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By Jan Wolski

Today's rapidly shrinking world requires a common language of measurements, a consistent system which could be used by everyone. The S.I. system of units is generally accepted as such and is already in use by a great majority of nations in the world. The change to S.I. units is also slowly taking place in U.S. engineering practice. The transition period is difficult and long because it takes time to get familiar with the new system, to start "feeling" values in new units. Instruments, formulas, computer programs, survey grids, etc. have to be converted or exchanged. The transition period should be used not only for substitution of units, but also for rationalization of presently used calculation methods. This paper examines the major parameters of mine ventilation from the above point of view and discusses a system which is much simpler and more consistent than the American Unit System still in use in the United States. In October 1979, the Society of Mining Engineers of AIME decided to introduce the S.I. unit system in all its publications including the periodical "Mining Engineering", and since February 1980 the system has been used consistently, not only in SME publications but in all conferences and meetings organized by this Society. The authors have no intention of explaining the details of the S.I. system in general. Any reader can find this information in many available publications and conversion tables, and in particular in the ASTM Standard for Metric Practice, E380-79. A comparison is made between various units used in mine ventilation from the past and those presently in use. This will allow an easy translation from one system to another, important when reading publications from abroad. S.I. and customary U.S. formulae are shown side by side for easier visualization of similarities and differences. Recommendations for the necessary steps in order to switch from American to S.I. units conclude the paper.

Jan 1, 1982

By Frank W. Osterwald

Violent, spontaneous destruction of coal faces and ribs during, what are commonly called, bumps endangers and at times destroys life and property in mines of the Book Cliffs coalfield, Carbon County, Utah. Because these mines supply much of the coking coal for the West Coast steel industries, mining is necessary, although costs are high and operating conditions are very difficult at times. As operations continue, mining will go to greater depths, and the difficulties will increase. Whether or not mining can be continued successfully depends in part on whether or not incidence of bumps can be controlled successfully. For this reason, the U.S. Geological Survey, at the request of and in cooperation with the U.S. Bureau of Mines, undertook a study of the Sunnyside No. 1 mine to determine what geologic factors were related to the incidence of bumps. This report presents the preliminary results of that study and indicates that some observable geologic features in the mine may be related directly or indirectly to bumps, and that other features may be used to infer stress distribution around workings that will aid in design of roof support measures. Coal is mined in the Sunnyside No. 1 mine from depths as great as 2500 ft by room-and-pillar methods. The surface topography is rugged with many steep cliffs and deep canyons, hence the load on the coal varies greatly within short distances. Much of the Sunnyside coal is under high stress, and while being mined, it shatters continuously' and falls from the face. Continuous shattering (bumping) makes mining easy, but if the shattering is interrupted, greater stress is built up and violent bumps may result when the coal is mined.

Jan 4, 1962

By H. W. Hardings

Nearly every mining and metallurgical engineer will recall his early experience and method of producing step- or stage-reduction in preparing ore-samples for assay, in which he employecl idea, step- or stage-reduction simply because it was a self-evident fact that it would be easier to break coarse ore with a hammer than it would be to roll it back and forth under the muller, and alter having reduced it to a size easy for a rubbing or bucking division he then placed it under the muller on the bucking-board and further reduced it in proportion to the physical energy he wished to expend, which was generally the minimum to produce results. After this step in our experience me seem to have ceased to consider stage-reduction as mechanicallg essential, probably because it did not apply to individual exertion. Moreover, me did not retain the mass under the muller until it was all reduced to pass the 80-mesh assay-oftice screen, but practiced further step-reduction by screening out the fine in order that it should not interfere with subsequent work, replacing the coarse for further reduction on the bucking-board. It was many years after the bucking-board stage of metallurgical practice that we mere brought to a full realization that there was a more economical method in applying the crushing forces usually employed in metallurgical work by taking advantage of this individual experience and applying it to mechanical ends. We have made some advance to this end in bringing out the conical ball-and-pebble mill—a device which fairly well automatically adjusts power to the results obtained, mechanically repeating the bucking-board experience. In the action of the conical mill, theory is evolved from practice, rather than practice from theory, as is commonly the case.

