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By C. M. Tucker, K. R. Van Horn, W. P. Sykes

Recent investigations of the molybdenum-carbon alloys have been reported by Becker and Ebertl,‡ Westgren and Phragmén2, T. Takei3, and H. Tutiya4. Takei3 studied the Mo-C system by employing metal-lographic and X-ray methods, and the other publications described the determination of the crystal structure of the molybdenum carbides. In exploring this system by a technique previously applied to the tungsten-carbon series5, the results of Takei were confirmed with two definite exceptions; i.e., first the composition of the eutectic, and second the nature of the carbon-rich intermediate phase. Consequently, a more thorough examination of the molybdenum-carbon constitution was initiated in an effort to correlate the data supplied by the microstructures, diffraction patterns and chemical analyses. Metallographic Investigation A briquette of molybdenum powder when heated in a carburizing atmosphere at 1500" to 1600" C. for several hours develops the carbon-rich layer shown in Fig. 1. The carburization was accomplished by placing the briquette in a carbon tube, which was heated in the hydrogen atmosphere of an alundum muffle wound with tungsten resistor. While the macrostructure indicates two distinct shells, and suggests the possibility of two carbon-rich phases, no evidence of this condition could be detected by the microscope, which revealed but one high-carbon constituent. This carbide forms next to the molybdenum as a relatively dense, light-colored zone (Fig. 2) which passes abruptly into an outer layer of spongy texture. As will be noted later, only one intermediate phase was observed in the X-ray photograms prepared of different locations in the carburized zone. The metallographic structure at the inner border of the shell, reproduced in Fig. 3, shows a marked porosity accom-

Jan 1, 1935

By Theodore B. Comstock

a. Boundaries of the District.—The district here considered comprises that portion of Colorado commonly known as " the San Juan Country." In order to bring the principal geological features of this region within the scope of a map of convenient dimensions upon a suitable scale, I have found it desirable to mark off boundaries near the parallels of 37O and 38O 10', and the meridiaus of 106' 30' and 108' 30' (West Longitude from Greenwich). This area of (approximately) 9400 square miles includes all the formations which we should have to discuss if our territory were greatly enlarged, excepting such as are distinctly characteristic of adjoining areas with independent orographic genesis. By limiting this review to these confines we miss very little of the geology of the eight counties of the San Juan region, viz.: Dolores, San Miguel, Ouray, Hinsdale,

Jan 1, 1887

By Carl Benedicks

IT is well known by every one who has had to deal with boiler tubes that these are often seriously affected by a sort of corrosion, occurring as a local pitting, that frequently causes a perforation of the tube in a rather short time. The characteristic appearance of this corrosion is shown in Fig. 1. A very similar corrosion occurs in condenser tubes (Fig. 2).1 A study of the microstructure or local chemical composition of the metal (iron; 70 :30 brass) fails to reveal any cause for this pitting. Of course one might possibly assume the starting point-to be some oxide particle, causing an electrolytic local action, but this in no way explains the continued corrosion, progressing even when the assumed oxide particle must have disappeared. By the excellent work done by the Corrosion Research Committee of the Institute of Metals, and communicated, in October, 1923, to the Institution of Engineers and Shipbuilders in Newcastle-on-tyne, stress was laid on the fact that a content of entangled air has a very obnoxious effect. In the following correspondence, Sir George Goodwin stated that "engineers have, for a long time past, regarded air as the big enemy to be fought against in all questions of corrosion"2 and Kenneth Fraser pointed out that the most vital point is "the avoidance or removal of possibly the chief cause of present day corrosion, i. e. entrapped air and gases brought out of solution."' In their reply, however, the authors state that they had "never for a moment believed that entangled air was responsible for the beginnings of corrosion, and express the opinion that the gradual liberation of air could not account for localized corrosion."4 On consulting the many textbooks on corrosion, as that

