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By L. A. Pursell

Environmental constraints can both delay and raise the cost of a major plant addition, often requiring a complete reevaluation of the plant site and the proposed project. In this case history, steps are presented which were followed in applying for environmental permits for a major addition to a lime plant. Methods are described for determining expected emission increases and for selecting the best control technology for each source. The description progresses through pre-application conferences with control agencies, the formal application procedure, computer modeling the air quality impact, and the methods followed in obtaining a favorable determination.

Jan 1, 1983

By Paul L. Horrer

Costly damage by severe wave attack to many engineering structures has illustrated the need for a consideration of the nature of wave action in plans for offshore drilling operations. Using wave data it is possible to answer questions pertaining to engineering problems such as platform elevation, structure orientation, and expected wave forces. For locations where wave records are not available a technique can be used to obtain information about wave characteristics from past meteorological data and near shore submarine topography. Forces exerted on structures by waves may be divided into four parts. A completed study is given in which frequencies of various wave heights and maximum frictional drag forces are computed for a typical offshore drilling site. INTRODUCTION Waves of tremendous proportions accompanying hurricane winds crash against breakwaters and other offshore structures causing untold damages. Wave forces exerted on structures at these times are enormous, as shown by past records of incidents where massive portions of breakwaters have been broken off and moved by waves. On other similar occasions, whole structure; have been unloosed and smashed or floated away. These incidents, which seem almost incredible, serve to illustrate the great amount of energy contained in large waves, and to show that this energy results in powerful forces destructive to offshore installation~ which are not designed sufficiently strong to withstand wave attack. In the past the expected frequencies of waves having various characteristic.% have rarely been considered in the design of structure affected by wave action. As a result, many structures have failed to accomplish the purpose for which they were designed or have collapsed under wave attack. Others have been constructed to withstand greater wave energy than is ever encountered, with resulting waste of material and construction time. In this study an analysis is made of the frequencies of waves having different characteristics which affect the plans for offshore drilling installations. After such an analysis the erection of these structures can proceed with less risk involved and with more efficiency and economy. ENGINEERING ASPECTS In the offshore drilling program wave forces play an extremely important part in design and construction of drilling rigs in shallow water. The design of a platform or other structure from which drilling equipment is operated is critical, becauze any damage to the platform may endanger personnel and result in complete loss of equipment. Since a platform built too close to the water would be battered by breakers, and one built unnecessarily high would involve undue expense, it is necessary to know the most desirable elevation at which the platform should be erected. This is only one of many questions about structural planning which can be answered using existing technique for determining wave characteristics. The purpose of efficient design for the portions of many types of offshore structures which are acted upon by wave forces is the same as that of all designs which deal with frictional forces of a fluid on a solid. For these structures the problem is comparable to that encountered by undersea craft moving through water, except that in the case of a fixed structure the force is produced by the water moving past the model. For off shore sructures which are extremely rigid the frictional forces may be nearly negligible compared with the impact or shock forces imparted by breaking waves. In all case; the better design is that which offers the least resistance to the opposing forces. From a consideration of wave forces, each drilling structure varies in efficiency depending upon the type and amount of superstructure in contact with the waves. For example, round piling and bracing offer less resistance to wave forces than do I-shaped ones. All network superstructure such as cross bracing should be kept to a minimum and at as low an elevation as possible, so that it will not expecience the pressure exerted at the tops of breaking waves. Models of proposed structures can be tested in wave tanks and in the field to ascertain the efficiency of specific designs. Past experience in beach and shoreline engineering has shown that, although changes in the topography of the bottom very near shore do not seem to be occurring, the natural forces involved may be in a delicate balance such that a static state exists. Interruptions of any of these natural forces by erecting offshore structures are likely to cause undesirable effects. Changes in beach profile result partly from sediment being brought into suspension by the orbital motion of waves and partly from the transport of sediment by longshore currents. With the erection of an offshore structure and consequent change in the combined effects of these two forces, unfavorable deposition upon, or erosion of, the bottom at the site may occur. Therefore, combination wave and current studies are essential for the solution of problems involved in the design of most marine structures. TECHNIQUE FOR OBTAINING WAVE INFORMATION In determining the probable effect of wave action on an offshore drilling structure, it is first necessary to know the usual frequencies of certain wave types for the given location. A technique has been developed which provides a means for obtaining information about wave characteristics in the