Jan 1, 1914

By Will H. Coghill, J. Bruce Clemer

Flotation has been so closely allied with the sulfide minerals and their early and associated oily reagents that the term "oil flotation" has erroneously been applied to the entire flotation process. Today, the term "chemical flotation" might be used to advantage. Flotation literature has dealt primarily with the removal of sulfides from non-sulfide gangues, and the separation of one sulfide from another. Now, the application of the process to the separation of nonsulfide minerals is coming to the fore; and from the standpoint of the number of commercial minerals involved, the flotation of nonsulfides offers the larger field. Here, soap or soap-forming substances, such as the fatty acids and their derivatives, are used; hence there may well be a subdivision of the chemical flotation process called "soap flotation." Early experimenters learned that it was easy to form a froth or foam that would carry a part or all of the ore charge over the lip of the flotation machine; but this could not be regarded as flotation because of the lack of selectivity. Doubtless soap was one of the first reagents tried, and doubtless it was rejected on account of its gangue-carrying properties. Now this same gangue-carrying ability makes soap an acceptable reagent, for we are dealing with that which, among sulfides, is considered "gan-gue." As in the flotation of sulfides, so in the flotation of nonsulfides, the selective flocculation of the mineral and the dispersion of the gangue are the first objectives. In fact, these two phenomena epitomize flotation. They depend upon the unlike surface properties of the respective minerals; and as long as the components of an ore have unlike surface properties, a separation is possible, at least in theory. Often in nonsulfide flotation it makes little difference which mineral floats and which is depressed; generally only a separation is sought.

Jan 1, 1935

IT does not seem practicable to review all the other specialized curricula that have developed in the mineral industries field in so much detail as has been given for petroleum. Nor is it easy to draw a definite line between true curricula, leading to a designated degree in the special subject, and options, which may range from the mere substitution of one or two courses for others in the final years to differences so extensive as almost to amount to separate curricula. Even to attempt to catalogue all the options that have been offered at one time or another would require too much space. The remainder of this discussion, therefore, will be confined to three topics which seem to be of major importance. Mining and metallurgical curricula will be covered in a later chapter. GEOLOGY The first, from the historical view, is geology in its relation to the mineral industries. Previous chapters have made clear that in the early years of mineral industry instruction in the United States economic geology and mining engineering so overlapped one another that men who were by, training and experience economic geologists were appointed professors of mining, while men who had graduated as mining engineers sometimes developed into professors of geology. Even today men whose basic training was in geology as a pure science, and who perhaps took a doctor's degree in that subject, have attained such distinction in the mineral industries as to be universally accepted as "mining men," and their right to be regarded as mining engineers would- not be questioned, even though they did not take a degree in engineering. Nevertheless the distinction does exist, and has been made a concrete reality in recent years by the enactment of

Jan 1, 1941

Prof. H. S. Munroe, New York City : In his reference to cop per-dressing at Lake Superior, p. 325, Mr. Douglas says that " the .. concentration .. . has been carried out with greatest financial economy,... I do not say with the greatest economy of min eral." And again, on p. 344, referring to the same, " it would not pay to reduce the quantity treated, and increase hand-labor, in order to save a few hundredths of one per cent. of copper." Mr. Douglas probably has in mind the fact that the copper lost is all included copper, locked op in grains of sand. To save this, the rock must be crushed finer. If the mesh of the stamp-screens be reduced, the stamps will crush less; and thus we shall have to reduce the quantity treated in the mill per day, while the labor re mains the same per day, or is increased per ton, as he says. Submitting to the loss of copper, however, is not the only solution of the difficulty. A large quantity of rich sand is now collected by the jigs, and it would be easy to save so much of this material that the escaping sands would be quite poor. What is wanted at Lake Superior, and at many dressing-works in this country, is an efficient crushing-machine to treat the sands thus collected. Abroad, we have the Heberle machine and the Schranz mill for this purpose, the latter being the more successful. The Heberle grinder was tried at the Calumet and Hecla mill for crush ing these rich sands, with what success I do not know. I should like to ask Mr. Douglas if we have no American crushing-machine that will reduce jig-sands to a fine state of division

