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By Charles Macdonald

It may seem to be almost unnecessary to occupy the time of the Institute in further consideration of a question which has been so comprehensively treated in papers already on file in our own Transactions and in those of the American Society of Civil Engineers. Unfortunately, however, the results of these concerted efforts have not been materially to increase our stock of Knowledge in the direction sought for; and as the necessity for this information is becoming.more and more apparent as the demand for structural materials increases, it is believed that by continuing the agitation by means of discussions in this and kindred societies, whose members are vitally interested in obtaining reliable data as to the properties of the materials they are called upon to work with, public opinion may be educated up to the importance of exerting such an influence upon the law-makers of the country as will result in the formation of a competent board, with adequate means at its disposal, to carry out this great work in a manner alike acceptable to the makers and users of the materials in question. It may be proper in the first place to glance briefly at what has been attempted thus hr, then to indicate some of the more important lines of needed investigation, and finally to consider reasons why government aid may with propriety be sought for in carrying on the work. At a convention of the Society of Civil Engineers held at Chicago June 5th, 1872, it was, on motion of General William Sooy Smith, resolved, that, " Whereas, American engineers are now mainly dependent upon formula for the calculation of strength of the different form of iron and steel, not based on experiments upon American materials and manufacture; and " Whereas, There differ greatly in many of their ch~racteristics front thoae of foreign production, both in their nature and forma: therefore,

Jan 1, 1882

By Parke A. Dickey

POTENTIAL differences between strata of shale and sandstone have been recognized for about 15 years, and they form the basis of the electrical logging of oil wells. Hitherto these potentials have been ascribed solely to electrochemical reactions caused by the disturbing effects of the water in the drill hole through which they are generally measured. Observations by the author in wells empty of water and in a mine shaft suggest that potential differences between sandstones and shales are natural and specific properties of the rocks, although they are modified to measurement by the disturbing effects of the water in the drill hole. The cause of these potentials probably is to be sought in the relative polar adsorptive capacities of quartz and clay particles.

Jan 1, 1944

By Samuel M. Cassidy

The exact date of man's first use of coal is lost in antiquity. The discovery that certain black rock would burn was undoubtedly accidental and probably occurred independently and many times in the world over thousands of years. It is quite likely that these independent discoveries were made when primitive man chanced to build camp fires on exposed ledges of a black rock, then was amazed when it caught fire. The Chinese recorded the use of coal 1100 yearn before the Christian Era and from the Bible we learn that King Solomon was familiar with coal in what is now Syria. In Wales, there is evidence that the Bronze Age people used coal for funeral pyres, and it is known that the Romans used this fuel. There are other ancient references. So the knowledge that coal would burn, and even some uses of that knowledge, go back thousands of years. However, practical and consistent use of coal seems to date to England in the Middle Ages. COAL IN AMERICA In the Americas, there is evidence here and there of occasional use by the Indians. However, the first recorded discovery of coal, in what is now the US, was by French explorers, who reported an outcrop exposure on the Illinois River in 1679. Following this, other discoveries were made by French and British explorers, but the first recorded actual usage was in Virginia in 1702, where a French settler was granted permission to use coal for his forge. Earliest recorded commercial mining was in 1750, from the James River coaEeld near Richmond, VA, a deposit now abandoned. Besides local consumption from this field, shipments were made to Philadelphia, New Pork, and Boston. During the Revolution this coal was of impor- tance in the manufacture of shot and shell; so important, in fact, that the British sent an expedition in 1781 to destroy the iron works and

Jan 1, 1981

By H. S. Hanna, C. Rampacek

The problems and limitations encountered in the Physical beneficiation of the Appalachian Red Iron Ores are discussed. Two major problems are identified - the high phosphorus content and the fine dissemination or encapsulation of mineral impurities in the iron-bearing minerals. A process that combined extreme fine grinding techniques with magnetizing roasting or flotation-separation methods is suggested. By these methods, concentrates assaying 60-61 % Fe, exceeding the widely accepted upper limit of 56% Fe set for these ores, were produced with 75-90% iron recovery. Moreover, it was shown that the phosphorus content of these concentrates could be reduced from 0.25% to 0.03% phosphorus by acid leaching. A brief discussion on production costs based on current and future developments in iron ore processing is given.

