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By Raymond Mancha

When calculating the pressure-volume characteristics of projected mine-ventilating circuits by orthodox methods, certain basic assumptions are required in order to employ the various available empirical data. It is assumed, for example, that the mine air is an incompressible fluid subjected to isothermal flow, an assumption sufficiently accurate for practical purposes since pressure and temperature differentials are small throughout the average circuit. A more erroneous assumption, however, is that all air is accounted for as it travels throughout the mine. No attempt is usually made to evaluate stopping leakage as it occurs; instead, the air volume required at the last crosscuts is assumed to enter the mine, travel the various intake air courses intact, sweep the workings and travel out by the return air courses to the point or points of exit from the mine. Actually, there is a leakage of air from intake to return at every stopping, the quantity of this leakage depending upon the tightness of the stopping and the pressure difference across the stopping. Unfortunately, a lack of empirical data and knowledge of the condition of individual stoppings makes an exact analysis of underground stopping leakage impossible. Generally, leakage is most severe through the old stoppings outbye the circuit. These are also subjected to higher pressure differences than the newer inbye stoppings. Therefore the circuit air volume diminishes at a decreasing rate progressing from outbye to inbye the circuit. Consider a simple mine circuit consisting of one intake and one return air course, each of equal and uniform section area and interconnected at regular intervals with crosscuts equipped with stoppings. At any point X inbye the circuit the air volume q on the intake air course equals that on the return air course and decreases with diminishing rate from outbye to inbye the circuit between the limits of Q1 completely outbye and Q completely inbye. Such a volume change is represented by curve a, Fig. I, which is computed with the aid of the equation q = Q1- (Q1- Q)(X + L)N. This equation results from the general algebraic equation of form q = k, — kXN after solving for kl and k with the knowledge that completely outbye X = o and q = QL, also completely inbye X = L and q = Q. Curves a, b and c, Fig. I, show values of q as ordinates versus values of X as abscissas, for values of N equal to 0.50, 1.00 and 2.00, respectively. Distribution of underground stopping 1eakage directly affects the air-volume distribution along the circuit, which in turn determines the circuit pressure gradient. To deliver any required air volume inbye a circuit or portion thereof requires a higher circuit-pressure differential if stoppings leak than is necessary with tight stoppings. Every mining engineer engaged in the analysis of projected mine-ventilation circuits is therefore confronted with the problem of making proper allowance for the effects of leaking stoppings. The purpose of this paper is to present evidence in support of the author's suggestion that circuit pressure increase (per cent)

Jan 1, 1942

By Raymond Mancha

When calculating the pressure-volume characteristics of projected mine-ventilating circuits by orthodox methods, certain basic assumptions are required in order to employ the various available empirical data. It is assumed, for example, that the mine air is an incompressible fluid subjected to isothermal flow, an assumption sufficiently accurate for practical purposes since pressure and temperature differentials are small throughout the average circuit. A more erroneous assumption, however, is that all air is accounted for as it travels throughout the mine. No attempt is usually made to evaluate stopping leakage as it occurs; instead, the air volume required at the last crosscuts is assumed to enter the mine, travel the various intake air courses intact, sweep the workings and travel out by the return air courses to the point or points of exit from the mine. Actually, there is a leakage of air from intake to return at every stopping, the quantity of this leakage depending upon the tightness of the stopping and the pressure difference across the stopping. Unfortunately, a lack of empirical data and knowledge of the condition of individual stoppings makes an exact analysis of underground stopping leakage impossible. Generally, leakage is most severe through the old stoppings outbye the circuit. These are also subjected to higher pressure differences than the newer inbye stoppings. Therefore the circuit air volume diminishes at a decreasing rate progressing from outbye to inbye the circuit. Consider a simple mine circuit consisting of one intake and one return air course, each of equal and uniform section area and interconnected at regular intervals with crosscuts equipped with stoppings. At any point X inbye the circuit the air volume q on the intake air course equals that on the return air course and decreases with diminishing rate from outbye to inbye the circuit between the limits of Q1 completely outbye and Q completely inbye. Such a volume change is represented by curve a, Fig. I, which is computed with the aid of the equation q = Q1- (Q1- Q)(X + L)N. This equation results from the general algebraic equation of form q = k, — kXN after solving for kl and k with the knowledge that completely outbye X = o and q = QL, also completely inbye X = L and q = Q. Curves a, b and c, Fig. I, show values of q as ordinates versus values of X as abscissas, for values of N equal to 0.50, 1.00 and 2.00, respectively. Distribution of underground stopping 1eakage directly affects the air-volume distribution along the circuit, which in turn determines the circuit pressure gradient. To deliver any required air volume inbye a circuit or portion thereof requires a higher circuit-pressure differential if stoppings leak than is necessary with tight stoppings. Every mining engineer engaged in the analysis of projected mine-ventilation circuits is therefore confronted with the problem of making proper allowance for the effects of leaking stoppings. The purpose of this paper is to present evidence in support of the author's suggestion that circuit pressure increase (per cent)

