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By W. A. Bruce

This paper covers the theory and present state of development of an apparatus for the nonmathematical analysis of complex problems of reservoir and well behavior. At the present stage of development of this apparatus, it is capable of solving the water-drive problem of any reservoir performance for which a mathematical solution has been presented in the literature, either on the basis of steady or unsteady-state flow analysis. The theory is presented for the extension of the scope of this analyzer along the lines of the present development. The resulting apparatus should be able to solve reservoir-performance problems previously thought too difficult for practical solution by mathematical means. As an illustration of its operation and present scope, the analysis of a reservoir problem and synthesis of expected performance is presented. Introduction In this method† of analyzing problems of petroleum-reservoir and well behavior, the porous continuum of the reservoir is assumed to be divided into small blocks, or units. Each block is assumed to be small enough so that for a material balance on the fluids in the block an average pressure for the block can be used. In analyzing reservoir behavior from this point of view by mathematical means, a set of simultaneous difference equations would be obtained (two for each block), which must be solved or combined into a partial differential equation. In the method to be described here, instead of solving these sets of equations analytically, electrical units are constructed, which will behave in respect to the flow of electricity exactly as the reservoir units behave under various conditions of fluid flow. The electrical units are then wired together in the same way that the reservoir units are connected naturally by virtue of their geometrical locations and shapes. Fluid-Flow Equations Consider a block in a reservoir. Assume that reservoir fluid (or fluids) is flowing in at one face and out at the opposite face, and that the block is small enough so that at all points the stream lines are within one degree of perpendicular to the face. Furthermore, assume that the pressure, pi, at the upstream face (Fig, I) is not more than one per cent greater than P2 the pressure at the downstream face. A material balance will show that the mass of fluid flowing out less the mass of fluid flowing in will equal the change in density times the fluid volume. This is expressed in the equation:

Jan 1, 1943

ALABAMA Aldrich -Thomas, D A Altoona -Cain, J Anmston-Cowie, L K Walmsley, W N White, H E Bankhead -Terentieff, V E Bessemer -Abbott, C E Ball, E M McKenzie, W C, Jr Mitchell, F R Morgan, C Thompson, N E Birmingham -Adams, J H Adler, J E Aldrich, T H Aldrich, T H , Jr

Jan 1, 1923

By M. Van Weyenbergh, G. Van Esbroeck

THE copper mines of the Katanga region in the Belgian Congo lie along the same mineralized belt as those of Northern Rhodesia. There are two distinct types of deposits in that belt, the dolomitic and the quartzitic. In the dolomitic type the metallic minerals are found in a dolomitic limestone country rock. Through oxidation and enrichment,, large deposits of high-grade oxidized copper ores were formed, some of which are being worked by the Union Miniére du Haut Katanga. Such deposits are all in Katanga. The quartzitic deposits are found in Katanga and Northern Rhodesia. Here the primary mineralization occurred in sandstones and quartzites, in horizons stratigraphically lower than the dolomites. These rocks are not favorable to secondary enrichment and the oxidized zone is poorer than the sulphide zone, which alone contains the ore. There are also in Katanga a few ore-bearing veins. One of them is being worked in the Prince Leopold mine at Kipushi. PRINCE LEOPOLD MINE The Kipushi ore body fills a fault vein and invades the wall rocks more or less extensively by metasomatic replacement. The vein strikes north-northeast and south-southwest and dips to the west. The variable dip averages 60ºto a depth of 300 ft., and more uniformly 80º below 400 ft. In the upper section the average width is 200 ft. and below the width is about 150 ft. The length of the ore body is 2300 feet. The eastern side of the vein-the footwall-is dolomitic and contains irregular masses of ore sometimes extending 100 ft. or more from the main

