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By John B. Mertie

More than 200 minerals are known that contain the rare-earths and thorium. Monazite and bastnaesite, however, are the principal commercial sources of the rare-earths, and monazite is the principal source of thorium. Monazite was in demand in earlier years mainly for its content of thorium, which was used in the manufacture of Welsbach gas mantles; but beginning in the latter part of the nineteenth century, the rare-earths became progressively more important than thorium. Recently, however, the tenor of thorium in monazite has again become a matter of commercial interest. Rare-Earths and Thorium The rare-earths proper are defined by spectroscopists as the oxides of 14 elements with atomic numbers ranging from 58 to 71; but more commonly lanthanum, with an atomic number of 57, is also included, in which case these 15 elements are often designated as the lanthanides. Chemists also include scandium and yttrium as elements of the rare-earths. A second group of elements, beginning with actinium and including thorium, protactinium, uranium, and all the transuranium elements so far produced, with atomic numbers ranging from 89 upward, are chemically and structurally related to the lanthanides, and are known as the higher rare-earths or actinides. Berzelius discovered that the lanthanides could be separated roughly into three groups, based upon the solubility of their double salts, R2(SO4)3-K2SO4-2H2O, in excess of K2SO4. This separation, with the substitution of sodium for potassium, is still used commercially. The double salts of the cerium earths were found to be almost insoluble; the terbium earths, partly soluble; and the yttrium earths, completely soluble. Based upon the degree of solubility, scandium belongs with the cerium earths; and yttrium belongs with, and gives its name to, the yttrium earths. These three groups with their atomic numbers are shown below. [ ] The prevailing state of oxidation for the rare-earths is R2O3, but cerium may readily be oxidized to the tetravalent state, in which condition it may be separated chemically from the other cerium earths. Praseodymium and terbium may also exist with the valence IV, and samarium, europium, and ytterbium may have the valence II. Most of the elements of the rare-earths, however, are very difficult to separate, and their initial isolation required the work of many chemists over a period of 150 years.20 Fractional crystallization, fractional precipitation, and ion exchange are the principal methods so far used, and fractional precipitation is now employed commercially on a large scale. Ion exchange columns are

Jan 1, 1960

I. PRESIDING OFFICER. At all business meetings of the Institute the President, or, in his absence, the First Vice-President, or, in the absence of both of them, any other Vice-President or Director, chosen by the meeting, shall preside. At all other meetings of the Institute the President, or, in his absence, one of the Vice-presidents, shall preside. If none of these be present the meeting shall elect a Chairman. The President shall do and perform such other duties as may from time to time be assigned to him by resolution of the Board of Directors of the Institute. II. ORDER OF BUSINESS. At each business meeting of the Institute the order of business shall be as follows: 1. Reading of minutes of preceding meeting. 2. Report of the President. 3. Report of the Treasurer. 4. Report of the Secretary. 5. Election of Directors. 6. Reports of Standing Committees. 7. Reports of Special Committees. 8. Special Orders. 9. Miscellaneous business. This order of business may be changed at any meeting, by a vote of a majority of the Members and Associates present. At all sessions of the Institute, other than business meetings, the order of proceedings and the time of adjournment shall rest in the discretion of the presiding officer. III. SECRETARY OF THE INSTITUTE. The Secretary shall keep a record of the proceedings of all the meetings of the Institute. He shall be custodian of the corporate seal, of the minute books and of all the legal documents belonging to the Institute. He shall have charge on behalf of the Institute of all correspondence. He shall notify all Officers and Directors and all members of committees of their election and appointment; shall issue notices of all meetings of the Board, and of the annual and other business meetings of the Institute; and shall, in calling special meetings of the Directors, specify the objects of such meetings. He shall act as clerk at all the meetings of the Board of Directors and at all meetings of the Institute. The Secretary shall be custodian of all technical or scientific papers submitted to the Institute for its consideration and shall have general charge and supervision of the editing and proof-reading of all material published by the Institute, and of the distribution thereof. The Secretary shall be the custodian of all back numbers of the Transactions and other publications of the Institute. There shall be kept under his direction an account

