Search Documents

By L. V. Bell

THE object in prospecting is to find ore. With the exception of certain discoveries of more or less accidental nature, intelligent prospecting as conducted today is, whether consciously or not, based upon a process of elimination. In the following discuss on it is proposed to evaluate those factors that enter into the eliminating of certain tracts of ground and, conyersely, the concentrating of attention upon others. The danger of generalizations as to the barrenness of cer.ain areas, without having due regard for all such factors, is emphasized. The fact that our conception as to what areas or rock formations are to be regarded as favourable or unfavourable is, in some measure at least, changing with new discoveries under diverse and unexpected circumstances, adds more point to the discussion. The criticism might be raised that the subject is treated largely from the standpoint of geology, but that may be met by stating that it is, and must continue to remain, precisely from this standpoint that the prospecror directs his activities. Briefly, the geologist may render the greatest service to the prospector in the early steps of selecting (a) the general territory in which to prospect; (b) the area to be intensively prospected; and, finally, (c) those parts of the claim or claims to be prospected in detail. Although certain phases of the discussion will be, in some measure, of general application, we shall here concern ourselves essentially with prospecting in the pre-Cambrian shield. Furthermore, the subject is so large that it has been decided to limit it to a consideration of that portion of the pre-Cambrian rocks in which is situated the mining district of western Quebec, of which the writer can speak with more personal knowledge. This limitation need not, however, seriously detract from whatever merit the discussion may possess, since the deposits concerned cover a fairly wide range of metallic ores, including gold, copper with associated zinc, and, lastly, molybdenum.

Jan 1, 1936

By W. C. Risley

IN the year 1933, workings at the No. 12 colliery, New Waterford, of the Dominion Coal Company, Limited, had advanced to a point where additional ventilation would soon be required. Furthermore, development of the mine was being .made to practically double the output of coal. Consequently, authorization was given to sink a shaft to the workings. The location selected is on the west side of the mine, about one and a half miles from the slope mouth and on the Low Point shore, some 250 feet from high-water mark. The cliff at this point is 40 feet high, with the land rising on a slope of about 5 per cent to the shaft. Figure 1 shows the location with reference to the colliery workings. The strata through which the shaft was to be sunk were pretty well known from diamond-drill borings previously made, and it was believed that water would be encountered to a depth of at least 250 feet to 300 feet. It was planned, therefore, to seal-off the water by the pumping of cement grout under high pressure. This method was considered to be the most economical means of handling the water during sinking, and would also result in a permanently dry shaft. Figure 2 shows a cross-section of the strata. The permanent shaft hoist and fan were to be electrically driven, which would necessitate the construction of a transmission line between the colliery and the shaft; therefore, it was arranged that the sinking equipment would have electric drive. As all equipment, materials used in construction, and supplies were to be hauled by truck, a roadway 1,800 feet long was required from the main highway to the site, and as heavy loads would be hauled during the fall, winter, and succeeding spring, this road was ballasted with 18 inches of clinkered material obtained from a burned culm bank one and a half miles distant. Actual field work was begun by the Company's own forces early in October. Work preparatory to sinking-in addition to the roadway and trans-mission line-included the construction of the reinforced-concrete shaft collar and fan drift connection; the permanent timber headframe (which was to be used also as the sinking headframe); the permanent reinforced-concrete building to house the shaft hoist and fan drive; and the erection of temporary buildings and installation of all equipment for sinking and lining the shaft and for cementation.

Jan 1, 1936

By Selwyn G. Blaylock

I.-THE HISTORY OF THE SYSTEM TO trace the history of the development of the Co-operative Committee System in The Consolidated Mining and Smelting Company of Canada, Limited, one must look backward about twenty years. In 1915 and 1916, the first years of the W ar to really affect Canadian life, there were sixteen hundred men working in the Trail plant. These men were, on the whole, a splendid body of men and pa trio tic to the core. They were almost one hundred percent organized, ninety-five percent of them be-longing to the Union of the Western Federation of Miners. Most of the tradesmen belonged to their craft unions as well. For example, there were ? local machinist, steel workers', electrician, boiler maker, bricklayer, and carpenter unions. The Company had always maintained an open-shop policy and refused to enforce membership in any union, but recognized the right of every man to belong to unions. The only exceptions have been the I.W.W. and the One Big Union. Both of these organizations have always been fought by the Company. By 1916, membership in the Western Federation being practically 100 per cent, the Company recognized this organization's authority to make agreements, and a wage and hour agreement was drawn up and signed by the Company and the local officials of the Union, and ratified and signed by the Head Office of the Union in Denver, Colorado. This agreement was for the duration of the war.