Jan 4, 1925

By Arthur F. Wendt

Introduction.—In the year 1885, the writer signed a contract to take charge of the reopening and developing of the celebrated old mines of " El Cerro Rico de Potosi." Two years earlier, an Eng- . lish firm of engineers had made a very glowing report on the property. In the summer of 1885, telegrams arrived from the parties in charge of operations at the mountain, claiming the finding of one of the old veins, with an average richness of over 200 ounces to the ton. In the fall of 1886, the author first personally visited Potosi, but found neither the English report nor the telegram borne out by the facts. After an expenditure of over half a million of dollars and more than three years of continuons hard work, the writer succeeded in unwatering and developing one of the principal old veins of the mountain. This vein, called "Cotamitos," now yields ores of about 75 ounces to the ton, and the old historic mountains of Potosi may be said to have again fairly entered the list of silver-producers. The experience of the author, during his residence in Bolivia, and data obtained from Sr. Don F. Avelino Aramayo, form the basis of this description. POTOSI. Etymology of the Name.—The Quichuá (pronounced Keechna) Indians, known to North American students as the " Incas," although the word "inca" merely signifies ''king," or "chief," of the Quichuás, called the mountain "Sumac-orcko," or the beautiful mountain." Eighty-three years before the discovery of the mountain by the Spaniards, the inca, or king, Huaina Ccapac, travelling from Cantumarca to Calque-Porco, saw the mountain of Potosf and, admiring its grandeur and beauty, said that within its bowels there was, no doubt, much silver. He ordered his vassal* to work the mines. They, having carried their mining implements to the mountain, ascended it and were on the point of commencing work, when they heard a voice of thunder, which said: " Do not take

Jan 1, 1891

By Paul Billingsley

THE mining districts of the first and second order1 of the western United States (and borders) are those named on Fig. 1. These fall into four groups: (1) in the eastern outliers of the Rocky Mountain system; (2) in the Rocky Mountain system itself; (3) in the Great Basin; and (4) in the Sierras and Coast ranges. Of these four groups, the first three are almost entirely of Tertiary age and are within a belt of Tertiary compres-sive folding which we shall call the Rocky Mountain-Great Basin thrust arc. The backbone of this belt is shown by the line BAC. The position of the ore districts in this belt indicates a conformance to linear elements of the continental pattern. These are additional to the peripheral elements emphasized by Butler.2 NATURE OF THE THRUST ARC The thrust arc separates regions of contrasted kinds. To the east of it are flat-lying plateaus interrupted by earlier mountain folds; to the west, sunken basins, in which block-faulted ranges lie like an anchored fleet in a sea of desert wash or lava. The cross-sections are as shown in Fig. 2.

Jan 1, 1933

By R. C. Ferguson, Harlowe Hardinge

Laboratory and plant data covering 12 different operations show that lower than "standard" ball mill speeds increase grinding efficiency. In the case of high pulp-level mills, the gain is so great that the increase in capital cost of the larger lower speed mill will pay for itself in less than a year's time. THE object of this paper is to show the economic advantage of operating ball mills at relatively slow speeds. Although many operators know that grinding costs are reduced by operating mills at low speeds, they seldom do so for a variety of reasons. When capital is limited, first cost is of primary importance, and installation of the less costly, highspeed mill is favored. When materials are in short supply, as during a war period, capacity rather than economy is the primary consideration. Existing mills are then speeded up to provide the desired increase in capacity, and new mills are purchased without consideration of maximum grinding efficiency. When the mill speed is increased to secure more production, the increase in grinding costs is often obscured by the total benefit derived from the additional output. This increase in grinding cost is seldom recognized as being sufficient to be worth correcting. For these reasons one may be lead to the erroneous conclusion that slow-speed operation is only occasionally applicable. The effect of mill speed on grinding efficiency has been studied in laboratory tests."! The results of some of these tests are given in tables I and I1 and fig. 1. In these tabulations, batch tests using ore charges of 125 to 200 lb were considered comparable to high pulp-level operation and charges of 50 to 100 lb comparable to low pulp-level operation. For the high pulp-level operation, these tests indicate the existence of a maximum in efficiency for operation at a speed of 50 pct of critical, both for the soft (dolomite) and hard (chert) ore. In low pulp-level operation, a decrease in speed increases the efficiency of grinding dolomite; no maximum of efficiency appears in the range of speeds tested. The results with chert were inconclusive. If the performance of large mills is indicated