Jan 1, 1942

HUDSON MAXIM, Brooklyn, N. Y.-Immediately after the creation of the Naval Consulting Board, Admiral Strauss, Chief of the Bureau of Ordnance of the Navy, told members of the Board that the most important problem for the scientists to solve was erosion in large guns. The Navy, for years, had been working on the problem with marked suceess, but there was much yet remaining to be accomplished. As Chairman of the Committee on Ordnance and Explosives of the Naval Consulting Board, I communicated with several experts in the manufacture of steel, principal among whom was Prof. Howe. He generously agreed to help in every way possible, and the work that he has done and the time that he has spent upon it can he appreciated only by reading his paper. Prof. Howe asked for some rings. from a, certain 14-in. gun which Admiral Strauss had mentioned in particular, and in which, he had informed us, at each shot the bore of the gun, was enlarged about 0.001 in.,' and that after a relatively small number of rounds it was considerably eroded. It has puzzled scientists for a long time to account for the peculiar erosive effect produced by the powder gases in a gun, arid: what Prof. Howe has done in his paper is worthy of Sherlock Holmes. He is a veritable Sherlock Holmes of science.

Jan 4, 1918

By Chester Wells Purington

Situation.—The Camp Bird mine is in Imogene basin† (Fig. 1) at the head-waters of Canon creek, a branch of the Gunnison, in the southern part of Ouray county, Colorado, towards the northern edge of the region known as the San Juan mountains, and about 10 miles W. of the continental divide. It is 8 miles by wagon-road from Ouray, the terminus of a branch of the Rio Grande' Southern railway. The distance from Denver to Ouray is 387 miles by rail. In an air-line, the mine is 190 miles SW. of Denver. The altitude of the town, tunnel and buildings is 11,200 ft., and level No. 2 is 11,500 ft., and No. 1 is 11,670 ft., above sea-level. The lowest point of the lode-ontcrop, which crosses the basin E. and W., has an elevation of 11,850 ft., and that of the highest point, on the divide between Imogene and Tomboy basins, is 13,250 ft. On the eastern slope of the Imogene basin (towards Ironton) the vein is less clearly defined on the surface. Ownership and Extent.—At the time of the writing of this paper, the property is owned by Mr. Thomas I?. Walsh, and operated under the management of Mr. J. W. Benson. It

Jan 1, 1903

By O. E. Kiessling

A GROWING uneasiness in the oil fields indicates that doubts are arising as to the efficiency of the present technical, economic and legal arrangements affecting production. Recent documents of the federal government, debates in state legislatures, editorials in the daily press and statements of oil company executives re-echo the notion that the present methods of producing oil satisfy neither the business man nor the public. Such intimations are of utmost importance, since oil is a vital clement in modern industry and dependence upon it increases as new uses develop. SECTION I-PRESENT SCHEME OF COMPETITIVE EXPLOITATION IS WASTEFUL The oil industry has convinced itself, for very good reasons, that the present scheme of competitive exploitation results in losses, both in terms of quantities of oil and in terms of profits. The story of these losses is familiar enough, and it is necessary only to distinguish and summarize briefly certain factors that are of importance to the following argument. Oil pools are exploited under a competitive economic system based on private ownership and contract; the hope of profits attracts capital and enterprise, and competition is supposed to serve as a regulative factor. Whether such a scheme of industrial organization works is partially dependent on the ability of the producer to withhold or produce is commodity as he sees fit, in accordance with the dictates of market demand.