Jan 1, 1936

By M. A. Schellhardt

The Bureau of Mines has made periodic back-pressure tests on numerous gas wells in the Texas Panhandle field during the past several years to study the delivery capacities of the wells under different pressure and operating conditions and to determine the relationships between pressures and rates of delivery from gas wells.4/ However, information regarding the intake capacities of gas-well systems is meager, end in projects involving the flow of gas into porous-rock reservoirs it has been necessary to determine intake capacities of gas wells by trial. Accordingly the fundamental intake characteristics of natural-gas yells have been studied to develop a method for determining intake capacities under different wellhead pressures from data descriptive of the "output" or producing characteristic of the wells.

Jan 1, 1936

By I. B. Browning, N. Shiarella, Coleman D. Hunter

The price of crude oil in Kentucky did not change very much during 1935 until the latter part of the year, but more stabilized conditions and an increase in consumption of natural gas made the year a more profitable one than the year 1934. The production of crude oil in 1935 amounted to 5,175,054 bbl. as compared to 4,814,904 bbl. in 1934. This increase was due to two developments: (1) the application of new recovery methods to old fields, which, although in operation in the state for several years, had never before reached a point where the production obtained, while highly satisfactory where applied, was sufficient to influence the totals in the production figures; (2) the development of the Fordsville area in Ohio County, where shallow depths enabled the operators to complete the development of a large number of wells with a good flush production probably accounted for most of the increase. A map showing the location of oil and gas pools in Kentucky was published last year.' The fields of eastern Kentucky, producing from the Weir sand of the Waverly group of the Lower Mississippian series, in Johnson, Magoffin, Lawrence and Elliott counties, produced 826,001 bbl. of oil in 1935 as compared with 902,247 bbl. in the previous year. No new wells were drilled in this area during the year, except those for use as intake wells in repressuring. What has been done in the few small areas within these fields in the way of repressuring has produced results sufficient to a great extent to offset the natural decline of all the field. It is probable the drilling of new wells and construction of new plants will be such as to cause these fields to produce more in 1936 than was produced in the past year. This is based on the fact that the sand is highly favorable for repressuring and the results obtained show from 300 to 500 per cent increase in production. From the "Corniferous" pools, where production is from the Cornifer-ous limestone of Devonian age, in Lee, Powell, Estill, Wolfe, Morgan and

Jan 1, 1936

By Northcutt Ely

A year ago the petroleum code was in effect, and Congress had before it bills with powerful backing designed to extend and put on a permanent basis the Federal authority impliedly recognized in the petroleum code. Those men in the industry who were convinced of the unconstitutionality of Federal regulation, who believed in conservation, and who were seeking accomplishment of a conservation compact among the oil-producing states, were at that time encountering difficulties in bringing about such an agreement. Since then there has been a shift in the center of gravity. Today, by virtue of the Supreme Court's Schechter case decision, the petroleum code is not in existence, the industry is not operating under an oil administrator, and the Federal-control bills are not on Congress' calendar. In view of what the Supreme Court has said in the Schechter case and the Hoosac Mills case about the local character of mining and manufacturing, the problem today is not whether the Federal Government or the State Governments ought to regulate oil production, but how effective we can make the devices that are available to us under the constitution for the conservation of the nation's oil resources. The interstate oil conservation compact ratified during the past year by Texas, Oklahoma, Kansas, New Mexico, Colorado and Illinois, approved by Congress, but not yet in effect in California, is the mechanism now at work. Interstate Oil Conservation Compact What is this interstate compact? The basic theory is simple and logical. It has four elements to it. The first point is that in order to effect the maximum recovery of our oil arid gas reserves it is necessary for some governmental authority to regulate the way in which those resources are taken out of the ground, so that the reservoir energy is efficiently used, and used equitably by the various owners of the pool. Second, that the state, as distinguished from the national government, possesses the police power necessary to protect the public interest and to protect the correlative rights of the common owners of the oil pool. Third, that the state governments ought to cooperate with each other through an interstate advisory commission so that orderly production in one state is

