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By C. E. Wethered

THE Morning mine is operated through one main working adit, known as No. 6 or 800 tunnel level. At a distance of 10,000 ft. underground from the portal is the vertical four-compartment, main working shaft, which extends to the 3050 level, a distance of 2250 ft. below the collar, or 800 level. Shaft-stations are cut and levels opened every 200 ft. of depth and the ore is stoped to the next level above. The vein is nearly vertical and the ore is usually fairly massive and brittle. Both walls are soft and slabby and much difficulty is therefore experienced in holding them. Stopes are usually carried up in short sections, approximately 200 ft. in length, that are mined as rapidly as possible in order to avoid a too great replacement or repair of stope timbers. The four-compartment vertical shaft, 110 ft. in the footwall of the vein, is the sole medium of outlet for all ore mined below the adit level. Two compartments of this shaft are used exclusively for hoisting ore, except at the time of changing shifts, when one compartment is used to handle some of the men and timber. The third compartment is equipped for handling men, tim-ber and all general supplies and is operated by a Nord-berg 300-hp. electric hoist. This hoist has a lifting ca-pacity of 14,000 lb. with an average rope speed of 800 ft. per minute. The fourth compartment is used solely as a manway and pipeway.

Jan 7, 1927

By R. P. Carreker

GERMANIUM is a member of that group of ele-nents—carbon, silicon, germanium, and tin-— that are currently of particular interest because of their interesting electrical properties. Near room temperature these materials of diamond cubic crystal structure are characteristically brittle. However, there have been several recent reports that germanium is not brittle at elevated temperatures These observations may be summarized as follows: 1—Germanium single crystals were observed to creep in bending under a maximum fiber stress of 6 kg per mm&apos; (8500 psi) at 500°C and above.&apos; The creep curves were sigmoidal, with an induction period that decreased with increasing temperature. 2—Germanium crystal bars have been bent 90" about radii ten times the bar thickness at 550°C.&apos; 3—-Audible clicks were heard when l/4 in. thick crystals were bent drastically at 450" to 500°C. No microstructural evidence of mechanical twinning was observed 4—Slip lines have been observed in tensile specimens deformed at 600°C, and are coincident with (111) planes, the close-packed planes of the diamond cubic structure.] The slip direction has not been established. 5—A germanium crystal has been compressed approximately 20 pct along a <110> axis at 700°C." The results reported subsequently were obtained in exploratory experiments intended to indicate some aspects of the behavior of germanium single crystals when tested in simple tension. Specimen Preparation A single crystal bar of n-type germanium was used. It was of purity corresponding to a resistance range of 2 to 20 ohm-cm. Tensile specimens were prepared by cutting small rectangular bars

Jan 1, 1957

By F. A. Forward, J. Halpern

A new process is described for extracting uranium from ores containing sulphidic minerals, which comprises treating an aqueous pulp of the ore with air or oxygen at elevated temperatures and pressures. The acid required to dissolve the uranium is generated during the leach through oxidation of the sulphides. The chemistry of the process is discussed and laboratory results are presented to illustrate the operation of the method and the variables which control it. With most ores, leaching at a temperature of 130°C and an oxygen partial pressure of 10 psi provides uranium extractions of 90 to 95 pct in 4 to 6 hr. The acidity and level of dissolved impurities in the leach liquor can be kept fairly low. The method is characterized by a number of advantageous features including low reagent cost, short retention times, and high recoveries. RECENTLY there have been developed several processes for extracting metal values from ores by pressure leaching techniques;&apos; -&apos; an example is the carbonate leaching process for uranium ores which has been studied in this laboratory.&apos; Leaching is carried out under oxygen pressure to ensure oxidation of the uranium to hexavalent compounds which are soluble in carbonate solutions. During the course of investigations relating to this process, it was observed that sulphide minerals, such as pyrite, usually were oxidized under the conditions of the leach treatment resulting in the formation of iron hydroxides and sodium sulphate, i.e. 2 FeS= + 7Vz O2 + 8 Na,CO3 + 7 H,,O -* 2 Fe(OH)3 + 4 Na2SO4 + 8 NaHCO.,. [1]

