Search Documents

By C. BARING HORIVOOD

(Chattanooga Meeting, October, 1908.) THIS paper is intended, in the light of recent investigations, to call attention to some of the essential features of good practice in sampling and mine-valuation. Mine-sampling may be divided broadly into two classes : (1) development-sampling and computation of ore-reserves; and, (2) stope-sampling and estimation of stope-values. DEVELOPMENT-SAMPLING. It is with development-sampling only that this paper deals-the term development being taken to mean the opening-up of a mine by cross-cuts, drives, connections, etc., preparatory to actual extraction of the ore for milling. In development-sampling the work of the sampler and the consequent estimation of the probable value of the mine or portions of the mine, as the case may be, cannot be verified until a later period, when the ground thus sampled has been exploited; hence, extreme care and accuracy are essential. Moreover, the development-sampler has to foresee and allow for contingencies which may arise when stoping is started. It follows that the sampling, in development-work, demands familiarity with the conditions likely to be encountered later in actual mining. In stopes, on the other hand, sampling is clone under actual working-conditions, and the sampler's valuations are immediately checked by the gold-output, or in some cases by a second sampling of the broken ore. A stope-sampler therefore need not be an experienced miner, though he should possess sound technical training and work accurately. Should he be somewhat inexperienced, be soon has his errors discovered for him, and learns to avoid them. Taking these facts into account, it is obvious that a mining company employing two or more samplers should

Jan 1, 1909

By K. J. Rosengren

INTRODUCTION Mount Isa Mines Limited operates a major mining complex at Mount Isa in northwest Queensland, Australia. The location is arid and remote, some 600 miles distant from the nearest port of Townsville on the eastern coast (Fig. I). Current mine production is 6 million long tons per annum comprising 3.8 million tons of copper ore and 2.2 million tons of silver-lead-zinc ore. Copper ore production is scheduled to increase to 5.8 million long tons per annum by 1973 and a new silver-lead-zinc mine is being developed at Hilton, 13 miles north of Mount Isa. The Mount Isa and Hilton orebodies occur in a single stratigraphic member, termed the Urquhart Shale. This shale is conformable with several other sedimentary formations striking north-south and dipping approximately 65º west. The silver-lead-zinc orebodies occur in bands conformable with the shale bedding and tend to be of tabular shape, varying in width from a few feet to nearly 200 ft. The copper orebodies occur in breccia bodies, locally known as "silica-dolomite", within the Urquhart Shale and tend to be more irregular and massive with widths up to several hundred feet. The detailed geology is described by Bennett (1 2). At present, production comes almost entirely from underground operations with only about 25,000 tons per year of carbonate ore from open pit operations. The mining method used in the copper orebodies is sublevel open stoping with pillar recovery by pillar blast before stope filling or by sublevel caving after stope filling. A large primary sublevel caving operation was also carried out until recently in one of the orebodies. The wider lead orebodies are mined by sublevel open stoping, with or without pillar recovery, while cut and fill stoping is used in the narrower orebodies. Details of the mining methods are given by Davies (3). The company's interest in open pit mining stems from a large open pit which was mined out in 1965 and a further large open pit planned for future production. In addition, the company is currently evaluating several large ore deposits in Australia and New Guinea. All of these orebodies would be mined by open pit methods and rock mechanics studies of slope stability are now a standard feature of all open pit evaluations.

Jan 1, 1972

By A. L. Hay

The Sydney coal field, the largest and most valuable in Nova Scotia, is situated on the northeastern coast of the Island of Cape Breton, extending from Mira Bay on the south to Cape Dauphin on the north, a distance of 30 miles, and has a general dip northeast under the sea. (Fig. 1. The field embraces the mining villages of Morien, Birchgrove and Reserve and the towns of Dominion, Glace Bay, Waterford and Sydney Mines. The city of Sydney is situated about midway between the northern and southern extremities of the field and on the western fringe of the productive coal measures. Sydney harbor crosses the coal field, cutting off direct rail connection between Sydney Mines and the greater part of the field to the southeast. (Fig. 2.) The coal measures are exposed in the cliffs on the coast line, which rise to an average height of 30 ft., and are almost continuous throughout the length of the field. The portion of the coal field under land forms a small segment of a circle, the greatest distance from the coast landwards is 9 miles, and it occupies an area of 200 sq. miles. The greatest distance developed seawards from the shore by mining operations is 2 miles. The strata maintain a regularity of dip at this distance, proving a submarine area of about 70 sq, miles. How much further the coal field extends seawards is unknown, but the indications are that it extends far beyond the present economical working limit and in all probability there is a vast submarine coal field. The productive coal measures are of Carboniferous age, these being underlain by beds of sandstone, locally classed as millstone grit, which define the southern limit of the field, while a spur of syenitic hills cuts off the coal-bearing strata on the north. Two main anticlinal folds having a general course easterly divide the field into three basins named from north to south: Sydney Mines-Lingan, Glace Bay and Morien. So far as the portion of the coal field already developed is concerned the general effect of these folds is to vary the direction and dip of the strata at different points of the several basins. The strata dip seawards at the average rate of 6 per cent. along the axes of the basins. On both sides of the several basins, the strata have a dip varying from 7 to 40