Jan 1, 1951

By Harlowe Hardinge, R. C. Ferguson

Laboratory and plant data covering 12 different operations show that lower than "standard" ball mill speeds increase grinding efficiency. In the case of high pulp-level mills, the gain is so great that the increase in capital cost of the larger lower speed mill will pay for itself in less than a year's time. THE object of this paper is to show the economic advantage of operating ball mills at relatively slow speeds. Although many operators know that grinding costs are reduced by operating mills at low speeds, they seldom do so for a variety of reasons. When capital is limited, first cost is of primary importance, and installation of the less costly, highspeed mill is favored. When materials are in short supply, as during a war period, capacity rather than economy is the primary consideration. Existing mills are then speeded up to provide the desired increase in capacity, and new mills are purchased without consideration of maximum grinding efficiency. When the mill speed is increased to secure more production, the increase in grinding costs is often obscured by the total benefit derived from the additional output. This increase in grinding cost is seldom recognized as being sufficient to be worth correcting. For these reasons one may be lead to the erroneous conclusion that slow-speed operation is only occasionally applicable. The effect of mill speed on grinding efficiency has been studied in laboratory tests."! The results of some of these tests are given in tables I and I1 and fig. 1. In these tabulations, batch tests using ore charges of 125 to 200 lb were considered comparable to high pulp-level operation and charges of 50 to 100 lb comparable to low pulp-level operation. For the high pulp-level operation, these tests indicate the existence of a maximum in efficiency for operation at a speed of 50 pct of critical, both for the soft (dolomite) and hard (chert) ore. In low pulp-level operation, a decrease in speed increases the efficiency of grinding dolomite; no maximum of efficiency appears in the range of speeds tested. The results with chert were inconclusive. If the performance of large mills is indicated

Jan 1, 1951

By H. L. Hollis

The paper read by Mr. George J. Snelus, in 1894, before the Iron and Steel Institute of Great Britain* so fully and ably described the Walrand-Leghisel process that there remains very little to add beyond recording some changes in practice, made since that date, and observed by the writer last summer, at several continental works, and the further fact that the process has now been for some time in successful operation in this country. Briefiy stated, the Walrand-LegBnisel process is an addition to the Bessemer operation, with the object of obtaining quiet and more fluid steel, and consequently sound castings and ingots. This is achieved by adding ferro-silicon at approximately the time of flame-drop in the ordinary Bessemer operation, and making an after-blow. The high calorific power of silicon is well known, and the rapid combustion of it immediately before

Jan 1, 1897

By G. Willard Quick

TENSILE tests of rail steels at elevated temperatures'' have shown that certain rails, in addition to having low ductility in the well-known bluebrittle range in the neighborhood of 200° C., have marked reduction in elongation and reduction of area in the temperature range from 400° to 700° C. This range of low ductility was called "the secondary brittle range" and the phenomenon, "secondary brittleness." The question naturally arises as to whether this property of the steels would be shown by impact tests performed in the same range of temperature. If so, the impact test, as suggested by Gillett3 would be a simpler and quicker method for the routine examination of steels at elevated temperature than the tensile test. A number of investigators have reported results of impact tests on steels at elevated temperatures, in which the energy absorbed decreased with increase of temperature above 200° or 300° C. Langenberg4 performed Charpy impact tests on several steels at temperatures ranging from room temperature up to 1000° F. (538° C). His results showed an increase in the energy absorbed in specimens tested in the range from room temperature to 200° or 300° C. and then a gradual decrease in the range, 300° to 538° C., the maximum temperature used. Greaves and Jones5

Jan 1, 1932

C. W. WASHBURNE, New York, N. Y. (communication to the Secretary *).-We are indebted to Mr. Pack for his detailed description of a rapid method of estimating the oil reserves in large fields. Although his method will give only a rough approximation of the reserves, nevertheless it is much more reliable than the saturation method. The saturation method should not be used when any other method is available. The paper describes a generalized method, which is especially useful in estimating the total resources of a Nation or State. Properly it is a method of estimating the oil that can be extracted by common methods within a given period of time. It does not account for

Jan 10, 1917

By D. W. Jessup

ONLY during the past few years, have the old-fashioned methods for treating ores and byproducts progressed to any marked degree. The advent of multiple-hearth roasting, blast roasting, the baghouse, and the Cottrell plant indicate this change. It is the ability to roast and smelt sulfide ores and concentrates that gave this later advance. Further investigations that will solve the problem of efficient handling of flotation concentrates and their attendant ills are of the utmost importance. With future developments, the metallurgist will be able to smelt more economically and to treat still more refractory ores, making the early methods appear small by comparison. GROWTH OF SMELTING Well within the memory of pioneer smeltermen, the ore was charged directly into the blast furnace as it came from the mine;, only the richer, ores were smelted, the lower grade and sulfide ores were undesirable. Matte was, at first, thrown away and only two products) were desired-slag and lead bullion. Scores of the early smelting companies failed because of improper reduction of ores, high costs, short- furnace campaigns, inability to treat sulfide ores, and ores containing-zinc. With the failure of weaker companies, consolidation eliminated many others, until today the field is dominated by a comparatively few organizations, each strong financially. Formerly, a few thousand dollars would erect a small plant, whereas the modern smelter costs over a million dollars. Ore and products to which formerly no attention was paid are now treated with comparative ease and at a good profit. Mechanical improvements have modernized smelting, furnace tonnages show an increase, and metal recoveries have made enormous strides. Even though costs have decreased, they have not dropped in proportion to the improvements, because of the higher wages, greater costs of fluxes and coke, more undesirable ores smelted, etc.

