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By W. H. Emmons

Many mineral veins occupy faults, and movements on certain warped fault planes have resulted in openings. On normal faults the steeper parts have the widest openings, and on reverse faults the flatter parts have the widest openings. Theoretically the width of the opening is the sine of the angle of deflection times the amount of movement on the fault plane, but actually the widths of some of the openings are probably less because of readjustments of walls along joints or of other readjustments. The first treatment of the subject seems to have been in a book on mineral veins by John Leithart, published in Newcastle, England, in 1838. Later the subject was treated in various texts published in Germany, in England, and elsewhere. The subject was not given much prominence in the earlier American literature on economic geology, but has interested several workers in that field in the past decade. In this paper examples of districts showing ore shoots on warped faults, with relations noted, are described. Fault veins of the three depth classes of veins are noted. Many epithermal veins are in normal faults, and commonly the larger ore shoots are in their steeper portions. Many mesothermal veins are in reverse faults and, many others are in normal faults. The flatter parts of veins in reverse faults are commonly wider than the steeper parts, although they are not always as rich as the steeper segments of the veins. There are not many hypothermal veins in faults of measured displacement. Introduction When faults are followed along dip or strike, many of them are found to have curving or warped surfaces, and cross sections through them in most directions show sinuous or waving intersections. Openings are formed where one wall moves away from the other (Figs. I,2). Where there is a bend in the fault, movement in any directions except along the axis of the bend will

Jan 1, 1949

By W. H. Emmons

Many mineral veins occupy faults, and movements on certain warped fault planes have resulted in openings. On normal faults the steeper parts have the widest openings, and on reverse faults the flatter parts have the widest openings. Theoretically the width of the opening is the sine of the angle of deflection times the amount of movement on the fault plane, but actually the widths of some of the openings are probably less because of readjustments of walls along joints or of other readjustments. The first treatment of the subject seems to have been in a book on mineral veins by John Leithart, published in Newcastle, England, in 1838. Later the subject was treated in various texts published in Germany, in England, and elsewhere. The subject was not given much prominence in the earlier American literature on economic geology, but has interested several workers in that field in the past decade. In this paper examples of districts showing ore shoots on warped faults, with relations noted, are described. Fault veins of the three depth classes of veins are noted. Many epithermal veins are in normal faults, and commonly the larger ore shoots are in their steeper portions. Many mesothermal veins are in reverse faults and, many others are in normal faults. The flatter parts of veins in reverse faults are commonly wider than the steeper parts, although they are not always as rich as the steeper segments of the veins. There are not many hypothermal veins in faults of measured displacement. Introduction When faults are followed along dip or strike, many of them are found to have curving or warped surfaces, and cross sections through them in most directions show sinuous or waving intersections. Openings are formed where one wall moves away from the other (Figs. I,2). Where there is a bend in the fault, movement in any directions except along the axis of the bend will

Jan 1, 1949

By Kerstin Malmqvist

A prospecting project for deep-seated sulphide ore bodies will be expensive and means a considerable economic risk. The high costs depend on the demand for extensive drilling. It is therefore important to find effective methods to estimate the outcome of different prospecting strategies. The results from a preliminary study of the possibility of using mathematical methods for this purpose are presented. We have found that mathematical methods, especially simulation technique, might be an important tool in such exploration work. A mathematical model of an ore field and of a drilling procedure has been constructed. A set of parameters describes the geometry, the size distribution and the intensity of ore bodies. Another set describes the geometry and the intensity of drill holes. Some preliminary results are given of Monte-Carlo simulations and probability calculations.