Jan 1, 1936

By E. H. Tenney

A discussion of the probable future use of coal for power development involves the study of several basic factors, such as future demand for power, the quantity and availability of fuels in direct competition with coal, the price of coal, and a closely related factor—the efficiency and cost of fuel utilization. Predictions based on purely statistical analyses of past coal consumption have definite limitations. For example, statistics showing the relation between coal utilization and total energy consumption from all sources between the years 1890 to 1930 indicate that during that period the energy consumption per person in the United States increased five times, while the coal consumption per person increased only twice1, and there has been an actual decrease in per capita coal consumption since 1920. Figures such as these, compiled by authentic agencies, emphasize the need for caution in attempting estimates as to the future use of coal, and, incidentally, would seem to offer little basis for optimism in the coal industry. They also suggest the value of analyzing broadly the part played in the past by the related factors of power consumption, competitive fuels, coal prices and the efficiency of utilization. Proper weight must also be given in such a study to the present status and limitations of power-plant developments, arid to the question of what the coal industry itself can do to further its own interests arid influence the consumption of its product.

Jan 1, 1936

By Wallace Ralston

The East Texas area includes the northeast 38 counties of the state of Texas. It covers all, and extends beyond, the borders of what is commonly described as the East Texas Basin. It is one of the most important oil and gas-producing areas of the Mid-Continent Province. It includes four important oil fields—Van, East Texas, Cayuga and Long Lake— and the recent extension of Rodessa field into Cass County, Texas, may prove to be of major size. Four commercial gas fields are in this area— Bethany, Waskom, Cayuga and Long Lake. Up to January, 1936, all of the oil has been produced from the Upper Cretaceous formations, and most of that from the basal member, the Woodbine sand. Gas is produced from both the Upper and Lower Cretaceous formations. Development in Fields East Texas Field.—This field continued to dominate the drilling and production situation throughout the United States. There were 4036 wells completed in this field during 1935; that is, 365 more wells than were completed during 1934. Drilling activity was due to close spacing of wells and the addition of 10,000 acres to the field. The field is now drilled to a density of one well to 6½ acres, which is certainly more wells than necessary for economic production of the field. The close spacing of wells is due mostly to the type of proration, which is per well allowable based on a potential test, and does not take acreage into consideration, and also to the numerous small acreage tracts such as town lots and excess strips. The field now has 19,519 producing wells. The allowable production for the field during 1935 was 161,118,659 bbl.; estimated production, including illegal or "hot oil," was 174,200,150. The illegal production of oil gradually decreased throughout the year, until an estimated low was reached of 20,500 bbl. daily during the months of November and December. The price of oil remained at $1.00 per barrel throughout the year. As stated, about 10,000 acres were added to the field during the year, making a total of 128,000 productive acres. There is a possibility that

Jan 1, 1936

By Howard N. Eavenson

One who has been trained in belief in the law of supply and demand and its effect upon prices finds it difficult to adjust himself to the minute regulations imposed by the New Deal, and also to the bewildering changes of government policy as expressed within a short period of time between the antitrust laws and the N.R.A., and later by the Bituminous Coal Conservation Act of 1935. A survey of the coal industry since the World War, both in this country and Great Britain, however, shows that regulation of some sort is needed if any stabilization is to be achieved and if the wage structure and economic welfare of the many communities dependent solely upon coal are to be maintained. Let us look at what has happened to the industry since 1920, which can be considered as the end of the period affected by the war influence. This discussion will be confined solely to bituminous coal, although many of the general conditions are equally applicable to anthracite, the position of which now is at least as bad as that of the softer variety. Since 1920—to the end of 1934—the production of coal has decreased from 568.7 million to 358.4 million tons, or 37 per cent; the number of mines from 14,766 to 6,258, or 58 per cent; the average annual production per mine has changed from 38,512 to 57,425 tons, or 50 per cent. The number of large mines has increased considerably, and the number of men employed has decreased from 639,547 to 458,011, a reduction of 28 per cent, while the average output per employee has changed from 4.0 to 4.4 tons, or an increase of 10 per cent. The average price per ton of coal at the mine has varied from $3.75 to $1.75. During that time wages decreased largely until 1933 and since that time have increased, until now the rates paid are considerably above those in other occupations, although the actual yearly earnings are low, because of part-time work. From 1920 to the signing of the Jacksonville wage agreement in 1924, about two-thirds of the men were union members and practically all of the nonunion mines were south of the Ohio River; with the fixing of the high wage scale of that agreement, which soon proved to be an uneconomic one, many of the mines found that they could not retain their business, so gradually changed to nonunion. By 1928 the proportion