Jan 8, 1925

W. McA. JOHNSON.-My idea is simply that a very large excess of coal is ordinarily used as the reducing Material in a zinc charge.. By fine-grinding you increase the surface, and by adding some agent like sawdust or small pieces of wood, or cotton stalks, the charge is made porous., However, the fineness of the ore and of the coal makes the charge, a very poor conductor of heat, and therefore it has to be briquetted. 0. C. RALSTON, Niagara -Falls, N. I'.-The present large, tonnage of flotation concentrate handled by the zinc smelters is often a considerable embarrassment -to them. Nearly all of them complain of the great amount of flue-dust formed during the roasting of this material. This would suggest that it is necessary to briquette, or otherwise agglomerate flotation concentrate before it is .placed in the roasting furnace, although Mr. Johnson's particular proposal merely involves briquetting after

Jan 4, 1918

JESSE L. JONES,* Pittsburgh, Pa. (written discussion?).-As the die-casting process is so very different in character from the process of making sand molds, it is often considered that entirely different methods of pouring, gating, venting, etc. should be used. There is really, however, no essential difference in the making of (lie castings and sand castings, and similar methods should be used in each process. In the matter of gating, the metal should be introduced at a central point, as nearly as possible, so that it will have an equal distance to flow from the point of entrance to the most distant points of the mold. This will cause a uniform rate of congealing of the casting and prevent streaks and cold shuts. The venting should be done in such a way that a free exit of the air in the molds can occur. It should be less difficult to take care of the venting of a die-casting mold than to vent an ordinary sand mold. In the case of a sand mold, the venting is left, to a considerable extent, to the judgment of the molder, and it is possible that no two molds will be vented in a similar manner. Further than this, after a vent has been made in a sand mold, it may become clogged by the sand and for this reason be inefficient. There is also quite a variation in the pressure of the metal entering a sand mold, due to varying heights of the pouring gate. In a die-casting mold these factors can be controlled more closely. The vents should be so disposed that the air in the mold compressed by the entrance of the metal may be able to leave the mold at a uniform rate and by exits located symmetrically. These exits are made quite small on molds at first, as they can he easily enlarged if necessary, and they are tapered so that a free flow is guaranteed without danger of the metal spurting out from the die. Uniformity of pressure of the metal as it enters the mold is very important and, as the pressure is mechanically applied, its control is not difficult. It is true that a sand mold has much less of a chilling effect on the metal poured into it than has the die-casting mold, but, outside of this point, there is a great similarity between the die-casting process and the process of making castings in sand folds. It is suggested that much would be gained by regarding these two processes as not essentially different.

Jan 4, 1919

By T. A. Rickard

The lodes of Cripple Creek, Colo., partake of the composition of the geological formation which they traverse. The prevailing rocks are andesitic breccia, lying upon granite, and also bodies of phonolite, trachytic phonolite, nepheline-basalt, etc., penetrating both the granite and the breccia. At Kalgoorlie, in West Australia, the prevailing rock is schistose, and has not been certainly identified, though microscopic sections indicate the probability that it was originally an acid eruptive. The lodes are essentially bands, more highly schistose than the encasing rock, and impregnated to a notable degree with disseminated pyrites and secondary calcite. During 1899 Cripple Creek produced 425,590 tons of ore, having a gross value of $15,658,254; during the same period the output of Kalgoorlie was 467,048 tons, valued at $17,724,587. In chemical composition, the ores at Cripple Creek and Kalgoorlie, respectively, present differences equally interesting to the petrographer and the metallurgist. In both cases we have to deal with altered eruptives as the matrix of the ore; but the much older rock of Kalgoorlie has undergone more decompo-

