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HAVING shown you before how moulds of statues and also those of guns are constructed, I wish to tell you at present how, if you wish to cast them in bronze, you are further to prepare and arrange these moulds so that they may receive the melted mass of the metals in a friendly manner and without disturbance. I know that you understand that a real and intense heat has been intro-

Jan 1, 1942

By D. H. Newland

New York has a small but not insignificant place in the oil and natural gas industries of the United States. It has had a continuous record as an oil producer since 1872, with an aggregate yield of about 104,000,000 bbl. The reported output for 1935 was 4,237,000 bbl., a gain of more than 10 per cent for the year and a total that has been exceeded only in the early period of flush production half a century ago. The industry has been steadily building up since 1920 with the successful practice of the water drive, which has given a new lease of life to pools that had been practically drained of oil recoverable by pumping. An additional output of 2000 bbl. or more per acre is being procured by this method. Altogether the fields in New York State cover about 55,000 acres. Their limits are well defined and it is unlikely that they will be extended in the future, although there is some prospect of finding additional supplies by deeper drilling. The oil from New York is all classed as Pennsylvania grade, for which the recent price has been about $2.50 a barrel. It is refined at Olean, Wellsville and Bolivar, in the oil district, and partly in Pennsylvania refineries. Exploration for natural gas, outside of the established districts, was considerable during the year. Altogether 59 wells were drilled, distributed over 13 counties, of which 33 were listed as producers and 26 were dry. At the close of the year, 13 wells were in process of drilling. The 33 producing wells had a combined estimated flow of 278 million cubic feet per day. The best results were obtained from exploration in Allegany County, where out of eight wells drilled to the Oriskany sandstone five were successful and showed a combined open-flow capacity of 107 million cubic feet. The Oriskany sandstone was encountered at a depth of 4500 to 4900 ft. In Steuben County, next east of Allegany County, two out of seven wells to the Oriskany proved productive, and one of these, in the town of Greenwood, on the Watkins structure, was probably the largest that has so far been opened in the state, with a reported yield of 35 million a day. In the central part of New York interest was awakened by the activity shown in exploring for gas in the Trenton limestone, in Camden, Florence and Rome townships, Oneida

Jan 1, 1936

By D. H. Newland

New York has a small but not insignificant place in the oil and natural gas industries of the United States. It has had a continuous record as an oil producer since 1872, with an aggregate yield of about 104,000,000 bbl. The reported output for 1935 was 4,237,000 bbl., a gain of more than 10 per cent for the year and a total that has been exceeded only in the early period of flush production half a century ago. The industry has been steadily building up since 1920 with the successful practice of the water drive, which has given a new lease of life to pools that had been practically drained of oil recoverable by pumping. An additional output of 2000 bbl. or more per acre is being procured by this method. Altogether the fields in New York State cover about 55,000 acres. Their limits are well defined and it is unlikely that they will be extended in the future, although there is some prospect of finding additional supplies by deeper drilling. The oil from New York is all classed as Pennsylvania grade, for which the recent price has been about $2.50 a barrel. It is refined at Olean, Wellsville and Bolivar, in the oil district, and partly in Pennsylvania refineries. Exploration for natural gas, outside of the established districts, was considerable during the year. Altogether 59 wells were drilled, distributed over 13 counties, of which 33 were listed as producers and 26 were dry. At the close of the year, 13 wells were in process of drilling. The 33 producing wells had a combined estimated flow of 278 million cubic feet per day. The best results were obtained from exploration in Allegany County, where out of eight wells drilled to the Oriskany sandstone five were successful and showed a combined open-flow capacity of 107 million cubic feet. The Oriskany sandstone was encountered at a depth of 4500 to 4900 ft. In Steuben County, next east of Allegany County, two out of seven wells to the Oriskany proved productive, and one of these, in the town of Greenwood, on the Watkins structure, was probably the largest that has so far been opened in the state, with a reported yield of 35 million a day. In the central part of New York interest was awakened by the activity shown in exploring for gas in the Trenton limestone, in Camden, Florence and Rome townships, Oneida

