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Jan 1, 1894

By Hewitt Wilson

IN 1903, T. M. and E. H. Alvord, of Marblemount, Wash., built a soapstone-grinding mill in the Skagit River Valley and are reported to have produced "ground talc" during 1904 and 1905, shipping to the paper mills in Wisconsin. Between 1916 and 1920, the Western Talc Co. built and operated a talc-grinding mill north of Mondovi, on the banks of the Spokane River, in eastern Washington, and sold powdered talc to the Inland Empire Paper Co. of Spokane. ? The most active develop-ment in recent years has been by two companies in the Skagit Valley-the Skagit Talc Company, Inc., which has been sawing soapstone block for the soda-recovery furnaces of the pulp and paper companies, and the Asbestos-Talc Products of Washington, Inc., at Burlington, which has been mining and dry-grinding a soft serpentine for the structural filler and insulation trade. Many prospects have been opened in the northern part of the state on both sides of the Cascade Mountains, and these activities undoubtedly are the forerunner of an industry that promises to attain considerable magnitude in the North Pacific States. At the present time, talc is imported from California for use as paper filler, and soapstone block from Virginia for use in the soda-recovery furnaces. A small market has been created locally for tailor and foundry:, pencils, stove grills, and block soapstone for art objects. The results of the present study, as yet incomplete, indicate that the use as a refractory and as a ceramic filler and flux can be expanded.

Jan 1, 1936

By Charles W. Eichrodt

So much has already been wimitten on this vast subject of ground movement and subsidence, and so many data collected and commented upon, that in this paper the author proposes to confine himself to the submission of some plans showing what has actually occurred in the mining of several of the orebodies which have come under his direction during the last 20 years or so at Rio Tinto, Spain. Some notes are added for the purpose of describing the plans. The author does not attempt to give his opinion as to the reasons why the subsidences have occurred in the manner in which they are found, but confines himself to giving as true a picture as possible of the movements that have taken place. Effects of Excavation on Ground Movement Broadly, the effects of excavations on the overhead or adjacent ground can be classified under three headings, as follows: 1. Ground movements due to excavations made from surface only, such as those made in opencasts where no excavations underlie them. The stability and strength of the ground to resist movement must determine the slopes. 2. Ground movements due to underground excavations only; i. e., where the surface is not removed. 3. Ground movements due to a combination of both; i. e., from excavations taking place from the surface for the purpose of stripping an orebody and recovery of the ore to a certain horizon combined with excavations being carried out below, at the same time, for the winning of the ore below the horizon at which mining by stripping or opencasting under the specific conditions is no longer economical. Nos. 1 and 2 represent independent and distinct problems and No. 3 is a combination, which presents results much more difficult of explanation. The accompanying plans and sections give examples of what has occurred under the three conditions. Unfortunately, the class of ground is not exactly the same in them all, but the difference is not greater than is generally encountered over districts of equal area. Excavations from Surface To illustrate No. 1 three cross-sections are shown, of excavations made for the stripping and excavation from three different orebodies

Jan 1, 1930

By H. C. Schultz

CERTAIN local conditions were known to govern in large measure the successful adaptation of liquid-oxygen explosives to the large-scale blasting at Chuquicamata. The wide variation in hardness of the rock at this mine makes necessary the use of several types of explosives. A locally manufactured, relatively cheap black powder is used in blasting the softer waste and capping material, where a thorough displacement, breaks the ground sufficiently. Before the introduction of L. 0. X., an ammonia dynamite of about 65 per cent. strength was being used exclusively in the harder underlying orebody, where a strong disruptive as well as a displacement effect is required for breaking the ore. The L. 0. X., as developed for quarry work in the United States, has a practically pure carbon cartridge material, and the explosive has an extremely high rate of detonation, which should therefore cause it to usefully develop its full disruptive effect in hard ground. The individual blasts at Chuquicamata are large, black-powder shots which dislodge masses of rock averaging 250,000 tons each, and dynamite shots which dislodge masses averaging 80,000 tons each. It was desirable, therefore, to attempt to displace with L. 0. X. the faster, higher-cost ammonia dynamite used in the smaller blasts. It was not considered practical to attempt to displace the low-cost black powder with L. 0. X., as estimated costs showed no probable saving if this were accomplished. Since it was desirable to continue shooting relatively large blasts for effective operation, it was recognized that larger storage facilities than had been in use would be needed for the liquid oxygen. Because of the difficulty of transporting and discharging large storage containers of efficient design, the better plan appeared to be storage and discharge of the liquid at the place of manufacture, and transportation of the filled soaking boxes to the blast.

