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By John R. Gould

A mathematical treatment of multiple-pass floating-zone refining of semiconductors, including the evaporation of solutes from the melt at reduced pressure, is presented. Vapor pressures and evaporation rate constants for phosphorus, arsenic, and antimony in germanium have been determined from floating-zone experiments conducted at 10 mm Hg. Rate sensi-tivity of arsenic in germanium has been examined over the range of 1 to 10 in. per hr growth rate. The equilibrium value of the segregation coefficient of arsenic in germanium, as determined by an extrapolation of these data, was found to be 0.09. PFANN has treated the segregation of nonvolatile solutes in the zone-melting process, Bradshaw and Mlavsky2 considered the evaporation of solutes in a vacuum during the growth of crystals by pulling from the melt, and van den Boomgaard3 has shown that it is possible to bring a volatile impurity element homogeneously into an ingot by means of zone-melting under a constant pressure of that element. This paper is concerned with the volatilization of solutes during zone - melting in a vacuum. The mathematical analysis by Lord4 of multiple-pass zone melting is extended to include evaporation of solutes. A method is presented in which evaluations of vapor pressures, evaporation rate constants, and distribution coefficients may be derived from the variation of solute concentration in the floating-zone refining of germanium at 105 mm Hg. EXPERIMENTAL Ingots of zone refined germanium, approximately 1/4 in. in diam and 10 to 12 in. in length, were subjected to several floating-zone passes at 105 mm Hg in order to provide intrinsic material for these studies. These ingots were then seeded in a [Ill] direction and solid-doped to a constant impurity concentration of approximately 1015 atoms per cmS in a forming gas ambient (10 pct H - 90 pct A) at 1/2 atm gage. The resulting crystals were subjected to repeated floating-zone passes at 105 mm Hg and a concentration profile along the length made after termination of each pass. Concentrations were determined from four-point probe resistivity measurements, and proper precautions were taken to prevent contamination during handling. A constant zone length, crystal cross section, and growth rate were maintained during zoning. A stationary coil and moving crystal system were employed for floating-zone growth with neither the section of crystal above nor below the melt rotated.

Jan 1, 1962

By J. B. Patton

No academic program of reasonable duration can provide a geologist with all the skills that may be needed for applied work in industrial minerals. However, any curriculum that does not provide background in such basis subdisciplines as mineralogy-petrology, stratigraphy, sedimentology, structure, and geomorphology will leave the practitioner handicapped. Enough geochemistry to understand materials requirements, and sufficient geophysics to use geophysical data, are essential. In addition to purely scientific considerations, the industrial minerals geologist must be able to evaluate economic factors. He may also be faced with legal, social, and political problems in land use, zoning, envil.onmenta1 protection, and reclamation.

Jan 1, 1985

By Henry A. Ley

Kansas ranked fourth on the list of oil-producing states during the year 1930. Progressive statistics show that total production for the year will approximate 42,729,085 bbl. When final figures are compiled for Kansas the production may exceed this estimate, and thereby threaten the all-time record of 43,253,470 bbl. in 1918. Throughout the year the cumulative volume of potential drilled-up production has been increased by new discoveries and by extensions to proven areas in the territory west of the Nemaha (granite ridge) Range. Scattered drilling and leasing operations of a constructive nature occurred, but completions declined to the lowest levels in more than 11 years. Average initial production of current completions climbed to a new all-time high of 512 bbl. to the well. Proration measures were applied to the flush pools. The resulting shut-in potential production, as of December 15, is estimated at 110,000 bbl. This estimate is a wild guess. If all wells of the state were permitted to flow wide open for a period of six months production would not exceed 150,000 bbl. a day. The outstanding development of the year was an intensive drilling campaign in southwestern Kansas, which contributed at least 1,000,000 acres of contiguous natural-gas lands to the natural-gas resources of the United States. Production and Development Prospecting for oil in Kansas began shortly after the initial prospecting at Titusville. Operations and interest in the potentialities became active about 1870. This development was restricted to the shallow districts of northeastern Kansas. By 1895 operations had extended southward to the Oklahoma state line and sufficient prospecting had taken place to prove the potentialities of the state. Active prospecting was extended westward by the discovery of oil on the Nemaha Range in Butler County about 1916. The discovery of oil in Russell County added an extensive borderland province in 1923. The important discoveries of oil in Sedgwick County revived interests and operations throughout this territory in 1928. The development of widespread natural-gas lands in extreme southwestern Kansas during 1930 carried active exploration to the western boundary of the state.

