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By F. H. Newell

In 1888 the United States Geological Survey began a systematic examination of the water-resources of the West, comparable in character and scope to the study of the deposits of ores or coal. As experience was acquired, the surveys were extended to the East, until now they embrace representative localities in all parts of the United States. The object to be attained is to note and record the distribution of water-supply, and to learn, as far as practicable, the laws governing its fluctuations.

Jan 1, 1901

By A. S. Richardson

PROGRESS in health and safety in the mining field has been greatly affected by war conditions. Some of the instruments commonly used in ventilation and dust prevention work have been practically unobtainable. Much equipment, such as fans, has been purchasable only when it was possible to make positive statements to the effect that it was absolutely necessary for the production of definite quantities of materials essential to the war. Even then, long delays were usually experienced in obtaining such equipment from the manufacturers. These circumstances have, of course, not been conducive to the development of new and better methods, though attention has been directed by governmental agencies towards the recognition of existing hazards to which little attention had previously been paid.

Jan 1, 1945

JAMES E. HOWARD,* Washington, D. C. (written discussion?). -Mr. Comstock, in his classification of the possible causes of transverse fissures, has not quite caught the point of view of the writer. It appears, following the trend of thought in Mr. Comstock's paper, that three groups instead of two might bee enumerated, namely: Fatigue of the steel, quality or, preferably, grade of steel, and mill practice. All steels are liable to failure by fatigue. Stresses that are capable of causing fatigue fractures are modified in their magnitude by the grade of steel acted upon. Mill practice is a term having a very wide meaning and in its relations to the development of transverse fissures has been used with such vagueness as to include many known factors and some that are unknown in the arts. According to the grade of steel employed, fatigue fractures may be accomplished by loads of greater or less magnitude, hence there is a relation between quality, or grade, of steel and the display of fatigue fractures. Mill practice of such an order as to affect the formation of transverse fissures must be shown to exert an influence on the ability of the steel to endure repeated stresses. Different grades of steel are selected for different purposes. Steel employed for fire-box purposes is of different grade from that used for cutting tools; although each grade is suitable for its purpose, and therefore of good quality. It is conceivable that a demand might be made for steel of physical properties in excess of those of any known grade. Under such a demand, impossible of' fulfillment, it would not be proper to refer to the steels as being deficient in quality; to do so would be a failure to recognize that all steels have their limitations in strength. Service conditions peculiar to rails admit of successive advance until the conditions can no longer-be met. The failure of a large number of rails from one type of failure, when all known means of averting the failure have been employed without success, is sufficient evidence that the end is close at hand. Iron rails, for a time, successfully met the requirements of railway service but weight of equipment, motive power, and rolling stock were increased, necessitating the use of steel. The early steel rails enjoyed the reputation of being of excellent quality, although: neither chemically nor structurally would they be so regarded ,lit the present time. They did good service in their day and under the conditions then prevailing were good rails. To meet the increased weight of rolling stock there has been

Jan 3, 1919

By F. L. Ransome

THAT geology and mining should stand in close and mutually helpful relationship was recognized in the United States at an early period, but it is not possible to set a precise date at which the study of ore deposits became a thoroughly reputable and important branch of geological science. As early as 1850, appeared the first ,part of Foster and Whitney's report1 on the Lake Superior region, devoted mainly to the copper-bearing areas, followed, in the succeeding year, by the second part,2 on the iron lands. This appears to have been the first comprehensive report on what might, at that time at least, be called "western" ore deposits to be prepared and published under the auspices of the Federal government. An outgrowth from this work was Whitney's Metallic Wealth of the United States,3 which appeared in 1854. It was the earliest general work on the ore deposits of the country, and remained a standard reference book for marly forty years. From 1853 on, various parties were sent out by the War Department to explore routes for proposed railways and wagon roads from the Mississippi Valley to the Pacific Coast. Geologists were attached to most of these parties, but their work was mainly of broad reconnaissance character, little attention being paid to ore deposits. Although the