Jan 1, 1928

Jan 1, 1889

By H. H. Kellogg

A model of the slag-fuming process for recovery of zinc oxide fume from lead blast furnace slags, adapted to solution by a digital computer, is presented. The model incorporates the variaticm with time of the following: the fuming of zinc and lead, the change in the ferrous-ferric ratio in the slag, the transfer of sulfur to and from the slag, the temperature of the liquid slag, the temperature of the gases and fume which exit to the flue, the heat losses to the water jackets, and the amount of frozen slag on the water jackets. The assumptions which underlie the model-some of which are but crude approximations—are discussed. Despite some obvious shortcomings, the model simulates faithfully many of the important features of practical slag-fuming operations. The behavior of the model is compared with the operation of the American Smelting and Refining Co. fumzace at El Paso, Tex. The model is used to predict the effects on performance of changes in the coal rate, the temperature of the secondary air, and the composition of the coal. THE fuming of lead blast furnace slag for recovery of zinc oxide is standard practice today, and it has been the subject of several previous attempts at mathematical process analysis.'-' The mathematical process model described in this paper incorporates many of the features from the earlier studies, but it is a far more complete and realistic representation of the commercial process in that the following additional features have been included: the fuming of lead as well as zinc; the transfer of sulfur between slag and gas; the addition of slag feed in batches, over a period of time; tapping of the final slag over a period of time; the change of slag temperature with time. The additional features of the present model add greatly to the mathematical complexity, but this difficulty has been obviated by programming the model for solution by a digital computer. The IBM 7094 computer solves the model for one operating cycle of the fuming furnace in less than 1 min. It is doubtful if the same calculations could be completed with the aid of a desk calculator in less than a month. The computer program, written in the Fortran IV language, is too lengthy for presentation here.* Instead, this paper As shown in the sections which follow, it does simulate with remarkable faithfulness most of the known behavior of the industrial process. On the other hand, the model contains several gross simplifications of both the chemistry and heat balance, necessitated by the lack of more exact knowledge. In addition to these known weaknesses, it is not unlikely that those more intimately acquainted with industrial practice than the author will find other additions to or modifications of the model which will improve its utility and reliability. CHEMISTRY In brief outline, the present model treats the fuming furnace as two units, A and B, in series. In A the batch of slag reacts with the continuous stream of air (primary and secondary) and fuel injected at the tuyeres, to produce a stream of hot, reduced gases containing zinc vapor. The zinc content of both the slag and the product gas changes with time because of the batch nature of the process. Unit A is called the "lower furnace" in this paper; physically, it is considered to be that part of the fuming furnace which lies below the charge port. In B, the "upper furnace", the product gas from A is burned with the stream of "tertiary" air, to produce zinc oxide fume. The performance of B also depends on time because of the time dependence inherited from the product gas of A. The rate behavior in the lower furnace determines the important features of the process—the rate of elimination of zinc and lead from the slag, and the amount of fuel required for this purpose. Bell, Turner, and peters' published the first useful model of the lower furnace. They employed the assumption that, at any instant of time, the slag and reduced gas reach a state of equilibrium, according to the reactions: They cited only indirect evidence in support of their assumption of slag-gas equilibrium, yet several more recent laboratory studies of the activity of zinc oxide in slags4-8 have produced evidence which supports their view. On first acquaintance it seems unlikely that a high-output "rate" process like slag fuming would even approach an equilibrium state. The author, in an earlier study,' established, however, that the gas-slag interface in a fuming furnace was capable of such high mass-transfer rates that a close approach to equilibrium between gas and slag was quite probable. In devising the present model it was decided to assume a state of equilibrium between slag and gas at the outset, and then to modify this assumption as necessary in order to make the model agree with the be -havior of the actual process. Up to this time the assumption remains a part of the model, since no behavior