Jan 1, 1894

By V. R. Garfias, R. V. Whetsel

As pointed out in previous studies, estimates of petroleum reserves if they are to be of value must not only presuppose a clear understanding of what is actually meant by reserves but must be subject to constant revision to conform with changes in their component factors. When such estimates are analyzed it must be clear that it is virtually impossible to obtain comparable figures reflecting the same degree of accuracy, to represent the reserves not only in various countries, but at times even of different fields in the same country. Estimates of reserves in the United States, subject to frequent independent checks, are obviously more reliable than those furnished, for instance, by the Soviet Government, as the latter must be accepted at their face value and are open to the suspicion of being made to conform with predetermined programs of propaganda. Any tabulation of the reserves of all producing countries, therefore, gives a total that is misleading, as the component items arc not arrived at on the same basis and therefore are not homogeneous in a true sense. Only a fraction of the petroleum stored underground, usually associated with natural gas, is or can be brought to the surface, and although practically all the natural gas underground can be rccovered, in actual practice in some fields a large part of the gas that reaches the mouth of the well is wasted. It is thus estimated that in the United States only some 25 to 35 per cent of the petroleum underground in proven fields is actually economically recovered. Estimates of reserves, therefore, should make clear the distinction between the known amount of oil underground in producing fields and the portion that actually can be brought to the surface. It cannot be overemphasized that as a result of the operation of the "Law of Capture," which controls subsoil ownership in the United States on comparatively small landholdings that seldom if ever cover the entire producing area, the oil fields are not as economically exploited as some forrign fields, and that as a result (were it not for the easy accessibility of the domestic market, the largest in the world) some American production would now be unprofitable in open competition with foreign oils.

Jan 1, 1939

By Samuel Wyer

F. G. CLAPP, New York, N. Y. (communication to the Secretary*).¬I assume that where this valuable paper states, near its end, that "it is not possible to establish a market price, " the author means that no particular price which will fit all conditions and fields can be given. I am not in agreement with Mr. Wyer, however, that the actual value of natural gas leaseholds is "largely a matter of opinion." I would even be willing to express myself very strongly as believing that if we, as experts, cannot give anything closer than a mere opinion, our testimony or reports are not of great value to our clients. I believe, moreover, that by detailed geological examinations and with our latest knowledge of geological structure, principles of natural gas occurrence, etc., we can approach just as near a certainty in natural gas valuations as we can in oil valuations, and much more so than in the valuation of many metal prospects, in which only the upper few feet of the vein has been opened. In other words, we are getting nearer and nearer every year to bringing geology as applied to oil and gas development into the class of an exact science. Mr. Wyer's paper gives an excellent outline for methods of leasehold valuation. Being presumably intended as an outline only, it can be expanded indefinitely by a detailed discussion of the methods of valuation for the four different classes of leaseholds which he mentions: (A) "Producing;" (B) "Protective;" (C) "Reserve;" and (D) "Prospective." This classification is probably as good as can be made in practice. In the producing leaseholds in particular it is easy to establish a market price at which these leaseholds should be bought or sold. The question would arise in any case whether or not the leases are connected with a pipe line or the distance from the pipe line. Assuming that a pipe line already taps the property and that gas is already being sold for a certain figure, this price must be multiplied by the number of thousand cubic feet still "in sight" in the ground, from which is to be deducted (a) bonuses, (b) rentals, (c) royalties, (d) cost of drilling, (e) taxes and

Jan 12, 1916

By C. K. Leith

MANGANESE is one of the minerals which is principally consumed in countries other than those of origin. Nearly 85 per cent of the pro-duction is used by the United States, England, Germany and France, and roughly a third of the total is used by the United States alone. On the other hand, over 85 per cent of the world production comes from Brazil, Russia, India, the Gold Coast of Africa, and the Sinai Peninsula. It follows from this fact that practically all manganese moves across international boundaries in raw or alloy form, and much the larger part of this movement is for considerable distances and is ocean borne. There is no indication that any one of the principal consuming countries can develop even approximately adequate supplies of its own. Under abnormal war conditions, with high prices and changes in metal-lurgical methods, only 35 per cent of the needs of the United States was met from local sources, and under our recent tariff only 11 per cent. There are thousands of manganese deposits scattered about the world, but only a very few which can figure largely in supplying requirements on a modern scale. The known reserves, together with highly probable extensions and explora-tions now under way, indicate no shortage from a world standpoint for many decades to come. The production and marketing of manganese is going steadily into fewer and stronger hands. The steel in-dustry uses over 90 per cent of all the manganese mined, and is acquiring control of a considerable part of the production in all of the principal fields-the Germans in Nikopol, the English in India and Gold Coast, the Americans in Georgia, India, Gold Coast and Brazil. Some of the controlling companies are of international scope. Concentration of commercial control is a notable tendency. A natural consequence is the growing un-easiness of smaller consumers the world over about their ultimate supplies and desire to know more definitely how and where manganese supplies will be controlled in the future. The sources of supply are few enough to warrant the belief that more or less monopolistic ele-ments of control are not impossible.