Jan 1, 1936

By G. W. H. Norman

INTEREST in the mineral possibilities (gold, copper) of northern Quebec, north of the Quebec-Cochrane branch of the Canadian National railway, has centred for many years in the Chibougamau district (see Figure 1). Since 1934, however, promising gold discoveries in the Rose Lake-Florence River section, 115 miles southwest of Chibougamau lake, have widened the interest, and prospectors have examined other parts of the country between Chibougamau lake and Bell river and the surrounding districts. The object of this paper is to !resent an outline of the geology, and to describe the mineral deposits, o part of this region, or, more specifically, of the part embraced by the Opawica-Chibougamau and Waswanipi map-areas(l), which include the districts about Chibougamau lake and Rose lake-Florence river, where mineral deposits are now in course of development either by surface or underground work. Early discoveries, developments, and explorations in the Chibougamau district are well summarized in the report of the Chibougamau Commission, published in 1911(2). The Commission discredited previous optimistic accounts of mineral discoveries in the area, made initially in 1903, but at the same time they expressed the opinion that, from a geological standpoint, the district promised a reward to diligent and intelligent prospecting. Their general conclusion-that prospecting in the area was not then (1911) commercially advisable in view of its inaccessibility and other handicaps shifted interest from the district until, some years later, valuable discoveries were made in the Rouyn area, and aircraft widened the field of successful exploration. During the past ten years or so, considerable energy has been spent in promoting the development of the district. The net result has been the discovery of a number of prospects, the majority of which have been explored only by trenching and, in most cases, diamond drilling.

Jan 1, 1936

By T. L. McCall

AUTHENTIC records show that coal mining in Cape Breton dates from the year 1720, when the French military authorities obtained coal from what is now known as the Blockhouse seam, in the Morien district, for use at Louisburg, where the fortress, now of such historic interest, was being built. Thereafter, coal was mined more or less continuously, and although, for many years, in a very haphazard way, there was, on the whole, a steady growth towards a better regulation of the industry, culminating in the year 1825 with the arrival of the General Mining Association in Nova Scotia. This Company, more generally known as the G.M.A., had acquired extensive tracts in Brazil and Colombia and had also purchased the mining rights for the whole of Nova Scotia-excepting such areas as had been previously leased-the attraction being the rich veins of copper currently reported as occurring in the Province. These fabulous copper veins, upon examination, failed to materialize, but the engineer sent out to report on them returned with such good accounts of the coalfields he had seen that steps were taken immediately to investigate them. From that rime onward, the history of coal mining in Nova Scotia is one of progress and achievement. One of the first acts of the G.M.A. was to acquire the areas already leased to other concerns and develop these in a masterly fashion, employing the best machinery and talent available at that time. Such dominant control over the minerals of the Province, although it led to orderly development in the several coalfields, also, later on, resulted in restricting operations in the various coal centres to such an extent that a determined effort was put forward by the people of Nova Scotia to end such a state of affairs. Consequently, in 1857, the original lease of the G.M.A. was abrogated, the Company, however, being allowed to retain certain areas in the districts it had already developed. This opened the way for the formation of other coal-mining companies, and numbers of these immediately sprang into existence in the various coal-mining centres. In 1893, the Dominion Coal Company, Limited, was formed by the amalgamation of seven companies operating in the neighbourhood of Glace Bay, in Cape Breton. Later, in 1910, the Dominion Iron & Steel Company, Limited, obtained control of the Cumberland Railway & Coal Company, which had been formed in 1884 to acquire the rights of the two companies working in the Cumberland County coalfield.

Jan 1, 1936

By Chester Fulton

IN Polk County, Florida, the mining of raw phosphates began some 50 years ago with dredging operations on the Peace River, and in other near-by places by removal of shallow overburden with negroes and wheelbarrows, or with mules and scrapers, and the excavation and screen-ing of deposits found close to the surface. There were many individual operations of comparatively short life. Later steam shovels removed the overburden, and still later hydraulic methods were substituted for the steam shovel. Within the last 10 years large electrically operated drag-lines have almost entirely replaced hydraulic mining for overburden removal. The matrix is still mined by hydraulic giants and pumped to the washer or recovery plant. The many small operations have long since disappeared and the most desirable phosphate lands have gradually been acquired through purchase or merger by the seven companies that are operating in the field today. These companies are producing and selling about 2,000,000 long tons of phosphate per annum, or about two-thirds of what the industry likes to think is the normal output, with 1929 and 1930 in mind. To produce these 2,000,000 long tons of raw phosphate, they mine and treat about 1,000,000 tons of tailings from older and less efficient opera-tions, about 11,000,000 tons of matrix, and remove from above this matrix some 22,000,000 tons of overburden. The mining practice that has made possible the excavation and handling of 34 million tons of material to win but 2 million tons of merchantable product, selling for probably an average of only $4 per long ton when dried, should be of interest to the mining profession, though little has been written of it. The Florida Pebble Field, as it has come to be known, comprises an area (Fig. 1) within a radius of about 18 to 20 miles centering around Mulberry in Polk County, a small town 30 miles east of Tampa, Florida's largest port on the gulf coast.

