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By J. M. Roberts, D. M. Barnett

The activation energy required to break a pinned dislocation line away from its condensed atmosphere of impurity atoms is calculated as a .function of applied stress, without neglecting line tension. Reasows are presented for not assuming the effect of line tension to be negligible when considering the problem of freeing a small segment of dislocation from an impurity atmosphere. The dislocation is considered to he pinned at each atomic size along its length and the pinning points are assumzed immobile. The development is a refinement of the origznal cottrell-bilby1 theory. The solution is compared to recent approximations developed by cottrell3 and Haasen5 in which line tension con- IN 1949 Cottrell and bilby1 considered the problem of determining the force required to pull a dislocation away from its condensed atmosphere of impurity atoms. They also examined the effect of thermal fluctuations on this force. The dislocation line was pictured as bowing out in a triangular loop under the action of an applied stress, and the activation energy necessary to free the dislocation from its atmosphere was calculated as a function of stress, line energy, and dislocation-solute atom interaction. siderations were neglected. A qualitative explanation of the yielding process in terms of the activation of Frank-Read sources is presented, but the lack of a realistic solution to the dynamic dislocation problem involved prevents an extension of the model at present. A self-consistent correlation between the present calculations and experimental data for delay time associated with yielding and the temperature dependence of the upper yield stress was made. Favorable agreement was noted. It is concluded that extension of the original Cottrell-~ilby' theory which includes line tension effects can just as well describe the yielding process as other approximations3,5 which neglect line tension. Cottrell and Bilby found the form of the activation energy vs stress curves to be almost independent of the line energy and the interaction energy (i.e., these parameters only affected the activation energy U by a scale factor). A check of the theory was accomplished by comparison with the experimental data of McAdam and Mebs2 for the lower yield stress as a function of temperature. cottrell,3 in 1957, attempted to obtain a simple closed-form solution for the activation energy as a function of stress by linearizing the quartic equation relating displacement of the dislocation line and applied stress. It was argued that since the contribution to the line energy/atomic plane of a dislocation is made by the long-range stress field of the dislocation through a term of the type (Gb3/2p)ln A/ro, where

Jan 1, 1963

By S C. Dominy

The grade of ore at Marvel Loch mine is directly related to the presence or absence of shear zones and quartz-sulfide-rich hornblende (¦ diopside) veining within areas of plagioclase alteration. An experienced geologist can identify these features in hand specimen. Practical rules have been developed to assist this visual identification. The structural sites and styles of alteration and veining most conducive to gold mineralisation have also been determined. The work has enabled a better understanding of the geological controls on mineralisation at Marvel Loch, and has clarified geological understanding for optimisation of grade control modeling, ore block mark-ups, and minimisation of ore loss and dilution during excavation. In addition to this, it has enabled a detailed understanding of mine scale structural controls, geometry and relative grade relationships.

Jan 1, 2003

By Alan Rice

Abstract-The mechanism by which stratiform ore deposits of PGE (platinum-group elements) are laid down in ultramafic igneous complexes is not completely clear. Early studies by the author and coworkers on numerical analyses of the convective cooling of low-Rayleigh-number magma chambers examined the effect of suspended crystal load on fluid density, and raised the possibility that the growth of the suspended crystal load during cooling could split a magma chamber into several convecting layers. The lower layers would have a higher content of refractory phases than the upper layers, which would consist of more evolved melt. This paper considers numerical modelling, as well as theoretical and experimental work in other fields dealing with suspended loads in fluids. The calculations, which are based on the physics of convecting magmas, yield quantitative relationships consistent with the observation that economically interesting stratiform PGE deposits are restricted to large magma bodies, and also yield estimation of the depth in a magma chamber at which certain grades of mineralization may occur.

