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By A. J. Jacobs, G. Katz

MANY of the studies of intermetallic compounds containing uranium were performed during the early 1940's under the aegis of the Manhattan Project. Subsequently, much of this work was declassified and published after 1949. In some instances this early work, completed with relatively impure materials, represents the only source of X-ray diffraction powder data available in the literature. In the case of the intermetallic compound U,Fe some discrepancies in the powder pattern exist in the literature. Since this compound has been prepared in this laboratory, it is believed that the publication of the indexed powder pattern would help clarify the conflict in the literature. In studies of the U-Fe system, Gordon and Kauf-mannl and Grogan and Clews2 independently reported the intermetallic compound U,Fe in 1950. The crystal structure was described by Baenziger, Rundle, Snow, and Wilson3 in 1950. It is isostructural with U,Mn, U,Ni, and U,Co and crystallizes in a body-centered tetragonal lattice. The lattice constants determined by Baenziger et al. are: giving an X-ray density = 17.7 g cm-3 for 4 mol per unit cell. The compound used in this study was prepared by melting a stoichiometric mixture of the constituent metals in an argon-arc furnace using a nonconsum-mable tungsten electrode. Before the argon of 99.98 pct purity was introduced into the furnace, it was passed through CaC1, to remove water vapor and afterwards through a stainless steel tube containing calcium turnings heated at 600°C for the removal of nitrogen and oxygen. The purity of the uranium used was better than 99.9 pct and that of the iron was 99.97 pct. Before and during melting a zirconium getter was used to further purify the argon atmos-

Jan 1, 1962

By Peter G. Groer

Several methods1-3 are being used to determine the WL and individual Rn-daughter concentrations in uranium mine atmospheres. The best of these methods is the one given in Ref. 3. According to this method, the WL and the Rn-daughter concentrations are determined from the total a-counts observed during three consecutive time intervals. Its only disadvantage lies in the fact that rather involved calculations are necessary to convert the observed counts into WL or pCi/l (picocuries per liter). There are, however, counting intervals that give simple weighting coefficients for the observed counts. This fact makes it possible to convert from a-counts to WL or pCi/l with the aid of a graph. After some trial runs on a computer the following equations emerged as the basis for the most practical procedure: [ ] NA, N.., and & stand for the number of RaA, RaB, and RaC atoms per liter of air. C(t1,t2) denotes the counts observed from time t. to time t2 (in minutes) after the end of the 5-min sampling period. E is the detector efficiency and V is the flow rate in liters per minute. With an accuracy loss of less than -5% one finds from [Eq. 1] by adding the corresponding terms: If the WL would have been calculated according to [Eq. 2] instead of using the graph, the result would have been 0.31. Since the values used for C's under [Eq. 3] represent the exact number of counts from a Rn-daughter mixture in equilibrium with 100/3 pCi of Rn the exact WL of this mixture can be calculated easily. The exact value is: [ ] This shows that the method is quite accurate for the 0.3 WL domain. The precision of the method excluding errors made in reading the graph can be estimated with the help of the following formula: [ ]

Jan 1, 1974

Hunkered up against the spine of the Andes in a tight valley where natural refuge from avalanche hardly exists is the daring Rio Blanco project of Cerro Corp. The deposit here was found in 1904, but nature has foiled all previous attempts to open it. To an experienced mountaineer or a highway engineer with mountain experience, the avalanche hazard in the valley of the Blanco river would be immediately apparent. The collar shaft is at the head of the valley at an elevation of 3600 m and for 12 km down the valley there is no space on the floor for building very much; the dissected rock walls are roadways for avalanches and even a highway could not be maintained sufficiently passable. This is the proposition taken on by the Cerro Corp. Chilean National Decree #1699, passed on December 9, 1966, signified "Go" to the Compania Minera Andina, a company whose shares are held 70% by the Cerro Corp. and 30% by the government of Chile. The orebody, although only partially delineated, contains proven reserves of 120 million tons of ore averaging 1.58% Cu. When the operation comes on stream in the last quarter of 1970, it will be at the rate of 11,000 tpd. Annual production will be 65,000 tpy of recoverable copper in concentrates.

