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By R. W. Raymond

The immense commercial value of the Gayley dry-blast process has been established beyond controversy. The testimony of practical blast-furnace managers, on both sides of the Atlantic, agrees that it reduces the cost of pig-iron about $1 per ton; but from the same testimony it appears that this direct economy does not by any means cover its commercial advantages—in fact, that under conditions frequently encountered in practice, it presents other benefits of even greater immediate financial importance. To this point I shall recur in a later part of the present paper. The history of the reception given to this invention, especially on the other side of the Atlantic, has repeated an experience familiar to American engineers. First, the reports of our practice were rejected as theoretically impossible, according to generally accepted notions and formulas; then the figures were reluctantly accepted; and finally the attempt has been made to explain how they could have been obtained. As to the Gayley dry blast, me Americans have been for several years in the last stage of the discussion, and the rest of the professional world is rapidly coming to it. Meanwhile, the remark has been repeatedly made that, whatever Mr. Gayley's process may turn out to be worth, it was not an invention on his part, but simply the energetic and persevering execution of a procedure already proposed by others. This question I wish to discuss first in the present paper. I. What Did Mr. Gayley Invent? Realizing that this is not the place for detailed argument on an issue of patent law, I shall not undertake to quote and criticise the publications prior to Mr. Gayley'a first patents. It may be admitted, without such critical analysis, that the possible advantages of removing moisture from the air forced into an iron blast-furnace were recognized and talked about a hun-

Jan 1, 1909

By R. M. Daelen

Mechanical science is severely tested by the demands of the iron manufacture for the varied apparatus needed to transport and to treat raw materials and products. Water has long been a favorite means of transmitting pressure for such purposes, because of its own incompressibility. Further advances in its use are the more to be expected, since mechanical improvements have steadily tended to overcome the difficulties formerly encountered in the employment of great hydraulic pressures. So long as the pressure is not higher than that which requires for plungers, etc., only ordinary stuffing-boxes, with hemp or other similar packing, the necessary arrangements for the production and transmission of the water-pressure without leakage are very simple. But when this limit (which is, for most purposes, 50 kilos to the square centimeter) is exceeded, new conditions of construction arise, which are met in various ways, and which justify a primary division of hydraulic presses into low-pressure and high-pressure respectively. The former are used in lifting and moving weights, and employ pressures as high (in extreme cases) as 100 kilos per square centimeter; but at this point the friction between piston and hemp-packing is so great that the use of cup-leathers is already preferable. Beyond 100 kilos it becomes a necessity. The range of practicable tight packing which follows is considerable, extending to about 1000 kilos; but "high pressure" in practice is from 100 to 600 kilos, and it is to this that the present paper applies. General Classes and Types. Hydraulic transmission at high pressure usually claims consideration in case the solid mechanism, such as levers, cams, screws, and gear-wheels, would have to be too large, would involve too much friction, or could not be suitably adapted to the speed-requirements of the working-tools. Since steam is mostly the primary carrier of

Jan 1, 1893

By J. J. Jakosky

A REVIEW of the progress in applied geophysics during the recent depression years reveals marked advances over the methods employed several years ago. Of late, geophysical work has been curtailed to a Con-siderable extent in the fields of oil and base-metal exploration, its especial domains a few years ago. Greater attention has been directed toward the use of geophysical technique in other engineering problems. Constantly maintained research programs have developed new instruments and per-fected better field, laboratory and interpretation techniques based on experience and skill acquired from years of application in the older geophysical field. During the past two years, geophysical methods have been employed in problems that required information on thickness of fill materials and subsurface bedrock contours. Considerable success has been attained, with subsequent drilling checking the predicted depths within one to five per cent. In general, these problems were similar as far as the fundamen-tal physical and geological conditions were concerned, but they have varied widely in specific detail and in engineering aspects. Character-istic of the different problems are: (1) yardage and bedrock profile in gold-placer mining; (2) water supply, involving underground drainage and storage conditions; (3) bedrock contours in dam-site and other structural investigations; (4) gravel and fill yardage, and other structural features along rights of way and in rock and gravel quarrying. Of particular interest, perhaps, to mining men are the problems of gold placer deposits and water supply. Geophysical work on gold placers is of especial interest because of the present expanded activity in all phases of gold mining. The development of a suitable water supply at an economical cost is often of prime importance in insuring a successful mining venture. Particularly is this true in the arid Southwest. How-ever, the use of geophysical work in water supply is not confined to the needs of mining development.