Jan 1, 1977

By Harrison Schmitt

The Parral area, a part of the Parral mining district of Southern Chihuahua, is situated in and near the City of Parral, with the most important mine of the district, La Prieta, lying within the city limits. The famous Veta Colorado and Palmilla veins near Villa Escobedo or Minas Nuevas are a few kilometers to the northeast (see Fig. 1). The chief metals produced are silver, lead and zinc, with some copper and gold. This area was one of the earliest to produce metal in Mexico, according to records at Parral, which show that mining started in 1632. In near-by Santa Barbara, however, mining had begun 85 years earlier. It is said that when silver was discovered in the Veta Colorado, the Santa Barbara gold deposits, at that time nearly exhausted, were immediately abandoned for the more profitable silver mines at Minas Nuevas (New Mines) During the post-revolutionary period, 1923-1928, the author made many trips to the Parral district to do mine examination work for several units of the American Smelting and Refining Co. This paper is an abstract of some of the geologic data collected, together with the results of a microscopic study of the ores and rocks—the latter investigation made at the University of Minnesota—and is intended to supplement one recently published. Topography The Parral district lies in the eastern foothills belt of the Sierra Madre Oeste. The area is about evenly divided between fairly flat to rolling plains and mesas on the south and rounded hills to rough precipitous slopes on the west and north. The relief is approximately 550 m. (1800 ft.). The areas of intrusive monzonite and Jurassic (?) sedimentary rocks give rise to a topography of low rounded hills and relatively flat valleys; as contrasted with the volcanics, with their alternating beds of soft

Jan 1, 1931

By Thomas A. Hendricks

The object of this paper is to give a brief description of the coals in the different districts of Arkansas and Oklahoma, their present commercial classification, and the need for a scientific classification that shall be more nearly in accord with their physical and chemical properties and shall place them in their proper position in a general scheme of classification. The paper is based on two seasons of field work in the Oklahoma coal field in 1930 and 1931 and on several weeks spent in visiting most of the operating mines in Arkansas in the same years. Most of the productive districts of the Arkansas-Oklahoma coal field lie in an east-west trending belt immediately north of the Ouachita Mountains, but the northwestern districts in Oklahoma trend northward toward Kansas. With the exception of the Muskogee district, where very little coal has been mined, the coal beds of the last-mentioned districts are all younger than those of the districts in the east-west trending belt. Description of the Coal by Districts Lehigh District, Oklahoma (5).1—In the Lehigh district mining has been extensive, but only three or four mines are operating at the present time. Two coal beds of workable thickness, Atoka and Lehigh, are known in this field. The greater part of the mining has been in the Lehigh, or younger bed, and all analyses available for the field have been of that coal. The Lehigh coal is very tough and blocky, the moisture and ash contents are fairly high, 6.5 and 10.7 per cent respectively, the volatile content is 39.5 per cent, fixed carbon 43.4 per cent, B.t.u. value 11,525, and the fuel ratio 1.1 (average 15 analyses). So far as the writer has been able to ascertain, laboratory attempts to coke this coal have been unsuccessful and no attempt has been made to produce coke commercially. Tulsa District, Oklahoma (l).—All commercial mining in the Tulsa district has been by stripping from the Dawson bed, and production has never been very great. The coal is blocky, contains 6.5 per cent moisture, 36.8 per cent volatile matter, 48.4 per cent fixed carbon, and 8.3 per cent

Jan 1, 1932

By Howard Smith

FOR several years this Institute has recorded in its TRANSACTIONS the various discoveries of potash? in America, and the successive stages in the development of an independent domestic potash industry. This paper is intended primarily to continue the record through the year 1935. In retrospect it is not inappropriate to note that public interest aroused in 1910 resulted in the production of some 1090 tons of pure potash in 1915, as a small beginning in the domestic inorganic potash industry, and that the infant industry thus begun reaches its majority this year, following a record production in 1935 of about 600,000 tons of potash salts and exports to no less than 22 foreign countries, including six countries in Europe. This production, with an estimated 200,000 tons of pure potash, may be compared with a production in 1934 of 430,157 tons with an equivalent of 144,342 tons of pure potash.

