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E. E. Olcott, New York City: Prof. Kemp's valuable description of the Lancaster Gap mine is in line with many other able contributions on the origin of mineral deposits that the Institute has lately brought forward. The splendid contribution that Prof.

Jan 1, 1895

By C. Y. Ang, C. Wert

Quench aging of supersaturated solid solutions of nitrogen in columbium takes place in reasonable times in the temperature range 300&apos; to 500°C. Changes in internal friction, hardness, and electrical resistivity are found to accompany this change. THERE is practically no detailed information in the literature concerning interstitial solid solutions in either columbium or tantalum. The fact that both of these metals are used extensively commercially in both pure and alloyed states makes studies of their properties of value. While the plan is to study both these metals and their alloys extensively, so far only a small number of measurements have been made. This paper presents data obtained in the initial investigations of columbium. The principal interstitial impurities of columbium are likely to be hydrogen, carbon, oxygen, and nitrogen. The first of these, hydrogen, is outside the scope of internal friction measurements at present and nothing quantitative is known about the initial hydrogen content of the specimens. However, it is believed that it is completely absent after the preliminary heat treatments are carried out. The carbon content of the original samples is low and can be reduced still further during sample preparation. Oxygen is normally present to some extent in columbium and can also be added or removed easily. Nitrogen is also normally present in small amounts and can also be controlled within limits. Since it is not possible yet to remove all the nitrogen from columbium and since it is possible to remove essentially all the oxygen and carbon, initial measurements were made on the alloy system nitrogen in columbium. In this sense then, the alloys are true binary alloys. Little is known about the effects of nitrogen on the physical and metallurgical properties of columbium, so it was necessary to perform some rather elementary measurements on the specimens. These measurements are described briefly in the next section and are discussed in detail in later sections. Scope of the Work That internal friction is associated with diffusion of nitrogen in columbium has been known for some time. It is similar in nature to that for carbon and nitrogen in a-iron. In these latter cases, the information obtained from internal friction has been useful metallurgically.&apos; and it is not too much to expect useful information from similar studies on columbium containing nitrogen. The technique of internal friction measurements is adequately described by Ke2 At a frequency of 1 cps the internal friction peak for nitrogen in columbium occurs at 300°C and that for oxygen at 160°C." So that all the measurements will be meaningful metallurgically, the internal friction has been calibrated by making a measurement of the damping at the two peaks and a measurement of oxygen and nitrogen content by chemical analysis. A comparison of the two gives the following calibration factor: To go from damping capacity expressed in terms of 1/Q to weight percent of oxygen and nitrogen in solid solution in columbium, multiply the peak values of internal friction by about 4 and 3 respectively." Data from which these factors were calculated are presented in Table I. The increase of electrical resistance of columbium caused by the addition of oxygen and nitrogen as interstitial impurities has been quantitatively determined. At room temperature the percentage increase is small for small additions of impurities (<0.1 wt pct); as the temperature is lowered it becomes an increasingly larger factor of the total resistance. An empirical relation has been established to express the resistivity at — 195°C in terms of weight percent of oxygen and nitrogen in solid solution. It is easy to make supersaturated solid solutions of nitrogen in columbium and to observe aging phenomena. The optimum aging temperature, as in the case for carbon and nitrogen in a-iron, occurs at the temperature for which the time necessary for a single place-change in diffusion is about 1 to 10 millisec. This means for nitrogen in columbium that significant property changes should take place for this alloy at about 400" to 500°C in reasonable time intervals. Results of such aging experiments are

Jan 1, 1954

By Heinrich Ries

The manufacture of fire-brick represents one of the oldest branches of the clay-working industry in New Jersey, and is of more importance than is commonly imagined. The New Jersey clays were first used for fire-brick after the war of 1812, and one of the earliest records, according to Professor Cook, shows that clay was taken from Woodbridge to Boston in 1816, arid used for that purpose. The value of the clays of the Woodbridge district does not seem to have been well and widely recognized for some years, however, although in 1855 the statistics, given in the Geological Report, show that clay for making 50,000,000 fire-bricks was then taken annually from the pits at Woodbridge, Perth Amboy and South Amboy. Perhaps the oldest works in the State was that known as the Salamander works (no longer in existence), where brick were made as early as 1825. A little later, in 1836, John R. Watson established a factory at Perth Amboy, and in 1858 Sayre & Fisher began the manufacture of fire-brick at Washington. The works of W. H. Berry at Woodbridge began operations in 1845, and have continued up to the present clay, although in 1896 the name was changed to J. E. Berry. The works of Henry Maurer & Son were established in 1856, and those of M. D. Valentine & Brother in 1865. These latter were started for making bath brick; later, sewer-pipe, and, finally, fire-brick and other refractory shapes were produced. A branch-works, located at Valentine on the Central railroad of New Jersey, was started in 1887. Even in the last two years several works have begun the manufacture of fire-brick. These include factories erected by

