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By K. L. Clark, Nicholas Kowall

MAXIMUM furnace efficiency and close control of final steel composition demand that the steel melter be able to follow closely the variations in the carbon content of the bath. For many years, the fracture test has been used by melters for estimating carbon, because it requires only a very short time to pour a sample into a chill mold, cool it in water, break it with a sledge hammer, and observe the fracture. After long experience gained from the observation of such fractures, most melters are able to estimate the carbon content of steel with amazing accuracy, particularly in the lower carbon ranges. Notwithstanding the utility of the fracture test, there has been widespread interest in other methods for rapid carbon determination to supplement it and to ensure against possible errors in human judgment. Several methods, based upon measurement of magnetic properties as functions of carbon content, have been described in the literature1-6 and have been found to give reasonably reliable results in plant practice when scrap composition is known and controlled. A difficulty encountered in the use of analyzers of the magnetic type is that alloying elements do change the relationship between carbon content and magnetic properties and it becomes necessary to establish calibration curves for all the expected combinations of alloy residuals that are not oxidized in the bath. The work reported here is of an investigation of a method that is independent of alloying elements normally present in constructional steels, being based upon the relatively well-known fact that in plain carbon and low-alloy steels martensitic hardness is a function of carbon content alone. WORK OF OTHER INVESTIGATORS In 1938, Burns, Moore and Archer published a curve7 that showed that the hardness of martensite is a function of carbon from 0.10 to 0.50 per cent and is independent of grain size or alloy content, at least within the range found in constructional S.A.E. compositions. Some of the deeper hardening types investigated, however, contained carbon to a maximum of only 0.20 per cent. Using this principle, Kern8 developed a method of rapid carbon determination for S.A.E. 43xx steels. His procedure consisted of chill-casting a test bar that was large enough to give a surface that could be prepared for Brinell indentations. The test piece was quenched immediately after solidification was complete and hardness readings were taken, so that the carbon content could be read from an experimentally determined curve giving the relationship between as-quenched hardness and carbon. EXPERIMENTAL WORK Although Kern's work had been done with a relatively deep-hardening steel, it

Jan 1, 1944

By Arnold H. Kackman

At the Kaiser Cement and Gypsum plant near San Jose, Calif., one rod-ball mill has taken over the entire raw grinding function for the largest single cement operation in the West. Installed as part of a major overhaul performed on the plant by Kaiser Engineers, the new mill does the work of seven previous mills in feeding the plant's six kilns and keeping pace with its annual capacity of 8.5 million bbl of cement. Installation of the mill, which is the largest in the world, was started in December of 1966 and completed in April of 1967. The over-all modernization program surrounding the new mill has included the modification of existing crushing facilities; the building of new raw materials handling and blending facilities, new raw milling facilities, and new slurry handling facilities; and the installation of a digital-analog control system.

Jan 7, 1967

A professional and special section of the United States Employment Service, Department of Labor, has been created for the purpose of aiding officers and men who have been discharged from military service, but who, for various reasons, cannot resume their former positions, to place themselves in industry without loss of time. Its work is carried out in conjunction with the Engineering Societies Employment Bureau. The machinery of this new professional section is being set up as rapidly as possible, and an office is already in operation at 16 East 42c1 St., New York. The work in the New York State district is under the direction of Mr. Henry Bruere, formerly City Chamberlain of New York City. Dr. Thomas T. Read, Chairman of the A. I. M. E. Committee on Industrial Organization, has charge of the clearance between the State offices of the Eastern States. This service is designed for the purpose of placing not only men in the engineering professions, but for all other kinds of professional and highly trained, skilled men. Full details regarding the qualifications desired in a man should be given, so that employers may be put in touch only with such available men as will fully qualify for the positions.