Jan 1, 1933

By J. Ralph Finlay

In latitude 4" S., about fifty miles from the Pacific, and in the amphitheater on the west flank of the Andes, which is drained by the river Tumbez, is the ancient town and mining district of Zaruma. The town is picturesque in the extreme, perched on a ridge 1800 feet high, between two lovely mountain rivers, looking out upon neighboring hills and valleys clothed in rich green, relieved by many hamlets roofed in red tiles, and, at greater distances on all sides, upon mountain slopes of gloomy forest crowned by the bare summits of the Andes. General Description. The gold-mines, discovered in 1549, mere worked extensively by the Spaniards in the 16th and 17th centuries, until their success was curtailed by the exhaustion of the oxidized surfaceores, and the uncovering of the refractory and hard ores underneath. The industry slowly declined until it was nearly or quite at a standstill in 1878, when an unfortunate English company, organized by Chilian promoters, acquired some of the best properties and began to work them. This company, after an extravagant début, relapsed into a struggle against poverty and mismanagement, and finally collapsed in 1894. In 1896 the English mines and many others, covering most of the district, were acquired by the South American co., formerly the South American Development Co., of New York. (See Figs. 1 and 2.) The vein-formation of Zaruma is extensive and complex, and the ores are somewhat refractory. In the immediate neighborhood of the gold-bearing veins the formation seems to be altogether volcanic, consisting of rather fine-grained holocrystalline diorite; but a few miles away, on either side, some gueisses and crystalline schists are to be found. About four miles south of the mines, and beyond some intervening granites, appear

