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By John W. Cabot

The following series of analyses, which may, be of interest to Bessemer-steel makers, is submitted as a contribution to the muchvexed discussion of manganese in Bessemer steel. They were made by the writer in the spring of 1881, at the works of the Pittsburgh Bessemer Steel Company Limited, during a' period of about eight days, part of. which time the rail-steel showed great variation in rolling qualities. During the first part of tile time in question, it rolled well; later on it began to roll wome until, finally, it cracked very badly, reaching its worst stage. After this it rapidly improved until it again rolled smoothly. During this time of transition from good rolling to bad, and hack to good again, the course of the manganese was followed quite closely. It is the striking correspondence between these varying manganese contents and the differences in rolling which is here presented as worthy of notice. The other ordinary elements were determined occasionally, but showed no. unusual variation: The steel, in question, was ordinary rail-steel of about the following compusition : C=35. P - .08. Mn - .98. Si = .08. 8 = .06. The samples for manganese determinations were taken at first from an average of two days' work, and later on, when the steel

Jan 1, 1882

By N. M. Saum, W. T. Caneer

Uranium may be in short supply due to the predicted energy needs in the coming years. As a result of this, a new surge of uranium exploration is underway accompanied by the refinement of numerous exploration techniques. One such technique is the monitoring of radon gas in surface soils and rocks as a guide to subsurface uranium deposits. The Colorado School of Mines Research Institute became involved in radon studies in 1967 on a project for the Atomic Energy Commission. Since that time the Institute has conducted numerous radon surveys for a large number of companies which have been active in uranium exploration. The objective of this paper is to relate the techniques utilized by the Research Institute and the results of some of the studies performed. Most of the studies performed by the Research Institute were related to roll front, sandstone-type uranium deposits. However, we have performed radon studies in various other types of rock. For those who may not be familiar with the application of radon "sniffing" in soils and rocks, a brief descriptive background should be given. The following question may be asked-why use radon as a guide to uranium mineralization? Some of the answers to this question are:

Jan 5, 1974

By K.D. White, Chester W. Washburne

Colombia has an almost ideal situation with lespect to the world's markets, being only a short distance from the Panama Canal and the West Indies. The sailing distance from its Caribbean ports to New York is less than that from Tampico. Geographically, Colombia consists of three systems of broad mountain ranges separated by two long narrow valleys. The Cauca River valley separates the Western or Coastal range from the Central range. On the west side of the Coastal range are the Atrato and San Juan Rivers. The Central and Eastern ranges are separated by the Magdalena River valley. In the department of Santander the Eastern range divides, one branch continuing northward as the Cordillera of Perija, the other turning eastward across Venezuela as the Cordillera of Merida. Between these ranges is the great basin occupied by Lake Maracaibo. These valleys consist mainly of long narrow reentrants or tongues of Tertiary sediments between the older rocks of the mountain ranges. The late Miocene and younger sediments seem to have been deposited in separated basins, but the Cretaceous and possibly some earlier Tertiary strata were laid down more or less continuously over a great part of Colombia and Venezuela. These strata were subsequently folded into the present ranges. The deposition of the Cretaceous and of some of the Tertiary was in a great sea, the main land mass being in Brazil, with land probably along some of the cores of the present mountain systems. The sediments, except the Lower Cretaceous, vary markedly in character and thickness. An illustration is seen in the massive series of non-marine conglomerates and sandstones of the upper Magdalena River valley, near Honda, which are almost wholly wanting in the coastal sections where marine sediments prevail. The oldest rocks bearing on the search for oil are the black carbonaceous and bituminous shales, limestones, and cherts of the upper part of the Lower Cretaceous. These probably are the main source of oil in both Colombia and Venezuela. They include thick bodies of true "oil shale." Above the carbonaceous and bituminous beds, lies a series of many thousand feet of clastic sediments. The most noticeable and easily recognizable formation among these clastic sediments is the "coal-bearing series," which may be either upper Cretaceous or Eocene. The