Jan 11, 1969

By Wm. Reuben Webster

BRASS is an alloy of copper and zinc. The brasses (using this term to denote all useful proportions of the two constituents) are the most valuable and widely employed of all [ ] nonferrous alloys, because of their high resistance to ordinary corrosive agencies and the very wide range of properties that may be imparted to them by variations in the proportions of the constituents and by variations in mechanical treatment and heat-treatment. Fig. I shows the normal physical properties, as determined by standard tensile tests, of the series when in the annealed condition. Fig. 2 shows the effect of varying amounts of cold-working on an almost pure brass containing 70 per cent copper and 30 per cent zinc. Fig. 3 shows the effect of annealing at various temperatures on the same alloy. This effect is somewhat modi [ ] fled by the degree of cold-working to which a brass has been subjected, as shown by Fig. 4. A fourth test, which is empirical, has been found useful because of its simplicity -the hot hammer test. Samples Y2 in. in diameter and ¾ in. long are placed in a suitable furnace. These are withdrawn one at a time at successively higher tempera¬tures and are subjected to the blow of a drop hammer weighing 50 lb. with a drop of 4 ft. The percentages of' reduction in length of the cylinders are plotted against temperatures and give a comparative measure of plasticity at different temperatures. The results of this test on several

Jan 1, 1942

By J. McLaren Forbes

Geologists and engineers in charge of diamond drilling often have no practical experience in the work, yet they must direct the drillers. In discussing some of the problems that arise, the author of this paper has tried to remember the things he did not know about diamond drilling when he first came in contact with that work. The basic reason for most diamond-drill holes is to obtain information. The more thorough the understanding of the geological and engineering problems involved, the greater will be the benefit derived from a drilling program. One of the best methods to ensure some thinking before drilling is to record on the permanent drill log, before the hole is collared, the reasons for the work and the information desired from that particular hole. When the hole is finished, the information obtained should be recorded. Driller The choice of a diamond driller is very important. If no experienced driller is available, a competent miner who has a sense of responsibility and better than average mechanical ingenuity can do the work. The best answer to most practical drilling problems, from the standpoint of the person in charge of the drilling program, is the service of experienced diamond drillers or drilling firms. Equipment Drilling equipment should be adequate to put down the longest hole desired and handle the toughest ground encountered. The type of bit used depends upon the ground drilled. Experimenting with various bits and careful study of footage records are the best means of determining which to use. Under ordinary circumstances it is best to drill using an EX barrel when possible. The length of rod and core barrels that can be used depends on the size of the drill station. Also, the length of core barrel depends on the way the ground cores. In good ground as much core will be recovered with a 10-ft. barrel as with a shorter one, and with considerable saving of drilling time. A water pump is needed if the hole is so deep that the water pressure is not strong enough to wash out the cuttings, or if it is drilled at an angle that prevents full force of the water pressure. Instructions For an Inexperienced Driller 1. Never run a bit too long a time. When a bit seems to be "good for one more run," discard it. 2. Always let the rods down on bottom easily. Protect the bit from sudden shock. 3. Start the drilling slowly and easily. Do not put pressure on the bit too fast. Diamonds can break. 4. Be sure the water pressure is strong enough to clear the bit, but do not use more water than is needed, as it may wash away the core. Usually, if no core is recovered the hole is a total loss. 5. When dry-blocking, do not run without water longer than necessary as the bit may burn. 6. Be sure the rods are well caulked and tightly screwed together. If not well caulked they will lose water, and if not

Jan 1, 1946

By John J. Howard

WE are approaching the depletion of our principal source of iron ore-the Great Lakes deposits, which have provided 85% of the nation's requirements for the past fifty years. This situation presents a threat to our standard of living and our position as a world power. Fortunately, in the Great Lakes region there are still tremendous quantities of potential iron ore in the form of the low iron, high silica rock called taconite. The economical extraction of iron from taconite will insure our future steel supply if no new deposits available to the United States even in time of war are discovered. In the new process presented here, the iron is reduced directly by a simple method and then separated from the silica. The product is "feed," not to the blast furnace, but to the steel plant. This process requires very much less plant, less physical and chemical treatment, and less fuel and auxiliary materials than the conventional ore concentration-blast furnace method. In my opinion, this new, fundamentally different approach offers a better hope for the solution of the iron ore problem.

