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By Richard Franchot

IN the inevitable conquest of the blast furnace by metallurgical science in the solution of the problem of how to make more and better iron or to burn less coke, or both, it is highly desirable first to find out why the efficiency of the furnace generally is no better than it is. The immediate need would seem to be a theory to account for the existing facts. Explanation for the quantitative results obtained in current practice has been strangely lacking. One reason for this may be found perhaps in the custom of think-ing of efficiency in terms of coke consumption. Before efficiency can be explained there should be a fairly exact knowledge of what it is. A statement of the pounds of coke used per ton of iron made may have value in indicating comparative results in smelting similar ores with similar cokes, but it tells very little of the efficiency of the operation. When the materials are different, one practice burning 1800 lb. may be less efficient than another using 2000 lb. A better measure is the pig and slag per unit of coke. What is needed is a specific description of efficiency as a' definite quantity having an exact meaning. Such description is afforded by expressing efficiencies in terms of the respective proportions of the fuel energy absorbed in and chargeable to the various actions known to be -taking place in the furnace. Concretely, the energy value of a pound of coke having 85 per cent carbon blown with air heated to 1200° F. is about 7650 lb.-cal. (13,770 B.t.u.). And the work done in smelting a pound of average iron from hematite, comprising reduction and melting with production of a half pound of free running slag from an equal weight of limestone,

Jan 9, 1926

By A. E. Martin, Gerhard Derge

IE the molecular constitution of molten slags were better known, the nature of chemical reactions in slags and between slags and metals could be better understood and as a consequence might be better controlled. Constitutional information can be obtained by studies on either the molten or the solidified slags. Valuable as the studies on solidified slags admittedly are for many purposes, especially as control methods in steelmaking, they are always of questionable value in giving information on the molecular constitution of liquid slags. However, the characteristics of molten slags such as viscosity, rates of dilfusion, and electrica1 conductivity can be determined experimentally and interpreted along with other knowledge on slag-metal and slag-gas reactions so as to provide direct information on liquid slags. Metallurgists are accustomed to regard reactions in molten slags as involving only neutral molecules, whereas it is quite possible that ionic constituents are actually involved. For example, the dissociation of calcium silicate usually is represented us Ca2SiO4 = 2CaO + SiO2 although a reasonable alternative would be to write Ca2SiO4 = 2Ca+2 + Si04-4 Such ionic dissociation has been suggested frequently without adequate experimental proof. This paper deals especially with electrical conductivity measurements on slags oi the blast-furnace type. These measurements were made to determine whether or not slags are ionized and, if so, to provide a qualitative estimate of the extent of ionization. Electrolysis experiments that indicate the identity of the ions present are also reported. Since the presence of ions has not been considered carefully in modern slag studies, the relevant literature will be reviewed. Review of Literature In 1906 Aikenl obtained a patent for a continuous process of producing iron electrolytically by passing a direct currenl through a bath of FeO.SiO2 to which iron oxide was added periodically to maintain a uniform concentration. The patent also included the addition of CaO and MgO to the bath to lower its melting point. The silicate melts involved were thus in the same system as basic open-hearth slags but with higher FeO and lower CaO contents. Electrical conductivity measurements were made on some molten silicates by Doelter2 in 1907. Natural silicates, such as

Jan 1, 1943

By Paul L. Russell

7.5-1. introduction. The possible engineering uses of nuclear explosives were recognized with the first nuclear detonation. Subsequent experiments have demonstrated the ability of nuclear explosives to move very large volumes of rock and earth efficiently and at costs below conventional earth-moving methods. The ability to package a quantity of energy equivalent to a few million tons of conventional explosive in a container approximately 20 ft long and 36 in. in diameter enables easy emplacement and thus provides the potential for excavation on scales heretofore impossible. Space does not permit detailed discussion of the many experiments with conventional high explosives and with nuclear explosives that were performed in developing the information presented here. A bibliography is included for those wishing detailed information. Material from those sources and from personal experience has been used freely. 7.5-2. Nuclear Explosives. An explosion, in general, results from the very rapid release of a large quantity of energy within a limited space. This is equally true for both conventional and nuclear explosions, although the energy is produced in quite different ways. In the case of a conventional explosive, this energy arises from chemical reactions. In a nuclear explosion, the energy is produced as a result of the formation of different atomic nuclei by the redistribution of the protons and neutrons within the interacting nuclei. Nuclear energy is of a much higher order of magnitude than chemical energy when equal masses are considered, and the release of this energy is a thousand times more rapid than the fastest chemical detonations. Explosions may be produced by fission or fusion reactions. FISSION. When a free (or unattached) neutron enters the nucleus of a fissionable atom, it can cause the nucleus to split into two smaller parts. This fission process is accompanied by the release of a large quantity of energy. The complete fission of 1 lb of uranium can produce as much energy as an explosion of 9,000 tons of TNT.

