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By B. Haimson, C. Fairhurst

One of the main functions of rock mechanics research has been to find ways of determining in-situ stresses. Many methods have been suggested, the most significant ones calling for measurements inside bore- holes. These methods usually employ some instrumentation for the purpose of measuring hole deformation. Several years ago, a new method was suggested by Scheidegger,l based on previous work by Hubbert and Willis.2 It was the method of "hydraulic fracturing," which had been introduced by the oil industry in 1948 for the purpose of oil-well production stimulation. Basically, hydraulic fracturing consists of sealing off a section of a borehole, pumping in a fluid, and pressurizing it until fracture occurs. If pumping is continued vigorously, the fracture is opened up and extended. In an oil field, such an artificial fracture increases the overall permeability of the formation and usually enhances production. During the entire operation, the variation of pressure with time is ordinarily recorded. Hubbert,2 Scheidegger,1 Kehle,3 and others have shown that the recorded pressures can be theoretically related to the magnitudes of the principal in-situ stresses; the orientation of the fracture can often be used to determine the direction of the principal stresses. The advantage of hydraulic fracturing over the present in-situ stress determination methods is simplicity: no sophisticated instrumentation is required inside the borehole; hence, the stresses can be measured at any depth. Moreover, if the formation is impermeable to the fracturing fluid, no elastic constants of the rock are required in calculating the stresses, a

Jan 1, 1970

By Arnold Hague

At the Buffalo meeting, October, 1888, Dr. Raymond presented a paper entitled: "Soaping Geysers" (p. 449 of the present volume), in which he called attention to the use of soap by tourists to cause eruptions of several of the well-known geysers in the Yellowstone Park. Incorporated in this paper appears a communication received from me, written from camp in the Park, in reply to some inquiries on the subject. The letter discussed somewhat briefly the means employed by visitors to the Park to hasten the eruptions from hot springs and reservoirs of hot water, which remain dormant for days, or even weeks or months, at a temperature near the boiling-point, without any display of geyser-action. As the paper has called forth considerable comment, I desire to elucidate one or two points in relation to the temperature of the springs, and to answer some inquiries about the composition of the thermal waters. In the summer of 1885, a Chinaman, employed as a laundryman for the accommodation of the tourists at the Upper Geyser Basin, accidently discovered, much to bis amazement, that soap thrown into the spring from which he was accustomed to draw his supply of water produced an eruption in every way similar to the actual workings of a geyser. Tourists with limited time at their command, who had travelled thousands of miles to look upon the wonders of the Yellowstone, soon fell into the way of coaxing the laundryman's spring into action, to partly compensate them for their sore disappointment in witnessing only the periodical eruptions of Old Faithful. Successful attempts upon this spring soon led to various endeavors to accelerate action in the dormant and more famous geysers. In a short time, so popular became the desire to stimulate geysers in this way, that the Park authorities were compelled to enforce rigidly the rule against throwing objects of any kind into the springs. In connection with a thorough investigation of the thermal waters of the Yellowstone Park and the phenomena of the geysers, I undertook a number of experiments to ascertain the action of soap upon the waters and to determine, if possible, those physical conditions of various pools and reservoirs which permitted the hastening of an

Jan 1, 1889

A BLAST can be "full of sound and fury," signifying nothing but a poorly confined charge, or it can be a muffled, well controlled explosion which moves the rock efficiently and places it in the desired location with the least amount of fuss and bother. Why one method will do the job and another proves to be almost useless is shown by the machine-gun camera studies of quarry blasting made by the Atlas Powder Co. staff. The sequence, or machine-gun, camera is the latest scientific device for the study of cause and effect factors in blasting. Movie cameras, previously used, although of some use, were limited because slow shutter speeds and small negatives failed to give clear, sharp prints. During World War II, the AAF developed the sequence camera, which figuratively stops the blast at regular intervals, making study and evaluation feasible. The camera is simple and inexpensive and offers material for accurate examination of blasting techniques. The machine-gun camera takes three 5x5 in. exposures per sec at a 1/450 sec shutter speed, four times faster than a movie camera. Negatives are 30 times larger than those of movie cameras, giving large, sharp prints. The rock movement is frozen on the picture as the sequence of the blast takes place. Pictures on this page show the advantage of individual machine gun photographs. But the sequences made possible by this camera give graphic, dramatic and conclusive support to recently developed detonation theories.