Jan 1, 1904

THE slag performs two useful functions in open-hearth steel- making. First, it is the means of disposal of all the impurities, save carbon, which are removed from the charge materials in refining the steel, so it must be suited to receiving and retaining as much as possible of undesirable elements with minimum loss of iron and useful alloying elements. Second, the slag serves as a buffer between the flame and the bath and transfers oxygen to the metal at a measured pace contrasted with the violent and difficultly controlled oxidation of the bessemer process. At the same time, the slag is a thermal insulator that limits the rate at which heat can be delivered to the metal from the flame, and a heavy slag blanket thereby serves as a brake on production rates. It has been said with justification that the secret of good steel- making is to make a good slag and the steel will take care of itself. In a broad sense, the subject of slag control includes not only the adjustment of the composition of the slag but also of its relative weight in terms of percentage of the metal-bath weight. The slag is made up essentially of: (1) oxides formed by oxidation of silicon, manganese, phosphorus, and iron in the charge, (2) Si02, MnO, MgO, and other oxides charged as such or introduced incidentally with ores or fluxes or by refractory erosion, and (3) lime charged or fed to the heat to neutralize the "acidic" oxides present (Si02 and P205). Obviously, if practically perfect control were possible over the composition of the charge as well as over the oxidation process during the melting period, both slag weight and composition would be very nearly predetermined; and the control problem would be solved. Unfortunately, only a somewhat imperfect control over these factors is possible, so the operator must begin during the lime boil and continue through the refining period to discover and correct departures from the normal pattern of slag development. To do this as the heat progresses, the first helper must be able to make quick estimates of the composition and physical state of develop-

Jan 1, 1964

By D. A. Vaughan

COMPOUNDS in the U-N system have received little attention since the work of Rundle, Baen-ziger, Wilson, and McDonald in 1948.&apos; They described the three nitrides UN2, U2,N2, and UN as the only phases in this system. The region between UN and U,N, was reported to consist of the two phases while the region between U,N, and UN, is a homogeneous solid solution in which the U,N3, structure transforms with increasing nitrogen content into the UN, structure. This report presents the results of an X-ray diffraction study of the phases present in the region of the diffusion gradient on uranium reacted with nitrogen at several temperatures between 500" and 915°C. Several samples of uranium used in U-N gas-metal reactions by Mallett and Gerds were available for X-ray diffraction study of phase composition through the diffusion gradient. X-ray diffraction data were obtained using filtered iron radiation at intervals through the diffusion layer of the several samples on filings or turnings at approximately 0.001 in. increments down to the base metal. Representative X-ray diffraction patterns from various layers through the case on uranium after nitriding at 850°C are shown in Fig. 1. These data show that three different phases are present in the

Jan 1, 1957

By E. L. Mann

Asbestos is the generic name given to a group of fibrous mineral silicates found in nature. They are all incombustible and can be separated by mechanical means into fibers of various lengths and cross sections, but each differs in chemical composition from the others. The commercial grades of asbestos consist of a spectrum of lengths and sizes and are not definitive as are most organic fibers. It is generally recognized that there are two main groups of asbestos. The first only contains the fibrous serpentine called chrysotile and comprises about 94% of the world production of asbestos. The second group contains five minerals in the amphibole series-crocidolite, amosite, anthophyllite, tremolite, and actinolite. The latter two have no commercial importance. Properties Physical The structures of asbestos fibers have been studied intensively over a number of years. X-ray diffraction patterns have been used as a means of identification and classification. Low angle X-ray scattering techniques have shown that chrysotile fibers are "hexagonally close packed" and parallel to each other, having cross-sectional diameters varying from 18Å to 300 Å units, while the amphibole fibers are many times larger in cross section, have considerably smaller surface areas, and the fibers are less symmetrical than those of chrysotile. Electron micrographs of the more common types of asbestos are shown in Figs. 1-4. Fig. 1 illustrates the softness and flexibility of chrysotile which make it suitable for textile-type products. For a number of years there was considerable controversy over the exact nature of chrysotile fiber, but the photographic evidence in Figs. 5-7 clearly show that it is tubular in structure. The curvature is the result of the mismatch in the dimensions of the silica [Si2O5] and brucite [Mg(OH)2] layers which are on the inside and outside, respectively, of a double sheet. This curvature had been predicted by Pauling (1930) years ago based on the molecular dimensions of the two component structures. In contrast to this, the structure of the amphiboles consists of two ribbon chains based on Si4O11 units separated by a band of seven cations with two hydroxyl groups attached to