Jan 5, 1950

By C. Y. Clayton, Francis B. Foley, Muir L. Frey

DuRing the past year, we have investigated the cause of 88 per cent, of the failures by breakage near the bit end of some 1-in. hollow, hexagon, drill steel used in a metal mine. This breakage in the region of the bit end of the steel was peculiarly interesting because we have been Ied to believe that breakage is most prevalent at the shank end of drill steels near the place where the steel is gripped in the chuck of the machine. Records from the mine showed, also, that the breakage was much more frequent in the short lengths of large gage than in the longer steels; this is shown graphically in Fig. 1. Because the shorter lengths of steels are usually those that have been made from broken pieces of long steels or from steels that have worn down in service, rarely being made from new stock, those who are wont to suspect steel of tiring and crystallizing in its old age through fatigue are quite apt to see in this instance an argument in favor of their idea. As usual, a careful examination of these steels reveals defects of a character hardly to be overlooked in favor of such a cause. The steel in question was rolled with a sand core and was of the usual drill steel composition: Carbon 0.85 per cent., manganese 0.60 per cent., silicon 0.25 per cent., phosphorus 0.02 per cent., and sulfur 0.02 per cent., with the exception that in some specimens there was vanadium, not exceeding 0.20 per cent. The following lengths and gages were used: LenGth, GaGe, LenGth. GaGe, Feet Inches feet Inches Starter 2 % 7 111/16 3 2 % 8 11 4 2 % 9 1 9/16 5 2 10 1 7/16 ________6_____________115/16____________________________

Jan 1, 1924

By Charles Y. Clayton

The shank, to give good service, should not upset nor should it cause excessive wear on the various parts of the machine. To fulfill these requirements, the steel must have a certain hardness—that is, resistance to deformation. The hardness is expressed in conventional terms, as Brinell or scleroscope number. Before deciding on the hardness that is proper, several factors should be considered; the most important are: type of drill steel used (whether hollow or solid), length of steel, nature of ground, air pressure, and hardness of hammer or anvil block (usually 600 Brinell). These are not all, but they are the most cogent ones. Without doubt, it would be better to use a shank that is too soft than one that is too hard. Most satisfactory service will be obtained from shanks that are just hard enough to resist any tendency to upset. To express the proper hardness in terms of Brinell numbers would mean a great many tests over a long period of time, or a study of drill steels that are being used successfully in the various districts. To obtain some information along this line, the persons making this investigation requested, a number of companies to send to them drill shanks that had been given the usual treatment at that mine. The results of the hardness tests are given in Table 1. The hardness values given in Table 2 are those of shanks known to have been quenched in water and drawn. These results show that where water quenching and drawing are in vogue the hardness is rarely under 400 Brinell.

Jan 1, 1923

By Charles Y. Clayton

The shank, to give good service, should not upset nor should it cause excessive wear on the various parts of the machine. To fulfill these requirements, the steel must have a certain hardness—that is, resistance to deformation. The hardness is expressed in conventional terms, as Brinell or scleroscope number. Before deciding on the hardness that is proper, several factors should be considered; the most important are: type of drill steel used (whether hollow or solid), length of steel, nature of ground, air pressure, and hardness of hammer or anvil block (usually 600 Brinell). These are not all, but they are the most cogent ones. Without doubt, it would be better to use a shank that is too soft than one that is too hard. Most satisfactory service will be obtained from shanks that are just hard enough to resist any tendency to upset. To express the proper hardness in terms of Brinell numbers would mean a great many tests over a long period of time, or a study of drill steels that are being used successfully in the various districts. To obtain some information along this line, the persons making this investigation requested, a number of companies to send to them drill shanks that had been given the usual treatment at that mine. The results of the hardness tests are given in Table 1. The hardness values given in Table 2 are those of shanks known to have been quenched in water and drawn. These results show that where water quenching and drawing are in vogue the hardness is rarely under 400 Brinell.