Jan 1, 1936

By J. J. Rutledge

The United States Bureau of Mines established at Bruceton, Pa., in 1909, an experimental mine, for the purpose of testing the means of preventing and limiting mine explosions. During the last ten years numerous explosions have been caused to originate in this mine for investigative purposes and the rate of propagation of the explosion wave, the pressure developed per unit of area by the explosions, and the general results of the explosions have been carefully recorded and studied. Means of preventing mine explosions or of limiting them to the areas in which they originate have been developed. A great deal of valuable information has been derived from the work in this mine and much more useful and Valuable information will be obtained in the future. The writer would plead, not for the opening of experimental mines in all the important coal-producing fields in the United States, but for the opening of demonstration mines, or mines in which experiments could be made with the various details of coal mining. The United States Department of Agriculture has established, in nearly every state, stations that undertake experimental work for the benefit of the agricultural interests. In addition, small demonstration plats are set aside, in suitable locations in the farming districts, where various crops are grown under scientific direction, so that the faimers in the neighborhood can note the results obtained and profit thereby. Something like this should be done for the coal-mining induatry. If experimental or demonstration mines were established, methods of working adapted to local conditions could be worked out. Owing to competition in the same markets, small capitalization, or low profits, it may be an utter impossibility for any one company to try a new method of mining. Labor conditions may prevent the trial of a new method of working. It may be impossible or inadvisable to disturb existing working conditions for fear of causing trouble among the miners through real or fancied changes in the scale of wages. The first and most important investigation to be undertaken in these demonstration mines would be the trial of various methods of working coal mines until a satisfactory plan had been demonstrated for each

Jan 1, 1920

By J. Jay Jacobsen

A dynamic regional coal development model is constructed for the Eastern Powder River Basin of Wyoming. Using this model, alternative development schedules from a recent environmental impact statement submitted to the Department of the Interior are simulated (Ref. 1). These alternatives include different mixes of export capacity, different coal conversion techniques within the region, as well as various levels of coal production. Exportation of 70 to 80 percent of an ultimate coal production of 180 million tons (163.3 x l09 kg) per year and the careful phasing of additional public services with population growth effectively reduce the social and environmental impacts of coal development. The alternative involving the addition of 43,000 megawatts of electrical generation capacity has very significant adverse social and environmental impacts on the region.

Jan 1, 1977

By J. L. Bruce, N. B. Braly, F. A. Linforth, Wm. B. Daly, Paul A. Gow, C. L. Berrien, R. H. Sales, P. F. Beaudin, John Gillie, G. W. Roddewig

Butte mining district is situated in Silver Bow County, in the southwestern part of Montana. Butte originated as a placer mining camp, gold having been discovered in 1864, on Silver Bow Creek, near the southerly end of what is now Main Street. The Butte placer gold was heavily alloyed with silver, and only commanded $13 an ounce. Placer mining was vigorously prosecuted along Silver Bow Creek and its tributary gulches for about 5 years, at the end of which time, in 1870, the Butte camp was practically deserted. In the meantime, the quartz veins prominently traceable over the hillsides were located, the first location, July 12, 1864, being made by the Missoula Mining Co. and called the Missoula Lode Claim, and later relocated by G. 0. Humphreys. Reasoning from the presence of the gold placers, free milling gold and silver ores were eagerly looked for by the early prospectors. Claims covering the great Rainbow and other silver lodes were located in the 60's. The presence of valuable silver ores in these veins caused the staking of many claims, believed to be valuable only for silver, but which later, at depth, proved to be enormous copper producers.

Jan 1, 1925

By S. G. Lasky

Abraham Lincoln is reputed to have said that if you want to chart a course to some destination, you have to know where you are starting from. In this instance we have to define our starting point in a double manner: 1) What was the theoretical basis of the Paley predictions? 2) What actually did the Commission predict, so that we can see how the predictions have worked out up to now as a basis for considering how they may have to be changed.