Jan 1, 1956

By C. A. Heberlein

C. A. HEBERLEIN, New York, N. Y.-The results stated by Rey and Brevers are so startling that they are of great interest, as the concentration of a low percentage of cinnabar by differential flotation yields a high-grade concentrate in the presence of either arsenical or iron pyrite. The authors say: "Cyanide can thus be used to depress arsenopyrite and make a good cinnabar-arsenopyrite separation. A cinnabar-pyrite separation could probably be effected in the same way." Corrosive sublimate at the present price of mercury would be a very expensive reagent but the expense would be justifiable if a high rate of concentration could be obtained with a high extraction. On my request, special tests were made in the Punitaqui mill in Chile along the line suggested by the authors, without any improvement of either grade or extraction. As the recovery of the cinnabar in a complex sulphide of chalcopyrite and pyrite gave unsatisfactory results, I had tests made at the testing laboratory of the American Cyanamid Co. at Stamford, Conn. As these tests turned out to be highly satisfactory, not only at Stamford but later at the mine, they are presented here. [ ] The pulp had a density of 22 and a pH of 7.8. Total time of conditioning was one minute. The reagent added was Texas fuel oil, 0.116lb. of 33.7 Bé. gravity containing 0.9 per cent sulphur. Frother, 0.062 lb. of No. 5 pine oil. Rate of concentration of mercury was 25.7: 11. [ ]

Jan 1, 1941

By A. M. Ross

DEURING the past year the uranium milling industry has seen the installation and initial operation of solvent extraction circuits in the Climax Uranium Co. mill at Grand Junction, Colo.; the Kerr-McGee Oil Industries mill at Shiprock, N. M.; and the AEC pilot plant at Grand Junction, operated by National Lead Co. Inc. The Vitro Uranium Co. mill in Salt Lake City is converting to solvent extraction, and the new Union Carbide Nuclear Co. mill to be constructed at Rifle, Colo., will also employ this method. Solvent extraction circuits will be incorporated in two mills now under construction -the Texas Zinc Minerals Co. mill at Mexican Hat, Utah, and the Gunnison Mining Co. mill at Gunnison, Colo. In Canada the expansion of the Eldorado mill at Port Radium includes installation of a solvent extraction circuit. Solvent Extraction Process: In simplest terms, the organic solvent is mixed with leach liquor and then the organic and aqueous phases are allowed to separate. By this contact the solvent selectively extracts uranium from the liquor, leaving a raffinate, or barren leach liquor, which may be discarded. The pregnant solvent is stripped of its uranium by con- tact with a stripping solution, such as aqueous sodium carbonate, which has a greater affinity for uranium than the solvent does. The barren solvent from the stripping step is available for further leach liquor extraction, and the pregnant stripping solution, which usually contains 30 to 60 g U3O8 per liter, is ready for precipitation of a final product, or uranium concentrate.

Jan 9, 1957

By Friedrich Wellmer

INTRODUCTION The Ramsbeck Pb/Zn Mine is located in the northern Sauerland area of West Germany, 150 km N of Frankfurt and 120 km E of Cologne. This is a vein deposit which has been worked from the middle of the 19th century to 1974. About 15 million tons of ore were mined and milled. The ore district contains several vein deposits and is roughly 14 km in length and 4 to 5 km in width. The host rocks are strata of Lower Middle Devonian age. The strata strike 60° to 70° NE and where overturned have a dip steeper than the veins (Fig. 1). The galena-sphalerite mineralization is in quartz veins, which are mineralized where they cut the "Main Ramsbeck Quartzite" horizon, a very competent host rock. Vein structures strike at 65º to 75º, dip about 20° to 25º SE and cut the quartzite at approximately 60 m intervals. The main or "steep veins" within each vein structure dip at 10º to 80° SE with an average of 30° and are offset by thrust faults dipping 5º N to 40° S with an average of 5º S. "Flat veins" usually weakly mineralized occur in the thrust faults between the "steep veins", thus forming the overall step-like vein structure. The mineralization is very irregular and changes a- long strike and down dip. It consists of thin veins of pure sphalerite and galena with quartz and pyrite. The thicknesses of the pure sphalerite and galena veins