Jan 1, 1923

By K. D. White, Chester W. Washburne

Colombia has an almost ideal situation with lespect to the world's markets, being only a short distance from the Panama Canal and the West Indies. The sailing distance from its Caribbean ports to New York is less than that from Tampico. Geographically, Colombia consists of three systems of broad mountain ranges separated by two long narrow valleys. The Cauca River valley separates the Western or Coastal range from the Central range. On the west side of the Coastal range are the Atrato and San Juan Rivers. The Central and Eastern ranges are separated by the Magdalena River valley. In the department of Santander the Eastern range divides, one branch continuing northward as the Cordillera of Perija, the other turning eastward across Venezuela as the Cordillera of Merida. Between these ranges is the great basin occupied by Lake Maracaibo. These valleys consist mainly of long narrow reentrants or tongues of Tertiary sediments between the older rocks of the mountain ranges. The late Miocene and younger sediments seem to have been deposited in separated basins, but the Cretaceous and possibly some earlier Tertiary strata were laid down more or less continuously over a great part of Colombia and Venezuela. These strata were subsequently folded into the present ranges. The deposition of the Cretaceous and of some of the Tertiary was in a great sea, the main land mass being in Brazil, with land probably along some of the cores of the present mountain systems. The sediments, except the Lower Cretaceous, vary markedly in character and thickness. An illustration is seen in the massive series of non-marine conglomerates and sandstones of the upper Magdalena River valley, near Honda, which are almost wholly wanting in the coastal sections where marine sediments prevail. The oldest rocks bearing on the search for oil are the black carbonaceous and bituminous shales, limestones, and cherts of the upper part of the Lower Cretaceous. These probably are the main source of oil in both Colombia and Venezuela. They include thick bodies of true "oil shale." Above the carbonaceous and bituminous beds, lies a series of many thousand feet of clastic sediments. The most noticeable and easily recognizable formation among these clastic sediments is the "coal-bearing series," which may be either upper Cretaceous or Eocene. The

Jan 1, 1923

By M. E. Gershon

Conventional methods of drill hole site selection are reviewed briefly. Two approaches using geostatistics are then discussed, both of which have been shown to yield improved results. Finally, a branch and bound algorithm is described which will select the best locations for drilling from a user specified number of possible drill sites. Two options are discussed. First, the user can specify a maximum drilling investment or a maximum number of drill holes and the program will select the locations yielding the minimum estimation variance. This amounts to getting the most for a given investment. Alternatively, a maximum tolerable estimation variance can be specified and the program will select the number and location of the drill holes to obtain the desired information at a minimum cost. Another benefit of the approach is the quantification of the tradeoffs between investment and information obtained.

Jan 1, 1985

By F. Milton Lewis, Roshan B. Bhappu

In Part I of this article, published in the September issue of MINING ENGINEERING, Edward S. Frohling and Robert M. McGeorge of Mountain States Mineral Enterprises, Inc., reviewed the general overall financial aspects and methods of raising the necessary capital for developing the mine. In Part 2 of this two-article series, we will present several case histories to show how realistic feasibility studies are used for evaluating the choices and options entailed in mining ventures. Basically, after a potential ore body has been discovered, and the necessary funds obtained for the development of the deposit, the next major problem is one of ascertaining what specifically is to be produced, and the costs of production. The profit potential of the mining venture can then be accurately assessed by the mine owner, operator, or loan officer.

Jan 10, 1975

By J. P. Norris, W. T. Pettijohn

The Mufulira Copper Mine, Ltd., is in Northern Rhodesia, ten miles from the Belgian Congo border, and is one of the group of four operating mines comprising the Northern Rhodesian Copperbelt. The ore deposits at Mufulira are on the limb of a large syncline striking NW.-SE. and dipping NE. at about 45 deg towards the Congo border. The host rocks are well-consolidated, highly-silicified, felspathic quarzites of the lower part of the pre-Cambrian Séries des Mines of the Katanga. The ore rocks are underlain, unconformably, by the older "Muva Series," in this case hard, green, metamorphosed quarzites. There are three superimposed orebodies, the first, or upper, orebody averaging 40-ft true thickness with a strike length of about 5000 ft, the second, or middle, orebody of about 50-ft true thickness with a strike length of about 6000 ft, and the third or lower orebody of around 60-ft true thickness with a strike length of 8000 ft. The orebodies are separated by varying widths of waste, or very low-grade ore, from a few feet up to 50 ft. The middle and lower orebodies are so close together for a strike length of 3000 ft that they are mined as one orebody. In all, the mineralized zone is about 200 ft in true thickness.

