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By A. E. Gorum, I. Cornet

Fatigrle of ionic crystals has been studied primarily in magnesinm oxide. under cyclic stress dislocations move irrreversibly; they multiply; slip bands form and grow; cracks mucleate and propagnte, and failure occurs. The use of ionic crystals such as MgO is advantageorus in such investigations because they are optically transparent. Individual dislocation Intersections with {100} surfaces may be observed with a standard microscope, using etch-pit techniques. Slip, deformation, crack .formation, and fracture in MgO crystals under cyclic stress are compared with cotrresponditzg processes in metals. ThE effect of cyclic loading in metals has been studied for many years. The appearance of slip lines is readily observed and the ensuing fracture may also be seen. From these observations it is possible to predict the behavior of a material and make an educated guess as to what is happening internally, but the actual changes taking place within the structure are not readily apparent. If one could obtain a material in which the individual glide components could be observed, it would be invaluable in determining the actual slip distribution resulting from cyclic loading as well as the distribution of slip in the neighborhood of a growing crack. Such a material is magnesium oxide. Dislocation arrays may be observed by means of etch pits

Jan 1, 1961

By F. Cadena

HIWASSEE Dam, now under construction by the Tennessee Valley Authority on the Hiwassee River, a tributary of the Tennessee River, will require aggregate for approximately 800,000 cu. yd. of concrete. Near the damsite deposits of natural sand or gravel are not available and graywacke, a rock that is found in abundance, suggested itself as a likely source of manufactured aggregate. Graywacke is a metamorphosed sandstone composed principally of a mixture of quartz (65 per cent), mica (25 per cent), and feldspar (10 per cent). Other minerals are pres-ent in negligible amounts. The rock varies in different parts of the quarry from very fine to a coarse grain containing particles of about 1/4 in. maximum size, although the bulk of the deposit is medium grain. Exten-sive tests showed that graywacke would be suitable as a source of both coarse and fine aggregates. The aggregate plant available for use at Hiwassee Dam consisted of the coarse-aggregate and sand plant used on the Norris project. The coarse-aggregate plant had also been used at Chickamauga Dam. Although most of this plant equipment is now in use at Hiwassee, the present flowsheet is not only different from that at Norris and Chicka-mauga but is also unique as compared to the flowsheet of the average crushed-stone aggregate plant. It is hoped that this paper will show the importance of proper arrange-ment of equipment if the optimum in flexibility and capacity is to be attained.

Jan 1, 1939

By C. R. Austin

IN a recent paper1 the authors presented information on a refinement of the Rohn type of creep test with data on pure iron that exemplified the behavior of the apparatus. The present paper extends that work to nickel and cobalt and to the examination of the comparative high-temperature properties of two widely used commercial alloys. Careful attention has been given to the effect of plastic deformation in decreas-ing creep rate, using the elementary metals iron, nickel and cobalt for purposes of analysis. In any, endeavor to develop new materials for high-temperature service one soon encounters a real problem as to the sort of test to be employed in evaluating the commercial possibilities of the alloys. At one time it was considered satisfactory to determine the tensile strengths at elevated temperatures and to use these values as a criterion for the commercial application of the alloys. More recently the proportional limit has been used as a means of classification. Data obtained from a form of bend test has also shown promise as providing a "merit index" of high-temperature serviceability.2 Koerber and Pomp3 state that since the influence of testing time is small, the high-temperature yield point of steel furnishes sufficiently reliable and concordant values up to about 350° C. (and a maximum of

Jan 1, 1934

By Joseph Chalmers

PROBLEMS dealing with the movement or ,migration of fluids through porous beds have been the subject of much research. The subject is not peculiar to the production of oil and gas, as many investigators have studied the nature of this movement and its relationship to the problems of other industries. Darcy1 conducted a series of experiments relating to the percolation of water through filter beds. King2 carried on an extensive series of laboratory experiments with the object of formulating some conception of the rate of movement of water through soils and sand strata in the drainage of surface water into underground channels and subsequent recovery of this water through wells drilled into the source beds for irrigation purposes. Slichter3 undertook a study. of the same problem from a mathematical standpoint, and more recently Furnas4 has investigated the flow of gases through beds of broken solids with particular reference to blast-furnace operation. With specific reference to gas production, Muskat and Botset5 of the Gulf Research Laboratory undertook an experimental study to establish quantitatively the characteristics of and laws governing the flow of gases through consolidated and unconsolidated porous materials of fine texture with a view of predicting the performance of gas in an underground reservoir. There seems to be a general agreement that many of the relationships between the numerous factors influencing the flow of fluids through porous materials are far too complicated to be attacked by analytical methods based upon a knowledge of hydrodynamics. For gases, the laws of