Jan 1, 1983

By Prof John E. Church

ONE of the most striking phenomena connected with the mines on the Comstock lode is the extreme heat encountered in the lower levels. This heat is not due to the burning of candles, heat of the men, and decomposition of timbers, all intensified by bad ventilation, as was the case nearer the surface. It proceeds from the rock, which maintains constantly a temperature very much higher than the average of the atmosphere in Nevada. The heat of these mines is a matter of more than usual interest, for they are the only hot ones now worked in the United States, and both in the present temperature encountered and in the increase which is to be expected as greater depths are reached, they appear to surpass any foreign mines of which we have a record. Hot mines are known also in other countries, as in the tin and copper lodes of Wales, where one of the veins worked by the United Mines is known as the hot lode. It has springs which discharge water at a temperature of 116&apos; Fahrenheit, the depth being 220 fathoms, or 1320 feet. The heat of the air in these workings is. given at 100&apos; to 113&apos; Fahrenheit. The air is bad, and the heat in the drifts seems to be traceable to defective ventilation rather than to the real necessities of the case. Air is supplied through a small pipe, and is drawn from a place where the temperature is 95&apos; Fahrenheit. Under such circumstances it is not surprising to read that in this hot mine the air is hotter than the rock, a state of things which I hare never observed in the Comstock. Other mines have been reported to the British Coal Committee as having temperatures of 106" Fahrenheit and thereabouts, but the only positive comparisons that are available at this writing are the following, all from Cornish mines : Mine. Depth Temperature. in feet. Air. Rock. Tresaveau,.....1581 86° 83° to 85° Consolidated Mines,. .. 1500 87° 86° " " . 1722 94o 93° " L .. .. 1764 94o to 96° 921/2° to 931/2°

Jan 1, 1879

By M. W. Hayward

THE object of this paper is to record and tabulate the data and field observations obtained by the writers and their associates during 10 years of intensive study of lead-zinc deposits in the Cretaceous limestone areas in Northern Mexico, particularly in mines owned by the Cia Minera de Peñoles, S. A. At the El Paso meeting of the Institute in October, 1930, J. G. Barry made the suggestion that a committee be appointed to correlate the ideas and theories which have been put forth by the numerous engineers and geologists who, during recent years, have made a study of the ore deposits in the area under consideration. The first step in a work of this nature would be to record all of the observed facts, and these facts would have to be accepted by those who attempted to formulate a theory of ore deposition. It is with this idea in mind that the writers have described as accurately as possible the actual, observed facts pertaining to the occurrence of the lead-zinc ores in dolomites or dolomitic horizons. By most writers the term "dolomite" is loosely used to designate magnesium-bearing limestones, regardless of the percentage of MgO present. Since no true dolomites exist in the areas to be described, we shall also loosely use the terms dolomite or dolomitic limestone to desig-nate those beds having a magnesia content of 5 per cent MgO or more. For a number of years the writers have been impressed with the fact that in areas where dolomite beds occur a large percentage of the lead ore is found in these beds, in spite of the fact that such beds may be overlain or underlain by pure limestone, which one would assume to be just as favorable for replacement as the dolomite, if not more so on account of its being more soluble in acid solutions than the dolomite. It is true that in some limestone areas, such as the Erupcion-Ahumada districts, Chihuahua, and Providencia, Zacatecas, where no dolomite beds have been found, large tonnages of lead ores have been mined. We venture to predict, however, that had there been dolomitic beds in these areas, the