Jan 6, 1950

By S. P. Goplen, M. Henriksen, T. F. Barron

In the past decade, numerous large scale drilling projects have made use of reverse circulation air lift methods. Reverse air lift pumping can be established by injecting gas into a column of liquid; the subsequently decreased density of the gas-liquid mixture allows atmospheric pressure outside the lift conduit to establish flow. The rate of flow can be controlled by varying the gas to liquid ratio. A typical reverse circulation air lift system is depicted in [Fig. 1]. Allen 1 has described a number of reverse air lift drilling projects. Although cited examples are generally related to large diameter holes, the method has seen use in other applications such as sand dredging, chemical pumping, water well pumping. and continuous coring. One particular benefit obtained with enclosed reverse circulation drilling is elimination of lost circulation. The required air/water ratio for pumping at a given submergence and lift has been established experimentally by Gibbs.2 His data, however, do not reflect sensitivity of flow rate to air/water ratio. Further, in Gibbs' work, air apparently is injec-

Jan 1, 1980

By Robert Yerkes

THE following is a brief account of the methods of measuring intelligence especially prepared for use in the U. S. Army, of typical results, and of some of their immediately practical applications. It has been prepared for the assistance of army examiners and for the information of all who are interested in the relations of scientific placement to military efficiency. PURPOSE OF THE INTELLIGENCE TESTS Under the direction of the Division of Psychology, Medical Department, and in accordance with provisions of War Department General Order No. 74, mental tests are given recruits during the 2-wk. detention period. These tests provide an immediate and reasonably dependable classification of the men according to general intelligence. Their specific purposes are to aid: 1. In the discovery of men whose superior intelligence suggests their consideration for advancement; 2. In the prompt selection and assignment to development battalions of men who are so inferior mentally that they are suited only for selected assignments; 3. In forming organizations of uniform mental strength where such uniformity is desired; 4. In forming organizations of superior mental strength where such superiority is demanded by the nature of the work to be performed; 5. In selecting suitable men for various army duties or for special training in colleges or technical schools; 6. In the early formation of training groups within regiment or battery in order that each man may receive instruction and drill according to his ability to profit thereby;

Jan 2, 1919

By A. W. Schlechten, Ernest J. Breton Jr.

Experiments on the separation of copper and zinc ions by selective action of ion exchange resins showed the carboxylic type to be more effective than the sulphonic resins. The latter demonstrated a greater capacity over a wider pH range. Data show the effectiveness of resins as a means of concentration. IN recent years the restrictions of stream pollution laws and the high price of metals have created an interest in ion exchange as a means for metal recovery. Some applications have proved successful. In Germany during World War 11, 17 tons of copper per day were recovered from rayon mill wastes by means of ion exchange resins;' and for some time in this country a large ion exchange unit has been in operation for the recovery of copper from rayon waste water. The possibilities of applying ion exchange to the recovery of metals occurring in plating rinse water is particularly promising. In most of these applications only the metal being recovered occurs in the waste. The ion exchange resins act merely as a means of concentrating the metals to a point where they can be recirculated. It would be highly desirable to use ion exchange as a means of not only concentrating but also of separating metals. With the exception of the impressive separations accomplished in connection with the atomic energy program, very little has been done on metal separations.' Therefore, an investigation was undertaken at the Missouri School of Mines and Metallurgy to determine if either of the two main types of ion exchange resins could be used to separate metal ions in solution. The selective removal of copper ions from a mixture of copper and zinc on carboxylic and sulphonic-type resins was investigated as a function of flow rate, pH, copper-zinc ratio, and concentration. It was shown that zinc can be separated from copper and that very large ratios of concentration can be obtained using ion exchange resins. Since ion exchange is relatively new to the field of metallurgy, a brief review of the subject will be included. Theory of Ion Exchange A comprehensive theory for ion exchange has not been developed as yet, but the mechanisms are analogous to metathetical reactions: R Na + Cu++ *=? K(SO3)2 Cu + 2Na+ R is the designation for the ion exchange resin. If a copper solution is passed over a resin bed in the sodium form, two ions of sodium will be released for every ion of copper removed. For the most part this reaction follows the laws of mass action and of electrical neutrality. Consequently, if an excess of sodium ions is passed over a bed containing copper, the reactions will be reversed, and the resin will be regenerated to its original form. A few empirical rules governing the exchange reaction have been set forth: 1—In general ions with a high valence will replace ions with a lower valence. 2—Ions having higher activity coefficients have a higher replacement potential. 3—In a series of mono-valent ions, those with the smallest radii of hydra-tion will tend to replace those having larger radii of hydration. 4—Where ions are similar in most respects, those with the higher atomic weight sometimes will take precedence. This last rule is not as definite as some of the others. These rules apply to rather dilute solutions at moderate temperatures and assume all ions to be present in about equal concentrations. Higher concentrations and temperatures may in some cases reverse the normal exchange reactions. Ion exchange materials are unique in that their efficiency increases as the concentration of the solution decreases. For many exchangers, most efficient operation is obtained at concentrations in the order of one thousandths of a percent. Most applications, though, are made in solutions containing considerably higher concentrations than this. Coste9 as shown that ion exchange resins will remove aluminum and iron effectively' from solutions of up to 10 pct chromic acid. Ion Exchange Resins Ion exchange resins are insoluble, porous, resinous structures to which active groups have been attached. Active groups such as (—SO,,)- and (COO)- pick up cations; hence structures saturated with groups such as these are called cation exchangers. Structures saturated with groups such as (—NH,)' which pick up anions, are referred to as anion exchangers. The resinous structure of necessity is resistant to strong acids, bases, oxidizing, and reducing agents, and most of the common organic solvents. An idea of the stability can be gaged from the fact that resins last for many years under constant use without detectable chemical or physical breakdown. The ion exchange reaction is not confined to the surface of these synthetic resins. Its porous structure permits active groups in the center of a particle as well as those on the surface to remove ions. A high capacity resin such as Amberlite IR-120 will remove up to 3.3 lb Cu per cu ft of resin. In this investigation several approaches to the problem of separating copper from zinc by ion exchange were considered. First, if a reagent could be found which would complex one of these metals and not the other, then by passing this reagent through a bed of exchanger containing copper and zinc, the