Jan 1, 1952

By R. A. David, D. J. Vink, D. L. Katz

A phase diagram showing boundary curve and quantity of liquid in the two-phase region was determined for a mixture of natural gas and natural gasoline in the region of its critical conditions. The temperatures and pressures of phase measurements were in the range of 85 to 212 F. and 1300 to 2600 Ib. per sq. in., respectively, with the critical conditions at 169.5 F. and 2615 Ib. per sq. in. abs. Color phenomena were observed in the region of the boundary curve from 102' to 192 F. Approximate densities of the single-phase and two-phase regions and analysis of the system are included. Boundary curves between the single-phase and the two-phase regions have been determined for several binary mixtures containing hydrocarbons. 2,3,4.6,7,10,11,12,14 These investigators did not report the relative amounts of liquid and vapor within the two-phase region. The equilibrium values obtained from the dew-point and bubble-point data can be used to compute the lines showing percentage of liquid on the pressure-temperature phase diagram8 but the positions of the lines near the critical temperature and pressure are uncertain. Relative amounts of vapor and liquid were obtained for a gasoline and a naphtha1 within the two-phase area but not in the region of the critical temperature and pressure. The bubble-point and dew-point lines, as well as the percentage liquid lines within the two-phase region, were determined by visual observations in glass apparatus. Apparatus An arrangement of the apparatus is given in Fig. 1, showing the Jerguson gauge A with glass windows B. Pressure was supplied by the

Jan 1, 1940

By Charles H. Doolittle, Royal P. Jarvis

The following notes are contributed, not with the idea of offering a complete history of the development of this very important process as applied to the Leadville district, but with the hope that the practice, as it was carried out in the Bi-Metallic Smelter, may still be of interest to others. The Bi-Metallic Smelter, at Leadville, Colo., was the first to make a commercial success of the process described in the following pages, which consisted essentially of smelting raw silver- and copper-bearing sulphide ores in blast-furnaces to form a matte, which was generally re-smelted with siliceous ores for a second high-grade matte. Robert Sticht, in his excellent monograph on the subject,' has outlined briefly the plant belonging to this company. He says, in effect: The Boulder, Mont., enterprise set the example for others with whom the patentee (W. L. Austin) had been negotiating, and the old La Plata lead-smelter at Leadville, Colo., was fashioned into a crude, temporary experimental plant for the Bi-Metallic Company, and the feasibility of the process demonstrated by a trial run. Subsequently, the plant was considerably improved, and, being supplied with very favorable ores, continued to run without interruption from August, 1892, to June, 1893. In September, 1803, smelting was resumed in a completely remodeled establishment, some $200,000 having been expended upon the new work. Thus, aside from the Montana experiments, which, under the direction of W. L. Austin, began as early as 1885 at Toston, and continued with indifferent success for six or seven years, the Bi-Metallic plant at Leadville may be said to have

Jan 1, 1911

REJUVENATED is an apt word to apply to Chino, Kennecott's big open-pit mine at Santa Rita, New Mexico. Back in 1923 Chino was merged with Ray by an exchange of shares, and in 1926 the Ray-Chino combination was taken over by Nevada Consolidated through an issue of bonds that were traded for the Ray and Chino assets. Subsequently, of course, the whole package was acquired by the Kennecott Copper Corporation. On the basis of the terms of the Ray-Chino-Nevada exchanges, Chino was rated third in value, something less than thirty per cent of the total. In 1955 the appraisal would doubtless be forty per cent or more. But it is not only vis-a-vis Ray and Nevada that Chino has blossomed out. At the end of 1931, Chino ranked seventh among the Porphyries in point of output; whereas by the end of 1954 it was fifth,. having passed both Inspiration and Nevada Consolidated. Sharp curtailment in production in 1932-33-34 and total suspension in the two years following (see Fig. 21) found the property in a somewhat parlous position. However, the engineers had not been idle; they had been planning for the future, and in 1937 a far-reaching program of rejuvenation was launched. During the ensuing five years, capital expenditures totaled more than $8,500,000. Among the projects undertaken were the following: (1) Mine-Purchase of larger and better equipment for drilling, loading, and transporting the ore. (2) Mine-Beginning of the first systematic project to leach and recover copper in the waste dumps at the mine.