Jan 1, 1949

By Paul L. Horrer

Costly damage by severe wave attack to many engineering structures has illustrated the need for a consideration of the nature of wave action in plans for offshore drilling operations. Using wave data it is possible to answer questions pertaining to engineering problems such as platform elevation, structure orientation, and expected wave forces. For locations where wave records are not available a technique can be used to obtain information about wave characteristics from past meteorological data and near shore submarine topography. Forces exerted on structures by waves may be divided into four parts. A completed study is given in which frequencies of various wave heights and maximum frictional drag forces are computed for a typical offshore drilling site. INTRODUCTION Waves of tremendous proportions accompanying hurricane winds crash against breakwaters and other offshore structures causing untold damages. Wave forces exerted on structures at these times are enormous, as shown by past records of incidents where massive portions of breakwaters have been broken off and moved by waves. On other similar occasions, whole structure; have been unloosed and smashed or floated away. These incidents, which seem almost incredible, serve to illustrate the great amount of energy contained in large waves, and to show that this energy results in powerful forces destructive to offshore installation~ which are not designed sufficiently strong to withstand wave attack. In the past the expected frequencies of waves having various characteristic.% have rarely been considered in the design of structure affected by wave action. As a result, many structures have failed to accomplish the purpose for which they were designed or have collapsed under wave attack. Others have been constructed to withstand greater wave energy than is ever encountered, with resulting waste of material and construction time. In this study an analysis is made of the frequencies of waves having different characteristics which affect the plans for offshore drilling installations. After such an analysis the erection of these structures can proceed with less risk involved and with more efficiency and economy. ENGINEERING ASPECTS In the offshore drilling program wave forces play an extremely important part in design and construction of drilling rigs in shallow water. The design of a platform or other structure from which drilling equipment is operated is critical, becauze any damage to the platform may endanger personnel and result in complete loss of equipment. Since a platform built too close to the water would be battered by breakers, and one built unnecessarily high would involve undue expense, it is necessary to know the most desirable elevation at which the platform should be erected. This is only one of many questions about structural planning which can be answered using existing technique for determining wave characteristics. The purpose of efficient design for the portions of many types of offshore structures which are acted upon by wave forces is the same as that of all designs which deal with frictional forces of a fluid on a solid. For these structures the problem is comparable to that encountered by undersea craft moving through water, except that in the case of a fixed structure the force is produced by the water moving past the model. For off shore sructures which are extremely rigid the frictional forces may be nearly negligible compared with the impact or shock forces imparted by breaking waves. In all case; the better design is that which offers the least resistance to the opposing forces. From a consideration of wave forces, each drilling structure varies in efficiency depending upon the type and amount of superstructure in contact with the waves. For example, round piling and bracing offer less resistance to wave forces than do I-shaped ones. All network superstructure such as cross bracing should be kept to a minimum and at as low an elevation as possible, so that it will not expecience the pressure exerted at the tops of breaking waves. Models of proposed structures can be tested in wave tanks and in the field to ascertain the efficiency of specific designs. Past experience in beach and shoreline engineering has shown that, although changes in the topography of the bottom very near shore do not seem to be occurring, the natural forces involved may be in a delicate balance such that a static state exists. Interruptions of any of these natural forces by erecting offshore structures are likely to cause undesirable effects. Changes in beach profile result partly from sediment being brought into suspension by the orbital motion of waves and partly from the transport of sediment by longshore currents. With the erection of an offshore structure and consequent change in the combined effects of these two forces, unfavorable deposition upon, or erosion of, the bottom at the site may occur. Therefore, combination wave and current studies are essential for the solution of problems involved in the design of most marine structures. TECHNIQUE FOR OBTAINING WAVE INFORMATION In determining the probable effect of wave action on an offshore drilling structure, it is first necessary to know the usual frequencies of certain wave types for the given location. A technique has been developed which provides a means for obtaining information about wave characteristics in the