Jan 1, 1901

By Karl F. Peterson, H. K. Najarian, Robert E. Lund

PRIMARY products of the Josephtown smelter are zinc metal of various grades, lead-free zinc oxide pigments, cadmium metal, and sulphuric acid. Zinc concentrates of domestic and foreign origin are blended and desulphurized at the roaster plant. The equipment includes five, 12-hearth Herreshoff roasters and two modified Trail-type suspension roasters. The sulphur dioxide containing gases from the roasting operation are diverted to a four-unit contact acid plant for the manufacture of sulphuric acid. The roasted calcines are agglomerated by sintering on Dwight-Lloyd-type sintering machines; the sinter is crushed and sized within required limits; and the sized sinter is smelted in vertical shaft-type electro-thermic furnaces. Of the 13 electrothermic furnaces of various sizes now in operation, four are designed to produce American process zinc oxidc of various specifications; and the remaining nine furnaces are equipped with vacuum-type condensers and produce zinc metal. Papers describing the general smelting practice at Josephtown have been published by AIME. Since both High Grade zinc metal and lead-free zinc oxide pigments are produced direct from the electrothermic furnaces without need for subsequent refining, the elimination of impurities such as lead and cadmium has to be accomplished during roasting and sintering operations. To effect the producing of both High Grade and Prime Western zinc products, the roasting and sintering operations are on two separate circuits. A High Grade circuit produces finished sized sinter low in lead, cadmium, etc., for the High Grade furnaces; and the Prime Western circuit produces finished sinter destined for the furnaces producing Prime Western metal. Sintering at the Josephtown smelter differs in many important respects from the sintering practice in smelters operating horizontal retort zinc furnaces. Requirements of the electrothermic smelting furnaces define the physical characteristics of the sinter, while the chemical composition of the sinter is controlled according to the grade of metal and oxide to be made as final products. Three principal objectives in the sintering process at Josephtown smelter are: 1. To transform the zinc calcine from the roasting operations into a hard, yet porous agglomerate that will not crumble in the smelting furnace. 2. Crushing and sizing of the sinter to obtain a proper screen analysis which is normally —% in. down to +1/4 in. particle size. 3. To eliminate, particularly in the High Grade circuit, as much of the impurities such as sulphur, lead, and cadmium as possible. The sintering plant as originally built in 1930 was equipped with three standard 42 in. x 44 ft Dwight-Lloyd sintering machines. Each machine was equipped with a 15x60 in. sintering corporation fan driven by 150 hp, 900 rpm synchronous motor through a magnetic clutch and capable of delivering 30,000 cfm of air at 15 in. of water and 150°F. Each sintering machine was driven by 7½ hp dc motor with controllers for varying the speed of the machine from 8 to 32 in. per min. The pallets were cast iron and the grates of the herringbone type. The charge was mixed in a 4 ft diam x 8 ft Stehli pugmill and transported by belt conveyor, elevator and tripper conveyor to a small bin over each machine. Shortly after the start of operations the following changes were found necessary: 1. The herringbone grates which plugged very quickly and were difficult to keep clean were replaced by straight, narrow cast-iron grate bars running at right angles to the travel of the pallets. These grate bars are held in place by a center bar extending across the pallet on the 24 in. dimension and by removable retaining plates which form the sides of the pallets. 2. Mechanical grate knockers were developed in conjunction with new grate bars for continuously and automatically cleaning the grates. 3. As the cast-iron pallets cracked, they were replaced with cast-steel pallets. In 1938, the capacity of the sinter plant was increased with the installation of two 42 in. x 22 ft machines which were brought from the company's Herculaneum lead smelter. With a circulating load of some 250 to 300 pct, production of finished sinter on the 42 in. x 44 ft machines at this time amounted to about three tons of sized sinter per machine hour. In 1945, one of the 42 in. x 22 ft machines was replaced by a 60 in. x 44 ft machine of our own design. In 1948, as part of the plant-wide expansion program, the sinter plant not only was expanded but also divided into two separate plants; namely, Prime Western and High Grade circuits. The sinter destined for furnaces producing Prime Western zinc metal is made in a new plant comprising two 60 in. x 44 ft Dwight-Lloyd-type sintering machines, each having a 45,000 cfm Sturtevant fan at 18 in. water static pressure and served by an 8 ft diam x 12 ft long rotary charge pclletizer and auxiliary crushing and sizing equipment. The sinter destined for furnaces producing High Grade zinc metal and zinc oxide pigments is produced in the old sinter plant which was expanded to accommodate four of the 60 in. x 44 ft sintering machines, replacing the old sintering units. In the High Grade sinter circuit, two units of the 60 in. x 44 ft machines are used as preliminary soft sinter machines; and the remaining two units of the 60 in. x 44 ft machines are used to make finished hard sinter. Purification Theory Partial elimination of lead and cadmium in the sintering of zinc ores is common knowledge. However, by some manipulation and by taking advantage of the double circuit, it is possible to make zinc sinter which is nearly free of contaminators. Lead

Jan 1, 1952

By Louise Barton Freeman, Coleman D. Hunter

The total production of oil in Kentucky during the year 1943 reached 7,010,776 bbl., which is more than at any time since 1930. Of this total, 5,287,659 bbl. was produced from the counties west of the Cincinnati arch, 692,359 bbl. from the 18 new pools opened during the year, and 3,260,765 from the Smith Mills pool, which was discovered in August of 1942. This is an important increase in western Kentucky in spite of the low price of crude, and demonstrates effectively the desire of the industry to cooperate in meeting the increased demands made by the war. Western Kentucky Two deep tests were drilled in the Kentucky portion of the Mississippi Embayment this year. Both were drilled to test the St. Peter. One well, drilled in Marshall County by the Adams Oil and Gas Co., did not encounter any St. Peter sandstone but drilled 650 ft. of formation below the position of the St. Peter and above the true Knox dolomite. The other well, in Ballard County, was reported to have tested the St. Peter and to have been temporarily abandoned at 3069 ft. At this depth the well probably was stopped in about the same formation as the Marshall County well. No accurate information is available on the Ballard County well. Several new producing areas were added to the list of fields in the western Kentucky coal basin, in Daviess, Henderson, McLean, Ohio, Union and Webster Counties. The Smith Mills pool was enlarged and production was found in the McClosky (Ste. Genevieve) in addition to the Cypress sandstone from which much of the earlier production had been obtained. There was some interest during the year in testing the Devonian and Silurian formations in the area south and east of the western Kentucky coal basin. In the fall of 1943, a 15 to 20-bbl. well was drilled in Allen County and two more wells are now being drilled. The production was obtained from within a few feet of the base of the Chattanooga black shale, probably in the upper Silurian. One well in Simpson County was drilled completely through the Silurian section before it was abandoned. Several wells were drilled in Logan, Todd and Christian Counties to test the Devonian where it is thinned by removal of the upper formations before deposition of the Chattanooga shale. None of these wells was successful but several other locations are now being tested. The Silurian thins in like manner on the eastern flank of the coal basin as the crest of the Cincinnati arch is approached, and it is along this thinning edge that such fields as the LeGrande, Logsdon Valley, Magnolia, Bowling Green and the Barren County pools were developed. A number of wells were drilled around these old pools in an effort to extend them, some of which were successful. The wells listed this year in Larue, Hardin, Barren, Hart and Warren Counties were drilled in the search for other such fields.