Jan 1, 1997

By Alan Rice

The mechanism by which stratiform ore deposits of PGE (platinum-group elements) are laid down in ultrama?c igneous complexes is not completely clear. Early studies by the author and coworkers on numerical analyses of the convective cooling of low-Rayleigh-number magma chambers examined the effect of suspended crystal load on ?uid density, and raised the possibility that the growth of the suspended crystal load during cooling could split a magma chamber into several convecting layers. The lower layers would have a higher content of refractory phases than the upper layers, which would consist of more evolved melt. This paper considers numerical modelling, as well as theoretical and experimental work in other ?elds dealing with suspended loads in ?uids. The calculations, which are based on the physics of convecting magmas, yield quantitative relationships consistent with the observation that economically interesting stratiform PGE deposits are restricted to large magma bodies, and also yield estimation of the depth in a magma chamber at which certain grades of mineralization may occur.

Jan 1, 1997

By Renato G. Bautista

"The chemistry of the separation of metals from each other and from the other undesirable components involve multiple simultaneous chemical reactions. In the case of leaching, the heterogeneous chemical reactions between the solid and the liquid phase may be limited to a few reactions. In the homogeneous liquid phase, the number of simultaneous chemical reactions could be double or triple that of the number of heterogeneous reactions. The rate of dissolution becomes very dependent on the changing concentrations of the significant chemical species taking part in the multiple reactions in both the heterogenous and homogeneous phase. The rate expression developed for the process must take into account the mechanism of chemical reactions in order to best represent the actual process. This paper also examine the role of mass transfer with chemical reaction in the develpoment of the rate equations for dissolution, liquid-liquid extraction, membrane separation, precipitation, and electrodeposition.IntroductionThe understanding and the elucidation of the mechanism of the rate phenomena for a specific chemical reaction system is of prime importance in the development of a successful chemical process. The development of successful emerging technologies for metals separation will depend on the accurate interpretation of the intrinsic chemical reaction kinetics and the rate of mass transfer of the desired metal species during its separation from the undesirable chemical species. This is the case whether the process application is for separation, concentration, and /or purification.The chemical processes that will be examined in this presentation will include leaching, solvent extraction, membrane separation, precipitation, and electrodeposition."

Jan 1, 1996

By H. T. Clark, S. Feigenbaum

The importance of measuring the temperature of molten steel in the open-hearth furnace has been recognized for many years. Poor temperature control may be costly to steelmaking operations and lead to a lowered quality of the steel. Low or excessive temperatures may shorten the life of the furnace, ladles and molds. Rates of reactions in the furnace and efficiencies of deoxidizers are known to change materially with a change in the temperature of the metal and slag. Ladle skulls and mold and stool stickers cause steel to be scrapped instead of being converted into useful products. Finally, the structure, segregation and surface condition of ingots are affected by the teeming temperature. Mill investigations of the effect of bath temperature upon steelmaking operations have been largely qualitative in character, based upon observations by practical melting men. The physical chemist has used the empirical information available and has reached reasonable and useful conclusions with respect to the various melting processes. The introduction of a reliable direct-reading pyrometer will permit accurate quantitative evaluation of the effects of temperature and should furnish a more rational basis for study of the thermochemistry of steelmaking. The problem is not merely one of making a small numbcr of temperature measurements in the open-hearth furnace. This has been done by several methods to a * Assistant Manager, Research and Development, Jones and Laughlin Steel Corporation, Pittsburgh, Pennsylvania. Issued as T.P. 2031 in MEtals Technology, June 1946; also in Open Hearth Proc., 1946. † Open-hearth Metallurgist, Jones and 1aughlin Steel Corporation, Aliquippa. Pennsylvania. degree of precision that was apparently satisfactory. Considerable effort by a number of investigators has been directed rather to the development of an open-hearth bath pyrometer that would be both accurate and practical for routine measurements. To be practical, the pyrometer should be inexpensive to operate; that is, the installation, operating and maintenance costs should be exceeded by the tangible benefits to the open-hearth operator. Temperatures from 2800' to 3100°F. are. encountered in the open-hearth furnace. The surface of the molten metal is covered by several inches of slag, which prevents direct observation of the metal surface for optical or radiation measurements. Both slag and metal are highly reactive at these temperatures and will attack to a greater or lesser extent any material immersed in them. Adequate protectioil of thermocouples, which of necessity must be brought to the temperature of the bath, has generally resulted in a large, heavy assembly made up of brittle materials, unsuited for handling on the open-hearth floor. The life of the equipment was short and maintenance was an important consideration. Earlier Work Any of a number of Physical Properties of liquid steel could conceivably be used a a basis for temperature measurement. Efforts to the present time, however, have been confined largely to measuring either the thermal electromotive force generated between two dissimilar materials immersed in the steel or the intensity of radiation from the surface of the steel. These