Jan 1, 1927

By J. S. Koehler, F. Seitz

THE dislocation theory of plastic flow originated in 1928, when Prandtl1 suggested that the internal damping of metals of plastic origin might arise from the motion of a crystalline imperfection. Following this, Dehlinger2 employed a similar imperfection in a theory of recrystallization. The first detailed theoretical discussions were those of E. Orowan3 and G. I. Taylor4 in 1934. The resulting theory was gen- eralized by J. M. Burgers5 in 1939. Mott and Nabarro, in England, and Seitz and Read,6 in the United States, started an extensive examination of the atomic theory of dislocations in the period between 1939 and 1941. However, this development was arrested by the mar and was not taken up again until after 1945. Since 1946, the field has been the object of very intense activity, particularly in the United States and England. Dislocations are beautiful and intricate imperfections; they are sufficiently complicated to account for the great variety of phenomena encountered in the field of plastic flow. Above all, the dislocation concept enables us to understand how a metal or other plastic solid can deform inelastically under very small stresses at temperatures far below the melting point. Suppose we attempt to shear a perfect crystal plastically. This can be done by sliding one entire atomic plane simultaneously through one atomic distance with' respect to the near-

Jan 1, 1954

By George J. Bancroft

INTRODUCTION. IT is unnecessary to repeat here the contents of many valuable contributions to this subject which have appeared in the Transactions and in the publications of the U. S. Geological Survey. As a basis for the further suggestions of this paper, the following are the most important: 1. The investigation of J. R. Don,1 showing the gold of certain Australasian veins to have been deposited by ascending solutions, and not by lateral secretion. 2. The theory of Prof. Posepny,2 distinguishing the vadose from the deep circulation, and ascribing the origin of certain classes of ore-deposits to ascending solutions of the latter class. 3. The theory of Prof. Van Hise,3 as to the underground circulation and the primary enrichment of veins thereby. 4. The paper of Prof. J. F. Kemp,4 showing that ore-deposits are largely the products of " expiring vulcanism." Many of Prof. Kemp's, ideas have been widely adopted by mining men. 5. The theory of secondary enrichment, so lucidly expounded by Mr. S. F. Emmons.5 This theory, dealing with, the rearrangement of ore-bodies after primary mineralization, has been generally adopted, and seems to me to have been as completely proved as the nature of the case permits. There are two facts which I think should be constantly borne in mind in formulating a theory of the genesis of ore-

Jan 1, 1913

By Hjalmer Sjögren

AMONG the feldspar-rocks there are certain types which occur constantly in different areas-viz., the aruphibolitic plagioclase- rocks and the granulitic rocks Composed of quartz and alkaline feldspars. Among the latter soda: granulites as well as potash are met with; also the corresponding gneisses occur. GROUP I.-THE ORES OF THE ARCHEAN CRYSTALLINE SCHISTS. The Rocks. The ore-bearing rocks of the ore-province of central Sweden are chemically and petrographically unlike the more monotonous gneiss- and granite-areas which surround them. On the whole, they constitute a quartz-feldspar formation in which purer quartzitic rocks, limestones, " skarn " rocks, and ore-bodies are very subordinate members. (Skarn is the Swedish name for rocks of varying composition, mostly consisting of lime, magnesia, iron, and alumina, silicates of the pyroxene, amphibole, and garnet groups; as secondary minerals, epidote, chlorite, biotite, and talc occur. The skarn is scarcely an independent rock but is connected with the ore-deposits. It is formed through an interchange between the silica of the quartz-feldspar rocks and the basic constituents of the ore-formation.) [A BRIDGED SUMMARY.-The amphibolites must be considered as stretched and dynamo-metamorphosed dioritic rocks. The granulites are divided into two groups, one showing predominant plagioclase, the other equal or predominant orthoclase. Evidently, the iron-ore deposits are connected in some way with the

Jan 1, 1913

By George J. Bancroft

It is unnecessary to repeat here the contents of many valuable contributions to this subject which have appeared in the Dansactions and in the publications of the U. S. Geological Survey. As a basis for the further suggestions of this paper, the following are the most important: 1. The investigation of J. R. Don,' showing the gold of certain Australasian veins to have been deposited by ascending solutions, and not by lateral secretion. 2. The theory of Prof. Posepny? distinguishing the vadose from the deep circulation, and ascribing the origin of certain classes of ore-deposits to ascending solutions of the latter class. 3. The theory of Prof. Van Hise,3 as to the underground circulation and the primary enrichment of veins thereby. 4. The paper of Prof. J. F. Kemp,4 showing that ore-deposits are largely the products of " expiring vulcanism." Many. of Prof. Kemp's ideas have been widely adopted by mining men. 5. The theory of secondary enrichment, so lucidly expounded by Mr. S. F. Emmons.V his theory, dealing with the rearrangement of ore-bodies after primary mineralization, has been generally adopted, and seems to me to have been as completely proved as the nature of the case permits. There are two facts which I think should be constantly borne in mind in formulating a theory of the genesis of ore-