Jan 1, 1957

By P. H. Fahlström

The Ebliden Company, originally entering the field of mining with the workings of the gold-copper-arsenic deposit at Ebliden, commenced zinc benificiation at Kristineberg in 1940 and lead mining at Laisvall in 1943. During the three last decades a number of mines has been developed for production, Today the Mining Division of BOLIDEN produces ore from 22 mines, operates 7 ore dressing plants and produces: [ ] Over two thirds of the lead contents are treated in the lead smelter of the company at Ri6nnskarsverken. The other part of it is sold abroad. The zinc content of the lead concentrates is recovered from the lead smelter at Ri6nnskarsverken. The zinc concentrates are shipped abroad to European smelters in Norway and Germany. Today BOLIDEN has its plants in the northern and the middle parts of Sweden. Figure 1. Straight lead ore, lead-zinc ores, lead-zinc-copper bearing ores and complex lead-zinc-copper and pyrite ores are treated in local and central plants with a capacity of 8.600 tpd. BOLIDEN also operates the low grade copper ore at Aitik at 7.000 tpd.

Jan 1, 1970

By Edwin C. Eckel

The title of this study may fairly lead to misunderstanding unless its basal viewpoint is explained at the start. There is of course no chance of misunderstanding the term strategic minerals-for some years past it has been rather generally used to cover those mineral supplies, important for war use, which do not occur in adequate amount on the territory of the Power under consideration. Even here, however, I might add a note of warning. It is commonly understood that the list of strategic minerals will vary, according to what country we are considering; but it is rarely understood, even in Staff studies, that it varies equally according to the particular adversary we happen to be considering. In the present study I have stated the definition in the broadest possible terms, and have at this stage purposely avoided limiting it to any one country or war situation, with the express purpose of being free to bring out certain implications which are commonly, if not always, overlooked. The more important opportunity for misunderstanding is, of course, that my views on the phenomena war and peace do not coincide with those currently fashionable, particularly in advanced intellectual circles. For we must face the fact that for a decade past the natural reaction from war conditions has shattered the public mentality so completely that our public discussions of such questions have very little relation to fact; they are excursions into ideal rather than Realpolitik. And as such they serve merely to prevent public discussion or accept-

Jan 1, 1932

By R. A. David, D. L. Katz, D. J. Vink

A phase diagram showing boundary curve and quantity of liquid in the two-phase region was determined for a mixture of natural gas and natural gasoline in the region of its critical conditions. The temperatures and pressures of phase measurements were in the range of 85 to 212 F. and 1300 to 2600 Ib. per sq. in., respectively, with the critical conditions at 169.5 F. and 2615 Ib. per sq. in. abs. Color phenomena were observed in the region of the boundary curve from 102' to 192 F. Approximate densities of the single-phase and two-phase regions and analysis of the system are included. Boundary curves between the single-phase and the two-phase regions have been determined for several binary mixtures containing hydrocarbons. 2,3,4.6,7,10,11,12,14 These investigators did not report the relative amounts of liquid and vapor within the two-phase region. The equilibrium values obtained from the dew-point and bubble-point data can be used to compute the lines showing percentage of liquid on the pressure-temperature phase diagram8 but the positions of the lines near the critical temperature and pressure are uncertain. Relative amounts of vapor and liquid were obtained for a gasoline and a naphtha1 within the two-phase area but not in the region of the critical temperature and pressure. The bubble-point and dew-point lines, as well as the percentage liquid lines within the two-phase region, were determined by visual observations in glass apparatus. Apparatus An arrangement of the apparatus is given in Fig. 1, showing the Jerguson gauge A with glass windows B. Pressure was supplied by the

