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By Paul A. Farrar, Louis P. Stone, Harold Margolin

The Ti-Mo-0 system was investigated in the region 0 to 45 wt pet Mo and 0 to 10 wt pet 0, from 600° to 1400°C. Solidus data are also presented. Isothermal sections at 700°, 900°, 1100°, and 1300°C, and vertical sections at 1 and 28 wt pet Mo, and 1 and 10 wt pet 0 are included. STUDY of the Ti-Mo-0 system has been carried out as part of a general study of titanium phase diagrams. The binary Ti-Mo system has been investigated in whole or in part by several investigators.1-8 It was found that molybdenum and ß-tita-nium form a complete series of solid solutions and that the ß/a + ß transus is depressed to below 600°C at approximately 30 pet Mo.* The Ti-O system has been investigated partially or fully in the range 0 to 30 pet 0 by several investigators." Extensive solubility of oxygen occurs in the field. While a is

Jan 1, 1957

By W. A. Olds, H. F. Yancey, M. R. Greer

John Griffen (Consulting Engineer, Pittsburgh)— This paper presents much data offering tentative answers to many technical questions that have been raised by the employment of dense-medium processes and, particularly. by use of the drum-type vessel. It is to be hoped that the Bureau of Mines will publish complete detailed data for the 50 or more tests so that it may be studied and analyzed by everyone interested. Such study will take considerable time and effort. The writer is therefore obliged to confine his discussion to a few points he has noted as being open to question. The data in Table VI which shows the recovery efficiency for the 1 to ½-in. fraction as 100 pct raised a question concerning the accuracy of these calculated figures; washability data on the washed coal and refuse show that such a figure is impossible. When the ash content of the misplaced material in the washed coal is higher than that of the misplaced material in the refuse, recovery efficiency must be less than 100 pct. A etudy of the data In Tables 111, IV, V, and VI suggest that this error probably arose from slight errors in calculating the data in Table V and more probably from the small scale used in plotting the washability curves from the Table V data. Using the size consist data and the weight and ash percentages of individual gravity fractions of each size as given in Tables 111 and IV and the reported recovery of 80 pct of washed coal, a revised Table V was calculated, carrying weight and ash percentages to hundredths of a percent instead of rounding off at tenths. This washability data for each size of Belling-ham reconstituted feed was then plotted on large scale washability curves. From this data the new Table XIV was prepared, which agrees very closely with data shown in Table VI except for two important values, theoretical yields and recovery efficiencies. As will be noted the recovery efficiencies in Table XIV are significantly lower than those given in Table VI. A study was then made of the data showing distribution of the specific gravity fractions to washed coal and refuse. This study indicated that when this distribution was based on the fractions as tested at 0.1-sp gr intervals the number of points obtained were insufficient to establish the distribution curves with reasonable precision, which in turn would affect the accuracy of the values for the specific gravity of separation and the error areas. The data in Tables III and IV of the paper and curves prepared therefrom make it possible for the specific gravity fractions to be subdivided further. This was done using 0.05-sp gr fractions and the distribution data so obtained is given in Table XIV, with resulting values for the specific gravity of separation and the error areas. The writer believes that the derived values shown on Table XIV are more accurate than the correspond-