Jan 2, 1919

By Leon Y. Sadler

Three new transfer functions relating the time response of the amount of floatable mineral in the under flow to time-dependent changes in the amount of floatable mineral in the feed to the cell are presented. Using experimental stimulus-response data obtained from the flotation of -200+325-mesh glass spheres in a rotor-stator-type cell, the new transfer functions are compared to the only transfer function to be presently found in the literature by nonlinear least-squares fitting in the frequency domain. The new mathematical model based on the amount of available bubble surface area and its rate of introduction is quite promising. The transfer function which allows for a distributed first-order flotation rate constant also gives good results. Simultaneous sodium chloride tracer and glass bead stimulus-response tests show that the mixing conditions in the cell were nearly ideal. It is felt that the new transfer functions presented offer excellent alternatives for use in the design of automatic process control equipment for the continuous mechanical froth flotation cell.

Jan 1, 1974

By Orville R. Lyons

THE Russellton preparation plant of Republic Steel Corp., located north of Pittsburgh, Pa., prepares 3 1/2x0-in. Thick-Freeport coal by means of a 13-ft 6-in. diam Chance cone and 16 No. 7 Deister tables. The plant feed ranges between 370 and 410 tons per hr, of which approximately 31 pct is ¼x0-in. size, and the plant reject ranges between 14 and 16 pct of the feed. The 3½xY4-in. washed coal, the cone product, is dewatered and desanded by a double-deck Parrish-type shaking screen 46 ft long and 7 ft wide. The 1¼x¼-in. portion is further dewatered by two 4x12-ft single-deck vibrating screens. The ¼x0-in. washed coal from the tables is distributed to three 54x70 in. Bird centrifuges. The dewatered centrifuge product is combined with the product of the de-watering screens prior to loading into railroad cars. During the early part of 1951 complaints were received from officials at Republic's coke ovens concerning the moisture content of Russellton washed coal. The records revealed that during the first half of 1951 the shipped washed coal moisture averaged

Jan 1, 1954

By O. J. Kensok

THE literature contains three previous studies of the chemical activities of Cd-Mg alloys: Trumbore, Wallace, and craigl obtained chemical activities of magnesium at 543" by performing electromotive-force measurements; Borg and irchenall calculated activities at 590°K based on vapor-pressure measurements of cadmium over Mg-Cd alloys by the Knud-sen effusion method; and Terpilouski and arcka measured the chemical activities of magnesium in the liquid state by means of electromotive-force measurements. In this study the vapor pressure of cadmium was determined over nine solid Cd-Mg alloys in the temperature range 571" to 697°K by the Knudsen effusion method. This study was prompted by the lack of precision in the data reported by Borg and Birchenall. Knudsen cells used during this study were fabricated from 0.020-in.-thick tantalum tubing. The tops and bottoms of the cells were cut from 0.010-in.-thick tantalum sheet, press-fitted, and welded in place. The orifice was drilled in the cell top and subsequently reamed to a knife-edge thickness. The diameter of the orifice was measured with a traveling microscope capable of reading 0.0001 cm. The sample was heated by means of a resistance

Jan 1, 1967

By P. Somasundaran, I. J. Lin

There are several methods described in the literature for the determination of the order and the rate constant for the flotation of minerals. These often involve some type of computational or graphical procedures. A relatively simpler method developed on the basis of a technique used by Chang" in chemical kinetics is described in this paper. Chang's technique, like most others in chemical kinetics," is based on the law of mass action which states that the rate of a chemical reaction is proportional to the active masses of the reacting substances at any given time. Application of this law to the flotation of minerals would involve the adaptation of the terms "flotation" for "chemical reaction" and "floatable amount of the minerals" for "the active masses of the chemical reactants." There are indeed a large number of physical processes controlling the actual flotation rate. The most inefficient one of these could be considered equivalent to the slowest reaction in a series of chemical reactions. If variables such as aeration rate and agitation are kept at constant levels, the rate of flotation under free flotation conditions (i.e., conditions under which the suspension is dilute) will be given by the following equation: where C is the concentration of the floatable minerals in the pulp at any given time t, K is the rate constant, and n is the order of the reaction. If we represent the floated fraction of the floatable mineral at time t as m (0 m - 1) and C at t = 0 as Ca, integration of Eq. 1 yields

