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By V. H. Gottschalk, R. S. Dean

In the theoretical study of metallurgical reactions, it is necessary to make certain assumptions concerning the nature of metal-gas systems. The assumption usually made is that the reaction in such systems takes place predominantly with gas that is in "solution" and that the amount of solution follows the rules which have been developed for aqueous solutions; namely, Henry's law. The purpose of this paper is to inquire whether these assumptions are the best ones that present knowledge of gas-metal systems permits us to make. In the first part the extent to which a gas will dissolve in a metal and still follow Henry's law is considered. The conclusion is believed justified that the number of molecules of gas that can dissolve in a metal and have the system follow Henry's law must be small indeed. It is therefore improbable that the first assumption concerning the predominance of these dissolved molecules in reaction is correct. It is suggested that some improvement in the correlation of the probabilities with the assumptions made in the mass law equations would be made by the use of the dp law of Sieverts in place of Henry's law. However, the amount of gas that may be held in a metal so that it follows either Henry's or Sieverts' law is considerably outweighed in most metallurgical reactions by that held in gas-metal systems of entirely different structures and concerning which little experimental evidence is available. Some speculation concerning the nature of these is offered. The conclusion is that attention should be given to the determining of the nature of gas-metal systems and that the really fruitful application of the mass law and its connected calculations will have to await a more complete knowledge of these systems than we now possess. DISCUSSION (Paul D. Merica presiding) P. D. Merica, New York, N. Y. (written discussion).—The solubility relations of gases in metals, in so far as they are known from the pioneer work of Sieverts and others, have from the first presented certain challenging peculiarities. The authors have emphasized the significance of these characteristics and suggest that they point

Jan 1, 1933

By E. P. Pfleide, L. W. Gibbs. J. R. Gross

A method using computer techniques is described for the comparative evaluation of truck performance over any given haul road using readily obtainable manufacturers' data. An additional computer program is utilized to calculate individual cycle times for each truck and shovel combination, fleet requirements for any desired production rate, and to estimate comparative costs. The introduction of a large number of variables into the program permits management to determine the critical system factors having the greatest bearing on costs. Thus, the method described can be used not only for analysis of needs for a new surface mine but for cost improvement in existing mines where changes in truck and shovel operations are contemplated. The systems analysis approach to the solution of problems in the mining industry is gaining in industry acceptance. This is a logical development in view of the fact that a mine constitutes one of the most dynamic systems of production. In contrast with a manufacturing plant, situated in a location selected through choice and utilizing a regulated source of quality controlled raw materials, the miner must go where the ore is and he is faced with ever changing physical conditions. He is subjected to the vagaries of nature, and he can never mine the same ore twice. What is systems engineering? There seems to be no concise and universally accepted definition of the term and its meaning is still fairly local. It deals largely with trade-offs of subsystem characteristics to achieve some desired result in an overall system. This concept of suboptimization can be explained by an example. If the objective of a mining company is to produce a certain quality ore at minimum cost, the optimum operation is not achieved by minimizing all costs, since all phases of mining are interrelated. Reduction of blasting costs might well increase loading, hauling, and crushing costs out of proportion to the resulting saving in explosives. Hence tradeoffs are necessary. It is evident then that an optimum system is achieved through a blending of suboptimal components which taken together yield the desired result. OBJECTIVE For our mathematical model we will assume the existence of a hypothetical new organization called Taconite Mining Co. (TMC). TMC has made an analysis of their orebody, their proposed operation, and

