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By Arthur Gray

THE thermal analysis of a metal or alloy is ordinarily made with the aid of heating and cooling curves, in which transitions are indicated by the rapid changes in curvature that accompany .changes in the rate of heat absorption or evolution. Analysis by the method that depends on the change in thermal expansivity is not customary, partly, at least, because of the difficulties involved in making the necessary measurements. However, under certain circumstances, the dilatometric method of analysis may possess advantages over the thermometric method that will justify the additional trouble required. The addition of 1 per cent. of zinc to an alloy has been found to produce, upon the volume changes that take place during transition, effects that suggest the possibility of using the dilatometric method of thermal analysis as a rather sensitive means of obtaining chemical information. Although the illustrations presented in this paper are drawn from data obtained during an investigation of dental amalgams, similar phenomena can doubtless be observed with other alloys. Some of the results found during an investigation made in 19171 have been confirmed by data on the thermal expansivity of amalgams published by Souder and Peters of the Bureau of Standards in reporting tests of dental materials.2 Although the Bureau of. Standards made experiments for the purpose of discovering effects of including zinc as one of the constituents of a dental alloy-a matter much discussed in dental literature but without the presentation of reliable experimental evidence to support the views of ;either side-the reports of the test made by the Bureau give the impression that certain striking phenomena associated with the presence of zinc were not noticed. Among such phenomena are those connected with the conditions that determine whether or not a specimen of amalgam becomes covered with droplets from which crystals develop.

Jan 9, 1920

By E. C. Harder

Few mineral deposits have in recent years attracted such general and widespread attention as the Brazilian iron-ore depositis…

Jan 1, 1915

Without doubt Arizona was the scene of the first use of coal in North America, that by the Hopi Indians as early as the 10th century in burning their pottery and in heating their houses and kivas (ceremonial rooms). As has already been said this is the only use of coal by Indians of which we have any knowledge, but it has been well established through investigations conducted by the Peabody Museum of Archaeology and Ethnology of Harvard University. The apparatus for burning was crude, but they did have fireplaces and chimneys which would draw. The evidences of coal use were found in the Jeddito Valley, in Navajo County, during the excavation of the pueblo of Awatovi, only a short distance from the Keams Canon School. "Many fire pits and primitive stone stoves containing coal ash have been found in the houses, and in most of the kivas built between 1300 and 1600, two firepits have been found, one containing wood ash exclusively and the other coal ash."' The expedition of 1939 found that coal was used much earlier than this, as stated above. It is probable that these Indians were using coal regularly before it came into general use in England and northern Europe. Apparently the use of coal was largely stopped about the time the Spaniards came to that country. The ruins are located on the southern edge of the Black Mesa and the coal seams outcrop on the mesa edge below the ruins. "The coal occurs principally in one large seam which varies from a foot and a half to six feet in thickness."1 This coal is sub-bituminous and burns well, leaving a large percentage of white ash. Another seam is found about 40 ft. above this large seam; it is from six inches to a foot thick and burns to a red ash. Both of these seams were used and coal from the larger seam was used at other houses in the valley. The pottery was usually burned close to the coal seams, and the coal was used to obtain a uniform and satisfactory color. In the Jeddito Valley, the mining was done by stripping, and the methods used are described as follows by J. 0. Brew and John T. Hack, the investigators.

Jan 1, 1942

By Howard Willey

MINING operations of the Charcas unit at present are limited to the Tiro General mine at Charcas, in the State of San Luis Potosi, Mexico. The Tiro General mine was first operated during the Spanish occupation of Mexico for rich silver ores in an oxidized zone along the outcrop of the principal vein. In depth the ore is a complex sulfide with widely varying proportions of sphalerite, argentiferous galena and chalcopyrite; and until recent years, it was economically impossible to carry on mining otherwise than irregularly in sections of the veins richest in galena and chalcopyrite. The advent of selective flotation brought the orebody as a whole within the field of economic interest, and a flotation mill of 650 metric tons daily capacity was constructed in the year 1925. The mining of partly worked-out sections of the mine, as well as the very heavy ground in most of the stopes opened in virgin ore, presented an unusually difficult problem. This -paper describes the so-called "filled top slice" stoping method finally adopted as the standard system.