Jan 1, 1974

By F. R. Hensel

ACCORDING to statements by Guertler,1 Smith and Hamilton were the first to study the copper-titanium alloys, but owing to the presence of large amounts of impurities their data are inconclusive. M. A. Hunter and I. W. Bacon later investigated the electrical conductivity and the temperature coefficients at room temperature. The present writers reported their results2 in November, 1930. Recently Droll published data on copper-titanium alloys3 which agree closely with those obtained by the authors. MATERIAL TESTED The titanium used was in the form of square sintered rods, the analysis of which runs as follows: titanium, 95.4 per cent; silicon, 0.7; iron,1.8; aluminum, 1.4; copper, 0.1; manganese, 0.05. . The ingots were prepared in a high-frequency induction furnace in air atmosphere. Their analyses are given in Table 1. Up to 5 percent titanium the alloys could be forged. Above that amount they were red short and broke up easily. Owing to their rapid absorption of nitrogen and oxygen from the air, the alloys with the higher amounts of titanium tend to form surface films which greatly increase the casting difficulties, especially when small masses of metal are handled. It was, however, possible to prepare sound ingots up to 25 per cent titanium.

Jan 1, 1931

By George Mah, Charles Wert

Internal-friction peaks caused by diffusion of oxygen and nitrogen have been observed in ytterbium. They are thought to be caused by the redistribution, under stress, of strain dipoles around an interstitial oxygen or nitrogen and a neighboring substitutional impurity. With the use of a simple geometrical model, diffusion coefficients for oxygen and nitrogen between special interstitial sites have been calculated. a) APPLICATION OF INTERNAL FRICTION TO MEASUREMENT OF DIFFUSION RATES IN DISSOLVED INTERSTITIAL ATOMS In bcc metals, the interstitial atoms occupy the centers of cube faces (0, 1/2, 1/2), or their equivalents, the center of the cube edges (0, 0, 1/2). An interstitial atom in this position causes an aniso-tropic distortion in the lattice. When stress is applied, mechanical relaxation can take place by the movements of the interstitial atoms. This relaxation has been used to obtain information concerning the movements of the interstitial atoms in the bcc metals. Data for these alloys have been compiled by Stanley and Wert. Other researchers have extended the investigation of interstitial diffusion to the close-packed metals. Gupta and weinig2 found an oxygen peak in a titanium, the height of which is linearly dependent on the oxygen concentration. They assumed, therefore, that they were dealing with movement of atomic ally dispersed oxygen in titanium. KG and wang3 determined that the diffusion coefficients of carbon in fcc steels and in nickel obtained by internal-friction methods were consistent with those obtained by macrodiffusion methods at much higher temperatures. Bisogni found oxygen and nitrogen peaks in hafnium by use of which he deduced the diffusion coefficient of these gases in hafnium. He observed further that the half-widths of these peaks corresponded almost exactly with those of a single-relaxation process; he assumed it to be caused by movement of atomically dispersed oxygen and nitrogen. From these studies, the deduction can be drawn that, in general, diffusion data can also be obtained for the interstitial diffusion in close-packed metals (or more precisely, in slightly impure close-packed metals). One group of such metals for which little data exist for the diffusion of dissolved oxygen and nitrogen is the rare earths. They have great affinity for gases, which enter solution interstitially. In this investigation results were obtained for the Yb-O and Yb-N interstitial solid solutions with traces of substitutional impurities; these solid solutions are of fcc structure. b) MECHANISM OF THE RELAXATION IN FCC CRYSTALS In the fcc structure, an interstitial gas atom is usually situated in the octahedral position (1/2, 1/2,