Jan 1, 1983

By E. W. Edson, F. W. Hertal

In some fields the problem of mud fluid is simple and easy of solution. But in the Ventura Avenue field the acquisition and disposal of good drilling mud is not the least of the problems that confront the operator. In fact, mud fluid in the Ventura Avenue field is a very important factor in the drilling of the wells. It is quite probable that many of the factors affecting mud in this field will not be found in most of the fields with which the reader is familiar. However, in the fields where the mud fluid causes no apparent problem it is probable that some of the points brought out in this paper could be used to economic advantage. In fields where caving and squeezing formations and high gas pressures are present, as in the Ventura Avenue field, it is believed that application of methods outlined will be of great assistance in drilling wells. On account of the sandy nature of the formation and the lack of suitable shale bodies in the strata drilled through in the Ventura Avenue field, the wells make practically no mud during drilling. It is necessary therefore to supply drilling mud to the wells that will carry the drill cuttings to the surface, and also will " wall up" the drill hole and prevent the sandy formations from caving. Mixing and Handling Mud Fluid The clay used to make the mud fluid is obtained from a shale stratum in the upper Pico (Plioccne) formation found about a mile on either side of the field. Since high gas pressures and caving formations were first encountered in the Ventura Avenue field and mud fluid was needed to combat them, the mixing of this mud fluid has gone through a process of evolution. First, the clay was mined and hauled to the derrick, where it was shoveled into the well and left for the churning action of the bit to mix into a mud in the hole. The next move was the construction of a mixer to mix the clay to a mud fluid which was pumped into the well. These mixing

Jan 1, 1930

By Paul I. Eimon, Byron R. Berger

INTRODUCTION Epithermal silver-gold deposits form at low to moderate temperatures in near-surface environments. These deposits are found in all rock types, but historically, the most important deposits occur as veins in volcanic rocks (e.g., Creede, Colorado; Pachuca, Mexico) and as replacements in sedimentary sequences (e.g., Mercur, Utah; Carlin, Nevada). Increases in the open-market prices for silver and gold in the last few years have resulted in renewed interest in precious metals and the economic viability of large-tonnage low-grade deposits. These bulk-mineable deposits form as replacements in permeable horizons or as stockworks in the up- per parts of otherwise bonanza-type hydrothermal systems and newly recognized systems that erupted onto the surface as hot springs, fumaroles, or geysers. Large tonnage low-grade de- posits were an unconventional resource prior to price increases; however, now they constitute one of the main sources of precious metals in the United States and the importance is growing worldwide. This paper presents conceptual geologic- geochemical models of epithermal precious-metal deposits derived from studies of productive deposits throughout the world. Much of the data presented is not new. However, the interpretation of the data in terms of current concepts of hydrothermal processes is new. This paper deals with idealized and general ore-forming mechanisms, and no attempt is made either to explain the origin of the different chemistries of ore- forming fluids or to examine all of the variations in specific deposits due to local structural controls and host-rock compositions.

Jan 1, 1983

By Laszlo Valentyik, John T. Patton

A conventional heavy-media separation process utilizes a mixture of finely ground solids like magnetite, ferrosilicon, or shale and water. The always-present clay in the medium acts as a stabilizing agent since the coarse heavy-media solids would quickly sink if they were mixed only in water. As the pseudoplastic nature of polymer solutions has excellent suspending properties, laboratory investigations were conducted at the Institute of Mineral Research on whether polymers could be used as suspending agents for finely ground heavy media. The preliminary results (published previously) of the laboratory research studies have shown that sufficient stabilities of heavy media can be obtained at a relatively low polymer concentration. This paper is a continuation of the previous work and it presents some of the results of recent studies where the rheological properties of the heavy-media suspensions were studied in a newly developed settling tube and the already familiar concentric-cylinder-type consistometer. In the investigations bentonites as a stabilizing agent also were included so that comparative results would be available to the plant engineer to assist him in the choice of the most suitable material for stabilizing various heavy media.