Jan 1, 1930

By A. R. Kinkel

Robert T. Walker and Woodville J. Walker (Walker Engineering Corp., Salt Lake City)—Mr. Kinkel's article embodies, in condensed form, the results of the first detailed and complete geological survey that has ever been made of the long neglected but potentially very important West Shasta Copper-Zinc district, in Shasta County, California. In view of the difficulties of the terrain and the complexity of the geological structure, this represents a notable achievement, and it is with regret, therefore, that the writers find it necessary to differ from Mr. Kinkel's conclusions on two important points. The first has to do with the interpretation of two members of the stratigraphic column of formations in the district; for purposes of comparison, the description of these two members according to Mr. Kinkel is shown parallel to the description of these members according to the writers, see Fig. 14, Mr. Kinkel's nomenclature being used. The first member, which Mr. Kinkel terms the upper unit of the Balaklala rhyolite, consists of a single, massive, homogenous body of very silicious igneous rock, consisting almost wholly of quartz and albite, and averaging about 80 pct silica. Most geologists of the U. S. Geological Survey who have previously inspected the district have called it an alaskite. It is not a pile of several members, but is a single unit, without internal subdivisions. It has the form of a recumbent lens, approximately flat on the bottom and arched on top, several miles in diameter, and attaining a maximum thickness of 1000 to 1200 ft. It varies in texture from porphyritic to holocrystalline, and contains unusually large quartz phenocrysts up to 4 mm diam. Mr. Kinkel considers this formation to be a thick lava flow that is older than the overlying Kennett shale, while the writers interpret it as being intrusive, constituting a domed sill or laccolith that is younger than the Kennett shale. Their reasons are as follows: 1) This formation shows none of the features which within the writers' experience invariably accompany very silicious lava flows. Nowhere is it vesicular; nowhere does it contain any glass or its devitrified equivalent; nowhere does it contain flow breccia; and nowhere has it a ragged top, in spite of the fact that there is no evidence of surface erosion, which might have removed such a top.

Jan 1, 1957

By O. M. Schaus

GRATIFYING progress continues towards the elimination of the hazards confronting health and safety in and about mines. Employers and employees are diligently co-operating. One of the outstanding movements towards this end is the National Safety Competition conducted by the U. S. Bureau of Mines. William W. Adams, of the Bureau, has stated that "Through 1936 there has passed by a dozen years of this National Safety Competition, as it started in 1925 with an enrollment of 210 mines and quarries in 28 states and 68 million man-hours of employment. For 1936 it covered 328 mines and quar-

Jan 1, 1938

By W. Chubb

FOR the past several years there has been considerable interest in the development of zirconium and zirconium alloys for application in nuclear reactors. In a portion of the development work being conducted, attention has been given to the development of high-strength zirconium alloys. One of the most outstanding alloys developed in the course of this work is Zr-4 wt pct Sn-1.6 wt pct Mo.' Fabrication and Test Methods Over 50 ingots of zirconium containing either tin and molybdenum or both have been evaluated in the process of selection of an optimum composition. Most of these were prepared as 20-g are-melted buttons; a few were prepared by induction melting. All ingots were prepared by the me of Foote Mineral

Jan 1, 1958

By Harrison Schmitt

DURING the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. HANOVER, NEW MEXICO The Hanover; New Mexico, zinc deposits were briefly described by Lindgren and others,1 Paige2 and recently in more detail by Schmitt.3 These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive 3/4 mile wide and 2 1/2 miles long (Fig. 1). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike; thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1933

By J. W. Axelson

CRUSHING has always been a major operation in the chemical and metallurgical industries, yet little is known about the theory of crushing, and today, the design of crushers is still based almost entirely on empirical knowledge and accumulated practical experience. In view of the increasing national need for the economic working of poorer grades of ores, the lack of a fundamental under- standing of this unit operation hardly presents a satisfactory situation. Basic investigations of crushing have been concerned mainly with three phases of the problem, 1-the mechanism of the fracture process itself, 2- the particle size distribution of the crushed product, and 3-the relationship between the energy input and the amount of new surface produced. Probably adequate information on these phases will be required for a comprehensive understanding of the process of crushing. A bibliography covering these phases will be given as well as a review of the work done in recent years at the University of Minnesota on the relationship between the energy input for crushing and the amount of new surface produced.