Jan 1, 1944

By Louise Barton Freeman, Coleman D. Hunter

The total production of oil in Kentucky during the year 1943 reached 7,010,776 bbl., which is more than at any time since 1930. Of this total, 5,287,659 bbl. was produced from the counties west of the Cincinnati arch, 692,359 bbl. from the 18 new pools opened during the year, and 3,260,765 from the Smith Mills pool, which was discovered in August of 1942. This is an important increase in western Kentucky in spite of the low price of crude, and demonstrates effectively the desire of the industry to cooperate in meeting the increased demands made by the war. Western Kentucky Two deep tests were drilled in the Kentucky portion of the Mississippi Embayment this year. Both were drilled to test the St. Peter. One well, drilled in Marshall County by the Adams Oil and Gas Co., did not encounter any St. Peter sandstone but drilled 650 ft. of formation below the position of the St. Peter and above the true Knox dolomite. The other well, in Ballard County, was reported to have tested the St. Peter and to have been temporarily abandoned at 3069 ft. At this depth the well probably was stopped in about the same formation as the Marshall County well. No accurate information is available on the Ballard County well. Several new producing areas were added to the list of fields in the western Kentucky coal basin, in Daviess, Henderson, McLean, Ohio, Union and Webster Counties. The Smith Mills pool was enlarged and production was found in the McClosky (Ste. Genevieve) in addition to the Cypress sandstone from which much of the earlier production had been obtained. There was some interest during the year in testing the Devonian and Silurian formations in the area south and east of the western Kentucky coal basin. In the fall of 1943, a 15 to 20-bbl. well was drilled in Allen County and two more wells are now being drilled. The production was obtained from within a few feet of the base of the Chattanooga black shale, probably in the upper Silurian. One well in Simpson County was drilled completely through the Silurian section before it was abandoned. Several wells were drilled in Logan, Todd and Christian Counties to test the Devonian where it is thinned by removal of the upper formations before deposition of the Chattanooga shale. None of these wells was successful but several other locations are now being tested. The Silurian thins in like manner on the eastern flank of the coal basin as the crest of the Cincinnati arch is approached, and it is along this thinning edge that such fields as the LeGrande, Logsdon Valley, Magnolia, Bowling Green and the Barren County pools were developed. A number of wells were drilled around these old pools in an effort to extend them, some of which were successful. The wells listed this year in Larue, Hardin, Barren, Hart and Warren Counties were drilled in the search for other such fields.

Jan 1, 1944

By Charles Y. Clayton

The shank, to give good service, should not upset nor should it cause excessive wear on the various parts of the machine. To fulfill these requirements, the steel must have a certain hardness—that is, resistance to deformation. The hardness is expressed in conventional terms, as Brinell or scleroscope number. Before deciding on the hardness that is proper, several factors should be considered; the most important are: type of drill steel used (whether hollow or solid), length of steel, nature of ground, air pressure, and hardness of hammer or anvil block (usually 600 Brinell). These are not all, but they are the most cogent ones. Without doubt, it would be better to use a shank that is too soft than one that is too hard. Most satisfactory service will be obtained from shanks that are just hard enough to resist any tendency to upset. To express the proper hardness in terms of Brinell numbers would mean a great many tests over a long period of time, or a study of drill steels that are being used successfully in the various districts. To obtain some information along this line, the persons making this investigation requested, a number of companies to send to them drill shanks that had been given the usual treatment at that mine. The results of the hardness tests are given in Table 1. The hardness values given in Table 2 are those of shanks known to have been quenched in water and drawn. These results show that where water quenching and drawing are in vogue the hardness is rarely under 400 Brinell.