Jan 1, 1933

By John Birkinbine

The experience of the past five years has furnished opportunities to study and to partially explain the operation and some of the causes of the short blast of Warwick Furnace at Pottstown, Pennsylvania, as described in the paper read at the Lake Superior Meeting, in August, 1880.* The many inquiries concerning the details of furnace operation which followed the publication of the paper, and the expressed desire of furnace managers to be informed as to future operations of this plant, have encouraged the preparation of the following data. To make the record continuous, and add to the value of both contributions, the present paper commences where the review of a short blast of Warwick Furnace ended, and includes the data of another short blast of two months, and a subsequent continuous campaign of nearly five years, which, by comparison, we shall designate as "the long blast." Frequent visits to the plant in the five years, during which its operation could be studied, and correspondence with the manager, Mr. Edgar S. Cook, have given a knowledge as to general features and details, and the courtesy of the officers of the Company which has given free access to the books of record permits the presentation of data which it is believed will be welcomed by furnace managers. Interest will undoubtedly be increased by the remarkable results which Mr. Cook has achieved chiefly with anthracite coal in a furnace whose details of construction will scarcely be generally admitted as embodying advanced ideas, its height being but 55 feet, with a bosh diameter of 15 feet 6 inches, its bosh-slope comparatively flat, its crucible smaller than the average, and the heat of the blast never reaching 1000' Fahrenheit. At present writing the credit of the best anthracite blast-furnace practice recorded in our Transactions is conceded to be that pursued by Mr. Fackenthal, at the Durham furnace, and Mr. Cook, at War-

Jan 1, 1886

By S. W. Parr

THE extent to which geological carbonization has taken place in the process of coal formation is a fundamental factor in all considerations relating to classification, oxidation, deterioration, spontaneous combustion, and especially in all considerations relating to destructive distillation having as an objective the production of marketable coke and by-products. Moreover, it may be readily shown that a. striking relationship exists between the geological decomposition or geological carbonization processes and those artificially produced by heat. This may be well illustrated by bringing again to view some of the charts more commonly met with 25 years ago, as in Fig. 1. 1 FIG. 1. In this figure the line of geological decomposition by decay, pressure, etc., because of its relation to the line of carbonization by destructive distillation, becomes of special significance when we attempt to formulate any system of classification which shall be reasonably scientific and at

Jan 2, 1926

By Samuel S. Wyer

Discussion of the paper of SAMUEL S. WYER, presented at the New York meeting February, 1916, and printed in Bulletin No. 110, February, 1916, pp. 263 to 279. DAVID T. DAY, Washington, D. C.-I would like to ask whether the court decisions quoted in the paper are general, or do they represent one side of the case; if so, are there any decisions that represent more than one side of the case? Are they of general application, or do they affect only one side? Also, what is the difference between a pump and a compressor from the standpoint of the natural-gas industry? I notice stress is laid on the word "pump" in. connection with some of the legal decisions, and then it is stated. that they must not pump or compress above 300 lb. The question is, is a pump a compressor and a compressor a pump, under certain conditions? SAMUEL S. WYER, Columbus, Ohio.-Answering the first question, I will say that the decisions cover both sides of the case very thoroughly, and are uniformly on the side that a company is justified in the use of gas compressors; in other words, there are no decisions holding it to be illegal to use gas compressors, with the exception noted in Indiana, Kansas, and Oklahoma where you cannot go below atmospheric pressure. In regard to the second question, I think the engineers and the gas operators themselves are responsible for the confusion. It is because the use of the term "pump" is almost universal, and so many people have obtained the idea that the primary function of a gas compressor is to pump air into the gas, in order to increase the consumers' gas bills. I appreciate that it is very hard to draw a clear line of demarcation. between a pump and a compressor. The distinction I have always made myself, and which I think is a logical one, is that you do not get the pumping action until you get below atmospheric pressure. As far as the compression end is concerned, there is only one State, namely, Indiana, that has any statutory limitation with regard to how high the pressure may be increased in order to put the gas into the transmission lines. The State law in Indiana limits the maximum pressure to 300 lb. per square inch.