Jan 1, 1932

By A. B. Kinzel

Since the exposition of the behavior of certain iron alloys by Sykesl involving the existence of an austenite loop and the discovery of such a loop in the chrome-iron system by Bain,2 there has been much conjecture both on his part and on the part of metallurgists in general as to the exact shape and location of this loop. In previous work commercial steel has been used and the microscope has been employed to locate the critical points so that the position of the loop has been quite approximate. Numerous attempts have been made to measure the critical points of the carbon-free alloys but all of these for one reason or another have failed. A satisfactory method for studying these phenomena is presented here. MateRial The first difficulty in this study was to obtain pure chromium-iron alloys. This has been overcome by melting in a vacuum electrolytic iron and chromium analyzing 99.84 Cr, Fe and C. A pure magnesite crucible was used and the melt allowed to solidify in the crucible. A typical analysis is chromium, 10.10 per cent., carbon, 0.006 per cent., silicon and manganese nil. To overcome the problem presented by segregation, ingots were made into wire 0.04 in. in diameter. This was accomplished by hand-forging the ingots into rods, using an oxyhydrogen flame for heating, in order to avoid carbon. Subsequently the rods were swaged to wire, the heating being carried out in hydrogen. Thus local segregation was eliminated although differences in analysis between portions 50 ft. apart were noted. An electric-resistance method was first tried to determine the critical points, but due to the physical defects in the wire this failed. Bain had previously shown the presence or absence of critical points in a qualitative way by observing the sag in a catenary. The author has devised the following method which gives an accurate determination of the critical points from expansion-temperature curves of suspended wire, a special telescopic dilatometer being used for the purpose.

By D. K. Crampton

NEARLY everyone who has not had the benefit of study in the field of metallurgy subscribes to a persistent and enthusiastic belief in the legendary lost art of hardening copper. This of course supplies a perfect introduction to a chapter of information on copper and its alloys, since the dissipation of fallacies and superstitions affecting an art probably constitutes the best method of getting at its real substance. Metals are hardened, but also embrittled, by a plurality of impurities. In the modern technology of copper-base metal products, we are familiar with a great host of materials, passing from one extreme of dead soft copper better than 99.9 pct pure, which in the form of wire about as thick as a match will stand hundreds of full twists in a 12-in. length, to an alloy containing less than 3 pct of alloyed substance possessing the strength of pretty good steel and capable of manufacture into razor blades, should we suddenly be deprived of steel; certainly a much better material for this purpose. Every copper alloy known to primitive man lies in some inter- mediate position and the ancient bronzes that have been found all over the world wherever an early civilization existed are usually contaminated by such impurities as sulfur, oxygen, antimony, arsenic, iron, or other materials, so that they could not possibly conform to any modern intelligent specification insuring the best combination of useful properties in alloys of their type and would go

Jan 1, 1953

By George Scott

MANY requests for information as to the possibility of washing coals to some predetermined percentage of ash or sulfur have suggested that the producers aim to satisfy some degree of purity set by the user of the fuel, rather than to attain the greatest economic benefit to all concerned. This paper is written to show that the highest economic purity of washed coal can be determined from washability studies of the raw coal, costs of mining and washing coal, and data on the effect of ash and sulphur on the value of the coal for the particular use for which it is intended. COKE FOR BLAST-FURNACE USE For purposes of illustration, we take the case of coal washed for coke to be used in the iron blast furnace. The method outlined can be made general in its application by substituting for the figures used here the actual operating figures for the particular case under consideration. In general, it costs the blast-furnace operation from 8 to 25 c. per ton of pig iron to slag out each 1 per cent. of ash introduced into the blast furnace by the coke. This figure depends on which one per cent. of ash is removed, and decreases with decrease in ash: When blast furnaces and coal mines are considered as a whole, the figure decreases to zero and then becomes negative, on account of low recovery of washed coal. Various figures1 have been given by different investigators: These figures necessarily differ, not only on account of the differences in operating costs but on account of the difference in the respective fuels as well. For the purpose of this paper, which, as explained, is to point out a method of attacking a certain problem, the figures used in the exposition of the method are of secondary importance. It is apparent that no universally applicable figures can be used, because there are none. Each plant has its own coal,2 its own operating cost, and its own conditions.