Jan 1, 1925

By F. C. Muttitt

The physical arrangement of the continuous casting facilities at Algoma have been described a number of times in previous papers. For the purposes of this discussion, it is sufficient to state that the casting plant is located at a considerable distance from the basic oxygen shop which supplies it, involving a relatively lengthy ladle transfer movement. (Fig. I) The handling of the ladle by two separate cranes, first to the argon station, and thence to the casting machines, results in an average interval, from start tap to start cast, of 45 minutes. The effects of such extended retention time on temperature control and on refractory performance are well known. Tapping temperatures well above normal are necessary to insure that the ensuing heat losses do not result in an undue incidence of premature tundish freeze-offs. The heat lost, as well as being a function of the retention time, becomes more critical with smaller ladle size; winter temperatures add to the problem with their effect in chilling ladles and increasing radiant losses.

Jan 1, 1972

By J. A. Bownocker

THE Pittsburgh is one of the most important coal beds of Ohio. It was the last of the great coal beds to be worked extensively in that State, has the largest area of virgin coal, and will in all probability be the last of the great deposits to be exhausted. The line of outcrop sweeps nearly southwest in a sinuous line from Jefferson County on the north to Lawrence on the south, a distance on a bee-line of at least 150 miles. (Fig. 1.) The maximum width of the area under which this coal is due is about 55 miles, but in most places it is less than half that and in the two southern counties it is in places restricted to narrow ridges. Here as elsewhere the Pittsburgh coal forms the base of the Monongahela formation, and the following section taken from Condit shows the position of this bed with reference to certain higher ones in this field:1 FEET INCHES Shales and thin beds of limestone 24 5 Coal, Meigs Creek, No. 9 4 0 Shale, sandy 11 0 Coal 0 8 Shale, clayey 6 0 Coal, Lower Meigs Creek 3 0 Shales,clayey 2 0 Limestones and thin layers of clay 25 0 Unseen 11 0 Coal, Redstone 2 0 Unseen 11 0 Coal, Pittsburgh, No. 8 8 0 Clay 5 0 Limestone 4 0 From the standpoint of continuity the Pittsburgh coal of Ohio must be classed with the patchy type. As the map shows, the coal is thin or wanting along many miles of the line of outcrop. The large deposits form three separate areas, which, in order of their importance, are generally known as (1) the Belmont, (2) the Federal Creek, and (3) the Gallia fields.