Jan 5, 1916

THE second operation in the art of casting, and one of the greatest importance, is that of melting and thoroughly liquefying the materials of which you wish to make your casting. On this operation depends the whole outcome of your intentions and the perfection of your work. Without it, even though you had a great abundance of moulds and vast quantities of bronze, your desires, labor, and expense would all be in vain. In this operation I find on consideration that, in addition to experience, there are three necessities-perhaps indeed four-that must be provided without fail. The first is the furnace or other agent which contains the fire and the metal brought together. The second is the wood or charcoal which is the necessary and proper nutriment of the fire, from whose virtues are derived the greater or lesser forces which, according to their kind, are ready to effect what is required. The third is to have the materials disposed to easy fusion by means of corruption, alloying, or by their own nature. The fourth, as the motivating cause of the whole, could perhaps be listed as the first-this is the ingenuity and good judgment of the worker, together with the bodily exertions not only of himself but also of his helpers in addition. For, besides a certain ordinary caution, it is necessary to pay particular attention, first, to see that the furnaces, machines, ladles, hearths, refineries, and other kinds of instruments or similar vessels be made so as to dispose the metals for melting, and, when melted, that they easily maintain them so. These should also be prepared in such a way that they cannot be injured by the fire, for if they should be damaged the operation would fail. In order to do this, it is first necessary that you arrange the instruments with forethought and action so that the power of the fire can operate. Fire operates on things only when brought together with them in long-continued operation, or when driven by a great force of wind. It burns many things and softens others, but it makes the metals as liquid as water.

Jan 1, 1942

By J. B. Scott, J. L. Popham, H. F. Coffer, J. J. Reynolds

This paper concerns field experiments to define the areal extent, orientation and thickness of an artificial fracture in the Sacatosa field, Maverick County, Tex. The fracture was made by a sand-oil treatment of 176,-000 gal of lease crude containing a fluid-loss additive and 270,000 lb of 20-40 mesh subangular Poteet sand. The well was perforated with a jet gun, consisting of six shots in a single plane. Fourteen test holes were drilled at various locations around the fractured well. Drill-stem tests, Micro and Sonic Logs, coring and sampling of formation cuttings were used to determine the presence of the fracture in these holes. The test holes were drilled at distances up to 250 ft in a radial pattern around the fractured well. In addition to fracture areal extent and orientation, sand grain size before and after fracturing, erosion of perforations and fracture thickness were studied. INTRODUCTION The orientation,12 areal extent3, 4 and thickness5-9 of artificially induced fractures in reservoir rock by hydraulic means have been discussed in great detail in the oil industry in recent years. Methods for initiating vertical"' and horizontal" fractures have been tested in the laboratory and the field. Although the methods used give successful well stimulation, good field data on the physical characteristics of the fracture are lacking in the literature. It is recognized generally that properties of a fracture, such as thickness, sand placement in the fracture" and shape, may vary from reservoir to reservoir. This paper gives data on size, orientation and sand placement in a large fracture initiated in a single plane in Sacatosa field, Maverick County, Tex. It is not intended as a speculative study; rather, it is restricted to actual field data on fracture properties. No attempt is made to prove that the same type of fracture occurs in all wells. The field procedure was to drill 14 test holes at various locations around the fractured well. By employing several different testing techniques, the presence of the fracture and some of its characteristics were determined. These techniques as well as the results obtained are discussed in detail in this paper. DESCRIPTION OF FRACTURE TREATMENT N. J. Chittim Well No. 37-1, completed in the San Miguel No. 1 sand, Sacatosa field, Maverick County, Tex., was chosen for the field study. The San Miguel sand is a tight, well consolidated sandstone with an average porosity of 23 per cent. The permeability ranges from 0.1 to 10 md, with a median permeability of 2.3 md. The sand thickness averages 23 ft and is located at depths of 1,150 to 1,700 ft throughout the field.I3 The fracture treatment performed on Well 37-1 was as follows. 1. The well was drilled to a depth of 1,438 ft with native mud, and 51/2-in. casing was set and cemented to the surface. 2. The casing was perforated at 1,349 ft with a fracture-initiating jet gun. This gun consists of six shots, 7/16-in. diameter in a single horizontal plane. The jets were oriented in two groups of three, 180" opposed. The perforating device was designed to initiate a fracture perpendicular to the wellbore.