Jan 1, 1968

By Milton H. Fies

Although pig iron from iron ore and red cedar charcoal preceded the mining of coal by many years, for tradition says that Alabama iron was used to shoe the horses of Andrew Jackson's soldiers, coal was not produced until 1830. In that year, coal was mined in Tuscaloosa County, in the vicinity of what is now the University of Alabama, and shipped on flat boats (obviously during the wet season, for there were many shoals) down the Warrior River to Mobile. About that time, the first railroad, the Decatur & Tecumseh, was being constructed in northern Alabama to overcome the obstructions to freight traffic caused by the now well-known Muscle Shoals in the Tennessee River. This railroad was patterned after a railroad at Mauch Chunk, Pa., which was used for hauling anthracite from the Panther Creek valley. The Alabama railroad, which required about four years to complete, was 46 miles long and was used solely for the transportation of cotton. Although it was a failure, it demonstrated the practicability of the undertaking, and the succeeding railroads, which were begun in 1834, 1848, 1852, and 1853, added immeasurably to the development of the coal resources of the state. Between the years 1830 and 1860, practically all the coal mined in the state was dug from the outcrop near the river or from the river beds, and shipped by boat to Mobile. Transporting coal down the Warrior River was an undertaking of great risk, required much skill, and frequently had heavy losses. It is recorded that this coal was sold to the gas company in Mobile in 1844; it was most likely mined from the Black Creek Seam. In 1914, on the completion of Lock 17, the Warrior River became a navigable stream from 9 miles above Cordova, Ala., to Mobile and offers a great opportunity for the future development of the coal resources of the state. Coke for foundry use was first made in Alabama in 1855. It was 21 years later, however, in 1876, that pig iron was made from Alabama ore with Alabama coal.

Jan 1, 1925

By Charles B. Dudley

DEAR SIR: It is now nearly three years since my first report to you on the subject of steel rails was written. That report, as you will remember, dealt principally with the question of the relation between the chemical composition and physical properties of steel rails end their power to resist crushing and fracture in actual service. Other matters were referred to or touched upon in that report, but the main question was, Why do some rails crush or break in service while others do not? Yon will doubtless remember that the principal conclusion arrived at was, that the softer rails are less liable to Crush or break in service than the hard ones. Or, in other words, so far as conclusions could be drawn from the chemical analysis and physical test of 25 samples of steel rails which had actually been in service, these conclusions were that those rails which have the smaller amounts of carbon, phosphorus, silicon, and manganese are less liable to crush or break in service than those which have larger amounts of these elements. Or, again, looked at in the light

Jan 1, 1881

From 1917 to 1926 mining at the Climax Molybdenum Co. property was confined to the Leal and White levels at elevations of 12,145 and 11,935 ft respectively and to surface outcrops above the Leal level. At present the production is coming from the Phillipson and Storke levels at elevations of 11,465 and 11,168 ft. Until 1926 when B. S. Butler recognized the relationship existing between the orebody and a central core of fine-grained hydrothermal quartz, the orebody was believed to be tabular in form. The orebody lies within the pre-Cambrian granites and schists and another rock type designated as the Climax porphyry and surrounds a highly silicious core, the mineable portion of which varies in thickness from 250 to 400 ft.

Aug 1, 1955

By James Aston

A proper consideration of this subject is not confined to the technical channels of production and metallurgy. It concerns an industry, and should cover economic aspects which are of material importance in any program of development. The discussion may logically be treated under three subdivisions, as follows: (1) manufacture, (2) characteristics related to quality of material; (3) adaptability and exploitation of product. Manufacture of Wrought Iron The manufacture of wrought iron is the most ancient art of the ferrous metal industry. The eighty years or less of existence of processes identified with our modern "Age of Steel" is a relatively brief interval compared with the several thousand years associated with the production of wrought iron by man. From the primitive early methods of production, manufacture for many centuries followed the line of direct reduction. There were developments as experience was gained through the years; but man's needs for a strong, ductile, forgeable product were met by reducing the ore to metallic iron in a single-stage operation. Following the development several centuries ago of what has become our modern blast-furnace operation, manufacture of wrought iron was gradually transformed into a two-stage method of first producing cast iron and then refining this to the desired degree of forgeability; the forerunner in principle of today's scheme of manufacture of steel. The product retained the essential characteristics of highly refined base metal with iron-silicate slag incorporation, which were associated with the material resulting from direct reduction methods. Cort's invention of the puddling process in 1784 is a landmark in wrought-iron manufacture. It consisted essentially in adapting a coal-fired reverberatory furnace to the refining operation; thus lifting the industry out of the slough of