Jan 1, 1949

By J. L. Smith, A. L. Albee

This article presents a series of guidelines by which the geologist can evaluate the likelihood of surface faulting and its probable extent at any given site in Southern California and Nevada. The information is intended primarily for geologists concerned with establishing design criteria for proposed nuclear plants. The geologic problems involved in the location of a nuclear power plant are fundamentally no different from those for other types of installations. They fall into four main categories: foundation stability, landslides and slope stability, shaking due to earthquakes, and surface faulting. For problems in the first three categories the foundation engineer, the geologist, and the seismologist can provide criteria for plant location and design, and these problems can generally be economically handled by appropriate design measures for a project of the magnitude of a nuclear plant. However, problems in the last category — surface faulting — are more difficult to handle and require a unique evaluation. Accordingly, this paper will deal primarily with the problem of establishing design criteria for surface faulting, particularly as it affects nuclear facilities. A nuclear reactor is a power source that for greater safety is contained in a heavy, air-tight structure, just as gas, oil, water, and other power sources must be contained. Surface faulting is significant in that it may reduce the integrity of the containment by affecting critical exterior piping or by breaching of the containment. A similar significance exists relative to dams or tanks for the storage of water, gas, or oil, except that in these latter examples the breaching of the container automatically releases the fluids to do their damage. This is not necessarily the case with the rupture of a reactor containment structure because the function of the containment is totally protective, i.e., it is necessary only in the event that radioactive products are released from the reactor, and there are many other safeguards to pre- vent this release even if the containment is ruptured. At the present time, nuclear power plants must be located near large sources of water for cooling the steam generated. The construction of an industrial facility of any kind on the coast line is esthetically distasteful to most people since, unfortunately, there is not enough coast to fulfill all the needs and all the desires of all the people. In most cases where industrial facilities encroach on the lives of citizens, there is no mechanism other than zoning laws by which a person can effectively protest. But in the case of a nuclear facility, the public hearing required by the Atomic Energy Commission provides a forum for dissent, as in recent case histories, and the question of safety provides objectors with a weapon for fighting the construction of the plant. The nature of a public hearing for a nuclear plant is such that the prospective owner and operator must prove that there is no undue hazard, whereas the objectors need only demonstrate that there is a reasonable doubt. It is in this situation that geology becomes the Achilles Heel of nuclear power plant location. For his investigation, the geologist has natural exposures of rock at the ground surface and a limited number of trenches and drill holes to give him a fairly complete picture of the distribution of the various rock types. From the surficial data, he must infer three more dimensions — depth below the surface, past time, and future time. Unlike many problems faced by engineers, the geologist has only this one set of data from which to reach a conclusion — he is unable to reproduce the natural sequence of events in order to obtain another set of data for comparison. Hence, by the very deductive nature of a geologic conclusion, it is difficult to prove a geologic conclusion beyond a reasonable doubt even to other geologists — and perhaps one should say especially to other geologists because the experience and background of a geologist will strongly influence his conclusion, and no two geologists have exactly the same experience and training. The engineer and the public official would like the geologist to conclude that faulting cannot occur at a given site or to assign a numerical value to the probability of its occurrence — but no responsible geologist can do either of these things. Since government officials and others must make decisions that affect the public safety, it would seem that the geologic profession must attempt to establish criteria and

Jan 1, 1968

By Arnold Hoffman

A RESPONSIBLE steel executive recently declared that scrap shortages, despite fantastic prices reaching up to $50 per ton, are responsible for the loss of 140,000 tons of steel a month and that in March 1947 alone 25 more steel furnaces could have been operating were it not for scrap scarcities. His answer to this serious situation was to ask for a speedier flow of scrap and also abolition of Government control over pig iron distribution. It would be more logical, perhaps, if an answer to this growing problem of scrap deficiency were sought within the steel industry itself. As long ago as 1933, L. B. Lindemuth, a consulting steel metallurgist, warned the steel industry that a shortage of scrap was inevitable and that beyond 1938, adequate supplies for open-hearth furnaces could not be expected. The outbreak of war, with consequent phenomenal demands on the industry, accelerated production of steel and further worsened the scrap situation. Today we are suffering from a condition which could have been prevented had the industry been more far-seeing and provided for an inevitable contingency. However, better late than never, and measures can now be taken to alleviate permanently scrap shortages in the future. This can be done by greater utilization of heavy sinter which experience proved is an excellent substitute for scrao and lump ore.