Jan 10, 1926

By Ralph Hultgren

IN solid solutions atoms of differing sizes occupy the same crystalline lattice, requiring that some of them be compressed and others expanded. The energy involved has been called misfit strain energy and is an important concept of crystal chemistry. If the atomic sizes and elastic constants of interatomic bonds are known, the misfit energy may be calculated,' provided certain simplifying assumptions are allowable. Usually, isotropic crystals are assumed and interatomic distances are taken to be the statistical average determined from X-ray diffraction. Such calculations yield values of the misfit energy of the order of 1 or 2 kcal per atom in alloys such as Au-Cu at compositions of 50 atomic pct. However, evidence has accumulated in recent times that atoms change their sizes with composition of alloys, implying electronic rearrangement of the bonds. The size changes have been found particularly by application of the X-ray method developed by Warren, Averbach, and Roberts.' Thus, Averbach, Flinn, and Cohen3 determined radii in Au-Cu alloys. Oriani4 showed that these new radii led to a calculated misfit energy in disordered AuCu, which was decreased from the values calculated by the usual theory more than twenty-fold, to only 80 cal per g atom. Thermodynamic calculations from the phase diagram5 also show misfit energy to be no more than a few hundred calories per g atom in this alloy. The question of what electronic rearrangements are possible therefore becomes compelling in estimating misfit energy. In the following pages the results of certain calculations on the AuCu tetragonal superlattice are submitted. Conclusions drawn from these should be applicable in large degree to disordered solid solutions. As in all ordered states, bonding distances in the superlattice are individually known, rather than being merely average distances as found from lattice constants of disordered states. Moreover, only the Au-Au and Cu-Cu distances are strained; the elastic constants of these are known in the elementary state. In the usual calculation it is necessary to assume elastic constants for Au-Cu bonds. Misfit energy has thus been calculable without the need of many simplifying assumptions usually made. It is still assumed that equilibrium bond lengths and elastic properties of the bonds are the same in the alloy as in the pure metals. As previously discussed, this is probably not correct. Also assumed is that the bonds are not affected by strain of neighboring bonds. A calculation of Young's modulus from compressibility data shows this to be far from true; extensive electronic rearrangements take place. It would seem that misfit energy cannot be calculated from elasticity data for the elements. The usual methods may, however, give an upper limit which is often much higher than the true value. The question of electronic rearrangement is, of course, a complex one. Pauling's theory gives a simple, approximate treatment of the relation between type of bond and bond distance. This has been applied with some success to the Au-Cu system, as will be shown in a later section. Misfit Energy in Au-Cu Alloys Hume-Rothery and Raynor6 discuss the Au-CU system as a type example of strain energy. The gold atom is 12.8 pct larger in diameter than the copper atom, near the size factor limit beyond which solid solubility is severely restricted. They therefore consider the misfit energy to be large, a conclusion for which they believe they find evidence in the phase diagram. Gold and copper are completely miscible in the solid state, but the alloy has a minimum melting point at an intermediate composition. From this Hume-Rothery and Raynor conclude that the strain energy is nearly large enough to prevent miscibility; the phase diagram tends toward a eutec-tic type. In Ag-Cu, which has almost identical size relationships, solid miscibility is quite limited; whereas in Au-Ag, where atomic sizes are nearly the same, there is complete miscibility without a minimum in the melting point. From their arguments the heat of formation of Au-Cu would be expected to be endothermic or only slightly exothermic, that of Ag-Cu to be endothermic, and that of Au-Ag to be exothermic. Deviations, from Ve-gard's law of additivity of atomic radii support these conclusions, since Au-Cu and Ag-Cu both have pronounced positive deviations, and Au-Ag has a negative deviation. Nevertheless, Au-Cu alloys form exothermically; indeed, considerably more exothermically than Au-Ag, Table I. Hence, strain energy must be much less important in this case than Hume-Rothery and Raynor have supposed.

Jan 1, 1958

By J. H. Clemes

The process of leaching silver ores with sodium hyposulphite is comparatively new, and published accounts of the details and losses of the process are as yet very few. The following account of a careful series of experiments to determine the actual loss in this process may therefore be acceptable to members of the Institute. The ore treated was highly calcareous, and the principal sulphide present was iron pyrites. Following is an analysis by Professor Price, of San Francisco, of the ore treated : Per cent. Silica,..........15.13 Sulphur,.........13.31 Arsenic,.......... 9.82 Iron............ 17.33 Alumina,..........1.35 Zinc,...........4.92 Lead,..........1.78 Carbonate of lime,..33.78 Magnesia,.......... 2.58 100.00 Ten tons were crushed dry with a 30 X 30 screen = 900 holes per square inch. In order to feel our way with this ore, two experimental or "pilot" charges were roasted. Pilot Charge No. 1. Treated 1000 pounds in a four-hearth reverberatory. 8.30 p.m.—Entered fourth hearth, remaining there one and onehalf hours; sulphur began to burn. 10 p.m.—Changed to third hearth; ore became red-hot half an hour after entering; the fireplace was kept almost destitute of fuel. 2.30 A.M.—Changed to second hearth. Charge continued, giving off a large quantity of sulphurous fume; the fireplace was kept dark.

Jan 1, 1884

By Freeman Bishop

The Interior Department has been in a state of disarray for many months. At first this was attributed to Interior Secretary Walter Hickel's inability to anticipate how his words would be interpreted by Press-Radio-TV. But then the already disquieted ernployees in the Department became aware that plans were afoot to take bits and pieces of the various antipollution programs from Interior; Health, Education and Welfare: the Atomic Energy Commission and other agencies and lump them together into a new Federal agency. Interior, many predicted, would be a shell of its former robust self. Hardly had this rumor started to add to employee uneasiness before the other big shoe hit the floor. The new rumor had it that the Bureau of Mines was being stripped of most of its research functions and that the Office of Coal Research and allied research groups would be abolished altogether.