Jan 1, 1935

By G. F. Loughlin, C. H. Behre

THE DEVELOPMENT OF CLASSIFICATION WHAT is the use of a classification of mineral deposits? From the days of Agricola, the founder of the science of ore deposits, successive authors on the subject have attempted classifications, none of which have attained unanimous indorsement of miners, engineers, or geologists. The miner and engineer naturally have little regard for a classification that does not help them to find ore. Mining geologists may share this feeling, and deplore the overemphasis that may be placed on classification by their academic brothers. Apparent effects of such overemphasis may be reflected by students or new graduates who have grown to think that each deposit must fit perfectly into some pigeonhole of the more or less arbitrary scheme that has been drilled into them. Diversity in mineral deposits as in other natural phenomena, however, is too great to be fully expressed in the usual tabular classification, and experience is essential for the appreciation of the value or usefulness of a classification. The succession of classifications has closely followed the growth of the science of mineral deposits and reflects that growth, as well perhaps as the limited or comprehensive viewpoint of each proponent. The earliest classifications were based on metal content, and were superseded by those based mainly on form of deposit. Source of materials also became a basis, and was followed by physical and chemical conditions and processes. In spite of this development it is interesting to note that in many of the latest reports on mining regions the authors adopt special classifications suited for their particular districts. Some of these, like the earliest classifications, are based primarily on metal content, and others are most conveniently based on form, and it may be convenient to modify these by reference to source of material or temperature of deposition. Some, including the writers, after noting these different usages, have refused to worry much over classification as an ultimate objective, but,

Jan 1, 1933

By Irving Hale

The superiority of electric power for mining purposes was recognized in a general way as soon as the electric motor be-

Jan 1, 1897

By Charles S. Barrett, Frederick N. Rhines, Robert F. Mehl

The solid solutions which aluminum forms with copper, and with magnesium and silicon, are not extensive, and accordingly could not be expected to form Widmanstatten figures profusely nor with great ease. A study of the Widmanstatten figures in these systems seemed desirable, however, because of the interest which these alloys bear towards age-hardening theories resulting from the necessary relationship between the age-hardening phenomena and the atomic processes leading to the formation of Widmanstatten figures.' Alloys of Aluminum with Copper The most accurate determination of the solid solubi1it.y of copper in aluminum seems to be that by Dix and Richardsoq2 whose results are represented in Fig. 1. According to this work, aluminum dissolves 5.6 weight per cent of copper at 548", and less than one per cent at room temperature. Judging from the constitutional diagram, this solid solu-lion on cooling tends to precipitate the compound CuA12, and this conclusion has been confirmed experimentally by Schmid and Wassermann.

Jan 1, 1932

By Alexander R. Troiano, Taylor Lyman

Studies of the transformation of aus-tenite at constant subcritical temperatures have been numerous since the work of Davenport and Rain.' Considerable information has been obtained on low-alloy steels and on high-carbon alloys containing undissolved carbide or graphite at the austenitizing temperature. Little is known of the isothermal transformation of aus-tenite containing in solution large amounts of both carbon and a single alloying element. In this investigation four steels containing one per cent carbon and with chromium in the range 3 to 9 per cent have been examined with the view to establishing the fundamental character of the isothermal reactions when all carbon and chromium are initially in solution in austenite. Experimental Procedure Alloys The chemical compositions of the steels investigated are given in Table I. The 4 per cent Cr alloy is a commercial steel. The other steels were made by the Carpenter Steel Co. as 50-lb., induction-furnace heats and rolled to 5/8 -in. round bars. Bars were softened at 650' to 700°C. before the specimens were cut. Most of the lines on the transformation diagrams presented here have been placed on the basis of the microscopic examinatioll of partially reacted specimens, Thees specimens were approximately 1/2 by 1/4 by 1/8 in. ill size, specimens of the 9 per cent cr steel were held 10 to 12 hr, at 1200°to 1225°C. before quenching to the various subcritical temperatures. The other steels were held for 2 to 2 1/2 hr. at 12ooOC. before quenching. These treatments, carried out in an atmosphere of purified nitrogen, produced an austenite grain size larger than A.S.T.M. So. I, some grains being 1 to 2 mm. in diameter. There were a few undissolved carbide particles in some specimens of the 9 per cent Cr steel. It is believed, however, that any errors in the results due to incomplete solution of carbon and chromium in austenite are negligible; that is, austenite compositions may be considered as being those listed ill Table I. X-ray Methods Constituents were identified and mar-tensite axial ratios determined from Debye