Jan 1, 1931

By W. H. Gauvin, N. J. Themelis

Jan 1, 1963

By J. G. Hall

Introduction When one thinks about world metal economics today, it seems to me he must go beyond the traditional factors such as exploration, discovery, economic feasibility of development, management, labor, and the application of technology. These elements have been and will continue to be very important, of course, in making available the resources that experts believe the world will require during the remainder of this century. There are, however, some new forces as well as new or different emphasis on some of the old factors that could materially affect the development of the world metal mining industries. For example, in my own company two of the most significant considerations affecting our economics today have to do with foreign political decisions and with environmental concerns here in the U. S. -both of which play a far more significant role in our economic considerations than they did as recently as 10 years ago. After a brief look at some historical data and some projections of probable future demands for the world's major metals, I shall then identify and comment upon some of the factors that I believe will have an increasing impact on the future of the economics of our industries. I do not have any magic solutions to the problems we will face; nevertheless, we in the mining industries of the world are going to have to cope with these matters and find satisfactory answers to the problems they will create. The Past Although the age in which we live has been described as the atomic age, the space age and the computer age, we are, in fact, living in a metals age, and we have lived in a metals age for a very long time. The discovery of copper smelting, for example, is placed at about 4000 B.C. Gold was used in a primitive way before that. Other metals - lead, silver, tin, iron and mercury - were discovered and used before 2000 B.C. In all probability, we will be dependent upon metals beyond the vision of anyone living today. In industrialized nations of the world, man's mode of living is based to a great extent on metals, and it is extremely unlikely

Jan 1, 1971

By J. Chipman, J. C. Fulton

Reduction of silicon from blast-furnace-type slags by carbon-saturated iron is a very slow reaction even under conditions of rapid stirring. Equilibrium under atmospheric pressure of carbon monoxide was approached from both sides, and the silica-silicon relation was established at temperatures of 1425º to 1700°C for slags containing up to 20 pct Al2O3. Silicon carbide is formed by reaction of graphite with high silica slags and the conditions for its formation were determined. Activities of SiO2 and of CaO in their binary solutions at 1600°C were determined. The effects on the activity of SiO2 were established for additions of 10 to 20 pct AI2O3 and of 10 pct MgO. STUDIES of chemical reactions between blast-*>-5 furnace slags and metal have been focussed on the transfer of sulphur from metal to slag. The important role which silica reduction plays in this process' has led to a study of the transfer of silicon from slag to metal and the equilibrium represented by the equation SiO2 (in slag) + 2C (graphite) = Si + 2CO (g). [I.] The authors2 have published an account of the experimental method employed in attacking this problem and of three series of experimental results at 1600°C. This paper contains data on some additional compositions and extends the observations to cover the temperature range 1425° to 1700°C. The data are used to determine the activity of silica in the slags. As in the earlier experiments, the atmosphere was carbon monoxide which flowed through the furnace at 150 ml per min. In certain heats designated in the tables and figures, the gas was bubbled through the melt using a graphite tube. The latter increased in porosity during a run and in some cases bubbling ceased as indicated by cessation of surging. Some results were discarded for this reason. Experimental Results The new data are shown in Tables I through V and both old and new data are plotted in Figs. 1

Jan 1, 1955

By W. D. Douglas, M. J. Hampshire, G. J. C. Young

This paper describes the replacement of a conventional filtration, clarification, and zinc precipitation plant by a carbon-in-pulp (CIP) electrowinning plant, with the objective of improving the recovery of gold from cyanide leached, acid plant calcines. The discussion covers early laboratory studies to the design and erection of the full-scale plant. Particular emphasis is placed on the problems encountered with commissioning and the strategies employed to solve them.

Jan 1, 1985

By Alan Lawley

AS part of a programme of experimental work on single crystals of rhenium and ruthenium, it was found necessary to have the crystallographic angles for these elements. The angles given in Table I were determined to the nearest minute of arc, by Univac Computer. The angle $ between (HKIL) and (hkil) is given by the formula: The angles given for rhenium should be particularly useful in view of the increasing interest in this element. For completeness, angular values are also given for cadmium zinc and magnesium; these form a more complete set of values than those given by Salkovitz.' The assistance of Professor J. Hobstetter and Mr. J. Crozier in the programming of this data is acknowledged. The work is sponsored by the Office of Naval Research under contract No. NONR 551 (19).