Jan 1, 1968

By Thomas Leonard Watson

In a paper read by title at the Washingtoil meeting of the Institute,' May, 1905,I discussed at considerable length the geological relations, mode of occurrence, and the genesis of the lead- and zinc-ores of the VirginisTennessee region. The present paper treats of the purely ecorlomic phases of the zinc-ores of the district,—such as methods of mining the ores, their preparation and treatment. The Albemarle coullty mines and plant were discussed in the paper referred to above, and mill not be considered here. Methods of Mining. Until very recently the mining of lead- and zinc-ores in Virginia mas limited wholly to the surface-belt of weathering. The mode of occurrence and the character of the ores to be mined were such as to demand the employment of niethods used in mining secondary concentrated ores. Accordingly, a system similar to that practiced in mining brown iron-ores was employed, being modified to meet the changed conditions. Oxidized or Soft Ores.—Up to the present time practically all the ore mined in the Virginia district has been of the oxidized or soft type;—the silicate, calamine, and the carbonate, smith-sonite; largely the former, which has been localized and concentrated at only slight depths below the surface. Because of the extreme irregularity with which the limestone weathers when stripped of the overlying residual clay, it presents a roughened surface of large and small irregular " chimneys"

Jan 1, 1907

By W. E. Rice

The ceramic industry has to do with forming or molding articles of clay, and imparting to them their characteristic properties of permanence, strength and color by subjecting them to heat treatment in kilns. This heat treatment is commonly known as "firing" or "burning." The art of firing clay ware antedates the industrial use of coal; hence wood was the fuel first used, and the earliest kilns were built to burn wood. The majority of the clay ware produced today is fired in periodic kilns that are essentially enlarged structures similar to the earliest enclosed kilns; a kiln consists of a large chamber 16 to 32 ft. dia. (or rectangular) in which the ware is charged and fired either in direct contact with flame or hot gases from the fuel, or in saggers which shield the ware from direct contact with the gases. The fuel is burned in a number of small furnaces built in the thick wall that encloses the chamber; these furnaces are from 16 to 36 in. wide and from 3 to 5 ft. long; some of them have horizontal or sloping grates, but many have no grates; the last are called "dead-bottom" furnaces. The temperature necessary to mature the charge in the kiln varies for different clays; for some it is as low as 1800°, and for others as high as 2700" F. Wood was an ideal fuel for the low temperatures that were used in early kilns; it burns freely and produces a long, clean flame, which promotes uniform distribution of the heat in the kiln; it does not coke and so restrict the passage of air through the fuel bed; the ash does not melt in the fuel bed to form clinker; and the ash that is carried into the chamber and deposited on the charge does not contain iron and sulfur to discolor the clay. The extent of the ceramic industry now precludes the general use of wood in kilns, so that today this industry is one of the large users of bituminous coal, burning more than eight million tons annually in kilns. Manufacturing plants usually are at or near the source of clay, with deposits of coal suitable for kilns occurring near the clay. The cost of coal is the largest single item of expense in the manufacture of clay ware, and, because all coals are not equally suitable for the process, the careful selection of coal is important. In this selection the desidera-

