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By H. C. M. Gordon

IT is essential to the success of any mining op::ration that the roadways through which the material wrought and ocher materials and supplies are to be transported should be kept in such condition that this transportation cart be effected rapidly and without difficulty. The longer the roadway and the greater the tonnage to be taken over it, the more necessary it becomes chat the construction and maintenance of the road be such chat traffic delays can be reduced co a minimum. le is proposed co deal with the development and construction of roadways serving longwall operations and, since a recreating system of longwall is worked, as a rule, only where roadways driven in the solid coal can be readily maintained, the discussion will be confined co advancing longwall roads which are driven through areas from which the coal seam has been totally extracted. In order to construct a roadway through extracted ground in such a manner that it will remain in a state of reasonably good repair without undue maintenance, it is necessary chat everything possible be done to bring the overlying strata co a state of equilibrium as quickly as this can be effected, and the operations should be so planned that future workings will not disturb the equilibrium so set up more than can be avoided. Obviously, the readiest way to obtain a stable roadway is to develop it by tunnelling through a settled waste. However, this cannot always be done, as some of the roadways must be developed and constructed as the walls progress, but level or lateral cut-offs can be constructed in this manner. Main-slope roads can be developed in a similar manner after the coal has been extracted and a waste formed for at !east five hundred feet on either side of the line of the permanent roadway from temporary subsidiary roads developed for this purpose along one or other of the flanks of the waste to be formed. This interval must be obtained in order chat the lacer extraction of the seam will not set up movements in the waste immediately overlying or adjacent to the constructed roadway, thus upsetting the equilibrium of the strata and distorting the road.

Jan 1, 1940

By A. R. T. Denues

This investigation was made under a cooperative agreement between the United States Department of the Interior, Bureau of Mines, and the Pittsburgh Testing Laboratory. Funds were supplied by the Chile Exploration Co., whose executive offices are in New York City. The support, cooperation, and services of these agencies made the work possible and are acknowledged gratefully. The writer wishes to express his particular indebtedness to the staff of the Explosives Division of the Bureau of Mines for services and assistance, particularly Dr. Wilbert J. Huff, consulting explosives chemist, J. C. Holtz, J. E. Tiffany, and A. B. Coates; to F. O. Gardner, treasurer of the Pittsburgh Testing Laboratory; to G. B. Holderer, consulting engineer in connection with liquid-oxygen explosives for the Chile Exploration Co.; to the Enos Coal Mining Co. of Oakland City, Ind., particularly to G. H. Utterback of the staff of the mine for providing facilities that made field tests possible; and to full-time assistants J. W. Rothhaar and J. G. P. Weinheimer and to W. S. Hiller, part-time assistant, who were employed under the cooperative agreement.

Jan 1, 1940

By M. F. Trice

PYROPHYLLITE is a hydrous aluminum silicate (A12Si4010(OH)2)1 that occurs in both the foliated and the massive forms. The foliated variety resembles talc in that it has a greasy feel, a pearly luster, perfect basal cleavage, and usually is white, although in some deposits apple green, gray, brown, russet, and nearly black specimens may be found. The massive deposits of pyrophyllite yield pearl gray to light tan aggregates, some of which are so friable that they may be crushed with the hands into a fine gritty powder. Frequently specimens of the massive variety are studded with crystals of radial structure. The mineral has a specific gravity of about 2.7 and a hardness of 1 on Mobs' scale.1 The chemical composition of commercial pyrophyllite reflects the mineralogy of the deposits, which, according to Stuckey,2 contain pyro-phyllite and quartz, together with chloritoid, sericite, and a few other minerals of negligible importance. The latter, he says, "are noticed in but small quantities to the extent they might occur as accessory constitu-ents of an igneous rock or as products of regional metamorphism or weathering. . . . Quartz is abundant everywhere except in the very best grades of pyrophyllite." Analyses of specimens from several deposits are listed in Table 1, showing that the silica content varies from 57 to 73 percent and the alumina from 22 to 33 percent. Oxides of iron and the alkaline metals are collectively present, with one exception, to an extent of about 1 to 1.5 per cent.