Jan 1, 1955

By A. J. Lynch, E. V. Manlapig, J. S. Hall, G. C. Thorne

Modelling of industrial sulphide flotation based on data collected in several flotation plants is discussed. A mechanistic approach is used in which it is recognised that flotation is a two stage pro- cess with concentration occurring both in the pulp and in the froth. The important features of the model, which is a kinetic model, are – 1. for each particle species there is a range of flotation rates which corresponds to the range of particle sizes, 2. the flotation rates of the liberated gangue particles which have no hydrophobic properties are dependent on the flotation rate of water and are controlled by variables such as the air and frother addition rates, and the pulp level, 3. as an approximation the valuable sulphide particles may be regarded as being present in two groups with high and low flotation rate constants, 4. increase in the addition rate of collector tends to increase the proportion of sulphide particles which are in the high flotation rate constant group. The actual flotation rate of each group of particles is a combination of an "inherent" flotation rate and a flotation rate which is dependent on the flotation rate of water, 5. at particular air and frother addition rates and pulp levels there is a physical limit to the rate at which particles can be transported into the concentrate and this is recognised in the model. The model has been used to study the steady state and dynamic properties of flotation circuits in operating plants. The assessment of the behaviour of composite particles is difficult because of the problem of quantitatively describing the surfaces of mineral particles. A method which is being developed to measure unpolished particles is described briefly.

Jan 1, 1976

Discussion of the paper of E: D. Gardner, presented at the Salt Lake meeting, August, 1914, and printed in Bulletin No. 91, July, 1914, pp. 1467 to 1471. H. V. WINCHELL, Minneapolis, Minn.-There are two questions I should like to ask: First, does the Department still adhere to the decision made in the East Tintic case? Second, does the Department require placer ground to he of such value that, in the opinion of the Forest Service employees, it will pay to work, before admitting the location to be valid? T. C. HOYT,* Ogden, Utah.-With reference to the first question: the Department does not hold to that decision, as it was reconsidered by the Secretary Of the Interior, and the Department is governed by the decision of the Secretary Of the Interior, on those points always. The Department of Agriculture makes no decision as to what constitutes a sufficient discovery. The mineral examiners simply report their findings and Opinions. These are transmitted to the chief of the field division of the General Land Office, who in turn transmits the reports to the Commissioner Of the General Land Office, who decides whether the report raises an issue requiring a hearing. If a hearing is ordered, expert testimony is given on the question of the discovery, as well as the evidence of practical people who operate in the vicinity of the claim in question. As to the extent of placer values considered sufficient to justify a location, my answer will need a little amplification. I couldn't answer it directly for the reason that sometimes people resort to placer claim location as a means of acquiring land for Other purposes than placer mining, which makes it absolutely necessary that the government give close attention to the question of whether good faith has been shown, as it is the evidences of good faith that largely determine whether a report adverse to a claim shall be made. That is a difficult point to cover sometimes. For instance, in the region I have recently visited there are some 17 miles of a valley, from ¼ to ¾ mile in width, all covered by placer locations. It is valuable stock-grazing land, and is stocked at the present time. It also contains a stand of timber, and is on the watershed of an important stream-important from the fact that it furnishes the water supply to government storage reservoirs, and to pending reclamation and Carey Act projects. In this case the placer claims will not be disturbed as mere locations. They will simply remain there, and there will be no action with reference to them until the claimant asks for patent or, before patent, begins to denude that watershed and remove that timber. Then the government would direct that the mineral experts go on to the ground, examine it, prospect it, and submit their report, with a view to seeing if

Jan 11, 1914

By Persifor Frazer

It has been the aim of the writer, by measuring his base line on the territory of theoretical chemistry, to attempt to fix by triangula tion certain points within the domain of mineralogy. As the barest first experiment in this direction, a few of the hydrated oxides of iron have been selected, their theoretical construe tion reduced to percentage of the constituents into which the ordinary analytical methods would resolve them, and the results compared with actual analyses compiled from the most reliable sources; the accidental errors being as much as possible eliminated. This method seems to be a simple one and one easily pursued, but, as will shortly appear, it is beset with grave difficulties, all of which the writer does not pretend to have satisfactorily surmounted. In the first place arises the important question, what are we to understand by the hydrated oxides of iron ? In all books of chemistry and lexicons of minerals, the proposition, long ago taught by the earlier chemists, that water might exist in two forms of combination, viz., as water of crystallization or as water of constitution, is tacitly assumed. There is nothing in the principles of the new chemistry which is opposed to this; for (to carry the mind's eye into the process of con struction of the least units into which a definite chemical compound is capable of being divided without losing its characteristic proper ties), however unlikely it may seem, it is, nevertheless, possible that a given molecule of iron may, under certain conditions of heat, pressure, etc., attract to itself as many molecules of the water in which it is natant as: from the relative size, shape, attractive force, etc. of either, it is capable of taking up, and this complex system of associated molecules might oscillate as a physical unit so long as the conditions on which its existence was dependent remained unchanged. Moreover, it is highly probable that the first effect upon such a mole cule produced by physical or chemical forces would be to separate it into two or more simple ones of different kinds, while a further ap plication of these forces might rend asunder the bonds of the simpler compounds themselves.