Jan 1, 1930

By AIME AIME

WHEN H. I. Smith joined the Institute back in 1908, he was an instructor in mining and metallurgy at Penn State the college from which he had graduated the year before with a B.S. degree. He had not gone far afield for his education, for he was born, February 15, 1984 at Finleyville, Pa., a small village some fourteen miles south of Pittsburgh and without doubt famous chiefly as H. I.'s birthplace. The summer that he graduated he took a trip to the copper mines Arizona and Mexico and en route worked for four weeks for the Portland Gold Mining Co. at Cripple Creek, Colo., as a mucker and trammer. The next summer he roamed farther afield mines and metallurgical works in Europe. Wishing to see more of Arizona, he left the Penn State faculty early in 1909 and went out to Wenden in that State to become mining engineer and assistant superintendent of something called the Corona Copper Co., with 72 mining claims and a one-mule-powered whim for a hoist. When that job folded he helped build the Santa Fe railroad from Parker. Ariza., to Danby Cialif., and then came back to Pennsylvania to enter Government services as a junior mining engineer with the Bureau of Mines.

Jan 1, 1943

By W. E. Remmers

The fact that gray iron increases in volume, cracks and distorts upon repeated heating and cooling is rather conlmon knowledge. In ingot molds, Diesel engine pistons, carburizing boxes, continuous furnace parts, grate bars, stoker parts, and all castings that are subjected repeatedly to high and low temperatures, the phenomenon of growth presents a vital problem. Ingot molds distort and produce cracks which result in seams or laps and later appear as defects in the finished product. The heads of Diesel pistons frequently fail by cracking in a stellar shape. This is attributed usually to the result of permanent growth. Distortion and change of dimension of furnace parts frequently renders them entirely unusable. In chain grate stokers, mechanical difficulties frequently are caused by the growth of the links. In proper operation these links should never attain a temperature sufficiently high to start growth; nevertheless, some have grown in. on an 8-in. length when improperly operated. Even though the phenomenon is generally known there still exists a deficiency in the explanation of the mechanism of this growth. The field of investigators of this subject has a decided variation in opinion concerning the causes. The problem is of sufficient importance therefore to warrant further consideration. Review of Published Work Since the published work, particularly the European, contains much detail, only the outstanding results and conclusions of the investigators will be reviewed. The pioneering investigations of Outerbridge in 1904 and 1905 brought forth the conclusion that growth was not a function of chemical or crystallographic changes but was a result of the formation of fine hair cracks. These cracks are supposedly due to a nonuniformity of thermal expansion and contraction which ruptures the structure of the material. More recently Benedicks and Lofquist presented a purely mechanical theory, which is similar to that of Outerbridge. These investigators believe the temperature gradient from the outside to the center of the cast piece causes a contraction of the outer layers on passing