Jan 1, 1961

several days before leaving Buffalo; influenza developed, and when his train reached Nashville, Tenn., he was too ill to continue his journey and was taken to the Kissam Hall Hospital, Vanderbilt University, where he died of pneumonia. He was a young man of unusual ability and high moral character, always brigh.t, happy and kind, faithful and honorable in all things; loved by both his associates and those under his authority. His life and character cannot be better described than by the following quotation from one of his superior officers: "Lieutenant Ohnsorg was a man loved by all of us, always cheerful, just and kind, with unusual executive ability. We can never expect to find a man who has his ability and fine temperament and his position can never be sled as he filled it." He was happily married and leaves to mourn his loss a wife, Constance E. (Rogers) Ohnsorg and a baby girl born since his death, Nov. 29, 1918, a father, W. H. Ohnsorg, mother, Ida May Ohnsorg, and a sister, Mrs. Stuart Strathy McNair. He was a member of the American Institute of Mining Engineers and of the Florida Phosphate Miners' Association. Lieutenant Edward Hale Perry At the height of the first great German'offensive -of'the Spring of 1918, Edward Hale Perry, of Boston, First Lieutenant, Company D, Sixth Regiment Engineers, U. S. Army, was killed on March 30, near War fusee—Aban-court, Picardy, France, while defending the Boisdes Tailloux against the terrific plunge aimed at Amiens. Lieutenant Perry was born in Boston, Jan. 23, 1887, the son of Georgianna W. and the late Charles F. Perry. After completion of his college preparatory course, he travelled for a year in South America and Europe before entering Harvard with the class of 1910. It might have been regarded as the natural thing for Perry, upon graduation, to choose a path that would lead to a business or professional career at home, but there were in his character a solidity, a horror of sham, a contempt for the "soft" things, and a love-of the open which caused him to be attracted to a life of stern and sturdy reality. Accordingly, he entered the graduate mining school at Harvard, and received the degree of Mining Engineer in 1913. In the meantime, two summers spent in Western mining camps had at-

Jan 1, 1920

By P. R. Martin, R. B. Kelly

Drilling in Central Texas during 1933 was confined, for the most part, to the search for new serpentine plugs. Bastrop County led in this particular activity, with 50 completions during the 12 months' period, 12 of which were productive. Only one new field was opened in Central Texas during the year, it being known as "Hilbig" (Bastrop County) and was discovered by the Humble Oil & Refining Co. The finding of commercial production in the serpentine at 2500 ft. led to further search in this and surrounding counties, but without success. Bexar County actually provided the greatest amount of drilling but the activity was limited to shallow development from 400 to 2000 ft. The Edwards limestone pay, which has been such a factor in past years, received but slight attention during 1933. Unsuccessful exploration was carried on in Lee and Burleson counties. With the exception of Freestone County, the Woodbine sand area was given even less consideration. This county, because of its close proximity to Anderson and Leon counties, saw a very active leasing campaign and several important tests drilled. In Central Texas, 252 wells were completed in 1933, and of this number 52, or 21 per cent, were productive. Hilbig Field The discovery well, Humble Oil & Refining Company's Annie Hassler No. 1, was completed Feb. 16, 1933, for an initial production of 65 bbl. the first hour, through tubing and 1/2-in. choke. The production was found in serpentine at 2468 ft. and tested 37.2" A.P.I. gravity. Twelve producing wells were drilled during the year and served to indicate that not more than 300 acres would comprise the entire field. Daily production at the end of the year was 775 bbl., although the field potential was 18,240 bbl. daily through 1-in. choke. The field adapts itself to pressure maintenance, and this scientific handling is being undertaken by the Humble Oil & Refining Co. through one injection well. It is the only area in the district where work of this nature is under way. Proration of Oil The more stringent application of proration in 1933 did not affect materially the producing fields in Central Texas. This is accounted for