Jan 1, 1947

By F. W. Bradley

MY first Nevada City mining reminiscence is one of seeing Capt. Thomas Mein, over 52 years ago, in the old Wyoming mill on Deer Creek about a mile below the town of Nevada City. Captain Mein was then superintendent of the Wyoming mine, where the old fashioned Cornish pump was used, as well as hurdy-gurdy water wheels for power. This mill was one of the typical, up-to-date mills of that time and consisted of stamps, fed by Chinese hand feeders, who also cobbed the ore down to a small enough size to be fed into the mortars. Stamps at that time were of light weight and crushed about one ton to one and a half tons to the stamp, the pulp going over plates, then into sluices with self-raising gates. When a sluice became full the pulp was shut off and directed into the parallel sluice, also with a self-raising gate. The concentrate thus collected in the sluice was shoveled out and carried to Cornish buddles and there cleaned up, preparatory to being sent to a local custom chlorination works.

Jan 1, 1929

By Richard J. Robbins

Mechanical moles have developed through a tedious process of evolution. At times it has seemed that tunnel borers have been subject to the same Darwinian rules of evolution as their zoological namesakes who, despite their efficiency, are highly specialized and still restricted to soft soil conditions near the surface of the ground. HISTORICAL HIGHLIGHTS The Robbins Co. began its work in this field in 1947 with the development of a twin-bore continuous coal miner. Although these machines were used primarily in coal, two of the early prototypes were used to bore tunnels through shale. Disk cutters were first used on these machines and showed promising results as core breakers between drag-bit kerfs. In 1953, James S. Robbins and Assocs. undertook the development of a 25-ft 9-in.-diam circular tunnel borer for Mittry Construction Co. to be used at Oahe Dam in South Dakota (Fig. 1). This is believed to be the first rock tunnel-boring machine built since the end of the 19th century when short sections of the Channel tunnel were successfully bored in chalk from both the English and French shores. Another Oahe Dam machine was built in 1955, and then a series of three small-diameter machines for the company's first real experience with medium-hard and hard rock (Fig. 2) None of these three could be considered a success, although they laid the groundwork for the success that followed. Interbedded shale and limestone in Pittsburgh and hard limestone in Chicago quickly pointed up the weaknesses in these machines which were used by Perini, Dravo, and Healey. Among the problems were the high breakage rate of tungsten-carbide drag bits, too much flexibility in the drive shafts, failure of high-pressure hydraulic systems, chain-conveyor failure, and general lack of rigidity and strength. In 1956 another attempt at medium-hard and hard rock-boring proved this time to be a success and a significant turning point in the development

Jan 1, 1970

On the following pages are abstracts of papers published by the Institute during the year 1935 as TECHNICAL PUBLICATIONS and CONTRIBUTIONS, papers in bound volumes appearing for the first time, and papers in MINING AND METALLURGY. For abstracts of papers that appeared in bound volumes in 1935 but that were published as TECHNICAL PUBLICATIONS in 1934, see the YEAR BOOS dated January, 1935.. Many of the TECHNICAL PUBLICATIONS have been reprinted in bound volumes. Information regarding this disposition, and number of pages in each paper, may be found in the list beginning on page 64. Volume numbers are given as listed at the beginning of the index, page 71. The abstracts are grouped as follows: [Page Metal Mining 17 Uses of Metals 23 Milling and Concentration 23 Iron and Steel Division 26 Nonferrous Metallurgy (Reduction of Ores)...: 34 Institute of Metals Division (Founding and Metallography of Nonferrous Alloys) 36 Page Coal Division 43 Petroleum Division 50 Industrial Minerals Division (Nonmetallics) 57 Mining Geology 60 Mineral Industry Education Division 62 Geophysical Prospecting 62]

Jan 1, 1936

By Jack Parker

The White Pine mine site lies five miles south of Lake Superior in Ontonagon County, Mich. Copper sulfide, mixed with some native copper, is mined by a room-and-pillar system from gently dipping Upper Kewee-nawan sediments. Depth of mining now varies from 700 to 1800 ft and the ore body continues to a depth of at least 3400 ft. An area roughly 21/2 miles square has already been mined. Mining height has varied from 61/2 to 22 ft. A rock mechanics program was set up in late 1963 to promote safety and mining efficiency. This note reports some of the findings. Rock Strength Compressive strength of small, dry specimens of sandstones, siltstones, and shales from the ore zone varies from 20,000 to 30,000 psi. This is intermediate between the softer coal mine sediments and the meta-morphic and igneous rocks of hard rock mines. Annual Cycle of Rock Failure Since 1963, every roof and pillar failure involving more than a few tons of rock has been examined and documented. Some 1500 stations have been installed for measuring convergence, -c1/1000 in., with Invar extensometers. At first it was thought that there was some kind of a cycle of roof failures; perhaps annual, perhaps even elated to the moon or to earth tides, but records (see

