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By J. L. Stuck

Geological investigation and research have contributed greatly in making industrial minerals the basis of an important industry in the state. North Carolina contains a wide variety of industrial minerals and rock. Mica, feldspar, kaolin, halloysite, talc, pyrophyllite, silli-manite, and spodumene are used to illustrate the progress being made. IN a previous paper1 an attempt was made to indicate the importance of industrial minerals in North Carolina and the wide variety of such materials present. The present paper is concerned with geological investigation and research which have made industrial minerals the basis of an important industry in the state. Geological mapping has gone through three stages in North Carolina during the present century. The first stage is represented by excellent reports of which Corundum and the Peridotites of Western North Carolina,2 Volume I, now a classic, is representative. In this report, a geologic map of the western third of the state is shown on a scale of 10 miles to the inch. The next stage is represented by folios" of the U. S. Geological Survey published between 1902 and 1932. Most of these contained 30 min quadrangle maps on a scale of 2 miles to the inch. The third step is represented by reports prepared during the past 10 years which contain geological maps4 on scales varying from 500 ft to 1 mile to the inch, while many mine maps have been prepared on scales varying from 20 to 150 ft to the inch. As the scale on which geological mapping has been done has decreased, the amount of information secured has increased. Pratt and Lewis did excellent work on the peridotites of western North Carolina, but their maps lacked details. Keith and others added

Jan 1, 1952

By Elwood Haynes

As in organic nature certain animal and vegetable forms have undergone modifications, and thus, as it were, fitted themselves to live in a new environment, so it has been found possible in certain instances to form new metallic combinations which are practically immune to the natural conditions that exist on the earth at the present time. A few of the metals, such as gold, silver, and the metals of the platinum group, are found native, but the commoner heavy metals are nearly always found in the form of oxides or sulphides. For a number of years I have made experiments with a view to finding certain metallic combinations or alloys which would not only resist oxidation and other harmful influences, but would also possess valuable physical properties, which would render them fit for special service. The first decisive step made in this direction was the discovery of an alloy of nickel and chromium in 1898. The properties of this alloy have already been described in a previous paper.' Immediately following the discovery of the nickel-chromium alloy, I produced an alloy of cobalt and chromium, which has likewise been described in the reference given, but the range of proportion between the cobalt and chromium is so great, and the combination is modified to such a marked degree by the introduction of other substances, that I have felt justified in reading another paper on this subject, describing more fully my researches in this particular direction. As early as 1907 and 1908,I made alloys or combinations of cobalt, chromium, and tungsten; cobalt, chromium, and molyb-

Jan 1, 1913

By F. Selig, E. J. Couch

The following points serve to supplement the interesting theoretical study on forward combustion by Thomas, and may be of some general interest. The mathematical model presented by the author can be viewed as a first approximation to the problem of calculating the vertical burned height profile resulting from ignition of the interval | z |<h/2 in a very thick formation. However, the assumption of a given minimum combustion temperature T, would give a better approximation to the vertical burned profile if the burning height were not constrained to stay within the ignited layer. This follows from the fact that both fuel and oxygen are present in the adjacent region, |z|>h/2, and for certain combinations of process variables the temperature is sufficiently high for complete combustion to occur. In this case, the vertical coverage will first become greater than the ignited interval before cutting back to zero as the extinction limit is approached as shown in Fig. 1. Such growth of vertical coverage is possible if the minimum combustion temperature is less than the initial source temperature (r = rj) at the edge (z = h/2) of the ignited interval. But this latter temperature is equal to one-half the source temperature for the case of infinite burned height.&apos;,&apos; Thus growth will occur initially if The fact that the vertical burned height can be greater than the ignited interval complicates the picture considerably, as can be seen by referring to Fig. 1. Here burning occurs in Region A, whereas none was possible in the original mathematical model. At the same time, there is no combustion in Region B, contrary to the assumption of burning in the entire layer |z|<h/2. This apparent inconsistency suggests that the vertical coverage derived from this simple model does not adequately represent the vertical height of the burned zone. A more compatible model will result from the actual stepwise calculation of the burning length (as a function of time) that would give rise to the specified combustion temperature. This problem can be more conveniently attacked by using the temperature distribution, given by the author&apos;s Eq. 12, expressed in the integrated form:

By A. T. Schwennesen

(Wilkes-Barre Meeting, June, 1911.) EVERY engineer has occasion to trace or copy a map, plan, or other drawing on paper too thick for the ordinary way of using tracing-cloth or tracing-paper. When the figure is small and simple a copy may be made by holding the original against a window-pane, covering it with the paper, and tracing direct by the aid of the strong sunlight from outside. The need of utilizing this principle on a larger scale and in a more convenient position led Dr. J. C. Branner to plan the table of which the following is a description: This table was first made in the form of an adjustable glass-top table with a mirror beneath, in 1887, while Dr. Branner was State Geologist of Arkansas. Later it was modified as experience suggested until the form as here described was evolved. The device consists essentially of a drafting-table with a plate-glass top, upon which the original drawing and the paper are laid, and a mirror mounted underneath to reflect the light of the sky up through the drawing. The glass top is hinged and fitted with two arms and thumb-screws, so that it can be raised and fixed to any position, either inclined or horizontal. The mirror is pivoted and revolves about a horizontal axis, so that it may be tilted to any angle. The hood of cardboard or black cloth prevents the reflection of light from the tracing, and may or may not be attached to the table. The apparatus is set up before a window through which part of the unobstructed sky is visible. The mirror is then adjusted like the reflector of a microscope, so that the skylight is reflected up through the drawing. If the mirror can be so located that the direct rays of the sun are reflected through the drawings, thicker paper can be used. The map or drawing may be held in place by clips screwed

May 1, 1911

By G. W. Nabor, M. Mortada

The effects of anisotropic or directional permeability on the areal sweep efficiency and the flow capacity are examined. The paper points out the importance of taking directional permeability into consideration in planning a flood. It analyzes the two-dimensional flow pattern associated with the skewed line drive for a unit mobility ratio. The direct and staggered line drives are treated as special cases of the skewed line drive. Analytical expressions are developed for the areal sweep efficiency at breakthrough and the flow capacity. They are related to the spacing between like wells, the distance between a row of injectors and the nearest row of producers, and the degree of skewness of the line drive. The latter quantity is defined such that it is equal to zero for the direct line drive and equals one-half for the staggered line drive. The areal sweep efficiency and the flow capacity depend also on the orientation of the flood pattern with respect to the principal axis of anisotropy. The paper provides a simple method for determining the areal sweep efficiency and the flow capacity for a formation in which the permeability in the bedding plane is anisotropic. INTRODUCTION Directional or anisotropic permeability is manifested by the ability of the formation to conduct fluids more readily along certain preferred directions. This situation occurs in many producing formationsl-4 and is usually attributed to depositional features in which the sand grains are oriented in a preferred direction. In some cases it results from the formation of a major and a minor fracture system. 4 Directional permeability should be taken into account in many phases of the production and exploration activities. Recognizing its existence in the formation of interest and planning accordingly can lead to increased recovery and substantial savings. For instance, the areal sweep efficiency in a water flood depends to a great extent on the orientation of the flood pattern with respect to the principal axis of permeability. Anisotropic5 permeability is specified by the directions of its three principal axes and the permeability along each axis. The principal axes of permeability are mutually perpendicular. This paper deals with the areal sweep efficiency at breakthrough and the flow capacity for formations with aniscltropic permeability. The flood pattern considered consists of alternate rows of injecting and producing wells. The rows of wells are parallel and form a developed, skewed line drive which is illustrated in Fig. 1. The staggered and direct line drives are treated as special cases of the skewed line drive. PRELLMINARY CONSIDERATIONS The formations considered in this paper are assumed to be of uniform thickness and porosity. The permeability is uniformly anisotropic, with each principal axis of permeability maintaining

By Bruce H. Gardner, Stephen A. Miller, Shosei Serata

The Bryan Mound salt dome in Freeport, Texas, has some of the largest and oldest solution caverns in the U.S. There are a total of five caverns of varying shapes and sizes randomly distributed throughout the salt dome. When the caverns were converted from a brine production to an oil storage operation, the effects on long-term stability of the caverns and inter-cavern behavior were analyzed to evaluate the future safety of the storage operation. The analysis was based on a worst-possible-case scenario, including accidental wellhead pressure loss. The impact of this pressure loss upon the thinnest partition between the two closest caverns was analyzed, using a case example of storing lightest weight LPG, thereby creating maximum differential pressures between these two caverns. The finite element method with the REM computer code was utilized for this analysis. Results of the analysis illustrate the basic mechanisms of the long-term behavior of the multiple caverns in the LPG storage operation.