Jan 1, 1923

By Charles Y. Clayton

The shank, to give good service, should not upset nor should it cause excessive wear on the various parts of the machine. To fulfill these requirements, the steel must have a certain hardness—that is, resistance to deformation. The hardness is expressed in conventional terms, as Brinell or scleroscope number. Before deciding on the hardness that is proper, several factors should be considered; the most important are: type of drill steel used (whether hollow or solid), length of steel, nature of ground, air pressure, and hardness of hammer or anvil block (usually 600 Brinell). These are not all, but they are the most cogent ones. Without doubt, it would be better to use a shank that is too soft than one that is too hard. Most satisfactory service will be obtained from shanks that are just hard enough to resist any tendency to upset. To express the proper hardness in terms of Brinell numbers would mean a great many tests over a long period of time, or a study of drill steels that are being used successfully in the various districts. To obtain some information along this line, the persons making this investigation requested, a number of companies to send to them drill shanks that had been given the usual treatment at that mine. The results of the hardness tests are given in Table 1. The hardness values given in Table 2 are those of shanks known to have been quenched in water and drawn. These results show that where water quenching and drawing are in vogue the hardness is rarely under 400 Brinell.

Jan 1, 1923

By Robert S. Shoemaker

At this Symposium on Gold which is sponsored by The Metallurgical Society of AIME and the International Precious Metals Institute many distinguished authors will present the latest developments in the metallurgy of gold and in operating practices at mines and in refineries. It seems appropriate then, as the introduction to this volume to recall some of the history of gold and the metallurgical developments which have been accomplished, especially during the past 100 years and some of the people who have contributed so much to the metallurgy of gold. Of all the elements gold has been the most sought after since the earliest times. Perhaps the quotation from Virgil's Aeneid best describes man's desire for gold but Pliny the Elder also put it very well when he wrote in 79 A.D. that "Gold is the first of man's follies, silver the second". This quest for gold has markedly influenced man's history and through the efforts of the early philosophers and alchemists to turn base metals into gold the foundations for modern chemistry were laid. The pages of history literally teem with references to gold. Gold is the first metal mentioned in the Bible and was the source of Croesus wealth as well as the death of King Midas whose touch turned everything into gold. And of course almost everyone has heard of Jason's Argonauts and the golden fleece. They are the subject of one of the many drawings in Agricola's De Re Metallica published in 1556. The Argonauts were probably prospectors seeking the source of the placers in the region near-the Black Sea. The time was about 1200 B.C. and the placer miners recovered gold by trapping the particles in sheep's fleeces placed in sluices. After drying, the fleeces were shaken to recover the gold. Gold is not hydrophilic, or wetted by water and thus the oils in the wool aided in collecting the particles. Here we have perhaps the earliest reference to surface chemistry and the basis for concentration of gold by flotation.

Jan 1, 1984

By H. L. Riley, B. W. Gandrud

As far as the present writers know, this system of flotation has not been used elsewhere in this country, but in the last couple of years it has been introduced, with minor variations, at one plant in England and one in Wales. The system has been described and discussed in a number of publications. The following is quoted from an abstract of the latest of these," a paper presented at an International Conference on Industrial Combustion in 1952. On the basis of experience to date with the commercial plants, it is believed that the kerosene-flotation process incorporates all the necessary elements to make it greatly superior to anything else now available for treating of fines in wet processes of coal preparation. Additional study and investigation are still needed, however, to determine if certain phases of the process can be improved to such an extent as to make it generally satisfactory and acceptable to the industry. Further improvements will be needed with respect to the capacities of the flotation cells and the reagent consumption.