Jan 1, 1932

By M. W. Hayward

THE object of this paper is to record and tabulate the data and field observations obtained by the writers and their associates during 10 years of intensive study of lead-zinc deposits in the Cretaceous limestone areas in Northern Mexico, particularly in mines owned by the Cia. Minera de Peñoles, S. A. At the El Paso meeting of the Institute in October, 1930, J. G. Barry made the suggestion that a committee be appointed to correlate the ideas and theories which have been put forth by the numerous engineers and geologists who, during recent years, have made a study of the ore deposits in the area under consideration. The first step in a work of this nature would be to record all of the observed facts, and these facts would have to be accepted by those who attempted to formulate a theory of ore deposition. It is with this idea in mind that the writers have described as accurately as possible the actual, observed facts pertaining to the occurrence of the lead-zinc ores in dolomites or dolomitic horizons. By most writers the term "dolomite," is loosely used to designate magnesium-bearing limestones, regardless of the percentage of MgO present. Since no, true dolomites exist in the areas to be described, we shall also loosely use the terms dolomite or dolomitic limestone to designate those beds having a magnesia content of 5 per cent MgO or more. For a number of years the writers have been impressed with the fact that in areas where dolomite beds occur a large percentage of the lead ore is found in these beds, in spite of the fact that such beds may be overlain or underlain by pure limestone, which one would assume to be just as favorable for replacement as the dolomite, if not more &apos;so on account of its being more soluble in acid solutions than the dolomite. It is true that in some limestone areas, such as the Erupcion-Ahumada districts, Chihuahua, and Providencia, Zacatecas, where no dolomite beds have been found, large tonnages of lead ores have been mined. We venture to predict, however, that had there been dolomitic beds in these areas, the

Jan 1, 1931

By Charles Frey

TIE fundamental principle of resistance thermometry lies in the determination of temperatures by the measurement of an electrical conductor subjected to various temperatures and the translation of the resultant changes, in ohms, into temperature equivalents. Such resistance measurements can be made with maximum precision by the use of a standard Wheatstone bridge and a reflecting galvanometer of high sensitivity. Under such conditions, results are obtainable that may be accurate within 0.1 or even 0.01 per cent., and the "idiosyncrasies" of heated electrical conductors can be studied with advantage and profit, even if the latter is not of a financial nature. The chief requisites for producing a serviceable -commercial instrument may be enumerated as follows: First, there must be a resistor or "bulb" that can stand the maximum temperature without deterioration and which has a pronounced temperature coefficient. Second, there should be constructed an "even" bridge, having two fixed arms of equal values, in ohms. Third, a rheostat, the maximum resistance of which will be equal to the total change in the resistance of the bulb, between temperature extremes, is required. Fourth, there must be a sensitive galvanometer which is aperiodic, or nearly so. Finally, there should be a fairly steady source of direct current. The general scheme of this type of apparatus, in its simplest form, can be readily understood by reference to Fig. 1. Resistors A and B are constructed of manganin, therlo, or some other resistance wire having a negligible temperature coefficient. The sensitive D&apos;Arsonval galvanometer G has its zero in the center. R is a rheostat and X is a resistor or bulb made of insulated platinum wire, or else of nickel, copper, or some alloy, according to requirements. K is a battery, but a direct-current service line is often used instead, with sufficient ballast in series to properly reduce the current.