Jan 1, 1985

By Wilbur Nelson

ALL of our accounts of the discovery of copper ore at Ducktown, Tenn., state that the discovery was made in August, 1843, yet it would appear that samples of copper from this district were found by the Spanish explorer, DeSoto, when he wandered into Southern Tennessee, in 1539, in his four years of exploration through the Southern States. The following quotation is taken from his diary: "Towards the north there was a province named Chisca; and that there was a melting of copper, and of another metall of the same colour, save that it was finer, and of a farre more perfect colour, and farre better to the sight, and that they used it not so much, because it was softer. And the selfe same thing was told the governor in Cutifa-Chiqui, where we saw some little hatchets of copper, which were said to have a mixture of gold. But in that part of the country it was not well peopled; and they said there were mountains, which the horses could not passe; and for that cause, the governor would not goe from Cutifa-Chiqui directly quicker." DeSoto sent two of his company to try to find these mines, but after five days&apos; wandering through the mountains they returned, stating that their guides had become lost. Although the Ducktown area may have been known to the ancient Indians, it was not until August, 1843, when a Mr. Lemmons, who was panning for gold on Potato Creek, in the Ducktown basin, found some reddish-brown decomposed rock, which he supposed to be gold, that the copper deposits were actually discovered. His disgust on finding that this yellow metal. was not gold was so great that he did not. try to develop his find. In March, 1847, B. C. Dugger erected an iron forge at this same place, but was unable to work the iron as it contained so much copper that on cooling it would break to pieces. The finding of copper in the iron ore by Mr. Dugger led to further explorations; and in April, of the same year, A. J. Weaver, who was passing through that country, told the people that the black rocks they had dug out were rich copper ore. Mr. Weaver began the first mining in this district.

Jan 10, 1924

By R. A. Blake

Measurements of the quantity of xanthate abstracted from mineral surfaces and put into solution by an increase in the hydroxyl ion concentration were made. A residual xanthate concentration of 59.6 ppm was found in one case at a pH of 11.8. The abstracted xanthate is capable of acting as a collector on fresh mineral surfaces under proper conditions. It was learned that as the hydroxyl ion increased and the xanthate abstracted, the coarse particles lose their floatability first. A volume weight relationship based on percentage coverage was established and seems to offer a reasonable explanation of the cause of observed results.

Jan 1, 1973

By L. H. Hart

Because of a widely recognized association between breccia pipes of one form or another and many important copper deposits, conditions under which breccia pipes develop have been of great scientific interest for many years. Since these phenomena first attracted attention, many theories have been advanced to explain their origin. This is not unexpected, since it is likely that they have been formed by and under a wide range of conditions. Moreover, the entire subject is confused by the fact that the term breccia pipe is applied to a wide variety of occurrences. To discuss any part of the subject intelligently, therefore, it is necessary to start with definitions of the terms used. In their discussion of the Toquepala deposit, Richard and Courtright have carefully defined the terms they have used in their presentation of a very logical geo- logical history of Toquepala breccias. This is a real contribution, as there is no reference in the literature known to the writer where the history of a series of breccia pipe epochs, confined essentially within one channelway, may be read with the degree of certainty that appears to be possible at Toquepala.

Jan 6, 1958

W. D. BRENNAN,* Cheyenne, Wyo. (written discussion?).-My experience has been that, where possible, it is preferable for each foreman to employ his own men, rather than to have them handled through an employment bureau. The fact that each foreman comes into direct contact with the man before he is put to work gives him an opportunity to choose, at certain times, the kind and class of men that he wishes. Where possible, after a man is employed he is sent to a central office where a complete history of each individual is kept on a card. If a man has previously been in the employ of the Company, his history can be obtained from this card, and if for any reason he is not wanted he can be refused work at the time he reports to, the central office. In connection with Workman&apos;s Compensation costs, we in Wyoming feel that although the rates of compensation paid may in some cases be rather low our law works satisfactorily. As the State and the number of employees are small, compensation cases are handled through Judges of the various District Courts. In the State Treasurer&apos;s Department, a few clerks were added to look after the handling and issuing of warrants and compiling of statistics. Most of the large employers have an arrangement by which a joint claim and assent, specifying the amount of compensation due, is made tip by the employer and signed by the workman. This is forwarded, to the Judges so that personal investigation of individual cases is not necessary. In this manner, compensation is promptly received and&apos; overhead expenses of operation of the law is kept at the minimum. The law requires each employer to pay into the State Treasury, for the benefit of the industrial fund, a sum equal to 1.5 per cent. of the money earned by each employee, engaged during each calendar month of such employment. Each employer contributes monthly, unless the sum heretofore contributed, after deducting all payments made on account of injuries to his employees, shall equal a full 1.5 per cent. of his annual pay roll, computed by multiplying his current monthly pay roll by twelve, and shall likewise be not less than ($5000). It has been found during the years that this law has been in effect, that a number of the larger employers have been exempt from payment for from five to eight months per year, so that in some cases, even in coal nines, industrial insurance has cost less than 0.75 per cent.

