecting out-put, and consequently, cost of product. With the object of obtain ing some information upon this subject, the following experi ments were made in the laboratory of the Buffalo Furnace Company. Efforts were made to obtain, as nearly as possible, represent ative ores from some of the most important mining districts in the United States. The ores received were from the Mesabi, Marquette, Gogebic, Menominee and Vermilion ranges of the Lake Superior district and from Southwest Virginia. Requests

Jan 1, 1897

By D. C. McLean

This report summarizes the work that has been done during the past several years in adapting resins for use as auxiliaries in mine roof support. The resins were applied in two ways: 1) by injection into the strata, and 2) as a bonding agent for roof bolts and reinforcing bar. The Explosives and Mining Chemicals Department of the American Cyanamid Co. has worked during this period in cooperation with the Roof Control Research Group of the U.S. Bureau of Mines, the Pattin Manufacturing Co., the J. H. Fletcher Co., the Homestake Mining Co., the U.S. Steel Corp., the National Mines Corp. and the Pocahontas Land Corp. in an effort to create resin formulations and methods for applying them as a practical and sate type of roof support for mining areas particularly where conventional support is inadequate, yet expensive. This, work has involved much pioneering in a field where theory, speculation, and pure mythology predominates, and little basic engineering data is available. It is strange butt true that, despite the importance of roof control both from an operational and safely standpoint, there is scarcely a mining' company in this country that has an engineer, or anyone, assigned to the study of roof support problem, except temporarily--after a bad roof fall. The responsibility for improving roof control methods seems to have been placed entirely upon the shoulder, of the USBM, various State departments of mines, and individual roof bolt manufacturing; companies. It was in cooperation with the USBM that Cyanamid first developed resins for mining use.

Jan 1, 1964

By W. Rostoker, H. Nichols

It has been demonstrated in previous work1'2 that wetting of aluminum alloys by liquid mercury can cause fracture to occur with substantial suppression of prior plastic flow. This has been interpreted as the action of a critical liquid species in reducing the cohesive strength of a stressed solid at sites of potential crack nucleation. In this way the critical transverse stress for fracture nucleation is reached at much lower stresses than is normally the case. The stresses for both fracture nucleation and fracture propagation are depressed by the same mechanism. In so doing the plastic-energy component of fracture energy is reduced to a level which is of the same order of magnitude as the surface, interfacial, or cleavage energy. Recent work2 has illustrated the influence of dispersed precipitates, cold work, and combinations of these on brittle fracture associated with plastic strains of the microyield order of magnitude. This has been rationalized in terms of the contribution of internal microstress fields to the stress magnifications at points of obstruction of active slip bands in a stressed metal. The presently reported studies on an Al-4-1/2 pct Mg alloy amplify this subject by introducing thermal-mechanical conditions which can produce strain aging. As amply demonstrated by Phillips, Swain, and borall, the tensile behavior of aluminum alloys containing magnesium reveals a yield-point elongation and successive discontinuous elongations over the whole plastic-strain range. This gives a stepped or serrated character to the stress-strain diagram. The yield-point elongation is not temperature-dependent. On the other hand, the discontinuous extensions in the plastic-strain range are gradually suppressed by lower temperatures of testing. At -78"C, only the yield-point elongation persists. The yield-point elongation itself can be suppressed by rapid quenching to room temperature from an annealing temperature of 500°C. The argument presented by Phillips et 1. and Cottre114 is that the yield-point elongation derives from surmounting at a critical stress the restraint to slip by grain boundaries which have been reinforced by appreciable magnesium-atom segregation. The serrated character of the plastic-strain range is the result of rapid strain aging during the test. This is made possible by the inevitable proximity of magnesium atoms to any dislocation line. In the Al-4-1/2 pct Mg alloy there is one magnesium atom for every twenty-two aluminum atoms and, with a coordination number of 12, a magnesium atom is on the average only about two atomic distances from any given lattice site. Rapid strain aging is therefore a reasonable expectation. A study of mercury embrittlement of the Al-4-1/2 pct Mg alloy (commercial designation 5083) provides an opportunity to relate the interplay of grain size, grain boundary restraint to slip and strain aging in the brittle-fracture process. One lot of commercial sheet material of 0.125-in. thickness was used for all of the tests. The specimen shape and test procedures used were the same as those described in a previous publication.2 A range of grain sizes between 0.0057 and 0.0125 mm was produced by various combinations of plastic prestrain and annealing. The coarsest grain was somewhat elongated in shape. In this case the measurement was taken in the direction transverse to the axis of tension as more meaningful to a brittle-fracture process. In the annealed condition, specimens wetted with mercury failed with zero permanent elongation at stresses slightly below the normal yield point, i.e., stresses at 0.05 to 0.2 pct strain. Since this occurs before yield-point elongation can begin, fracture derives from slip contained within individual grains and restrained from propagating across grain boundaries. No significant difference in wetted fracture stress was observed between specimens which had been water-quenched or furnace-cooled from the annealing temperatures. This signifies that the degree of magnesium segregation at grain boundaries

Jan 1, 1964

By A. B., Sabin

THERE are many who know The Lucky Tiger and will remember the 35-mile road from Esqueda, a station on The Nacozari Railroad in northern Sonora, Mexico. They will remember the box canyons of the Agua Caliente Mountains which are scarcely wide enough for two cars to pass; the Bavispe River which one hour may be a lazy trickle and the next a sweeping torrent, and the tortuous road up Tigre and Espuela canyons, now following the wash, now hugging some gigantic red cliff. It is still the same. From camp the view of the distant blue-gray mountains is the same. But one thing a visitor of a former day might miss: The hundreds of pack mules and burros, loaded with concentrates from the mill, which used to take most of the road and show up at the most inopportune places, have almost disappeared, replaced of course by the auto truck.

Jan 1, 1929