Jan 1, 1968

By Thomas F. Downing

When examining a coal property it is customary for the engineer to take channel samples at several coal faces. In doing so the extraneous matter, or partings, which can be removed by hand, or mechanically, with the facilities at hand, or proposed, is rejected. Where there is doubt concerning a stratum it is usually rejected from the main sample but part is taken for separate analysis. The samples are forwarded to a chemist for proximate analyses and determination of British thermal units, and, sometimes, ash fusion. Consideration is given all available commercial analyses but frequently the owner presents only the favorable ones. From the results thus obtained a general evaluation is made, monies are loaned or expended, markets are determined, and realization is estimated. In many instances, such grades are not substantiated and it is time we looked deeper for a basis which will prove more practical. Institute committees are working hard on analytic and use classifications and much valuable information has already been assembled and distributed. However, no single grade can be applied to any particular bed or region. Much study has been given the Pittsburgh No. 8 seam, yet that bed is subject to material differences in a single section;i. e., some strata of a face may differ from others in structure and analysis, particularly in sulfur content. From some localities it yields a good carbonization fuel, while in others it is chemically unfit for such use. Traveling south to the Logan, W. Va., field we find the Cedar Grove (Island Creek) seam a hard, gray splint coal., In the same field, and not far distant, the same bed changes, both structurally and chemically, and consists of excellent gas coal. In Illinois the moisture content of a bed may vary greatly in different localities. We have seen mines in which part of the coal is excellent for special purpose use but is spoiled by the product from another part of the same mine. Many other illustrations could be given but these are sufficient to show that application of any grading of coal must be distinctly local. The actual designation of grade can be given only after detail study of the component parts of the seam, or seams, on the property under considera-

Jan 1, 1932

By R. Rocca, M. B. Bever

THE adiabatic elastic deformation of a body is accompanied by a change in temperature. This phenomenon is known as the thermoelastic effect. Under adiabatic conditions the temperature of a metal bar is decreased by an elastic elongation and is increased by an elastic compression. All materials which elongate on heating behave in this manner. The sign of the thermoelastic temperature change is reversed for the few materials which have a negative coefficient of thermal expansion. The following equation for the thermoelastic effect can be derived from fundamental thermody-namic theorems, as shown in the Appendix: dT8 =-a1/cs T dss [1] Cs In this equation, T is the absolute temperature, S is the entropy, a, is the coefficient of linear thermal expansion, cs' is the heat capacity per unit volume at constant stress and s is the stress (positive in tension). Eq 1 can be applied to small, but finite changes in stress in the following form: ?Ts =- a1/cs T?ss [2] The sign of the temperature change AT is opposite to that of the change in stress s for materials which have a positive coefficient of thermal expansion. Eq 2 has been verified for many different materials and stresses at room temperature. No previous publication appears to have been devoted to an in- vestigation of the thermoelastic effect over a range of temperatures. Review of Literature Lord Kelvin (W. Thomson) presented a general theory of the thermoelastic effect in 1851' and later applied it to a solid, subject to an arbitrary system of stresses'. His analysis was based on a cycle of isothermal and constant-strain transformations and led to Eq 2 above. Even today, one of the clearest expositions of the thermoelastic effect is found in Lord Kelvin's article on elasticity in the Ninth Edition of the Encyclopedia Britannica (1878). R. ROCCA, Junior Member, and M. B. BEVER, Member AIME, are Research Assistant in Metallurgy and Associate Professor of Metallurgy, respectiuely, Massachusetts Institute of Technology, Cambridge, Mass. AIME New York Meeting, Feb. 1950. TP 2760 E. Discussion (2 copies) may be sent to Transactions AIME before APT. 1, 1950, and is scheduled for publication Nov. 1950. Manuscript received Oct. 15, 1949.

Jan 1, 1951

By Joseph Ames

THERE are two distinct questions associated with the concept of temperature: one is practical, the other is theoretical. Our fundamental ideas of temperature come from our senses; we know what we mean by the words "hot" and "cold," or by saying one body is "hotter than another." But for scientific purposes words require definition. We are guided in this matter, as in all other scientific questions, by our knowledge of facts of observation. When two bodies at different temperatures are intimately associated, e.g., a hot stone is, dropped into a pail of water, our experience is that ultimately they come to the smile temperature as far as our senses can tell; the hot body becomes colder and the cold body hotter. In the case of a block of ice, immersed in, water, the ice melts, forming cold water, which then mixes with the other water, the final result being water colder than the original water. From our knowledge of the nature of heat phenomena, we learn that in this process one body loses, heat and the other gains heat, the condition of equilibrium being, one in which each body gains Is much heat as it loses. It is distinctly assumed in this statement that only two bodies are concerned in the transfer of heat, all other bodies being rendered in some way impervious to heat. The body that in the process loses heat is said to have the ?higher temperature" while the body that gains the heat is said to have the "lower temperature;" and, when thermal equilibrium is reached, the two bodies are said to have the "same temperature." Consequently, the temperature of a body may be defined, is it was by Maxwell, as "its thermal state considered with reference to its power of communicating heat to other bodies."