By H. F. Moore

This paper gives a preliminary summary of results of tests on the resistance to fatigue under reversed stresses of steel subjected to cold-working and of tests to determine the effect of rest on the endurance of steel under reversed stresses. The tests of cold-worked steel were undertaken as part of an investigation by the National Research Council Committee on Fatigue Phenomena of Metals and were made by Mr. Moore; the tests to determine the effect of rest are part of an investigation now being made by Mr. Putnam. Both series of tests were made in the Materials Testing Laboratory of the University of Illinois. The preliminary results of these tests are reported now. because it is believed that test data on fatigue strength should be available at the earliest possible moment; however, it should be clearly kept in mind that this paper gives preliminary results and is intended to encourage discussion rather than to give final conclusions. Before giving the data of the tests, the writers will explain the term "fatigue strength" as used in this paper and will discuss briefly the method used in interpreting the test data of repeated-stress tests. The term fatigue strength, as applied to a material, may be defined as that maximum fiber stress that will cause fracture of the material after the repetition of any given number of cycles of stress, each cycle involving the variation of stress from a minimum to the above maximum. The fatigue strength, then, varies with the number of repetitions occurring in the lifetime of a structural or machine member and with the range of stress for each cycle of stress. The fatigue strength will be lower for a member in which the stress is completely reversed than for one in which the stress varies from zero to a maximum. In interpreting test data from fatigue tests under reversed stress, the stresses and corresponding numbers of repetitions required for failure are plotted on logarithmic cross-section paper. In 1910, Professor

Jan 2, 1919

By F. C. Bond

B. H. Bergstrom (Allis-Chalmers Mfg. Co., Milwaukee)—In reading this article, it was difficult to follow through the example given as a starting point in the derivation of the theoretical equation which relates ball size to feed size. A discussion with F. C. Bond led to the following clarification: Bond postulates that "the breaking force exerted by a ball varies ... as the cube of its diameter . . ." and that the force in pounds per square inch required to break a particle varies ... as its diameter squared." He concludes: "It follows that when a l-in. ball breaks a 1-mm particle, a 2-in. ball will break a 4-mm particle, and a 3-in. ball a 9-mm particle." The above example can be true only for a different set of assumptions. Since the first assumption is apparently true, it is the second that must be revised. The second assumption should read that the breaking force required to break a particle varies as its diameter to the 3/2 power. This relationship was derived in the next paragraph of the article.

Jan 1, 1960

By H. Ries

INTRODUCTION OF the several interesting physical properties of clay which have claimed the attention of investigators in recent years, none is more important than the behavior of the material when heated to temperatures above those of dehydration. Some of the problems to be solved are: 1. The mineralogical changes that take place in firing. 2. The relation between temperature and change in constitution, shrinkage, porosity, etc. 3. The importance of the time factor, as duration of firing, either in reaching a given temperature, or of exposure to a constant temperature. Mineralogical Changes As a result of fusion, reactions take place between the constituents of a clay, which results in a reorganization of the mass, and the formation of new compounds. Of the new minerals developed, sillimanite is the one usually recorded, and has been referred to by a number of observers.1 There appears to he a difference of opinion, however, regarding the temperature at which it is formed. Thus. Klein2 notes that sillimanite forms only above. 1300° C., while Mellor claims that it can develop below 1200° C., the difference in results being conditioned by the time factor. In Klein's experiments the test pieces were fired in 12 hr., while in Mellor's, the temperature rose from 800° to 1180° in 24 hrs., and occupied the same time in cooling back to 800°.