Jan 5, 1927

The opening session of the Institute was held at Hazle Hall, Tuesday evening, October 27th, with a large attendance of members. President Raymond called the Institute to order, and after a few introductory remarks, introduced Mr. I. Lowthian Bell, President of the Iron and Steel Institute of Great Britain, and Honorary Member of the American Institute of Mining Engineers. Mr. Bell was received with great applause, and made his acknowledgments in a brief speech, of which the following is the substance: He desired to thank the Institute personally for the honor conferred upon him in his election to membership, and also for the invitation extended last year to the body of which he was President. The difficulty felt by many members of the Iron and Steel Institute, of leaving for a long journey the works of which they had charge, aggravated by special industrial troubles at the time of the invitation, had obliged them to conclude that it could not then be accepted in a fitting manner. The iron .manufacture of this country is a subject of great interest to Englishmen, who look with pride upon the achievements on this side the water of the descendants of a common ancestry. His own reception in this country had far surpassed in cordiality even the well-grounded anticipations he had formed from the assurances of the President and other friends. Notwithstanding the flattering manner in which his friend, in introducing him to the Institute, had spoken of his contributions to the science of iron metallurgy, he could not take to himself alone the significance of this welcome. He knew it was a recognition of the services rendered by the body which he had the honor to represent; and he was glad to see present a member of that body, Mr. Thomas Whitwell, who had fortunately been able to make the journey at this time, arid whom he had had the pleasure of meeting on the shores of Lake Champlain. He had been requested to say something of his impressions of the American iron industry. It was not easy to digest so soon the vast

By W. H. Blauvelt

The only way in which the difficult problems of classification of coal for the manufacture of by-product coke can be solved is to analyze them by the use of scientific data. It is very easy to adopt classifications for coal for the manufacture of by-product coke along certain lines; we can easily say that for a certain class of metallurgical operation coke made from bituminous coal must not contain more than so much sulfur or more than so much ash and should yield certain returns in the by-products, tar, ammonia, benzol, gas, etc. Those points we are fairly clear on and I think it is hardly worth while to discuss them because I presume that they are familiar to most of us who have any occasion either to make coke or to use it. But there is a field in the manufacture of coke which we know very little about. For example, we are operating a plant on a certain mixture of coal. Suddenly our blast-furnace man or the user of the coke tells us the coke is not as good as it was before. The coke is analyzed and the coal is analyzed. Everything seems to be about the same as it was— the ash is the same, there is no more sulfur, and so on—but the coke, for the use to which it is put, particularly in the blast furnace, is wrong. What happens? The management decide to try a slightly different coal mixture. They do not necessarily raise the total hydrocarbons, the volatile matter in the mixture, nor change the sulfur or the ash, but they do make a change which improves the value of the coke for metallurgical use. The reason for this difficulty, as I see it, is the " combustibility " of the coke—I hesitate to use the word, but it is the best one I have available. Combustibility of Coke We know now that the combustibility of coke is a very vital point in many metallurgical processes and I think one of the most notable instances of the proof of this is the experience of the Carnegie Steel Co. in the production of coke at its Clairton plant. The history of that

Jan 1, 1930

By R. V. Whetsel, V. R. Garfias

As pointed out in previous studies, estimates of petroleum reserves if they are to be of value must not only presuppose a clear understanding of what is actually meant by reserves but must be subject to constant revision to conform with changes in their component factors. When such estimates are analyzed it must be clear that it is virtually impossible to obtain comparable figures reflecting the same degree of accuracy, to represent the reserves not only in various countries, but at times even of different fields in the same country. Estimates of reserves in the United States, subject to frequent independent checks, are obviously more reliable than those furnished, for instance, by the Soviet Government, as the latter must be accepted at their face value and are open to the suspicion of being made to conform with predetermined programs of propaganda. Any tabulation of the reserves of all producing countries, therefore, gives a total that is misleading, as the component items arc not arrived at on the same basis and therefore are not homogeneous in a true sense. Only a fraction of the petroleum stored underground, usually associated with natural gas, is or can be brought to the surface, and although practically all the natural gas underground can be rccovered, in actual practice in some fields a large part of the gas that reaches the mouth of the well is wasted. It is thus estimated that in the United States only some 25 to 35 per cent of the petroleum underground in proven fields is actually economically recovered. Estimates of reserves, therefore, should make clear the distinction between the known amount of oil underground in producing fields and the portion that actually can be brought to the surface. It cannot be overemphasized that as a result of the operation of the "Law of Capture," which controls subsoil ownership in the United States on comparatively small landholdings that seldom if ever cover the entire producing area, the oil fields are not as economically exploited as some forrign fields, and that as a result (were it not for the easy accessibility of the domestic market, the largest in the world) some American production would now be unprofitable in open competition with foreign oils.