Jan 1, 1939

Jan 1, 1892

By S. D. Dahlgren

The plasticity of unalloyed P plutonium was studied by evaluating the strain-rate-hardening exponent, m, in the equation Values of m up to 0.33 and tensile elongations up to 680 pct were obtained for ß plutonium formed directly from the a phase. Casl bars that were cycled and tested had lower flow stresses and higher values for than uncycled bars , hut their total plastic elongations were not as great as expected because of premature failure at voids formed during cycling. Flow stresses were higher and m was lower (m = 0.15) for 9 plutonzutn formed from the y phase. ThE strain-rate-hardening exponent for plastic flow of p plutonium was determined as a function of strain rate, test temperature, and heat-treating history, and it was related to the rather large plastic elongation found previously for some plutonium tensile samples. Gardner and ~ann' obtained tensile elongations of up to 620 pct for P plutonium samples which had been completely transformed from the low-temperature a phase to the P phase before testing. Such a large percentage elongation is unusual for unalloyed metals or single-phase alloys.' The a phase is stable below approximately 112°C and (3 is stable between approximately 112" and 190"c.~ Both phases have mono-clinic structures. A temperature of 160°C is 0.58 of the effective absolute melting point, 475°C) of the p phase. The effective melting point is obtained by considering the enthalpy and entropy changes associated with the higher-temperature phase transformations and it is not the same as the experimental melting point of the highest-temperature allotrope of unalloyed plutonium. Nelson, Bowman, and Bierlein observed a striking difference between the ductility, as well as other mechanical properties, of p plutonium formed from the next higher-temperature phase (y) and the ductility of /3 plutonium formed from the a phase. The total elongation of /3 plutonium formed from the y phase was less than 5 pct. Earlier, the creep rate of 13 plutonium formed from the a phase was shown to be 200 to 500 times faster than the rate for 0 formed from y for the same test temperature and stress.

Jan 1, 1969

By R. A. Flinn, John T. Norton

A considerable number of experiments in recent years have definitely established the fact that the internal friction or mechanical hysteresis of a metal under cyclic stress is a property that is highly "structure sensitive." Because of this fact, it has been suggested that an observation of this property, which often is referred to as "damping capacity,'' might be a useful indicator of structural changes taking place when a metal or alloy is subjected to any of a number of metallurgical treatments. Damping capacity is of interest to both engineer and metallurgist, but from a rather different point of view, and the information that each desires from such observations is of a different nature. The metallurgist is in search of various external indications of changes taking place in the interior of a metal; changes which are in themselves not directly observable. Even if the observed phenomenon cannot be explained in fundamental terms, it may be empirically related to certain characteristics of the material and prove of real value in research. Internal friction or mechanical hysteresis occupies such a position, and, although it is not well understood in terms of basic metallic theory, an observation of its changes can serve in a very useful capacity. Of course, there is nothing new in the measurement of damping, but the use of this property in metallurgical research constitutes a vast field, which has received all too little attention. The present work is essentially of an exploratory nature in this field and is an attempt to evaluate the process as a research tool. The phenomenon of age-hardening was chosen as a typical example of a structural change and one method of measuring damping was examined in considerable detail. Methods of Measuring Damping Capacity Many kinds of observations can be made upon a specimen subjected to a cyclic stress from which can be calculated the energy absorbed in

Jan 1, 1938

By R. A. Flinn, John T. Norton

A considerable number of experiments in recent years have definitely established the fact that the internal friction or mechanical hysteresis of a metal under cyclic stress is a property that is highly "structure sensitive." Because of this fact, it has been suggested that an observation of this property, which often is referred to as "damping capacity,'' might be a useful indicator of structural changes taking place when a metal or alloy is subjected to any of a number of metallurgical treatments. Damping capacity is of interest to both engineer and metallurgist, but from a rather different point of view, and the information that each desires from such observations is of a different nature. The metallurgist is in search of various external indications of changes taking place in the interior of a metal; changes which are in themselves not directly observable. Even if the observed phenomenon cannot be explained in fundamental terms, it may be empirically related to certain characteristics of the material and prove of real value in research. Internal friction or mechanical hysteresis occupies such a position, and, although it is not well understood in terms of basic metallic theory, an observation of its changes can serve in a very useful capacity. Of course, there is nothing new in the measurement of damping, but the use of this property in metallurgical research constitutes a vast field, which has received all too little attention. The present work is essentially of an exploratory nature in this field and is an attempt to evaluate the process as a research tool. The phenomenon of age-hardening was chosen as a typical example of a structural change and one method of measuring damping was examined in considerable detail. Methods of Measuring Damping Capacity Many kinds of observations can be made upon a specimen subjected to a cyclic stress from which can be calculated the energy absorbed in