Jan 1, 1940

By Arthur Brant

STEEPROCK LAKE (Figure 1) lies about two miles north of Atikokan, a village approximately one hundred and forty miles west of Fort William and one hundred miles east of Fort Frances on the Canadian National railway. The possible presence of hematite beneath the waters of Middle arm was inferred by early geological investigators (1890-1903) from the dense hematite float found on the southerly shores of this portion of the lake (1). A dip-needle survey of Middle arm, undertaken in the winter of 1930-31 by J. G. Cross, indicated two areas of high magnetic attraction which Mr. Cross thought might be due to magnetic iron oxides associated with possible hematite bodies. Bedrock could not be reached by the ineffectual hand-drilling so courageously attempted, and further work was abandoned. It was not until 1937 that Mr. Jos. Errington, of Toronto, convinced of the possibilities, determined to support Mr. Cross to the extent of several thousand feet of drilling. During the winter of 1937-38, holes Nos. 1, 3, 4, 5, and 13 were put down (see Figure 1). The first four of these holes demonstrated that the areas of magnetic attraction outlined by the dip-needle survey east of the Narrows and southwest of Elbow point were due to ash rock (2). As a result, Mr. Cross decided to investigate the bordering areas of low magnetic attraction and selected a location near the high ferruginous lime (3) point in the northeast of Middle arm. Dense, hard hematite beneath approximately 350 feet of water and clay was struck in the first hole, and, before the end of the winter's drilling, hematite had been encountered in holes Nos. 6 to 13 along a straight line 700 feet in length (see Figure 1). In the meantime, the Steerola ( 4) Exploration Company had been formed to continue development and already, in the spring of 1938, W. D. Neeland, the Company geologist, had come to the conclusion that the most probable location for possible hematite was at the ash-lime contact. Accordingly, during the summer, drilling was continued off-shore in holes Nos. 15, 25, and 27 (see Figure 2) toward possible hematite bodies inferred by Mr. Neeland.

Jan 1, 1940

By J. B. Mawdsley

A LITILE north of the geographic centre of the Province of Saskatchewan, 150 miles north of the city of Prince Albert, is a narrow green-stone and sedimentary belt of pronounced structural characteristics. This belt, generally known as the Sulphide Lake belt, is about two and a half miles wide. During the past three years prospecting has uncovered numerous gold-bearing showings occurring chiefly along the centre of the belt for a distance of at least nine miles. The number of these showings, the nature of some of them, and their relationship to strong structural features, make it altogether likely that intensive work will eventually locate ore-bodies that will be of economic importance. The discovery of gold in the fall of 1938 on the south shore of Mackay lake, about five miles northwest of the Sulphide Lake gold-bearing belt, indicates that there are neighbouring zones of interest. This paper, an attempt to outline the present status of the interesting mineralized belt, is based largely on the information gained on a five-day tour of this district, made in August, 1939, on behalf of the Department of Natural Resources of the Province of Saskatchewan. The Sulphide Lake belt is named after a small lake centrally located in it. This lake and others are just north and within short portage distances of some of the long bays along the north shore of Lac La-Ronge, an irregular, island-studded lake, about twenty miles in diameter, in relatively rocky Precambrian country, just north of the Palaeozoic contact. The fur-trading post and settlement of Lac La-Ronge is on the west shore of this lake and a road, now under construction, will shortly link this community with the city of Prince Albert. In the past, the most direct route was an indifferent canoe route, in part following Montreal lake and river; more recently, the aeroplane has made this section easily accessible.

Jan 1, 1940

By R. A. Cattell

A technologic group such as the Petroleum and Natural Gas Division of the Bureau f Mines, which conducts research on many of the complicated and frequently interrelated problems f extracting crude oil and natural gas from the ground, transporting them to market or to daces for subsequent treatment, and manufacturing products, should report progress from time to time. Engineers and others who apply the results obtained by this division are closely associated with its personnel, because many of the problems are attached cooperatively with groups in industry. Some of this cooperation is formal, as exemplified by work now in progress under cooperative agreements with the States of Oklahoma, Kansas, and others, but much of it is informal, prompted by the desire to be mutually helpful in the public interest. Furthermore, the published reports of the Bureau on subjects pertaining to petroleum and natural-gas technology come to the direct attention of a relatively large number of persons, whose interest in results and appreciation of the value of this type of work have caused them to be kept currently informed regarding available data.