Jan 1, 1879

By H. S. Munroe

AN elaborate discussion under this heading formed a chapter in one of the reports made by Professor Raymond as Commissioner of Mining Statistics.* In a subsequent report- was printed a paper, by Mr. William Main, Jr., of Columbia, South Carolina, containing a theoretical investigation into the effect of the velocity of impact on the effective ditty of stamps. A visit to the Lake Superior copper region last summer suggested an inquiry into the relative efficiency and economy of the enormous steam stamps of the copper-mills, as compared with the results obtained with the cant and tappet stamps commonly used in the West. The atmospheric stamp used at the Phoenix Mill promised to add interest to the inquiry, as giving an example of unusually high speed, this stamp making 160 drops per minute. In introducing his subject Dr. Raymond makes the following remarks, which are quite apropos of the present investigation : "In considering the economical application of stamping machinery, we meet, at- the beginning, with serious difficulties in obtaining accurate data for comparison. The weight and fall of stamps vary as the shoes and dies wear out; and this may lead to a change of speed also. Moreover, defects in engines, boilers, or machinery for the transmission of power, may occasion serious losses, which cannot fairly be charged to the arrangements of the stamps proper. Again, the capacity of stamp-mills is directly dependent, in some degree, upon the nature and extent of discharge, fineness of screens, and other peculiarities of the battery. Finally the hardness and tenacity of the rock crushed varies so much that comparisons between different localities cannot be implicitly trusted. The safest experiments are those made in the same mill, by changing first one and then another condition of working; but this is seldom possible for such * Mineral Resources West of the Rocky Mountains, 1871, p. 380. †- Mineral Resources West of the Rocky Mountains,, 1873, p. 345.

Jan 1, 1881

By Frederic K. Bunton

The smelting plant of the British Columbia Copper Co. at Greenwood, B. C., now closed because of the decline in the price of copper due.to the European war, is of special interest to metallurgists for several reasons. It was successfully smelting in blast furnaces the lowest grade copper ore of all plants in America. In order to do so, it had to run at very hig~; efficiency, which necessarily required a large tonnage per square foot of hearth area, together with the minimum amount of labor and other costs. The furnaces smelted daily 2,250 tons of ore (6.62 tons per sq. ft. of hearth area), carrying 0.85 per cent. of copper, at a smelting cost of 81.18 per ton. The entire plant required 130 men to operate it and keep up repairs, showing a labor efficiency of about 17.5 Dons per man per day. In the present paper, the method of obtaining these results is shown. Most of the information contained in this description I obtained as Assistant Superintendent, during the two years preceding the present shutdown. Other sources of information to which I am indebted are: The British Columbia Copper Co., Ltd., by ALfred W. G. Wilson, in The Copper Smelting Industry of Canada; Greenwood Smelting Worlrs, by J. E. McAllister, Engineering and Mining Journal, vol. xci, pp. 1011 to 1015 (May 20, 1911); and Description of the Copper Smelter of The British Columbia Copper Co., by W. L. Bell, in Transactions of the Canadian Mining Institute, vol. xvi, pp. 151 to 154 (1913). II. Location and Connections The smelter of this company is about half a mile south of GreenGood, in the Boundary district of British Columbia, on the Columbia & Westerg branch of the Canadian Pacific Railway. It was originally built in 1900 by Paul Johnson, to handle 600 tons of ore a day in two small furnaces of 300 tons capacity; but in 1907 the old furnaces were torn out, the plant was remodeled, and three blast furnaces, 48 by 240 in. at) the tuyéres, were installed. In 1910, two of these were enlarged to 51 by