Jan 1, 1977

By L. S. Chabot

INTRODUCTION THE bibliography of mining methods in the past few years has contained many articles dealing with the use of the diamond drill for blasthole drilling. In the Canadian mines, this method has been used with great success in stoping at Noranda, Aldermac, Waite Amulet, East Malartic and Sladen Malartic mines in the Province of Quebec. It has also been used at the Dorchester and Beattie gold mines in Duparquet, Quebec. The method has found useful application at Copper Mountain mine, British Colombia, and at Flin Flon mine in Manitoba. In the United States, the diamond drill blasthole method has been used at Cornwall Iron Ore Mines in Pennsylvania and at the Republic Steel Corporation magnetite properties in the Port Henry district of northern New York. In the Lake Superior iron district, the method has been used at the Anvil-Palms mine of Pickands, Mather and Co. at Bessemer, Mich., and is also used at the Book mine of the North Range Mining Co. at Alpha, Mich. Other companies in the district have also experimented in some degree with the method at some of their properties. This paper is being offered as a preliminary report on the use of the diamond drill method of stoping at the Book mine. Sufficient work has been done with it to prove its worth and it is the purpose of the article to present some results, operational details, equipment ideas and recommendations which we have found in its use at our mine. LOCATION AND DESCRIPTION The Book mine is situated about a mile north of the village of Alpha, in the NE-NE ¼ and the SE-NE ¼ of sec 12-42-33, between the Dunn mine and the Balkan-Judson mine, and about four miles southwest of the village of Crystal Falls, on the Menominee Range of Michigan. The property was found to have ore near surface in sufficient quantities for open-pit operations and stripping was begun in the latter part of 1942 to prepare it for ore production in 1943. During 1943, 288,447 tons of direct shipping ore were produced from the open pit and 382,933 tons in 1944. While the mine was being operated as an open pit some 350,000 tons of lean ore were stockpiled for later treatment. This material is being treated in a washing and jig plant and concentrates are produced during the shipping season. The ore bodies at the Book mine are characteristic of the Menominee Range. They are found on the flanks of sharply folded anticlines which have a fairly steep pitch to the northwest. The open-pit operations in 1943 and 1944 revealed two of these anticlinal structures. A detailed study and classification of the old diamond drill records, coupled with the information of some new holes drilled, has established the

Jan 1, 1947

By R. W. Raymond

The western public domain acquired by the United States through trcaties, as the result of conquest or purchase, was invaded after Marshall's re-discovery of gold in California, by an overwhelming multitude of prospectors and miners from all parts of the world. he mineral lands of the whole Pacific slope were practically unsurveyed. Congress, disgusted with the experiment of leasing mineral lands, which it had tried for 40 years, and abandoned in 1847, enacted no laws for the management of these public mineral lands, and the pioneers made their own laws governing mining titles. These local regulations applied at first to gulch-mining in the auriferous river-beds only; and they constituted a simple and practical system. adapted to the needs and means of primitive communities—significantly called " camps." They had the means of measuring distances, but not angles; they knew no property except personal property in the form of pickaxes, pans, supplies, camp-equipage, horses or mules, and mining rights. The earliest codes which they developed expressed what might be called the law of the lariat. With the lariat they measured the distance assigned to each miner along the gold-bearing gulch—a double portion to the discoverer, and a single portion to his successors, in the order of their coming. With the lariat, they hung, after such due process of law as was available, the rascal who stole a horse, or a bag of gold-dust, or a mining claim, or killed another man without giving him fair notice and a chance to defend himself. In these pioneer codes, adopted in mass-meetings and enforced by the same authority, two features concern us most: 1. They measured mining property by one dimension only. So many feet of the gulch, held by one man, meant a distance into either bank, and a distance in depth, extending as far as gold might be found.

Jan 1, 1915

ALTHOUGH the first colonists in the area that is now the United States, whether Spanish, French or English in nationality, were usually keenly interested in the possibilities of mineral wealth, it is a curious and interesting fact that none of them happened upon the mineral deposits that eventually were to make this the greatest mineral-producing country; up to 1800 it would probably have been rated as rather poor in minerals. Spanish explorers traversed the southeastern United States with- out finding the Appalachian gold deposits that aroused so much interest in the early nineteenth century; Coronado sought in vain for the seven golden cities of Cibola; and the important gold deposits of California were not discovered until the political sovereignty of the region had passed from Mexico, which had held it for three centuries. The French also held Canada for nearly two centuries (and the British for another century) without finding the mineral deposits in Ontario and Quebec that now are so important. Though they knew of the copper of the Keweenaw peninsula, the lead ores of Wisconsin and Missouri, and the coal of Illinois in the seventeenth century, these deposits were all too remote for exploitation. In the area held by Great Britain, iron smelting was planned at Jamestown as early as 1619 and was actually begun at Lynn, Mass., in 1643. The industry grew slowly, at first, but had reached considerable importance before the Revolution. Commercial bituminous coal mining began about 1750 in Virginia but anthracite mining in Pennsylvania was not started until 1800. As a result there was naturally little interest in the technical aspects of mineral production here before 1800 by any except the few people who were actually engaged in it. Students of natural science were much interested in minerals, however. The activities of those who rank as geologists are so thoroughly covered in