Jan 1, 1934

By W. R. Ingalls

THE manufacture of zinc oxide directly from the ore is one of the most important contributions that America has made to the metallurgy of zinc. Heretofore, this has been clone chiefly for the production of zinc and zinc-lead pigments, and the method has been known as the Wetherill process. While that term may properly be applied to the process for pigment manufacture, it must be recognized that the principles of the process are of far wider application; and that there is going to be wider application in the immediate future is more than an expectation. I have in mind the use of the process as a method of igneous concentration. Igneous concentration is broader in its scope than the Wetherill process, for it may be done in the blast smelting furnace, or in the reverberatory, or by other means. Igneous concentration is a rather clumsy term, and I prefer to introduce the new generic expression of "zinc burning," which is convenient, readily understood and precise, for in all cases the zinc oxide is reduced to metallic form, is volatilized and is then burned to zinc oxide, the latter happening, however, after the zinc has been separated from the residue of the ore. As previously indicated, zinc burning may be done either in blast or reverberatory smelting, the gangue of the ore being scorified and drawn off as slag, while other metallic minerals are reduced to matte or metal. Such processes have heretofore been practised on fairly large scales. Thus, F. L. Bartlett smelted zinc ores at Canyon City, Colo., in specially designed blast furnaces, wherein the smelting column was only about 18 in. high. Such a limitation was necessary in order to prevent zinky accretions in the shaft of the furnace, which in course of time would have interfered with its operation. In running the Bartlett furnaces it was easy to bar them off, indeed, to poke right down into the smelting zone, and keep things going freely. Some iron blast furnaces in Virginia and the spiegeleisen furnaces of the New Jersey Zinc Co. afford other examples of zinc burning in blast-furnace smelting, although in their cases the happening is incidental rather than a primary purpose.

Jan 9, 1917

BECAUSE it is necessary that the powders made for casting have a magistery of salt water, I wish now to teach you to prepare the salt that must form this magistery, for without it these powders would not have the toughness to hold themselves together when they are dry. In short, you take the quantity [119v] of salt that you need to prepare and put it in a rough pot, either baked or, if it suits you better, raw but well dried. This is completely covered with a lid or is luted with well- made moulding clay. Then it is encircled with brick ends at a distance of three dita, like a drying furnace. This space is filled with good charcoal; fire is applied and it is left to stand until all the charcoal is consumed by itself* Then you take that quantity of this burned or rather melted salt which you wish to use for moistening the clay and which you think can be dissolved in the water so that it wd remain very salty. It is boiled in a pot with water and then left to stand. After it has settled, your powder is moistened with it and used for moulding. When you see by testing it that the powder stands up as you wish, it is good. If not, give it some more of this water again and continue until you see that it holds enough. For without this magistery it would return to the dryness that it had before as a powder, and you could not use it without fear that it would fall from the Games. In this way this earth, either natural or artificial, is prepared and made ready, and it is used as the need occurs.

Jan 1, 1942

ROBERT M. KEENEY,* Portsmouth, Ohio (written discussion?).- Mr. Coffin has written a most interesting paper that covers most of the uses to which water-cooled devices are subjected; but to meet with the operating department's approval, these devices must effect a saving in cost per ton of ingots produced in the furnace. The making of steel in the open-hearth furnace is dependent entirely on the personal element. It is not possible to charge the furnace with so much raw material, turn on a valve for heat, and by use of recording thermometers, clocks, etc. empty the furnace when a steel is made. Competent men trained to the work must be in charge all the time, and the quality and quantity of steel produced is quite as dependent on the care and working qualities of the furnaces as on the raw material and working of the charge itself. Steel making is hot, hard work and the inducement offered to technical men to take up this work is not sufficient to induce many to enter the field. The result is that most of the workmen in an open-hearth plant, the men who actually operate the furnace and make the steel, are not technical men and do not understand the "whys" and "wherefores " and care less. All this means that a furnace must be built as nearly fool-proof as possible. By this I mean that it is necessary to protect those parts of a furnace most subject to abuse by water-cooled devices whenever possible, and these water-cooled appliances must he as nearly fool-proof as they can be made. The control of the gas entering a furnace is of the utmost importance. This means a properly designed port must have the same design throughout the whole run of the furnace. This is not possible with the ordinary

Jan 6, 1919

By P. A. Beck

In the course of work on grain growth in high purity aluminum a simple optical method was developed for detecting the presence or absence of preferred orientation in annealed specimens. The specimens were prepared by grinding, polishing and "deep etching." The etching reagent used for high purity aluminum has been described.* The resulting etch pits produced selective