Jan 1, 1970

By John F. Abel

The following quotation is from "Guidelines for evaluation of undergraduate curricula in geological engineering, mineral processing, and mining engineering" prepared by the Committee on Education of SME of AIME. "The objectives of the Engineers' Council for Professional Development (ECPD), as delineated in its constitution, are: (a) To promote and advance all phases of engineering education with a view to the promotion of the public welfare through the development of the better educated engineer and engineering technician." (Italics added.) The problem is that no one has as yet seriously developed a method of supplying engineering technicians. There were great hopes that the expansion of junior colleges would help satisfy this need. Sadly, they have not; and it appears they are unwilling or unable to supply the need for mineral engineering technologists. Apparently, the junior colleges cannot afford staff for such courses, even when the colleges are located in mining districts.

Jan 1, 1971

Albert Sauveur, Cambridge, Mass. (written discussion).— In his introductory paragraph, the author states that he has come to bury Beilby, not to praise him. The paper, however, gives the impression that while he may have dug the grave, Beilby is still at large. I am not one of those whom the author calls enthusiastic supporters of Beilby's amorphous theory and in support of this claim quote from a book I am writing: "Attractive as the amorphous theory is, and notwithstanding the ability with which it has been presented and the renown of its sponsors and supporters, it should not be accepted without reservations as a demonstrated fact.... So long as it explains more satisfactorily than other theories a greater number of phenomena in which it may play a part, we should use it in preference to others as the best available. Let us avoid the danger, however, into which too many fall, of accepting as indisputable truths, statements and theories emanating from those whom we hold in great esteem. It is not what those men themselves would wish us to do. I am entitled, I think, to occupy a position in the middle ground. Neither should Howe be classified with the enthusiastic supporters for he has written that the theory should be classed rather among the precious working theories than among those firmly established," a very wise and prudent statement. Jeffries, on the other hand, I would not hesitate to describe as an enthusiastic supporter. The author reproaches the advocates of the amorphous theory with having taken whatever properties they needed and with having assigned them arbitrarily to the hypothetical amorphous phase. He then applics their method to small crystals. If the existence of an amorphous phase is assumed, its greater tenacity and greater hardness is satisfactorily explained in the words of Howc: '(This greater strength is natural, because the amorphous state lacks the cleavages and slip planes which weaken crystalline substances." Can the greater strength and hardness claimed for small crystals be as satisfactorily explained? Nor do I think that the cold deformation of metals through successive slips within the crystalline grains can he accounted for as acceptably by the "small crystals theory."

Jan 1, 1923

By Thomas V. Falkie, Robert Stefanko

Much has been said and written recently about the manpower problem in the mining industry. The coal segment of the industry has been scrambling to staff and man its companies and operations in order to accommodate the current boom, and there are some interesting side- lights and developments which deserve further attention from coal mining people. This column will deal with the manpower problem in general and the plight of the professional-the mining engineer-in particular. At this point in the game, it is desirable and perhaps necessary to ask ourselves if there really is a manpower problem and, if so, how serious it is. Suprisingly, there are varying and conflicting answers to this question. If we are talking about warm bodies, then in most mining areas there is no problem. If, however, we are talking about skilled or trained people-at all levels-there are apparently serious shortages, especially in the coal industry and in the U. S. Bureau of Mines. To define quantitatively the present and future need for mining professionals is a formidable task, to say the least. Without pretending that these figures are anything but an educated guess, we feel there is an immediate need for about 1000 mining engineers right now and a continuing need for about 300 mining school graduates per year (double last year's number) for the next ten years in order to take up the slack, provide for attrition and maintain a normal growth rate. Mining companies, large and small, are just now beginning to realize that the industry is undergoing a revolution, It is no longer possible to design, build and operate coal mines by the "seat of the pants." Production demands, the new health and safety law and the inevitable new legislation on surface mining will require more engineering, more planning and new technology. There are mine operators who need mining engineers and don't even know that they need them. This could mean rough going for the small operator. It surely means that there will be a trend toward increasing the ratio of technical to nontechnical employees and the ratio of technical employees to dollars of capital towards levels comparable with other highly mechanized industries.