Jan 1, 1929

By H. M. Howe, E. C. Groesbeck

That the quiescence of a liquid while it is solidifying should favor the formation of columnar crystals, normal of the cooling surface, is seen readily on considering the mechanism of solidification. First, each particle of any composite liquid, whether it be an aqueous solution or a molten metal, in solidifying splits up into two parts, different in composition and hence in fusibility. One part is infusible at the existing temperature, and hence solidifies, and in general attaches itself to the inclosing walls of metal which have already solidified; A, Fig. 1. The other part is fusible at the existing temperature and hence remains molten. In the case of carbon steel, the part of each drop which actually solidifies is poorer in carbon than the drop itself was before it began to solidify, and this impoverishment of the solidifying half-drop enriches the other half-drop in carbon, and thus makes it unfreezable at the existing tern- By this mechanism there arises during solidification a "littoral" or shore layer of liquid B, Fig. 1, bathing the already solidified walls, and more fusible than either those walls or the great remaining central mass of liquid or " deep sea " C, from which it separates them. It is essential that we grasp clearly this conception of a fusible littoral molten layer coating the already solidified walls and separating them from the deep sea. Meanwhile heat is flowing rapidly outward through these walls, its escape cooling them, so that if any given particle of the deep sea metal could get past this littoral layer and come into contact with the solid walls, it would in turn solidify, and like its predecessors would split up in solidifying into a less fusible half-drop which would attach itself to those . walls and a more fusible one which would remain molten. Thus we see

Jan 1, 1920

By D. V. Carter, F. M. Hackbusch

Beginning the year 1938, the East and East Central Texas district comprised 48 counties, which is equivalent to the Texas Railroad Commission districts 5 and 6. At the close of the year there were 46 oil and gas fields in this district. Eight other fields, seven oil and one gas, have been abandoned. Exploratory Drilling During the year, 113 exploratory wells were drilled. Nine discoveries were made, five of which proved to be oil fields, three distillate, and one gas. Completions for the district were 2043 oil wells (distillate wells included), 36 gas wells and 163 dry holes. Exclusive of the East Texas field, the Marion County extension of the Rodessa field led the district in the number of completions during the year. Production and Proration All fields in the district produced a total of 182,369,484 bbl. of oil, a decrease of 12.57 per cent compared with the 208,594,453 bbl. produced during 1937. The East Texas field produced 148,189,913 bbl., which was 81.6 per cent of the district's production for 1938. November daily average oil production for the East and East Central district was 469,102 bbl. The estimated cumulative production to Jan. 1, 1939, for this district was 1,753,894,802 bbl. It is estimated that the East and East Central district produced 38.9 per cent of the state's total production for the year, which was 468,781,632 barrels. The decrease in 1938 production, as compared to that of 1937, in this district was partly due to the Saturday and Sunday shutdowns, 71 days for the year, which is equivalent to 19.45 per cent of the year. All fields in this district were affected by shutdowns except the Texas portion of the Rodessa field, which was shut in only during January and February. Certain wells were exempt from these shutdowns because of special pro-