Jan 1, 1977

By Jan M. Mutmansky

A knowledge of rock characteristics forms the foundation for the application of rock mechanics to engineering works. Hence, there has been an increased interest in the determination and proper utilization of rock properties data. Most numerical values quoted for rock properties are obtained from arbitrary tests and are not necessarily indicative of any intrinsic rock characteristics. Recent attempts to correlate these properties by statistical methods have attracted considerable attention, in the hope that these might give some clue to the fundamental properties. To date, correlation and regression techniques have been employed for this purpose. The use of statistics has also been deemed appropriate because of inhomogeneity and anisotropy in rocks. The problems have been further compounded by the lack of standardized methods of measuring rock properties. The various ASTM committees are still deliberating on these matters, but recommendations should be forthcoming in the near future. As more reliable data become available, the ability of geoscientists to find more meaningful relationships between rock properties will be greatly enhanced. The objective of this paper is to outline another statistical technique which might be useful in providing an insight into the relationships that exist between rock properties. This method does not attempt to predict rock characteristics, but rather compares the similarity or dissimilarity between properties. This enables rock properties to be classified into groups with similar intrinsic characteristics. The technique described is one form of factor analysis. It allows the results obtained to be depicted geometrically, so as to make ready visual examination possible.

Jan 1, 1968

By Claus Guenter Goetzeil

(New York Meeting, February, 1937) The object of this investigation was to determine whether silver alloys could be used instead of the currently employed insert of high-expansion Average Coefficient per Deg. C. over Range 20° to 200° C. Pure aluminum..................................... 24.6 X 10-6 Cast low-expansion Si-Cu-Ni-A1 piston alloy............ 20.0 X 10-6 High-expansion austenitic Cu-Ni cast iron.............. 19.3 X 10-6 Cast steel (0.25-0.35 C, 0.40-1.0 Mn).................. 12.6 X 10-6 Cast iron (3.15 total C, 2.16 Si)....................... 12.8 X 10-6 Pure silver.......................................... 18.9 X 10-6 austenitic ferronickel alloy, to reduce the wear of ring grooves in light metal pistons. A typical example of a piston containing a ferronickel insert is shown in Fig. 1. The high coefficient of expansion of silver made it worthy of consideration, while the small size of the insert would render its use feasible in Germany as an emergency measure. The coefficients of linear expansion of several metals and ailoys are as shown in the table above. Obviously the melting point of the insert must be high enough to prevent it from melting when the light alloy is cast around it. This imposes a lower limit of about 850" C. for the solidus of the silver alloy. Pure silver melts at about 961" C., so that the tolerable depression in the solidus is rather small. To avoid deformation of the insert during use a Brinell hardness number of at least 60 appears necessary.

Jan 1, 1937

By Charles M. Cooley

THE continual improvements in. the two extremes of the drilling, unit, the drill and bit, have prompted critical examination of the drill steel, the weak link of this drilling unit. Obviously, little is to be gained from the betterment of the drill and bit if the drill steel which transmits the force needed for drilling from the machine to the bit cannot stand long hard service. The technology of the bit has advanced from the integral type to steel detachables, thence to the tungsten carbide insert. The carbide insert is the most significant advance in the bit, bringing it to the level of a machine tool with its performance records under constant surveillance. Long steel changes have become advantageous because the carbide bit will drill greater footages without replacement than did the steel bit: The development of the tungsten carbide insert opened new fields of endeavor in drilling with percussion drills here- to fore known, but limited by the steel bit. After the introduction of the tungsten carbide bit, drill manufacturers began promotion of long feed shells, lighter drifters and stopers, and easily handled auxiliary equipment. Ultimately this promotion of better equipment was intended to increase the bit-against-rock time of the drill shift. Advantages of the uninterrupted drilling period of a long steel change and faster setup time of lighter drill machines are lost when the shank fails in the machine, rod failure requires continual changing, or the bit breaks off in the hole. The quest for reduced

Jan 1, 1952

By Hans Haalk

PRACTICAL or applied geophysics-as we designate the border region between physics and geophysics on one hand and practical geology on the other-has as its object the application of physical or geophysical methods of investigation to problems of practical geology. Its field of operation comprises all methods of physical measurement that are used in the problem of determining, from the geophysical influences of the subsoil that can be measured at the surface of the earth, the special characteristics of the association of strata, faults, etc., to detect the presence of deposits and to investigate underground structures. It therefore repre-sents an aid, a physical method of research in practical geology, and is inseparably connected with geological studies; for this reason, it is also called geophysical prospecting. Formerly research methods of practical geology were based on observation exclusively: first, on the observation of the strata and formations at accessible parts of the surface of the earth, especially in shafts, borings and mines if such were available; then on the observation of the tectonic conditions in so far as these were already known at places directly visible; and finally, by estimation of the importance of formations of the terrane. Later, there were added in special cases, analytical chemical crystallo-graphical, petrographical and similar investigations of rock samples which were taken from the places under consideration. The knowledge thus obtained is of value and is expanded by hypotheses and constructions that are supported by geological theories of origin and by laws of the sequence of formations and rock systems, which are based on long experience.