Jan 12, 1951

By R. P. Dolan, W. M. Shedd, B. L. Buchanan

Analytical expressions are derived from empirical data relating the basic physical device parameters to the radiation dose. To put in perspective and justify the approach taken, the overall problem and methods of attempted solution of radiation damage to transistors in a missile or satellite environment is briefly examined. The main emphasis is on a new criteria for neutron radiation hardness and the device design implications resulting from using this criteria. Contrary to other derived criteria, the derived bipolar hardness relation depends mainly on the initial lifetime rather than the base transit time. It is shown, that contrary to previously accepted beliefs, the inherent attainable radiation tolerance of JFET's is at least a factor of ten greater than the radiation tolerance ofbipolars. Experimental results on JFET's designed for maximum neutron radiation tolerance are presented. The accuracy, utility, and range of possible validity of various published lifetime and carrier removal damage constants are discussed. It is well known that transistors are subject to damage due to radiation at much lower radiation levels than those which would cause structural damage to a missile or satellite. The three principal categories of radiation damage to transistors are displacement, ionization, and thermomechanical. The main cause of displacement damage is fast neutrons, and the main effects which permanently degrade transistor operation are minority carrier lifetime reduction and carrier removal. A second-order effect is mobility reduction. The main cause of ionization damage is gamma radiation which results in permanent effects due to charge build-up in the oxide and transient effects due to photo-current generation. The transient effects are usually handled by using circumvention techniques in the electronics system. The extent of the transistor degradation due to displacement and ionization damage depends strongly on the transistor type, whereas the extent of thermomechanical damage does not depend on the transistor type, but depends mainly on packaging and metallization which are common to all transistor types. The standard transistor types are categorized in Fig. 1 and typical cross-sections are shown in Fig. 2. The original reason for the designation of the two classes of transistors was that the unipolar operation depends on only one carrier (majority) and the bipolar operation depends on both minority and majority car- riers. The bipolar is then seriously degraded by minority carrier lifetime reduction, whereas the unipolar or field effect transistor is not. One of the two principle classes of field effect transistors, the junction field effect transistor (JFET), depends strongly on carrier removal. However, the insulated gate (MIS) is little affected by either carrier removal or lifetime changes, but is virtually eliminated as a radiation resistant device because of permanent charge build-up in the insulator caused by ionizing radiation. The bipolar and JFET suffer only minor effects due to charge build-up in the oxide passivation when compared1 to the MOS. This is because the active region of the MOS is adjacent to or part of the oxide layer. It is then the bipolar and JFET which are potentially resistant to permanent radiation damage. DERIVATION OF RADIATION TOLERANCE RELATIONS Criteria. The bipolar is by far the most widely used transistor type. The usual criteria for hardening bipo-