Nov 1, 1955

By John V. Beall

There is an underlying surge to mining in the Philippines." So said A. R. "Ham" Reed, general manager Itogon-Suyoc Mines, Inc., to this reporter last November. Itogon-Suyoc is a small company with a struggling gold mine, a mixed sulfide mine and some prospects. In the Republic of Philippines (ROP), politics, which have an effect on mining, create some uncertainties. By July 1974, no mining company may have more than 40% foreign ownership. The ownership provision is a matter of concern to such important companies as Atlas and Benguet Consolidated and is generally considered a deterrent to new foreign investment. Under these circumstances, Reed's comments are of interest. On foreign prospectors: Don't come in cold; find a Philippine partner or buy into a company already here. Physical conditions of exploration are tough-terrain, communications -but the mineral potential is excellent.

Jan 4, 1969

By Michael D. Martin

Pima Mining Co., managed and 50% owned by Cyprus Mines Corp., with Union Oil of California and Utah Construction and Mining Co. sharing equally in the remaining 50%, is a medium-sized open pit copper mine situated in the very active Twin Buttes mining district, 22 miles southwest of Tucson, Ariz. In 1965, a three-part paper described Pima's growth from 3,000 tpd (tons per day) in 1957 to 18,000 tpd nine years later. Within months of the completion of the last stage of this sixfold expansion, studies were being wound up on a further major expansion, this time to 30,000 tpd. This expansion is now a reality. Details of the enlargement of the crushing and concentrating plant have already been covered in a recent paper, and the present paper will cover pit engineering studies, equipment selection, and current operating practices. Key factors in top management's decision to go ahead with the latest expansion were: (1) a substantial increase in ore reserves coupled with an appreciable decrease in grade, (2) a generally favorable outlook for copper prices, and (3) better than expected performance by mine and mill equipment purchased for the expansion to 18,000 tpd. For the pit design studies, particular attention was paid to pit stability, a problem area at times in the past, and to the location and grades of the final ramp systems. In drawing up the long-term mining schedule, the attitude of the ore, with the higher grade material lying deeper, was a critical factor and considerable stockpiling of lower-grade material in the early years had to be accepted in order to keep the annual grades close to the average of the orebody. The expansion called for major purchases of mine equipment in order to gear up the mine for delivery of 30,000 tpd to the concentrator. In general, equipment chosen was of types already proven at Pima, al- though there were some exceptions to this practice. One of these excep-

Jan 1, 1969

By L. D. Mullins, W. R. Bartlett, R. H. Barham, W. L. Wahl

This paper describes an electrical model and its applicution to the analysis of four reservoirs in Saudi Arabia. The model has 2,501 mesh points and represents 35,000 sq miles of the Arab-D member. Details of modeling such as mesh size, control problems and standards of performance in matching reservoir history are discussed. The particular performance match achieved for the Arab-D rnember is presented. Details such as permeability barriers, aquifer depletion and iwerference between oil fields are given. The performance match realized in the Abqaiq pool is presented in detail. INTRODUCTION The resistor-capacitor network and associated control equipment described in this paper comprise an electrical analog of a reservoir system. Similar equipment has been used to study the transient response of reservoirs for many years. The unique feature of the model and application to be described is the extremely large size of the model and reservoir system, and the detail observed in simulating the reservoir with the model. The Arabian American Oil Co. first became interested in analog computers for simulation of oil reservoirs in 1949. Since that time, several models have been developed, each more elaborate and refined so that the reservoir system might be more closely simulated. The current model is the latest in a series designed, built and operated by the Field Research Laboratory of Socony Mobil Oil Co. in collaboration with Aramco. It has been and continues to be used to study the regional performance of the Arab-D member limestone reservoir. The Arab-D member is one of the Middle East's most prolific producing horizons.. THE MODEL The theory of simulating a reservoir system with an electrical system has been presented in the literature.1-5 Therefore, this paper will not discuss the theoretical aspect of the problem except to point out the correspondence between the fluid system and electrical system, as shown in Table 1. In general, the complete model is made up of input devices, output devices, central control and a resistance-capacitance (RC) network. At times, the RC network alone is referred to as the "model". However, it should be evident from the text which meaning is attached to the word "model". A discussion of the equipment follows. THE RESISTANCE-CAPACITANCE NETWORK The RC network consists of 2,501 capacitance decades interconnected through 4,900 resistance decades. The components are arranged to form a rectangular network of 2,501 mesh points in a 41- X 61-mesh array. Imposing the mesh grid system on the continuous reservoir system divides the reservoir into discrete areal segments. These discrete segments may be of various sizes. More precisely, the mesh size need not be uniform throughout the model. The RC network is fabricated in two sections which are connected at the top. An inside view of the "tunnel" formed by the two sections is shown in Fig. 1. The height and width of the tunnel are shown in the figure. Numerals appear along the bottom and along the back opening of the tunnel. These numbers denote the x and y co-ordinate positions of mesh points. Fig. 2 presents a rear view of one-half the model. The length dimensions of the model, as well as a rear view of the capacitor decades, are shown in this figure. The control dials used in adjusting the resistance and capacitance values on the model can be seen in the enlarged portion of the model shown in Fig. 3. The electrical capacity at any mesh point can range from 0 to 1.0 microfarads set to the nearest tenth of a microfarad. The electric resistance connecting any two mesh points can range from 0 to 9,990,000 ohms set to the nearest 1,000 ohms. External capacitors may be added to any or all mesh points if the need arises. The values of electrical resistance and capacitance are adjusted manually by manipulating the two types of decade units. INPUT EQUIPMENT A considerable quantity of equipment is used to control the input to the RC network. These input devices are