Jan 1, 1947

By H. T. Clark, S. Feigenbaum

The importance of measuring the temperature of molten steel in the open-hearth furnace has been recognized for many years. Poor temperature control may be costly to steelmaking operations and lead to a lowered quality of the steel. Low or excessive temperatures may shorten the life of the furnace, ladles and molds. Rates of reactions in the furnace and efficiencies of deoxidizers are known to change materially with a change in the temperature of the metal and slag. Ladle skulls and mold and stool stickers cause steel to be scrapped instead of being converted into useful products. Finally, the structure, segregation and surface condition of ingots are affected by the teeming temperature. Mill investigations of the effect of bath temperature upon steelmaking operations have been largely qualitative in character, based upon observations by practical melting men. The physical chemist has used the empirical information available and has reached reasonable and useful conclusions with respect to the various melting processes. The introduction of a reliable direct-reading pyrometer will permit accurate quantitative evaluation of the effects of temperature and should furnish a more rational basis for study of the thermochemistry of steelmaking. The problem is not merely one of making a small numbcr of temperature measurements in the open-hearth furnace. This has been done by several methods to a * Assistant Manager, Research and Development, Jones and Laughlin Steel Corporation, Pittsburgh, Pennsylvania. Issued as T.P. 2031 in MEtals Technology, June 1946; also in Open Hearth Proc., 1946. † Open-hearth Metallurgist, Jones and 1aughlin Steel Corporation, Aliquippa. Pennsylvania. degree of precision that was apparently satisfactory. Considerable effort by a number of investigators has been directed rather to the development of an open-hearth bath pyrometer that would be both accurate and practical for routine measurements. To be practical, the pyrometer should be inexpensive to operate; that is, the installation, operating and maintenance costs should be exceeded by the tangible benefits to the open-hearth operator. Temperatures from 2800' to 3100°F. are. encountered in the open-hearth furnace. The surface of the molten metal is covered by several inches of slag, which prevents direct observation of the metal surface for optical or radiation measurements. Both slag and metal are highly reactive at these temperatures and will attack to a greater or lesser extent any material immersed in them. Adequate protectioil of thermocouples, which of necessity must be brought to the temperature of the bath, has generally resulted in a large, heavy assembly made up of brittle materials, unsuited for handling on the open-hearth floor. The life of the equipment was short and maintenance was an important consideration. Earlier Work Any of a number of Physical Properties of liquid steel could conceivably be used a a basis for temperature measurement. Efforts to the present time, however, have been confined largely to measuring either the thermal electromotive force generated between two dissimilar materials immersed in the steel or the intensity of radiation from the surface of the steel. These

Jan 1, 1947

By M. J. Ankeny

This is a study of 58 fatal haulage accidents investigated by Federal coal-mine inspectors during the period January - June 1951. The information presented in this circular was obtained by analyzing fatal haulage accidents in 33 bituminous-coal producing counties representing 11 States. The physical conditions represent a cross section off producing coal beds. Mining and transportation methods vary, from those of small hand-loading mines to those of large modern mechanized operations. These data are thought to be representative of haulage conditions within the bituminous-coal mining industry and are submitted to follow up the Information Circular 7604 ?Analysis of Haulage Fatalities in Bituminous-Coal Mines - 1950.? Coal-mine haulage ranks second as a cause of coal-mine fatalities, and the problem of haulage safety is complex. It is subject to constant change and is comprised of numerous influencing variables, which are not always obvious. The solution to this problem will not come through the application of any standard formula or mechanical approach since the inherent factors are strongly influenced by the human equation, and the chain of circumstances is further affected by expediency.