Jan 1, 1908

By C. K. Leith

The ores of the region are contained in rocks of pre-Cambrian age, which, for most of the country up to recent years, have usually been referred to as “crystalline schists” or “crystalline complex;” and regarded principally as a metamorphosed basement-unit upon which the sedimentary rocks, beginning with the Paleozoic, were laid down. In the Lake Superior region this pre-Cambrian complex presents an' unusual variety of rocks with determinable relations. It has been possible, with the large expenditures which the magnitude of the iron-mining industry warrants, to work out their stratigraphy to a larger degree than bas been possible in almost any other area of pre-Cambrian rocks. [The portion here omitted contains descriptions of the Archean, Algonkian, and Keweenawan rocks of the several districts, their structure, distribution, correlation, and succession. Table I. and the geological map of the Lake Superior region belong to this portion, but are here reproduced on account of their value as guides to the readers of the rest of the paper.] The simplest and clearest conception of the pre-ambrian succession for the Lake Superior region may perhaps be obtained by thinking of it as primarily divided into six series-Keweenawan, Upper Huronian, Middle Huronian, Lower Huronian, Keewatin, and Laurentian-all but the last two separated by unconformities of varying and disputed relative im-

Jan 1, 1913

By Franklin R. Carpenter

Pyritic smelting, so-called, as practiced in the Black Hills is pyritic smelting only in the sense that Dr. John Percy uses the expression in his " Metallurgy of Silver," where he describes a process for smelting dry silver-ores in connection with iron pyrites, to form a regulus. The ores treated by this process in the Black Hills are very siliceous, averaging about 74 per cent. of silica, from 10 to 20 of iron oxide, 4 or 5 of alumina, and from 2 to 4 of lime. In 1889, while Dean of the South Dakota School of Mines, I took up the question of their smelting. There were neither copper- nor lead-ores in the Hills; hence pyrite and pyrrhotite, of which there are large deposits, were employed to form a regulus. This mixture of pyrite and pyrrhotite, besides being absolutely barren of gold and silver, carried an average of 30 per cent. of silica. The only basic material available as a flux for the great excess of silica in the ores and in the pyrite was a dolomitic limestone. Moreover, the local coke gave 24 per cent. of ash, 60 per cent. of which was silica—as unpromising a set of conditions as can well be imagined. We had before us the examples of Mr. W. Lawrence Austin, of this Institute, who had experimented at Toston, Montana,"

Jan 1, 1901

By E. F. Steeb, P. C. Rosenthal

BlANKS 8 in. long were cut from the as-received bar stock and austenitized at 1560° F for 1 hr, oil quenched, tempered at 1140°F for 1 hr, and water quenched. The heat-treated blanks were machined into tensile specimens which were subsequently used for the straining operation. Some of the tensile specimens were temper embrittled at 900°F for 24 hr and air cooled prior to or following the straining operation. The specimens were strained in tension up to 5 pct total strain (elastic plus plastic) either at room temperature or at 900°F. The reduced sec- tion of the tensile specimen employed was 5 in. long and 0.600 in. in diam. This size specimen was sufficiently large to permit two standard Charpy impact bars to be machined from it. One group of specimens was temper embrittled at 900°F for 24 hr under stress of about 20,000 psi applied with a hydraulic tensile testing machine. Approximately 0.34 pct plastic strain occurred during this treatment. A comparison of series "A" and "B" data in Table I at 0 pct strain, reveals that the steel was rather highly susceptible to temper embrittlement, the embrittling treatment causing the transition temperature to rise 165°F. The 28 ft-lb level, which was near the center of the sharp-rising portion of the transition curve, was selected as the