Jan 8, 1919

By R. G. Knickerbocker, R. R. Lloyd, W. T. Rawles

In July 1041, the Experiment Station of the Bureau of Mines at Boulder City, Nevada, began a study of methods of producing magnesium metal from magnesium oxide, with particular emphasis upon the direct use of magnesium oxide in a molten chloride electrolyte. The program was extended to include pilot-plant study of chemical methods for the preparation of pure magnesia from dolomites and magnesites. Preliminary work on the production of magnesia from dolomite was done with the cooperation of Kobert D. Pike and the Harbison-Walker Refractories Co. These investigatipns included a cooperative arrangement whereby the Bureau tested certain steps of the Harbison-Walker-Pike process. The process finally developed by the Bureau includes the precarbonation mixing step of the H.W.P. flowsheet prepared by Mr. Pike. Two magnesium-reduction plants using MgO as a source of magnesium were being constructed in the West, and they enormously stimulated interest in various dolomite deposits as possible sources of the magnesia needed by them. This paper describes one phase of this program—the operation of a pilot plant for producing cell-grade magnesia from dolomite from Sloan, Nevada. The process developed for this purpose is an adaptation of a well-known process first proposed by Clossonl and modified by others,2"1 involving the use of calcium chloride and carbon dioxide. It is based on the following chemical reactions: MgCl2 + Ca(OH)2 = CaCl2 + Mg(OH)2 [1] Mg(OH)4 + CaCU + CO2 = MgCl2 + CaCO, + H2O [2] The first reaction proceeds almost completely to the right because of the much greater solubility of calcium hydroxide as compared with magnesium hydroxide. Under equilibrium conditions, when only the four components shown in reaction I are involved, the ratio of magnesium to calcium in solution, according to solubility-product relationship, will be: This reaction is the basis of present commercial processes for recovering magnesium from sea water and dolomite. The second reaction is, in effect, a reversal of the first reaction produced by adding COz. This reaction also proceeds nearly to completion, the solubility relationship being: Ca where P indicates partial pressure of COz, in atmospheres.

Jan 1, 1944

By C. R. Dodson, W. T. Cardwell

This paper presents the results of a theoretical and experimental study of the effect of preperforated liners on well productivity. The analysis concerns the rectangular type of slot, either machine or torch cut, which is common in California. Muskatla treated this problem recently in a mathematical analysis of the flow of oil or gas from natural reservoirs into both gun-perforated and slotted liners. This paper presents additional and simplified analytical considerations and conclusions for the slotted liner, the solutions being applicable in the laboratory as well as in the field. An application of the analytical methods to permeability measurements on mounted core samples is given, to show the effects of sealing wax or other obstructions on the end faces of the cores. Results Fig. I &apos;Ompares the results of some theoretical calculations with the results of electrical analogy experiments performed in the Standard Oil Company of California&apos;s Production Technology Laboratory at La Habra, California. Fig. I indicates that the flux into short, "three-dimensional slots" of the relative dimensions encountered in practice is approximately equal to that into full-length, "two-dimensional slots" having the same open fraction of pipe. (The same numbers of slot rows, and the same radius ratio are also implied.) It can be seen from physical considerations that the closeness of this approximation must improve as the ratio of the external radius to the internal radius increases. Therefore, it is possible to calculate the flow into a slotted liner using a simple modification of the Darcy equation: where N is .the number of slot rows and O is the open fraction of the pipe. Fig. 2 shows the results of calculations . using Eq. 28. The most remarkable features of Fig. 2 are the high flux values for very small open fractions of pipe. For instance, with six slot rows and a radius ratio of 500, 74 per cent of the open-hole flux may be obtained with only o.I per cent of pipe Open. Fig. 2 shows that for a given open frac tion of pipe, the flux is greater, the greater

Jan 1, 1945

By Paul Bechtner

THE name bentonite formerly was applied solely to a peculiar clay occurring in Wyoming and South Dakota, which was distinguished from other clays by its unctuous feel when wet and the property of swelling in water. In the last decade scientific studies of clay have recognized that bentonite is composed mainly of the clay mineral montmorillonite and the name bentonite has been extended to cover the entire family of clays that have montmorillonite as their chief constituent. Montmorillonite has the chemical formula of A1203-4Si0-xH2O, With Fe203 and MgO replacing part of the A1203. The montmorillonite crystal is an Si-Al-Si clay mineral, being formed of two silicon-oxygen sheets with an aluminum-oxygen sheet sandwiched between them. In contrast, kaolinite-the chief clay mineral of most clays other than bentonite-is Si-Al, one silica and one alumina sheet. The unit crystal of montmorillonite is much thinner than that of kaolinite, with greater surface area. These differences in crystal structure patterns are leading factors in the dissimilar properties and commercial uses of bentonite compared with other clays. Mineralogically, bentonites are 85 to 90 pct montmorillonite with fragments of feldspar, gypsum, calcium carbonate, quartz and traces of other minerals. They vary in color; the widely used Wyoming type is creamy white when dry and a light shade of tan when wet; the low-swelling bentonites of the southern United States and elsewhere are found in many shades of gray, blue, yellow, red, and brown. Pure white bentonites are rarer and generally of the medium or low-swelling type, though there are a few exceptions to that general rule. PROPERTIES Bentonites may be divided into two general classes: (1) those that adsorb large quantities of water, "swelling" greatly in the process, and that remain in suspension in thin water dispersions; (2) those that adsorb only slightly more water than ordinary plastic clays or fuller&apos;s earths, do not swell noticeably, and settle rapidly in thin water dispersions. Another distinction is that some varieties of the No. 2 type