Jan 1, 1939

By D. T. Jones

In view of the importance of the application of scientific principles to the production of oil from the reservoir, the Production Staff of the Anglo-Iranian Oil Co. (late Anglo-Persian Oil Co.) has been engaged for some years on an intensive program of research on the physical properties of crude oil. Problems involving the retention of crude oil in capillaries and fine fissures demanded for their solution a knowledge of the surface tension and specific gravity of the crude under reservoir conditions, and it is the purpose of this paper to describe briefly the methods adopted for the determination of these properties, and to present the more important results. A detailed article was published in volume 1 of the World Congress Proceedings (1933). Surface-tension observations on crude oil regassed at high pressures with natural gases have been made in the past by Beecher and Park-hurstl and Swartz2, but up to the time of the investigations in Iran no one seems to have carried out experiments with gas-saturated crude direct from the reservoir and kept at its original pressure. Results obtained in this manner are obviously of greater practical value for solving problems connected with the reservoir. Method of Measurement No apparatus for the measurements, under the pressure conditions involved, was available, and a suitable instrument had to be designed and constructed in the Fields workshops. Careful consideration of the matter led to the adoption of a method for measuring the surface tension which did not involve a knowledge of the specific gravity of the oils under the working conditions: the main reason for this being that up to that time no accurate determination of the specific gravity had been made under these conditions. The method adopted involves the measurement of the actual tension in an oil film, and is effected by means of

Jan 1, 1936

By Joseph A. Holmes

Although Venezuelan production attained a new peak in 1938, passing the 190 million barrel mark for the first time, there was a distinct flattening of the steep upward trend that marked 1937 and preceding years. The annual total of 190,231,780 bbl. was only 31/3 million barrels above the 1937 figure, an increase of slightly less than 2 per cent, which contrasts sharply with the 20 per cent increase of 1937 over 1936. As in the previous year, the Lake Maracaibo fields supplied approximately 73 per cent of the oil produced, Lagunillas remaining the largest single contributor in spite of a 17 million barrel decrease in its annual output. Tia Juana increased its percentage of the Venezuelan total from 14.1 per cent in 1937 to 23.4 per cent in 1938; La Rosa showed little change with 13.7 per cent; Quiriquire in eastern Venezuela was also little changed with 13.2 per cent; Mene Grande, the only other field of real importance, declined from 7.7 per cent of the total in 1937 to 6.6 per cent for 1938. Two new fields, Temblador and Bachaquero, began actively to ship oil during the year, and by November were averaging 7600 and 10,000 bbl. per day, respectively. The former is in eastern Venezuela, and the latter is the most southern of the proven Lake Maracaibo fields. (A map of Venezuela was published in Volume 127 of the Transactions.) Table 1 gives a complete résumé of Venezuelan production by fields for 1937 and 1938, and shows that 1,685,575,663 bbl. had been produced to Dec. 31, 1938. The percentage contributed by each of the principal fields to this total is shown in Table 3, as well as their trends over the past several years. From these data it is apparent that the Maracaibo Basin is the principal source of Venezuelan production, and will probably continue to hold this position for some years. At the year's end 2657 oil wells were producing, of which 2425 were in western and 232 in eastern Venezuela; 36 per cent were on natural flow, 57 ppr cent were pumping, and 7 per cent were on air or gas lift. Out of 523 wells drilled, 507 producers were completed in 1938, five less than in the previous year and nearly 100 less than in 1929. These

Jan 1, 1939

FREQUENTLY the careful engineer puts the word porphyry in quotation marks or precedes it with "so-called," when he writes of the Porphyry Copper mines. This is done by way of serving notice that he is aware that the term is not a precise one, though no one who is informed on the subject would in any event misinterpret it. The name originated from the fact that the rock containing the copper at Utah Copper, Morenci, Nevada Consolidated, and Braden-the first four to be developed-was in each instance known as porphyry. The term was convenient; and when Ray, Miami, and inspiration came along they fell into the Porphyry category even though the ore consisted essentially of a rock called schist instead of porphyry. The word is not inclusive enough; nor as a matter of fact is it sufficiently exclusive. Numerous copper deposits occur in porphyry rocks that are not Porphyry Coppers, paradoxical as it may seem. Desiring to be more accurate and at the same time to use a word that is in some degree descriptive, various engineers have adopted the expression "disseminated copper deposits." This alludes to the characteristic scattering of grains or specks of copper minerals more or less uniformly throughout the mass of the rock. Yet here again the implication is not entirely accurate, for the following reason: in some of the ores, the proportion of copper minerals "peppered" in the rock is small, compared with that which coats the walls of cracks and minute fissures; and that which is found as veinlets along planes of fracture. Many geologists have extended their interpretation of the term disseminated to include both types of mineral occurrence. One of the most striking features of the Porphyry ores is the intense shattering and fracturing that the rock underwent at some period or periods prior to the deposition of the copper