Jan 1, 1932

By W. M. Courtis

. There seems to be a well-established belief that there is an indescribable something in the appearance of gold-quartz not to be learned from books, that enables those who are fortunate enough to have acquired the power to recognize this characteristic, to pronounce at once that a certain quartz will or will not pay. The stronger this claim is made, the more certain is the claimant to be one of the self-styled practical miners. After several years spent among the gold-mines of California with practical and professional gold-miners, I have come to the conclusion that very few care to risk an opinion on a piece of quartz until some of it has been "horned out." Nevertheless, there is what the miners call a " kindly " appearance, that is more often followed by good results than is a vitreous, water-wet-looking quartz. A dark, resinous quartz seems to be most in favor, but there are so many exceptions that even quartz as " white as a hound's tooth " produces gold in some mines.. The ribbon-quartz, a laminated variety, separated by thin talc or chlorite partings, has a well-known good name. The slides of rich quartz specimens show that this parallelism is a microscopical characteristic of the only macroscopical distinction that, as a rule, these quartzes show. This is shown by Nos. 12 and 13, photographs of the richest quartz, that averaged $65 per pound. It is noticeable, also, in Nos. 7 and 9, and others. Dr. Hensoldt, of Columbia College, who prepared, excellently, a large number of my slides, and whom I have to thank for descriptions and suggestions, says of Nos. 12 and 13: "This variety of quartz differs considerably, microscopically, from the others of your locality, and is, in more than one respect, remarkable. Like the

Jan 1, 1890

By Louis Huber

DESPITE the fact that centrifugal fans were first developed for ventilating mines and that artificial ventilation was first practiced in mines, the lack of knowledge of mining men on mine ventilation in general, and on fan performances and characteristics in particular, is very much in evidence today. While it is true that mines are much better ventilated now than they were 20 to 30 years ago, we have made very little progress in the study of mine ventilation, or in mine ventilating fan design. Today the average mine operator is woefully dependent on the engineers of mine fan manufacturers when he is in the market for a fan, and this situation works to the disadvantage of both the operator and the manufacturer. The former may be imposed upon by an unscrupulous sales engineer and induced to buy a fan which is not the proper one for the mine; when it is operating it may be wasteful of power and even accessory to a serious mine disaster. More often, however, it is the fan manufacturer who is imposed on. If the operator asks the manufacturer to build for him a fan that will deliver a certain quantity of air against a certain specified pressure and requiring a specified number of horse power when operating under these conditions, the manufacturer may build a fan that will comply with these specifications to the letter. When the fan is installed it is frequently found that it is delivering a greater quantity of air against a lesser pressure or a lesser quantity of air against a greater pressure, and is requiring more horse power than specified in the first case and less than that specified in the second. In either case the operator usually upbraids the manufacturer for not meeting specifications, and refuses to pay for the fan. The trouble in either case outlined above is that the pressure necessary to force the specified quantity of air through the mine has been estimated incorrectly by the operator or his engineers. When a fan is designed and built to deliver a certain quantity of air against a certain specified resistance it will operate at its maximum efficiency only when it is operating under

Jan 2, 1926

By N. B. Davis

I . INTRODUCTION WHILE working with a number of very sticky cracking clays from western Canada the writer became interested in a study of the cause of the excessive plasticity, This led to a review of the rather bulky literature on the subject and the finding that plasticity still remains to be satisfactorily explained. Most of these investigations seem to have been carried on solely from the chemical viewpoint, the geologic aspects having been ignored. In nearly every case, the investigators have worked with the higher-grade clays of low to medium plasticity, such as the kaolins, the excessively plastic ones having generally been neglected, partly because of their limited application, yet the author believes that these are

Jan 2, 1915

By G. B. Gould

EVERY mathematical statement of a measure of anything (as distin-guished from a count) is followed by a qualification always implied if not explicity stated--that the statement is only an estimate, which may vary from absolute accuracy within certain limits, according to the accu-racy of the measuring instrument. This basic fact, so obvious to engineers, is not so well understood by many that make use of laboratory coal tests. The tolerances that must be allowed in measurements of coal quality are very important in both their commercial and engineering applica-tions-and the significance of these tolerances depends upon the use made of the laboratory coal test. Only in recent years has there been any intensive study of this ques-tion of tolerances as applied to measurements of coal quality. There is very little in our published literature on the subject, and what has been published is not, readily comprehended by those who sell coal, or buy coal and use it, unless they happen to have made a study of the subject them-selves. There is great need for more widespread understanding of what has been discovered and how it applies to the use of laboratory coal tests. What follows is an attempt to condense into a few pages the results of the major investigations so far reported, and to explain their meaning in simple nontechnical language, with the addition of some recent illustrative experiments.