Jan 1, 1952

By John W. Cabot

THE following series of analyses, which may, be of interest to Bessemer-steel makers, is submitted as a contribution to the much-vexed discussion of manganese in Bessemer steel. They were made by the writer in the spring of 1881, at the works of the Pittsburgh Bessemer Steel Company Limited, during a period of about eight days, part of, which time the rail-steel showed great variation in rolling qualities. During the first part of the time in question, it rolled well; later on it began to roll worse until, finally, it cracked very badly, reaching its worst stage. After this it rapidly improved until it again rolled smoothly. During this .time of transition 'from. good rolling to bad, and back to good again, the course of the manganese was followed' quite closely. It is the striking correspondence between these varying manganese contents and the differences in rolling which is here presented as worthy of notice. The other ordinary elements were determined occasionally, but showed no unusual variation Tim steel, in question, was ordinary rail-steel of about "the following composition : C=.35.P=.08.Mn=.98. Si=.08. S=.05. The samples for manganese determinations were taken at first from an average of two days' work, and later on, when the steel

Jan 1, 1882

MIXED emotions were produced by the announcement that the buildup of weapons will be stretched out till mid-1954 instead of the previous 1953 deadline. Reason: government assistance programs will be tougher to get but there will be easement in materials allocations. Earlier in February, DPA had announced that tightening up on regulations governing rapid tax -amortization would become effective March 1. In the future, DPA will have to certify amortization contracts for all construction and permanent installations costing more than $100,000. This action was necessary according to DPA's James F. King, so that new industrial expansions already approved could be assessed in the light of the changing critical mineral picture. When DMPA inherited the backlog of government assistance, requests from DMA, it moved in fast. The results of DMPA's work is described in the article on p. 351 by James K. Richardson; The speed with which these requests were approved and the lengthening of the military program have made a reappraisal of the critical mineral list necessary. It looks as though the consumer industries will be getting more metal soon and, led by steel, there is an industry push toward the abandonment of CMP. Relaxing of materials controls appears imminent but discontinuing CMP is in the "let's talk this thing over" stage.