Jan 9, 1919

The notion prevails that writing is a knack, that the skilful use of the pen is a gift of nature. This is an error. Dogberry may be responsible for it; he said: "To be a well-informed man is the gift of fortune, but to write and read comes by nature". Because Dogberry said it, we may be sure that Shakespeare thought otherwise. Ability of any sort may be partly innate, but my own observation and experience lead me to conclude that most of the easy writers have become so by constant practice. As I recall the names of men successful with the pen, I remember that most of them have written a great deal and have taken particular pains to improve their style. The suggestion that proficiency in the difficult art is a happy accident provokes a sardonic smile. The larger part of the great writing in our literature is the result of persistent effort. An easy fluency has been the undoing of many; their flamboyant and fantastic scribbling has proved as perishable as froth. This criticism applies to technical writing also; in order that a technical description or discussion may hold the interest of the reader, at least long enough to cause him to read it to the end, the writing must be done carefully and systematically; otherwise it will fail in its purpose of conveying information. Clearness is absolutely essential. "It is not enough to use language that may be understood; it is necessary to use language that must be understood."* The purpose of writing, at least of that which is meant to be read by others, is not only to express ideas but to communicate them. Lack of perspicuity may prove as bad as

Jan 1, 1931

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 os mechanical hysteresis occupies such a position, and, although it is nor well understood in terms of basic metallic theory, an observation of itt 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.

Jan 1, 1938

By L. C. Reese

The ultimate resistance against a rigid cylinder which is moved laterally in a cohesionless soil is a function of the geometry of the cylinder and the properties of the soil. An approximate method is developed for computing this resistance and is tested against results of laboratory experiments. Satisfactory agreement between the method and experiment was obtained. Not only was the ultimate resistance against the cylinder measured, but measurements were made of the shape of the rupture surfaces. These measurements should allow the development of a more rigorous computation procedure. INTRODUCTION A critical aspect in the design of offshore drilling platforms is assuring the stability of the platform during a hurricane. The large horizontal loads from waves and wind make a severe loading condition. Piles are generally employed as the foundation since they can be effective in resisting both horizontal and vertical loads. Spuds are sometimes used with a mat foundation, where the spuds are designed principally to resist horizontal loads and the mat designed principally to resist vertical loads. The research reported in this paper is related to one aspect of the problem of laterally loaded piles or spuds in sand. The complete solution to the problem of the laterally loaded pile in sand would require the prediction of soil resistance against the pile as a function of pile deflection; only the ultimate resistance against short piles is considered in this paper. A considerable amount of additional research will be necessary in order to obtain a complete solution to the problem of the laterally loaded pile in sand; however, the work reported here should be useful as a guide in the performance of some of the additional research. ULTIMATE LATERAL RESISTANCE AGAINST A LONG FALL IN SAND To aid in the understanding of the theory which is developed for a cylinder, the theory for earth pressure against a wall is reviewed. In Fig. l(a), a long wall of height H is shown embedded in soil. Soil resistance will develop as the wall is deflected, and the soil resistance will increase with deflection until some limiting value is reached. In this discussion, and those following, it is assumed that all points on the wall deflect equal amounts. A possible shape of the real curve which relates soil resistance to deflection is shown by the dashed line in Fig. l(b); however, as a means of simplifying the discussion, an idealized curve (shown by the unbroken lines) is drawn. If such a wall as this were furnishing the horizontal support for an offshore structure, the dashed curve in Fig. 1 would be the information needed in performing a foundation analysis, with the idealized curve possibly being an acceptable substitute. For the idealized curve, the soil resistance is linear with deflection for the early portion of the curve such that

By Prof John E. Church

It is a well-known fact that under similar conditions a ton of pig iron can be made from any ore with less fuel when charcoal is used than when coke or anthracite is employed for heating. The cause of this superiority is entirely undiscovered, and no explanation has yet been offered which has won even temporary acceptance. Such as they are the hypotheses heretofore presented are of two general kinds, and they come from those two divisions of the working force which are so often antagonistic in all professions, the scientific and the practical men. The theory of the scientific men is drawn from the chemical reactions which are known to go on in the furnace, and it is well expressed in a recent paper by Prof. Akerman, of the Stockholm (Sweden) School of Mines. It makes the superiority of charcoal as a fuel in the blast furnace to depend upon its quick and thorough reduction of carbonic acid. This property belongs to charcoal in virtue of its porous structure. Its cells have a diameter of only one twenty-four hundredth of an inch, and one grain of charcoal has been computed to have a surface of two and four-tenths square feet. According to the theory in question, carbonic acid is formed by the first impact of the air upon the fuel; but in charcoal furnaces the acid is immediately reduced to oxide by taking the necessary amount of carbon into combination, and the gas reaches its highest reducing power even in the near vicinity of the tuyeres. Coke, being harder, does not produce so strong a reducing gas in that part of the furnace. Carbonic acid is formed as in the case of charcoal, and remains longer before its reduction to oxide is completed. Anthracite is the