Jan 1, 1937

By R. E. Zimmerman

ALTHOUGH flotation of coal is considered relatively new in the United States by coal-preparation engineers, actually it has been practiced to some extent for the past 30 years, It is practiced much more widely in Europe than in the United States. Commercial plants are operating in nearly all major coal-producing countries of the world. A froth flotation plant has been operating since 1930 at the Champion No, 1 preparation plant of the Pittsburgh Coal Co. Unfortunately the term flotation is widely used in the United States by coal-preparation engineers to designate dense medium processes of coal cleaning. As used here, flotation means those processes for cleaning fine sizes of coal in which the coal is collected in a froth or matte at or near the surface of a pulp. The refuse particles remain in the pulp. Two distinct types of flotation are practiced: froth flotation and agglomeration. FORMS OF FLOTATION The theory of the principles of flotation and of the physicochemical foundations surrounding this process has become a complex and scientific field and coal-preparation engineers contemplating use of flotation processes would do well to study the works of Gaudin, 2, 5 Taggart, 3 Zimmerman, 4 Wark, 6 Ralston, 7 Petersen. 8 Bulk Oil Flotation.-In this process the separation of mineral from gangue is accomplished by virtue of the fact that minerals of metallic lustre, as sulphides, or hydrocarbons, as coal and graphite, are wetted preferentially by oil in the presence of water and consequently pass into the interface between oil and water; while gangue or rock is wetted by water and remains in the medium. Beginning in 1860 with Haynes and later between 1897 and 1907, at least 25 patents were granted for bulk oil flotation. Large quantities of oil are required, generally 3 to 25 per cent by weight of feed, and recovery of such oil is a major problem. The Elmore process 3 (1901 and 1902) is an example of a bulk oil process, The Trent process (1902-25) has been used for the cleaning of coal on a commercial scale, According to E. W, Davidson 9 there were five such plants operating in the United States by 1925. They have since been abandoned.

Jan 1, 1950

APRIL BEGAN with increased disorder in the Ruhr and some blood-shed. The war cloud in the East disappeared, however, with the signifi- cance by the Turks of their intention to return to Lausanne to negotiate a treaty of peace with the Allies. The French occupation of the Ruhr continued during April without there being any spectacular develop-ments. Of course there was surliness on the part of the Germans. In the meanwhile the statesmen on both sides were intimating what they might give and what they might take, sounding the sentiment of their respective populaces. The British Government found that its revenue for the last fiscal year has been greatly in excess of expenses. The surplus was applied to reduction of the debt. A consequence of this development has been a reduction in British taxes for the ensuing year, which has naturally created a much better feeling in Great Britain. On the other hand the unemployment situation in Great Britain caused increasing alarm. At the begin-ning of April about 1,500,000 men were out of work and the thought was developing that this might be not merely a temporary emergency, but a long continuing condition. The uneasiness of the workers themselves began to be exhibited in increasing strikes and threats of strikes. There were important domestic events during April. The six miners who were on trial in Illinois for the Herrin massacre were acquitted, following which the State dropped further prosecutions on the ground that Williamson County is so thoroughly under labor domina-tion that justice could not be had there. The Supreme Court of the United States on Apr. 10 handed down a decision that an act of Congress fixing minimum wages for women in the District of Columbia was unconstitu-tional, being interference with the freedom of contract included within the guarantees of the fifth amendment. Advances of wages became more general during April. The leading event under this head was the action of the United Steel Corporation putting into effect an.11 per cent. increase in the wages of common labor on Apr. 16, by virtue of which the rate per hour was raised from 36 c. to 40 c. This was dictated by competitive conditions, the labor difficulties of the steel industry being due less to a scarcity of men than their disinclination to take jobs in that industry while the building and other industries were paying as high as 60 c. per hour for similar work.