Jan 1, 1949

By C. E. Sims, F. W. Boulger, H. A. Saller

Most of the data on equilibrium constant and the deoxidations potentialities of those elements, considered to be stronger deoxidizers for steel than is silicon, have been calculated from thermodynamic data. The reason for this is, primarily, the obvious difficulty of obtaining direct experimental evidence of equivalent accuracy. This is an excellent use of the principles of thermodynamics and has given valuable data not otherwise available. Such results, of course, can be no more accurate than the physical constants used in the calculations, and one can never be sure that the basic data are either complete or accurate. In fact, as in the case with silicon,1 there are not only discrepancies among the calculated theoretical values of the equilibrium constant for deoxidation of steel but also between the theoretical and experimental values. It is highly desirable, therefore, to obtain experimental values for checks on calculated results whenever possible. If they disagree, both cannot be right, but if there is good agreement, their value is enhanced. The present work was done in an effort to obtain experimental evidence in regard to some of the common alloying additions but more particularly the so-called "strong" deoxidizers for steel. The method used was to determine the minimum concentration of the deoxidizer that would effect a certain definite degree of deoxidation in steel. The criterion of deoxidation was the change from the large globular Type I sulphide to the eutectic Type II as described by Sims and Dahle.2 This change is sharp and definite, and inasmuch as it can be produced with equal facility by aluminum, zirconium, and titanium, it is considered a manifestation of a certain degree of deoxidation and not an alloying effect. Ostensibly such a procedure could give only a comparison of deoxidizing powers and no absolute values. Nevertheless, repeated observations have shown that, when increasing increments of aluminum are added to a steel, the residual aluminum content begins to increase simultaneously with the appearance of Type II inclusions. Thus it seems warranted to postulate that the Type II inclusions appear coincident with the virtual elimination of FeO as an active constituent of the steel. Experimental Procedure The data obtained were primarily from the microexamination of polished and unetched specimens and from chemical analysis. Experimental heats weighing 200 to 250 lb were made in a basic-lined high-frequency induction furnace. The base composition was nominally that of a medium-carbon casting steel to which the appropriate additions were made. Specimens were poured into sand-cast ingots 3 in. in diam as shown in Fig 1. Sand-cast ingots were used to prevent chilling and to allow sufficient time in freezing for normal inclusions to form of a size large enough to be studied readily. In the first few heats, the tapered wall ingot was used, but in the majority, the extra large riser was used to prevent piping in heavily deoxidized steels. Specimens for microexamination were taken from the location shown in Fig 1, and drillings for chemical analysis were taken from a similar location. The procedure was to melt the base composition and deoxidize with the usual manganese and silicon additions and then to pour an ingot. The furnace was then tilted back, and the first increment of strong deoxidizer or special alloy was added and allowed to disseminate through the melt, with enough power on to hold the temperature constant, for 45 sec. Then a second ingot was poured. After this, another increment was added, and after the same holding time another ingot was poured. In this way from 9 to 12 ingots were poured from each heat, each successive ingot having progressively larger total additions of alloy. Eighteen heats were made altogether, and the range of alloys used and additions made are outlined in Table 1. The three principal types of sulphide inclusions found are illustrated in Fig 2. The globular Type I sulphides are characteristic of silicon-killed steels, the eutectic Type II are characteristic of steels deoxidized with a small amount of aluminum, while the larger, angular Type III are usually found in steels with a residual aluminum content above about 0.02 pct. In all specimens studied, the transition from Type I to II either did not occur at all or was very abrupt and clear cut. There never was any doubt as to just which increment produced the change, although the individual additions were small, in the order of 0.01 pct. The change from Type II to Type III was considerably less sharp, and, in some cases, both types were found together. Inasmuch as the formation of Type III sulphides is apparently not a deoxidation phenomenon, they will not be discussed here.

Jan 1, 1950

By Oswald J. Heinrich

At the Baltimore meeting of the Institute in February, 1879, Mr. Eckley B. Coxe, then president of the Institute, called attention in his address to the subject of Secondary Technical Education, and

Jan 1, 1881

By Friedrich Wellmer

INTRODUCTION The Ramsbeck Pb/Zn Mine is located in the northern Sauerland area of West Germany, 150 km N of Frankfurt and 120 km E of Cologne. This is a vein deposit which has been worked from the middle of the 19th century to 1974. About 15 million tons of ore were mined and milled. The ore district contains several vein deposits and is roughly 14 km in length and 4 to 5 km in width. The host rocks are strata of Lower Middle Devonian age. The strata strike 60° to 70° NE and where overturned have a dip steeper than the veins (Fig. 1). The galena-sphalerite mineralization is in quartz veins, which are mineralized where they cut the "Main Ramsbeck Quartzite" horizon, a very competent host rock. Vein structures strike at 65º to 75º, dip about 20° to 25º SE and cut the quartzite at approximately 60 m intervals. The main or "steep veins" within each vein structure dip at 10º to 80° SE with an average of 30° and are offset by thrust faults dipping 5º N to 40° S with an average of 5º S. "Flat veins" usually weakly mineralized occur in the thrust faults between the "steep veins", thus forming the overall step-like vein structure. The mineralization is very irregular and changes a- long strike and down dip. It consists of thin veins of pure sphalerite and galena with quartz and pyrite. The thicknesses of the pure sphalerite and galena veins