Jan 3, 1960

By J. J. Rutledge

THE United States Bureau of Mines established at Bruceton, Pa., in 1909, an experimental mine, for the purpose of testing the means of preventing and limiting mine explosions. During the last ten years numerous explosions have been caused to originate in .this mine for investigative purposes and the rate of propagation of the explosion wave, the pressure developed per unit of area by the explosions, and, the general results of the explosions have been carefully recorded and. studied. Means of preventing mine explosions or of limiting them to the areas in which they originate have been developed. A great deal of valuable information has been derived from the work in this mine and much more useful and valuable information will be obtained in. the future. The writer would plead, not for the opening of experimental mines in all the important coal-producing fields in the United States, but for the opening of demonstration mines, or mines in which experiments could be made with the various details of coal mining. The United States Department of Agriculture has established, in nearly every state, stations that undertake experimental work for the benefit of the agricultural interests. In addition, small demonstration plats are set aside, in suitable locations in the farming districts, where various crops are grown under scientific direction, so that the farmers in the neighborhood can note the results obtained and profit thereby. Something like this should be done for the coal-mining industry. If experimental or demonstration mines were established, methods of working adapted to local conditions could be worked out. Owing to competition in the same markets, small capitalization, or low profits, it may be an utter impossibility for any one company to try a new method of mining. Labor conditions may prevent the trial of a new method of working. It may be impossible or inadvisable to disturb existing working conditions for fear of causing trouble among the miners through real or fancied changes in the scale of wages.

Jan 2, 1920

By L. L. Swift

.It the present time there are four base metals being used for automo-tive bearing alloys. Of course there are numerous variations in the amounts of alloying elements added to each base metal and nearly all of these alloys have the conventional, if not classical, duplex structure; that is, they are composed of a hard constituent embedded in a soft matrix. The well-known theory is that the former will wear well, while the latter will be plastic enough to allow the bearing to be broken in and conform to the contours of the shaft. The requirements of the modern bearing have been most aptly described by W. M. Corse: In order to meet the engineering demands of today a good bearing metal must be able to carry the weight of the shaft and stand up under steady or suddenly applied loads, or even blows ill sorne types of service. A certain amount of plasticity is desired to compensate for minute irregularities in the shaft or bearing surface, and to permit yielding, thereby avoiding dangerous stresses in bearing and shaft and pre-venting overheating and rapid wear of parts. Less plasticity is required in a bearing tuetal if the surfaces of bearings and journals are machined accurately, aligned, and kept in alignment. It is desirable, of course, that a bearing metal have a low coeffi-cicnt of friction. Under most operating conditions the friction depends on the unit, pressure of the bcaring, the speed, the temperature, and the properties of the lubricant. A good bearing metal must have a low rate of wear to reduce the necessity for frequent replacements, and adjustment of the bearings. It must wear more rapidly, however, than the journal or shaft running on it, because replacement of the journal or shaft is more difficult and costly than replacement of the bearing.' The hardness of the bearing alloy is a property closely related to several of the foregoing. With a duplex microstructure, the measurement of hardness with any of the usual commercial devices means little. The Bierbaum method of measuring the hardness of the individual canstituents was developed to fill this need. MICROCHARACTER The Bierbaum MicroCharacter~,~ measures the scratch-hardness of a solid by pulling a weighted diamond point over the surface. The diamond point is ground so that it is the corner of a cube, and Mounted

Jan 1, 1939

By L. L. Swift

.It the present time there are four base metals being used for automo-tive bearing alloys. Of course there are numerous variations in the amounts of alloying elements added to each base metal and nearly all of these alloys have the conventional, if not classical, duplex structure; that is, they are composed of a hard constituent embedded in a soft matrix. The well-known theory is that the former will wear well, while the latter will be plastic enough to allow the bearing to be broken in and conform to the contours of the shaft. The requirements of the modern bearing have been most aptly described by W. M. Corse: In order to meet the engineering demands of today a good bearing metal must be able to carry the weight of the shaft and stand up under steady or suddenly applied loads, or even blows ill sorne types of service. A certain amount of plasticity is desired to compensate for minute irregularities in the shaft or bearing surface, and to permit yielding, thereby avoiding dangerous stresses in bearing and shaft and pre-venting overheating and rapid wear of parts. Less plasticity is required in a bearing tuetal if the surfaces of bearings and journals are machined accurately, aligned, and kept in alignment. It is desirable, of course, that a bearing metal have a low coeffi-cicnt of friction. Under most operating conditions the friction depends on the unit, pressure of the bcaring, the speed, the temperature, and the properties of the lubricant. A good bearing metal must have a low rate of wear to reduce the necessity for frequent replacements, and adjustment of the bearings. It must wear more rapidly, however, than the journal or shaft running on it, because replacement of the journal or shaft is more difficult and costly than replacement of the bearing.' The hardness of the bearing alloy is a property closely related to several of the foregoing. With a duplex microstructure, the measurement of hardness with any of the usual commercial devices means little. The Bierbaum method of measuring the hardness of the individual canstituents was developed to fill this need. MICROCHARACTER The Bierbaum MicroCharacter~,~ measures the scratch-hardness of a solid by pulling a weighted diamond point over the surface. The diamond point is ground so that it is the corner of a cube, and Mounted