Jan 1, 1951

By John G. Koert, Koert D. Burnham, John G. Broughton

Wollastonite in Essex County, New York, occurs as a typical contact mineral in a series of rocks metamorphosed by anorthosite. Sole current use is in various types of electric welding fluxes. Its uniform lathlike shape suggests its use as a specialized filler. Introduction Wollastonite (CaSiO3) was first noted in the vicinity of Willsboro, Essex County, New York, about 1810 by Dr. William Meade, and described from the same locality in 1821 by Lardner Vanuxem.' Recent exploration and development indicate that the deposit is of adequate size for continued exploitation on a larger scale than the present operations. The only other known occurrence of like magnitude in this country is in Kern County, California.* Wollastonite has been reported from Michigan, Pennsylvania, and Lewis County, New York, but these are little more than mineral localities. Geology The Essex County wollastonite has been found outcropping at numerous separate localities in a belt of contact metamorphosed sediments, 1/4 mile wide, which begins 2 miles southwest of the village of Willsboro and trends N. 70" W. for approximately 6 miles (Fig. I). In this belt, the pre-Cambrian Grenville has been injected and partially replaced by the more liquid portions of an anorthositic magma. Bud-dington and Whitcomb3 have described the rock in this contact metamorphosed belt as "Mixed gneisses: Grenville mafic, pyroxenic and garnetiferous gneisses and skarns* with local nearly uniform garnet or pyroxene layers and with gabbroic anorthosite sheets. A few limestone layers." These rocks are underlain, presumably at no great depth, by gabbroic anorthosite gneiss, the typical Whiteface border facies of the Adirondack anorthosite massif. The occurrence of wollastonite in large quantities was discovered during the quarrying of the garnet-rich layer that overlies the wollastonite at one opening. Further prospecting revealed its presence elsewhere in the belt, overlain in most places by the garnet. Accurate tracing of the wollastonite is difficult, owing to the glacial cover and to the fact that the weathered surface of the mineral has a dark, dirty brown color, and that the wollastonite itself has been dissolved more or less completely along the outcrops. It has, however, been noted at 10 localities within the skarn belt in the first 2 1/2 miles from its southeastern end. It has not been found in the northern half of the belt and therefore may be limited to the southern half. At the Fox Hill quarry, which is the main opening, 150 ft. have been exposed, showing an aggregate thickness of 30 to 35 it. Of