Jan 1, 1971

Albert Sauveur, Cambridge, Mass. (written discussion).— In his introductory paragraph, the author states that he has come to bury Beilby, not to praise him. The paper, however, gives the impression that while he may have dug the grave, Beilby is still at large. I am not one of those whom the author calls enthusiastic supporters of Beilby's amorphous theory and in support of this claim quote from a book I am writing: "Attractive as the amorphous theory is, and notwithstanding the ability with which it has been presented and the renown of its sponsors and supporters, it should not be accepted without reservations as a demonstrated fact.... So long as it explains more satisfactorily than other theories a greater number of phenomena in which it may play a part, we should use it in preference to others as the best available. Let us avoid the danger, however, into which too many fall, of accepting as indisputable truths, statements and theories emanating from those whom we hold in great esteem. It is not what those men themselves would wish us to do. I am entitled, I think, to occupy a position in the middle ground. Neither should Howe be classified with the enthusiastic supporters for he has written that the theory should be classed rather among the precious working theories than among those firmly established," a very wise and prudent statement. Jeffries, on the other hand, I would not hesitate to describe as an enthusiastic supporter. The author reproaches the advocates of the amorphous theory with having taken whatever properties they needed and with having assigned them arbitrarily to the hypothetical amorphous phase. He then applics their method to small crystals. If the existence of an amorphous phase is assumed, its greater tenacity and greater hardness is satisfactorily explained in the words of Howc: '(This greater strength is natural, because the amorphous state lacks the cleavages and slip planes which weaken crystalline substances." Can the greater strength and hardness claimed for small crystals be as satisfactorily explained? Nor do I think that the cold deformation of metals through successive slips within the crystalline grains can he accounted for as acceptably by the "small crystals theory."

Jan 1, 1923

The pattern of the coal industry west of the Mississippi River, so far as its history is concerned, is entirely different from that to the east of the "Father of Waters." When the Louisiana Purchase was consummated, one of Jefferson's first thoughts was to ascertain what sort of a country had been purchased, and to that end he sent Lewis and Clark to ascend the Missouri River and to reach the Pacific Ocean if possible, but above all to bring back a report showing the character of the country, its mineral and other resources, inhabitants, etc. This first expedition was supplemented by others to various parts of the vast domain for the same purpose; years later, when transportation routes were necessary to hold and develop the western country, a number of expeditions were sent to explore possible routes for railroads. The records of nearly all of these explorers, as will be shown later, contain references to coal in many localities, the possible value of which was realized but its potential value remained dormant for many years until increasing population and methods of transport made markets available. Missouri was the first state west of the Mississippi in which coal was produced and the names of a number of places show that the French were familiar with the coal deposits there. Lewis and Clark, soon after they left St. Louis, passed "a remarkable Coal Hill on the Larboard Side, called by the French Carbonere, this hill appeares to Contain great quantity of Coal."1 This hill was about seven miles below St. Charles. No other outcrops were seen by them until they had passed the present limits of the state. The Louisiana Gazette of April 9, 1805 contained an article on "The Missouri," author not stated, which said, "the short stay we have generally made among the savage nations has prevented us from making those researches, which would have supplied us with a more extensive information respecting the various mines found on the borders of the Missouri; we know with certainty only those of iron, lead and coal." In 1806 Pike passed through Missouri on his tour to Mexico. On August 17th, along the Osage River he remarked, "here the river-bank is

Jan 1, 1942

No records have been found of coal in the old Spanish documents, although some mention of it probably exists in manuscripts. Coal was found in Mt. Diablo, in Contra Costa County, about five miles south of the San Joaquin River in 1852, but the first mine, the Teutonia, was located in 1858. The deposits are located on both sides of a high ridge, and vessels of 1,000 tons burden could ascend the river to the nearest point to the mines.1 In 1854, coal was found about four miles from Oroville, on the Feather River, in Butte County. Development work was started and in 1856 a mine was opened. From the description the coal was likely a variety of lignite and probably never amounted to anything commercially, as it does not appear again in the records 2 The more valuable mines at Mt. Diablo were opened in 1859 and 1860. By 1867 there had been 11 mines started and at that time five were in operation. The seam conditions were much disturbed and lack of knowledge of them caused much waste of effort and money. All of the coal excepting that used locally and in nearby towns, was shipped to San Francisco, and largely used for steam purposes. The first receipts were in 1861-6,620 tons. A railroad to the river had been constructed and opened in February 1866. The Corral Hollow field in Alameda County was found and prospected to a small extent in 1862. Two mines were opened but little work was done and the field was then abandoned. Good exposures were rare and the cost of underground exploration was then prohibitive. The Commercial mine produced coal in 1869 and 1870, but a fire in the latter year destroyed the tipple and communications to the mine. The Livermore mine was abandoned after 18 months operation in 1875 and 1876 and no other work was done here until the nineties. In 1867 Hyne reported the presence of coal in workable thickness, and of good quality, on the property of the Pacific Coast Petroleum Company,