By A. Perry Thompson

I- GeneRal Distribution, AppeaRance, and Relations ........ 563 11. Data fRom MicRoscopic Examination............... 568 1. Criteria for Distinguishing Primary from Secondary Minerals...... 568 2. The Leonard Vein Filling..................... 574 Quartz............................ 575 Pyrite............................ 575 Enargite............................ 576 Covellite............................ 578 Bornite............................ 581 Chalcocite........................... 583 Chalcopyrite.......................... 586 3. The Fault-Vein Covellite..................... 587 The Speculator Ore........................ 587 The East Gray Rock Ore.....,.............. 589 4. Other Occurrences of Covellite.................. 591 111. Conclusions........................... 592 1. The Replacement of Minerals..................592 2. The Character of Mineralizing Solutions .............. 594 I. General Distribution, Appearance, and Relations Mining in Butte has seldom encountered covellite in commercial quantities. The notable occurrences, extending vertically and laterally perhaps several hundred feet, presented scattered, bladed lenses of this mineral in a matrix of quartz, pyrite, enargite, bornite, and chalcocite. But under the microscope covellite is seen to be widespread in the Butte ores, though in such small quantity that megascopic examination will not discover it. In early mining operations covellite was found in the Gray Rock vein, a member of the Blue vein system. As described by Sales,' it persisted as an occasional ore mineral, associated with quartz, pyrite, tetrahedrite, bornite, chalcocite, and minor amounts of sphalerite, from the 700-ft. to the 1,200-ft. level of the East Gray Rock and Diamond mines. Crushed quartz-monzonite and later quartz completed the vein filling between

Jan 1, 1916

By T. L. Joseph

A DEMAND for specialized knowledge has directed engineering curricula towards competency in some particular field or occupation. Preparation for life in a broad sense of completeness has received little consideration. Ways and means are needed for weaving some of the threads of liberal education into the fabric of engineering education. Any effort to develop a humanistic-social stem of engineering education will depend largely upon the content of the courses and the type of instruction offered. Many of the courses in college curricula are intended to lay a foundation for more advanced courses to be taken later by those. who specialize in some particular field. Students in other fields lack the background necessary to take the advanced courses and have too much detailed information, soon forgotten, forced upon them if they pursue the foundation courses. To develop a humanistic-social stem for engineering education existing catalogue courses selected should follow some general plan aimed towards broad educational objectives. Courses packed with detailed factual information are necessary for the stu-

Jan 1, 1947

For the seventh consecutive year, the value of nonfuel mineral raw ma¬terials produced in the US set a new record, reaching almost $20 billion-up 12.7% from the previous year, according to the US Bureau of Mines. The Bureau reported that this mineral production was the basis for about $200 billion worth of processed materials of mineral origin.