Jan 1, 1940

By M. F. Trice

PYROPHYLLITE is a hydrous aluminum silicate (Al2Si4O10(OH)2)1 that occurs in both the foliated and the massive forms. The foliated variety resembles talc in that it has a greasy feel, a pearly luster, perfect basal cleavage, and usually is white, although in some deposits apple green, gray, brown, russet, and nearly black specimens may be found. The massive deposits of pyrophyllite yield pearl gray to light tan aggregates, some of which are so friable that they may be crushed with the hands into a fine gritty powder. Frequently specimens of the massive variety are studded with crystals of radial structure. The mineral has a specific gravity of about 2.7 and a hardness of 1 on Mohs' scale.1 The chemical composition of commercial pyrophyllite reflects the mineralogy of the deposits, which, according to Stuckey,2 contain pyro-phyllite and quartz, together with chloritoid, sericite, and a few other minerals of negligible importance. The latter, he says, "are noticed in but small quantities to the extent they might occur as accessory constitu-ents of an igneous rock or as products of regional metamorphism or weathering. . . . Quartz is abundant everywhere except in the very best grades of pyrophyllite." Analyses of specimens from several deposits are listed in Table 1, showing that the silica content varies from 57 to 73 per cent and the alumina from 22 to 33 per cent. Oxides of iron and the alkaline metals are collectively present, with one exception, to an extent of about 1 to 1.5 per cent.

Jan 1, 1940

By Alfred W. G. Wilson

THE ultimate purpose of the Chemical Manufacturer is to produce consumer products which can be sold to customers. Such production and sales can be continued only if the operations yield a profit to the manufacturer and if the products meet the requirements o the consumer--bath parties to the transaction must be satisfied. There are vast numbers of consumer products, made by chemical pro-cesses. The production of some of these ultimate products may involve the use of several intermediate chemicals, applications of few or many different processes, and the utilization, somewhere in the series of operations, of a variety of raw materials. On the other hand, some ultimate products have a very simple chemical history between raw materials and end products. There are no chemical products in use which are completely independent of the mineral industry. For many, the association is direct and obvious; for others, it may be indirect and even obscure. Analyses of the process and raw-material ancestry of a very large number of consumer products would suggest that many products are derived from Industrial Mineral products directly, that there are many in which the connection is indirect, and that there are only a few products with which industrial minerals are not in some way or other associated. The vast majority of the more important chemical products, and especially the basic chemicals from which other products are made, are directly dependent for their production upon Industrial Minerals or their derivatives. In the preceding part of this paper, for each raw material mentioned some references have been made to the leading chemical products based on this material. This, however, is only part of the story, because in most cases the consumer product can be made from any special raw material mentioned only by the use of other materials or chemicals made from them. The production of consumer chemicals is really possible only through an intricate interlocking of processes, materials, and apparatus.

Jan 1, 1940

By W. W. Adams

The year 1937 was signalized by increased employment in the metal-and nonmetal-mining 4 industry of the United States. Measured by the number of men working, there was a 17-percent gain in employment compared with 1936. In total number of man-hours worked at all mines, the gain was slightly over 18 percent. Hazards connected with mining resulted in more accidents to the workers than in 1936, but the increase in number of accidents caused only a slight rise in the accident rate because of the much larger increase in the number of man-hours worked. In fact, the fatality rate per million man-hours of exposure was lower in 1937 than in 1936, but the rate for nonfatal injuries increased slightly.