Jan 1, 1938

By Harrison Schmitt

During the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. Hanover, New Mexico The Hanover, New Mexico, zinc deposits were briefly described by Lindgren and others,' Paige2 and recently in more detail by Schmitt. These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive ¾ mile wide and 2 miles long (Fig. I). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike, thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1935

By Harrison Schmitt

During the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. Hanover, New Mexico The Hanover, New Mexico, zinc deposits were briefly described by Lindgren and others,' Paige2 and recently in more detail by Schmitt. These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive ¾ mile wide and 2 miles long (Fig. I). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike, thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1935

During the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. Hanover, New Mexico The Hanover, New Mexico, zinc deposits were briefly described by Lindgren and others,' Paige2 and recently in more detail by Schmitt. These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive ¾ mile wide and 2 miles long (Fig. I). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike, thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1935

During the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. Hanover, New Mexico The Hanover, New Mexico, zinc deposits were briefly described by Lindgren and others,' Paige2 and recently in more detail by Schmitt. These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive ¾ mile wide and 2 miles long (Fig. I). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike, thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1935

By Harrison Schmitt

During the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. Hanover, New Mexico The Hanover, New Mexico, zinc deposits were briefly described by Lindgren and others,' Paige2 and recently in more detail by Schmitt. These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive ¾ mile wide and 2 miles long (Fig. I). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike, thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1935

By Lawrence Addicks

AT the San Francisco meeting of the Institute last year, I presented, through the courtesy of Dr. James Douglas; some results of experiments on the roasting and leaching of concentrator tailings. After it became apparent that flotation rather than leaching was clearly the better method of handling the particular problem under consideration, before dismantling the experimental equipment, some data were secured on roasting and leaching the concentrate itself in competition with smelting. Some of the results obtained are given in the following paper and they a re of particular interest at this time in. view of the large quantities of flotation concentrates with their somewhat difficult smelting characteristics now being produced. A complete wet process? consists of roasting and leaching the calcines in dilute sulphuric acid produced from the roaster gases, roasting the residue with salt and leaching with dilute tower liquors (the well-known Longmaid-Henderson process) and recovering the copper, silver and gold by cementation or electrolysis or a combination of both. It is evident, however, that the residue from the first leaching, carrying about 20 per cent. of the copper and all of the silver and gold, can be smelted if preferable. In considering the application of the scheme to individual cases, it must be remembered that freight plays a. large part in any reduction process wherein smelting is not conducted at the, mouth of the mine, and that it is not practicable today to build small smelting plants for individual operations. The experiments may be grouped under four main heads: Roasting, leaching, chloridizing residue, and recovery of copper from solutions. The products of two concentrators were used: The Nacozari concentrates were the product of a large modern mill not using flotation, the copper mineral being largely chalcopyrite; and the Tyrone concentrates, the product of an experimental mill including flotation, the copper mineral being chiefly chalcocite. Typical analyses would be as follows:

Jan 9, 1916

By F. V. Lenel, J. A. Dromsky

The influence of thermal and mechanical treatments upon the elevated-temperature stability, the microstructure, and the mechanical properties of aluminumaluminum oxide alloys is investigated. Compacts from atomized and flake aluminum powders were sintered at temperatures just below the melting point of aluminum in a vacuum of 10-4 Torr for several hours and were then hot-extruded. During this treatment the hydrated oxide present on the surface of the powder particles decomposes, the water vapor produced reacts with the aluminum forming additional oxide, and the hydrogen developed is removed by diffusion to the surface. Extrusions of compacts so treated are stable at temperatures up to the melting point of aluminum and do not form blisters and internal defects typical of extrusions from untreated powder. Electron micrographs of extrusions from unsintered compacts show long parallel oriented platelets typical of the IN previous investigations1,2 the properties and structure of aluminum alloys were described which had been produced by cold compacting aluminum powder and then hot pressing and extruding the compacts. Both the structure and the properties of these alloys differ significantly from those of commercially produced aluminum-aluminum oxide alloys. When commercial alloys are produced, they are given a sintering treatment in air at about 600°C between cold compacting and hot pressing.3 During this treatment the hydrated oxide, which forms the coating on the aluminum-powder particles from which the alloys are prepared, is decomposed.4 The chemically bound water which is released reacts with the aluminum and forms aluminum oxide and hydrogen. Most of the hydrogen is eliminated by hydrated oxide skins on the original powder particles, while the oxide particles in extrusions from sintered compacts are broken up. The strength of extrusions from treated powder is somewhat lower, but their ductility is considerably improved over that of extrusions from untreated powder. The slip-trace patterns on electron microgvaphs of extrusions which had been strained in tension before replication indicated that the grain size of the extruded alloys was approximately the same as that of the original powder particles. Coarse-grained alloys were produced by severe cold work and annealing of the extrusions. They have significantly lower room-temperature strength, but about the same ductility as the vacuum-sintered fine-grained alloys. The size and shape of oxides in the coarsegrained alloys is similar to those of the fine-grained alloys, but the particles are somewhat more uniformly distributed. diffusing to the interior or exterior surfaces of the compact, but it is difficult to eliminate all of it because the solubility of hydrogen in solid aluminum is very low even near its melting point. Extruded alloys which are not sintered before hot pressing and extrusion appear quite sound upon metallo-graphic examination, but develop severe surface blistering and internal fissuring when they are heated to elevated temperatures after extrusion. Fissures and blisters have been observed even in commercial alloys which had been sintered in air, although they are much less severe.' Because of the importance of this sintering treatment it was studied in this investigation in a modified form, using vacuum sintering rather than sintering in air, to insure more complete elimination of occluded hydrogen. The technique is described and the effect of the treatment upon the structure of the alloys is documented. It has been known for some time that extruded aluminum-aluminum oxide alloys are very finegrained, but an exact delineation of grains in electron micrographs has not been possible. In the conventional metallographic-etching techniques etchants attack the interface between the second-phase particles and the matrix in the alloys much

Jan 1, 1964

By J. E. Spurr

The region here discussed is that part of Western Nevada in which. during the last few years. discoveries of rich gold- and

Jan 1, 1906

By Charles R. Keyes

In the dry regions of the globe many silver-deposits display certain remarkable features, which at the same time are so totally unlike anything met with among ore-bodies elsewhere that they hare long presented exceptional dificulties, not only to a satisfactory explanation of their origin, but to economical milling. A most striking peculiarity of these ores is the haloid character of many of their bonanzas. To this fact more than to any other may be ascribed most of the unusual uncertainties of mining-operations in desert countries—the marvelous local richness of the ores under certain conditions and the often abrupt transition to utter poverty; the inadequacy of ordinary prospecting customs and the constant devising of new exploratory methods; the unaccountable losses in smelting and the continual change in treatment-practice. For these anomalies certain climatic conditions seem to be chiefly responsible.

Jan 1, 1912

By Walter R. Crane

Operators of diamond drills have long been familiar with threadlike markings or riflings on cores but apparently have given but little serious thought to the conditions that are responsible for their production. The opinion generally held by those who have observed the phenomena is that the riflings are produced directly or indirectly by vibration, but so far as the writer is aware no systematic attempt has been made to demonstrate the fact. A careful search through the literature on diamond-drilling practice has been rewarded by only one reference to such markings of cores. J. N. Justice1 writes, "Of the peculiarities met with in the core, I will mention only one. The core from the "H" drill, at about 360 ft. came out rifled and pentagonal. The change from the circular to the pentagonal was sudden, and for 9 ft. this structure was maintained, when suddenly it returned to the circular. I have not been able to find any one who can explain the cause of this change of form. The drill men marveled at it and suggested vibration, six-stone bits, and several other hypotheses which need not be mentioned." The writer became interested in the matter of core riflings some 10 years ago while in the Flat River lead region of Missouri, where many remarkable examples of "rifled" cores were observed and collected. Since that time similar phenomena have been observed in various localities throughout the United States and Canada, and samples have been gotten together illustrating a large number of variations in form. After a careful study had been made of the material at hand it seemed desirable that certain data should be obtained from the experience of others regarding the normal action of diamond drills in forming cores, portions of which are occasionally rifled, before an attempt was made to draw any conclusions as to their cause. About 20 letters were addressed to diamond-drill companies, operators, and engineers actively engaged in drilling operations, with a