Jan 1, 1939

By J. A. Herbst, G. E. Agar

The effect of fluid viscosity on the classification of solids in a liquid-solid cyclone was investigated. The separation size was found to be proportional to Additionally, it was found that the prediction of flow rate through a cyclone is dependent on a Reynolds criterion. Above a critical value, the flow can be predicted by a simple equation, whereas, below this value a variable orifice coefficient must be introduced. INTRODUCTION The solid-liquid cyclone is widely used as a device for classification, thickening, and heavy media separations. The more important variables and how they affect the performance of a cyclone are known and have been the subject of several investigations.' In general, these studies have paid little attention to the viscosity and those which have, introduced it through Stokes settling considerations. Systems which contain appreciable amounts of swelling clays exhibit viscosities much greater than water, and in these systems the viscosity term becomes important in determining the separation size. The work described here was done to determine in a Newtonian system the dependence of separation size on viscosity. BACKGROUND The separation size for a cyclone classifier has been related to the parameters of the cyclone by an equation of the form: where a is probably between 1.3 and 1.5, ß is between 0.50 and 0.57, and 6 has a theoretical value of 0.5. where y has a value between 1.8 and 2.0. Although these relationships are empirical, equations that differ only in the exponents have been derived from theoretical considerations. Those interested in the origin of these equations are referred to some of the original work.6,7 MATERIALS AND PROCEDURE The laboratory apparatus used in this study is pictured diagramatically in Fig. 1. Feed slurry was pumped from an agitated 15-gallon plastic tank by a centrifugal pump driven by 3/4 hp motor. The static pressure of the feedstream and thus the pressure drop through the cyclone was measured on a gage located as close to inlet of the cyclone as possible. When samples were not being taken, overflow and

Jan 1, 1967

By R. E. Ogilvie, N. L. Peterson

Intevdiffusion and intrinsic diffusiorz coefficients were determined in the uranium-niobium system from diffusion couples analyzed with an electron microbeam probe. A Previously unveported intermediate phase, designated in this report as the delta phase, was found to exist along the mobium-rich side of the miscibility gap. Its composition width was determined from the concentration gradients in the diffusion couples. The presence of this phase was also confirmed by microhardness analysis and metallographic observations. THE excellent corrosion resistant properties, high-temperature strength and reasonable nuclear properties of niobium have prompted its use as an alloying element with uranium and as a possible cladding material for reactor fuel elements. Hence the formation and growth of intermetallic phases as well as diffusion data for the uranium-niobium system are of considerable practical importance to metallurgists and nuclear engineers. Diffusion zones may exhibit varying degrees of complexity dependi.ng upon the mutual solubility of the metals involved, and the intermediate phases which may form. In the simplest case where the metals exhibit a calmplete range of solid solubility, a single phase region is produced. Generally, however, the metals may react to produce a multiphase diffusion zone containing several layers of intermetallic phases. A number of investigatorsl-6 have analyzed the concentration gradients present in diffusion couples in order to investigate phase equilibria and solu- bility limits. If diffusion is the rate-controlling process in establishing a concentration gradient, the compositions at the interfaces of the intermediate phases will represent the equilibrium values expected from the phase diagram at the temperature at which diffusion has taken place. No published information is available at this time on diffusion in the uranium-niobium system. A number of investigators7-" have contributed information to the construction of the uranium-niobium phase diagram from other than diffusion techniques. There is good agreement on the high uranium side of the phase diagram, but the high niobium side of the miscibility gap still remains somewhat in doubt. The phase diagram as determined by B. A. Rogers, et al.7 is shown in Fig. 1. The present work was aimed at obtaining fundamental information about the solubility limits of the miscibility gap and diffusion in the uranium-niobium system. A Kirkendall effect, which might be expected on the basis of the rather large difference in melting points between uranium (1132°C) and niobium (2415" C), was also investigated. The concentration gradients were measured by an electron microbeam probe technique, similar to that used by Castaing,l2 Adda and philibert,13, l4 and Macres.4