Jan 1, 1916

TO THE BOARD OF DIRECTORS AND THE MEMBERS OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS Gentlemen -It is pleasant to be able to report that the year just closed has been a prosperous and successful one for the Institute As is shown by the reports of the Treasurer and the Finance Committee, the business affairs of this organization are in excellent condition With property valued at more than three-quarters of a million dollars, and with con¬siderable sums in various funds and endowments, it is possible to spend on each member of whatever class $22 65 each year, more than the maxi¬mum amount of dues received from any one, and substantially twice the average amount, $10.94, received from all To do this has required close management and a strict regard for our limitations In 1926, when the Budget was made up, the estimated expenditures for the work which it was felt the Institute must do exceeded the estimated receipts by some $14,000. At the close of the year, despite a` number of unexpected decreases in receipts, it had proved possible to accomplish substantially all the work laid out and close the books with the usual transfer of initia¬tion fees to the General Reserve, and still only reduce the cash balance $2,074 54. This was made possible by the hearty and loyal cooperation of the whole staff of employees and the extremely large amount of gratui¬tous service rendered by the officers, the members of the Divisions and technical Committees, and the membership generally Even so it was impossible, because of limitations of funds, to undertake many things it is highly desirable for the Institute to do, and it was necessary to refuse the publication of important papers and committee studies, because of the lack of funds.

Jan 1, 1923

By J. E. Tiffany

FOR blasting in coal mines the U. S. Bureau of Mines recommends that permissible explosives be used exclusively, that these shall be fired electrically, and that where feasible the working place shall be cut or sheared. These recommendations are made to promote safety and prevent mine explosions. Although permissible explosives are not flameless, their lower flame temperature and shorter duration of flame make their use safer than that of non-permissible explosives. Mixtures of air with both methane and bituminous coal dust, which are liable to occur in coal mines, may be ignited by coming in contact with any type of flame or spark of sufficient temperature and duration or by the firing of a blast. In a working place where a blast is to be fired, in addition to the use of permissible explosives, adequate ventilation for the dilution and removal of accumulations or outbursts of flammable gas should be provided. Bituminous coal mines should be rock-dusted as a means of rendering the coal dust harmless. The efficient use of permissible explosives depends upon the proper preparation of the working place, standardized drilling, the strength characteristics of the explosive, and the use of a proper weight of charge. Experienced shotfirers should load, tamp and fire all holes. The major part of the information and data here presented is based on the results of efficiency tests made in large producing mines of Pennsylvania and Illinois. Bureau of Mines Report of Investigations, Serial No. 2697, describes how a standard method of blasting was worked out and put into operation in a mine in southern Illinois.1 This paper contains a description of the methods worked out subsequently in another mine in that district.

Jan 1, 1928

By John C. F. Randolph

This establishment being now in full working order, it has seemed of considerable professional interest to collect together, in a concise form, the various points as to its plan, method of dressing, and equipment. The data contained in this paper have been largely drawn from the able paper of E. Kutscher, constrnoting engineer of the works, contained in the Zeitschrift fur Berg-HÜtten-und Salinenwesen im Preussischen Staate, 1873, supplemented by some personal memoranda made while the works were under construction and by memoranda on the works appearing in various German technical papers from their completion up to date. This is probably the largest dressing works in the world devoted to the beneficiation of argentiferous lead ores, and it is doubtful if any establishment for the concentration of mineral of any description can compare with it in size. As showing the final practice adopted in an old and very conservative mining region, in which the concentration of ores has been a matter of constant practice and experiment for a very long period, these works are of peculiar interest. The fact that the Clausthal ores strongly resemble a very large and abundant class of ores found in the United States has always attracted the attention of American mining engineers and mine owners to the methods employed in dressing and smelting them. The study of their methods of concentration of ores has, however, always been full of difficulty,