Jan 1, 1939

By Enrique Touceda

The question as to the proper amount of total carbon that the malleable founder would prefer to have in pig iron for use in the production of air-furnace, white iron castings, must be considered from different angles, that is, whether it is desirable or advantageous from an economic standpoint to use some kind of low-carbon scrap on his mixture, or make use of pig and sprue only. Whereas silicon is the acknowledged scrap carrier in the case of cupola gray iron castings, carbon performs this role for the most part in malleable iron practice, irrespective of the character of furnace used for the production of the white iron castings. In this particular, the advantage lies with the maker of gray iron castings in that the silicon content in pig iron through a regulation of furnace temperature is under very easy control by the blast-furnace manager, whereas he has little or no control over the resultant percentage of carbon, as this is dependent on the quantity of coke in the hearth, and hearth temperature, coupled with the amount of hearth slag and its particular composition. As perhaps more than 95 per cent. of white iron castings are made in air furnaces the following statements are intended to cover that situation particularly: In the malleable process the composition of the hard iron castings (that is determined upon as best suited for the work in hand) is the one factor that must control the composition of the mixture to be used; because if the elements are not between certain definite limits individually and collectively the annealed or finished product will be unsoitable, due, perhaps, to lack of sufficient strength or because it is too hard, to machine easily. The annealed product can be divided into two classes, one of which greatly predominates, that is, by far the largest tonnage is used for machine parts where high strength and ductility are essential requisites, while a far smaller amount, light in weight and thin in section, is used for other manufactured products in which castings of any reasonable degree of strength and ductility have proved satisfactory.

Jan 1, 1927

By James Humes

THE active mines in the Park City district at the present time are the Silver King Coalition, Daly-Judge, Daly West, and Silver King Consoli¬dated. Several other companies, such as the Daly, American Flag, Ontario, etc., are doing considerable development work. In the Silver King Coalition mines the ore is a replacement of a dark siliceous limestone bed, varying in thickness from 18 in. to several feet. In places the ore has reached a thickness of 25 ft. This limestone bed lies within 100 ft. of the underlying Weber quartzite. There are other lime beds, similar in appearance to this one, in the Park City formation, which is approximately 700 ft. thick; but not one of them has been found to contain any traces of ore. Directly under and in contact with the ore-bearing bed is another, composed of gray lime well studded with dark concretionary nodules; and this one is an unfailing indication of the proximity of the ore-bearing bed. These ore deposits make out from or have connection with some one of the ore-bearing fissures, which were undoubtedly the channels for the circulation of mineral-bearing solutions. It is therefore proper to run prospecting drifts in the fissures, although they seldom contain much ore. As a general rule, drifting in the fissures is not costly. Mining and mucking cost from $2.50 to $4 per foot, and very little timber is required. There are instances, as in the Daly fissure in the Daly-Judge mine, where the expense of keeping drifts open in the fissure is so great that it has proved economical to make the drifts in the foot-wall rock and run crosscuts into the fissure at short intervals. In the Park City mines it is not easy to determine beforehand the best method for extracting the ore from a newly discovered ore shoot in the bedded deposits. While we may get one dimension from the drift run in the fissure, that will not give us a correct idea as to the other dimensions of the orebody. The fissures here referred to have a N. 35° E.