Jan 1, 1879

By Albert F. J. Bordeaux

Discussion of the paper of Albert F. J. Bordeaux (Bi-Monthly Bulletin, No. 23, September, 190S, pp. 629 to 640). A. H. BROMLY, Zihuatanejo, Guerrero, Mexico (communication to the Secretary*) :-The following criticism of what "is offered as a summary which may be found useful by mining engineers," is not dictated by any captious spirit, but in the interest of historical and scientific accuracy. The States of Queretaro and Oaxaca have produced sufficient silver to warrant more extended notice. Referring to Pachuca, State of Hidalgo, the somewhat loose and. inexact statement is made that "the ore-deposit is an andesite, intermixed with quartz-veins, rich from the surface." A better description would be,-the ore-deposits consist of quartz-veins in andesite. It is notable that many of the rich shoots worked in recent days did not come to surface. In consequence, Pachuca, is often quoted by the ill-informed as a camp in which values improve with depth, the truth being that the veins carry shoots, or clavos, some of which were exposed at surface and some not. The name of " electric plow," applied to the mechanical stirrer of recent use, is certainly not to be recommended. The stirrer, or agitator, consists essentially of a traversing gang-plow, operated by power through shafting, drums, and wire-rope. The fact that in certain plants the motive-power used is electricity does not make it an electric plow. Such a name suggests a machine of which the motor is an essential and integral part; which is not so in this case. A lathe in a factory driven by water-power is not called a hydraulic lathe. My experience agrees with Dr. Raymond's note as to azulaque, which in sortie districts is also applied to blue copper carbonate. The El Oro, Esperanza, and Mexico mines should be allocated to the State of Mexico; the Dos Estrellas being in Michoacan, as stated. The El Oro quartz certainly does not appeal to me

May 1, 1909

HAVING demonstrated to you above the practice of bringing silver to its ultimate fineness and perfection, it now remains for me to describe how the two kinds of metals that are found in the smelting product that you made from the ores are to be brought to their end: One is copper and the other lead, and perhaps a third is gold, if per-chance the silver that you refined in the cupeling hearth contained any. It would be almost impossible that it should not contain any, because either a little or a lot is almost always found as an admixed substance not only in silver but in. every one of the other metals as well. But in order to continue in sequence, you must suppose that there is some gold and that, of the two materials you have that I mentioned above and told you to save, one is the matte (calling it according to the usage of Germany, * since I do not know a more exact or better word for describing it to you) and the .other is the litharge that you took from the cupeling hearth. In addition, the hearths themselves are saturated and full of lead. If these things should remain in their present condition they would be useless bodies without any perfection. First, taking one of the three said parts, as a material of greater quantity and also as a thing that needs greater labor, and because, being reduced to the point I have told you with smelting and evaporation, it is nearer to its end, I shall tell you what must be done in order to bring it to pure copper. As I have told you, there are two materials on hand, one of which is the matte and the other the litharge. Each at first sight seems a half-burned thing; one has already been finished metal and the other is to be, but in my opinion the matte is nearer to its end than is the litharge because the latter has been dried by the power of the fire and re-formed from another body. Now leaving aside the discussion of this thing, after the matte has been well evaporated and reduced, it is taken and put on a forge. In front of the tuyère a receptacle is made of stones that neither calcine nor melt, or of coals and powdered clay, in the form of a little cradle that is longer than it is wide and not very deep. Its length should be about one and a half