Jan 5, 1923

By Stirling Huntley

With the threatened falling off in production of the lighter oil pools of the Tampico embayment in Mexico, a general search of that country for oil-producing regions has resulted in renewed activity in the region of the Isthmus of Tehuantepec, one of the first districts exploited in Mexico. Since the drilling of the first well in the San Cristobal section by the Pearson interests in 1902, drilling has been continuous, except during 1917-1921, when practically all development was stopped by the revolutionary activity. Early in 1921, a drilling campaign was inaugurated for the purpose of testing out the known salt-dome poolfi on the flanks of the salt masses, rather than on their tops where previous tests had been located. On Dec. 7, 1921, the Aguila Co., with which are consolidated the Pearson interests and which has been the only company active in developing this region, unexpectedly drilled into a sand horizon at 3015 ft. with its Conception well No. 18. The hole was unable to handle the production, as a 1400-ft. string of 121/2-in. casing was hanging in the hole, a salt-water horizon drilled through at about 800 ft., was not cemented off, and 3000 ft. of 4-in. drill stem with rotary bit was in the hole. This well's potential capacity was never determined, but it made 7000 bbl. of 25" Bé. oil through the bit and Pin. drill stem, in one of its sporadic flows before sanding up, and thus proved itself capable of the largest potential production of any well on the Isthmus. The well showed salt water before caving and sanding up with the drill stem still in the hole, and will probably never be used for production. Wells Nos. 22 and 23, drilled nearby, have proved disappointments after making good showings of oil. In the spring of 1922, Ixhuatlan wells Nos. 28 and 29, deep tests supposedly on the flank of the known salt cores in that field, went into solid salt; No. 28 at 2250 ft. and No. 29 at 2400 ft. No. 28 was continued in the salt for 1000 ft. before operations were stopped. Later comple-

Jan 1, 1923

By P. H. Dudley

When we see the magnificent passenger-trains of from 8 to 12 coaches, drawn by locomotives weighing from 100 to 110 tons, at speeds of from 50 to 60 miles per hour between terminals, to make a schedule of 45 miles per hour, and freighttrains of from 50 to 75 cars of 60,000 pounds capacity, drawn by one locomotive, it is hard to realize that it lacks a few months of fifteen years since my pioneer 5-inch 80-pound rail for the United States was laid by the New York Central aid Hudson River Railroad Co., in July, 1884, on the Harlem line. Shorter passenger-trains, of from 4 to 5 coaches, are run much faster, notably the Empire State Express, the schedule of which for the 440 miles between New York and Buffalo requires 53.3 miles per hour, calling for a running-speed, for much of the time, of from 65 to 75 miles per hour, while higher speeds are very common. On other railroads laid with my 5 1/8-inch 80-pound rail, speeds of from 60 to 75 miles per hour obtain in daily practice. On many of the important railroads east of the Mississippi high speeds of from 60 to 70 miles per hour are part of the daily service. So many instances of speeds of 90, and even 100, miles per hour have been recorded that they must be considered as likely to occur on important lines, and provision must be made for them in the track. Solid mail-trains of from 6 to 8 cars are run from New York to Chicago, 1000 miles, in twenty-four hours; and, commeneing with the present year, shorter trains are running from Chicago to San Francisco, 2000 miles, in three and one-half days. In the freight-service equally important progress has been

Jan 1, 1900

By V. R. Garfias, H. J. Hawley

FoR a number of years the senior author has been interested in the various geologic and engineering problems involved in the development of the petroliferous districts of northeastern Mexico, having in a previous paper* endeavored to present a summarized statement of the information relating to the geology and soil resources of this region. Of the many interesting geologic phenomena, perhaps those which have been the object of most speculation relate to the igneous intrusions which, in places, have a controlling influence on the accumulation of oil in commercial quantibies, a relationship which has been tentatively explained by various observers with as many interestingly different views. The authors of the present paper aim to record, in the course of a general discussion of the various viewpoints, some additional data, and present further tentative conclusions with a view to rounding out an up-to-date summary of the subject. The greater part of the area in question lies in the State of Vera Cruz, only a northwest fraction being in the State of San Luis Potosi. Vera Cruz is bounded on the north by the State of Tamaulipas, the northernmost of the Mexican States along the Gulf. The topography of the States of Tamaulipas and Vera Cruz and of Texas and Louisiana to the north, is controlled by the Gulf coastal plain which in northern Vera Cruz has an average width of about, 60 miles, the transitional topography between that of the rugged Banks of the Sierra and the lowlands of the coast being made up of a series of terraces and irregular hills and valleys. Geology and StRucture The greater part of the mainland of Mexico is made up of Tertiary and later effusive rocks and of sedimentaries of Cretaceous age. The igneous rocks form a belt from 150 to 300 miles wide, spurs of which shirt

Jan 1, 1918

By J. B. Warriner

Introduction STRIPPING is the name given to the process of removing clay, rock, or other cover from deposits of coal or ore. In this paper it is intended to cover the methods used in carrying on this operation in the anthracite coal regions of Pennsylvania. In doing this, attention will be chiefly devoted to those methods wherein practice in different sections of the region differs, or is susceptible to change or improvement, though it is intended to give as complete data as possible concerning all stages of the operation. The data from which this paper has been prepared have been collected and submitted by a committee representing the larger users of stripping methods, of which committee the writer has acted as chairman. Data and assistance have also been obtained from various mining men, engineers, contractors and manufacturers of stripping equipment, to all of whom our appreciation is clue.