Jan 1, 1949

INTRODUCTION Porphyry copper deposits have been reported from the Caribbean area by Pease (1966), Cox, et al. (1973), Guild (1974), Kesler, et al. (1975), and others. This chapter summarizes the most widely known characteristics of those deposits. Only one deposit that conceivably can be classed as a porphyry copper occurrence is in production (Pueblo Viejo, Dominican Republic), but others are known whose tonnage and grade are of economic interest. Deposits in this province may be classified as copper-gold or copper-molybdenum types (Kesler, 1972), but deposits associated with quartz-rich plutons that have high Na2O:K2O and high gold:copper but low molybdenum: copper ratios dominate. Porphyry copper occurrences are reported in the literature from Puerto Rico, Haiti, the Dominican Republic, Jamaica, and Cuba. Only the porphyry copper deposits from Puerto Rico are extensively described in the literature; consequently the Caribbean porphyry copper province in general is not as well documented as the southern Cordilleran orogen. Because past published technical descriptions are incomplete, some data presented here are new to the literature. The Caribbean includes the island arcs between North and South America. Porphyry copper occurrences are known from the Greater Antilles, the generally east-west trending group of islands that lies south of North America. Fig. 48, therefore, only covers the Greater Antilles portion of the Caribbean. Porphyry copper deposits in this area are not described by the Lowell and Guilbert (1970) model in details of metallization (general paucity of molybdenum), alteration (scarcity of orthoclase), or petrography (preponderance of quartz diorite). Therefore, this model should be modified to include deposits associated with quartz-bearing plutons such as those found in the Caribbean. In the Meme deposit on Haiti ore occurs in skarn adjacent to the quartz diorite phase of a composite quartz monzonite-granodio-rite-quartz diorite pluton (Kesler, 1968). This deposit, with a K-Ar 66 m.y. date, is not included in Fig. 48 as a porphyry copper deposit because metallization is restricted largely to the intruded rocks. Although the intrusive rocks at the Meme deposit may contain sulfide near skarn contacts they are otherwise essentially unaltered. Porphyry molybdenum deposits as defined by Clarke (1972) have not been reported in the Caribbean area.

Jan 1, 1978

By William F. List, Marvin A. Schuster

Monolithic electrooptical mosaics of 2500 photo-transistor elements with internal row and surface column interconnections have been fabricated by epitaxial-planar diffsion techniques. Unique access to any elemed of the mosaic is provided through one of the fifty X and one of the fifty Y external leads. The sensor mosaic can be used for imaging applications and has a 1:1 aspect ratio, a resolution of 100 lines per in., a dynamic range in excess of lo3, a sensitivity of 0.5 per pw, element response within a 2:l range over 75 pct of the mosaic, and a minimum detectable signal of the order of 10-&apos; w. Design considerations which ilnpose particclar fabrication yequirements are disctussed along with some of the problems peculiar to the epitaxial and planar-dijfision techniqes by which this device is fabricated. The solid-state silicon monolith has an imaging area of 0.5 by 0.5 in. and an element center -to- center spacing of 0.010 in. J monolithic solid-state electrooptical device has been developed as the photon-sensing mosaic for use in an image-converter system.&apos; This system is the solid-state equivalent of the vidicon and can image radiation in the visible and near-infrared regions of the spectrum. The electrooptical image converter has the desirable size, weight, reliability, and low-power characteristics inherent in solid-state devices. It is read out by direct-wire means rather than by beam-scan techniques. The packaged unit is shown in Fig. 1. A selection of material for the sensor was based on considerations of both reliable fabrication techniques and material spectral response. Silicon was selected both for its response from the lower end of :he visible to the long-wavelength cut-off above 11,000A and for its well-developed epitaxial planar-diffused technology. The electrical image is composed of M x N discrete information bits with each bit emanating from one of the individual phototransistor sensors. The interconnected mosaic concept was introduced to provide a structure which is both manageable in its number of leads and compatible with conventional viewing systems which accept XY data. Interconnections along the Y direction are provided by internally diffused strips, while interconnections along the X direction are formed by vacuum-deposited metal surface bars. Unique access to any individual element of the M x N mosaic is available through one of the M and one of the N external leads. PHOTOTRANSISTOR DESIGN A phototransistor structure2 was selected for the discrete photon detectors of which the mosaic is com- posed. Basically, the mode of phototransistor operation is such that incident quanta are absorbed in the base area of the element where they generate electron-hole pairs. If the electrons are liberated within a diffusion length of the depletion region around the collector junction, they will diffuse to this depletion region and be swept across the junction where they account for a small component of the photocurrent. Similarly, the holes which are created within a diffusion length of the emitter junction will diffuse to this region where they forward bias the emitter and so induce injection of minority carriers into the base. This accounts for the substantial transistor photocurrent. This mechanism of operation implies several design and fabrication goals for the individual sensor elements: high electrooptical conversion efficiency, sufficient carrier lifetime in the base regions, and a maximum volume in which photons can be absorbed within a diffusion length from the depletion layer about the junction. Moderately high transistor gain is desirable to permit readout at low light levels; however, very high gain has a deleterious effect on mosaic dynamic range. The mosaic must also be characterized by good uniformity of element response as well as by good isolation between elements. The above set of conditions imply that junction depths must be optimized with respect to photon ab-