Jan 1, 1971

By Oliver Bowles

A HEAVY gel of bentonite clay has been proposed as an effective lubricant to speed down the ways to sea, river, or lake, the mighty cargo ships now hitting the water at the rate of about three a day. Another unusual application of a nonmetallic mineral is in food conservation, for the claim has been made that the next new item on the menu for poultry and rabbits will be vitamin tablets prepared from mont-morillonite clay. These uses have minor importance but illustrate not only the diversity in utilization, but the notable trend in 1942 toward mobilizing nonmetallic minerals for the war program. Although occupying less headline space than iron, steel, copper, aluminum, magnesium, and other metals, the nonmetallics are filling important emergency needs. Mica and quartz crystal are essential to communication; asbestos is urgently needed in fireproof heat and electrical insulation; and strontium minerals are utilized in the manufacture of signal flares and tracer bullets.

Jan 1, 1943

(The following list contains the names of those members of the Institute of whose connection with military service. we have only recently become acquainted; it also includes the names of a few who have recently been promoted or transferred. A complete list was published in the Year Book, issued as a supplement of the Bulletin for March, 1918.) ADAMS, HENRY, Major, Assistant to Department Engineer, North-eastern Dept. ALINE, P. A., Co. C, 316th Supply Trains. * Low-cost cottage construction in America; a study based on the housing collection in the Harvard Social Museum, by Winthrop A. Hamlin. Cambridge, Mass., Harvard University, 1917. (Publications of the Department of Social Ethics, No. 7.) 30 pp., 4 charts. Illus.

Jan 5, 1918

By O. J. Hollister

Jan 1, 1888

Jan 1, 1970

By T. B. Nolan, R. N. Hunt

In terms of present metal prices, analysis of extant records of the Eureka district indicate past production of the magnitude of $200,000,000 in recovered silver, lead, and gold. Production to date has been thoroughly oxidized ore from massive replacements, fissures, manta, and pipe-like bodies-in large part from the massive Eldorado (middle Cambrian) and Hamburg (middle to late Cambrian) dolomite horizons. In the productive area of about 6 square miles carbonate rocks comprise 80 per cent of the section, which includes early Cambrian to late Ordovician horizons. Four-fifths or more of the district's production came from a block of Eldorado dolomite in Ruby Hill that was moved in over younger horizons on strands of a regional thrust fault. The lower 500 to 600 feet of the block was much fractured and brecciated and became host to the ores. The Ruby Hill fault, a late normal fault, limits the Ruby Hill block of dolomite on the north for its entire length of nearly a mile and terminates the downward extent and exploitation of its ores. It introduced an hiatus of some 40 years in the district's development. Drilling of the past 20-odd years, followed by underground work, has now exposed the down-faulted extension of the Ruby Hill block of Eldorado dolomite and its contained ores, dropped 1800 feet in a dip shift to depths beneath the surface of 2000 to 3000 feet. The ores at depth are the sulfide counterpart of those mined in early years on the footwall side of the fault. The ores of the district may be attributed to the same source as the intrusive quartz diorite outcropping in a limited way south of Ruby Hill but found at depth elsewhere in drill holes. The long north-south axis of the district, its anticlinal structure, its major faults, and the distribution of the intrusives and, in their relation to the surface, the ores themselves, all suggest that erosion has not cut deep enough to expose the extent of intrusives and the ores consequent upon them.

Jan 1, 1968

By AIME AIME

DOUBT in anyone's mind that this is the age of metals, industrially speaking, could easily have been dispelled by attending the National Metal Congress in Chicago, Sept. 22 to 26. Iron, copper and aluminum; zinc, lead and nickel, often alloyed with each other or with some of a dozen minor metals, make the materials without which the modern world could not run. Science, pure and applied, is doing marvels in finding new mixtures, new alloys to meet new needs; in developing new means of rolling, fabricating, casting and welding metals cheaply-and effectively. These and related matters were the subject of 100 papers presented at 33 seperate sessions of the organizations that participated in the congress.