Jan 1, 1948

By Koert D. Burnham, John G. Broughton, John G. Koert

Wollastonite in Essex County, New York, occurs as a typical contact mineral in a series of rocks metamorphosed by anorthosite. Sole current use is in various types of electric welding fluxes. Its uniform lathlike shape suggests its use as a specialized filler. Introduction Wollastonite (CaSiO3) was first noted in the vicinity of Willsboro, Essex County, New York, about 1810 by Dr. William Meade, and described from the same locality in 1821 by Lardner Vanuxem.' Recent exploration and development indicate that the deposit is of adequate size for continued exploitation on a larger scale than the present operations. The only other known occurrence of like magnitude in this country is in Kern County, California.* Wollastonite has been reported from Michigan, Pennsylvania, and Lewis County, New York, but these are little more than mineral localities. Geology The Essex County wollastonite has been found outcropping at numerous separate localities in a belt of contact metamorphosed sediments, 1/4 mile wide, which begins 2 miles southwest of the village of Willsboro and trends N. 70" W. for approximately 6 miles (Fig. I). In this belt, the pre-Cambrian Grenville has been injected and partially replaced by the more liquid portions of an anorthositic magma. Bud-dington and Whitcomb3 have described the rock in this contact metamorphosed belt as "Mixed gneisses: Grenville mafic, pyroxenic and garnetiferous gneisses and skarns* with local nearly uniform garnet or pyroxene layers and with gabbroic anorthosite sheets. A few limestone layers." These rocks are underlain, presumably at no great depth, by gabbroic anorthosite gneiss, the typical Whiteface border facies of the Adirondack anorthosite massif. The occurrence of wollastonite in large quantities was discovered during the quarrying of the garnet-rich layer that overlies the wollastonite at one opening. Further prospecting revealed its presence elsewhere in the belt, overlain in most places by the garnet. Accurate tracing of the wollastonite is difficult, owing to the glacial cover and to the fact that the weathered surface of the mineral has a dark, dirty brown color, and that the wollastonite itself has been dissolved more or less completely along the outcrops. It has, however, been noted at 10 localities within the skarn belt in the first 2 1/2 miles from its southeastern end. It has not been found in the northern half of the belt and therefore may be limited to the southern half. At the Fox Hill quarry, which is the main opening, 150 ft. have been exposed, showing an aggregate thickness of 30 to 35 it. Of

Jan 1, 1948

By E. Watkins, R. Kimutis, H. Dougherty

Gas wells have often intersected mining resources, but unconventional shale well drilling has more recently challenged mines to balance the risk of interaction due to higher pressures and larger quantities of gas. Full extraction mining, such as the longwall method, induces ground movement that may influence the casings if wells are drilled within the mining area. The possibility of a casing shear would lead to the risk of unplanned gas migration into the mine. This has the potential to quickly overcome the ventilation system and reach the explosive range which, if ignited, can have catastrophic consequences on the health and safety of underground workers. The utilization of network software to model mine ventilation is a common practice in the mining industry and can assist with a well breach scenario. This work focuses on a well breach in between two longwall panels after second panel mining with gas entering primarily through the gobs of the adjacent longwall panels. Applying the network software Ventsim, a gob zone and ventilation network were created to better understand the distribution of gas within the mine and the limitations and effectiveness of a ventilation system. The model shows both a transient flow simulation and steady state concentrations throughout the mine ventilation system. Using a standard Pittsburgh coal seam longwall ventilation scheme, we find that the system can dilute a significant inflow of up to 700 cfm of methane.

Mar 2, 2022

By Mark D. Kirkbride

This paper outlines the process for designing a hard rock blast in an underground coal mine. The coal mine is located in Western Kentucky and operates four continuous miner units at 7 unit-shifts per day. The mine operates in the Western Kentucky No. 11 Seam with local variations from 4.5 - 5.5 feet seam thickness. The seam has sporadic siderite deposits. Usually these deposits do not significantly interfere with the mining process. When previous siderite deposits were encountered they were small enough to drop an entry for a couple of crosscuts. The blasting plan was called for after a siderite deposit was encountered in the belt entry at about one third of the panel length. The other sides of the panel had been previously mined and sealed so the decision was made to mine through the siderite deposit with the continuous miner instead of abandoning the panel. The deposit was approximately 300 feet in length down the belt entry. Mining through the deposit with the continuous miner was expensive in both terms of production and of wear and tear on the continuous miner. A blasting plan for the siderite deposits was designed to minimize damage to the continuous miner should a similar situation occur.

Jan 1, 1999

By Carlos Enrique Arroyo Ortiz, Jadir Pedro Alves

This paper presents some of the results obtained during the research work about the use of technologies and digital transformation in the process of rock drilling in open pit mines. The use of automation presents itself as a disruptive factor and a driver of improvements that provide sustainability in rock drilling. Seven main operational parameters were utilized to combine measurement while the drilling (MWD) with other information generated by the equipment during hole drilling, in six different lithologies in an iron mine, located in the central region of Minas Gerais in Brazil. Adjustments and corrections were made to the data collected in order to minimize external influences other than the rock itself, to ensure the effectiveness of the analyses. Finally, we sought to compare the performance of the drilling process in manual and automatic operation modes. Thus, making it possible to show the efficiency and impact on the sustainability of rock drilling operations in open pit mines.