Jan 1, 1936

By Joseph L. Jernegan

THE Whale Lode occurs in the main range of the Rocky Mountains, Park County, Colorado Territory, at Hall Valley. It has been opened up and worked to some extent by the Whale Mine, situated some 11,300 feet above the level of the sea. The mine, with 700 feet of the lode on either side of the discovery shaft, is the property of the Hall Valley Silver-Lead Mining and Smelting Company. The adjacent country rock is a compact, fine-grained gneiss ; its general strike is about north and south, dipping steeply to the west. In the immediate vicinity of the mine, the strata are very nearly vertical. The gneiss incloses numberless veins of a reddish granite, in which the feldspar largely predominates over the quartz and mica, the latter oftentimes being scarcely perceptible. As a general rule these granitic veins seem to more frequently follow the lines of stratification of the gneiss than otherwise. They are of varying width, some large, some small; the larger are from 5 to 6 feet wide. Gash veins of feldspar and quartz are also of very fre¬quent occurrence. The general trend of the lode is about northeast and southwest, intersecting the country rock at about an angle of 45° to its stratification. It dips to the northwest at an angle of 65°. I am unable to state accurately how far this lode has been traced upon the surface, but it is at least well known to extend entirely through the mountain upon which the mine is situated, and is traceable over the ridge by a hollow extending for some distance along the surface, in which the lode crops out. This hollow in the surface rock has probably been formed through decomposition of the vein matter by atmospherical influences. The width of the crevice is variable, generally between 5 and 10 feet; the pay vein varies from an inch, or less, to 36 inches. The vein is generally accompanied both on foot and hanging walls by a whitish, semi-decomposed rock, composed of quartz and decomposed feldspar, and in some places-where the process of decomposition has not reached as advanced a stage-a light-greenish or black mica. This rock, therefore, is in places composed of all the constituents of gneiss, and is undoubtedly nothing more or less than the same in a decomposed condition. It is often very strongly impregnated with iron pyrites, generally crystallized in minute cubes, and it is probably owing to the presence of this min-

Jan 1, 1875

All data about shipments from the present state of West Virginia, even when it was still a part of the "Old Dominion," are shown in Table 56 together with the source of information, and all other figures are estimated. While the earliest production was undoubtedly in the extreme northern part of the state, coal having been quite largely used in Pennsylvania before any is credited to West Virginia, the largest production in the early days of the industry was along the Kanawha River where the salt furnaces used tremendous quantities for years before shipments were made by river. When we take into consideration the economic conditions existing then, it is evident that the consumption of coal by the salt industry along the Kanawha and Kiskiminitas Rivers rivalled in importance that of any industry today. There were no canals built in this state, the shipments before railroads were built being by the Ohio and Kanawha Rivers, and production in the northern counties began after the Baltimore & Ohio Railroad was completed from Cumberland to Wheeling. For some years after this line was completed all locomotive fuel used on it was hauled from the Cumberland region. The movement of coal from Boone County by Coal River to the Kanawha and Ohio Rivers from 1857 to 1880 is rather unique in its size and the length of movement, nearly all the coal going at least as far as Cincinnati and much of it to New Orleans. Fayette County began shipping when the Chesapeake & Ohio Railroad was completed and Mercer County, when the Norfolk & Western Railroad reached there in 1884; none of the other large producing counties in the southern part of the state began producing coal in the period under study.

Jan 1, 1942

By W. W. Scott

The application of engineering methods to the problems connected with drilling and producing in the oil industry has led to the development of the science that is variously termed "petroleum engineering," "production engineering," "petroleum production engineering," and even Itpolitical engineering." It would require much detail to enumerate the qualifications of a petroleum engineer, just as it would for an engineer in any major industry. For those who have a genuine liking for the oil industry, there is a wide selection of pathways to achievement. The oil industry is now highly specialized. Its products are necessary to all civilized people and are indispensable in the security of our nation and also in the well-being of our families. The business structure of our country depends in a large measure upon oil, and the welfare of this group as individuals is certainly linked with the welfare of the oil industry. What Is the Trend of Engineering? The oil industry offers a fertile field of opportunity for engineering; probably more so than any other industry. The sciences of geology, physics, chemistry and mathematics are all used in some phase of the oil industry and to a very considerable extent in the production division, which embraces the geological, drilling and producing departments. In drilling and production alone, research programs of considerable magnitude are being carried on at this time, and no doubt the future will see a great deal more of this kind of work. Through the cooperation of the engineer, the equipment manufacturer, and the American Petroleum Institute, immense savings have been made by the standardization of drilling and production equipment. Drilling equipment in itself offers a wide scope for study, in that continued efforts are being made to improve the equipment so that it can be made to drill faster and to greater depths. The improvements in drilling equipment are required because new reserves of oil are being found at progressively greater depths. In order to produce such oil in competition with oil now being produced from reservoirs

Jan 1, 1937

Jan 1, 1956

By Vytas Svalbonas

Sophisticated computer analysis methods such as finite elements, finite differences, and numerical integration have become tools in the mineral processing industry for design of large mill shells. While use of such methods allows the analyst-designer to take new freedom with his designed structure, there are also pitfalls and dangers which must be recognized for the proper use of such sophisticated tools. One of the worst of these is treating any computer answers as "gospel truth." The present paper discusses the knowledge required by the analyst-designer for proper use of computer analysis, as well as explaining to the layman how to identify questionable areas in such structural analyses.