Jan 1, 1931

By R. B. Woodworth

INTRODUCTION IN the sinking of bore holes, there are but two fundamental operations -drilling and hoisting,-which determine in the main the character of drilling mechanism and structures. There are endless ramifications, however, in the execution of these fundamental operations, according to the purposes for which the bore holes are drilled, their maintenance after completion, the protection and convenience of workmen, etc. The three main lines of use for bore holes are in mineral exploration, the sinking of water and salt wells, and the exploitation of petroleum and natural gas. This paper has to do more especially with the last. Here again there are many divergences. Wells may be drilled by either the percussive, the hydraulic, or the abrasive method. Finally, each of these methods, as applied by drillers of diverse nationalities, has followed somewhat different lines of development. The American system of cable-tool drilling has perhaps had the widest application; the hydraulic rotary is also in extensive use; but the Canadian system, the Galician system, and the Russian free-fall system all have their points of recognized merit and are preferred by operators accustomed to their use. These differences in drilling procedure, which rest ultimately on essential variations in geological conditions, are reflected in the chilling structures as well as in the drilling mechanism. The purpose of the present paper is to record those stages in the development of the application of steel to the construction of drilling mechanism and structures with which the writer has been intimately associated, and to contribute to the history of the art of drilling other data acquired in the course of his personal investigations. It is necessarily limited by reason of space to American practice, with especial reference, therefore, to the cable-tool system and the hydraulic rotary method of drilling wells for oil and gas.

Jan 11, 1915

By C. S. Sivil

To modern civilization the platinum metals are of inestimable value. Their distinctive properties, both physical and chemical, render them indispensable in an age in which the processes of the laboratory are becoming an essential part of the daily life of the world. Generally, their function, though vital to particular processes, is not spectacular, and so remains unknown to all except the operators. EARLY METHODS OF MANUFACTURE The properties of platinum were recognized as of prime importance for scientific work at. a very early date, probably between 1750 and 1760. The difficulty of making articles from it seemed almost insurmountable, because no means of attaining the temperature necessary to melt it were known at that time. It is true that solid platinum could be obtained by fusing the metal with a more volatile metal such as arsenic, which was subsequently driven off by baking, but such a method, at its best, would give only a very brittle product, which was totally unsuitable for the purposes for which it was intended. Little, if any, progress could be made until it was discovered that platinum sponge, heated to white heat and hammered in an iron or clay mold, would metallize and retain the shape of the mold. This was a process that could not be wholly satisfactory but from it developed the method of pressing the sponge in a mold and forging it at white heat into wire or sheet. At present a somewhat similar process must be used for fabricating articles of tungsten, molybdenum and other metals of high fusing point, as with these metals we face today the same problems that the scientists of the eighteenth century encountered with platinum, but possibly the next significant advance in the metallurgy of these metals will be the devising of means to melt and cast them.

Jan 1, 1931

By Frank C. Schrader

Page Introduction.............................. 196 Geology of the District......................... 196 Ore Deposits of the District....................... 198 Gcncral Description........................ 198 The Cerbat Mountains Group................... 199 General Description...................... 199 Tennessee Mine....................... 203 Midnight Mine........................ 203 Mineral Park........................ 204- Golconda Mine........................ 204 Other Ore-bearing Districts.................. 205 Lost Basin District ...................... 205 The Black Mountains Group.................... 206 Tom Reed-Gold Road District...................... 208 General Dcscription........................ 208 Development........................... 209 Topograplly............................ 210 Geology.............................. 210 Ore Deposits........................... 213 General Dwcription...................... 213 Zones.......................:....215 Structure of Ore Shoots.................... 217 Gold Road Mine ......................... 218 General Description...................... 218 Geology........................... 218 Ore Deposits......................... 219 Tom Reed Minc......................... 222 General Description..................... 222 • Ore Deposits.......................... 222 Development......................... 223 Character of Ore....................... 224 Other Mines........................... 224 Fields Similar to the Ton1 Reed-Gold Road District......... 227