Jan 1, 1923

C. P. BOWIE, San Francisco, Cal.-In my work with the U.S. Bureau of Mines, I have been detailed to report on oil storage containers, and in going around the country I have, been much interested in, the possibilities in the use of concrete for such containers. In talking with a good many people, I have discovered that concrete is being used A good deal for a wide variety of oils ranging from 14° to as high as 40° Bé., especially, by some of the western railroads:, If any member has had experience, in storing gasoline in concrete, I should like to learn of it. DORSEY HAGER, Tulsa, Okla.-Mr. M J. Munn, formerly .with the U. S. Geological Survey, acid connected with the Gypsy Oil Co., until a short time ago, has invented a invented a method for the application of concrete to the storage not only of crude oil but of refined products:. The Cosden Oil Co., of Tulsa, is now working on that plan, and, expects to store refined products in concrete tanks. THE CHAIRMAN (I.N. KNAPP, Ardmore Pa.).-I have had considerable experience in building masonry tanks for gas Holders. I do not believe it is possible to build a concrete or masonry tank of any kind. With hydraulic cement, mortar, which will be absolutely water-tight, unless the bottom and inner wall, after completion are waterproofed with some impervious material. The same will be true of oil tanks, the bottom and inner face of which must be made impervious to oil. Masonry tanks are intended to be sunk in the ground. All that the wall of the tank then amounts to is a retaining wall to keep the excavation in shape and to receive an impervious coating. The bottom of, a; tank, when empty, must be protected by a relief valve from any hydraulic: pressure acting from below. At ordinary prices, for sheets, a tank 100 ft. diam by 20 ft. deep can be built of steel much quicker and cheaper than of masonry. Several years, ago I saw very large oil storage tank under construction in California the bottom and sides being concrete. The sides were, sloped at about the single of repose for the material excavated: If you build a steel oil tank, you can get. .men for the work who do nothing else, and you, are likely to get a satisfactory job; but if you wish to build a concrete or masonry tank it is almost: impossible to find men skilled in building absolutely water-tight masonry Work. The general idea is that any laborer can mix up concrete in any old way and make a,

Jan 1, 1918

By W. H. Emmons

This paper is the second of a series treating the relations of ores of the metals to igneous rocks. In the first paper1 the general problem was outlined and the normal downward changes in metalliferous lodes were briefly stated, with references to earlier papers treating the relations of ores to depths of their formation. The present paper by a number of examples illustrates the relations treated in the first paper. These examples are chosen chiefly from the larger mining districts because their underground developments are more extensive, but the same relations are shown in maps of scores of undeveloped areas in which the main geological conditions are nearly similar. Ecology of Metalliferous Deposits Ore deposits are divided into three groups: 1, Those formed by sedimentary processes; 2, those deposited by meteoric waters; and, 3, those formed in connection with igneous processes. The last group is the most important. It includes the magmatic segregations, which are igneous rocks in the strict sense, and the veins and related deposits, which were formed by precipitation in channels from solutions originating in cooling intrusives. These deposits may be divided into two groups: 1. Those related to intrusives as basic as diorite; and, 2, those related to intrusives more acid than diorite. The second group probably includes more than 95 per cent. of all lode ores. Nearly all of the ores of this group are associated with granitic batholiths or are in positions where it is reasonable to suppose that such a batholith, not yet exposed by erosion, underlies the area containing the deposits. The batholiths are great masses of deep-seated igneous rocks. When they are intruded most of them are probably as basic as diorite and some

Jan 1, 1927

By Clarence O. Babcock

A simple robust rock bolt load gage was tested in the laboratory to define its characteristic behavior and to obtain a measure of its performance. The gage uses three vibrating wire sensors crimped 120 (2.09 rad) apart into the outer surface of a hollow cylindrical steel, tube. The resonant frequencies of the wires change as the gage is loaded. This change is read with a Creare meter developed for the Bureau of Mines on a previous contract to read borehole stress gage results. A statistical analysis of data obtained defines the variables influencing results. A U.S. patent (3,914,992) assigned by the author to the Dept. of the Interior was granted Oct. 28, 1975.

Jan 1, 1978

By Robert Forsyth

As the latest plant on a large scale, the new Bessemer works of the North Chicago Rolling Mill Company, at South Chicago, presents some features of interest to steel-makers, I have ventured to lay before the Institute a short description of that plant, and some* remarks upon the practice there. At the time the South Chicago works were designed the adoption of the basic process in this country seemed imminent. Experience in Europe had demonstrated the perfect success of the process technically, and the question of its commercial value was one which, for any particular works, would have to be settled by its special advantages for procuring the necessary ores and basic materials. Under the circumstances, it was thought best at South Chicago to so arrange the plant as to allow the introdnction of the basic whenever it became advisable, and to make such other changes from the standard type of Bessemer plant as the state of the art seemed to demand and to foreshadow. As the use of metal direct from the blast furnace, while generally condemned by experts here, was in such successful practice in Europe (particularly in connection with the basic process), there was no doubt about its feasibility, while its economy in fuel and labor made it especially attractive to the Western manufacturer. It was accordingly decided to build a direct-metal plant adapted to the basic process. The ingots made were to be rolled into rails at one heat, and were to be of such size (12 inches square and long enough for three and four rails) as to be readily and quickly handled by the rolling machinery proposed. This small size of ingots, and the large number cast from each heat of 10 tons, made it necessary to provide a good deal of room in the casting-pit—much more than in any previons plant—and to put down extra facilities for handling ingots. To meet the delays incident to the basic process—to insure that one vessel should be always blowing if necessary, and to provide opportunity for current repairs to linings, etc.—it was decided that three vessels should be used, and, to properly concentrate the work of