Jan 1, 1928

By Hans Haalck

PRACTICAL or applied geophysics-as we designate the border region between physics and geophysics on one hand and practical geology on the other-has as its object the application of physical or geophysical methods of investigation to problems of practical geology. Its field of operation comprises all methods of physical measurement that are used in the problem of determining, from the geophysical influences of the subsoil that can be measured at the surface of the earth, the special characteristics of the association of strata, faults, etc., to detect the presence of deposits and to investigate underground structures. It therefore represents an aid, a physical method of research in practical geology, and is inseparably connected with geological studies; for this reason, it is also called geophysical prospecting. Formerly research methods of practical geology were based on observation exclusively: first, on the observation of the strata and formations at accessible tarts of the surface of the earth, especially in shafts, borings and mines if such were available; then on the observation of the tectonic conditions in so far as these were already known at places directly visible; and finally, by estimation of the importance of formations of the terrane. Later, there were added in special cases, analytical chemical crystallographical, petrographical and similar investigations of rock samples which were taken from the places under consideration. The knowledge thus obtained is of value and is expanded by hypotheses and constructions that are supported by geological theories of origin and by laws of the sequence of formations and rock systems, which are based on long experience.

Jan 1, 1928

By Hans Haalck

PRACTICAL or applied geophysics-as we designate the border region between physics and geophysics on one hand and practical geology on the other-has as its object the application of physical or geophysical methods of investigation to problems of practical geology. Its field of operation comprises all methods of physical measurement that are used in the problem of determining, from the geophysical influences of the subsoil that can be measured at the surface of the earth, the special characteristics of the association of strata, faults, etc., to detect the presence of deposits and to investigate underground structures. It therefore represents an aid, a physical method of research in practical geology, and is inseparably connected with geological studies; for this reason, it is also called geophysical prospecting. Formerly research methods of practical geology were based on observation exclusively: first, on the observation of the strata and formations at accessible parts of the surface of the earth, especially in shafts, borings and mines if such were available; then on the observation of the tectonic conditions in so far as these were already known at places directly visible; and finally, by estimation of the importance of formations of the terrane. Later, there were added in special cases, analytical chemical crystallo-graphical, petrographical and similar investigations of rock samples which were taken from the places under consideration. The knowledge thus obtained is of value and is expanded by hypotheses and constructions that are supported by geological theories of origin and by laws of the sequence of formations and rock systems, which are based on long experience.

Jan 1, 1928

By Zay Jeffries

IMAGINE a spinning sphere of hot matter about 8000 miles in diameter, rushing through space at a velocity measured in miles per second, and you have a rough idea of what our earth is supposed to have been like about two to four billion years ago. By applying all of the science known to man and, more especially, by determining the velocity of earthquake waves at different depths, making comparisons with meteorites, studying densities, compressibility of rocks and the nature of surface rocks, a fairly definite conception of the general constitution of the earth has been obtained.1 The earth is supposed to have a central core rich in iron containing a substantial amount of nickel and small percentages of several other elements. The density of the core is assumed to be about ten times that of water and the diameter about 4200 miles. An intermediate shell of density about 4, and thickness of about 1800 miles, is sup- posed to consist of heavy rocks including sulfides, oxides, and silicates. The outer rock shell, probably about 100 miles thick and with a density around 2.8, is thought to be composed mostly of silicates, becoming in general more siliceous as the earth&apos;s surface is approached. NATURE&apos;S SMELTING OPERATION Nature seems to have subjected the earth to a stupendous smelting operation, burying beyond reach much of the metal that man recovers in his smelting practices. We live on the surface of Nature&apos;s "slag dump" and must be content, for the near term, to recover for man&apos;s