Jan 1, 1917

By N. J. Grant, C. F. Flo, F. B. Cuff

An investigation of the Ti-Cr system has shown the presence of a complete series of solid solutions in the ß phase, with a minimum in the solid us near 50 pct Cr. An intermetallic compound, TiCr2, forms during cooling from the ß solid solution. There is a eutectoid reaction at the low chromium side of the system. IN view of the recognition of the potentialities of titanium and its alloys as important structural materials there has arisen a need for a systematic investigation of various titanium binary diagrams. Of these, the Ti-Cr system was of particular interest because of the improved properties imparted to titanium by small chromium additions. A literature survey disclosed a partial constitution diagram that had been suggested by Vogel and Wenderott,¹ This diagram, shown in Fig. 1, is the result of work done on the Fe-Cr-Ti ternary system. Alloys containing less than 43 pct Cr were not investigated. In addition to this, a study of alloys in the Ti-Cr system was reported by McPherson and Fontana.² Adenstedt3 furnished a number of dilato-meter curves obtained from specimens containing 5, 10, and 15 pct Cr. Very recently, McQuillan4 submitted a proposed diagram covering the complete range of compositions between titanium and chromium. This diagram was in general agreement with the one described here. Experimental Procedure Sponge titanium (99.7 pct) and electrolytic chromium (Bureau of Mines analysis: 99.03 pct Cr, 0.40 pct Fe, 0.53 pct O2) were used for the initial determination of the system. Subsequent refinement of points, particularly for the low chromium side of the diagram, was accomplished by using iodide titanium and high purity chromium (National Research Corp. analysis: 0.050 pct C, 0.045 pct O2). The Ti-Cr alloys were prepared by melting 25 g charges in an enclosed, water-cooled copper crucible using a movable tungsten electrode. The atmosphere was helium, prepurified by first passing it through a drying agent and then through sponge titanium heated to 850°C. Particular care was taken to avoid any large scale segregation resulting from insufficient mixing of the components. Each charge was melted and kept molten for approximately 1 min, allowed to cool, inverted, remelted, and kept molten for an additional minute. In order to ascertain the amount of impurity pickup (oxygen and nitrogen) during the melting procedure, three iodide titanium specimens were melted in sequence and then checked for increased hardness. The specimens in the as-cast condition showed a relatively large hardness increase over the hardness of the as-received iodide titanium. The scattering on these readings was large. However, after the specimens had been homogenized at 840 °C for 2 hr and slowly cooled, the measured increase in hardness over the as-received titanium was small with a corresponding decrease in scatter. The reason for this hardness change is that in heat treating these specimens below the transformation temperature (885°C) there was a conversion from the as-cast structure to the more nearly equilibrium structure of the annealed specimen. The alloys were analyzed for chromium content and although the actual percentage was invariably low the deviation from the nominal composition never exceeded 0.6 pct Cr.

Jan 1, 1953

By ALEXANDER L Hay, Alexander L.

THE Sydney coal field, the largest and most valuable in Nova Scotia, is on the northeastern coast of the Island of Cape Breton, extending from Mira Bay on the south to Cape Dauphin on the north, a distance of 30 miles, and has a general dip northeast under the sea. The field embraces the mining villages of Morien, Birch- grove and Reserve and the towns of Dominion, Glace Bay, Waterford and Sydney Mines. The city of Sydney is about midway between the northern and southern extremities of the field and on the western fringe of the productive coal measures. Sydney harbor crosses the coal field, cutting off direct rail connection between Sydney Mines and the greater part of the field to the southeast.

Jan 1, 1928

By O. Jay Myers

The war effort has furnished the necessary impetus for better magnesium foundry practice. Four or five years ago, there were but a few formulas in general use for core-sand mixtures for magnesium castings. Certain sands, binders, and inhibitors were specified and the proportions of these materials in each mixture were maintained between very narrow limits. As more and more war industries entered the field, much research was carried out and methods and practices were improved. Magnesium founding is still in a state of flux; therefore it is not uncommon to find one foundry spraying inhibitors on its cores, and another foundry using sand mixtures with incorporated protective agents. The basic core or dry-sand mold mixture for magnesium in use today is compounded with sand, core oil or resin binder, cereal, and moisture. Core oil or resin binder are added for baked strength while the cereal binder and moisture are for green strength. The normal mixtures (based on the weight of the sand) contain from o.5 to 1.5 per cent of both cereal binder and core oil, and the moisture content variesbetween 1.5 and 5 per cent. The ratio of core oil to cereal binder varies from 60:40 to 40:60, while the correct amount of moisture depends upon the method of coremaking. Protective Agents In all magnesium practice, protective agents are used in conjunction with the core and molding sands to prevent oxidation of the metal. The use of these inhibitors is not novel, but publications covering this field are not entirely adequate. Beck1 says: Magnesium alloys decompose water to form magnesium oxide, hydrogen being liberated in the process (Mg + H2O ? H2 ?+ MgO). This reaction results in the blackening of the skin and the appearance of areas of porosity on the casting surface, the cavities of which are filled with a grey oxide powder (these are termed 'burns'). Although sand cores for magnesium castings are thoroughly dried during the baking cycle, burning will take place on the casting5 unless the metal is protected properly. This type of burning is more difficult to define than the "water-magnesium" reaction cited by Beckl A possible explanation may lie in the following equation: 2Mg + O2—> 2MgO Here, the source of the oxygen is not water, but the air in the mold cavity, together with the chemically combined oxygen in the core-binding media. Generally, two methods are used to prevent this reaction from taking place.