Jan 1, 1959

By John W. Trammell, Chester O. Ensign

Efficient mining of copper ore at the White Pine mine in Michigan's Upper Peninsula is partially dependent on the rather unique problem of predicting variations and rock types in a barren stratum called the upper sandstone. The pronounced effect which this formation has on the local mining techniques is reflected by the necessity of deciding whether to mine the sandstone along with ore-bearing rock, thus diluting overall ore grade, or, alternatively, leaving the sandstone behind to form the mine roof. THE OREBODY AND MINING TYPES In the mine, the cupriferous zone of the Nonesuch shale is divided into three major portions (Fig. I). Lying conformably on top of the Copper Harbor formation (or "lower sandstone") is the lower part of the orebody, the parting shale. The parting shale is overlain by the upper sandstone. On top of the upper sandstone, the basal portion (8 ft) of the upper shale is quite similar to the parting shale. Both the upper shale and parting shale are divided into a number of smaller stratigraphic units, each having a characteristic copper content, as shown by the histogram of Fig. 1. Other authors have dealt in detail with the stratigraphy and mineralogy of the orebody, so it will suffice here to call attention to the low copper content of the upper sandstone.

Jan 12, 1964

By Carl H. Samans

THE INFORMATION AVAILABLE on the rolling characteristics of the precious metals-gold, silver, the platinum metals and their alloys-is incomplete and mostly from scattered sources. In the present paper an effort has been made to assemble and correlate it and to fill in some of the gaps that exist. GENERAL ROLLING CHARACTERISTICS SOME EFFECTS OF IMPURITIES Gold and its alloys are generally considered to be hot short and hence are usually rolled cold. Cold rolling of the yellow, green, and pink gold alloys. Which customarily contain gold, silver, copper and zinc and frequently some nickel as well, introduces no new problems since reasonable reductions are quite feasible and the alloys show little tendency to fire crack in subsequent annealing. The white gold alloys. which usually contain little or no silver and 10 pct or more nickel, are very susceptible to fire cracking1 and hence wrist he given relatively heavy reductions, i. e., 8-10 pct or more per pass with a total reduction of about 50 pct between anneals, to minimize this tendency. In addition, it is preferable to keep the bar as flat as possible during rolling. Although no comprehensive study appears to have been made of the effects of impurities on the cold rolling characteristics of gold alloys, the observations of Nowack2 on the effects of small

Jan 1, 1948

By Henry Howland

INTRODUCTION DURING the last decade no topic has created more interest or received more thought among blast-furnace men than colic. One reason for this is, undoubtedly, the remarkable increase in the use of byproduct coke. Formerly our coke was made at a distance from the furnaces and by a distinct organization. There was little cooperation or development possible under these conditions. Today the situation is greatly changed. Much of our coke is made by the organization operating the furnaces and the coke oven is operated with the primary object of obtaining the best results in the blast furnace. The effect of changing the method of coke manufacture, even in some minor detail, is often felt almost immediately at the blast furnace. There naturally results one of the most valuable assets of the byproduct coke oven, -i.e., the possibility of increased blast-furnace efficiency clue to close observance and correct operation of the ovens. The results are evident, but it often is difficult correctly to account for them. In attacking the solution of a problem of as much importance as why one coke is better than another, there are facts which should be kept clearly in mind The author hopes, in this paper, to bring out some points relative to the use of carbon in the blast furnace which will be of value in solving this question.

Jan 3, 1916

By M. K. Barnett

Engineering research consists, broadly speaking, in the investigation of the effect of the variations in a number of factors on some property of a product or characteristic of a process. The unambiguous description of the product or process requires that the property or characteristic be expressible in quantitative terms. For the purpose of practical control, it is likewise desirable that the independently variable factors governing the product or process be quantities, although this ideal goal is not always attained. Maximum efficiency—i.e., the attain- ment of the maximum amount of reliable, useful information relating to the influence of, the factors on the property of the product or characteristic of the process, for the least expense—is an important requirement for the satisfactory operation of a research organization. Obviously, a necessary condition for the attainment of maximum efficiency is an adequate knowledge of the specialized field in which the experimental research lies. While necessary, this condition is not sufficient. Proper attention must also be given to the general principles of experimental design together with the modern methods for the analysis and evaluation of experimental data. The Present discussion is confined to a single design, the so-called "factorial" design. This design is of special interest in that it attains its goal, maximum efficiency, by directly departing from the