Jan 1, 1952

By Gifford White

CONSIDERABLE attention has been directed in recent years to methods of electric prospecting other than the conventional direct-current tech-niques. It has been extensively recognized that electrical data of a more general nature than that possible by direct-current methods might be useful in geophysical studies. To this end, a number of different types of electric currents have been employed, such as single-frequency alter-nating currents, square-topped periodic current waves,4 periodic surges of a less specific nature,8 and suddenly applied direct current.1,2 Yet, to the author's knowledge, little analysis of these different types of driving currents has been made from the standpoint of network theory to determine just what type of currents would give the most useful data, and, most important of all, to determine the relation of the data taken by one method to those of another. Without touching on the actual theoretical problem of how currents flow in the earth under specified boundary conditions, some very useful information can be obtained from the study of the fundamental integral equations of electrical networks, throwing light on the problem not ordinarily appreciated by the field worker. Some manipulation of the standard network equations will be made, with the sole purpose in mind of developing expressions leading to practical results. Suppose that four points in the earth have been located and it is wished to obtain the most useful type of electrical data by inserting current into two of them and measuring the potential developed between the other two. The first problem that arises is that of which pair of the four shall be chosen as current grounds. In the direct-current case, where only steady potentials are measured, the selection is of little consequence, but as soon as currents varying with time are used at the current grounds, a new effect arises. The fact that a varying current is flowing in the current-carrying conductor between the current grounds means that magnetic and electric fields varying with time will be produced

Jan 1, 1940

By Chester Washburne

COLOMBIA has an almost ideal situation with respect to the world's markets, being only a short distance from the Panama canal and the West Indies. The sailing distance from its Caribbean ports to New York is less than that from Tampico. Geographically, Colombia consists of three systems of broad mountain ranges separated by two long narrow valleys. The Cauca River valley separates the Western or Coastal range from the Central range. On the west side of the Coastal range are the Atrato and San Juan Rivers. The Central and Eastern ranges are separated by the Magdalena River valley. In the department of Santander the Eastern range divides, one branch continuing northward as the Cordillera of Perija, the other turning eastward across Venezuela as the Cordillera of Merida. Between these ranges is the great basin occupied by Lake Maracaibo. These valleys consist mainly of long narrow reëntrants or tongues of Tertiary sediments between the older rocks of the mountain ranges. The late Miocene and younger sediments seem to have been deposited in separated basins, but the Cretaceous and possibly some earlier Tertiary strata were laid down more or less continuously over a great part of .Colombia and Venezuela. These strata were subsequently folded into the present ranges. The deposition of the Cretaceous and of some of the Tertiary was in a great sea, the main land mass being in Brazil, with land probably along some of the cores of the present mountain systems. The sediments, except the Lower Cretaceous, vary markedly in character and thickness. An illustration is seen in the massive series of non-marine conglomerates and sandstones of the upper Magdalena River valley, near Honda, which are almost wholly wanting in the coastal sections where marine sediments prevail. The oldest rocks bearing on the search for oil are the black carbonaceous and bituminous shales, limestones, and cherts of the upper part of the Lower Cretaceous. These probably are the main source of oil in both Colombia and Venezuela. They include thick bodies of true "oil shale. Above the carbonaceous and bituminous beds, lies a series of many thousand feet of clastic sediments. The most noticeable and easily recognizable formation among these clastic sediments is the "coal-bearing series," which may be either upper Cretaceous or Eocene. The

Jan 6, 1922

By D. E. Norquist, J. E. Moeller

The results of wear on marked balls, 4, 31/2, 3, and 2 in. diam are given. All balls were forged steel of practically the same chemical analysis and hardness. The results indicate that balls in a given mill for a given length of time will have equal diameter losses, regardless of size.

Jan 1, 1950

By E. P. Chapman

In May 1957 a diamond drill hole intersected 40 ft of magnetite and chalcopyrite assaying 2.55% copper and 51.6% iron on the claims of Craigmont Mines Ltd. near Merritt, southern British Columbia. The subsequent drilling indicated the presence of a multi-million ton orebody averaging over 2% copper and 18% iron, the latter present for the most part as magnetite and specular hematite in approximately equal proportions. This orebody, although under shallow cover at its eastern extremity, did not come to the surface and the early drilling was done on the basis of strong coinciding magnetic and geochemical anomalies. After 4 ½ years of intensive exploration and development the property was put into production in September 1961. The new ultramodern concentrator has a design capacity of 4000 tpd but is consistently treating well over this amount. Production is currently coming from that portion of the deposit which is amenable to open-pit mining methods. By mid-1958 information regarding the importance of the Craigmont find became fairly wide- spread, and exploration in the Merritt area was greatly intensified. Numerous magnetic and geochemical anomalies have been tested by drilling with notable lack of success. Detailed geological studies of the deposit and of the area have been made by Government agencies and by private companies and such studies are continuing. Many types of geophysical methods have been employed over the Craigmont deposit in an effort to develop knowledge which would assist in the search for similar mineral concentrations in the environment in which it occurs. This paper will discuss the results of the various geophysical surveys in relation to geological conditions and ore outlines insofar as they are now known.