Jan 1, 1884

By T. H. Alden

T. H. Alden (General Electric Research Laboratory)—This paper as well as earlier ones of Dr. Wood represent an important contribution to the experimental description of fatigue fracture. The mechanism of fracture proposed by the authors, however, is not established by this data nor supported by other data existing in the literature. Although taper section metallography provides a rather detailed picture of fatigue crack geometry, photographs so obtained must be interpreted with care. The narrow bands revealed by etching, frequently associated with surface notches, are labeled by the authors "fissures". Measurement shows, taking into account the 20 to 1 taper magnification, that the depth of these structures is at most 2 to 3 times the width. This distinction is important in the conception of a mechanism of crack formation. It is difficult, for example, to imagine a deep, narrow fissure arising from a "ratchet slip" model. A surface notch, on the other hand, may form easily by this mechanism. The notches observed in the present work are the subsurface evidence of the surface slip bands or striations in which fatigue cracks are known to originate.4-6 It is clear that an understanding of the structure of these slip bands is of key importance in understanding the mechanism of fracture. The evidence presented shows that these regions etch preferentially, possibly because they contain a high density of lattice defects, or as the authors state equivalently, because they are "abnormally distorted." However, it is not possible to conclude that the distortion consists of a high density of vacant lattice sites. The fact of a high total shear strain in itself does not assure a predominance of point defects as opposed to other defects, for example, dislocations. Other evidence in the literature which suggests unusual densities of point defects formed by fatigue7-' refers not to the striations or fissures, but to the material between fissures (the "matrix"). If a choice must be made, the preferential etching would seem to be evidence for a high dislocation density, since dislocations are known to encourage chemical attack in copper;g no such effect is known for the case of point defects. A third alternative is that the slip bands are actually cracked, but that near its tip the crack is too narrow to be detected by the authors' metal-lographic technique. In this case the rapid etching can be readily understood in terms of the increased chemical activity of surface atoms. Unless a vacancy mechanism is operative, the motion of dislocations to-and-fro on single slip planes will not lead to crack growth. Point defect or dislocation loop generation are the principal non-reversible effects predicted by this model. In any case, the nonuniform roughening of the surface in a slip band6 requires a flexibility of dislocation motion which is not a part of the to-and-fro fine slip idea. The same is probably true of crack growth by a shear mechanism. Either some dislocations must change their slip planes near the end of the band and return on different planes,'0 or dislocations of opposite sign annihilate." The mechanism by which these processes occur in copper at room temperature or below is that of cross slip. Thus cross slip appears to be essential to fatigue crack growth.6'10"12 The fact that a tensile stress opens the slip bands into broad cracks does not indicate the structure of the bands or the mechanism by which cracks form. The charactersitic concentration of slip into bands during fatigue shows a low resistance to shear strain in these regions. (This fact in itself may be inconsistent with a high concentration of vacancies.) The authors contend also that continuing shear produces an additional mechanical weakening so that the bands fracture easily (are pulled apart) under the influence of the superimposed tensile stress. It is equally possible that the only weakness is a weakness in shear, that the crack propagates by a shear mechanism, and that subsequently the tensile stress pulls the crack apart. Even the direct observation of bands opened by a tensile stress would not be conclusive since, as argued above, they may be fine cracks. The same argument applies to internal cracks, their existence in the presence of a tensile stress not indicating the mechanism of formation. Internal cracks originating in regions of heavy shear have also been seen following tensile deformation of OFHC copper,13 so that this mode of fracture is not unique to combined tensile and fatigue straining. The authors point out in their companion report14 that 90 pct of the cracks formed during pure tor-sional strain were within 8 deg of the normal to the specimen axis. If the tensile stress were an important factor in crack propagation, it is surprising that the cracks cluster about the plane in which the normal stress vanishes. Similarly, a study of zinc single crystals showed that for various orientations the life correlated well with the resolved shear stress on the basal plane,'= and was not dependent on the normal stress across this plane. W. A. Wood and H. M. Bendler (Authors' reply) -Dr. Alden's discussion emphasizes the essential point in the relation of slip band structure to