Jan 1, 1948

By M. K. Barnett

Engineering research consists, broadly speaking, in the investigation of the effect of the variations in a number of factors on some property of a product or characteristic of a process. The unambiguous description of the product or process requires that the property or characteristic be expressible in quantitative terms. For the purpose of practical control, it is likewise desirable that the independently variable factors governing the product or process be quantities, although this ideal goal is not always attained. Maximum efficiency—i.e., the attain- ment of the maximum amount of reliable, useful information relating to the influence of, the factors on the property of the product or characteristic of the process, for the least expense—is an important requirement for the satisfactory operation of a research organization. Obviously, a necessary condition for the attainment of maximum efficiency is an adequate knowledge of the specialized field in which the experimental research lies. While necessary, this condition is not sufficient. Proper attention must also be given to the general principles of experimental design together with the modern methods for the analysis and evaluation of experimental data. The Present discussion is confined to a single design, the so-called "factorial" design. This design is of special interest in that it attains its goal, maximum efficiency, by directly departing from the

Jan 1, 1948

By J. Stringer, I. W. Edington, C. R. Rarey

THE geometrical interpretation of transmission electron micrographs of hcp metals is more complicated than the equivalent interpretation of cubic metal for two reasons: firstly, prominent zone axes are not in general normal to prominent planes, so that a simple diffraction pattern often corresponds to a nonra-tional foil plane; and secondly, the Miller-Bravais sys-tem of indexing directions is not easy to visualize. In this, the indexing is referred to the Bravais four-axis system, and the direction is labeled [hkil], chosen so that and I are shown in Fig. 1. Some geometrical relationships useful for the interpretation of transmission micrographs have been calculated and are tabulated below: 6) Direction of the intersection of two planes; this is easily calculated by applying Condition 4 to both planes: a direction that lies in both planes is clearly their direction of intersection. Some of the above expressions have also recently been given by Otte and Crocker;' Expression 5 is of course in most standard crystallographic texts. It is generally considered easier and quicker to use graphical methods for the interpretation of electron micrographs than analytical methods. For this purpose, it is most convenient to use a "double stereo-gram" in which both the poles alzd the rational directions are plotted. It is, of course, necessary to orient

Jan 1, 1967

By H. W. Dow

Quite early in the beginning of the present century, hoisting equipment underwent a radical change, when electric motors were applied to furnish the power in place of steam engines. Naturally, in the beginning, motors were not employed for large hoists: most of them were small single-drum hoists for which the motor ran continuously and the drum was clutched in for hoisting by various methods, and the down-going trips were made on the brake. In 1911 the Nordberg Manufacturing Co. of Milwaukee built for the first time a double-drum hoist powered with a first-motion direct-current motor (Fig. I). This hoist embodied many of the features that are used on larger hoists today. In the early development of motor-driven hoists a more or less natural mis- take was generally made, which only recently is being corrected. Because the electric motor has a higher speed than the steam engine, mining people in general accepted, without question, the use of small-diameter drums and the resultant finding of the rope in multiple layers, which was not at that time, the general practice on first-motion steam hoists. Small-diameter drums can usually be driven by a motor through a single reduction of gears even with relatively high motor speed, therefore the complete equipment could be obtained with a lower first cost.

Jan 1, 1946

By Henry Faul

MEASUREMENT of radioactivity of rocks and ores has developed into a complete method of geophysical exploration. The problem falls into three natural categories: (I) surface radiation measurement in the field and underground; (2) radioactivity logging of drillholes; and (3) laboratory analysis of samples. Portable counters are used in the field for tracing radioactive formations and for quantitative estimates of radioactive content of surface rock. Wartime advances in battery design make it possible to construct small precision counters that can be carried easily. Even the smallest conventional diamond drillholes can be logged, and actual content of the radioactive element can be measured. The exact grade of very thin active layers or veins can be estimated only approximately. Samples may be analyzed for their alpha, beta or gamma activity, and beta assaying is the best suited to rapid routine operation. Simple calibration with standard samples is sufficient for rough work, but a density correction is necessary when greater precision is required. Samples with high emanating power should be fixed and stored for three weeks to reestablish the radium-radon equilibrium prior to precision assaying. Carnotite can be fixed by sintering or molding with plastics. Among the important new developments, a low-voltage Geiger tube has been designed recently, and crystal scintillation counters hold great promise for high-efficiency gamma-ray measurement.

Jan 1, 1947