Jan 1, 1964

By R. J. Borg, C. E. Birchenall

The self-diffusion coefficients for a iron have been deternzined between 980° and 1167° K using Fe55 as the tracer. With decreasing temperature the diffusivity was found to decrease more rapidly than predicted by the Arrhenius equation in the region of the Curie temperature. The diffusion coefficients obtained well above the temperature of the magnetic transformation are more precise ard differ substantially from all the previously reported values. In the temperature region beginning at least 50" above T,, the diffusion coefficient is given by D = 118 (±2) exp 1 HE self-diffusion coefficients for a iron have been reported previously as the result of four independent investigations The general lack of agreement and the poor precision of most of the previous work prompted the redetermination by the present authors. The possible effect of the onset of ferromagnetism upon the diffusivity5 provided an additional impetus for this investigation. The earlier measurements of Birchenall and Mehl1 gave low values for the diffusion coefficient at temperatures below the Curie temperature, Tc. However, the precision of these measurements is not sufficient to establish an indisputable correlation between the low values and the magnetic transformation. The results of this investigation along with all the previous ones are shown in Fig. 1. EXPERIMENTAL Small rectangular samples, approximately 1 by 0.5 by 0.3 cm, of high-purity iron (Vacuum Metals Corp., "Ferrovac") are first heated in hydrogen at 900°C for24hr in order to remove possible trace amounts of dissolved carbon and oxygen. The small

Jan 1, 1961

By Clair Upthegrove, Elbert S. Rowland

THE widespread interest in the alloys of beryllium with copper is due principally to the fact that certain compositions show very favorable precipitation-hardening characteristics and are, in fact, the strongest nonferrous alloys known at the present time. Investigations have been conducted by Masing and Dahl and others on the physical characteristics of ternary beryllium alloys, in an attempt to produce precipitation-hardening effects with a smaller amount of beryllium than that required in the binary copper-beryllium alloys (2.0 to 2.5 per cent Be). The results of these investigations show that ternary alloys of beryllium with Cu-Sn, Cu-Al and Cu-Zn, among others, exhibit promising improvements in physical properties after precipitation-hardening treatment and, while the increases in properties obtained are not as high as those realized from the binary copper-beryllium alloys, excellent properties are: obtained with beryllium contents averaging about one-half the amount required in the binary alloys. This paper presents the results of an investigation of the equilibrium relations of certain alloys containing copper, tin and beryllium. The alpha-phase boundary of the ternary system is given for alloys containing from. 0 to 1 per cent beryllium. The equilibrium conditions beyond the alpha-phase boundary are presented for alloys containing up to 32 per cent tin and 1 per cent beryllium. The data were collected by means of

Jan 1, 1935

By Henry J. Miller, Marcella Lindeman

DURING some experiments made by Henry J. Miller, partly in Germany and partly in the United States, in which it was found necessary to melt metals in quantities up to 60 kg. in a vacuum or under low pressures of hydrogen, molybdenum was tried as the resistor in the electric melting furnaces. Molybdenum ribbons 16 by 0.55 mm. and 18 by 0.45 mm. were used as resistors. The furnaces were of the type shown in Fig. 1. [ ] About the heating tube, Y, are wound parallel resistors of molybdenum ribbon from the water-cooled electrodes, E1, E2. The whole is within a copper container having outlets for the removal or introduction of gases and a window, W, for observation, the space about the heating tube and electrodes being filled with insulating material. The life of the molybdenum used as the resistor was found to depend very much on the manner of using it, its failure being due in some cases to thinning by evaporation or chemical reaction and in others to hardening, which prevented it from following the expansions and shrink¬ing of the heating tubing without cracking. As such failures are often rather expensive in commercial work, it was thought worth while to determine the causes. The factors influencing the behavior of molybdenum resistors used in this manner may be briefly stated as follows:

Jan 1, 1928

By S. Edward Drummond, Charles D. Haynes, Stephen H. Stow

This paper is a preliminary report on the occurrence and distribution of economically interesting heavy minerals (kyanite, sillimanite, staurolite, zircon, monazite, ilmenite, leucoxene, rutile) in sands from the sea floor surface of the offshore area, Alabama-Mississippi. Weight percent of heavies derived from the +60 portion of 97 samples is contoured in [Fig. 1]. Five hundred grains from 42 of the heavy mineral separates were identified and sized microscopically; the data were converted to weight percent for each mineral species and are summarized in [Table 1]. Heavy Mineral Distribution In the Gulf, there is a general westward decrease [(Fig. 1)] in maximum abundance of heavies from 2.4% north of Sand Island at the mouth of Mobile Bay to slightly over 1.0% south of Petit Bois Island and a corresponding decrease in the Mississippi Sound from 1.4%, north of Dauphin Island to slightly over 0.25% north of Horn Island. Average concentrations of heavies for different areas are found in Table 1. There is westerly longshore transport in this area; the interaction of the longshore current with discharge from Mobile Bay and disruptions of the current by Sand Island, possibly aided by a shoaling effect, appear to be the cause of the preferential deposition and concentration of heavies (2.4%) north of Sand Island in 10 to 14 ft of water.