Jan 9, 1917

By I. Javandel, P. A. Witherspoon

The finite element method was originally developed in the aircraft industry to handle problems of stress distribution in complex airframe configurations. This paper describes how the method can be extended to problems of transient flow in porous media. In this approach, the continuum is replaced by a system of finite elements. By employing the variational principle, one can obtain time dependent solutions for the potential at every point in the system by minimizing a potential energy functional. The theory of the method is reviewed. To demonstrate its validity, nonsteady-state results obtained by the finite clement method are compared with those of typical boundary value problems for which rigorous analytical solutions are available. To demonstrate the power of this approach, solutions for the more complex problem of transient flow in layered systems with crossflow are also presented. The generality of this approach with respect to arbitrary boundary conditions and changes in rock properties provides a new method of handling problems of fluid flow in complex systems. INTRODUCTION Problems of transient flow in porous media often can be handled by the methods of analytical mathematics as long as the geometry or properties of the flow system do not become too complex. When the analytical approach becomes intractable, it is customary to resort to numerical methods, and a great variety of problems have been handled in this manner. One such method relies on the finite difference approach wherein the system is divided into a network of elements, and a finite difference equation for the flow into and out of each element is developed. The solution of the resulting set of equations usually requires a high speed computer. When heterogeneous systems of arbitrary geometry must be considered, however, this approach is sometimes difficult to apply and may require large amounts of computer time. The finite element method is a new approach that avoids these difficulties. It was developed originally in the aircraft industry to provide a refined solution for stress distributions in extremely complex airframe configurations. 27 Clough has recently reviewed the application of the finite element method in the field of structural mechanics.6 The technique has been applied successfully in the stress analysis of many complex structures.l, 27, 28 Recognition that this procedure can be interpreted in terms of variational procedures involving minimizing a potential energy functional7 leads naturally to its extension to other boundary value problems. In the field of heat flow, there recently have been introduced several approximate methods of solution that are based on variational principles.2-4, 17 By employing the variational principle in conjunction with the finite element idealization, a powerful solution technique is now available for determining the potential distribution within complex bodies of arbitrary geometry. In the finite element approximation of solids, the continuum is replaced by a system of elements. An approximate solution for the potential field within each element is assumed, and flux equilibrium equations are developed at a discrete number of points within the network of finite elements. For the case of steady-state heat flow, the technique is completely described by Zienkiewicz and Cheung.33 Since the flow of fluids in porous media is analogous to the flow of heat, Zienkiewicz et al. have employed the finite element method in obtaining steady-state solutions to heterogeneous and anisotropic seepage problems. 34 Taylor and Brown have used this method to investigate steady-state flow problems involving a free surface.25 The work of Gurtin has been instrumental in laying the groundwork for the application of finite element methods to linear initial-value problems.12 As a result, Wilson and Nickell have recently

Jan 1, 1969

By A. D. S. Gillies

One of the most difficult places to ventilate in any mine is the working face area. With an everchanging configuration, continual modification and extension to the ventilation system is necessary to maintain an adequate supply of fresh air and to avoid mixing and recirculation in the face area. In coal mines, methane emissions and high dust levels as coal is broken and removed from the face area can produce unhealthy and dangerous conditions if ventilation is not adequately monitored.

Jan 1, 1982

By Andrew B. Crichton

THE oft repeated statements of the United States Geological Survey and the Bureau of Mines that the coal reserves in the United States are sufficient for 3000 yr have given us all a sense of security hard to disturb. If we discount that statement 66 pct, which to the uninformed seems drastic, we would still have 1000 yr supply, and why should mortal man worry about the difference between 1000 and 3000 yr supply of coal. That is exactly the attitude which many who should be better in- formed have taken toward the problem. A recent brochure "How Strong is America," by the New York Herald Tribune, states there is "no end to coal * * The truth is staggering * * U. S. has enough coal to last 4000 years." What the statement actually means is that the calculator got as high as 4000 yr and decided it was pointless to go on. The President's ERP Committee on Natural Resources and others in high places continue to assure the country of our superabundance of coal. In the past few days the “Wall Street Journal" carried an item from Director Boyd of the Bureau of Mines saying that within a hundred years we would need to triple our annual coal production of 6oo,ooo,ooo tons, making it 1,800,000,000 tons annually, and at that rate we had coal reserves sufficient for 1000 yr. In my humble opinion, we cannot now or ever produce 1,800,000,000 tons annually, be- cause we do not have the reserves in the producing districts to do it. Past reckoning in geology may be, as in the Psalms, a thousand years are as yesterday, but the future must be considered more realistically, and "a thousand years" is really a "heck" of a long time. In most developed areas, mining engineers can count the coal reserves in terms of a hundred years or less, and in some important areas now producing large annual tonnages in much under fifty years. They think when they hear of thousands of years coal reserves, reference is made to distant fields and "the fields are always green far away." The estimates of our coal reserves upon which we are relying were made in 1907 under the direction of Marius R. Campbell, Director of the United States Geological Survey. It is apparent this work was not well done. It was necessarily based on rather meager data because of the little development and prospecting as of that date. There were mistakes in the correlation of seams, and they assumed the continuity of thick seams throughout large coal bearing areas where coal often did not exist. The overstatement of coal bearing areas in the Campbell figures are common. The 1907 survey includes all coals over 14 in. in thickness to a depth of 3000 ft. The total coal reserves according to Campbell were 3157.2 billion tons. The production and mining losses that year would amount to -570 million tons and