Jan 1, 1963

By F. X. Tartaron

This article is a continuation of a previous paper by the writer in which Kick's Law was stated to be a part of comminution theory. ln the present paper, a broadening of ideas is attempted in order to state a general theory. The word "general" is employed because the new theory includes all previous laws and generalizations which are considered to be essentially correct. These ideas are combined into a coherent whole and the general theory can be expressed by the equation In the author's previous paper on comminution, ' the equations developed were based on Charles' equation of exponents a-n +1 = 0. 2 This paper is divided into two parts, designated as First Approach and Second Approach. In the First Approach, the equations of the previous paper are utilized, with Charles' equation of exponents being necessary. In the Second Approach, a separate and independent method is used to derive the same conclusions as in the First Approach, but without the use of Charles' equation of exponents. Holmes accepts the theoretical foundation of Kick's Law as sound but denies that the law as such operates in comminution. His idea is that Kick's Law requires homogenous matter whereas the presence of cracks, flaws and cleavage planes, which predominate in the coarser particles, makes matter unhomogene-ous. This explains why there is no experimental evidence to support Kick's Law. However, since the basis of the law is theoretically sound, all experimental evidence must be viewed as emanating from it. This requires modification of current comminution equations to fit this concept. Holmes makes the modification by changing the constant exponent n in the general energy equation used by Charles (E = - JCdx/xn) to a variable exponent r. The writer asserts that Kick's Law operates in comminution without modification but it does not

Jan 1, 1963

By B. D. Cullity, J. T. Norton, M. Telkes

THIS investigation of antimony-selenium alloys was undertaken in an attempt to find a suitable material for use in power-generating thermocouples. The chief requirements for such a material are high thermoelectric power, low electrical resistivity and low thermal conductivity. Measurements of the first two properties mentioned are usually sufficient to determine whether or not a material is suitable for use in a thermoelectric generator. As a first approximation the requirements are: 1. Thermoelectric power greater than 200 microvolts per °C. 2. Electrical resistivity less than 0.002 ohm-cm. 3. Thermal conductivity less than 0.015 watt per cm per "C. These quantities are averages for the Operating temperature range. Previous Work Experimental investigations of equilibrium in the antimony - selenium system have been summarized by Han-sen². These investigations extended from 1906 to 1921. In Hansen's judgment, the most accurate phase diagram is that determined by Parravano, in 1913 and this is reproduced in the upper part of fig. 1. The most notable parts of this diagram are the liquid miscilibility gap, extending from about 12 to 36 wt pct selenium, and the intermediate phase Sb2Se3 containing 49.3 wt pct selenium. The crystal structure of Sb2Se3 has not been determined. Pelabon3,4 made measurements of the electrical resistivity of a few antimony-selenium alloys but his investigation was not very complete. He found that the resistivity increased with the selenium content and became very large as the composition of Sb2Se3 was approached. For alloys containing less than 50 at. pct (39.3 wt pet) selenium, he found that the resistivity increased regularly with temperature. For alloys containing larger amounts of selenium, he found various results: in some cases, the resistivity decreased with increas-

Jan 1, 1951

By D. J. Jr. McAdam

RESULTS of a general survey of corrosion-fatigue phenomena at the Naval Engineering Experiment Station were presented in five previous papers.1-5 In these papers references were given to the work of Haigh in 1917.6 The five papers mentioned gave a general survey of the behavior of metals when tested to failure under simultaneous corrosion and cyclic stress. As a result of this survey the fourth paper gave a tentative analysis of the corrosion-fatigue process. According to this analysis, if the initial stress is below the endurance limit but above the corrosion-fatigue limit, the corrosion-fatigue process is divided into two periods. The first period is the formation of pits. As the initial stress is below the endurance limit, the pitting is assumed to be due to corrosion, not to fatigue. The corrosion pitting, however, is not the ordinary pitting of stressless corrosion, but is an accelerated pitting due to the effect of the cyclic stress on the corrosion. As the pit progresses, both the actual stress and the effective solution pressure increase. The increase of actual stress is due to increasing stress concentration at the bottoms of the pits. The increase of effective solution pressure is due to the increase of actual stress. The mutual intensification of stress and solution pressure continues until the actual stress at the bottoms of the pits surpasses the endurance limit. The second period of corrosion-fatigue then begins. In this period the process is merely fatigue accelerated by the corrosion. The cracks advance at a continually accelerated rate until the specimen breaks.