Jan 1, 1941

By Lewis Stockett

During the year 1903, a building having machinery corresponding to ail anthracite-coal breaker was erected at the town of Stockett, Cascade county, Mont., for the purpose of breaking-up and cleaning bituminous coal. The coal is mined from a vein of the Kootenai group of the Lower Cretaceous measures having the following section: The vein is nearly horizontal in position, and each bench differs in quality as shown in Table I.

Jan 1, 1905

Discussion of the paper of WALTER 0. SNELLING, presented at the New York meeting, February, 1915, and printed in Bulletin No. 100, April, 1915, pp. 695 to 704. A. F. LUCAS, Washington, D. C.-Are the results of the experiments in practical operation? WALTER 0. SNELLING.-There have been no large-scale operations up to the present. The necessary conditions of temperature are easily arranged for, but the required condition of pressure, 800 lb., is not so simple a matter. The company has been working on this problem, and at the refinery in Oklahoma work of this kind is now being carried on. The way in which an ordinary still will leak at 50 lb., and more at 100 lb., leaves some doubt in the mind of many as to what can be clone at a continuous working pressure of 800 lb. On the other hand, the fact that they are making ammonia abroad by a method which employs higher pressures and temperatures than anything involved in this method, leads me to believe that the difficulties, which will undoubtedly arise when this is attempted on a commercial scale, can be overcome. WILLIAM N. BEST, New York, N. Y.-Is there any change in the calorific value of these oils?

Jan 5, 1915

By E. J. Roberts, E. B. Fitch

Most classifiers in use today are, in function, settling pools. A fluid suspension of particles is passed through a pool at such a rate that only a fraction of the particles-the coarser fraction-has time to settle out of suspension. The rest are carried on out of the pool as overflow. The most fundamental way in which such classifiers differ is in the mechanism used to remove the settled particles from the pool. The particles may gravitate from the pool, as in the various sand cones, or they may be conveyed mechanically from the pool by drags, spirals, or reciprocating rakes. The mechanism of settling pool classification and its limitations are discussed. A method for calculating countercurrent classifications is presented. The practical validity of the calculation method has been confirmed through 20 years of use within The Dorr Co. During this time it has been used on diverse feeds and has been checked against many types of settling pool classifiers, with close agreement in nearly every case. Excellent elimination of third critical mesh particles and finer ones may be obtained in a countercurrent classifications series where all stages separate at the same mesh, but elimination of first and second criticals is inherently limited. Spectacular elimination of all criticals may be obtained by arranging successive stages to classify at successively coarser mesh. Improvement in elimination is obtained at the cost of an increased internal recirculation, but this may be tolerable in many cases.

Nov 1, 1956

By Warren L. Howes

This paper deals primarily with an investigation of ball-mill liners that was conducted by the writer over a period of six years at the Mammoth mill in Arizona. The investigation covered a wide variety of designs of liners in both primary and secondary mills. The comparative results are presented herein as evidence of the extent to which design influenced liner life and mill performance. Flowsheet The feed to the Mammoth mill was a complex, oxidized, gold-silver-lead-molybde-num-vanadium ore with rhyolite, andesite and granite as gangue. Although the ore varied between stopes, the long-term average in character remained substantially the same. Capacity was 560 tons per day.† Fig. I shows an abbreviated flowsheet of the grinding section of the mill. Primary Ball Mill A 3-ft. Symons shorthead crusher in open circuit crushed to 1/4-in. maximum one-way dimension the feed to the 5 by Io-ft. Marcy open-end ball mill. The mill rotated at 80 per cent of critical speed and was charged with 4-in. forged steel balls. Cast balls were used for a few months at a slight reduction in ball cost, but breakage of the large balls reduced the ball size and grinding capacity to a point where the over-all costs suffered out of proportion to the saving in cost of balls. For metallurgical reasons, the finished product of the mill was maintained at minus 8-mesh. This coarse product, plus the very abrasive ore and the absence of fines in the feed, caused abnormally rapid wear of the mill liners. The resultant high operating cost led to the most extensive phase of the investigation. In order to clarify the difference in design of the various types of liners used, Fig. a shows the profiles with the arrangement in which grinding balls of maximum size would lie on the face of the liners. The results with each type of shell liner in the primary mill are shown in Table I. Since most of the testing was done with