Feb 6, 2023

By Laxman M. Amaratunga, Glen G. Hein

"Most mining operations utilize the tailings coarse fraction for backfilling while the fines have been traditionally disposed on surface in tailings ponds. Recently, paste fill has been developed which uses a fraction of the fine tailings (10-30% w/w of <45 µm) in the fill (Brummer and Moss, 1991). This development allows a mining company to use a portion of the fines for backfill, but still requires surface impoundment of the unused tailings. Reactive tailings have the added problem of generating acid after being oxidized in the presence of air and water. Treating acid mine drainage (AMO) from these ponds has proven to be a costly environmental problem and a long term liability.One practical method to reduce the environmental impacts associated with the tailings pond is to modify the physical and chemical prope1ties of the fine tailings so that they can be utilized in an environmentally safe manner. This was accomplished by agglomerating the tailings into pellets and using theses pellets as a coarse aggregate in a total tailings paste fill. This technology does not require any supplemental sand or gravel to be added to the fill.This paper presents the ongoing research into utilizing these tailings agglomerates as a coarse aggregate fraction, in order to create a total tailings paste fill which has supe1ior strength characteristics.IntroductionThe Canadian mining industry produces more than 500 million tonnes of tailings and waste rock annually. The waste rock is usually returned underground for use as rock fill in underground support with the tailings remaining to be disposed of in tailings ponds. Tailings consist of a coarse and fine fraction, and can be either reactive (acid generating) or non-reactive. In an effort to minimize tailings disposal, the coarse fraction has been used underground in backfill along with alluvial sands. This diversion of the coarse fraction, however still requires that the fine fraction be disposed of in tailings ponds. This disposal creates the potential for acid mine drainage (AMO), since in the presence of air and water, reactive sulphide tailings can generate acid. It is therefore an important goal in the mining industry to minimize the disposal of fine tailings into tailings ponds since the treatment of AMO is a costly and long-te1m environmental liability."

Jan 1, 1997

Separates of all the Technical Publications published in 1930 are available at Institute headquarters. All the papers are on file in public, university and technical libraries, and when so indicated in the list, may be found in the TRANSACTIONS. Copies of these papers have been mailed to those members of the Institute who are registered in Classes A-Mining Methods; B-Milling and Concentration; C-Iron and Steel Division; D-Non-ferrous Metallurgy; E-Institute of Metals Division; F-Coal Division; G-Petroleum Division; H-Non-metallic Minerals; I-Mining Geology; K-Mining Administration; L-Geophysical Prospecting, respectively. Other members may obtain copies by writing to the Secretary. Additional copies are sold at the rate of 1 cent per page; minimum charge, 25 cents. METAL MINING TECH¬ NICAL PUBLI- TITLE AUTHOR MEETING TRANS CATION VOLUME No. AND PAGE* 264-A.29. Quicksilver Industry in 1929. Im- L. H. Duschak San Francisco T30, 283, 312 provements in the Metallurgy of C. G. Maier and Oct., 1929 Quicksilver and Symposium on The others Present Status of the Quicksilver Industry (With Discussion) (37) 271-A.30 Observation on Ground Movement R. E. Palmer New York T30,168 and Subsidences at Rio Tinto Feb., 1930 Mines, Spain (20) 274-A.31 Development and Installation of the C. L. Berrien New York T30, 139, 166 Hawkesworth Detachable Bit (29) . Feb., 1930 276-A.32 Protective Measures Against Gas O. A. Glaeser New York T30, 129, 187 Hazards at United Verde Mine (11) Feb., 1930 287-A.33 Use and Cost of Compressed Air (12) R. S. Lewis New York Feb., 1930 314-A.34 Miami Copper Company Method of F. W. Maclennan New York T30, 39, 80 Mining Low-grade Orebody (44) Feb., 1930 319-A.35 How Human Beings Respond to W. J. McConnell New York Changing Atmospheric Conditions Feb., 1930 (9)