Jan 1, 1977

By A. C. Fieldner, Lester L. Hirst, Henry H. Storch

Experimental work on liquefaction of coal was taken up by the Bureau of Mines in 1936 when it became evident that a prudent policy from the national point of view should include preparation for the time when gradual exhaustion of petroleum resources would require supplementing the growing demand for motor fuel with gasoline and diesel oil from coal. At that time (1936) certain foreign nations that had no home sources of petroleum, especially Germany, England, and Japan, were conducting active research and at least two of them were producing liquid fuel from coal on a commercial scale. Germany was reported to have an annual producing capacity of 800,000 metric tons of gasoline per year, and England had just put into operation the Billingham plant of Imperial Chemical Industries for the hydrogehation of bituminous coal and tar by the Bergius-I.G. process. The annual capacity of this plant was about 150,000 long tons of gasoline per annum (3500 bbl. per day). With these developments taking place in foreign countries, it seemed important to undertake a long-range program of fundamental research in this country to establish a sound groundwork for the evaluation of foreign work on synthetic liquid fuels and at the same time to obtain data on the oil yields and operating difficulties using various kinds of American coals and lignite to the hydrogenation process. The results of such research would be useful in determining the yields and quality of liquid products obtainable from various coals so that American industry would be in position to select the most suitable coals and make rapid progress in establishing this new industry when the commercial need should arise. It was hoped, also, that progress in a better understanding of the chemistry of coal hydrogenation would reduce the cost of the process materially. To carry out this program, a small continuous unit capable of hydrogenating 100 Ib. of coal in 24 hr. was installed at the Central Experiment Station of the Bureau of Mines at Pittsburgh, Pa. Small steel autoclaves or bombs of 0.3 gal. (1.2 liters) capacity also were used for batch-hydro-genation experiments in the study of the chemical fundamentals of the process. Much valuable assistance was obtained in planning the experimental program and designing the equipment from the Fuel Research Station of Great Britain and the Fuel Laboratories of the Mines Department of Canada, where such investigations had been in progress for several years. Equipment and General Procedure of Research The industrial liquefaction of coal by the Bergius-I.G. hydrogenation process as practiced at Billingham, England, from

Jan 1, 1944

By Lester L. Hirst, Henry H. Storch, A. C. Fieldner

Experimental work on liquefaction of coal was taken up by the Bureau of Mines in 1936 when it became evident that a prudent policy from the national point of view should include preparation for the time when gradual exhaustion of petroleum resources would require supplementing the growing demand for motor fuel with gasoline and diesel oil from coal. At that time (1936) certain foreign nations that had no home sources of petroleum, especially Germany, England, and Japan, were conducting active research and at least two of them were producing liquid fuel from coal on a commercial scale. Germany was reported to have an annual producing capacity of 800,000 metric tons of gasoline per year, and England had just put into operation the Billingham plant of Imperial Chemical Industries for the hydrogehation of bituminous coal and tar by the Bergius-I.G. process. The annual capacity of this plant was about 150,000 long tons of gasoline per annum (3500 bbl. per day). With these developments taking place in foreign countries, it seemed important to undertake a long-range program of fundamental research in this country to establish a sound groundwork for the evaluation of foreign work on synthetic liquid fuels and at the same time to obtain data on the oil yields and operating difficulties using various kinds of American coals and lignite to the hydrogenation process. The results of such research would be useful in determining the yields and quality of liquid products obtainable from various coals so that American industry would be in position to select the most suitable coals and make rapid progress in establishing this new industry when the commercial need should arise. It was hoped, also, that progress in a better understanding of the chemistry of coal hydrogenation would reduce the cost of the process materially. To carry out this program, a small continuous unit capable of hydrogenating 100 Ib. of coal in 24 hr. was installed at the Central Experiment Station of the Bureau of Mines at Pittsburgh, Pa. Small steel autoclaves or bombs of 0.3 gal. (1.2 liters) capacity also were used for batch-hydro-genation experiments in the study of the chemical fundamentals of the process. Much valuable assistance was obtained in planning the experimental program and designing the equipment from the Fuel Research Station of Great Britain and the Fuel Laboratories of the Mines Department of Canada, where such investigations had been in progress for several years. Equipment and General Procedure of Research The industrial liquefaction of coal by the Bergius-I.G. hydrogenation process as practiced at Billingham, England, from