Jan 2, 1915

By Earnest R. Woakes

Those engaged in pumping from shafts, or other mining works, may be intereited in the following suggestion of what is believed to be a novel method of raising moderate quantities of water against a considerable head. It is admitted that the ordinary Cornish pump, as generally used in mines, is hard to beat, on account of both its extreme simplicity and its easy adaptation to the requirements of mining; its great drawback, however, being the enormous weight of heavy rods and successive plungers that have to be kept in motion, not to mention the necessary " balance-" and " angle-bobs," with all their accompanying friction and wear and tear. It is contended that the following method would, to a great extent, overcome these drawbacks ; though, no doubt, many old miners may say it would also introduce new ones. Possibly, this may be the case. It is only desired that this pump may be judged upon its merits. The chief novelty of the method consists in employing the almost unlimited pressure obtainable from a high column of water, augmented, if necessary, by a hydraulic ram or press at the top, to work a small-diameter piston or plunger at the bottom of a shaft or well. This high-pressure plunger, indicated at E, in Fig. 1, transmits power direct to a larger-diameter plunger, F, constituting, together with the ordinary H-piece, valves, and wind-bore, the actual pump, which raises the water, by column C, to the adit-level or other discharge, placed as far as possible below the head of the high-pressure column A and ram W. It will thus be seen, that it is only necessary to maintain a prmsnre on the small piston, E, equal to that on the larger one, F, by means of the small but high column of water, A, in order to cause F to descend, and thus force the water up through C. The up-stroke is accomplished by a small water-wheel, or other engine, connected to the light rod or wire rope B, this having only to raise the weight of the actual plungers and fill the H-piece with water from the tank or

Jan 1, 1892

By Basil Prescott

In the science of evolution of the species, there is a law which, simply stated, avers that the history of the individual repeats the history of the race. Similarly, if unassisted by the experience of others, each SUCcessful engineer would perfect and develop his methods and technique from the rough grab sample up to the carefully taken, recorded and studied samples and observations which now determine and decide the expenditure of the large sums required for modern mining. Hence real progress results from the interchange of experience, as in that way the entire experience of the profession can be made available to every engineer. The literature of this subject is already voluminous, but some progress has been made in the gathering of data and in their compilation or presentation. More Romance than Developed Ore in Limestone Deposits In certain types of deposits, methods little known 25 yews ago have been developed, perfected and standardized to a degree that lifts sampling from the field of manual labor to the plane of an applied science; for instance, the modern methods of estimating the so-called porphyry coppers. With some types of orebodies, we have become familiar, and sometimes on too easy speaking terms, with millions of tons of ore in reserve and tens of millions of dollars; while with others even these once marvelous figures sink into insignificance before the array of ciphers that are presented. .In such company, the average limestone replacement orebody is entirely out of place, for its reserves seldom reach a figure to arrest the attention of the modern engineer, and more often are insignificant. It is only when the records of the production of some of the older camps are studied, which show them to have continuously produced over very extended periods, that a realization is borne home that occasionally this type is worthy of consideration even in these days of gigantic tonnage.

Jan 1, 1925

By Holbrook G. Botset

Experiments performed in this laboratory on the flow of gas-liquid mixtures through unconsolidated sands have been described and discussed in an earlier paper.4 In these earlier experiments a definite relationship was found between the liquid saturation of a sand and its permeability to the liquid or gas phase. Furthermore, the nature of the sand, the permeabilities of the sands over a range between 17 and 260 darcies, appeared to have a negligible effect upon the saturation-permeability relation. Likewise experiments indicated that the viscosity of the liquid, or the substitution of an immiscible liquid for the gas phase, had only a very slight effect on the permeability-saturation relation. This conclusion has since been definitely confirmed by the experiments of M. C. Leverett3 on the flow of oil and water through unconsolidated sands. The sands used by Leverett were of very low permeability (between 6.8 and 1.04 darcies), while the oil-water viscosity ratio varied between 90 and 0.057. Since the sands that constitute petroleum reservoirs are largely consolidated, although of widely varying degrees of consolidation, it was desirable to extend the experiments on gas-liquid mixtures to consolidated sand. In the study of consolidated sands additional variables are involved, but for the initial experiments the only new variable to be introduced was the cementing material. Experimental Procedure A comparatively limited assortment of sandstones was available for the selection of the experimental material. Of these, the Nichols buff sandstone appeared to be most suitable. It gives no visual evidence of any bedding planes, it has a firm structure, permitting easy handling, and its permeability is about 0.5 darcy. Its only disadvantage is the fact that it contains an appreciable amount of ferric oxide which, for experiments involving water, will hydrate and reduce the permeability. This