Jan 1, 1930

By Henry F. Herley

The New Orient mine, owned and operated by the Chicago, Wilmington & Franklin Coal Co., has caused a great deal of comment and interest because of its unusual features and huge daily production. It is in Franklin County, Illinois, adjacent to the town of West Frankfort. The seam being mined is the Illinois No. 6 which in this locality is 9 to 12 ft. thick and lies approximately 500 ft. below the surface. Without fear of contradiction, it can be said that this is one of the largest coal mines in the world from a daily production standpoint. During 1928, New Orient produced 2,400,000 tons, which amounts to over 10,000 tons each day the mine operated that year. The mine is built for a capacity of 12,000 tons but has actually hoisted over 15,000 tons in one 8-hr, shift. This enormous production can perhaps be better visualized if it is realized that each day's operation depletes over two acres of coal. The general features of this mine have already been fully covered in a paper by George B. Harrington,' President of the Chicago, Wilmington & Franklin Coal Co. In a paper of the nature of Mr. Harrington's, it was unnecessary to stress any particular phase of mining conditions, consequently the ventilation problems were touched upon but lightly. In this paper an attempt has been made to describe some of the problems which have been encountered in providing adequate ventilation for the mine. Ventilating Conditions The acreage allotted to New Orient mine has a length, north and south, of approximately 6 miles, and a width, east and west, of 2 to 4 miles. A number of important considerations caused the hoist shaft, air shaft and surface plant to be located near the southeast corner of the property, instead of near the center, as is usual. During the initial phase of the mine development, the mine was ventilated through these shafts, although there was a full realization that at some future date other shafts would be required.

Jan 1, 1930

By C. H. Snyder

Tlie paper deals with details of construction of the Colmol, including improvements in design that will be incorporated in new models. These improvements are results of problems encountered and worked out in experimental operation with the unit. Also included is a descriptive plan of operating where roof and air conditions are of the worst. A summary of production results from the machine is presented. THE various units used in conventional mining are well-built. Generally the universal under -cutter, driven by approximately 50 hp, weighs approximately 25,000 lb, and is a very strong piece of machinery. The drilling machine is not as husky as an undercutter, generally is driven by approximately 15 hp, weighs about 9000 lb, but is a well-constructed, sturdy mechanism. The loader, usually 60 hp, weighs approximately 24,000 lb, and certainly is a strong, rugged unit. The working parts of all three of these sturdy conventional units have been made of tough steel alloys for some time. With the use of three machines having a combined horsepower of approximately 125, with a combined weight of approximately 60,000 lb, and with the possible inherent advantage of single purpose machines performing a single function, the use of considerable explosives has been required to complete the conventional mining cycle. It was therefore our thought, upon conception of the first Colmol,* a machine which was to do the work accomplished by the three conventional units plus explosives, that it must be a rugged mechanism. Now, after building several units, after going through many and varied experiments, and after the expense of some million-odd dollars, we find we have observed and learned nothing that contradicts our original thinking. A continuous miner, if it is to give satisfactory performance, must be a rugged piece of machinery. Ruggedness has been, and is constantly, in the minds of our engineers in designing the Colmol. Improvements where they have been required have been in the direction of more weight, more horse power, better alloys, bigger hydraulic pumps and motors; in short, always, toward more torque, greater strength, more ruggedness. Now not only the finest steel alloys are utilized but more than 100 Timken roller bearings are used. The following is some pertinent data on models being built and to be built: The low unit: Cutting height, 30 to 42 in. By changing the upper gear case the maximum cutting height can be increased to 61 in., giving a variable cutting height of from 30 to 61 in. Width of cut, 9 ft 6 in. Width of body, 75 in. over tracks. Height of body, 271/2 in. Overall length, 23 ft. Driven by three 50-hp motors or a total of 150 hp. Weight, 26 tons. The intermediate unit: Cutting height, 451/2 to 72 in. Width of cut, 9 ft 8 in. Width of body, 77 in. over tracks. Height of body, 43 in. Overall length, 26 ft. Driven by three 70-hp motors or a total of 210 hp. Weight, 35 tons.