Jan 1, 1940

By I. N. Zavarine

The observations presented in this paper were recorded during a study of the spheroidizing process. Spheroidization of cementite in steel is either brought about to develop a set of desirable mechanical properties or is an incidental result of mechanical and heat-treating manipulations. Physical properties of steel are materially influenced by the state of the cementite. Conversion of cementite from the lamellar to the spheroidal state is usually accompanied by a decrease of hardness and of strength and by an increase in ductility. The spheroidized structure is usually considered as an ultimate step in the process of the softening of steel. The unorthodox hardening of a 3.5 per cent Ni steel (SAE No. 2330) after a heat-treatment that previously proved entirely suitable for a complete spheroidization of cementite in carbon steels led to the observations that constitute the subject of the present paper. Experimental Procedure The steels used for the experiments described were bought on the market. All were in the form of 3/4-in. round bars. Their chemical compositions are given in Table 1. The spheroidization of cementite in steels can be obtained in several ways. The method used in the present work is, perhaps, the least known. It consists of cyclic heating and cooling of steel, the temperature being

Jan 1, 1939

By Paul M. Tyler

Fully a decade ago, demand for ground mica began to exceed supplies of scrap mica from manufacturing operations and of waste block from feldspar and sheet mica mining in the United States, with the result that in recent years the market has absorbed larger and larger quantities of mica recovered as a by-product from clay washing,1 as a joint product with kyanite12 and by grinding schists. So far, only schists that contain a large percentage of mica have been utilized for making ground mica, but already there has been a good deal of wishful thinking with regard to recovering mica as an aid to the prospective working of low-grade gold ores and ores of certain base metals. With wet-ground mica selling at $60 to $100 a ton and even dry-ground mica worth over $20 a ton, many ores that could not be considered as otherwise workable under present conditions will show commercial possibilities if they can be made to yield even a relatively small percentage of salable mica. An interesting paper might be written on the coming role of industrial minerals as joint products of metal mines. It is largely a matter of markets. Many years ago I watched the mess left behind the gold dredges in the mountains of Colorado and thought of the Denver sand and gravel operators who prided themselves upon their canniness in providing devices for catching gold merely as an incident to their regular business of selling what we miners classed as "tailings." Nowadays almost every milling or mining operation near settled communities finds use for at least part of its waste for road material or concrete aggregate and several eastern iron mines have gone into the crushed-stone business. Promoters now mention fertilizer "filler" as potentially salable at all the way from $1 to $10 a ton, or whatever is needed to cover costs of mining and treating the "ore" and leave the metal values as "clear profit." In emulating the pork packers in their efforts to utilize "everything but the squeal," mining engineers may go too far; on the other hand, they should not let

Jan 1, 1942

By Peter B. Scotland

The mines of the Arizona Copper Co. are situated in the Morenci-Metcalf copper district in southeastern Arizona. This copper-bearing district covers a triangular mountainous area of about 3 square miles, rising abruptly from the gravel plateau of the surrounding country. In this area, an immense intrusion of porphyry lias displaced, shattered, and engulfed the shales, limestones, and quartzites formerly bedded on the basal granite. Outcrops of oxide ore were discovered in 1873, and these surface ores were found to connect in depth with large bodies of high-grade oxide ores in the limestones and shales. The mining of these high-grade ores continued until about 1893, when their rapid exhaustion led to the discovery and exploitation of the low-grade sulphide ores in the adjoining porphyry. Methods of concentration were then devised and the low-grade ores finally rendered profitable. The Arizona Copper Co. and the Detroit Copper Mining Co., operating in the same district, were the pioneers in the successful development of the low-grade "porphyry" properties of to-day. The largest mines of the Arizona Copper Co. are the Humboldt and Clay at Morenci, and the Coronado, Metcalf, and King at Metcalf. These mines produce about 4,000 tons daily of concentrating ore containing from 2.5 to 2.8 per cent. copper. The topography of the country is very rugged and mining operations are conducted principally through adit levels. A few of the mines are opened by shafts, the deepest being 1,100 ft., in the Coronado mine. Ore Occurrence The low-grade sulphide ore occurs as: (1) disseminated deposits in the main stock of quartz porphyry; (2) lode deposits in fault fissures in granite. The high-grade oxide ores were found as tabular deposits in limestone and shale close to contacts with porphyry dikes. Low-grade oxide ore formed the outcrop of some of the sulphide orebodies; the majority of the outcrops, however, were barren.