Jan 1, 1980

By John Branner

FIVE of the geologic horizons that yield oil in other parts of the world are represented in Brazil; namely, the Devonian, Carboniferous, Permian, Cretaceous, and Tertiary. Thus far, the first two have shown no, evidences of being oil bearing within Brazilian territory. Not enough exploring has been done to permit trustworthy comparisons of the relative importance of the Permian, Cretaceous, and Tertiary as oil-bearing horizons in this country. The most important, indeed almost the only, information available relates to the locations of the areas and to the structural features of the several horizons. The theories regarding the physical conditions under which these rocks were laid down, however, I regard of the utmost importance. PERMIAN Rocks of Permian age cover an enormous area in Brazil, extending from Rio Grande do Sul to Maranhão on the north, and to Matto Grosso on the west. These Permian rocks in many places are known to include oil-bearing shales and in some locations contain small veins of gilsonite. The geologic map of Brazil shows that the Permian area is widely distributed, but there is considerable doubt about 'the origin of some of the rocks:. Some of the lower Permian beds in southern Brazil contain marine fossils, but in Minas no fossils have as yet been found in them, and in Bahia, at only one locality have a few Permian plants been found. Indications of oil have been found in the states of São-Paulo, Paraná, and elsewhere farther south, but wells drilled in the Permian of São Paulo near the Morro do Bofete did not find oil. One well has been started, by the Brazilian government, in the Permian of Paraná near Marechal Mallet, close to latitude 26° south, but thus far oil has not been found.

Jan 6, 1922

EVERY dry thing that burns easily and multiplies or maintains fire by its own intrinsic nature can be put into an incendiary composition and various effects are produced. Some of these things are mineral combinations, like sulphur or its oil; some others, [163v] hot, dry, and subtle substances, like saltpeter; and some are. unctuous things, like fats and oils of any kind; while some serve because of dryness, like pith and wood. Some of these things are natural and some artificial But now I set aside the search for these differences in their composition. This is what I have found among all the ancient and modern things that I have been able to seek, and first, back in the time of Alexander the Great. Marcus Graecus, who was perhaps the inventor or a great experimenter and practicer of such things, writes of many of them. I have chosen some among these, and one* is this: In order to make it, he took Grecian pitch, alchitran, live sulphur, tartar, sarcocolla, niter, and petroleum oil, one part of each, and, in addition, a double amount of quicklime. He mixed it all with oil of egg yolks. Having put it in a well-covered and closed vessel of glass or glazed earthenware under warm manure, he left it for a month. Then, having liquefied it over a slow fire, always keeping the vessel well closed, he finally put this liquor in hollow sticks, in little pots, or in vessels expressly made, all with a little fuse fitted in the middle. If I should have to do this, I would say that a little gunpowder should be put in, which should give beginning to the fire so that it would ignite more easily. I have also found that another fire is made. For this sulphur is taken, or oil of sulphur if it is possible to obtain, petroleum oil or some rock oil, juniper oil, very well-refined saltpeter, and for one part of each of these five parts of asphalt; in addition, take goose or duck fat, pure black pitch, varnish, pulverized dove's dung, and enough aqua vitae to cover all the aforesaid things.. Then it is put in a glass vessel under warm manure for