Jan 1, 1879

By G. Derge, L. D. Kirkbride

In recent years the problem of sulfur elimination in iron and steel-making has been of increasing importance. This interest has been due to the increasing amounts of sulfur coming into the system via raw materials. As a result, many investigations have been directed at obtaining information pertaining to the rate and mechanism of sulfur removal in the blast furnace as well as measuring appropriate thermodynamic quantities. Chang and Goldmanl as well as others2'3 showed that the process of sulfur transfer from molten carbon-saturated iron to blast furnace-type slags could be considered as two opposing first-order chemical reactions. Recently, Ramachandran et al.4 have shown that during desulfurization electrical neutrality is preserved in both phases and iron and silicon are transferred into the slag concurrently with the evolution of carbon monoxide gas. They concluded that the reaction s + c-+ (0)=(S) + CO(g) does not express the stoichiometry of the sulfur transfer process. As in all previous investigations, these authors studied the process of a net transfer of sulfur from metal to slag across a slag-metal interface. However, no experimental data have previously been obtained for the process of sulfurization. It was the purpose of this study to investigate the sulfurization process, i.e., net transfer of sulfur from slag to metal. EXPERIMENTAL PROCEDURE Apparatus—The equipment used in this investiga-tion was typical of that used by others.1-3The furnace was a high-frequency induction unit powered by a 35 kw Hg spark gap converter. Fig. 1 shows a schematic diagram of the apparatus. A two-compartment crucible assembly was employed to melt the slag and metal charges; being similar to that used by Ramachandran,4 in size and design. The atmosphere was that produced by reaction of hot graphite with air. Temperature measurements were made by W-Mo thermocouples which were calibrated against a Bureau of Standards Pt - Pt 10 pct Rh couple. Temperature control was always good to * 5°C and in general was much better than this figure. Raw materials used in the experiments were C. P. reagent grade where possible. The silica used in the preparation of the slags was in the form of highly purified silica flour. Silicon and titanium additions

Jan 1, 1961

By Philip Morse

THE Australian lead-smelting plants began to use charges carrying high zinc percentages somewhat earlier than was common with American plants. When lead smelting first started in Australia the immense deposits of oxidized lead at Broken Hill were available but later these oxidized ores became exhausted and were replaced by sulfides. This was before the days of flotation and these sulfides when concentrated carried about 1 per cent. of zinc to 6 per cent. of lead. The works of the Sulphide Corpn. at Cockle Creek was perhaps the pioneer in high-zinc slags but the Port Pirie plant of the Proprietary Co. was a close and very able second and has continued the work to the present time. The Cockle Creek lead furnaces remained in operation until shortly after the war when most of the Broken Hill companies combined and took over the Port Pirie plant to treat their concentrates. As it was the practice both at Cockle Creek and Port Pirie to carry 20 per cent. or more of lead on the charge, it was found that under these conditions of large amounts of zinc in the charge, good roasting was absolutely necessary and matte production was unwise. The Huntington-Heberlein system of roasting was introduced and later the Dwight & Lloyd process. In this way, by roasting the sulfide portions of the charge as thoroughly as possible and making no matte, a method of smelting was developed where the slag over long periods carried as high as 20 per cent. ZnO without serious furnace troubles, and slags carrying even up to 33 per cent. ZnO have been reported. The zinc slags were not very different in appearance from the ordinary slags produced in American practice except that they gave off more smoke and fume on tapping. The slag usually ran hot and freely, coming from the tap in a full stream. Normally there was little crust on the sides' of the furnace and the tuyeres gave no trouble though they were always rather dark.