Jan 1, 1967

By Charles E. Locke

The little stamp-mill in the mining laboratory of the Massachusetts Institute of Technology and the work done by it have been well described by Prof. R. H. Richards and E. E. Bugbee in a paper read at the Albany meeting of the American Institute of Mining Engineers, February, 1903.&apos; As run for student class-work the mill contains a feeder, stamps, plate, and vanner. Results in the past indicate that the work of these machines is just as efficient as that of a regular mill handling the same class of ore. It has been the custom to obtain ore principally from Nova Scotia, mainly because it is the nearest source of supply, and also because there is a considerable saving in freight-cost as compared with other districts. The gold in Nova Scotia ores is notoriously coarse, and for this reason it is almost impossible to obtain satisfactory results by sampling and fire-assay, unless an extremely large lot of ore is crushed and all of the contained gold pellets are saved. A very interesting and most extraordinary example of this fact has been presented by a recent run in the Technology stamp-mill. Since the capacity of the mill is about 60 kg. per hr., and since in about 5-hr. run the students in any one section have an opportunity to make the necessary study of machines, it usually happens that several runs are made from one lot of ore. When the shipment is received it is first dried and weighed, put through the Blake breaker, set at 1 or 1.5 in., and the crushed product is piled in a cone on the sampling-floor. When the crushing is completed the ore is usually stored away in barrels for future use; it is aimed to have each barrel of

Jan 1, 1914

By J. A. Holmes

SHUTTING-IN the Rangely gas well was an interesting problem because of the high rock pressure and the volume of gas developed, as well as the difficulties encountered. After nearly a week&apos;s open flow, the rock pressure was 1275 lb., which corresponds with a 2950 ft. hydrostatic head. The volume of gas was between 45,000,000 and 50,000,000 cu. ft. per day. The Rangeley oil field, which now has a daily production of 100 bbl. of shale oil from shallow depth, lies approximately 100 miles north and 30 miles west of Grand Junction, Colo.; not far from the Utah line. The, well we are considering was drilled on the apex of a large clearly defined. Structure1 in the SE.1/4 sec. 30, T. 2 S., R. 102 W., and entered the gas sand at 2954 ft. on March 2, 1925. The condition of the well at the time the gas was encountered was as follows: 20 ft. of 20-in. conductor cemented with ten sacks at 40 ft. The 15 1/2-in. casing was pulled when the 12 1/2-in. was cemented. 1166 ft. of 12 1/2-in. casing, cemented with fifteen sacks. 2531 ft. of 10-in, casing, cemented with ten sacks; neither the 12 1/2-in. nor the 10-in, casing shut off water but they were cemented for protection. 2938 ft. of 8 1/4-in. 36-lb. casing, hanging on a spider in the collar with a forged-steel, high-pressure bradenhead between it and the 10-in. casing. An 8 1/4-in. drilling, or master, gate and a control head were in place on the 8 1/4-in. casing, and all was in readiness for the bringing in of the well.