Jan 5, 1979

By Clarence Zener

Contents Page General Principles................................................................. 551 Equilibrium Diagrams......................................................... 551 Nucleation................................................................... 553 Kinetics of Phase-boundary Propagation......................................... 553 Kinetics of Growth of New Phase............................................... 556 Spheroidization............................................................... 560 Pure Iron-carbon System........................................................... 561 Formation of Pearlite.......................................................... 561 Interlamellar Spacing........................................................ 562 Pearlite C-curve............................................................. 563 Bainite Formation............................................................. 565 Formation of Martensite....................................................... 570 Loss of Tetragonality of Martensite.............................................. 570 Effect of Alloys upon Decomposition of Austenite..................................... 572 Pearlite...................................................................... 572 Bainite and Martensite......................................................... 574 Time-temperature-transformation Curves............................................. 576 Appendix A............................................................. ......... 579 Appendix B....................................................................... 580 Appendix C....................................................................... 580 The present investigation started in an attempt to understand certain details of the decomposition of austenite, and of the effect of alloying elements thereon. As the investigation proceeded it became apparent that not only these details, but all the general features of austenite decomposition, could be understood in terms of fundamental physical principles. Since the direct applicability of these physical principles has not been previously recognized, it was decided to incorporate the original results of the investigation into a review of the general subject of the kinetics of austenite decomposition. This review constitutes the present article. An extended summary of the results is given on pages 576 to 579. This article, which deals with the kinetics of phase transformations, may appropriately be considered as a sequel to two recent articles1,2 from this laboratory on the equilibrium relations in medium alloy steels.

Jan 1, 1947

By Clarence Zener

Contents Page General Principles................................................................. 551 Equilibrium Diagrams......................................................... 551 Nucleation................................................................... 553 Kinetics of Phase-boundary Propagation......................................... 553 Kinetics of Growth of New Phase............................................... 556 Spheroidization............................................................... 560 Pure Iron-carbon System........................................................... 561 Formation of Pearlite.......................................................... 561 Interlamellar Spacing........................................................ 562 Pearlite C-curve............................................................. 563 Bainite Formation............................................................. 565 Formation of Martensite....................................................... 570 Loss of Tetragonality of Martensite.............................................. 570 Effect of Alloys upon Decomposition of Austenite..................................... 572 Pearlite...................................................................... 572 Bainite and Martensite......................................................... 574 Time-temperature-transformation Curves............................................. 576 Appendix A............................................................. ......... 579 Appendix B....................................................................... 580 Appendix C....................................................................... 580 The present investigation started in an attempt to understand certain details of the decomposition of austenite, and of the effect of alloying elements thereon. As the investigation proceeded it became apparent that not only these details, but all the general features of austenite decomposition, could be understood in terms of fundamental physical principles. Since the direct applicability of these physical principles has not been previously recognized, it was decided to incorporate the original results of the investigation into a review of the general subject of the kinetics of austenite decomposition. This review constitutes the present article. An extended summary of the results is given on pages 576 to 579. This article, which deals with the kinetics of phase transformations, may appropriately be considered as a sequel to two recent articles1,2 from this laboratory on the equilibrium relations in medium alloy steels.

Jan 1, 1947

By H. C. Kenny

THE annealing or softening temperature of cold-worked copper is appreciably increased by almost unbelievably small amounts of silver. As indicated by some data in this paper, the softening temperature of high-conductivity, tough-pitch copper may be increased from 200° to 350° C. by the addition of only 15 oz. per ton (0.052 per cent) of that element. Because it has this higher annealing temperature as compared with the silver-free metal, silver-bearing copper finds considerable use in industry. For example, when hard-rolled copper is used in operations that involve soldering or tinning, silver-bearing copper insures against loss of strength, whereas silver-free copper becomes "dead soft." Yet-though several investigators, beginning with Caesar and Gerner1 in 1916, have shown that small amounts of silver do definitely raise the softening temperature of copper-data are lacking on the problem: What is the specific influence of different amounts of silver on this tem-perature? It was to help in filling this gap in the knowledge of what might be termed "alloy coppers" that the data given herein were obtained. The softening of cold-worked copper depends, of course, on a number of factors, of which the composition of the material is only one. Other highly important factors are the degree to which the material is cold-worked and the time it-is held at the annealing temperature. The method of cold working and the grain size of the metal produced are also signifi-cant. All these variables were taken into account in the investigation reported here, and the influence of silver on the electrical conductivity and on the working was also considered.

Jan 1, 1934