Jan 1, 1915

By I. N. Zavarine

The observations presented in this paper were recorded during a study of the spheroidizing process. Spheroidization of cementite in steel is either brought about to develop a set of desirable mechanical properties or is an incidental result of mechanical and heat-treating manipulations. Physical properties of steel are materially influenced by the state of the cementite. Conversion of cementite from the lamellar to the spheroidal state is usually accompanied by a decrease of hardness and of strength and by an increase in ductility. The spheroidized structure is usually considered as an ultimate step in the process of the softening of steel. The unorthodox hardening of a 3.5 per cent Ni steel (SAE No. 2330) after a heat-treatment that previously proved entirely suitable for a complete spheroidization of cementite in carbon steels led to the observations that constitute the subject of the present paper. Experimental Procedure The steels used for the experiments described were bought on the market. All were in the form of 3/4-in. round bars. Their chemical compositions are given in Table 1. The spheroidization of cementite in steels can be obtained in several ways. The method used in the present work is, perhaps, the least known. It consists of cyclic heating and cooling of steel, the temperature being

Jan 1, 1939

By L. H. Duschak

Electrolytic zinc produced from sulfate solution and with pure lead anodes is always contaminated with a small and varying percentage of lead. The purpose of this investigation is to determine the characteristics of several lead alloys and their influence on the products of electrolysis and power consumption. The study of alloyed anodes has been a matter of interest for some years. Tainton, Taylor and Ehrlinger prepared a highly interesting paper' on this subject a year ago, in which the effects of silver-lead and some ternary alloys of lead-silver-tin were described, and the presentation of any paper on insoluble anodes will owe much to the inspirational results achieved by Dr. Colin G. Fink and Li Chi Pan in their work on insoluble anodes for the electrolysis of brine,2 and to other published papers by Dr. Fink and his coworkers embracing the development of the copper-silicon-manganese anode for the production of electrolytic copper and the general subject of anode development. The present paper describes a study of various combinations of 10 metals. The general plan of the work provides for the fabrication of the alloyed anode, its adequate conditioning by preparatory electrolytic operation, the production of cathode zinc and its analysis, the determination of the anode polarization, and other features. A list of the anodes tested, showing composition and polarization at various current densities together with the lead assay of the cathode zinc, is shown in Table 1. Determination of Anode Polarization In the determination of anode polarization under operating conditions it is essential that the anode area used be restricted to the side facing the cathode, in order that these measurements may be referred to a definite current per unit of area. It becomes necessary, therefore, to insulate the inactive face of the anode, to prevent the leakage of lines of force

Jan 1, 1930

By John R. Edwards

Introductory.—There are many interesting and important events connected with the petroleum problem. The remarkable men who conceived 'the thought of transporting petroleum by pipe line, conserving the byproducts of the commodity, and conducting extended investigation and research whereby the flash point of the oil was raised, its cost reduced and its supply assured, are deserving of the gratitude of this nation. It was primarily the success attained by Captain Lucas, after his comprehensive search for oil in Texas and Louisiana, that was the impelling cause which prompted the Navy Department to conduct the extensive series of liquid fuel-oil tests that were made from 1901 to 1903. The sensational discovery of oil at Spindle top made a deep impression upon Rear Admiral George W. Melville, then Engineer-in-Chief of the Navy, and the discovery of the vast oil field in Texas convinced him that, within a generation, if not within a decade, crude petroleum was going to play a very important part in warfare, and that the commodity might possibly develop into a necessary munition of war. The United States' Commanding Position as a Petroleum Producer.— In the study of the various problems relating to the world's production of crude petroleum, the position of the United States is one of commanding importance, whether viewed from the industrial or the military aspect. The present yield of this country is practically double that of the rest of the world, and, in view of the productive and prospective fields possessed by various countries, together with the comprehensive and exhaustive search that has been made throughout the world for petroleum, it is extremely probable that this lead will be maintained for the next decade. As regards the character of the crude-oil yield of different countries, America possesses the greater part of the supply that contains a paraffine base, and therefore a considerable portion at least of the American product produces the best illuminant. Of all the crude-oil distillates, kerosene is in many respects thc most important, and the Appalachian product for this purpose is favored, particularly in the Far East, above that of any other petroleum yield of the world.