Jan 1, 1942

By Corale L. Brierley

An unidentified, high-temperature microbe, which oxidizes reduced sulfur and iron in an acid medium between 45° and 75°C, is studied to determine its ability to leach copper sulfide minerals and molybdenite. Copper is leached from low-grade ore as well as a chalcopyrite concentrate, and preliminary data indicate a tolerance of 1.0 gpl copper by the microbe. A molybdenite concentrate is also biogenically leached, and the microbe is able to continue growth when the soluble molybdenum concentration is 750 ppm. Molybdenum can not be biogenically extracted from waste material using the present technique. Direct observation using SEM illustrates colonial growth and developmental characteristics of the microbe on molybdenite fines. The organism responds to hexavalent molybdenum by reducing this metal to the pentavalent state in aerobic and nitrogen gas atmospheres.

Jan 1, 1974

By J. C. Crampton

Gradual shifts in the center of ore production have dictated three moves for the Pend Oreille Mines & Metals Co. plant. Capacity has grown from 300 tpd to the present 2400 tpd, and the gravity process used at the original Josephine mill has long since given way to improved flotation practice. The Josephine mill, operated in World War I and converted to flotation in 1927, treated 200,000 tons of ore rating as high as 16 pct Zn. By 1935 extra ore handling warranted construction of a new mill on a lower level, and capacity was raised from 300 to 800 tpd.

Sep 1, 1955

BEFORE an audience which included many notable members of the engineering profession, the John Fritz Medal was presented to Senator Guglielmo Marconi on July 6, 1922, in the auditorium of the Engineering Societies Building, in New York. The medal was awarded for achievements in the development of wireless telegraphy, but all of the speakers emphasized the inventor's service to mankind, in saving life at sea, especially, as well as his remarkable scientific attainments. SIGNIFICANCE OF THE JOHN FRITZ MEDAL The John Fritz Medal is presented from time to time for notable achievements in applied science, as a memorial to the engineer and metallurgist whose name it bears, one of the charter members of the American Institute of Mining and Metallurgical Engineers. The medal fund, contributed by friends of Mr. Fritz, is administered by representatives of the four national engineering societies. Seventeen awards have been made to men of eminent distinction in the various branches of the profession of engineering, whose names are more familiar to the civilized world than are the names of most of the presidents of the United States. Four of the medallists were present on the evening of July 6: Dr. Elihu Thomson, the dean of the electrical engineers, General Goethals, Orville Wright, and J: Waldo Smith, who developed the New York City water supply, system. In opening the meeting, Dr. Comfort A. Adams, president of the Board of Award, said in part: The profession of engineering knows no national boundaries. That the engineers of this country sense this fact deeply is evi-denced by the absence of any limitations as to nationality in the award of the John Fritz Medal. The engineer is seeking for the truth wherever it may be found, and it frequently happens that the most helpful sugges-tions for the solution of a particular problem are the results of the work of men of other nationalities on the other side of the world, whom we have never seen. Thus through this long range interchange of information and of ideas, there has grown up a feeling of real kinship among the engineers of the civilized world, a sense of interdependence and of the need and value of cooperation, in wide contrast with the all too prevalent sense of conflicting interests, of racial and national antagonisms of bitterness and misunderstanding. We often think of the nations of the earth as separated by walls or barriers, of various kinds and of various heights. Some of these are the natural results of evolution, for example, differences of language, customs and traditions; while others are more artificial, being maintained by law and dictated by fear, greed, and shortsightedness or ignorance. There is deep conviction that the degree in which we can abolish these barriers is a true measure of our progress towards real civilization, and that the destruction of these barriers is the only method of attaining that world-wide peace for which every