Jan 1, 1942

By Morgan Walker

ONE of the most serious problems in the produc- tion of natural gas is the removal of water from the wells. As a gas well approaches its period of exhaustion, the removal of water by properly de-signed devices becomes increasingly important. Sev-eral methods are used for dewatering gas wells. If the .gas velocity and pressure are high enough, the water in the well will be carried out by the gas on opening the well to atmospheric pressure and allowing the gas to flow unrestricted except for the resistance of the casing. This method of dewatering a gas well is detri-mental to the producing sand, and very wasteful if used frequently. When the well has declined in production a string of tubing is often run in the well, with a packer set at the top or bottom of the well. If the top of the tubing is opened to atmospheric pressure and the gas is allowed to flow unrestricted as in the above method, the water can be discharged at the top of the well, provided the velocity of the gas is high enough. However, if the water has accumulated in the well until the water pres-sure is equal to or greater than the gas pressure, the ,water cannot be brought to the surface. In dewatering :a gas well by this method the operator sometimes finds -that if the packer is set near the top of the well and -the casing is tight, the water can be blown out when .it is impossible to blow it out with the packer set at the top of the sand. This is largely due to some gas leaking into the tubing through the collars. This method of dewatering gas wells is also wasteful. Water can be pumped out of a gas well with virtually the same equipment, as used for pumping oil, but the method involves installing a separate pump for each well, and difficulties are encountered in attempting to pump water under high gas pressure.

Jan 3, 1927

By Joseph A. Holmes, Henry Kreisinger

At the Mining Experiment Station of the U. S. Geological Survey, in Pittsburg, an investigation of the process of combustion is being carried on in a specially-designed furnace having an unusually long combustion-chamber. This work is conducted by a con~mittee consisti~lg of 11. Kreisinger, mechanical engineer; Dr. J. C. W. Frazer, chemist; and Dr..J. K. Clement, physicist. The problem, essentially one of physical chemistry, is estremely interesting to all who are concerned in the burning of coal or the construction of furnaces. The main object of these experiments is to ascertain the relation between the amount of' the volatile combustible driven from the coal and the combustion-spaces necessary to burn it completely. Our best steam-coals vary from 15 to 45 per cent. in volatile matter and from 40 to 75 per cent. of fixed combtistible. The greater part of the latter is burned on the grate: but the volatile combustible leaves the freshly-charsed coal and must be burned in the combustion-space. If this space is not large enough, the volatile combustible mill leave the furnace only partly burnecl, and the result will be a considerable heat-loss and a smoky stack. Strictly speaking, the factor which determines the completeness of combustion of the volatile matter, after it has been mixed with a certain amount of air, is the length of time the mixture is allowed to remain in the combustion-space; but this length of time depends on the extent of the space itself. Let us suppose, for instance, that, when a given coal is burned at a certain standard rate, the volume of the volatile combustible driven oft' per second is 10 cu. ft. Adding, say, 10 cu. ft. of air, the volume of the resulting burning mixture is increased to 20 cu. ft. If the combustion-space is 30 cu. ft., the burning mixture will stay in it,

Jan 1, 1911

By Carl S. Westerberg

Coal preparation practice and trends follow, among other factors, production trends in any given area. Considering an area the size of a state, some broad predictions may be made after a review of the annual production records. As this paper is concerned with coal cleaning in Utah, data on its production record are pertinent. Table 1 shows the percentage relation of coal production in Utah to the national total as a single figure up to 1935 which includes all recorded production. From 1935 through 1947 these data are presented by years. It is evident from these data that the production of Utah coal is ascending. The reason for this trend is industrial growth in the West resulting in a population shift which accounts for more people than the normal increase would supply together with Utah's relatively fortunate geographical location and its abundance of good-quality coal. Utah is also hopeful of supplying more coal in the future for West Coast power generation.I Utah is not unique among coal-producing states in anticipating greater production in the future. Coal Age states, " . . . it is now evident that a billion-ton yearly production of anthracite and bituminous by 1960 is not impossible." At present it is about 610,000,000 tons, the all-time high in 1947 was approximately 687,803,000 tons. In view of the trend outlined above, obviously more new mines will be required to produce the necessary tonnage. These in turn will require more mechanical cleaning capacity. Whether the required new plants will be built by present operators of mines and mechanical cleaning plants or by others now in the business of producing coal or expecting to enter it is of no consequence in this discussion. The fact is— they will be built.