Jan 1, 1945

By W. L. Dennen, W. W. Wirth

Research looking toward the reduction of the cost of roof support by substitution of longer-life materials for wooden timber is fully justified by the fact that roof support is an important element of all production costs. Permanent or semipermanent roof support will reduce the expense of timber-maintenance crews during steady operations, but even more markedly during idle periods. The management, therefore, is faced with the important problem of timber renewals, which in times of regular operation are frequently obscured by more urgent problems of production. Increased use of timber in the Anthracite Region of Pennsylvania is caused mainly by increased percentage of coal obtained from robbing areas, which requires more timber for safety than development work, and maintenance of long haulageways through crushed ground despite the fact that less coal is transported over them. The timber reserve in the immediate vicinity of the mines has been depleted to such an extent that it is necessary to secure 70 per cent of the timber requirements from distant sources. Originally, mine timbering in this region was done by largely utilizing round props or legs with round collars. The whole cross section of the tree from which timber was cut was utilized by forming the joints between the legs and the collars with saw and adze, using plank or round saplings for lagging behind the legs and over the collars to prevent material falling between them. The Mine Inspectors' report of 1898 records an important digression from the use of round timber, when two tunnels at the Babylon colliery, near Pittston, Pa., were timbered with 12 by 12-in. square timber sets with mud sills, through quicksand for distances of 425 and 160 ft., respectively. The timbers were lagged with 3-in. plank to control sand. An early step toward the permanent type of roof support was the installation of "brick pillars or perfect arched brick rooms" instead of

Jan 1, 1940

By W. L. Dennen, W. W. Wirth

Research looking toward the reduction of the cost of roof support by substitution of longer-life materials for wooden timber is fully justified by the fact that roof support is an important element of all production costs. Permanent or semipermanent roof support will reduce the expense of timber-maintenance crews during steady operations, but even more markedly during idle periods. The management, therefore, is faced with the important problem of timber renewals, which in times of regular operation are frequently obscured by more urgent problems of production. Increased use of timber in the Anthracite Region of Pennsylvania is caused mainly by increased percentage of coal obtained from robbing areas, which requires more timber for safety than development work, and maintenance of long haulageways through crushed ground despite the fact that less coal is transported over them. The timber reserve in the immediate vicinity of the mines has been depleted to such an extent that it is necessary to secure 70 per cent of the timber requirements from distant sources. Originally, mine timbering in this region was done by largely utilizing round props or legs with round collars. The whole cross section of the tree from which timber was cut was utilized by forming the joints between the legs and the collars with saw and adze, using plank or round saplings for lagging behind the legs and over the collars to prevent material falling between them. The Mine Inspectors' report of 1898 records an important digression from the use of round timber, when two tunnels at the Babylon colliery, near Pittston, Pa., were timbered with 12 by 12-in. square timber sets with mud sills, through quicksand for distances of 425 and 160 ft., respectively. The timbers were lagged with 3-in. plank to control sand. An early step toward the permanent type of roof support was the installation of "brick pillars or perfect arched brick rooms" instead of

Jan 1, 1940

By Bror Nordberg

SAND and gravel are unconsolidated granular materials resulting from the natural disintegration of rocks. The two materials nearly al- ways occur together, variably proportioned in widely available de- posits. A commercial sand comprises the fine granular material, usually less than f in. in diameter (ASTM Designation C58-28), and gravel consists of the coarse, granular material larger than sand (ASTM Designation C125-46T). Gravel falls within the range of 1/4 in. and a top size usually of 3 ½ in. Chemical definition is impossible. Sand and gravel are always of secondary origin. They were formed from various massive rocks through the action of chemical and mechanical forces; then transported, abraded, washed, sorted, and classified by streams, glaciers, waves, or winds, to be redeposited in beds as they are found. Chief disintegrating forces in the reduction of rocks into granular particles were frost, rain, the dissolving action of acid and alkaline ground waters, the mechanical action of streams and waves, and the action of glaciers. Method of formation and deposition have imparted physical properties to sands and gravels that largely determine the commercial value of the materials for particular use and influence the manner of exploitation. In the early days of the commercial industry, purchasing specifications were relatively lenient but in. the past decade much more rigid quality requirements have had to be met for acceptance by all classes of purchasers. The trend to further severity in requirements is a challenge to the industry that commands full knowledge of the nature of raw materials at hand and skillful application of processing into commercial products. Mechanical strength, the ability to resist disintegration, chemica