Jan 3, 1919

By Lawrence Veiller, D. Eppelsheimer

D. Eppelsheimer, * Middletown, Ohio.—The housing of employees has so many and so varied aspects that in order to reach even an approximately correct solution it is necessary to have in mind a few fundamental principles; but it is not possible as yet to write these housing principles in the clear and correct form that is possible with many of our natural laws. Manifestly, the problem depends first on the kind of people it is necessary to house. What is suitable for the Southern unattached negro is not suitable for the married skilled American. The influx of colored labor has affected quite a number of what were satisfactorily housed communities. The second important factor is the relative proportion of the number of employees to the total employable population of the community in which the industry is located. The employer of a hundred men in a large city has little responsibility in the matter of housing his employees. If he employs 75 per cent. of the employable population in a community of 27,000, as is the case of the company with which the writer is connected, it means a large responsibility. In the establishment of an entirely new plant in a more or less isolated place, the responsibility becomes greater. As engineers, we design and write the specifications for the machinery to accomplish a definite purpose, and proceed to house it, provide the necessary buildings with their accessories in the way of cranes, or heating systems, or sprinkling systems, as the case may be. There is no reason why the operating force should not be built up in very much the same way: design the organization, write its specifications so that the employment department can secure the proper men, and then house that organization with just as much thought and care as is given the plant. In the plant, the various machines will work along certain definite lines and accomplish certain results; but even if we start with the proper organization it takes considerable time to get that organization working together. One of the most important elements to this end is the proper housing of the organization. A man usually spends more time at home than at work. Proper surroundings and a comfortable, convenient house of good appearance exercise an influence that cannot be denied, and an employee situated in such surroundings is far more inclined to follow the policies of his employer and take an active part in furthering them than one dissatisfied with his home and surroundings, which feeling

Jan 1, 1919

By N. K. Chen, R. Maddin

Columbium single crystals were deformed in tension and compression. Reorientation by X-rays and stereographic projections of slip traces indicate that plane of slip may be considered as (110). The plastic behavior is shown to be quite similar to the deformation of molybdenum single crystals. STUDIES on the crystallography of the deformation process in body-centered cubic metals have been renewed recently with investigations of iron single crystals1-" and molybdenum single crystals.4 It is now apparent that too many exceptions to the rationalization based upon the ratio of absolute testing temperature to absolute melting point by Andrade5 exist to permit more serious discussion of this type of analysis. The considerations of resolved shear stress utilizing only planes of the type {ll0}, {112), and {123)³,6 permit analysis of the deformation only on the basis of those three types of planes. The suggestions made by Elam7 and by Greninger8 in which the slip process is envisioned as a composite slip on two nonparallel {110) planes can be illustrated schematically in Fig. 1. It may be seen that an unresolved trace on any plane containing a <111> direction may be accomplished by varying the number of atoms participating in the composite process. By further varying the number of atoms in each plane but keeping the ratio of participating atoms constant, jogs could be obtained in the traces and hence wavy slip lines could be produced. Vogel and Brick&apos; studied the behavior of a iron single crystals in which they suggest that the plane of glide is "non-crystallographic" and may be predicted from the intersection between the great circle joining the slip direction and specimen axis with the great circle whose zone axis is the slip direction. In a more recent investigation on iron single crystals, Steijn and Brick" suggest that the slip mechanism may be considered as made up of a type of composite slip occurring on {110} and {112} planes. Evidence for a possible composite nature of the slip process has been presented for the case of molybdenum in the form of analysis of asterism and specimen axis rotation." Definite proof of a composite slip process must, however, await good electron microscopic resolution of the individual traces making up the unresolved optical trace used in determining the acting slip plane. The present investigation was undertaken to study the behavior of columbium single crystals not only in tension but also in compression since the specimen axis migration should indicate the plane or planes of glide in the same manner that the specimen axis migration in tension indicates the direction of glide. The orientations of eleven crystals investigated are shown in Fig. 2. Specific orientations are missing (those in the vicinity of [Ill] and [001] and consequently the effect of orientation on the crystallography of deformation could not be considered. Experimental Procedure The 1/8 in. rods (7 in. long) were subjected to an axial tension in vacuo while at temperatures in the vicinity of 2000°C for 2 to 4 hr. This treatment resulted in large cylindrical grains (about ½ in. long) occupying the entire cross section. A number of these rods were used for the tension studies by observing the behavior of the individual grains. For the compression studies, single crystals approximately % in. long by 1/8 in. in diameter were cut from the rods; the ends were ground parallel. All specimens were polished electrolytically in a solution of 15 cc HF(48 pct) and 85 cc H2SO4 (concentrated) using a platinum cathode, a current density of 0.04 amp per sq cm and a temperature between 25" and 60°C.10 Orientations were obtained using a Laue back-reflection method (3 cm film to specimen distance) with a ½ mm collimator 9 cm long. For the compression specimens, a reference mark was scratched on one of the compression sur-