Jan 1, 1961

By Peter N. Calder, Alan Bauer

INTRODUCTION One of the most important decisions involved in the design of an open pit mine is the selection of a slope angle. Despite this fact, engineering procedures have developed slowly in this field. Only recently have the instruments and know-how become available to undertake a design based on sound engineering principles. The effect of blasting on open pit slope stability is one aspect in which the state of the art has not developed fully. These effects include: a) the effects of the ground motion associated with blast waves on slope stability, and b) the fracturing of rock in the vicinity of slopes caused by blast waves. Natural rock jointing plays an important role in both of these. SUMMARY OF BLASTING EFFECTS In recent years there has been a trend to larger sizes of blast holes in open pits to the extent that today 9% in. and 12% in. diam. holes are the most common. The reasons for this have been economic. Larger machines are more efficient and produce at a lower overall cost per ton. As the size of blast holes have increased, so have the other factors associated with blasting. Bench heights have increased, the tons/ft. of hole yield has risen significantly and the explosive load per hole has increased. Quite naturally the rupture radius for a single blast hole has increased along with the vibration level produced per blast hole. Open pit blasting operations can result in two types of unwanted damage: 1. Damage to structures, such as buildings, dams and slopes by ground vibrations initiated by the blast. 2. Fracturing of ground beyond the planned excavation limits. Let us first consider item one. Vibration effects are determined by the type of blast which is fired and the type of medium through which the blast wave is being transmitted. They are strongly influenced by the weight of charge per hole, the number of holes per delay, the distance from the shot point, the mode of initiation, the point of interest relative to the blast, etc.

Jan 1, 1971

By Max C. Eastman, V. H. Wilhelm

California had a record year in production and drilling activity, but the results have not been sufficient to keep up with the enormous increase in demand due to war activity. During the year, 164 dry wildcats were drilled, 80 dry wells in proved areas, 31 gas wells, and 1158 successful oil-well completions for a total of 1433 wells, compared with a total of 765 in 1942. With new discoveries of only 20,000,000 and production of 283,000,000 bbl. for the year, total reserves of California oil have decreased more than 250,000,000 bbl. However, revised estimates of the reserves of old fields indicate an increase in the state's reserves of I00,000,000 barrels. The completion of 1158 wells has served only to maintain the maximum efficient daily rate of production at 800,000 barrels. There is evidence in many fields that oil is being withdrawn too rapidly to obtain the maximum recovery, and more rapidly than is conducive to good production practice. Statistics for 1943 as compared with I942 are shown in the table in the next column, Supply and Demand Steadily mounting needs of the military forces and increased industrial consumption raised total demand for all petroleum products on the Pacific Coast to 914,000 bbl. daily in 1943. That all-time record demand was 149,ooo bbl. daily higher than in 1942 and 214,000 bbl. daily above 1941 demand. Despite restrictions due to shortages of critical material, crude-oil production was boosted from 680,000 bbl. daily in 1942 to 779,000 bbl. daily in 1943, the highest level in 15 years. However, the new crude supply plus natural gasoline production and imports from other states totaled only 840,000 bbl. daily, leaving a deficiency between supply and demand of 74,000 bbl. daily. That shortage had to be made up by withdrawals from inventories, which had been steadily depleted during the previous four years. Aboveground reserves, which totaled 159,574,000 bbl. on Jan. I, 1939, were down to ~8.000,000, bbl. at the end of 1943. Significantly enough, the greater part of that decrease occurred during the last six months of I9437 when more than 23,000,000 bbl. was taken from inventories of both crude and products. Although the size of total inventories on Dec. 31, 1943 might appear substantial, about 65 per