Jan 1, 1943

By Warren L. Howes

This paper deals primarily with an investigation of ball-mill liners that was conducted by the writer over a period of six years at the Mammoth mill in Arizona. The investigation covered a wide variety of designs of liners in both primary and secondary mills. The comparative results are presented herein as evidence of the extent to which design influenced liner life and mill performance. Flowsheet The feed to the Mammoth mill was a complex, oxidized, gold-silver-lead-molybde-num-vanadium ore with rhyolite, andesite and granite as gangue. Although the ore varied between stopes, the long-term average in character remained substantially the same. Capacity was 560 tons per day.† Fig. I shows an abbreviated flowsheet of the grinding section of the mill. Primary Ball Mill A 3-ft. Symons shorthead crusher in open circuit crushed to 1/4-in. maximum one-way dimension the feed to the 5 by Io-ft. Marcy open-end ball mill. The mill rotated at 80 per cent of critical speed and was charged with 4-in. forged steel balls. Cast balls were used for a few months at a slight reduction in ball cost, but breakage of the large balls reduced the ball size and grinding capacity to a point where the over-all costs suffered out of proportion to the saving in cost of balls. For metallurgical reasons, the finished product of the mill was maintained at minus 8-mesh. This coarse product, plus the very abrasive ore and the absence of fines in the feed, caused abnormally rapid wear of the mill liners. The resultant high operating cost led to the most extensive phase of the investigation. In order to clarify the difference in design of the various types of liners used, Fig. a shows the profiles with the arrangement in which grinding balls of maximum size would lie on the face of the liners. The results with each type of shell liner in the primary mill are shown in Table I. Since most of the testing was done with

Jan 1, 1943

By Stewart Coleman, Thomas W. Moore, H. D. Wilde

It is recognized that in the early days of the petroleum industry oil was produced with practically no scientific or fundamental knowledge of the laws and principles governing its extraction from the ground. Only a few, if any, of those exploiting the oil resources made any effort to collect accurate scientific information. There was little need for it, for as is frequently the case where the supply of a natural resource appears inexhaustible and is greater than the demand, large profits were possible from merely skimming the surface with little regard to the efficiency or thoroughness with which the oil was obtained. With this policy in force, great quantities of gas were wasted and when the reservoirs ceased producing by natural means they still contained a large fraetion of the oil originally in them. The present tendency in the industry is toward conserving existing oil reserves. In order that greater percentages of the oil present in the ground may be recovered, efforts are being made to improve production methods and to rework depleted fields. If the production methods are to be improved intelligently it is essential that the fundamental laws be known and understood, consequently large amounts of money and effort are being spent in gathering data that will serve to define and interpret these laws. A great deal of attention is being focussed on the study of the motion of oil through an oil-bearing sand, the forces that cause it to move and the factors that affect its motion. It is recognized that one of the important factors is pressure, but its quantitative effect is not known. In a given field the rate of production declines with time and so does the rock pressure. Furthermore, a comparison of different fields shows, as a

Jan 1, 1930

By George H. Ashley

The present critical state of the supply, distribution, and utilization of coal and the necessity for pooling and zoning coals calls renewed attention to the lack of any fully adequate classification of coal. In the past coals have been classified as anthracite, semianthracite, semibitumi-nous, bituminous, subbituminous coals, and lignite, and a few special types, such as splint coal and cannel coal. But under the term bituminous coal are included a great variety of coals differing markedly both physically and chemically. The term subbituminous coal covers as great a range of chemical differences. In order to distinguish these varieties of bituminous coals it has been customary to designate coal by names derived from the place where mined, or by the name of the bed from which it is mined. Thus, in the market reports, coals are quoted as Pocahontas coal, New River or Sewell coal, Moshannon coal, Ohio coal, Williamson County coal, Jellico coal, and so on indefinitely, no limit being set as to the boundaries of the area to which a given name is applied. Nor is there any scale by which the coal from one place may be compared with the coal from some other district or some other bed. On the one hand, coals from the same district may be quite distinct and sell at very different prices or coal from the same bed may differ greatly in different districts; on the other hand, coals from different states may be so similar physically and chemically that one could replace the other in practical use without any appreciable difference in service. The following classification, arrived at after a careful review of a large number of systems of classification and of all of the recognized characteristics of coal, brings together all coals that so nearly resemble each other physically, chemically, and in heating qualities that any coal of a given type could replace any other coal of the same type and grade in use. Thus, if coals A and B are classed as of the same type and grade they have, so far as known to the writer, approximately the same heating value when burned under the same conditions, and the same character, length of flame, and properties affecting transportation and stocking; and if of the same grade, approximately the same percentage of impurities.