Jan 1, 1940

By J. N. Hummel

The methods of electrical prospecting, which employ contact electrodes to produce an electric field in the ground, furnish information concerning the constitution of the material beneath the surface, as indicated by the distortion of this artificially produced field and anomalies therein. To reveal the distortion of such field of known character, it is only necessary to measure qualitatively the direction of the field, using sensitive compensation methods. In such a case, the survey is relatively simple, and that is an important factor from a practical point of view. The distortion of the normal field thus determined permits an easy interpretation and gives approximate information as to the subsurface conditions, without the necessity of a thorough theoretical knowledge of the electrical field. The true field of application of the equipotential lines and search-coil methods, which are based on this principle of directional determination of the electrical field in the ground, is that of search for deposits of economic minerals for the mining industry, although they can also be used in solution of other problems; for example, in the determination of the strike of anisotropic beds. The distortion of the electric field as represented by the picture of equipotential lines or other measured curves is striking only when bodies having conductivities different from that of the country rock are embedded in the underground, or when the underground is anisotropic. It is obvious that methods based on such a simple principle and capable of solving directly many of the practical problems of mining geology have found a widespread application. However, these methods are unable to furnish any information as to the presence, depth and physical properties of layers in the underground, which have different conductivities, but are parallel, or only slightly inclined, to the surface. Where such conditions exist in the underground, the picture of the field

Jan 1, 1932

By Holbrook G. Botset

Experiments performed in this laboratory on the flow of gas-liquid mixtures through unconsolidated sands have been described and discussed in an earlier paper.4 In these earlier experiments a definite relationship was found between the liquid saturation of a sand and its permeability to the liquid or gas phase. Furthermore, the nature of the sand, the permeabilities of the sands over a range between 17 and 260 darcies, appeared to have a negligible effect upon the saturation-permeability relation. Likewise experiments indicated that the viscosity of the liquid, or the substitution of an immiscible liquid for the gas phase, had only a very slight effect on the permeability-saturation relation. This conclusion has since been definitely confirmed by the experiments of M. C. Leverett3 on the flow of oil and water through unconsolidated sands. The sands used by Leverett were of very low permeability (between 6.8 and 1.04 darcies), while the oil-water viscosity ratio varied between 90 and 0.057. Since the sands that constitute petroleum reservoirs are largely consolidated, although of widely varying degrees of consolidation, it was desirable to extend the experiments on gas-liquid mixtures to consolidated sand. In the study of consolidated sands additional variables are involved, but for the initial experiments the only new variable to be introduced was the cementing material. Experimental Procedure A comparatively limited assortment of sandstones was available for the selection of the experimental material. Of these, the Nichols buff sandstone appeared to be most suitable. It gives no visual evidence of any bedding planes, it has a firm structure, permitting easy handling, and its permeability is about 0.5 darcy. Its only disadvantage is the fact that it contains an appreciable amount of ferric oxide which, for experiments involving water, will hydrate and reduce the permeability. This

Jan 1, 1940

By G. B. Pryde, R. M. Magraw

In laying out a new mine, provision should be made for the ultimate recovery of as much coal in any given bed as is consistent with safety and economic mining. Though each mining district, if not each individual mine, has problems that make the adoption of any hard and fast rule impossible, certain basic principles are adapted to practically all conditions. One of the most vital is the provision for barrier pillars of ample dimensions to protect all haulage and permanent airways during the life of the property. Where conditions permit, room or butt entries should be driven on the strike or slightly to the rise, and rooms turned at right angles to these entries. The width of rooms and room pillars is governed by conditions prevailing in the mines under consideration. A safe rule is: In advancing, extract not more than 25 to 35 per cent. of the entire seam; in exceptionally thick seams, considerably less than 25 per cent. should be taken. Rooms usually vary in length from 250 to 350 ft. (76 to 106 m.) with a barrier pillar of not less than 80 ft. between the last crosscut. in rooms and the back entry of the level above. All entries, rooms, and entry-and-room crosscuts should be driven .on sights and room crosscuts should be driven at, right angles to the direction of the rooms. In mines under excessively heavy cover or where roof conditions are bad, rooms should be driven narrow and a barrier pillar left at every fifth to tenth room. This barrier should be of such dimensions that one or more rooms, with pillars of usual dimensions, may be turned through it when the barrier is no longer required. Two of the advantages of such a barrier are the protection of the panel against peaking of roof load during pillar extraction and the easy closing of the entry in case of fire. Where economic conditions permit, it is preferable to follow the retreating panel system of mining. In the case of coal that outcrops, and even in cases where no outcrop is exposed, it is preferable to commence pillar extracting on the high side of the mine. Where the retreating

Jan 1, 1922