Jan 1, 1949

By E. P. Polushkin

This work has for its purpose the establishment of a new method for determining the structural composition of alloys. The area occupied by a constituent on a few representative photomicrographs of the alloy is measured, by a planimeter, especially designed for metallographic work, and the volume and proportional weight of the constituent calculated. Experiments have shown that the results are accurate enough to justify the application of the method to many problems in metallographic research instead of chemical analysis. The advantage of the method is the possibility of determining the amount of the constituents without separating them from the alloy; their composition may also be determined if the ultimate chemical analysis of the alloy is known. Suppose Fig. 1 represents a part of a photomicrograph on which the total area of the black figures is to be found. By a system of parallel lines drawn short equal distances apart all figures may be divided into trapezoids. As the area of a trapezoid is equal to its median multiplied by its altitude, the relation between the total areas of the black and the white figures comprised within each strip is equal to the relation between the sums of medians for these figures respectively. This is also true for the whole area of the photomicrograph. Therefore, to determine the total areas of the black and white figures we must first find the proportion between the sums of the medians and then divide the area of the whole photomicrograph in the same proportion.

Jan 1, 1925

By C. L. Sainsbury

Lode and placer tin deposits of the western Seward Peninsula, Alaska, have produced more than 2200 tons of metallic tin and constitute the only known domestic deposits of economic grade and size. The lode deposits consist of quartz-topaz greisens containing cassiterite and wolframite as well as numerous base-metal sulfide minerals, and most are in or near altered biotite-granite that forms isolated stocks or in rhyolitic dikes near granite. Within the main lode-producing area in the central York Mountains, nonpegmatite beryllium deposits, consisting principally of fluorite, chrysoberyl, diaspore, tourmaline, and white mica, with minor euclase, bertrandite, phenakite, hematite, and todorokite, are distributed zonally around the tin deposits and locally are transitional with them. All the known beryllium deposits are replacement lodes in carbonate rocks. In the area discussed, both tin and beryllium deposits are localized in a structural belt striking N70° to N85°E across the central York Mountains. The belt is characterized by numerous normal faults, which cut extensive thrust sheets, and by dikes of rhyolite, rhyolite porphyry, and lamprophyre that were injected along the faults. Ore deposits are localized where the dikes intrude brecciated rocks beneath thrusts and, although complex in detail, form tabular lodes that tend to lie along the thrusts. The granites contain abnormal amounts of tin, beryllium, lithium, and boron, and the tin and beryllium lodes are believed to be genetically associated with these enriched granites

Jan 1, 1968

By H. E. Searle, Robert J. McKay, O. B. J. Fraser

The practical study of corrosion requires consideration of its economic aspects. It must be based on sound scientific principles, but it should be borne in mind that probably the most important object of a corrosion test is to determine what metal in corrosion-resisting construction will produce the greatest operating profit. Thus the corrosion test must be directly connected with money values or it is not a practical corrosion test. This, perhaps unusual, connection between corrosion and economics is partially due to the fact that corrosion deals only with the time factor or duration of equipment, and it is almost the only test which deals with this feature. In these statements a departure is made from the academic definition of the word corrosion and it is done deliberately. The use of the term corrosion is unusual. It is as though we spoke of a tensile test as a "breaking" test. We are not interested primarily in the break but in the strength of the metal. There is no English word which expresses our main interest in corrosion-testing, but let us have clearly in mind that we make corrosion tests to prevent corrosion. Our real interest is in this corrosion-prevention, not in the corrosion. Previous to 1922, it was common comment that "it is impossible to determine the course of corrosion by laboratory testing.'' This statement was true at that time in that the technique of laboratory testing for corrosion resistance was so vague that tests in the laboratory gave untrue results almost as often as true ones. This was so, even in the simple case of determining which one of two metals better resists a given solution. While this is no longer true the number of misleading "corrosion tests" still being ground out by laboratories is too large in the light of our present knowledge. There are two important features of corrosion testing whose neglect is a large contributing factor to misleading results: (1) The economic relations of the corrosion tests to other tests; (2) testing technique. Regarding economic relations J. F. Thompson l has said: "The use of any particular metal is rarely based upon the sole property of resistance to corrosion. In fact, I should like to venture the assertion

Jan 1, 1929