Jan 1, 1951

By C. H. Snyder

Tlie paper deals with details of construction of the Colmol, including improvements in design that will be incorporated in new models. These improvements are results of problems encountered and worked out in experimental operation with the unit. Also included is a descriptive plan of operating where roof and air conditions are of the worst. A summary of production results from the machine is presented. THE various units used in conventional mining are well-built. Generally the universal under -cutter, driven by approximately 50 hp, weighs approximately 25,000 lb, and is a very strong piece of machinery. The drilling machine is not as husky as an undercutter, generally is driven by approximately 15 hp, weighs about 9000 lb, but is a well-constructed, sturdy mechanism. The loader, usually 60 hp, weighs approximately 24,000 lb, and certainly is a strong, rugged unit. The working parts of all three of these sturdy conventional units have been made of tough steel alloys for some time. With the use of three machines having a combined horsepower of approximately 125, with a combined weight of approximately 60,000 lb, and with the possible inherent advantage of single purpose machines performing a single function, the use of considerable explosives has been required to complete the conventional mining cycle. It was therefore our thought, upon conception of the first Colmol,* a machine which was to do the work accomplished by the three conventional units plus explosives, that it must be a rugged mechanism. Now, after building several units, after going through many and varied experiments, and after the expense of some million-odd dollars, we find we have observed and learned nothing that contradicts our original thinking. A continuous miner, if it is to give satisfactory performance, must be a rugged piece of machinery. Ruggedness has been, and is constantly, in the minds of our engineers in designing the Colmol. Improvements where they have been required have been in the direction of more weight, more horse power, better alloys, bigger hydraulic pumps and motors; in short, always, toward more torque, greater strength, more ruggedness. Now not only the finest steel alloys are utilized but more than 100 Timken roller bearings are used. The following is some pertinent data on models being built and to be built: The low unit: Cutting height, 30 to 42 in. By changing the upper gear case the maximum cutting height can be increased to 61 in., giving a variable cutting height of from 30 to 61 in. Width of cut, 9 ft 6 in. Width of body, 75 in. over tracks. Height of body, 271/2 in. Overall length, 23 ft. Driven by three 50-hp motors or a total of 150 hp. Weight, 26 tons. The intermediate unit: Cutting height, 451/2 to 72 in. Width of cut, 9 ft 8 in. Width of body, 77 in. over tracks. Height of body, 43 in. Overall length, 26 ft. Driven by three 70-hp motors or a total of 210 hp. Weight, 35 tons.

Jan 1, 1951

By William T. Folwell

The Lucky Friday mine east of Mullan, Idaho, is an outstanding example of a property in the Coeur d’Alene district where a small and insignificant- appearing silver-lead-zinc vein at the surface has changed at depth into a large vein of great importance. The Lucky Friday vein has little if any surface expression and above the 1200 level the ore shoots are small and discontinuous. Between the 1200 level and 2450 level, the lowest developed level, the main ore shoot has shown remarkable improvement on each succeeding lower level, and today the mine is one of the major lead-silver producers in the Coeur d'Alene district. History: The Lucky Friday property is on the north side of the South Fork of the Coeur d'Alene River in sections 25, 26 and 35, T. 48 N., R. 5 E., Hunter mining district, Shoshone County, Idaho. This is about one mile east of the town of Mullan, which serves the eastern portion of the Coeur d'Alene district. The southern part of the property is crossed by a branch line of the Northern Pacific Ry. and by U. S. Highway 10. This highway is the principal road crossing the panhandle of Idaho and connects the district with Spokane, Wash., on the west and Missoula, Mont., on the east. The main portal and surface plant of the Lucky Friday mine is at an elevation of 3365 ft, only a short distance above the valley floor and a few hundred feet from U. S. Highway 10, so the mine is readily accessible for year-round operation.

Jan 12, 1958

By Donald H. McLaughlin

ZEST in the search for new supplies of metallic ores and petroleum is difficult to maintain with stocks of raw materials accumulating and with over- production rightly or wrongly blamed for most of our industrial troubles. Enthusiasm over new methods of prospecting has consequently diminished and exploration programs in many fields have been drastically cur- tailed. Very naturally the effects have been felt with particular keeness in highly specialized phases of the work, such as geophysical prospecting, for the feverish scramble for new areas in which to drill beneath magnetic or electrical anomalies has abated, and there is even a lull in the firing in the battle over salt domes on the Gulf Coast. It is unquestionably an unhappy time for many of the organizations dependent on this work, but in certain respects the situation may be beneficial in correcting unsound practices that .have grown up through the necessity for haste and for quick decisions. With the restriction of the field to the more competent workers by the harsh rule of survival of the fittest, a general improvement, not only in technique but in business methods, can be expected which may go far in restoring public confidence. Geophysical prospecting in the short period that it has been utilized in North America, has suffered severely both from over-popularity and from excessive abuse. The former evil now

Jan 1, 1931