Jan 1, 1945

By George A. Morrison

The Columbia Chemical Division of the Pittsburgh Plate Glass Co. is at Bar-berton, Ohio, 35 miles south of Cleveland. For many years large tonnages of limestone have been brought to the Barberton plant from distant points. The stone is here burnt in vertical kilns, the resultant product then hydrated and the hydrated lime used in chemical processing. To eliminate the expense of these shipments, the company decided to investigate a limestone bed known to exist on company property at Barberton, where the stone is used. The bed lay at a depth of more than 2000 ft. and was known locally as the "Deep Lime." Chemical analyses of sludge from churn-drill holes made some years ago proved that the limestone was of sufficient purity to warrant diamond-drill exploration. Four diamond-drill holes were put down at well-spaced intervals, to represent fairly an area of four miles by one mile. Cores logged as to chemical and physical conditions were found to compare closely, and to corroborate the earlier evidence that the limestone was of superior quality for chemical use. A plant of 300 tons per hour was subsequently decided upon. SITe The yard at the chemical plant was already so congested that location of the projected mine within its area could not be considered. Eventually a site was selected 2 miles northwest of the plant, near the main line of the Erie Railroad. Here 412 acres were owned outright by the company and stone rights were obtained on 2 50 additional acres. This location required a transportation line of nearly 2 miles (8800 ft.), crossing two major highways, and to avoid interruption of deliveries to the plant, overpasses were planned. Geology The limestone in the immediate vicinity lies about 2200 ft. below the surface. Geologists* identify this stone as Delaware of Devonian age. It is overlain by 18 ft. of unconsolidated (sand and gravel), 100 ft. of water-bearing sandstone, and finally 2080 ft. of shale into which sandstone in thin layers is interbedded. The contact of shale and limestone is abrupt, flat-lying and very pronounced. Berea sandstone, often found at 520 ft., is absent, but Euclid sandstone was encountered, together with a seepage of oil and a small amount of methane gas. The limestone bed itself is 345 ft. thick, and overlies 200 ft. of gypsum. The lower part becomes dolomitic as it approaches the gypsum. A detailed study of the drill cores indicates that the upper 50 ft. are highest in lime and reasonably low in silica. The physical make-up shows several separating cherty layers. These occur at definite horizons and cause distinct partings, which become horizontal planes of

Jan 1, 1946

By C. A. Stewart

PAGE. I. Introduction............ 241 II. Location. TopoGRaphy. and History....... 243 III. DescRiption of the Rocks......... 245 1. Altered Sediments.......... 245 2. Alaskite........... 246 3. Alaskite.Porphyry.....255 4. Quartz Dikes........... 257 5. Biotite.Granite.......... 256 6. Quartz.Porphyryl......... 260 7. Andesite........... 262 8. Miscellaneous Dikes......... 263 IV. Age oF the Rocks and Comparison with other Localities.. 263 V. AlteRation............ 265 1. Sericitization........... 265 2. Silicification........... 266 VI. StRuctuRes........267 1. Dip of the Limestone......... 267 2. Faulting........... 267 VII. Contact - metamorhism,.......... 269 1. Endomorphism.......... 269 2. Exomorphism......... 271 Recrystallization and Loss of Color...... 271 New ,Minerals.......... 272 Addition of Material........ 274 Volume.Changes.... 276 Locus of Metamorhism........ 277 Method of Precipitation.........278 VIII. ORe-Deposits............ 278 1. Contact-Metamorphic Copper.Ores,..... 279 General..........279 Shape and Distribution........ 279 Minerals........... 281 Secondary Enrichment........ 282 2. Disseminated Copper.Ores........ 283 3. Origin of the Copper.Orcs........ 284 4. Lead-Silver Ores.......... 287 IX. Bibliography............ 288

Jan 1, 1913

A development drilling and bulk sampling program should furnish the following information: (1) geology of the mineralized zone, (2) quantitative data on grade and tons of material within pertinent cutoff limits, (3) physical size and shape of the deposit and areas underlain by waste as well as ore, (4) mineralogical and metallurgical characteristics of the ore, (5) physical characteristics of the ore, (6) bulk samples for metallurgical testing and grade, (7) data on factors that affect mining operations, such as ground water and ground conditions. The method and equipment best suited for a particular drilling job depend upon the geologic features of the mineral deposit to be tested.