Jan 1, 1920

By Peter L. Swanson

A microcrack process zone is frequently suggested to accompany macrofractures in rock and play an important role in the resistance to fracture propagation. Attenuation of surface waves propagating through mode I fractures in wedge-loaded double-cantilever beam specimens of Westerly granite has been recorded in an attempt to characterize the structure of the fracture process zone. The ultrasonic measurements do not support the generally accepted model of a macroscopic fracture that incrementally propagates with the accompaniment of a cloud of microcracks. Instead, fractures in Westerly granite appear to form as gradually separating surfaces within a zone having a width of a few millimeters and a length of several tens of millimeters. A fracture process zone of this size would necessitate the use of meter-sized specimens in order for linear elastic fracture mechanics to be applicable.

Jan 1, 1984

By R. S. Shoemaker, F. W. McQuiston

CAMPBELL RED LAKE MINES Balmertown, Ontario 1974 Operating Data MINE LOCATION: Balmertown, in Red Lake mining area of Ontario TYPE OF MINE: Underground mine developed by vertical shaft to 4300 feet. Mining active above 3000 ft depth. ORE DESCRIPTION: Gold and minor silver.. Sulfur content about 1.3%. Ar senopyrite , pyrite, pyrrhotite, and stibnite. CAPACITY IN TONS124 HRS: 825 ASSAY: 0.66 oz Au per ton heads MILL PROCESS: Amalgamation, flotation, roasting of concentrate and separate treatment of calcines and flotation tails by cyanide. PLANT BUILDING: Mine mill and service facilities all housed in insulated and heated buildings POWER: Total consumption, mine and mill - 100 Kwh/T WASTE DISPOSAL: Impoundment of tailings. Arsenic to sealed underground storage EMPLOYEES: Total of 300 men on payroll. Housing in Balmertown and nearby communities.

Jan 1, 1975

By Frederick M. Becket

DoctoR Albert Sauveur, distinguished scientist and Honorary Member of this Institute, predicted in the first Howe Memorial Lecture that the privilege of delivering' this annual address would be considered a highly significant honor. The intervening years have well borne out Sauveur's prophecy. I wish to assure the American Institute of Mining and Metallurgical Engineers that I also deeply appreciate this honor, recognizing at the same time the present and even more the future responsibilities with which it is accompanicd. Several of the previous lecturers had the good fortune to attend the classes of Professor Howc and to work in his laboratories. I was similarly favored, although in my instance and to my great regret the period was all too short. However, Howe's book, published in 1903, "Iron, Steel and Other Alloys," afforded me abundant opportunity to continue these studies. How well I remember the inspiration I derived from this famous book by Howe, the metallurgical master, pioneer, and educator! Remembering that Professor Howe contributed numerous papers to The Metallographist, a magazine supported from a technical point of view by the world's pioneers in metallography, I was curious a few days ago to learn the nature of Howe's early contributions to this magazine. The first paper by Howe in the first year of The Metallographist (1898) dealt with the allotropic theory; the second also treated of allotropy, and I quote the first sentence of that paper: The allotropic theory of the hardening of steel may, like so many other important theories, have to be accepted or rejected not on direct proof or disproof, but on the accumulation of circumstantial evidence for or against it. Howe's ability to stimulate others by his deep understanding and clarity of expression was truly remarkable; but just as striking was his intuitive judgment concerning the implications of metallurgical data in the arts and scienees. It therefore seems fitting that this lecture comprise a broad treatment of the subject chosen, rather than a closely documented thesis on any one phase of the problem; that in it attention be focused

Jan 1, 1938