Jan 1, 1929

By Robert L. Akright

LOCATION AND HISTORY The Candelaria silver mine is located in an arid, isolated desert setting in Sections 3 and 4, T.3N., R.35E., and Section 33, T.4N., R.35E., Mineral County, Nevada (Fig. 1). Silver was discovered in 1863 by Mexican explorers, and high grade silver veins were mined from the early 1870s through the 1880s. Essentially all mining had ended by 1890. The veins were mined by underground methods typical of the period. As is the case in many mining districts, Candelaria was studied and explored by a number of companies. All these efforts were terminated short of mine development because of low silver prices and difficult metallurgy. On March 1, 1976, Occidental Minerals (Oxymin) entered into a Limited Partnership agreement, known as Candelaria Partners, as General Partner with Congdon and Carey Ltd. No. 4. Prior to the agreement, Congdon and Carey had acquired the candelaria properties as part of a bullish silver program and did considerable exploration which indicated the possibility of a large reserve of shallow silver mineralization. GEOLOGY AND ORE DEPOSITS Silver and gold mineralization in the Candelaria district occurs in high-grade fissure veins with silver values ranging from 0.6 to 7.8 kg/t (20 to 250 oz per st). These veins, combined with the low grade disseminated mineralization in the intervening material between the veins, form Manto- like deposits 15 to 46 m (50 to 150 ft) thick. Three such deposits are found in the Candelaria district: the Lucky Hill, Mount Diablo, and Northern Belle deposits (Figs. 2 and 3). The average ore grade of the Lucky Hill and Mount Diablo [ ]

Jan 1, 1985

By Persifor Frazer

(Read at the Amenia Meeting, October, 1877.) IT has been the aim of the writer, by measuring his base line on the territory of theoretical chemistry, to attempt to fix by triangulation certain points within the domain of mineralogy. As the barest first experiment in this direction, a few of the hydrated oxides of iron have been selected, their theoretical construction reduced to percentage of the constituents into which the ordinary analytical methods would resolve them, and the results compared with actual analyses compiled from the most reliable sources; the accidental errors being as much as possible eliminated. This method seems to be a simple one and one easily pursued, but, as will shortly appear, it is beset with grave difficulties, all of which the writer does not pretend to have satisfactorily surmounted. In the first place arises the important question, what are we to understand by the hydrated oxides of iron ? In all books of chemistry and lexicons of minerals, the proposition, long ago taught by the earlier chemists, that water might exist in two forms of combination, viz., as water of crystallization or as water of constitution, is tacitly assumed. There is nothing in the principles of the new chemistry which is opposed to this ; for (to carry the mind's eye into .the process of construction of the least units into which a definite chemical compound is capable of being divided without losing its characteristic properties), however unlikely it may seem, it is, nevertheless, possible that a given molecule of iron may, under certain conditions of heat, pressure, etc., attract to itself as many molecules of the water in which it is natant as from the relative size, shape, attractive force, etc. of either, it is capable of taking up, and this complex system of associated molecules might oscillate as a physical unit so long as the conditions on which its existence was dependent remained unchanged. Moreover, it is highly probable that the first effect upon such a molecule produced by physical or chemical forces would be to separate it into two or more simple ones of different kinds, while a further application of these forces might rend asunder the bonds of the simpler compounds themselves.

Jan 1, 1878

By F. F. Aplan

The past year has been another year of vigorous fundamental research in mineral processing as evidenced by the active publication of results, particularly in Germany, Japan, United Kingdom, United States and USSR. It was also noteworthy for several significant meetings and conferences. The Basic Science sessions at the AIME Annual Meeting continued to attract an increasing audience and the sessions were especially notable for the active discussion of papers. The third Engineering Foundation Conference on Particulate Matter Systems,1 chaired by F. F. Aplan, was held in Milwaukee in August and attracted over 100 experts from five continents. Sessions at this week-long conference covered comminution, particle characterization, separation of fine particles, fluid-solid separations as applied to pollution control, flotation kinetics, particle-particle interactions and particle agglomeration. This popular conference will be continued under John Karpinski of Bethlehem Steel Corp. as 1968 chairman.