Jan 1, 1942

THE Institute assembled in the Court-House, on Tuesday evening, May 22d, and was called to order by Vice-President E. B. Coxe. After announcement by the Local Committee of the programme for excursions, the Secretary read the following annual report of the Council The Council, in presenting to the Institute its annual report, has to record a most eventful year in the history of the Institute. Three meetings, as usual, have been held, two in Philadelphia and one in New York. At the Philadelphia meetings in June and October, there were present many distinguished foreign engineers, some of whom contributed communications to the Institute, and took part in its discussions. Sixty-seven papers have, in all, been presented to the Institute, which will be published in the fifth volume of Transactions. There has been an accession to the membership of 1 honorary member, 11 foreign members, and 162 members and associates; -8 have resigned, 6 have died, and 30 have been dropped from the roll, after due notification, for non-payment of dues. The membership now comprises 5 honorary members, 60 foreign members, and 644 members and associates, in all 699. As worthy of especial mention in the work of the year are the Discussions on Technical Education in connection with the American Society of Civil Engineers, and the report of the-International Committee appointed by the Institute to consider the nomenclature of iron and steel. The Discussions on Technical Education have been published in a separate volume, and comprise a valuable and suggestive collection of the views of practical engineers and educators. The report of the International Committee, composed of Messrs. Akerman, of Sweden; Bell, of England; Tunner, of Austria; Gruner, of France; Wedding, of Prussia; and Holley and Egleston, of the United States, has received the careful attention of engineers and metallurgists of all countries, and has met . with very general acceptance. Of the work of the Centennial Committee in Philadelphia the members are generally familiar, from personal experience, and from the detailed report of the committee at the last meeting of the Institute. But the record of the service rendered by this committee would he incomplete without mention of the numerous letters of thanks and formal expressions of obligations received by the Institute from individuals, societies, and governments abroad. The wise and generous spirit in which the work of the committee was planned, and the laborious and self-sacrificing manner in which it was carried out, call for emphatic expressions of thanks from the Institute. The gifts of Centennial exhibits to the Institute, largely as testimonials for services rendered, has necessitated the appointment of a Museum Committee for

Jan 1, 1878

By R. Webeler

In order to study the role of work hardening in the fatigue process, use was made of the great sensitivty of the resistivity of AuCu to cold work. A change of the resistivity of AuCu of the order of 1 to 2 pct at the temperature of liquid nitrogen was found to occur as a consequence of severe fatigue. ACCORDING to Orowan's theory,' the process of fatigue In metals 1s associated with the production of a number of small regions which have undergone strain hardening. This phenomenon is supposed to occilr even if the stress applied during fatiguing is always smaller than the yield stress. In an attempt to verity the existence of such regions, Welber and Webeler' undertook to detect the stored energy associated with severe fatigue in copper. Previous experiments" had shown that the energy stored in a sample of copper which has been cold worked by torsion is released in the temperature range between 150" and 250°C when the sample is heated from room temperature and that no more energy is released (or absorbed) between 250" and 450°C. In particular the stored energy amounted to 0.41 cal per g for a case in which the mechanical energy expended in twisting the sample was 11.9 cal per g. In the case of fatigued copper, however, no release of stored energy could be detected between 150" and 250°C, so that the experimental error of &0.02 cal per g represents an upper limit for the amount of energy stored in strain hardening., It seemed desirable to attack the problem in a new fashion. For this purpose, it was decided to make use of the fact that, if an alloy capable of undergoing the order-disorder transition is ordered and then cold worked, the resistivity, p, increases very greatly above the value for the ordered state even if the deformation is very small. Some insight into the nature of the fatigue process may be obtained then by measuring the resistivity of an ordered sample before and after subjecting it to fatigue. For reasons which will become apparent from the following remarks, considerably more can be learned by carrying out the resistivity measurements at two different temperatures. In the case of a material containing impurities, vacancies, dislocations, or other imperfections of essentially atomic dimensions, the resistivity, p, according to Matthiessen's rule, can be represented as a sum of two terms p = p, + p, where p, is the (temperature dependent) resistivity of the pure metal, and p, is the temperature independent contribution of the imperfections. Briefly, the physical basis for this rule is the following: The main contribution of the impurities in question to the resistivity results from the fact that they interrupt the periodicity of the lattice and thus scatter the conduction electrons with a probability which is almost independent of temperature. In order that this be the case, it is necessary that the' extension of the impurities be small enough—roughly less than one electron mean free path—so that their main effect on the resistivity occurs for the foregoing reason. If an alloy like AuCu is partly or completely disordered by quenching from an appropriate temperature, Matthiessen's rule also applies to a very good approximation* with p, representing in this case the resistivity po of the ordered sample and p, the additional (temperature independent) resistivity due to the disorder. In general, the disorder can be represented in terms of atoms which are displaced from their "proper" positions in the superlattice and which thus qualitatively represent the imperfections in the superlattice responsible for the term p,. Since the misplaced atoms are distributed at random throughout the super-lattice, their contribution to the resistivity still can be considered in terms of the scattering of conduction electrons by lattice defects. The situation is somewhat more complex in the case of an alloy disordered by cold work because the process of disordering here does not involve a random redistribution of the atoms; however, Matthiessen's rule also holds in this case. Whenever Matthiessen's rule does apply, the values of the quantity /3 = (p? — /(T, — T,), where p, and p, are the values of the resistivity at two fixed temperatures, T, and T,, respectively, is constant (independent of p,) for a given alloy or metal. In particular, if a sample of AuCu is subjected to ordinary cold work, the value of /3 remains equal to Po, the value for the ordered material. According to Orowan's theory,' as remarked before, a fatigued sample contains a large number of isolated severely cold-worked regions, which make up only a small proportion of the metal. Thus, if a sample of AuCu initially in the ordered state is fatigued, more or less disordered regions will be produced within the ordered material. If these regions are small enough so that Matthiessen's rule applies, then it follows from the previous discussion that /3 again will remain equal to Po. If the effect of fatigue is to produce cold-worked regions which are macroscopic—of the order of at least several electron mean free paths—the effective resistivity, p, has to be computed by use of the ordinary laws of large-scale electrodynamics. For the sake of simplicity, it will be assumed here that the cold-worked regions are completely disordered and have a resistivity, p,. For a given proportion A of disordered regions the effective resistivity, p, for the current in a given direction depends on the geometrical configuration of these regions. In any case, the value of p for such