Jan 1, 1970

Jan 1, 1961

By W. B. Dancy, A. Adams

Laboratory test work on heavy liquid separation of sylvite from halite is reported. Numerous tests were run on sylvite ore sized in the ranges of 4x20 mesh, 10x65 mesh, 8x100 mesh, -8 mesh and -10 mesh with heavy liquids in the range of 2.05 to 2.15 sp gr. From the test results, it was concluded that, with the type of ore under study and a size in the range of -8 mesh, a recovery as high as 90% could be achieved with a product grade of 70% KCl. However, a final product at an acceptable recovery cannot be made with one pass, and the float must either be further processed with heavy liquids or dried and sent to a conventional froth flotation circuit. Potash ores occurring in this country consist essentially of sylvite and halite plus minor amounts of magnesium sulfate salts and montmoril-lonite-type clays. Recovery of potash minerals from evaporite ores in the North American potash fields is accomplished almost exclusively by use of amine flotation. European practice involves froth flotation as well as solution-crystallization processes. Laboratory and pilot plant test work has been reported in Europe and the U. S. on the application of heavy media separation to potash ore beneficiation. Work was probably discontinued because of lack of ore with the required very coarse liberation characteristics (1/8 to 1/2 in. liberation size). Sylvite, with a gravity of 1.99, and halite, with a gravity of 2.17, appear to be ideal for separation by heavy liquids, which are now available in gravities from 1.59 to 2.95. This paper reviews preliminary results obtained from laboratory test work on heavy liquid separation of sylvite from halite. TEST WORK The heavy liquids used in the tests under discussion were chlorobromethane, with a specific gravity of 1.923, and dibromethane, with a gravity of 2.490. These liquids, completely miscible, were combined in the proportions needed to give a mixture having the desired specific gravity. Feed for the laboratory tests was mine-run ore screened to the desired mesh sizes. In conducting the tests, the sample was fed at a constant rate into a stream of heavy liquid and the mixture directed into a small separatory vessel. The float overflowed into a collecting pan while the sink collected in the bottom of the separatory vessel and was removed at the end of the test. Approximately 500 g of feed constituted a charge. Pulp density of the feed was kept low to prevent particle to particle interference in separation. With feed in the range of 8x100 mesh, a pulp density of under 10% solids by weight was found advisable. With coarser feed the pulp density could be carried as high as 15% solids. Time of separation was very rapid. In the case of 4x20-mesh material, separation was effected in 15 to 30 sec; with -10-mesh feed, separation required about 1 to 2 min. SPECIAL EQUIPMENT Since heavy liquids are toxic to varying degrees, all separatory work was carried out in a standard laboratory fume hood. It was noted that complete removal of fumes was not being effected; therefore the hood construction was modified, resulting in a completely satisfactory arrangement for heavy liquid test work. In the interest of safety, details of this fume hood are reported here. Unlike most fumes, heavy liquid fumes tend to settle and flow like water, rather than to rise like a gas. Working on this assumption, a standard water drain was installed in the hood. Across the front of the hood a 1-in. barrier was constructed. In the rear of the hood a false back was installed, with an adjustable sliding door on both the bottom and top of this panel. As shown in Fig. 1, the exhaust fan pulled a vacuum behind the barrier, sucking the heavy fumes from the bottom of the hood. Another addition was the drying box, shown to the right of the hood. This is simply a box covered on top with hardware cloth and connected by a 6-in. inlet to the hood. Sample trays made of fine mesh wire filter screens were found ideal for drying samples. With this arrangement, air flowed completely through the sample and all fumes were drawn into the hood. In use, it was found effective to cover with a

Jan 1, 1963

Jan 1, 1920

By E. R. Borcherdt

IT is notable that the first large-scale mine operation equipped entirely with detachable bits was the Badger State mine of the Anaconda Copper Mining Co. in Butte, Montana, just 30 years ago. This mine in 1922 was producing approximately 1200 tons of ore per day. Much of the data presented in C. L. Berrien's article' describing the development and installation of the Hawkesworth detachable drill bit were obtained from these operations. As in any pioneering effort, no precedent existed and many difficult problems required solution, so that the changeover to detachable bits at all Butte hill mines was not completed for 6 years. There was widespread disbelief as to the probable efficiency of the new installation. Some attempts were made in 1931 by the owners of the Hawkesworth patents to interest Ontario gold mine operators in the bit. These efforts were not successful, but they undoubtedly stimulated thinking which resulted in the invention and patenting of several well-known Canadian detachable bits, one of which is now a widely used throwaway bit. The success of the Butte installation also led to the development of the threaded type of bit connections by several well-known manufacturers, and in 1935 these bits were introduced to the mining industry on a national scale. The original Hawkesworth bit was not provided with a water hole but, depended upon water passing through the clearance opening between the tongue in the bit and the groove in the rod to flush cuttings from the drill hole, see Fig. 1. In December 1935 it was found that this method of introducing drilling water to the bit face resulted in high dust counts. To correct this a water hole was drilled on the central axis of the bit, passing through the tongue. Unfortunately, quenching water would rise through the small water hole, spot-hardening the tongue to cause breakage, never completely eliminated. In the fall of 1936 large-scale tests indicated that savings would be effected by use of a threaded type of bit, which was therefore adopted as standard for all Butte mines. This type of bit was used until 1947, when it was superseded by a one-use slip-on type. Since the first use of the Hawkesworth bit every detachable bit of importance has been investigated, and where advantages which might reduce costs or increase efficiency were indicated, substantial tests of the bit were carried on in the Butte mines. When tests demonstrated the advisability of changing from one kind of detachable bit to another the change was made at one level or in one area each day until the new rod and bit equipment was used throughout the mine. This involved a minimum of cost and disruption of drilling. Intelligent selection of a detachable bit to obtain optimum results requires careful consideration to achieve a balance between the three principal types of equipment used in the drilling process: 1—drill bits, 2—drill steel, and 3—drilling machines. Optimum results imply maximum output and minimum cost per unit of output. Since every rock type differs in drillability and it is generally impractical to provide equipment for more than one or two types of rock which may occur in one operation, selection of equipment must encompass average drilling conditions. However, on exceptional occasions several widely differing conditions may make it mandatory to provide equipment best suited to each condition. The choice of rock-drilling equipment is a most controversial subject and one that is further complicated by unreliable and frequently misleading performance claims. Small operators without the means for making accurate evaluations of equipment frequently suffer from these over-enthusiastic claims. It is apparent from experience in rock drilling throughout the world that rock drillability is not alike in any two places, and that selection of proper equipment can only be made after conducting thorough trials of various types of equipment. Some recent drilling tests in tactite and hornstone at the Darwin, California mine of the Anaconda Co. present some interesting clues on rock drillability. Microscopic examination of thin sections of these rocks reveals that mineral composition and rock texture are equally important in governing drillability. The Darwin hornstone is at times so abrasive that the carbide bit cutting edges become flattened to 3/32 in. in 2 to 4 ft of drilling, and some carbide bits were dulled to this point after 9 to 10 in. of drilling. This wear was determined to be the proper point for resharpening to eliminate carbide insert breakage or breakage of the steel rod when drilling with 1½ to 1?-in. bits, with a drifter of 2 3/4-in. diam and 90 to 100 psi air pressure, see Supplement A. Before considering the merits of various bit designs it may be well to review the mechanics of drilling rock with percussion drills. A sharp bit cuts by penetration and chipping. The amount of penetration governs the amount of chipping and depends upon the contact area of the cutting edge, the foot-