Jan 1, 1940

By R. A. Cattell

A technologic group such as the Petroleum and Natural Gas Division of the Bureau of Mines, which conducts research on many of the complicated and frequently interrelated problems of extracting crude oil and natural gas from the ground, transporting them to market or to places for subsequent treatment, and manufacturing products, should report progress from time to time. Engineers and others who apply the results obtained by this division are closely associated with its personnel, because may of the problems are attached cooperatively with groups in industry. Some of this cooperation is formal, as exemplified by work now in progress under cooperative agreements with the States of Oklahoma, Kansas, and others, but much of it is informal, prompted by the desire to be mutually helpful in the public interest. Furthermore, the published reports of the Bureau on subjects pertaining to petroleum and natural-gas technology come to the direct attention of a relatively large number of persons, whose interest in results and appreciation of the value of this type of work have caused them to be kept currently informed regarding available data.

Jan 1, 1940

By E. R. Maize

[In report of Investigations 3452,5/ baling with roof movement in the Crucible mine, reference was made do to the fact tart timber decay was being studied at the time of writing. This roper, written after completion of that study, describes s the work and summarizes the data obtained. When the study of roof movement as begun at Crucible two ideas were advanced on decay Of timber by some of the officials: (1) That timber decay vas unusually rapid in the Crucible mine, and (2) that timber coated with rock dust decayed more rapidly than those teat were not so coated. There yore no records by which these ideas could be tested, and it appeared wise to make a limited; investigation particularly of the effect of rock dusting on decay, as rock dusting is an important means of preventing coal-dust explosions.]

Jan 1, 1940

By William W. Adams

Accidents to men employed in the quarrying and related industries of the United States were more numerous, absolutely and relatively, in 1937 than in 1936. Fortunately, the entire increase was in the category of nonfatal injuries, as accidents causing death declined in number and in proportion to the number of man-hours worked. Employment increased. More men were employed, more man-days and man-hours were worked, and the average employee had more hours of work than in 1936. Reports covering all commercial operations showed that 84,094 men were employed an increase of 5.1 percent over 1936. The number of man-hours of work performed by the industry was, 158 millions, an increase of 7.6 percent. Seventy-seven men were killed by accidents, a, reduction of 14 from the year before, and 6,348 men were injured and disabled for more than the remainder of the day on which the accident occurred, 11 percent more than in 1936. The fatality rate of 0.49 per million man-hours of exposure in 1937 compared favorably with the rate of 0.62 for the previous year, whereas the non-fatal-injury rate of 40.10 was 3.2 percent higher than the rate of 38.87 for 1936.

Jan 1, 1940

By C. H. Jr. Herty

ALMOST every metallurgist who has given the Howe Memorial Lecture has had a personal contact with the distinguished gentleman to whose honor this hour is devoted. Unfortunately for me, such personal contacts were not possible. However, in the preparation of a thesis on the open-hearth process, one of my earliest tasks was to make a survey of the literature, and it was from Professor Howe's Metallurgy of Iron and Steel that I drew a number of references to previous work which formed the foundation for my reading. In his volume there is such a complete exposition of the then current thought on the subject of slags and on their role in the elimination of phosphorus from steel that I feel no hesitation in discussing in this Howe Lecture the subject of "Slag Control." In the present era of close specification, the drive for uniformity of product, and the close inspection of the product and of the cost sheet, the utmost efforts must be made to control the steelmaking variables to the best advantage of the steel producer. One of the major variables is the slag in the furnace and its effect upon the composition and quality of the metal. What advantages are to be gained from slag control? In the broad sense the advantages must be tremendous, because the very foundations of good steel melting are based on "shaping up" the slag to a point where, with proper temperature, the heat is ready for the final additions. Every melter works toward these ends through his experience with innumerable heats of steel. The elimination of undesirable constituents such as phosphorus and sulphur is entirely a matter of slag composition and physical nature, a point well known for over half a century. The role played by the slag in assisting in proper heat transfer from roof and flame to the steel has been equally well known. In more recent years there has come the problem of oxygen control in the more accurate gaug-ing of additions for making high-grade rimmed steel for the new strip mills, and in the deoxidizing additions for grain-size control and cleanli-ness of forging steels, both carbon and alloy. In this problem the oxidiz-ing characteristics of the slag are of prime importance.