Jan 1, 1915

By W. H. Adams

Virginia, a store-house of metals, is more and more a surprise to the present generation. With her enormous available mineral wealth, worked upon steadily for over a century, exploited SUEciently to demonstrate beyond question costs and values, reported upon by our most eminent scientists, written up by thoroughly earnest correspondents, we yet find her little understood by capitalists or practical men, and until very lately overlooked by the advanceguard of pioneers in metallurgy, whose restless energy conquered the wilderness of Northern Michigan years ago, and has written a new and startling history for almost impenetrable Western territories. The world is learning through the mouths of giant furnaces lately put in blast at Lowmoor, Goshen, and Roanoke, more of this wondcrful State. It is becoming plain that nearer home, amid all the surroundings of civilization, under an equable climate and with the advantage of a minimum cost for fuel and labor, there are stores of mineral, varied in character and deposited over a wide area, which exceed all ordinary calcnlations. Principal among these minerals, iron ores have been, and will probably continue to be, the leading product and the source of greatest revenue. My attention has been called during the past year to one particular section of the iron-belt, where for forty years charcoal-furnaces were successfully operated, the ores being mined in open pits, as can so frequently be seen from the Connecticut line southward into Georgia. There is, however, a significant peculiarity in the character of these deposits of Louisa county warranting special mention, as it is thought that nowhere on the earth's surface, within so moderate a distance of tidewater, can their like be fouad. Probably half a million tons of lump and wash-material have been taken from pits

Jan 1, 1884

By Edward Thomas

ROCK bolting, third great change in postwar underground mining, is inseparably tied to the other two changes: better drilling and mechanized mining. Mechanized mining provided the impetus, when conventional supports restricted maneuver-ability of equipment-while carbide-tipped bits lent the means of drilling required holes cheaply. With the need and the tools at hand development snow- balled. In just six years, from January 1948 to January 1954, some 800 mines adopted bolting for systematic support, and over 100 of these mines now use rock bolts exclusively. Simultaneously, foreign mines have adopted the idea, but to a lesser extent. What held back this major change? The concept of fastening loose material to unbroken and apparently solid material is probably as old as mining itself, and sporadic use has been reported from virtually every mining region in the world. But falls of rock have always been the greatest source of both fatal and nonfatal accidents in underground mining and miners have understandable reluctance to work under roof or back material if they even suspect that it might be hanging like a "sword of Damocles" -supported only by a thin bolt.

Jan 11, 1954

By Schlumberger, C

IN the search for practical geological problems amenable to solution by the potential methods, the geophysicist is led to study mathematically various theoretical cases. In these idealistic discussions, the media under consideration are generally supposed to be homogeneous and iso-tropic. The geophysicist, of course, realizes perfectly that these condi-tions do not occur in their entirety in reality. However, the assumptions made are justified, because very often they are necessary in order to render possible an exhaustive study of a given problem, which otherwise would be too complicated, and would not lend itself to a complete mathe-matical analysis. Of the above two assumptions, that concerning the homogeneity of a given geological formation is satisfactorily realized except in so far as isotropy is concerned, since this property is not often encountered in practice. As a consequence, it is very desirable for the geophysicist to have quite an extensive knowledge of the properties of anisotropic forma-tions, and of the laws that govern the propagation of electric current therein. With such principles in mind, he will be able to decide whether the conclusions arrived at in simple, isotropic conditions are still correct in more complex cases, or in what way they must be modified or adapted in order to constitute a sound basis for the interpretation of the results obtained in anisotropic media. On the other hand, the fact that in anisotropic formations themobility of the ions is greater along the strike than perpendicular thereto can be utilized for determining the direction of the dip by induc-tion measurements. We therefore propose to study in three successive chapters the following points: 1. Propagation of the electric current in anisotropic media. 2. Some consequences of the anisotropy of geological formations with reference to the surface electrical measurements, and their interpretation. 3. Determination of the direction of the dip of anisotropic formations by surface induction measurements.