Jan 1, 1954

[ ] Thomas C. Baker, Jr., has been transferred by the American Manganese Steel Div. of the American Brake Shoe Co., from their Oakland, Calif., branch to their Cleveland, Ohio, office. He will represent them in Ohio and Michigan. William H. Carson, has been appointed district manager of Goodman Mfg. Co's. Huntington, W. Va. sales office. He succeeds Morris W. Highland, granted a leave of absence for health reasons. Mr. Carson, a graduate engineer of Michigan College of Mining & Technology, has been a member of the company's Huntington sales force since 1939, the past two years as assistant district manager. James Parnell Caulfield, former general manager of the Utah Copper Div. of Kennecott Copper Corp., has been appointed assistant general manager of Kennecott's Western Mining Div. L. F. Pett, general supervisor of operations of the Utah Copper Div., was named Mr. Caulfield's successor as general manager. William D. Charles, on completion of his graduate studies at the Massachusetts Institute of Technology, accepted the position of mineral engineer with American Cyanamid Co.

Jan 1, 1952

By R. S. Wagner, R. G. Treuting, W. C. Ellis

Use of the Weisseizbevg goniometer for the study of the morphology of whisker crystals and transfer of the results to a stereograplzic projection are described. While in almost all instances a complete and rapid solution is obtained with a purely gaphical treatment, an absolute analytical treatment applicable to difficult cases is given. Examples are given for determination of growth direction and external features of a crystal, for detection of 'twintzittg, and for establislting the orientation relntionships in a kinked whisker crystal. We give here a method for the use of the Weissen-berg goniometerl" in the study of orientation relationships in "whisker" (micro) crystals3-8 and direct transference of the data to the stereographic projection. The operations are straightforward and require no involved calculations: in almost all cases solely graphical treatment is adequate. In a few complex instances, a more exact analytic method may be required. In the method, not only are equatorial reflections of an oscillation photograph used, but also those on higher layer lines, or those not occurring on a recognized layer line. Such reflections off the zero level are often essentialy to detect the presence of twinning. The method is particularly suitable for examination of whisker crystals since the axial or growth direction is almost always one of high symmetry, permitting a more restricted oscillation range to obtain the necessary reflections and an accordingly shorter exposure time. The method is also applicable when there is no lattice-related external symmetry, and is as well able to identify external crystal surfaces, when such exist, with the aid of an optical beam. Thus growth direction, identification of lateral faces, twinning, and orientation relationships in a kinked crystal can be established. A test for the Eshelby twist6-8 can readily be made. The method can be used for orientation, for structure analysis, and as an aid in the identification of an unknown crystal. Moving-film techniques have previously been employed variously for crystal-orientation studies.1,2,9-13 In particular, use of the Weissenberg method for orientation determination has been reported by Wooster and wooster.14 While their method derives the same data as here described, it differs in depending on the tracing of constant p streaks, a less than dependable phenomenon with small specimens, a few microns or less in cross section. The Laue method can and has been used for orientation studies of microcrystals,15 e.g., 2 p in cross section, but requires the extreme intensity and concentration from a microfocus tube to obtain reasonable exposure time. PRINCIPLES OF THE PRESENT METHOD Consider a crystal of random orientation with respect to the oscillation axis in a Weissenberg goniometer. Its diffraction pattern need not necessarily result in recognizable layer lines. In Fig. 1, a stereo-graphic projection of the reference sphere is given with the equatorial plane XZ normal to the oscillation axis Y, and the X-ray beam directed from X towards 2. The great circle ZZ is then normal to the beam, and the axes are right-handed. Thus the reflected X-ray beam lies at the intersection R of small circle ARB of radius 28 from 2, and of small circle RE of radius a from the rotation axis Y. a is the conventional semiapex angle of a cone of diffracted rays from the atoms aligned in the direction