Jan 1, 1933

By D. T. Jones

In view of the importance of the application of scientific principles to the production of oil from the reservoir, the Production Staff of the Anglo-Iranian Oil Co. (late Anglo-Persian Oil Co.) has been engaged for some years on an intensive program of research on the physical properties of crude oil. Problems involving the retention of crude oil in capillaries and fine fissures demanded for their solution a knowledge of the surface tension and specific gravity of the crude under reservoir conditions, and it is the purpose of this paper to describe briefly the methods adopted for the determination of these properties, and to present the more important results. A detailed article was published in volume 1 of the World Congress Proceedings (1933). Surface-tension observations on crude oil regassed at high pressures with natural gases have been made in the past by Beecher and Park-hurstl and Swartz2, but up to the time of the investigations in Iran no one seems to have carried out experiments with gas-saturated crude direct from the reservoir and kept at its original pressure. Results obtained in this manner are obviously of greater practical value for solving problems connected with the reservoir. Method of Measurement No apparatus for the measurements, under the pressure conditions involved, was available, and a suitable instrument had to be designed and constructed in the Fields workshops. Careful consideration of the matter led to the adoption of a method for measuring the surface tension which did not involve a knowledge of the specific gravity of the oils under the working conditions: the main reason for this being that up to that time no accurate determination of the specific gravity had been made under these conditions. The method adopted involves the measurement of the actual tension in an oil film, and is effected by means of

Jan 1, 1936

By Charles Mabery

So FAR as the elementary composition of petroleum is -known, it may be briefly stated. Petroleum consists principally of a few series of hydrocarbons, with admixtures of sulfur, nitrogen, and oxygen derivatives in comparatively minute proportions, which may be regarded as impurities to be removed in the preparation Of commercial products. But as each series is represented by many homologs, in the aggregate, crude petroleum is an extremely complex mixture of hydrocarbons and their derivatives. In part, these hydrocarbons individually conform in structure to the system of synthetic hydrocarbons whose structure is well defined and -represented by the typical series CnH2n+2, CnH2n, the series CnH2n-2, CnH2n-4, the members of which have not been sufficiently studied to establish their structure, and the series CnH2n-6 composed of the aromatic group, benzene and its homologs. Hydrocarbons of greater density contained in the portions of petroleum that cannot be distilled without decomposition doubtless have less hydrogen than is represented by these formulas. Since to every hydrocarbon there is a definite temperature, even in vacuum, at which its constituent carbon and hydrogen atoms fall apart, and since for the heavier bodies this temperature is not much above 360° C. in vacuum, it is evident that some other method than distillation must be devised for their separation if anything further is to be learned concerning their individual constitution. CLASSIFICATION OF PETROLEUMS There is such a wide variation in the composition of petroleum from different fields, it would seem possible to make a classification on this basis were it not that no single variety is entirely free from hydrocarbons contained in others. Such a classification has been suggested of the exceptionally pure Pennsylvania petroleum, the sulfur oil from Trenton

Jan 2, 1920

By Joseph A. Holmes

Although Venezuelan production attained a new peak in 1938, passing the 190 million barrel mark for the first time, there was a distinct flattening of the steep upward trend that marked 1937 and preceding years. The annual total of 190,231,780 bbl. was only 31/3 million barrels above the 1937 figure, an increase of slightly less than 2 per cent, which contrasts sharply with the 20 per cent increase of 1937 over 1936. As in the previous year, the Lake Maracaibo fields supplied approximately 73 per cent of the oil produced, Lagunillas remaining the largest single contributor in spite of a 17 million barrel decrease in its annual output. Tia Juana increased its percentage of the Venezuelan total from 14.1 per cent in 1937 to 23.4 per cent in 1938; La Rosa showed little change with 13.7 per cent; Quiriquire in eastern Venezuela was also little changed with 13.2 per cent; Mene Grande, the only other field of real importance, declined from 7.7 per cent of the total in 1937 to 6.6 per cent for 1938. Two new fields, Temblador and Bachaquero, began actively to ship oil during the year, and by November were averaging 7600 and 10,000 bbl. per day, respectively. The former is in eastern Venezuela, and the latter is the most southern of the proven Lake Maracaibo fields. (A map of Venezuela was published in Volume 127 of the Transactions.) Table 1 gives a complete résumé of Venezuelan production by fields for 1937 and 1938, and shows that 1,685,575,663 bbl. had been produced to Dec. 31, 1938. The percentage contributed by each of the principal fields to this total is shown in Table 3, as well as their trends over the past several years. From these data it is apparent that the Maracaibo Basin is the principal source of Venezuelan production, and will probably continue to hold this position for some years. At the year's end 2657 oil wells were producing, of which 2425 were in western and 232 in eastern Venezuela; 36 per cent were on natural flow, 57 ppr cent were pumping, and 7 per cent were on air or gas lift. Out of 523 wells drilled, 507 producers were completed in 1938, five less than in the previous year and nearly 100 less than in 1929. These