Jan 1, 1956

By H. D. Kiddle

IN mining in Malaya has been a courageous ad- venture in private enterprise, attended by all the hazards of prospecting in unexplored areas of tropical jungles-jungles that still cover four-fifths of the country. To assess the contribution of an industry to a country's revenue, it is necessary to consider not only duties levied on the products, but also the revenue from all businesses and individuals directly and indirectly deriving income from the industry. Exact figures are not obtainable, but from 1850 until shortly before the first World War, tin mining in Malaya was a dominant factor in the Federation's development. Even at the turn of the century, tin export duty alone represented 45 pct of total Government revenue, while in the 40-year period up to the end of 1937, tin ore duties collected by the Federated Malay States Government amounted to 383,- 81 0,284 Malayan dollars,* approximately one-fifth of the total revenue for the same period.

Jan 11, 1957

By Henry N. McCarl, John J. Dran

In recent years, market rates of interest have risen well above their historical long-term average. Also during this period, the short-term variability of interest rates has been greater than in prior years. Interest rates have a significant effect on the operation of our economy. They influence the extractive industries in a number of ways. Their major long-range impact is on in- vestment decisions-specifically the valuation of mineral deposits. An understanding of the factors that influence interest rates is important to the engineer or businessman who makes the investment decisions for the mining company. The effect of changes in the market rate of interest on the value of mineral reserves is critical to the future financial success of the mining enterprise.

Jan 6, 1977

By F. W. Libbey

Jan 1, 1985

By Hon. Charles McCrea

MINING taxation is a subject which bears definitely upon-the welfare of the mining indus-try. Every government must have a revenue but that revenue should be raised in such a way as to hamper as little as possible legitimate enterprise or industry. A mining tax should be fair, and one which appeals to the natural sense of justice. Our present system is a tax on net- profits after all expenses are met. On profits in excess of $10,000 the Mining Tax Act takes three per cent., one-half of which goes to the Govern-ment and one-half to the municipality in which the mines are situated, to meet local needs for roads, schools, etc. On profits from one to five million dollars", the tax is five per cent.; over five million, six per cent., and so on. The first $10,000 profit is exempt. The result is that if a mine is worked at a loss, it pays no tax at all; if it makes a small profit, it pays a small tax; if profits are large, the tax increases accordingly. It is difficult to imagine a fairer or less onerous method of taxation, or one better adapted to meet fluctuating conditions from year to year as profits rise or fall. A just and fair tax should be levied on profits, never on capital. There is, one branch of the mining industry upon which is levied a higher tax than upon other branches, namely, the nickel industry. I see no good reason why any branch of the mining industry should be discrim-inated against on a profits tax basis. A mining tax should not discourage development. The present tax meets this requirement. In the early years of a mine, when it is all outgo and no income, the mine pays no tax. Not until it reaches a productive and. profitable stage does the tax take effect, and then the mine can afford to pay it. Further, a tax on profits does not operate against the opening up of low-grade deposits, or those in which the chance of success is to a certain extent speculative.