Jan 1, 1917

By H. A. Wriedt

A method of calculating activities in binary systems having miscibility gaps is described. The method, which applies only to the phase in which the gap occurs, is exact when the function defined by the equation varies linearly with composition. Analytical and numerical solutions (as a function of the conjugate phase compositions) are presented for two coefficients A and B from which the thermodynamic activities can be calculated. Deviations from Henry's law, calculable by the method presented, are shown graphically for the particula~ case of the component i at the edge of the miscibility gap more remote .from pure component i. For symmetrical gaps, the deviation from Henry's law at this gap edge becomes smaller as the gap becomes wider, The interrelation of gap location, the direction of departures from Henry's law and the occurrence of maxima and minzma in these departures is discussed in some detail. Values for a and for activity calculated from phase diagrams show fair to excellent agreement with corresponding experimental values in the Al-Zn and CaO-SiO2 systems. WHEN structurally similar phases, B and 6, lie at the sides of a two-phase region in a constitution diagram, it can be assumed that, stably or metast-ably, they will become completely miscible at a higher temperature. The B and 6 phases are particular composition ranges of a single B6 phase region with a miscibility gap. Below, as above, the critical solution temperature, the free energy of formation of the 06 phase is a continuous function of composition through the range of the miscibility gap. It is the purpose of this paper to use this continuous free-energy function in order to develop a simple method for computing the thermodynamic activities in the B6 solution of a binary system. To make these calculations it is assumed that the function ai, familiar from Gibbs-Duhem integrations and defined by the equation

Jan 1, 1962

By Turno De Michelis

The Porto Marghera plant was erected in 1936 for the production of 10,000 tons of electrolytic zinc annually. Since then it has been continuously enlarged until annual production of the metal reached 40,000 tons in 1969. At the same time the processing cycle was modified bringing it up to date with modern techniques, and was completed by installations for the recovery of by-products in the minerals treated and subsequent processing of the base metal. 90% of the zinc produced is of 99.993% purity . At present the plant comprises, first of all, the zinc blende desulphuration department which has a single modern fluid bed furnace capable of processing 220 - 250 tons of dry crude mineral daily; it is connected to the sulphuric acid plant with its three catalysis sections each capable of producing 60-70 tons of sul9huri.c acid monohydrate daily. The roasted blende is conveyed pneumatically to plants for leaching of the zinc and purification of the resulting solution. During recent years this department has been completely transformed from the discontinuous cycle, for which it was built, to the continuous cycle, paying great attention to

Jan 1, 1970

By I. N. Knapp

I Herewith present some notes on the use of Portland cement to cement in the casing, and for plugging, to exclude water from oil and gas wells, and the methods employed. I have used my best efforts to. make each step of the operation of cementing wells perfectly clear. The information is the result of actual experience and observation. The illustrations are from original drawings made especially for this paper. Portland Cement It is not necessary to discuss here the manufacture of cement. Any established brand of the slower setting Portland cements may be purchased with the confidence that it will harden, if properly used, and exclude water from and plug wells efficiently. Setting.—By the setting of cement is meant its initial change from a soft or plastic mortar to a friable solid. After the cement has become thoroughly set it is still very weak and can be readily pulverized in the fingers. Setting is thought to be effected by the crystallizing out of the silicate and the aluminate of lime, which are soluble in water in their anhydrous form. After dissolving in the water they pass to the hydrated state, in which they are insoluble, and hence are precipitated in a crystalline form. Ordinarily neat Portland cement mortar remains perfectly plastic for from 1 to 1 1/2 hr. after mixing with water at about 70" F. A higher temperature accelerates and a lower retards setting.. Hardening.—This is due to a continual crystallization of salts from solution, and to further chemical and physical changes which develop slowly, but which continue for long periods of time. Testing.—It is no more necessary for an operator to go into the scientific testing of cement to be used in a well than to so test the pipe used. He must depend for the quality of each on the tests and reliability of the manufacturer. Cement or pipe may be damaged in shipment so

Jan 1, 1915