Jan 1, 1901

By M. S. Hunter, D. L. Robinson

An extremely fine subgrain structure found in aluminum and aluminum alloys is shown and a method for revealing this structure is described. The appearance and some of the characteristics of this structure are described and the possible significance of subgrain structure in terms of chemical, electrochemical, and metallurgical processes is considered. GRAINS and grain boundaries, which constitute the principal manifestations of the crystalline aggregates known as metals, play such an important part in determining the characteristics and properties of metals and alloys that their nature and behavior have long been of much concern to the met-allographer. Many investigators have speculated on the possible existence of a finer structure within the usual grain structure and, through X-ray diffraction and metallographic techniques, have revealed evidence that such finer structures exist. Among these structures are the mosaic blocks and domains described by Burgers1 and others in their contributions on crystalline structure and the dislocation theory, the small units associated with polygoniza-tion described by Cahn,2 and the intragranular blocks revealed more recently by Lacombe and Beaujard.3 his paper describes some novel methods for clearly revealing a very fine granular substructure within the usual grains of pure aluminum and aluminum alloys. It also compares the characteristics and behavior of this subgrain structure with those of the ordinary grain structure and gives some examples of the manner in which this substructure may influence the characteristics of aluminum alloys. Metallographic investigations of aluminum and its alloys have dealt extensively with the functions and behavior of grains and grain boundaries and have evolved a definite concept of the relation between grain structure, orientation and physical, mechanical, chemical, and electrochemical behavior. During the examination of etched samples, a roughening or mottling of the body of certain grains has occasionally been observed. Such roughening obviously represented differential attack by the etching solution, but its true significance was not at first realized. It is now known that this roughening probably rep- resented a subgrain structure, although the particular etching treatments used were not capable of revealing this subgrain structure clearly. Also, in practically all cases, the subgrains were apparently far too small to be resolved by the light microscope. Recently, a method has been developed for revealing clearly the subgrain structure of most aluminum alloys. This method is somewhat unique in that it eliminates much of the usual tedious mechanical polishing and the attendant danger of a surface layer of flowed metal and at the same time is simple, rapid, and effective. It involves the use of the Alcoa R5 Bright Dip, a patented chemical polishing treatment licensed by Aluminum Co. of America. This treatment produces a bright, highly polished surface at least the equal of any mechanical polish and also etches the subgrain boundaries as well as the ordinary grain boundaries to reveal both the grain and subgrain structure simultaneously. Metallographic specimens to be examined are taken through the customary grinding and polishing operations used for aluminum alloys.' The usual care required in the final polishing operation to prevent a flowed surface layer and to obtain a high polish is not necessary, however, because any flowed layer is eliminated and a high polish is produced by the final immersion in the Alcoa R5 Bright Dip. Depending on alloy type, this dip takes from a few seconds to about 3 min, after which the sample is rinsed well, blown dry, and is ready for examination. The substructure can be revealed by some of the usual metallographic methods such as electropolish-ing or mechanical polishing and etching but no method has been found which is the equal of the new chemical polishing treatment. Mechanical polishing followed by the usual metallographic etching is not entirely satisfactory for revealing this substructure, probably because of the flowed surface layer resulting from the mechanical polish. If the usual etching methods are prolonged sufficiently to remove this layer, the specimen surface becomes quite rough and the substructure is not defined clearly.

Jan 1, 1954

By H. C. Fiedler

SILICON-IRON strip with a cube-on-edge secondary recrystallization texture is made commercially as thin as 10 mils. With inclusions present to inhibit normal grain growth, a few grains, and these have the (110)[001] orientation, grow very large at the expense of the matrix grains. In the absence of inclusions, only normal grain growth occurs and the texture is not as strong as when it is developed by secondary recrystallization.1 Strip for use at frequencies of 400 cps and higher is made in thicknesses of 1, 2, and 4 mils by a process developed by Littmann.2 Attempts to develop a strong texture in these thin gages by the same methods as were used for the 10 mil and thicker strip were unsuccessful,2 and Littmann's solution to this problem was to cold roll the grain

Jan 1, 1963

By M. S. Tsai, Y. D. Chuang, H. M. Wu

To contact the commercial OPAP-kerosene solution with CH3OH – H20 solution, we used the appropriate concentration of DOPAP / MOPAP solvent. By using this treated OPAP solvent, uranium can be recovered from wet-process phosphoric acid. Electric DC power is supplied on the dual side of the ion-exchange membrane of a specially designed box-type mixer settler. U(VI) is reduced to U(IV) in the cathode and U(IV) is oxidized to U(VI) in the anode. Uranium is extracted in the cathode by treating it with OPAP solvent. Next the uranium is stripped from the loaded OPAP solvent by concentrated phosphoric acid in the anode. After 300 hours of continuous operation total recovery of uranium is as much as 95%.