Jan 2, 1968

By J. G. Thompson

OXYGEN, nitrogen and hydrogen are present in practically all metals in one or more of the following forms: (1) molecular gas in blowholes or blisters, (2) combined in nonmetallic inclusions such as nitrides, oxides or silicates, and (3) in solid solution in the metal. Gaseous elements, in some of these forms, are encountered in practically all metals and alloys but possibly have received most publicity in connection with iron and steel. In fact, the entire steel industry depends upon the control of the oxygen content during the refining process, as well as in the finished material, and it was only after the adoption of the use of efficient deoxidizers such as manganese that the production of good steel with a low carbon content became possible. In normally clean, sound steel the amount of hydrogen is negligible and the amounts of oxygen and nitrogen vary from a few thousandths to a few hundredths per cent. However, many of the effects attributed(27,31,40.41,53,54,55,56,62) ? to the presence of these elements are important and at first glance appear to be out of proportion to the amounts of impurities involved. The presence of oxygen is believed to affect the solubility of carbon in austenite and ferrite and thereby to affect the structure of the iron or steel. Such properties as strength, hardness, ductility, elastic limit, impact resistance, magnetic permeability, tendency toward caustic embrittlement, irregularity in carburization, the cutting life of tools, certain corrosion phenomena, the presence of flakes, seams, bands, ghost lines and hair cracks, and the tendency to age-harden, all have been attributed to the presence of oxygen.

Jan 1, 1932

By Stephen E. Merritt, John W. Straton, T. Carl Shelton

Surveying and mapping are used to locate and visually portray objects, lines, or areas in relation to a reference point or line. The actual making of the measurements to locate the objects and points falls under surveying while mapping is concerned with putting the survey information into a graphical form. Generally, the type or class of proposed survey depends on the precision required. Some surveys may need only approximate measurements which can be obtained by simply pacing or by using an ordinary measuring tape; others may require much accuracy, thus calling for the use of an engineer's transit or theodolite along with a graduated steel tape for horizontal measurements, or a level and a graduated rod for measuring vertical distances. Mapping is likewise dependent on accuracy requirements. For example, a general layout showing the relative position of surface facilities may not call for a large scale of dimension or great precision whereas for detailed work, a large scale plus care in plotting points and drawing lines and curves are important factors. SURVEYING METHODS There are many kinds or types of surveying methods. Some examples include : land surveying for determining boundaries of land areas; route surveying for locating roads, highways, right-of-way, and haulways; city surveying for laying out lots, streets, and alleys; and mining surveying for projecting mine openings and locating mining operations. See Fig. 1. There are other types of surveying than those named, but in general, the type of method to be used will depend on the purpose for which the survey is to be made.

Jan 1, 1981

By J. J. Tietjen, D. Richman

Single-crystal Gap lms been epitaxially grow from the vapor phase at a rate oJ 3 p per nzin without encountering a7Zy low-ang-le grain boundaries or debwading- the electrical properties of the material. This growth rate exceeds any value previol~sly reported for the vapor phase growth of Gap. In pure material, mObilities ns high as 175 sq cm per U-sec at room tenzperature and 1450 sq cm per v-sec at 77°K have been obtained. These values are anLong the highest that have been attai)led for this material. For the first time, Gap possesses a number of important properties which make it well-suited for use in electro-optic modulators. First, the transverse electro-optic effect is operable in this material, which makes it possible to increase the path length of the modulated iron doping of Gap has been achieved; this results i?z resistivities of approximately 10" ohm-cm. The problelrls of residual strain and isolated shorting paths in these crystals have been partially solved. Electro-optic modulation of visible radiation has been demonstrated with this material. It is anticipated that further improvement with regard to the probleins of strain and shorting paths will result in a practical Gap electro-optic modulator. radiation without increasing the applied voltage. In addition, this permits the use of thin crystals so that relatively small voltages are needed to provide the requisite high electric fields. Second, GaP is a cubic crystal and therefore does not introduce critical optical-alignment problems associated with birefrin-gent crystals, such as ammonium dihydrogen phosphate (ADP), and potassium dihydrogen phosphate