Jan 1, 1948

By S. Le Fevre

THE application of electricity to the mining and beneficiation of the magnetic iron ores of the Mineville, N. Y., district, on Lake Champlain, has resulted in economies and enhanced quality of product, without which only a comparatively small quantity of the present output could be marketed. The output of the Witherbee, Sherman & Co. mines is about 700,000 tons per annum, and of this about four-fifths is treated by magnetic separation to increase the iron content and reduce the phosphorus. The use of electricity for the magnetic separation of the ore from the gangue is therefore of primary importance, and makes possible the application of electric power for mining and preparing the ore for concentration: The fact which speaks loudest in favor of the application of electricity is this: It is possible for about 25c. per ton of shipping ore to furnish all the power required to put the ore on cars. This includes mining a hard ore underground, from a depth of 900 ft., hoisting to surface, crushing to 4 or s in. in size, and separating from the gangue. This also includes lights about the works, and all miscellaneous power, such as about the shops. The first plant for the generation of electric power for use at Mineville was completed in 1903, and was one of the first for the application of electricity to mining iron ore. This was a Nordberg compound condensing steam engine, direct connected to a 750-kw. alternating-current generator, 3,300 volts, 3 phase, 25 cycles. All the plants added later use the same-current but with higher voltage. The map, Fig. 1, shows the power plants and the transmission system; Figs. 2 and 3 are views of the shaft houses and the mills.

Jan 6, 1914

By D. A Dahlstrom

THE necessity for slime elimination from valuable mineral and coal products has become increasingly significant within the past 5 years.' , Most of the mechanized mining and present beneficiation methods have resulted in larger tonnages of extreme fines, silts, and clay, commonly called slimes, processed by the preparation plant. Economics in turn have forced the plant operator constantly to lower the bottom size of effective beneficiation, necessitating an almost complete recovery of valuable solids regardless of particle size. When these important factors are considered, the need for an efficient slime removal method for fine solids becomes self-evident. Ordinarily slimes have been classified as ranging from 75 microns, or 200 mesh, down to colloidal dimensions of less than one micron. At the same time there is general agreement that the most troublesome slimes are primarily clays, silts and extreme fines, so that the actual top size may be placed at approximately 30 to 40 microns. This immediately restricts any desliming operation to classification, as screening or other methods would be both uneconomical and grossly inefficient at such dimensions. The liquid-solid cyclone has been recognized as one of the most efficient fine size classifiers available to the mining industry. Applications of cyclones to thickening, high efficiency solid recovery, degritting,

Jan 1, 1953

By D. A. Dahlstrom

THE necessity for slime elimination from valuable mineral and coal products has become increasingly significant within the past 5 years.' , Most of the mechanized mining and present beneficiation methods have resulted in larger tonnages of extreme fines, silts, and clay, commonly called slimes, processed by the preparation plant. Economics in turn have forced the plant operator constantly to lower the bottom size of effective beneficiation, necessitating an almost complete recovery of valuable solids regardless of particle size. When these important factors are considered, the need for an efficient slime removal method for fine solids becomes self-evident. Ordinarily slimes have been classified as ranging from 75 microns, or 200 mesh, down to colloidal dimensions of less than one micron. At the same time there is general agreement that the most troublesome slimes are primarily clays, silts and extreme fines, so that the actual top size may be placed at approximately 30 to 40 microns. This immediately restricts any desliming operation to classification, as screening or other methods would be both uneconomical and grossly inefficient at such dimensions. The liquid-solid cyclone has been recognized as one of the most efficient fine size classifiers available to the mining industry. Applications of cyclones to thickening, high efficiency solid recovery, degritting,