Jan 1, 1954

By W. Hume-Rothery

IN recent interesting papers,1,2 Bardos et al. have described ternary Laves phases of the type A2(BsSi) and A4(B5Si3) where A = titanium vanadium, niobium, and so forth, and B = manganese, iron, cobalt, or nickel; other more complex formulae have also been established. In these phases, silicon plays the part of the smaller B atom of a Laves phase AB2, and the interatomic distances show that the effec- tive silicon radii lie between 1.16 and 1.21Å, and are thus very much smaller than the metallic radius of silicon for CN = 12. It does not seem to have been pointed out that these small atomic radii are almost the sape as the normal covalent radius of silicon (1.174Å). If, therefore, silicon acts as an acceptor of electrons as suggested by Bardos et al.,1 it appears to do so, not by the building up of a negatively charged silicon ion which would be large, but by the formation of what are very nearly or may be actually normal covalent bonds. Since a covalent bond contains two electrons, its formation would reduce the number of electrons available for bonding in other parts of the structure, and in this way the effect of silicon in stabilizing the o phase at high electron concentrations might be understood.

Jan 1, 1965

MINING and Metallurgy closed the year 1928 showing a small profit, the receipts, exclusive of the charge against members, dues for subscriptions, having been $43,067.81, and expenditures $40,925.58. In accord with the policy of the Board the budget is made each year with the purpose of balancing the accounts rather than the maximum of profit from the undertaking since it is the service the journal performs for members that justifies its existence. This service is being constantly increased. Within the year a number of changes have been made in the dress of the magazine, a new cover adopted, color more frequently used, and illustrations more generally employed. These changes seem to have been appreciated both by readers and advertisers. More space has been devoted to papers read before local sections and to the news of their activities. It is believed that this has helped materially in sustaining and increasing the interest in such meetings. The general, regional, and division meetings have also been fully reported and news of Board meetings, of the work of the various committees, of the employment service and other activities of the Institute has been spread before its members month by month. The 570 pages of reading matter printed in the course of the year constitute not only a record of what the Institute was doing but of what the most representative sections possible of the members of the mining and metallurgical professions were thinking. With 9000 members scattered around the world, occupying key positions in the industry, the Institute affords through its own journal an unsurpassed medium for broad contact and enables the readers with the minimum of expenditure of time and at no extra money expense to keep a general contact with the whole range of subjects touched by miners and metallurgists. In these days of intense specialization but rapid change such contact is particularly valuable. The more formal papers presented to the Institute are published in the Transactions, Technical Publications and the special volumes. Mining and Metallurgy carries abstracts of all papers published ,by the Institute and prints in full the shorter, less detailed papers and those which reflect work in progress rather than finished. Such papers have a news value which is supplemented by editorial comment, discussion by members and others, and the actual news of the organization itself. Without therefore attempting to fill the place of a general news sheet, it has a timeliness that gives it an immediate value much appreciated by the readers. In accord with the general policy of the Board every effort will be made constantly to improve the quality of the magazine to the full extent that its revenue will permit. Your Committee feels that, through the intelligent cooperation of the official staff in the office, Mining and Metallurgy has been improved in