Jan 1, 1953

By Teder R. I., M. M. Protodyakonov

In order to find an empirical relation between a quantity F and (m) independent variables or factors, each of which take (n) different values or levels, it is necessary to conduct nm different experiments (all possible combinations of the factors), each of which has to be repeated a few times (usually five) due to the scattering of the data. The total number of such experiments is very large, thus for example, when m = 4 and n = 5, it is equal to 5.54 = 3125; and very rarely is it possible to conduct such a number of experiments. Various possible methods of planning partial experiments are illustrated in Fig. 1. Each method shows a large combinative square consisting of five columns and five rows of middle squares, each of which, in turn, is further divided into five columns and five rows of cells. Such a partition corresponds to a plan of an experiment with four factors, each of which takes five different levels. The blackened cells indicate the combination of factors in a partial experiment. The total number of experiments is reduced on the basis of the following considerations: a) The effect of only a few levels of some factors is studied (Fig. la). Such an investigation gives no information on the effect of some factors, therefore it cannot be accepted as satisfactory; b) By reducing the number of levels of each factor; in such a case it is not possible to obtain an empirical relationship, but only whether some factors have an effect. This is evidently inadequate;

Jan 1, 1971

By James Norman

SPODUMENE is a lithium-bearing pyroxene, and is an important source of lithium compounds. Because of its high alumina and lithia content it might be a desirable constituent of glass batches. The use of spodu-mene in ceramics will undoubtedly increase, as it has been shown that a mixture of the proper proportions of this mineral with soda feldspar and potash feldspar has a much lower maturing temperature upon firing than has any one of the three components.1 The mineral spodumene seldom occurs as pure mineral, but ordinarily with feldspars, mica and quartz. All spodumene-bearing rocks tested contained these minerals as gangue. Small amounts of iron and manga-nese oxides also were present, usually as stains on the silicate grains. Mica associated with the spodumene carried a considerable amount of lithia. This was discovered in flotation tailings, which, although virtually free of spodumene grains when examined microscopically, showed 0.4 to 0.5 per cent Li20 on chemical analysis. The lithia content of micas picked from the North Carolina spodumene rock was variable. Some samples contained little lithia, others more than 3 per cent. In 1938, under the supervision of Oliver C. Ralston, ? the Bureau of Mines, in cooperation with the Tennessee Mineral Products Corporation, undertook to study the beneficiation of North Carolina spodumene by froth flotation. The Bureau had previously published investigations on the beneficiation of spodumene.2,3 The methods described in the second publication&apos; did not give good results with badly weathered spodumene rock, so that more thorough investigation of the subject was warranted.

Jan 1, 1940

By W. D. Klopp, R. I. Jaffee, H. R. Ogden, D. J. Maykuth

The purification of commercial-purity tantalum powder by vacuum sintering in the temperature range 2600° to 2860°C has been investigated. Mixtures of tantalum oxide and tantalum carbide were sintered at 1800° and 2200°C. Tantalum bars containing 1 pct additions of oxygen, nitrogen, and carbon. were sintered in the range 1800° to 2600°C. Anulyses were conducted on the sititeyed mixtures to determine the extent of removal of oxygen, nitrogen, and carbon at each sintering condition. The mechanism for remova1 of each impurity, and the conditions necessary for preparing ductile tantalum by vacuum sintering are discussed. INTEREST in the refractory metals has been stimulated in recent years by the need for structural materials capable of operating at temperatures of 1100°C and higher. These metals include columbium (niobium) (mp 2468°C), molybdenum (mp 2620°C), tantalum (mp 2996°C), rhenium (mp 3160°C), and tung- sten (mp 3415°C). In addition to its high melting point, tantalum possesses the advantages of forming a solid, nonvolatile oxide at temperatures of interest and of being ductile and easy to fabricate. The classic method of consolidating tantalum from powder refined from the ores is by vacuum sintering at temperatures on the order of 2600°C. This sintering treatment both densifies the compacted powder bars and purifies the metal by causing impurities to boil out. The present work was undertaken to provide more quantative data on the relationship between sintering conditions and purity and to determine the mechanisms of impurity removal.