Jan 1, 1926

ARTHUR PHILLIPS,* Bridgeport, Conn. (written discussion?).-It is to, be regretted that the very valuable paper by Messrs. Bassett and Davis did not appear in the early war period. The data presented would have been of inestimable service to inspectors, of cartridge brass who, admittedly, had little or no knowledge regarding the relation of grain size to temperature of anneal, and no real appreciation of, the significance of the Brinell hardness test. The paper is of considerable interest to, metallurgists also. WALTER R. HIBBARD, ? Bridgeport. Conn. (written discussion§).-The writer has carefully studied Messrs. Bassett and Davis&apos;s paper with considerable interest, inasmuch as our laboratory has tested cartridge brass by means of a Brinell machine. In March, 1917, at the suggestion of the Technical Department of the American Brass Co., we started a comparison of grain-size measurements and Brinell hardness of-cartridge brass with a gage of 0.1 in. or greater. This was continued until March, 1918, when we adopted the Brinell hardness test as standard for brass 0.1 in. gage or greater, and discontinued grain-size measurements upon this metal. The data collected during the test showed that the Brinell hardness indicated more accurately how the metal acted in actual working operations. It was also more reliable because two manipulators check themselves closer by the Brinell test than by the grain-size measurements. It also consumed less time in making the tests. Alfred V. de Forest, formerly assistant research engineer of our laboratories, has described the apparatus and some of the checking results in a paper read June, 1918, before the American Society for Testing Materials.1 The writer hopes that a more satisfactory. method for testing cartridge brass and gilding in gages thinner than 0.1 in. may be devised than the present method of grain-size measurements.

Jan 3, 1919

By R. G. Davies

THE effect of ordered structures upon steady state creep has not been extensively studied although it has been demonstrated that the brass,&apos; ie,&apos; and Fe3Al3 superlattices increase the creep resistance. Suzuki and Yamamoto observed an acceleration in the creep rate of Ni3Fe below the critical temperature for order, (T, - 505"), for both the ordered and disordered states, and that the activation energy for creep was independent of the applied stress. They concluded that a dislocation climb creep mechanism was operative down to 300°C which is - 1/3 TM where TM is the absolute melting temperature. This is quite remarkable in that it is usually observed that climb controlled creep in both pure metals and alloys ceases below - 1/2 TM (590" for ie). With this anomaly in mind it was decided to reinvestigate creep in a 75 at. pct Ni-25 at. pct Fe alloy. The creep apparatus and operating conditions have already been decribed. Since Ni-Fe alloys order very slowly, it is possible to have a disordered alloy at a temperature below T,. A long anneal at a temperature just below T, produces considerable long-range order;5 the ordering treatment in the present investigation was 150 hr at 485°C which gives an antiphase domain size of-SOW

Jan 1, 1963

By W. P. Blake

One of the most remarkable iron-ore districts of the world is found in Southern Utah, in Iron County, about 270 miles south of Salt Lake City, and 10 miles west of Cedar City. This region has long been known in a general way; but, being at present somewhat difficult of access, it has been rarely visited by &apos;any of our members. Professor Newberry has published somewhere a short description. Last year, by the invitation of J. R. Walker, Esq., of Salt Lake City, one of our associate members, I formed one of a party, including Professor G. W. Maynard and W. S. Keyes, to visit and inspect the region. A special car was placed at our disposal by the courtesy of Hon. John Sharp, Superintendent of the Utah Central Railway. From the present southern terminus of the road at Milford, a drive of 55 miles took us to Cedar City, about 10 miles east of the iron region. The ores outcrop in a low range of hills or mountains, and stand out in such bold relief from the general surface, and are so massive and jet black, that they may be seen for miles before they are reached. These outcrops extend in long lines over the hills, and mark very . clearly the course of the beds, conforming generally to the inclosing stratified formations, probably of Palaeozoic age. These rocks are somewhat obscure, but there are large outcrops of limestone without much alteration. This, in places, appears to be the adjoining rock, at others the wall-rocks are porphyry, and at others apparently a quartzite and a fine-grained felsite. The beds of iron-ore are from 10 to 100 feet and more in thick ness, and some of the outcrops extend unbroken continuously for 1000 feet and more. It consists chiefly of magnetite and hematite,

Jan 1, 1886