Jan 1, 1984

By P. Barnes

The complete and uccurate filtration of water (if the word accurste map be thus Used) for the feeding of boilers, and for many similar industrial purposes, although somewhat practiced both at home and abroad, has heal by no means common. Even if the exact line cannot be defined at which filtration begins to be called for, ad will be found profitable, it is certain that in a large number of cases it may be employed with real advantage in the economy of fuel, and also in the greater durability of the boiler or other form of apparatus in

Jan 1, 1882

Discussion of the paper of G. P. Hulst, presented at the Salt Lake meeting, August, 1914, and printed in Bulletin No. 92, August, 1914, pp. 1865 to 1871. L. S. AUSTIN, Salt Lake City, Utah.-One question that I would like to ask is in regard to the sampling kettle which stands beside the softening furnace. How is the sample taken or melted? G. P. HULST.-The sampling kettles in question are of 45 tons capacity and are fired with coal. The lead bullion comes in on a high line in car-load lots of 30 to 40 tons. The entire lot is trucked from car, weighed over scales and thrown into the sampling kettle, which has been previously cleaned. The kettle is fired and the bullion melted, then heated up until no frozen bullion' remains in the .bottom or adheres to the sides of the kettle. The kettle is scraped clean, sides and bottom, and the wet dross is skimmed Doff clean into molds. The kettle is stirred thoroughly during the period in which 24 to 30 samples of approximately ½ assay ton are taken. These samples are taken in a long-hand loci iron mold, providing for taking six to eight "gumdrops." The mold is inserted and heated to the same temperature as the molten metal, and gumdrops are clipped out and cooled in the mold by dipping 'the bottom of. the mold into Water. The samples should be free from fins. The gumdrops represent the contents of the kettle, and in assaying, they should not be clipped, but weighed up and the result computed. The dross bars are weighed and sawed according to old hammer and punch sample template. The sawdust represents a sample of the dross. In eases of high gold in the bullion there is a slight correction in the assay. This method of sampling was developed at the Omaha plant of the American Smelting & Refining Co., W. T.. Page, Manager, in 1903 or 1904, for adjusting differences in checking smelter sampling. L. S. AUSTIN.-The base bullion which you treat is very clean. It has been remelted, and skimmed before shipment. How rapidly can you get it through the softening furnace, and how does it compare with ordinary base bullion? G. P. HULST.-Twenty-four hours is the softening limit on these charges. In other words, it is charged into the furnace, heated up, and the first and second skimmings are taken off, and it goes into the kettle the next day; that is, 24 hr. elapse from the time the bullion is charged to the time it is in the kettle. L. S. AUSTIN.-It seems to be a long time to hold such a pure bullion. I suppose, though, it comes around conveniently so that you have a time for all the other operations of refining. Isn't that the case? MR. HULST.-Every refinery is based on those principles.

Jan 11, 1914

By Chester W. Washburne

At present it is impossible to estimate closely the amount of oil obtainable from a given area of land. However, after the completion of a few properly distributed prospect wells, one can calculate the approximate yield of the sands penetrated, with a probable error of say 50 per cent. Even rough predictions of this kind are of value in large operations. Without wells upon it, one can never be absolutely certain that an area will produce any oil whatever, and one can only indulge in wild guesses of the probable productive area, before the geological structure has been carefully contoured and the top of the basal water plotted on a map. This requires wells. At times it is desirable to form an idea of the possible yield of oil in advance of drilling, as in cases where the price asked for undeveloped land seems too high, but where the probability of finding oil is furnished by neighboring development, supported by the geology. In such cases the most one can do is to make an estimate of possible maximum yield, which may of course far exceed results, and which is of use mainly in the prevention of excessive initial investment. The method is very significant in a general way, as in regions like the Bighorn Basin, Wyoming, where the productive sands in the Cretaceous shale are so few and so thin and fine that they cannot develop very great production, although the high quality of the oil probably will counterbalance this defect sufficiently to give local profit in favorable areas. Reservoir Capacity of Sands.—The porosity of a stratum is the measure of its maximum reservoir capacity for liquids and gases. The porosity may be determined experimentally and must be used in connection with the total volume of the sand.

Jan 1, 1915