Jan 10, 1923

By O. E. Kiessling

THE Committee-on Production Control, at its meeting held during the last annual session in February, 1930, evidenced great interest in problems of stabilization affecting all mineral industries. . No immediate program of activity for the Committee as a- unit was decided on, however,, and efforts during the past pear have consisted lirgely of further stressing the economic aspects of mineral production and of the action by committee members, :.serving in their individual capacities, in sponsoring constructive changes, in specific, industries. Of greatest interest to the general subject of production control in 1930 was the very definite advance toward better coordination of demand and supply in the petroleum industry. Furthermore, since opinion both within and without the oil industry now favors a constructive program, and with a gradual change in legal precedents, it seems not unreasonable to expect greater progress in the near future.

Jan 1, 1931

By J. E. Norton

PRODUCTION statistics show that during the period of emergence from the depres¬sion the coal industry was becoming increasingly cognizant of the economic and competitive necessity for mechanizing. About 1935 many of its leaders were becoming aware also of the alarming scarcity of men properly trained to cope with the new problems of mechanization. In order to get a factual statement of this problem, a special AIME Coal Division Committee + was requested to survey the condition. Its investigation disclosed that graduates of mining schools going into coal mining numbered 16 in 1939 and 15 in 1938. With this as a background, Pittsburgh Coal Co. foresaw that a comprehensive program was necessary if it was to enlist the services of trained technical men, who were an indispensable part of a mechaniza¬tion program. The purpose of this paper is to review the program set up, to comment on the successes and failures and to outline the future course of action. SUMMER WORK An inescapable conclusion from the mechanization statistics was that the opportunities in coal mining were good. Not only was there a void in technical skill to fill from past years, but the ac¬celerating rate of mechanization indicated an increasing demand for technically trained men for the future. The remedy lay primarily in presenting facts con¬cerning the coal industry to the under¬graduate engineers before they made their professional occupational choice. Based on this idea, one of the key points in the program - was summer vacation work for the undergraduate, which, through the inducement of summer earnings, brought men into the mines to take a look at the prospects. This was more successful than statistics indicate because the war badly scrambled the orderly working of the program, but it could not obscure the value of a summer work program. A decided advantage was that it gave the company a preview of the graduate. An observation on this part of the program is that it is extremely hard to gauge lower classmen, and we found it wise to give them the benefit of the doubt, as the last two years in college bring about surprisingly rapid develop¬ment in some men. We could readily single out the men at the opposite ends of the scale of competence. COMPREHENSIVE TRAINING PROGRAM Having adopted summer work as a

Jan 1, 1946

By Richard S. McCaffery, Joseph F. Oesterle, Oscar O. Fritsche

The method of obtaining the data on which this paper is based is explained in detail in the paper on Determination of Viscosity of Iron Blast-furnace Slags.' The work was made possible by a grant of funds from Engineering Foundation, and it gives the results now obtained, continuing the general subject of our previous work and reported in former papers2 The data experimentally obtained are in the form of a temperature-viscosity curve for any slag of particular composition. (See Fig. 1.) From these curves, the viscosity of a slag of a definite composition and at a definite temperature is taken off and is plotted on a plane triaxial diagram showing compositions of silica lime and alumina on a plane representing constant-magnesia content (Fig. 4). The temperatures at which these results were plotted are 1300°, 1350°, 1400°, 1450°, 1500°, 1550" and 1600" C. and since the constant magnesia plane sections were an even 1 per cent. magnesia apart, magnesia analyses not of even unit magnesia composition were projected to these even unit magnesia planes. For example, 1.78 per cent. magnesia and 2.35 per cent. magnesia were projected to the 2 per cent. magnesia plane. The triaxial diagrams on which this first plotting was made were drawn on celluloid sheets, a transparent material on which it was easy to draw. When all the experimental work was plotted on celluloid in this way, the sheets representing a definite temperature were stacked in the proper order and were examined by transmitted light. Where

Jan 1, 1932

By E. W. Enqelmann

INCREASED metal consumption throughout the world in the past three years has brought greater activity in the concentrators and mills that treat the ores.' Comparatively low prices have made greater economies necessary, with a continuing search for more efficient flow sheets, equipment, processes, and reagents. Comminution GRINDING has long been too ex- pensive and even any small increment of saving has been eagerly sought. Although not recently new the use of rod mills to cover the gap between intermediate crushing and coarse grinding has made further headway. They eliminate dusting and the closed- circuit operation of fine crushers, either roll or Symons cone, and the rod-mill product is suitable for secondary mills which can be operated with smaller balls and iron liners instead of coarse balls and steel liners. The newer practice is radically different from the older application of rod mills where they at- tempted to use them instead of ball mills for fine grinders. For that purpose they were not well adapted, as they do not have sufficient grinding surface available per cubic foot of mill volume.

Jan 1, 1940