Jan 1, 1944

By Max C. Eastman, V. H. Wilhelm

California had a record year in production and drilling activity, but the results have not been sufficient to keep up with the enormous increase in demand due to war activity. During the year, 164 dry wildcats were drilled, 80 dry wells in proved areas, 31 gas wells, and 1158 successful oil-well completions for a total of 1433 wells, compared with a total of 765 in 1942. With new discoveries of only 20,000,000 and production of 283,000,000 bbl. for the year, total reserves of California oil have decreased more than 250,000,000 bbl. However, revised estimates of the reserves of old fields indicate an increase in the state's reserves of I00,000,000 barrels. The completion of 1158 wells has served only to maintain the maximum efficient daily rate of production at 800,000 barrels. There is evidence in many fields that oil is being withdrawn too rapidly to obtain the maximum recovery, and more rapidly than is conducive to good production practice. Statistics for 1943 as compared with I942 are shown in the table in the next column, Supply and Demand Steadily mounting needs of the military forces and increased industrial consumption raised total demand for all petroleum products on the Pacific Coast to 914,000 bbl. daily in 1943. That all-time record demand was 149,ooo bbl. daily higher than in 1942 and 214,000 bbl. daily above 1941 demand. Despite restrictions due to shortages of critical material, crude-oil production was boosted from 680,000 bbl. daily in 1942 to 779,000 bbl. daily in 1943, the highest level in 15 years. However, the new crude supply plus natural gasoline production and imports from other states totaled only 840,000 bbl. daily, leaving a deficiency between supply and demand of 74,000 bbl. daily. That shortage had to be made up by withdrawals from inventories, which had been steadily depleted during the previous four years. Aboveground reserves, which totaled 159,574,000 bbl. on Jan. I, 1939, were down to ~8.000,000, bbl. at the end of 1943. Significantly enough, the greater part of that decrease occurred during the last six months of I9437 when more than 23,000,000 bbl. was taken from inventories of both crude and products. Although the size of total inventories on Dec. 31, 1943 might appear substantial, about 65 per

Jan 1, 1944

AN announcement of the annual meeting to be held in New York, Feb. 14 to 17 inclusive is being mailed to all members. Particular attention is called to the necessity of asking for certificates when you purchase your ticket in order that all may secure reduced return fares.

Jan 1, 1927

By Leon Eliel

TEN years ago .a broad knowledge of aerial mapping, coupled with a smattering of geology, qualified one to speak on the subject of the appli-cation of aerial mapping to geology. Today, with aerial maps a common tool in the hands of expert geologists on every continent throughout the world, it would be nothing short of presumptuous for the author of this paper, who is not a geologist, to give any geological statements on his own authority. Relatively, today we are only purveyors of general geological gossip, with a definite case here and there by way of illustration. But we can present a story of the really marvellous strides that have been made in the evolution of aerial mapping, built around a skeleton of geological tidbits, from which some useful conclusions may be drawn. The average geologist goes about reading his aerial maps much as one would approach the problem of deciphering a cryptogram. To begin with, typical key expressions appear in recurring sequences and under certain conditions. If once the meaning of these. isolated bits of infor-mation can be ascertained, the message begins to take meaning.. In a similar fashion, the geologist works out his key from aerial maps of territory with which he has some familiarity. He learns that a certain type of thin, white line may mean a vein of quartz. He sees that a certain change in the photographic tone of vegetation on the ground reflects two kinds of soils on opposite sides of a contact. He sees that a certain type of alignment of topographical features often means a fault. He learns that by the erosion pattern he can frequently distinguish soft formations from harder ones. And so, bit by bit, he ties together the information of the picture with his experience on the ground until he develops a reasonably creditable capacity of interpretation. Through the complete gamut of surface conditions, ranging all the way from flat, arid, exposed desert terrain to dense jungle, or rugged mountains, the evidence from which the geologist must make his inter-pretation varies with bewildering profusion. The quality of photographs which are obtainable may range from perfect pictures in the desert to almost useless smudges in the steaming jungles. One thing he has learned with certainty-the airplane carrying its mapping camera is a superb reconnaissance tool, only awaiting his ingenuity in correlating the pictures with the ground to simplify most exploratory problems.

Jan 1, 1936