Jan 1, 1950

By R. A. Pasternak, B. Evans

A dynamic technique for the determination of solubilities of gases in metals has been explored, using the N-Nb system as a test case. An initially clean sample, maintained at constant high temperature, is exposed to the gas at low pressure: the rate of sorp-tion and the corresponding change in sample resistance are measured continuously. A pronounced decrease in the slope of the resistance concentration curve is observed at the terminal solubility. The rate of gas uptake by the sample was determined in an ultrahigh-vacuum flow system equipped with a servo-control which maintains constant pressure in the sample chamber; the system and the technique have been described in detail elsewhere. 1,2 The sample was held at constant temperature during sorption by maintaining approximately constant power input into it; this results in constant temperature, since the emissivity of a metal is independent of moderate concentrations of dissolved gas. The simple electrical circuit used both for heating and for resistance measurement is shown in Fig. 1. The power input into the filament is where R is the filament resistance, RL is an adjustable resistance in series with the filament, and VT is the constant dc potential of the power source. If RL is set equal to R at the beginning of an absorption run, the power input becomes insensitive to subsequent resistance changes; for example, an increase of 20 pct in sample resistance is accompanied by a decrease in power input of less than 0.8 pct; i.e., the

Jan 1, 1967

By T. B. Counselman

THE importance of concentration of iron ores too low in grade to be smelted direct is shown by Table I, showing 1940 ship- [ ] ments from the Lake Superior district. Canadian ores are omitted. [ ] Only in Minnesota is concentrating, other than crushing and screening, practiced at present. Tonnage produced by various methods of concentration is shown in Table 2. The curves in Fig. I show the gradual increase in tonnage of concentrated ores shipped, compared with total shipments from Minnesota. Most of the concentration work is performed on the Mesabi Range. This range is about 100 miles long, and not over 3 miles wide from the line at which the formation tapers out to a feather edge on the north to the place on the south at which, some 600 ft. thick, it is overlain with slates. CLASSES OF ORE The Mesabi Range contains three classes of iron ore. First is the unaltered taconite, or banded iron-bearing chert. It is estimated that there are some 60 billion tons of this material, which contains, roughly, 25 to 30 per cent iron. This material is virtually untouched, since no commercially successful method has yet been found for concentrating it to a grade suitable for the blast furnace. Intensive experimental work is in progress, and the problem is gradually being solved. In 1922 the Mesabi Iron Co. spent several million dollars erecting a large-scale pilot plant for concentrating and sintering the magnetic taconites on the east end of the range. An important tonnage of high-grade sinter was shipped to lower lake furnaces, proving that the taconite can be concentrated to a satisfactory grade. The costs, with equipment and methods then in use, were too high for

Jan 1, 1941

By Frank Van Horn

IT is customary to ascribe two general modes of occurrence to natural gas, namely shale. gas which, as the name indicates, is found in' shale, and reservoir gas, which occurs ill sandstone, conglomerate and dolomitic limestone. Both of these types are found in the Cleveland district. The shale gas has been produced on a small scale for a long period of years, probably dating back as far as 1883. Shale gas is a low-pressure gas, small in volume with variable pressure, and is limited to no definite horizon. It is generally independent of oil, may last for a long time, and is not dependent to any great extent on the structure of the rocks. There are many such wells in the district which range from 400 to 1,840 ft. in depth, although most have been completed at about 800 ft. This indicates that the wells pass through the Cleveland and Chagrin shales into the Huron or Portage shale of the Upper Devonian. During the last 2 years great interest has developed in a deeper-seated reservoir gas. What is commonly called reservoir gas is generally a high-pressure gas occurring in large volume at a definite horizon. Oil may, or may not, be associated with the gas, and in most regions in which reservoir gas is found, the geological structure is of great importance. This type of gas occurs in all large fields such as those of West Virginia which have been supplying Cleveland until the recent discovery of local gas at great depths in commercial amounts.