Jan 1, 1944

By M. H. Merriss

Some years ago, at the plant of the Baltimore Copper Smelting & Rolling Co., the receipt of large quantities of copper blister running high in lead, nickel, and arsenic resulted in the formation of a great amount of very foul slag, in the anode furnaces. A typical analysis of this slag was: Gold, oz. per ton......... 0.09 Arsenic, per cent.......... 0.60 Silver, oz. per ton......'.. 13.20 Antimony, per cent........ 0.50 Copper, per cent......... 19.50 Silica, per cent............ 28.30 Lead, per cent........... 11.90 FeO, per cent............. 19.20 Nickel, per cent.......... 4.60 CaO, per cent............. 1.60 The problem was to get out the copper in marketable form, to save the gold, silver, and particularly the nickel, and to get rid of as much as possible of the lead, arsenic, and other elements that were valueless to the Baltimore plant. In a copper refinery that does not take custom material for matte smelting, the usual method is to smelt the anode slag with coke in a reducing furnace, the black copper thus formed being sent back to the anode furnaces; this was the custom at Baltimore. An average anode slag will contain, perhaps, 40 per cent. copper and such small quantities of lead, nickel, etc., that smelting will get rid of most of these impurities in the black-copper furnace slag. To treat such an impure slag in this way, however, would result in a large nickel loss, and would send back to the anode furnaces all the lead and nickel not so lost, where it would be slagged off again and returned to the black-copper furnace as a slag still more concentrated in impurities. The result would probably be a constantly increasing amount of anode slag containing a likewise constantly increasing percentage of impurities. To avoid such a disastrous closed circuit some other process had to be devised. A small multiple-tank room, built for impure copper as an adjunct to the main series electrolytic refinery, was available, so the following standard process was suggested:

Jan 1, 1924

By Lester L. Hirst, Arno C. Fieldner, Henry H. Storch

EXPERIMENTAL work on liquefaction of coal was taken up by the Bureau of Mines in 1936 when it became evident that a prudent policy from the national point of view should include preparation for the time when gradual exhaustion of petroleum resources would require supplementing the growing demand for motor fuel with gasoline and diesel oil from coal. At that time (1936) certain foreign nations that had no home sources of petroleum, especially Germany, England, and Japan, were conducting active research and at least two of them were producing liquid fuel from coal on a commercial scale. Germany was reported to have an annual producing capacity of 800,000 metric tons of gasoline per year, and England had just put into operation the Billingham plant of Imperial Chemical Industries for the hydrogenation of bituminous coal and tar by the Bergius-.I.G. process. The annual capacity of this plant was about 150,000 long tons of gasoline per annum (3500 bbl. per day). With these developments taking place in foreign countries, it seemed important to undertake a long-range program of fundamental research in this country to establish a sound groundwork for the evaluation of foreign work on synthetic liquid fuels and at the same time to obtain data on the oil yields and operating difficulties using various kinds of American coals and lignite to the hydrogenation process. The results of such research would be useful in determining the yields and quality of liquid products obtainable from various coals so that American industry would be in position to select the most suitable coals and make rapid progress in establishing this new industry when the commercial need should arise. It was hoped, also, that progress in a better understanding of the chemistry of coal hydrogenation would reduce the cost of the process materially. To carry out this program, a small continuous unit capable of hydrogenating 100 lb. of coal in 24 hr. was installed at the Central Experiment Station of the Bureau of Mines at Pittsburgh, Pa. Small steel autoclaves or bombs of 0.3 gal. (1.2 liters) capacity also were used for batch-hydrogenation experiments in the study of the chemical fundamentals of the process. Much valuable assistance was obtained in planning the experimental program and designing the equipment from the Fuel Research Station of Great Britain and the Fuel Laboratories of the Mines Department of Canada, where such investigations had been in progress for several years. EQUIPMENT AND GENERAL PROCEDURE OF RESEARCH The industrial liquefaction of coal by the Bergius-I.G. hydrogenation process as practiced at Billingham, England, from