Jan 1, 1939

By A. W. Gauger

Fox perhaps one hundred years scientists have been engaged in attempts at devising a satisfactory method of classification of coal. During this time many charts, tables and graphs have been proposed, some of which have had considerable merit, but no one system has been found to be applicable to all ranks of coal, nor has any one system received general acceptance. In many of the proposals, water eliminated between room temperature and 105° C. has been regarded as extraneous matter and calculations have been made to the air-dry or water-free basis. Such methods of. calculation do not lend themselves to satisfactory grouping of the high-moisture coals.1,2 A consideration not only of the properties of the high-moisture coals and their behavior on drying but of the generally accepted ideas of the coalification process and the role of water in this process indicates that water is an essential constituent of all coals and therefore should not be neglected. For example, in such low-rank coals as the lignites of the Northern Great Plains' deposits the inherent moisture of the lignite as mined plays a very important part in the physical properties thereof. Freshly mined lignite contains upwards of 30 per cent water and is extremely tough and resistant to shock. Upon exposure to the atmosphere, the lump loses part of its moisture and checks and splits, leaving a friable and broken up residue. So far as we have been able to determine, water is the only thing lost in this process and we are forced to the conclusion that moisture plays an extremely important part in the structural properties of the original lignite. With reference to the coalification process, Mack and Hulett3 pointed out in 1917 the important part that water played therein. They observed that water cannot be removed from peat or coal by pressure alone, but only as the result of chemical reaction, and suggested that peat in its early stages may be largely a hydrosol. Slow chemical changes occur over a long period of time until finally the mass becomes more largely a hydrogel. These views are substantiated to some extent by the experi-

Jan 1, 1932

By D. N. Stevens, D. N. Bloom, M. A. Klugman

This paper represents a portion of a larger study concerning dispersion of major, minor and trace elements in wall-rock about orebodies in part of the Colorado Mineral Belt. This phase of the work pertains to the Mg/Ca ratio variations in wall-rock adjacent to orebodies in two mines, one in the Horseshoe Mining District (Hilltop mine), and the other in the Alma Mining District (Phillips mine). The two districts lie adjacent to one another, the Horseshoe District on the south and the Alma District on the north, and are commonly referred to as one, the Alma-Horseshoe Mining District. The Alma-Horseshoe Mining District is located 80 miles southwest of Denver, Colo., (Fig. 1) in Park County, on the eastern slope of the Mosquito range. The area is typified by rugged relief with altitudes of from 10,500 to 14,000 ft. The Horseshoe District is separated from the Lead-ville Mining District by the crest of the Mosquito range, with the Leadville District to the west. The Alma-Horseshoe District has been considered as peripherial to the Leadville District, and has not received the detailed attention that the Leadville District has. These two mines were selected for this study because of their ease of access; the attitude of the workings and the drill holes to the known mineralization; the similarity of the mineralization; and because the mineralization occurs in carbonates in both mines but are of different ages. In the Hilltop mine mineralization is confined to the Leadville dolomite (Mis-issippian) and is principally lead with subordinate zinc and silver. In the Phillips mine the mineralization occurs in the Peerless dolomite and shale (Cambrian) and in the Manitou dolomite (Ordovician) and is principally zinc with subordinate lead, silver,