Jan 1, 1917

By Walter White

THE measurement of the reading of a thermoelement is the measurement of an electromotive force extraordinarily small compared to those generally used in commercial work. Of the various possible methods of measuring such a quantity, the most advantageous is always a delicate galvanometer. Since a galvanometer measures current, it is necessary to adopt some scheme by which its current reading shall indicate electromotive force. There are two general methods of doing this. One is to use the delicate galvanometer as a "direct reader," that is, to let the electromotive force of the thermoelement furnish the power and produce the current measured. If the resistance is constant the reading will, after a suitable calibration, give the electromotive force of the thermoelement which, by means of a table or of a suitable scale in the galvanometer itself, will FIG. 1.-SIMPLIFIED POTENTIOMETER. POTENTIAL DROP ACROSS THE PART PIN or CIRCUIT OF BULL CELL BALANCES THAT OF THERMOELEMENT TC WHEN GALVANOMETER G READS ZERO. give the temperature. The other method, that of the potentiometer, is to balance the electromotive force of the thermoelement by means of another electromotive force, using the galvanometer to tell when the balance is made. The usual way of getting this other electromotive force is to have a battery, the "bull" cell, send a current through a series of resistances, which 'may in a special case be the resistance of a single wire. The fall of potential along this circuit will then, by Ohm's Law, be proportional to the resistance; the potential difference between any two points, proportional to the resistance between the two points. This is represented in Fig. 1, where M and N are the two points in the circuit AZ of the battery. If M or N, or both, is movable so that the resistance

Jan 9, 1919

By Allen Rogers

IT IS universal practice for corporations, at the end of the fiscal period, to call in a firm of chartered accountants to audit the books. The effect of this is to put an independent organization's seal of approval on the accounting of the business done by the management. Their report lets the stockholders know that the accounts rendered truly present the results of the year's business. This is as it should be; the average stockholder has no personal contact or even acquaintance with the managers of his enterprise and the approval of their stewardship by an indepen-dent agent is very desirable for maintaining confidence in their honesty and ability. But such an examination deals only with what may be called the arithmetic of the business; even the most elaborate audit, as the practice is at present, goes no further than to verify the items of the inventory. In other words, while checking up the entries showing the transaction's of the year and certifying to the correct-ness of the items of the balance sheet, such a report gives the stockholder no idea of the ability with which his affairs have been managed. If the profit and loss balance is satisfactory, as certified by the public accountants, he assumes that the management has been able; where it is not, he turns to the president's report and usually finds an explanation. Such an explanation never takes the form of admission of mis-takes in business judgment or of bad technical manage-ment. It could hardly be expected that it would. The stockholder is generally furnished, therefore, with a certificate of the honesty of his management, but never one of its ability. He does not worry about the latter as long as dividends come in; when they cease, his action generally finds expression in replacing the management. In other words, so long as profits are realized, he assumes the management to be good, even though its success is a matter beyond its control and better management would make larger profits. When there is no profit, the stockholders have no means of knowing whether it is due to conditions beyond the control of the management, as the annual report is sure to allege, or whether, by better management, profit is possible. Here is where the technical audit comes in.

Jan 6, 1922

By G. F. Tagg

In an earlier paper1, the author described a method of interpreting earth-resistivity curves, based on the theoretical investigation of a single horizontal underlying stratum. If the four-electrode system of Wenner is employed, the resistivity in a homogeneous soil is given by the formula where a is the electrode separation and R is the resistance of the earth between the two inner electrodes. If the earth is not perfectly homogeneous, the application of this formula gives an apparent specific resistance varying with the electrode separation. In the special case of the single horizontal underlying stratum, there is a surface layer of thickness h and resistivity p1 and a lower layer, extending to infinity, of resistivity pz. It has been shown by Lancaster-Jones2 that the apparent resistivity obtained by an application of equation 1 is related to the true resistivities, the depth h and the electrode separation a by an expression of the formhere pa is the apparent resistivity and F is a function (actually an infinite series), of the ratio h/a, and a reflection coefficient k = (p2 — p1)/(p2 + p1). For given values of h/a and k, the right-hand side of equation 2 can be calculated, and curves drawn showing the relationship between pa/p1, h/a and k. Such a set of curves for the case when p1 > p2 is given in Fig. 1. When pl is less than pz it is more convenient to use conductivity instead of resistivity. Hence, if oa = the apparent conductivity = lip, and a1 = the conductivity of the upper layer = l/pl, it follows that GeophyGical prospecting by earth-resistivity methods is frequently applied to investigation of structural problems in geology. Fig. 1 indicates a scheme of the general arrangement used in these methods of measurements. The battery (or generator) E is connected with two "current electrodes" I1 and I2. The current of intensity J, supplied by this battery, passes through the earth between these elcc- trodes. A potential difference U will be measured between two other electrodes V1 and Vz, called "potential electrodes." According to the configuration of electrodes (Fig. I), the resistivity of a homogeneous soil results from the formula

Jan 1, 1940