Jan 1, 1944

By B. O. Pickard

With more than a score of shafts and numerous stope openings to the surface, all inter-connected underground; with underground temperatures high, often exceeding 100' wet bulb; with an ore presenting a dust health-hazard; with certain rocks giving off inert gases; with an altitude of 6000 ft. above the sea level and a dry desert climate, the Tonopah mines offered an interesting problem to the student of metal-line ventilation. Tonopah is not an old mining district, relatively speaking. It was discovered in 1900 and Tonopah soon was a boom camp. Ry 1910 the mines of this district had paid many millions of dollars in dividends. At the time of the 1921 ventilation study, mining had passed its peak of production and the operators were striving to reduce costs, to discover new orebodies, and to attract desirable workmen. In 1925, the camp was operating on a still less prosperous basis, but the several managements had not relaxed in their efforts to keep the mines on a paying basis, neither had they lost their faith in the ability of the mines and the price of the silver to "come back." Early in the fall of 1921 the Bureau of Mines was invited by the mine operators at Tonopah, Nev., to make a detailed study of the underground air conditions in the Tonopah silver district. D. Harrington, chief engineer of the Safety Service Division of the Bureau, who was then directly supervising the ventilation studies, detailed district engineer B. 0. Pickard, mining engineer E. D. Gardner, surgeon C. E. Kindall, and petrographer IT. Insley to carry on the study. G. S. Rice, as chief mining engineer of the Bureau of Mines, was in general charge of the work. Upon the completion of the study each operator was furnished a report on conditions in his mine. In 1925, a supplemental study at Tonopah was made by the district engineer at the request of several of the operators, and each operator advised on the changes in his respective air conditions and recommendations for improvements. Recently, several of the operators gave the

Jan 1, 1927

By JAMES H. McGRAW

P UBLZCLTY and engineers do not mix. In the very words of my subject, there is an apparent contradiction. In the past, publicity has been abhorrent to the engineer. It seems to be true that the engineer, because of his training or his background, has developed a state of mind which omits publicity. At any rate he has done a poor publicity job for himself. The average engineer is self-conscious; he ought to be class-conscious. If T should ask the men in this hall to get up one by one and tell who they are and what they have done, there would be an instinctive reaction in the mind of each man-a feeling that this was out of place. If I should ask each man to get up and tell something about his neighbor, I should find that each neighbor, once he got acquainted with the man next to him and understood what he was doing, would be as human and as generous-hearted in telling about his brother engineer as is any professional man.

Jan 1, 1920

By Richard L. Stowe

Four NX-diameter holes were diamond-drilled in competent granite. Samples of the recovered core were used in laboratory tests. A borehole, plate-bearing device known as a Goodman jack was used to perform load deformation tests on the rock in the core hole. The majority of samples used in the laboratory tests were taken from depths in the hole at or within 5 ft of those at which the plate bearing tests were made. Borehole camera records, compressional and shear wave velocities, and densities were measured. Dynamic elastic constants were computed for the in-situ material, while comparative data (except camera records) were obtained in the laboratory. These data were examined to evaluate the significance of the in-situ modulus of deformation (Ed), the value computed from Goodman jack tests. Average test results show an excellent correlation between in-situ and laboratory data. The ratio of laboratory to field deformation modulus ranges from 9.82 to 7.21 for 3,000 and 9,000-psi stress levels, respectively. The dynamic modulus ratio, ED field/Ep lab, is 1.02; the compressional wave velocity ratio, V8 field/V8 lab, is 0.94; the shear wave velocity ratio, V, field/V, lab, is 1.12; and the density ratio, field [y/y] lab, is 0.95.

Jan 1, 1973