Jan 10, 1967

TWO recent developments in open hearth steelmaking have had a substantial impact on metallurgical practices and operating procedures. These are: (1) the use of oxygen roof lances for accelerating the refining reactions, and (2) the use of a spring-arch, basic roof for prolonging the life of the furnace. Although these practices can be used separately, they are generally used to complement each other in an effort to obtain minimum heat time consistent with an acceptable rate of wear of the refractory roof, walls and port ends. DECARBONIZATION BY OXYGEN INJECTION The use of oxygen to speed carbon elimination was perceived by Sir Henry Bessmer but its practical use in steelmaking could not be realized until processes were developed for the manufacture of low cost, tonnage oxygen. However, as early as 1922 Bigge1 obtained a patent covering the use of gaseous oxygen to speed decarbonization of a molten steel bath. At that time, oxygen was available only in bottles and at a cost of $240 per net ton. At the end of World War II the price of oxygen had dropped to $80 per net ton, and as a result, metallurgical oxygen (99.5 per cent began to come into widespread experimental use for decarbonization in open hearth and electric furnace shops.2-8 Even this price prevented oxygen's routine use for other than decarbonizing the bath in shops producing substantial quantities of steels containing less than 0.40 per cent carbon. Today, tonnage metallurgical oxygen can be manufactured for less than $15 per net ton, and commercial purity oxygen (95 per cent is reported to cost less than $5 per ton. Thus, it is not at all surprising to find many open hearth shops effectively using large quantities of oxygen to accelerate decarbonization. Equipment for Oxygen Injection. The oxygen may be injected by a lance pipe inserted through the wicket hole and pushed several inches into the steel bath, or by a water-cooled jet inserted through the back- wall, endwall, or roof, and immersed in the slag or set just a few inches above the slag. Oxygen at approximately 100 psi is piped directly to control stations adjacent to each furnace. The installations should include adequate safety devices such as fire checks and emergency valves,

Jan 1, 1964

By W. A. Longacre

IN the geophysical exploration program of the Cleveland-Cliffs Iron Co. on the Marquette Range of Northern Michigan, the vertical intensity magnetometer has been used to obtain magnetic anomaly maps of large areas. A network of magnetic base stations has been established and the relative vertical intensity at each station measured carefully with respect to a prime base. In the search for the relatively nonmagnetic soft red hematite ore, the magnetic exploration is indirect, involving the study of dikes, faults, contacts, and other structural features. It was found that the, magnetometer, adjusted to a scale value of approximately 40 y per scale division, was satisfactory for this type of exploration, although many magnetic anomalies were encountered that required the use of auxiliary magnets.

Jan 10, 1951

By Eugene F. Poncelet

GLASS squares compressed on edge by steel jaws in poor contact with them developed jagged "partial-contact" cracks caused by the formation of local tensile stresses. Compressed by steel jaws in perfect contact, they developed smooth "release cracks" during release of the pressure, caused by the formation of local tensile stresses during the release of the pressure. All these cracks were parallel to the pressure. A Microflash photograph of a disintegrating specimen under sufficient pressure reveals a network of fractures roughly normal to each other, also "release cracks" and a disintegration cloud. The Griffith theory is amended to account for the formation of a first crack. A new theory, based on the theory of thermal agitation and wave propagation, is proposed to account for the progress, velocity and forking of cracks. The network of fractures is shown to have been caused by reflection at a free boundary of pressure pulses emanating from a first crack. Postulating equal distribution of energy in the pulses emitted on either side by a crack in particles, the smaller fragments are shown to continue fracturing preferentially while some of the coarser fragments remain as residual pieces. As comminution of the smaller fragments proceeds, the solid is reduced to a collection of residual particles of smaller and smaller sizes, accounting for the disintegration cloud. EXPERIMENTAL PROCEDURE Apparatus A crushing device was built, consisting of a steel frame and two polished, hardened steel jaws to crush plate-glass samples. This device was placed between the plates of a hydraulic press (Fig. I). For centering the pressure, the upper jaw was guided vertically and provided with a rounded top. Later it was replaced by a steel jaw ground out of a 2 1/2-in. steel ball, the lower surface being ground to an optical flat (Fig. 2). Four rollers were used to eliminate side thrust. Screws and centering blocks served to center the specimen in the crushing device. Hard steel shims placed under the shoulder of the upper jaw limited the "follow through" of the jaw after failure of the specimen. Stress distribution was first examined with a polariscope mounted on an optical bench, using monochromatic light. It was found convenient to mount polaroid, quarter wave and monochromatic plates directly on the device itself. A Microflash unit* was used as light source for the photographs. A gold-paint pattern was fused on the plate-glass specimens and connected into the spark-