Jan 1, 1961

By C. W. Davis, R. S. Dean

AMONG naturally occurring inorganic compounds, magnetite has many unusual and interesting properties, and it is the purpose of this paper to call attention to these properties and review possible uses of magnetite that might be based on them; in other words, to see what uses may be found for magnetite as a physical rather than as a chemical entity, as a mineral rather than as an iron ore. The Mineral Physics Studies initiated in the Metallurgical Division of the U. S. Bureau of Mines a few years ago gathered together much information on mineral properties, and they are therefore the principal source of material for this paper. Magnetic Properties Of Magnetite And Possible Uses As A Magnetic Material Magnetite is unique among minerals for its great magnetic susceptibility, approximately one-third that of soft iron, and some magnetites are permanent magnets, or lodestones. The literature contains many measurements of magnetic properties of individual magnetite crystals, but no systematic survey of the effect of mechanical preparation and heat-treatment was available until the recent investigations of the Bureau of which included not only susceptibility but coercive force and remanence as well. For the purpose of orientation, Table 1 gives the magnetic properties of several samples of magnetite and of a few other substances3. This table indicates that when ordinary magnetite is powdered it decreases in susceptibility and increases in coercive force and remanence, approaching the properties of lodestone. The properties of lodestone are in fact probably due to the development of very large internal surface on fine grain size4.

Jan 1, 1937

By H. M. Howe

It is a grave objection to the present system (or rather lack of system) of mineralogical nomenclature that, in the very great majority of cases, the name of a mineral gives no hint of its chemical composition, one might almost say no suggestion, however faint, of anything connected with it or characteristic of it, chemical, physical, historical, geographical, geological, or lithological. In becoming acquainted with a mineral, in addition to learning its composition and important characteristics, one must also learn a name wholly unconnected with any of them. It has occurred to me that a system might be devised in which the name of each mineral should express at least an approximation to its ultimate composition. It is far easier to learn the names of most minerals than their compositions. Most of us are familiar with the names and appearance of many minerals, especially among the silicates, of whose compositions we have but a rough notion. It would be the aim of such a system to enable us, in making the one slight effort of learning the name of a mineral, by that same effort and involuntarily to learn its composition, which now requires an additional and a much greater effort. I have worked out a system designed to meet this requirement, and its description occupies the remainder of this article. Doubtless there are many devices on which could be based other systems fulfilling the requirement above set forth better than that about to be described does, and at the same time furnishing names

Jan 1, 1884

By E. D. Gardner

APPARENTLY the widespread agitation for the codification of our mining laws has had its effect, and it is quite possible that Congress will take up the question during this present session. The greatest objection to our present statutes pertaining to metalliferous deposits seems to be directed against the law of the apex. Those who are not in favor of changing this law are very far in the minority and they apparently realize that it is useless to urge its retention. Next in importance to the repeal of the law of the apex, seems to be a widespread advocacy for the repeal of the law requiring discovery of mineral before a valid location of a mining claim can be made. To a lesser extent there appears to be a desire to have the law changed so as to allow patent for claims without mineral discoveries. The purpose of this article is to review the arguments in favor of the proposed change of the discovery requirement, to show some of the evils that may be expected to result therefrom, and to consider whether a system may be devised to correct the undesirable features of the present law in this respect and at the same time not expose the mining fraternity and the general public to the evils which would result from the repeal of this fundamental requirement. Under the law as at present framed, the validity of a mining location is dependent upon the fact of discovery of mineral within the boundaries of the land claimed.

Jan 9, 1916

By Joseph Pogue

IN 1920, 531 million barrels of crude petroleum were consumed in the United States. As imposing as this figure is, the fact that the domestic consumption of crude petroleum has increased at an average rate of 10 per cent. a year for the past decade is more striking. Will this rate of increase in demand continue? If so, the year 1930 will call for 1260 million barrels of petroleum-a staggering volume. On the other hand, may we expect the demand for petroleum to grow as rapidly as it did when the automotive industry was having its most phenomenal expansion? If not, to what extent will the growth of oil requirements decrease? When and to what degree will the petroleum industry become affected by the economic law of diminishing returns? Obviously, this matter requires careful analysis, especially as both national and industrial planning must be predicated upon present estimates of the requirements of the future. The purpose of this paper, accordingly, is to project, as closely as present limitations of knowledge permit, the course of the demand for petroleum in the United States over the next ten years. At first, the problem of estimating the future of a demand as complex as that for petroleum might appear insoluble. Fortunately, however, there are several scientific methods of approaching the problem, centering around a study of rates of industrial growth, which lend considerable hope that the requirements of the immediate future in this field may be approximated with sufficient closeness to have practical value as a basis of action.

Jan 3, 1922