Jan 1, 1967

By H. L. TERWILLIGER

THOSE of us who have been following rock drilling work for the last 15 or 20 years can recall some of the problems that were encountered with the old piston type of rock drill and the solid steel which it used. There was frequent trouble in keeping a straight hole in badly broken ground when using the ordinary four- point bit that had a flare on the wings of about 14". The drill steel, when pounding down its hole, would follow the line of least resistance and draw away from the desired line when it encountered a weak side in the ground through which it was drilling. Some would overcome the difficulty by making long winged bits to prevent the steel crowding over; this would relieve the troubles to a great extent. There was trouble with the rifling of drill holes and inability to drill round holes in some ground. The cure for these ills was to use the "X" bit, rather than the crossbit. The "2" bits were brought out in an effort to make it easier to drill a round hole in bad ground. Most of these troubles were before the days when the mechanical drill sharpener was in as common use as it is today. It was not until the introduction of the Leyner type of rock drill, requiring hollow steel that the users of rock drills found themselves confronted with more difficult prob- lems than they had ever encountered before with drill steel because the steel had to stand more severe service.

Jan 1, 1924

By W. N. Lacey, B. H. Sage

In recent years there has been an increase of interest in the flow of gases at relatively high pressures. Hydrodynamic calculation of the energy losses in the flow of gases in conduits, as well as through the porous solid materials constituting natural petroleum reservoirs, requires a knowledge of the viscosity of the fluid at the pressure and temperature involved. Although there are numerous publications concerning the absolute viscosity † of hydrocarbon gases at atmospheric pressure, there appears to be little information available relating to the effect of pressure upon the viscosity of these gases. Voge133 determined the viscosity of methane at 32° F. and atmospheric pressure. His measurements at 32° F. were later substantiated by the measurements of Rankine and Smith20 at 63° and 212° F. Ishida14 also reported values for the viscosity of methane at atmospheric pressure. Trautz and Kurz30 measured the viscosity of propane at atmospheric pressure, from 83° to 530°F., by the use of a short capillary tube. Rap-penecker2' determined the viscosity of gaseous isopentane at elevated temperatures. Day6 made an accurate investigation of the effect of pressure upon the viscosity of n-pentane and isopentane at pressures from 2 lb. per sq. in.‡ to the vapor pressure at 77° F. (approximately 9.8 and 13.3 lb. per sq. in., respectively). Earhart7 reported data upon the viscosity of several natural gases measured by the long capillary-tube method. The viscosity of air, at atmospheric pressure and 73.4° F., was measured by Harrington9 by the rotating-cylinder method. Kellstrom15 has rec,ently made an elaborate investigation of the viscosity of air at atmospheric pressure. The latter work is perhaps the most accurate investigation of the viscosity of a gas that has been made.