Jan 1, 1964

By G. R. Mansfield

THE third year of Government exploration for potash by the U. S. Geological Survey and the U. S. Bureau of Mines under the authorization of the act approved June 25, 1926 (Public 424-69th Cong.) is drawing to a close. The results thus far obtained are thought to be sufficiently interesting and satisfactory to justify the presentation of a brief pre¬liminary account of the work. REVIEW OF EARLIER EXPLORATION The general geologic similarity of the Permian basin of Texas and New Mexico to the potash field of Germany had long ago suggested the possibility of the presence of potash salts somewhere in that basin, but petroleum exploration was then making little headway there and the necessary data could not be obtained. The discovery by Udden in 1912 of potash in brine from the Spur well in Dickens County, Texas, was the first direct evidence of its presence. In 1915-17 the U. S. Geological Survey drilled a test well with standard tools at Cliffside near Amarillo, but failed to find potash. Nevertheless, an observer has been kept in the field, at first in cooperation with the Texas Bureau of Economic Geology but since 1922 by the Survey alone, to secure data and samples from oil and gas tests. Since the discovery of oil in Reagan County in 1923 exploration by drilling has been rapidly extended to many parts of western Texas and southeastern New Mexico. The identification of the potash-bearing mineral polyhalite was first announced by the Geological Survey in June, 1921, the material having come from cuttings from the Bryant well in Midland County and the Burns well in Dawson County, Texas. Successive discoveries and announcements of similar purport aroused widespread interest in potash exploration, which culminated in the action by Congress already noted.

Jan 1, 1929

By R. C. Hirschfeld, H. H. Einstein, R. W. Bruhn, R. A. Nelson

The objective of the model studies described in this paper is to determine the effect of planar discontinuities on the strength and deformability of a rock mass. A model material was used because it satisfied concurrently three requirements that available natural-rock samples did not: (1) low strength, which was desirable for minimizing the loads that had to be applied in the laboratory; (2) ease of producing test specimens with geometrically regular joint patterns; and (3) uniformity of the test specimens. The model tests were performed on specimens made from a single modeling material and tested under triaxial stress conditions with [u,=u,]. Results are presented in this paper for tests on specimens that had (1) a single joint set inclined at several angles to the major principal direction, including 0º and 90°, and (2) two joint sets that were mutually perpendicular, one set perpendicular to and one set parallel to the major principal direction. Several different joint spacings were used in each series. Future tests will include a series with two sets of joints that make oblique angles with each other and with the major principal direction. The results of model tests and tests on cores of jointed rock by several investigators (e.g., Müller and Pacher,l Moore,2 Krsmanovic and Milic,3 Hayashi,4 Rosenblad,5 Jaeger,6 and Lane and Heck 7, have contributed significantly to the design of these experiments, which are believed to be the first in which a comprehensive study has been made of the combined effects under triaxial loading of joint spacing and joint orientation (Fig. 1).

Jan 1, 1970

By D. V. Carter, F. M. Hackbusch

Beginning the year 1938, the East and East Central Texas district comprised 48 counties, which is equivalent to the Texas Railroad Commission districts 5 and 6. At the close of the year there were 46 oil and gas fields in this district. Eight other fields, seven oil and one gas, have been abandoned. Exploratory Drilling During the year, 113 exploratory wells were drilled. Nine discoveries were made, five of which proved to be oil fields, three distillate, and one gas. Completions for the district were 2043 oil wells (distillate wells included), 36 gas wells and 163 dry holes. Exclusive of the East Texas field, the Marion County extension of the Rodessa field led the district in the number of completions during the year. Production and Proration All fields in the district produced a total of 182,369,484 bbl. of oil, a decrease of 12.57 per cent compared with the 208,594,453 bbl. produced during 1937. The East Texas field produced 148,189,913 bbl., which was 81.6 per cent of the district's production for 1938. November daily average oil production for the East and East Central district was 469,102 bbl. The estimated cumulative production to Jan. 1, 1939, for this district was 1,753,894,802 bbl. It is estimated that the East and East Central district produced 38.9 per cent of the state's total production for the year, which was 468,781,632 barrels. The decrease in 1938 production, as compared to that of 1937, in this district was partly due to the Saturday and Sunday shutdowns, 71 days for the year, which is equivalent to 19.45 per cent of the year. All fields in this district were affected by shutdowns except the Texas portion of the Rodessa field, which was shut in only during January and February. Certain wells were exempt from these shutdowns because of special pro-

Jan 1, 1939