Jan 1, 1944

By J. M. Donkers, R. de Groot

The various objectives of dredging at sea require different methods and radically different equipment for their optimum fulfillment. In the majority of cases, sea dredging is done by means of dredging equipment connected to a pontoon or ship floating at the surface. As the supporting hull is subject to the influence of waves, swells, currents and wind, the connecting point of the dredging equipment to the hull will generally move relative to the sea bottom with 6° of freedom. The more important hull motions are surge, heave, pitch and roll. Depending on the actual sea and weather conditions and the size of the hull, some of these motions can be so large that dredging equipment of rigid construction (normal or inland dredges) cannot be used. In those cases where mechanical disintegration of the bottom is necessary and where accurate dredging is required, the designer must find a solution for this problem. For cases where the bottom consists of soils that can be handled by plain suction, highly sophisticated dredging equipment such as the trailing suction hopper dredge permit dredging under all but the most severe sea state conditions. This type of dredge picks up the soil from the sea bottom while slowly underway. The drag suction head is fitted on a suction pipe of such flexibility that the supporting ship can carry out all six movements in relation to the draghead (heave, pitch, roll, sway, yaw and surge), while the draghead remains in firm contact with the bottom. The suction pipe is fitted with flexible hoses, a universal hinge, a horizontal hinge, axial turning gland and sliding turning gland with horizontal axis and is suspended flexibly from the ship incorporating swell compensating buffer gear, keeping the wires taut and the draghead bottom contact pressure fairly constant while the dredge moves up and down. Due to the fact that the draghead has a low bottom contact pressure and has little tendency to sink into the bottom, this compensation is not difficult to realize.

Jan 4, 1974

By G. S. Rice, J. A. Davis

The Péchelbronn oil field is located in the province of Alsace, in the Rhine Valley, about 30 miles north of Strasbourg. It is approximately 4 miles wide and 12 miles long, extending from the villages of Lobsann on the north to Wintershausen and Ohlungen near Haguenau on the south. (See Fig. 1.) The productive area includes about 44,000 hectares (107,680 acres). The name Péchelbronn signifies "pitch-spring" or "pitch-fountain." The first exploratory galleries were driven in from the hillside in 1735; and in 1745 the first official concession was granted by the French government and the first pit sunk to a depth of about 30 ft. Extraction by drilled wells was begun in 1879, supplementing the mining operations, and during the next 10 years 200 wells were drilled to an average depth of 172 m. (568 ft.). The bringing in of two "gusher" wells, in 1882 and 1888, respectively, was followed by the abandonment of all underground work. Underground mining, with a view to increasing the production of petroleum by recovering the oil left in the sands after drilling wells, was resumed in 1916. This mining operation started by sinking shaft No. 1 to a depth of 150 m. (495 ft.). The underground developments were pushed during 1917 and 1918 and the annual production of the Péchel-bronn field was increased to about 50,000 metric tons or 350,000 bbl. On the signing of the Versailles Treaty the province of Alsace, which had been taken by Germany as the result of the war of 1870, was returned to France, and the proprietary rights were taken over by the French Government. Concessions or leases, which embraced all the known oil-bearing territory of the field, were granted to the present operating company, Mines de Péchelbronn. This company followed both the drilling and the mining methods of the previous company.

Jan 1, 1927

By Yinchang Wang

1. INTRODUCTION 1. Subject, and Scope The formation of the oxidized ores of zinc has been recognized as a subject of great importance in economic geology. For many years these ores have been much sought, partly because they are more desirable for metallurgical treatment and partly because they are apt to be freer from gangue than is the sulphide of zinc. Up to very recent years the oxidized ores were the principal source of the metal and at present they still furnish a large portion of the commercial production. . The oxidized ores of zinc include six minerals, as shown in the-following table

Jan 9, 1915