Jan 7, 1962

By Gifford White

Considerable attention has been directed in recent years to methods of electric prospecting other than the conventional direct-current techniques. It has been extensively recognized that electrical data of a more general nature than that possible by direct-current methods might be useful in geophysical studies. To this end, a number of different types of electric currents have been employed, such as single-frequency alternating currents, square-topped periodic current waves,4 periodic surges of a less specific nature,s and suddenly applied direct current.1,2 Yet, to the author's knowledge, little analysis of these different types of driving currents has been made from the standpoint of network theory to determine just what typc of currents would give the most useful data, and, most important of all, to determine the relation of the data taken by one method to those of another. Without touching on the actual theoretical problem of how currents flow in the earth under specified boundary conditions, some very useful information can be obtained from the study of the fundamental integral equations of electrical networks, throwing light on the problem not ordinarily appreciated by the field worker. Some manipulation of the standard network equations will be made, with the sole purpose in mind of developing expressions leading to practical results. Suppose that four points in the earth have been located and it is wished to obtain the most useful type of electrical data by inserting current into two of them and measuring the potential developed between the other two. The first problem that arises is that of which pair of the four shall be chosen as current grounds. In the direct-current case, where only steady potentials are measured, the selection is of little consequence, but as soon as currents varying with time are used at the current grounds, a new effeet arises. The fact that a varying current is flowing in the current-carrying conductor between the current grounds means that magnetic and electric fields varying with time will be produced

Jan 1, 1940

By Gifford White

Considerable attention has been directed in recent years to methods of electric prospecting other than the conventional direct-current techniques. It has been extensively recognized that electrical data of a more general nature than that possible by direct-current methods might be useful in geophysical studies. To this end, a number of different types of electric currents have been employed, such as single-frequency alternating currents, square-topped periodic current waves,4 periodic surges of a less specific nature,s and suddenly applied direct current.1,2 Yet, to the author's knowledge, little analysis of these different types of driving currents has been made from the standpoint of network theory to determine just what typc of currents would give the most useful data, and, most important of all, to determine the relation of the data taken by one method to those of another. Without touching on the actual theoretical problem of how currents flow in the earth under specified boundary conditions, some very useful information can be obtained from the study of the fundamental integral equations of electrical networks, throwing light on the problem not ordinarily appreciated by the field worker. Some manipulation of the standard network equations will be made, with the sole purpose in mind of developing expressions leading to practical results. Suppose that four points in the earth have been located and it is wished to obtain the most useful type of electrical data by inserting current into two of them and measuring the potential developed between the other two. The first problem that arises is that of which pair of the four shall be chosen as current grounds. In the direct-current case, where only steady potentials are measured, the selection is of little consequence, but as soon as currents varying with time are used at the current grounds, a new effeet arises. The fact that a varying current is flowing in the current-carrying conductor between the current grounds means that magnetic and electric fields varying with time will be produced

Jan 1, 1940

By R. H. Sayre

.... The subject is one of great interest in every point of view to railroad managers and steel-rail makers. It has occurred to me that if in this connection your society would take up the matter of the shape or section of steel rails and the form of joint, and be able to arrive at such form for difEerent weight of rails as you could recommend to the railroa~ls of tbis country with a view of obtaining uniformity, it would be, in caseof adoption, of great value both to the railroads and makers of wils. My idea is that if botb your society and that of the civil engineers ahould join in the adoption of templates and their recoalmendation, it would be more likely tb have the desired effect. Youm truly, Robert H. Sayre..

Jan 1, 1881

By J. M. GARZA

The production of oil in Mexico during 1945 was 43,402,852 bbl., or a daily average of 118,912 bbl. In March 1938 most of the oil properties were taken over by the Mexican Government and since then have been operated by Petroleos Mexicanos, an agency of the Government. The variations in the production during the last 8 years have been due to- fluctuations in the export market demand for Mexican oil rather than to the productive capacity of the fields. Since 1937, yearly production, to the nearest hundred thousand barrels, has been as follows :

Jan 1, 1946