Jan 1, 1929

By Francis L. Bosqui

The following paper embodies a report which I made on the filter-press treatment of slimes at the Liberty Bell mine, Telluride, Colo. At the time this report was submitted, the management deemed it wiser to defer the installation of so costly a plant as the one required, in the hope that some of the many investigators in the field might soon evolve a cheaper and more perfect method of slimes-treatment, and one better suited to the conditions at Telluride. The Liberty Bell ore consists essentially of quartz and clay, with iron pyrites disseminated through the quartz in very fine particles. There is considerable iron and manganese stain in some of the ore, the latter especially in the clays, which are sometimes quite black. Occasionally particles of galena, zincblende, gray copper and a few other minerals are seen, but they are comparatively rare, and not in sufficient quantity to affect considerations of treatment. Free gold is occasionally seen in the quartz, and one or two instances of mire silver have been observed. The milling-plant consists of an 80-stamp amalgamating mill which crushes through 20-mesh screens; 20 Wilfley concentrating tables, taking out, in iron sulphides, about 2 per cent. of the total ore crushed; and a cyanide plant consisting of two tiers of 33 ft. vats, five in each tier, fed by revolving pipe-die tributers. The slimes overflow from the upper settling tanks through gates with adjustable outlets, and thence to a large canvas-plant, which efects only a small saving. This slimes product, of which about 100 tons escape per day (or 38 per cent. of the total ore crushed), contains about 3 per cent. of dry solids. Of this approximately 93 per cent. will pass a 200-mesh screen. The slimes range in value between $3.90 and $4.87 per ton, the values being about equally distributed between gold and silver. The actual averages for ore and slimes during the years 1900-

Jan 1, 1904

CONTENTS PAGE THOENEN, J. R.-Limestone Production as a Mining Problem. Discussed by Oliver Bowles, J. T. Singewald, S. R. Russell 1 GRIGGS, C. C.-Engineering in Limestone Production. Discussed by W. C. Phalen, John Rice, Samuel M. Shallcross, Oliver Bowles, Nathan C. Rockwood, George Milliron 2 WILDER, FRANK A.-Rotary Calciners for Gypsum. Discussed by L. K. Arm-strong 9 PORTER, JOHN J.-Manufacturing Problems of Cement Industry. Discussed by Samuel M. Shallcross 9 KIRKHAM, VIRGIL R. D.-Phosphate Deposits of Idaho and Their Relation to the World Supply. Discussed by F. A. Wilder, S. L. Willis, G. R. Mansfield, R. W. Stone, L. K. Armstrong 9 Limestone Production as a Mining Problem Discussion of the paper of J. R. THOENEN, presented at the New York Meeting, February, 1925, and issued, as Paper 1417-H, with MINING AND METALLURGY, February, 1925. OLIVER BOWLES, New Brunswick, N. J.-I am so thoroughly convinced of the growing importance of underground work in the production of limestone that I had the author make a detailed study of limestone mining for the Bureau of Mines and prepare a report on the principles of limestone mining. Many limestone operators, long accustomed to open¬pit work, are being forced to mining. About 6 months ago I thought there were twenty-five or thirty underground limestone operations in the United States but the author has been finding new ones until his list now runs nearer sixty. Some of these are very extensive; one at least has 4 ½ miles of underground workings. There is an ever-expanding field for the engineer in the operation of limestone mines and quarries. Some of the larger companies realize the need of skilled engineering advice, but many of the companies regard the engineer as an unnecessary expense. Although almost every metal mine, even those handling only a few hundred tons of ore per month, employs a mining engineer, many limestone operations ten times as large employ no mining engineers. Few mining engineers are at all familiar