Jan 1, 1977

Edward Eeller, Baltimore, Md. (communication to the Secretary): Mr. Miller's improved method of the cyanide-assay for copper will, without doubt, be much appreciated by assayers and chemists who are engaged at copper mines and works. The writer, as one who, at one time, had much work of that kind to do, entertains no doubt of its practical value. In enumerating the factors which affect the accuracy of cyanide-titration, Mr. Miller omits to mention time. This I have always considered an essential one; i.e., in order to secure accuracy, I have believed it to be necessary to run the cyanidesolution at the same rate of speed in standardizing as in the titration of the samples. I have accomplished this, without the use of a time-keeper and without noticing the volume of the solution, in the following simple manner: In running the cyanide-solution from the burette, the stream was so regulated, by manipulation of the cock, that it retained its continuity for a distance of about one inch below the orifice, and, below that, broke into individual drops. This means that a constant pressure is maintained at the orifice of the burette, so that, during equal intervals of time, equal volumes of the solution pass through. The stream of cyanide-solution was left to flow in the manner indicated until the blue ammoniacal copper-solution began to show a distinct change in color, after which the cyanide was added by drops at regular intervals until the desired end-reaction. When several burettes are used they should have orifices of equal diameter; otherwise, the timefactor must be considered separately for each. In accordance with Mr. Miller's views, I have always considered the cyanide-method as of very satisfactory accuracy for all copper-assaying in which I did not employ the electrolytic method. It may interest some of my colleagues to know the modified method which I employed some fifteen years ago in making great numbers of copper-estimations on ores and

Jan 1, 1902

By D. F. Haley

THE molybdenite deposits at Climax, Cool., have recently attracted considerable notice, because of their great size, as compared with other known deposits of the same mineral. Climax station, on the. Colorado Southern narrow-gage railway, was at one time the Fremont Pass station on the Denver & Rio Grande. It is 1412 miles northeast of Leadville, and exactly on the divide between the headwaters of the Arkansas and Blue Rivers. Climax station is 11,300 ft. (3444 m.) above sea level. The working tunnel of the molybdenum mine is about 1 mile from the railroad, and 900 ft. above it, at an elevation of 12,200 feet. The climatic conditions are severe, and snow can be expected during any month of the year. Winter sets in not later than Nov. 1, the snowfall is very heavy, and the ground remains covered with snow until June 1, and sometimes even later. From June 1 to Oct. 1, there is much rain and a little snow falls in the late afternoon nearly every day. In October, 1917, there was one of the biggest snowstorms and blizzards of the year. Being just on the divide, constant strong winds blow the fine, dry snow with such force that, during most of the winter, outside work of any kind -is accomplished under most trying conditions. Within a few miles of Climax, some of the richest gold placers of Colorado occur. One of them, McNulty Gulch, was just across on the northeastern flank of Bartlett mountain. This mountain, therefore; was well prospected, and the presence of a bluish mineral and a yellowish one resembling sulphur was known to the old prospectors. They thought for many years that the blue mineral was graphite, and it is difficult to say when it first became definitely known that it was molybdenite. Claims had been staked as .early as 1896, but it is evident that the prospectors at that time were looking for gold. In 1902; several claims were acquired by H. Leal, who drove a tunnel about 900 ft. (274 in.) long, probably to intersect a fault, which shows on the surface, and was thought to be a possible gold carrier. Gold was not found in paying quantities, but throughout its length the tunnel passed through a fractured silicified granite, showing a fairly uniform distribution of a fine-grained bluish mineral, which was finally determined as molybdenite. For several

Jan 8, 1918

Herbert A. MegRaw, San Luis de la Paz, Guanajuato, Mexico (communication to the Secretary *):—I am in entire accord with the basis of Mr. Lamb's argument, that the stamp

Jan 1, 1911