Jan 1, 1930

To improve the air quality in large-opening stone mines by developing better ventilation techniques, including appropriate fan selection in conjunction with air-coursing methods. Background Stone mines are the most common underground large-entry mines in the United States. Data from the Mine Safety and Health Administration (MSHA) for the year 2000 indicate that there were 162 active nonmetal underground mines in the United States, of which 117 were stone mines. Many underground stone mines are drift mines developed from previous quarry operations. Typically, these room-and-pillar mines have entries that are 20 ft or higher and at least 40 ft wide. These large dimensions lead to a very small ventilating pressure loss, even when significant air quantities move through the mine. This is especially true of drift mine operations where ventilating pressure losses of <0.25 in w.g. are common. Underground stone mines with shafts that are<200 ft deep typically have ventilating pressure losses that are <2 in w.g. The pressure losses through these mines are much lower than those of a typical coal mine or deep metal/nonmetal mine. Therefore, the ventilation techniques and principles are quite different. In addition, because of new MSHA regulations that limit the concentration of diesel particulate matter, these mines may need to greatly increase their ventilation airflow. Therefore, large-opening mines need a fan that can move large air quantities and operate at low static pressures. There are three fan types for mine ventilation: centrifugal, axial vane, and propeller. Centrifugal fans are uncommon in underground stone mines as they are often associated with mines requiring the highest of ventilation pressures. Axial vane fans are widely used in all types of mining operations. They are the most common fan type currently found in underground large-opening stone mines. However, they typically do not operate at low static pressures with high efficiency. Propeller fans are currently uncommon in underground stone mines. They are designed for low static pressures and large air quantities at higher efficiency. This fan type best suits the ventilation needs in large-opening stone mines?they produce large air quantities at low pressure losses. Mines with air shafts<100 ft long and at least 12 ft in diameter have fairly low mine static pressures and may also benefit from propeller fans.

Dec 1, 2002

Discussion of papers with authors' written replies and closing remarks.

Jan 1, 1947

By Robert F. Mehl

Jan 1, 1944

By Robert F. Mehl

Jan 1, 1944

By Aug. J. Jr. Bowie

(Read at the Wilkes-Barre Meeting, May, 1877.) Brief Outline of the General Topography of the Gold Regions of California. THE topographical features of California, as demonstrated by the explorations of the State Geological Survey, are found to be exceedingly simple. Three equidistant parallel lines can be used in conveying a general idea of the physical geography of Central California. A straight or " main axial line," whose course would be north 31° west, passing through the culminating peaks of the Sierra for a distance of five hundred miles, can be assumed as the eastern boundary of the State. A second parallel drawn fifty-five miles west of the " main axial line" will skirt the western base of the Sierra Nevada, along the edge of the foot-hills. A third parallel run equidistant from the second will represent "as nearly as possible the western base of the Coast Ranges." These parallel lines divide the State into three belts, namely, the Sierra, the Great Valley of California, and the Coast Ranges. " This arrangement of the physical features holds good for a length of four hundred miles in the direction of the main axial line, comprising almost the whole of the agricultural and the greater part of the mining districts."* The section of the country which is of immediate interest to the miner is the western slope of the Sierras. These mountains, rising in a short distance from the Sacramento plains to elevations of over seven thousand feet, with occasional peaks ten and twelve thousand feet high, are cut by numerous deep and precipitous gorges or capons, through which drains the immense watershed of the Sierra, supplying the main rivers of the State and ultimately emptying into the Pacific Ocean. Between these capons, ridges or divides are formed, on top of * See vol. i, p. 5, Geological Survey of California. J. D. Whitney, State Geologist.

Jan 1, 1878