Jan 1, 1953

By Reynold Q. Shotts

INTRODUCTION THE small domestic underfeed stoker as now designed is unusually sensitive to the coking and plastic properties of coals, and when the attempt is made to burn the high rank coking and caking coals of the Appalachian fields, serious trouble may occur. Part of the trouble may be caused by the ash content and clinkering characteristics of the particular coal in use, but more often it is the result of an excessive accumulation of coke in the form of "trees" or masses in the fuel bed. Often the zone of burning becomes so restricted that the fire goes out, and in extreme cases the fire may be lifted completely out of the fuel bed and away from the air ports. Even if the fire is preserved, excessive coking may cause response to subsequent heat demand to be slow and irregular. Coke trees seem to grow. most readily during periods of hold-fire operation, so that in order to preserve the fire in mild weather it is often necessary to set the timer for such a long operating period each hour that much unneeded and unwanted heat is developed, causing discomfort. During demand periods the fire may pick up so slowly that the intense burning which develops just before stoker cut-off causes a serious overshooting of the thermostat. Stoker coal performance tests which have been made in a number of laboratories 1, 2, 3, 4, 5 are one method of approach to the problem of selecting stoker coals. As yet these tests have not been standardized and they are expensive and time-consuming. The value of the results probably increases with the length of the test. Sherman and co-workers at Battelle Memorial Institute believe that even a one-week test is not too reliable a trial2 and it is quite likely that others will agree. A great advantage of such tests is that characteristics of coals, other than the tendency to form coke masses, may be evaluated from them. The selection of stoker coals would be greatly facilitated if there existed some simple measure of the tendency of a coal to form coke in a fuel bed. Although possessing all of the disadvantages of any small-scale laboratory test, the test for the free-swelling index of coal has been found useful for evaluating the probable effects of swelling properties upon combustion. 7 Ostborg, Limbacher and Sherman, have shown that the test can predict, roughly, the tendency of coke to accumulate in the fuel bed of a domestic stoker. They also gave instances of its value in predicting combustion behavior in some large installations. The use of the test for free-swelling index has become well established and has been adopted as a standard by the American Society for Testing Materials.8 When domestic stoker coal investigations began at the State Mine Experiment Station in the summer of 1944, it was decided

Jan 1, 1948

By H. R. Hanley, Charles Y. Clayton

One of the most important contributions to the art of electrolytic zinc production has been the aluminum cathode. This has been used in all major production since its commercial development in 1916. The literature is replete with important contributions, some of which may have been replaced by better ones, but thus far there appears no other metal to take the place of aluminum as cathode material. Credit for this innovation goes to Sherard Cowper Coles, of England. When experimenting on the extraction of zinc from Broken Hill ore at Hayle, Cornwall, in 1893, he introduced the aluminum cathode, and in 1895 obtained British Patent No. 20073. The reason for this dominant position of aluminum as cathode material in zinc sulphate electrolytes is its unique surface, to which electro-deposited metals usually do not tightly adhere. The metal must, be of high purity for best results. It is possible to develop a starting-sheet method by which thin electro-deposited sheets of cathode zinc are made and stripped from a smooth aluminum plate. Such thin sheets of cathode zinc may be used as are the copper sheets in standard electrolytic copper-refinery practice. However, complications arise because of extreme warping of the zinc starting sheet after a few hours of deposition, and thus special arrangements must be made to compensate for this abnormality. Reasons advanced for the ease with which deposits may be stripped from the aluminum surface are: (1) presence of a permanent oxide coating on the metal, (2) failure of aluminum to alloy with the deposit, (3) differences in coefficient of expansion, (4) high position of aluminum in the electromotive scries of metals. Of these reasons for nonadherence, which may have some application in general deposition, probably the oxide coating has the greatest bearing on the subject of zinc deposition. Adherence of zinc deposits has occasionally had serious effect on tonnage and production costs. Opinions have differed as to the specific

Jan 1, 1943