Jan 1, 1938

The first discovery of gold in Montana is credited to François Finlay, a half-breed, from the Red River country, in Canada; he went to California during the early days and learned there how to wash the gold from placer deposits; then, on his return, he crossed Montana and found gold on the western slope of the Rocky Mountains, on Gold creek, a minor tributary of the Hell Gate river, in what is now Deer Lodge county. That was in 1852.* Finlay did not find enough gold to induce him to continue at work, but six years later a group of miners, led by the brothers James Stuart and Granville Stuart prospected on this same creek, obtaining about ten cents to the pan. They, however, were harassed by the Blackfeet Indians, and they were also handicapped by lack of proper tools; so they too desisted from further operations. Two years later, in 1860, Henry Thomas started to work on Gold creek with three sluice-boxes hewn out of green timber that he cut on the spot. With this simple apparatus he won from $1.50 to $2.00 per day. This may be considered the fist instance of systematic mining in Montana. Meanwhile the Stuarts went to Fort Bridger, in southwestern Wyoming, where they remained as traders until 1861, when, again lured by the gleam of gold, they returned to the valley of the Deer Lodge and resumed prospecting, using 10 sluice-boxes that were brought from Walla Walla, in Washington, 425 miles distant. In the summer of 1862 they were joined by many others, chiefly from Colorado, in consequence of an exchange of

Jan 1, 1932

By J. P. Timmons, J. H. Moran, G. K. Miller, M. A. Coufleau

A prototype equipment has been designed and built for the digital recording of well logs on magnetic tape at the same time that the regular film recording is made. The format of the digital tape produced is such that it can be used directly at the input of the ZBM 704, 7090 or other models of ZBM computers which accept digital magnetic tape. This apparatus has been used for the experimental field recording of dipmeter tape logs which were subsequently computed by means of an ZBM 704 or 7090. In this paper the equipment and the digital tape are described briefly, and their application to the computer-interpretation of dipmeter data is discussed. A principal element in the interpretation of the dipmeter log is the correlation of the three microresirtivity dipmeter curves to determine the depth displacements between them. Several correlation methods for computer use are considered, with particular attention to their sensitivity to error and their consumption of computer time. The tape data were used to compute information content of the dipmeter microresistivity curves in terms of their frequency spectra. The results show that the sampling rate used in recording the digital information is quite adequate and illustrate a use of the digital tape in evaluating the characteristics of new tools. Some examples of field results are shown. It can be foreseen that, when digital tape recording becomes available for general field use, a whole new realm of possibilities will be opened up for the processing of other well logs through computations, which hitherto were not feasible because they were too laborious and time-con.sunzing. INTRODUCTION The last few years have seen a revolution in the design and production of data-processing equipment. Stored-pro-gram digital computers have progressed from a research curiosity to the basis of a major industry. There are now hundreds of such machines in daily use in the United States. With the acceptance of a technique that was, in fact, already clearly described by John von Neumann in 1945, the last decade has seen great strides in the development'of components, reliability, programming systems and, most spectacularly, in the sheer number of machines built and in use. In 1957 there were enough digital computers available to the oil industry to justify the suggestion that it would be worthwhile to investigate the possibility of using these machines in processing well log data.' The first result of this investigation was the appearance of what may be referred to as the input-output bottleneck. Well logs are customarily recorded on film. To get these data into a machine required then (and still does): a time-consuming semi-automatic reading of the film; conversion of the log data to digital form; and recording these digital data in some medium acceptable for computer input, such as cards, magnetic tape, or punched paper tape. However, the recording, reading, and re-recording could only result in deterioration of the data. Therefore, it was concluded that the fist step should be the development of a new, more direct recording technique supplemental to the film recording, which would provide easy access to the digital computer. There are many solutions to the problem of recording log data in an easily recoverable form. After careful consideration it was decided to adopt the boldest solution which, it was felt, was also the most elegant. It was decided to record well logs directly, in the field, on magnetic tape in such a way that this tape could be used without further modification as an input to the IBM 704 or 7090 computer. To realize practical field recording of magnetic tape logs, it became necessary to develop in a rather small package, an analog-to-digital converter, a tape recorder, and the necessary multiplexing and control circuits to allow the simultaneous recording of a multiplicity of logging signals. The magnetic tape recording was to be made simultaneously with the conventional logging operation in such a way as not to interfere with it. Along with the development of hardware, it was necessary to begin development of interpretation techniques and machine programs that would exploit the power of the digital computer. Here, again, there is a long list of possible applications. After much consideration it was decided to concentrate on the interpretation of the dipmeter log as a first application. It is the object of this paper to describe in some detail the developments sketched in the last three paragraphs.