Jan 8, 1922

By Norman Brown, J. V. Rinnovatore

It was found that a shear stress applied during the recovery had no effect on the amount of recovery if the stress was less than the instantaneous yield point irrespective of the direction of the stress. Large ajplied stresses during recovery had a marked effect, which depended on the direction of stressing. Single strain reversals at -72°C not only produced the Bausch-inger effect but also increased the flow stress. The increase inflow stress was attributed to vacancies, which have appreciable mobility at -72 °C. THEORIES I-' of recovery suggest that the internal stress field of the dislocations plays an essential role. Most investigations of recovery use time and temperature as the independent variables; however, here stress has been introduced as a variable in two ways: 1) by varying the internal stress field according to the amount of strain prior to recovery and 2) by applying an external stress during recovery. Tannen- baum and Kauzrnann studied the effect of applying a stress during recovery by measuring the change in creep rate after recovery; they found that stresses as high as 95 pct of the creep stress had no effect on recovery. Earlier, Wood and scrutton6 showed that an applied stress during creep increased the rate of poly-gonization. The experiment by Wood involved poly-crystalline aluminum whereas Tannenbaum and Kauzmann used a single crystal of zinc. In this investigation, zinc single crystals were used and deformed in a manner to prevent polygonization. Thus, the main difference between this investigation and that of Tannenbaum and Kauzmann is the use of the stress-strain curve instead of creep rate as the index of recovery. In addition, the applied stress during recovery varied

Jan 1, 1961

By William E. Ford, Edward Salisbury Dana

1. Normal Class (28) Gypsum Type 2. Hemimorphic Class (29) Tartaric Acid Type 3. Clinohedral Class (30) Clinohedrite Type Mathematical Relations of the Monoclinic System Crystallographic Axes. - The monoetinic system includes all the forms which are referred to three unequal axes, having one of their axial inclinations oblique. The axes are designated as follows : the inclined or clino-axis is a; the ortho-axis is b, the vertical axis is c. The acute angle between the axes a and c is represented by the letter 0; the angles between a and b and b and c are right angles. See Fig. 331.

Jan 1, 1922

By M. F. Goudge

Production of many industrial minerals reached all-time records in 1965. In keeping with the high level of industrial activity throughout the nation, producers of many industrial minerals operated at capacity or near capacity, notably the producers of phosphate, potash and sulfur. In the case of sulfur, the demand exceeded production and orders were filled, in part, from stocks accumulated in previous years. Industrial minerals as a group continued to increase both in value and quantity at a faster percentage rate than metallic minerals and fuels, The U.S. Bureau of Mines estimated that the value of industrial minerals produced in 1963 was $4318 million vs. $2006 million for metals. Preliminary estimates for 1965 indicate that current value of production was again more than 2% times that of metals, thus making apparent their importance to the industrial life of the nation.

Jan 2, 1966

By William Metcalf

ONE of the first questions that naturally occurs to one who handles steel is," Why does steel harden ?" To answer this question the chemist and physicist have devoted much thought and experiment, and while they have enriched our store of knowledge of the nature and composition of steel, it cannot be said that they have yet solved the problem involved in its hardening. In this communication I desire to direct attention to a line of investigation yet new, in the hope that it may receive the attention of those who have the time and ability to pursue it. I refer to magnetism. There are so many parallels between the action of magnetism on iron and steel and their behavior under different processes of manipulation that it would seem as if there must be some connection between the forces at work in the different cases, if, indeed, there be not an identity of force in all of these cases. Magnetism, as we know it, may be merely the visible manifestation of forces, which may serve as a guide to lead us to an exact knowledge of the structure, the strains, and the resistances with which we have to deal in iron and steel. If a magnet be brought close to a pile of iron filings, the little pieces of iron will fly to the magnet and attach themselves to it, with their longer axes lying in the direction of the force. If molten cast iron be poured into an iron mould,-a chill,-the iron upon crystallizing will form needlelike crystals, with their long axes normal to the surfaces of the mould. If the iron is at the proper temperature and the quantity small, compared to the mass of the mould, the whole of it will be chilled, or set, in' the hard needlelike crystals

Jan 1, 1881