Jan 6, 1925

By A. Q. Tool

THE necessity of accurate temperature measurements in the glass-making industries is today being much more widely appreciated than in the past. The introduction of the modern simplified and perfected pyrometric methods in connection with exact regulation of furnace temperatures has caused a marked improvement in the glass product with a quickened rate of production. An example of the processes in which much improvement has been and still can be made is that of annealing or heat-treating the glass. This is one of the most delicate processes in glass manufacture and one that requires a most careful furnace control. The heat treatment is undertaken to decrease the possibility of breakage and, in glass for fine optical instruments, to prevent serious warping of accurately ground and polished surfaces and to make the glass more uniform throughout to the passage of light waves. These objects are accomplished by removing all the harmful stresses that exist in a piece of glass when it has been cooled too quickly or unevenly. Such stresses exist, for example, after it has been pressed, cast, or otherwise worked. Thus the process of annealing consists of heating the glass evenly to the temperature at which it softens just enough to relieve these stresses in a reasonable time and then cooling slowly and uniformly until the glass hardens again. Accordingly, the things that must be investigated and determined in order to anneal glass without loss of time are, the annealing temperature, the time that the glass should be held at this temperature while the stresses relax, and the quickest cooling procedure that will give satisfactory results. After these characteristics of the glass are known the problem is one of pyrometry and temperature control entirely. In cases when it is known that a glass article will be required to withstand some definite type of heat or mechanical shock it is often possible, by a proper heat treatment, to produce such a distribution of the stresses in the glass that it will be enabled to resist these shocks more effectively.

Jan 9, 1919

By C. W. Vaupell

THE Huitzuco mines lie in north central Guerrero, Mexico; production has been about 90,000 flasks of quicksilver since 1873. Near-surface ores fill extinct mud geysers and the deep deposits are chambered veins, stock-works in brecciated blocks, and replacements in limestone. The epigenetic minerals livingstonite, stibnite and sulphur occur in limestone, gypsum and dolomite through a developed vertical range of 260 meters. The deepest workings expose an increased amount of stibnite, which probably indicates that the lower limit of mercury mineralization is being approached. A resur-gence of heat and water formed geysers over an extended area after the period of mercury mineralization. Mud geysers, which are situated, in the outcrops, contain the secondary mercury minerals, cinnabar and barcenite in the gravel and mud filling the vents. A 150-ton flotation plant is in operation concentrating stope fills that assay 3.0 kg. of mercury per ton. In one open stope, which is more than one hectare in area and 60 m. high, 150,000 tons are available.

Jan 1, 1937

By Charles A. Kumke

The (&apos;slot" system of mining in use at the Golden Queen mine, Mojave, Calif., does not involve any new mining methods. It is, however, a new combination and adaptation of several stoping systems in common practice. The first plans for stoping operations at the Golden Queen mine called for ordinary shrinkage stopes. The hanging wall of the vein, where exposed, is a very hard felsite with a dip varying from 50° to 70°. The vein itself is quartz, shattered and fractured enough to make it easy to drill and blast to a clean hanging wall. There is no well defined footwall. The footwall limits had to be determined by assays as the metal content faded out into the felsite. Two shrinkage stopes, each approximately 200 ft. long, were laid out and started on the 200-ft. level. One of these stopes, varying in width from 8 to 18 ft., was carried on up to the top limits of the ore, approximately 120 ft., without a break in the operation. The shrinkage system proved entirely satisfactory and low costs resulted from this operation. In the final drawing of this stope, two timbermen followed down on the ore, scaling the hanging wall clean of small fragments and placing an occasional long stull from foot to hanging wall where it was deemed necessary. Few such stulls, however, were required. The hanging wall stood up very well until the stope was entirely emptied of ore. Waste fill was then put into the stope by the glory-hole method, through a waste raise that had previously been run to surface from the middle of the stope. The second shrinkage stope ran into difficulties about 35 ft. above the sill floor. Up to this point the maximum width of the ore had been about 15 ft. The ore suddenly widened into the footwall to a distance of 40 ft. in the north end of the stope. In extending the stoping operations over this, width, it was soon found that the vein material would not arch and support itself. Drilling in this end of the stope was then entirely too hazardous, and all operations were stopped. The ore was drawn through the chutes below as rapidly as possible and as soon as the stope was entirely

Jan 1, 1937

By William C. Peters

The pre-production interval, beginning with the recognition of an orebody&apos;s best potential and ending with significant production, contains time-dependent conditions well appreciated by miners but not always understood or appreciated by the landowners, investors, and legislators with whom a miner must deal. The expression persists, even outside of Western fiction, that someone has "found a mine." From a slightly more knowledgeable position, the question is asked "How long does it take to make a mine?" and an all-encompassing answer is expected. By scanning the discovery and development history of hundreds of mines and rejecting those which involve rehabilitation or expansion of older mines, some generalizations can be attempted. It should be kept in mind that while physical conditions involving the geology of the orebody and the geographic surroundings do not change markedly with time, technologic and economic conditions do change from year to year. The new methods, facilities, markets, land tenure, and politics form a pattern in which today&apos;s mines are made and which do sometimes modify the pre-production interval.

Jan 8, 1966