Jan 1, 1968

By Roy Moore

THE Tom Reed Extension and Big Jim mines of United Eastern Mining Co. are situated in the Oatman district, Mohave County, Ariz., about 28 miles southwest of Kingman, the nearest railway point. Articles descriptive of the mine surface plant, mill construction, and plant operations have been written by Otto Wartenweiler1, the designing engineer; Wheeler 0. North,2 when he was assistant general manager for the company, and Earle M. Bagley, mill superintendent.3 The last article covers average costs for the full time the mill was operated. The geology of the mines is described by F. L. Ransome4 of the United States Geological Survey. Production was started in January,. 1917, and the known orebodies were exhausted in May, 1925, showing a life of seven years and five months. On account of the comparatively short life and the fact that stoping operations were confined to two orebodies, little experimenting was done with mining methods. The two orebodies were in what is generally called the Tom Reed-United Eastern vein, which occupies a fault fissure having a normal displacement of several hundred feet. Seven or eight very productive ore shoots were mined along this vein in a distance of 1 ½ miles, the two worked by the United Eastern being 1 mile apart. The maximum dimensions of the Tom Reed Extension ore shoot were height, 750. ft.; length, 950 ft.; thickness, 48 ft. The vein structure varied from a solid quartz-calcite filling to a series of parallel stringers separated by andesite. From this body, 511,976 tons of ore were mined. (Fig. 1.)

Jan 1, 1928

Discussion of the paper of H! M. CHANCE, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 91, July, 1914, pp. 1461 to 1466. R. V. Norris, Wilkes-Barre, Pa.-In his resume of coal-taxation methods Mr. Chance has apparently confined his investigation to bituminous coal, so a summary of the anthracite situation as to coal assessment should be of interest. The anthracite region of Pennsylvania in its 484 square miles of measures lies in the counties of Wayne, Lackawanna, Luzerne, Carbon, Schuylkill, Northumberland, and Dauphin, and in each of these different methods of assessment have been adopted. The assessments for taxation in Pennsylvania are made under Acts of the Legislatures of 1841 and 1842, under which the assessors are re¬quired to "assess rate and value every subject of taxation according to the actual value thereof, and at such rates and prices as the same would bring at a bona fide sale after due notice." Under this general law coal land has been assessed as such, but up to about 25 years ago the coal was assessed at rates so low as to be unimportant, though the rates in each township and municipality, even in the same county, showed no agreement or ascertainable basis. In the late '80s, the need for greater revenue drew attention to the possibilities of collecting much larger taxes from the coal lands and, spurred by public demand, the assessing authorities in some counties undertook a reassessment of coal. The method pursued was to demand from each owner a statement of the area and average remaining thickness of coal on his lands. On this return, made in some cases under oath, an assessment based on foot-acreage was levied, with a resulting great increase in valuation, but the valuation per foot-acre was low and no serious objection was made. This assessment with occasional increases of rate remained in force until 1907, when, in the triennial assessment of that year, a complete revision of the valuation was again attempted, engineers were employed by the counties to check the accuracy of the returns from the owners, and, based on the foot-acreage thus obtained, an enormous increase, to $65 per foot-acre, was made in the valuation. This assessment was resisted in the courts by appeals resulting in very extensive litigation, and a final determination of the validity of the 1907 and all subsequent assessments has not yet been obtained. In the first appeals tried the rate calculated on a foot-acre valuation was reduced by the Luzerne County court to about $45, while the. Lackawanna County courts reduced a larger rate to $67. The county authorities were, how-

Jan 4, 1915