Jan 1, 1940

In the plumbing of vertical shafts the methods employed and equipment used, are generally made to best suit existing conditions. Undoubtedly, there is no method that can be called standard or that can be used with equal ease and success on all shafts. At the Mount Isa Mines Limited property in Northern Queensland, Australia, local conditions have presented no major difficulties to be overcome in shaft plumbing work. In fact, compared to those at many shafts, the problem has been rather simple. There are three vertical shafts connecting main mine workings, with the greatest plumbing depth for any single lift, 350 ft.Other conditions pertaining to plumbing work have been generally normal.The method we have employed is, in principle, similar to the Weisbach orientation method with a variation that does not necessitate damping of the wires to bring them to rest. Although conditions encountered have not been such that damping the wires would have been inconvenient, we feel we have saved much time and eliminated unnecessary...

Jan 1, 1940

By Edmund S. Leaver

The Precious Metals Section is concerned primarily with ore-testing problems associated with precious metals and with the analysis and concentration of a large number of the strategic-mineral samples that have been included in the research program of the Bureau of Mines. During the fiscal year 1938-39, 30 projects were completed. The requests for this service are based upon the desire f the sponsor to obtain the best or most satisfactory method for maximum recovery of the minerals. In many instances it is a question of improving present milling practice, with due regard to utilization of present equipment. In others, the probable tonnage available maybe the deciding factor in the choice of a particular recovery method. Under all circumstances the results of tests axe prepared with the thought of aiding a competent metallurgist, familiar with local conditions, to formulate a practical flow sheet or to assist the mill operator to correct known losses. A microscopic examination for identification of the mineral constituents and their association in each ore is always a big help, in planning the tests and may indicate the reason for former troubles or assist with best procedure.

Jan 1, 1940

By Oliver Bowles

Calcareous rocks, of which the principal varieties are marble and lime¬stone, are used extensively for building and ornamental purposes. Onyx and travertine, subdivisions of these groups, are sufficiently distinctive in origin and use to merit separate classification. The purpose of this paper is to define the terms "onyx" and "travertine" and to describe the occurrences and uses of the materials bearing these names. ORIGIN AND CHARACTER Confusion exists in the use of the word "onyx." True onyx is a banded chalcedony, a form of silicon dioxide related to jasper, agate, and flint. Calcium carbonate is commonly deposited from solution in successive layers of varying color closely resembling onyx, and for this reason such calcareous rock is also called "onyx." To distinguish the calcareous from the siliceous

Jan 1, 1940

Page Laboratory Methods...........................127 Special Analytical Methods.......................127 Improvements in the Accuracy of the Vacuum-fusion Method for the Determination of Oxygen in Steel....................127 Quantitative Spectrochemical Analysis of Mixtures of Gases.......131 Oxygen Samples from Open-hearth Bath...............133 Rapid Analysis of Sample for Alumina.................139 Accurate Carbon Analyses in Low-carbon Steel.............139 Laboratory Technique for Study of Reactions Involving Liquid Metal. . . . 142 Rotating Liquid Crucibles......................143 Stationary Crucibles.........................145 Jones and Laughlin Experimental Furnace...............148 Vacuum Melting..........................149 Measurement of Temperature of Liquid Iron and Steel;..........149 Pouring and Teeming Temperatures..................149 Bath Temperatures.........................151 Plant Methods.............................154 Methods of Studying Slags.......................154 Sampling Slag in the Open Hearth..................155 Viscosity of Open-hearth Slags....................155 Petrographic Examination of Slag...................156 Statistical Methods Applied to Study and Control of Chemical Relations in Bath...............................166 Rapid Method of -Correlation Applicable to Study of Steelmaking Reactions............................166 INTRODUCTION On Thursday morning, Feb. 16, 1939, a round table discussion was held on the subject of Experimental Methods in the Study of Steelmaking. Dr. John Chipman, Professor of Metallurgy at the Massachusetts Institute of Technology, and chairman of the A.I.M.E. Committee on Physical Chemistry of Steelmaking, presided. In opening the meeting, the chairman said: "The purpose of this round table is to discuss methods of study by which more and better information on the fundamentals of steelmaking can be obtained. It was thought that a round table discussion rather than a symposium would furnish the best opportunity for those actually using various methods of study to get together and discuss their common problems. For this reason attention will be focused upon methods of study rather than upon their results. We want new and current and up-to-date discussion.