Jan 1, 1933

By E. P. Pfleider, O. Rellensmann

For many years mine surveyors and exploration engineers have sought an accurate means of transferring meridian underground by using the gyro-compass. These efforts have generally failed, either because they were inaccurate or because the size and cost of the unit were prohibitive. During the past ten years, however, great strides have been made. Autonetics in California has developed a comparatively light-weight (100-lb) gyro-theodolite, and the Institute for Mine Surveying at Clausthal Mining Academy in Germany has developed an instrument that is accurate to within 20" to 30" of arc. Concurrently, Minneapolis-Honeywell has produced an astounding gyro, the size of a salt shaker, that weighs less than 0.5 lb and compares favorably in performance with the 50-lb gyros of conventional design. This unit, designed for missile guidance, should be adaptable for surveying small boreholes. Given the proper interest and approach from the engineering fraternity, excellent gyrocompasses could probably be available for accurate underground survey work at nominal cost within the next three years. Principles of the Gyro-Compass: The gyrocompass, used for 50 years as a navigational instrument in ships and aircraft, senses the turning axis of the earth and points out true polar north. It does this by employing the earth's rotation, the force of gravity, and the precession characteristics of a gyro. For further details the reader is referred to several excellent publications'"3 covering the principles and application of the gyroscope. The heart of the gyro-compass is the gyroscope, or rapidly spinning wheel, which rigidly maintains its angular orientation in inertial space. Free gyros employ universal joints to allow the wheel axle to maintain its rigid spatial orientation independent of base motion disturbances. Free gyros are independent of the earth's turning and are not north-seeking. Only as they might be initially oriented parallel to the earth's turning axis could any north indication be obtained. In practice, the free gyro tends to drift off its set position and lose its accuracy. The Sperry-Sun Well Surveying Co. instrument (5M in O. D.) is of this free gyro type. It is counterbalanced, however, against the rotational effects of the earth, so that orientation of the spinning axis will be maintained throughout the survey.

Jan 1, 1960

By Clinton M. Ball

Magnetic iron-ore is found in many localities throughout this and other countries, in large bodies and in convenient proximity to other materials required for its conversion into iron and steel; and these bodies of ore would have great commercial value on account of their nearness to consuming markets if they were generally suitable in their natural state for use in the larger operations of steel-making. In the manufacture of iron and steel it has been found, however, that not all ores are equally valuable as sources of raw material for the finished products of furnace, forge and foundry; and, as is now well understood, this is because of the intrusion, in the process of formation of the ore-bodies, of substances which can enter into deleterious combinations with the iron itself, or form compounds associated with the iron oxide which will hinder, if they do not altogether prevent, the production therefrom of the higher grades of finished metal. It is only since the development of the modern method of steel-making by the Bessemer process that the art of the chemist has been called to a critical study of the nature and effect produced by the presence of these pernicious substances in the furnace while the iron is undergoing reduction to the metallic state. Phosphorus and sulphur are the most common and obnoxious elements, and the admixture of one or the other, or both of these, in small percentages and varying proportions, will greatly modify the final results of manufacture. It so happens that generally, although not always, these hurtful elements are found in compounds in the ore which are not magnetic, and this circumstance has led to the expenditure of much ingenuity and money over a long period of time, in attempts to utilize the attractive power of magnets to separate the magnetic oxide of iron out of its crushed ores and from sands, in

Jan 1, 1896