Jan 1, 1917

By L. P. Teas

Although 1930 has been a year of stagnation, proration and curtailment, the Gulf Coast has measured up to its tradition in the matter of interesting and significant discoveries. Only 2 domes and 7 new structural areas were brought into the producing column in 1930, whereas, in 1929, 13 domes and one structure were added to this list, yet a total of 14 new producing horizons were proved on various domes and structures. On 5 domes new flanks were successfully tested for commercial production. The year 1930 has shown at Barber's Hill that oil in commercial quantities may exist below salt or cap. Numerous wells have been drilled through cap, or even salt itself, into good producing sands. The past year has been particularly notable in the interest and in the number of deep holes drilled. Two wells have gone below 8000 ft. in each of the states of Texas and Louisiana, and in the two states together 14 wells have gone below 7000 ft At the beginning of the year only one well was producing below 6000 ft. in coastal Texas, while at its end, 19 wells were producing or had produced. Geophysical discoveries and activity on the Coast have waned and this type of work has moved further inland. The peaks of production at Pettus, Barber's Hill, Raccoon Bend, Refugio, Orchard and at Humble, in Texas; and at Lake Barre, Port Barre, Black Bayou, White Castle and Vinton in Louisiana, were seen this year. These were new peaks for Humble and Vinton, of course, these fields having previously gone through periods of peak flank production. In Table 1 the completions listed are for the entire month of December in both years. It is remarkable that in 1930, a year of overproduction and proration, there were actually more wildcat operations at its end than at the end of 1929; but it is gratifying that the operations in the proven fields were exactly one-half what they had been at the end of 1929. The price of A grade coastal crude, or oil below 25" Bé., has been cut from $1.30 at the beginning of the year to $1.00 at its close; and B grade, or oil above 25o Bé., has been reduced from a price range of $1.15 to $1.63 down to a range of from $0.75 to $1.22. In spite of these reductions there has been no proration program on the Coast. Systematic

Jan 1, 1931

By Fred B. Brost

In 1976, a decision was made to install a conveying system to transport ore 10.3 km (6.4 miles) from the new Eisenhower mine to Twin Buttes. The system, supplied and installed by Cable Belt Ltd., of England, represents a radical departure from conventional conveyor systems. The driving tension is applied through two endless wire ropes while the belt acts only as the carrying medium. Features of the system are a single 2240-kW (3000-hp) drive and a 60° angle bend. Construction was completed in two years and full production was attained alter several mouths operation.

Jan 12, 1979

By J. E. Jopling, J. R. Chenneour, E. L. Derby, S. R. Elliott

The Marquette range, on which are situated the iron mines of Mar-quette County, together with a few in Baraga County, Mich., extends from a point 10 miles southwest of Marquette westward for 30 miles. The tracts are usually a multiple of the standard 40-acre parcel, which is the smallest government subdivision of a square mile or section. About half of the mines are held in fee, these being owned by the older mining companies. Some of them date back to about 1880, and a few are as early as 1850. During the past 40 years most of the mines opened have been on leased lands, the royalty being either for a stated amount per ton or a percentage of the selling price of the ore at the lower lake ports, or the selling price on board of cars at the mine. The first merchantable body of ore discovered in the Lake Superior district was found, in 1845, at what is known as the Jackson mine, near Negaunee. This ore was hard hematite. After unprofitable attempts had been made, in 1848, to smelt it in forges, shipments were begun to lower lake ports, which increased rapidly upon the completion of the locks at Sault Ste. Marie, in 1855, and the railroad from the mines to Marquette, in 1857. Beginning with the Pioneer, in 1858, a number of small charcoal furnaces were built to smelt a part of the product. At various points in the upper and lower peninsulas, large charcoal furnaces are still making iron from the ores of the Marquette range. In connection with these furnaces are byproduct plants. As the deposits were opened up, soft ore was encountered, but for a few years this was disregaided, as only the hard ore was used. Underground mining was begun about 1880 and during the next few years the open-pit mines producing high-grade ore were exhausted. The first mines in the district were owned by the Jackson, Cleveland, Lake Superior, Lake Angeline, Champion, Iron Cliffs, Humboldt, Republic, and Michigamme companies. Many of these companies have been merged in the holdings of The Cleveland-Cliffs Iron Co., which controls most of the tonnage of the district.