Jan 1, 1940

By Gilbert Soler

PRODUCERS of alloy steels recognize the importance of chemical composition in rela-tion to the hot-working properties and the typical surface defects found in their prod-uct. Each analysis of steel has its own peculiar characteristics. Under conditions of standard mill practice each analysis is susceptible to certain types of defects. Mill practice must be varied to obtain the best combination of surface and internal quality in the product. Chemical composition influences the cast structure and crystallization character-istics of the ingot. It also determines the rate of heating and cooling, the plastic hot-working range, and the phase structure of the steel at various temperatures as well as the tendency toward scale formation and decarburization, This paper endeavors to emphasize the manner in which chemical composition affects the various properties of steel, and to indicate the relative impor-tance of these factors in relation to the hot-working properties and surface charac-teristics of killed steel. The influence of chemical composition may be outlined as follows: I. Effect on the cast structure of steel, including: A. State of deoxidation, and type of inclusions. B. Gas content of steel. C. Freezing point and melting point of steel.

Jan 1, 1940

By Alden B. Greninger, Alexander R. Troiano

Metallurgists have long believed that martensite in steel forms as plates along the octahedral {111} planes of austenite. Much has been written about mechanisms whereby units of the austenite lattice are pictured as transforming to martensite by shearing movements initiated along the octahedral planes of austenite, supposedly resulting in plates of martensite lying parallel to these planes of shear. A critical inspection of two or three photomicrographs of quenched hypereutectoid steel led us to the conclusion that the orientation habit of martensite, at least in hypereutectoid austenite, could not possibly be octahedral. Inasmuch as recent studies,30,31 of the martensite-type reaction in nonferrous alloy systems have established the irrational orientation habit as characteristic of this type of lattice transformation, the need for a thorough restudy of the crystallography of martensite formation in steel was evident. The present paper reports the results of such a study, extended to include both cementite and some of the products of constant-temperature decomposition of austenite. Also reported are a few of the results obtained from a microscopic and X-ray study of the austempering process in very high-carbon steel. I. The Martensite Transformation Previous Work Microstructure and Crystal Structure of Martensite.—Among the best series of published photomicrographs of quenched steels are those of Whitely,1 Robertson,2 Hanemann and Schrader,3 and Lucas.4 The crystal structure of martensite is body-centered tetragonal, with axial ratio varying from 1 near 0.0 per cent carbon to 1.08 for 1.75 per cent

Jan 1, 1940

By Donald E. Cummings

Measures appropriate for the control of the silicosis hazard in mining cannot be formulated precisely, but sufficient knowledge1-l9 has accumulated during the past quarter century to permit the suggestion of useful, though partly empirical, rules for its alleviation. The industrial hygienist today recognizes that the peril incurred by the inhalation of harmful dust is a function of two variable factors—the degree of harmful exposure and the specific susceptibility of the exposed individual to pulmonary injury. Control of the danger arising out of prolonged contact with pernicious airborne particulate matter is consequently best exercised by influencing both of these recognized variables. Obviously the problem has two broad aspects—one, medical; the other within the province of the engineer. I—Factors Comprising Degree of Individual Susceptibility Thorough investigations conducted among miners who have labored for years in the presence of recognized silicosis hazards usually reveal an impressive difference in the injury incurred by men whose exposure to dust has been nearly identical. After a quarter century underground, one individual is short of breath and incapacitated with miners' complaint, while a fellow workman suffers no pulmonary embarrassment and is in good health. Physicians ascribe this oft-observed difference in reaction to individual susceptibility and express a universal regret when they deplore the fate that chose to make the predisposed youth a miner rather than a farmer. To trust the health of miners to fate at the present time is even more unfortunate, because many of the factors that influence man's susceptibility to dust are known, and can be accurately determined by competent medical methods. Among the most important factors comprising susceptibility to injury by dust are the anatomical peculiarities of the individual's respiratory mechanism, his physiological response to the inhalation of dust, his previous dust, exposure, the existence of pulmonary infections or other pathological processes in his lungs, his age,

Jan 1, 1940