Jan 1, 1930

By Chandler Morse

RENEWABLE VS. NONRENEWABLE NATURAL RESOURCES Nonrenewable resources, such as minerals, are the inevitable center of attention in discussions of depletion and exhaustion. Nevertheless, it may well be proper to regard some nonrenewable resources as not subject to exhaustion, and renewable resources may sometimes be treated as if they were finite stocks. Thus, the availability of nonrenewable resources is not and probably never will be known completely Chap. 2.5A, and therefore is not subject to firm predictions concerning exhaustibility. Moreover, because exploration and discovery are more or less continuous processes it is often appropriate to regard mineral supplies as flows, and to treat the estimated reserves as working capital, an inventory, continually depleted by use and augmented by discoveries.23 The aggregate economically exploitable stocks of a given mineral are seldom estimated (or estimatable) with precision, as Chap. 2.5A shows, and even when they are, forecasts concerning years of remaining life can be and often are falsified by changes in one or more of the multidimensional conditions of supply and demand; or the productive services formerly derived from an exhausted stock may continue to provided without material impairment by one or more substitutes b Conversely, the renewable resources are all subject to depletion when the rate of use exceeds the natural or induced rate of replenishment, and cases of exhaustion or near exhaustion, as through soil erosion, overcuttmg of forest lands, and overfishing, are rather common c Where exhaustion is a clear possibility the resource may either be exploited on a consciously adopted "sustainable yield" basis or be treated as an exhausting asset." In some cases, conscious treatment

Jan 1, 1976

Shooting Soot from Stacks In the DuPont magazine of June, 1916, S. R. Russell describes a method of cleaning large smoke or kiln stacks which he calls "simple,. economical- slid-most efficient" and-which- he -says can- be used in either-lined or unlined stacks, brick or steel, without fear of injury to the stack or lining. He gives the following specific directions: "The gun can be made out of air old piece of shafting about 4 in. in diameter and 14 to 16 in. long. Bore a hole 1 ¾ in. in diameter and 10 in. long in the center of the piece. Then bore a small horizontal hole ¼ in. in diameter through the piece-to the bottom of the center bore. This hole serves as a touch hole for inserting the fuse. "The-whole thing can be mounted on a pedestal about 6 in. in diameter so that it will stand in an upright position. "The -method of operation is as follows: Pour some FFF Blasting Powder into the mouth of the cannon to about 2 in. from the top. Tamp to the collar with dry clay. , A short piece of fuse is inserted in the touch hole and in contact with the main powder charge. Open the flue door at the bottom of the stack, set the cannon on the bottom and in the center of the stack, light the fuse and close the flue door. "The explosion shakes and loosens the soot adhering to the sides, causing it to fall to the bottom. It can' then be removed through the flue opening.

Jan 9, 1916

By W. H. Emmons

In 1922 Morey made a series of experiments in which he observed the cooling of a molten system containing H2O, 9.1 per cent; K2O, 17.3 per cent and SiO2, 73.6 per cent. This system was confined in a bomb; it was fluid at 500° C. and exerted no vapor pressure. In cooling to 420° C. a large part of it crystallized and at that temperature much of the water had separated from the crystals and remained as steam, which built up a pressure of 4998 lb. per sq. in., a force sufficient to lift nearly one mile of granite.' If granite, cooling at 600°, expels vapor in the process of crystallization it is reasonable to suppose that a considerably greater vapor pressure would result, and it is thought that the vapor expelled from crystallizing granitic batholiths probably has a pressure sufficient to lift two or three miles of granite. This vapor, collecting near the tops of cupolas of batholiths, is believed to exert sufficient pressure to fracture the hoods and roofs of batholiths above the cupolas. If that is true, one would expect to find that the fracture systems above cupolas are arranged in patterns that depend in part on the shapes of the cupolas. The mechanics of the situation seem to require that conical cupolas should have radial fracture patterns, that bluntly rounded cupolas should have fracture systems that are either irregular or rudely conjugated in plan, and that elongated stocks or cupolas should have fracture systems in which the fractu'res lie nearly parallel to the direction of the elongation of the cupolas. Study of essentially all the cupolas of the earth that have associated important vein-filled fractures shows that this is generally true. This

Jan 1, 1935