Jan 1, 1925

By Ralph E. Davis, Lyon F. Terry

The rapid expansion of the natural gas industry in this country during the past three or four years has necessitated the construction of a number of long and comparatively large diameter high-pressure pipe lines This period of expansion and construction is still at high tide, and the current year will doubtless surpass all prior years in mileage and capacity of gas line installation. The fundamental economics of the business of long-distsrier transportation of natural gas may be briefly and simply stated, although most careful consideration must be given the actual determination and integration of the several more important factors which determine the ultimate success or failure of such a project. Reduced to its simplest form, a sound natural gas transportation project requires: 1. A competent source of gas, where the combination of quantity of gas available, cost of production, and longevity meet the given requirements. 2. A market, reasonably certain to endure in the face of any probable competition, of satisfactory size and price, and having a sufficiently favorable load factor. 3. A cost of installation of pipe line systen and an operating cost such as will, with honest and reasonably efficient management, afford a net operating return sufficient to attract the necessary capital required. In a11 new projects of this kind it is necessary that thehe three cssentials to ultimate success be assured. Hence the necessity of competent surveys of gas supply, and of market, both industrial and domestic. The prudent engineer will allow for "factors of safety" in reaching his conclusions just as he would in the design of a bridge. This paper deals primarily with but one of the major considerations enumerated above, I. e, the economic design of the pipe line system. The "pipe line system" will be considered to include (1) the pipe Iine, and (2) a series of compressor plants along the pipe line for maintaining

Jan 1, 1929

By G. H. Matheson, J. M. W. Mackenzie

The coal concentrates studied contained clay slimes which would not flocculate on the addition of a polymer flocculent alone. The mechanism of the flocculation process is interpreted on the basis of the flocculation of lyophobic colloids. The filtration rate characteristics are shown to deviate slightly from certain basic filtration equations. Cake moisture was shown to decrease with cake drying time and vacuum, and increase with cake thickness. Filtration is a commonly accepted method of dewa-tering the fine coal concentrates produced in coal cleaning operations. Dewatering of these concentrates, using drum or disc vacuum filters, usually presents few technical difficulties and will result in the production of a filter cake containing some 20 to 25 pct moisture. In many coal cleaning operations it is common practice to add flocculants to the coal concentrates prior to filtration to increase the filtration rate. The mechanism whereby flocculation increases filtration rate has been summarized by Gaudin,4 while Geer, et a15 have compared the effectiveness of starch and synthetic flocculants as filter aids for a variety of coal concentrates. Coal concentrates, containing appreciable quantities of expanding lattice clays of the montmorillonite-illite group, sometimes prove impossible to filter without flocculation of the pulp prior to filtration. The fine coal concentrates produced at the Newcastle washery of The Broken Hill Proprietary Co. Ltd. fall into this group. Coals mined in this district contain appreciable quantities of expanding lattice clays which break down in the washery circuit waters and, by processes of mechanical inclusion, contaminate the coal concentrate thickener feed. Despite the classifying action of this thickener, the underflow which is pumped to the filters contains sufficient clay slimes to render filtration of the unflocculated pulp impossible. Filtration leaf and plant tests were carried out to develop effective and economic flocculant combinations and to determine the filtration characteristics of the flocculated coal concentrates. The determination, by leaf testing, of the filtration characteristics, and the analysis of these characteristics in the light of the equations of Brown2 resulted in the successful trial operation of the filters in the Newcastle washq. Although the filtration characteristics are not entirely in agreement with the theoretical treatment of Brown, the equations developed made it possible to predict, from leaf tests, the effect in the plant filters of pulp density, form vacuum, and form time on filtration rate and filtrate volume. EXPERIMENTAL PROCEDURES The sample used for leaf testing was the coal concentrate thickener underflow, which in plant operations would form the feed to the two 12-disk Dorr-Oliver filters. The feed to the coal concentrate thickener comprises the undersize produced by dewatering the Diester table concentrate on 5-mm dewatering screens and the overflow produced by cycloning of the froth flotation concentrate. At the time of testing these filters were inoperative because of the difficulties in filtration, arising from contamination of the

Jan 1, 1962