Jan 1, 1936

By R. S. Dean

The function of the Metallurgical Division is to conduct investigations relating to the treatment of mineral products from the state in which they are mined to the refined metal or other unfabricated product. These investigations include scientific and practical studies of ore dressing, covering the crushing and grinding of ores, separation by gravity, flotation, and magnetic methods; the hydrometallurgical treatment of ores, including cyanidation and amalgamation of the precious metals; the smelting and refining of copper, lead, and zinc, as well as the rare metals; and steel-melting practices from the raw ore to the finished steel. The object of this work is to conserve natural resources and eliminate waste by furnishing information on current methods of metallurgical practice, making fundamental studies of metallurgical processes, and developing new processes to the point of demonstrating their practicability. The Division is made up of sections devoted to the several phases of this work, each section being beaded by an investigator capable of supervising his particular work. The work is carried on at the experiment stations and field offices or in the field, whichever seems test suited for the work in hand. The following projects should be mentioned as particularly outstanding among those consummated successfully during the year: 1. Application of the type of chemicals known in the textile industry as wetting-out agents to flotation and agglomeration of ores, particulary soluble salts such as sodium and potassium chloride which must be treated in saturated brine. 2. Demonstration of a linear relation between surface and coercive force in magnetic minerals and its application to magnetic separation and to the determination of grinding efficiencies and other metallurgical data which require surface determination at very fine sizes. 3. Pilot-plant demonstration of the practicability of the reduction of iron ore by natural gas and conversion of this direct iron into steel by direct melting and by forging and rolling before melting. The structure and properties of the iron so produced were studied in detail. This report covers the fiscal year July 1, 1934, to June 30, 193b.

Jan 1, 1936

By Frank Foote, Eric J. Jette

The unusual physical, electrical and magnetic properties of the iron-nickel alloys has given rise to a voluminous literature. This work will be reviewed critically in "The Alloys of Iron and Nickel," a monograph of the Alloys of Iron Research Series, soon to be published. In what follows we shall therefore confine ourselves to those of the earlier investigations that involved the use of X-ray crystal-structure methods. The earliest X-ray work on the iron-nickel system was by Miss Andrewsl. Using the powder method of X-ray analysis purely as a means of identifying the phases present, she located a region between 20 and 30 weight per cent nickel in which body-centered and face-centered phases coexisted. No lattice constants nor details of heat-treatment were reported. Bain2 also reported some qualitative observations. McKeehan3 made a systematic investigation over the whole of the system, giving many of his alloys four and some five different heat-treatments. In alloys furnace-cooled from 900' to 950' C. he found two coexisting phases between 0.15 and 30 per cent nickel. The precision of the lattice-constant measurements was low in comparison with what can be obtained today. Even for alloys of the same heat-treatment, differences in the constants were often between two and ten parts per thousand. In regions where no change of lattice constant with heat-treatment should occur, differences of the same order of magnitude were found. Since the maximum change in the lattice constant of nickel with change of composition is only about 2 per cent of the constant for pure nickel, these variations in the constants for a given alloy cause the points to "scatter" badly about any curve that may be drawn to represent them and it is difficult to interpret such results. In spite of this, McKeehan shows that the lattice constant of nickel increased as the iron content increased. His results for the alpha-iron phase are less conclusive. Osawa4 also investigated the entire system. For alloys slowly cooled from 1150' C. and then filed into samples for X-ray analysis, he found

Jan 1, 1936

By Thomas G. Chapman

The four major steps in the production of marketable copper are mining, concentrating, smelting, and refining. In a few cases, however, leaching takes the place of concentrating, smelting, and refining, and in others ores are smelted without being concentrated. Copper ores have been milled since the early days of mining in the United States. Except in the Michigan district, most copper ores went direct to the smelter until the so-called porphyry mines were developed. At present, although considerable leaching and direct-smelting ores are produced, the bulk of the copper ore mined is concentrated. Improved methods of concentration have kept pace with the increased tonnages of ores milled.

Jan 1, 1936

By W. W. Adams

The safety record established by the coal-mining industry of the United States during 1934, although not as favorable as that for the previous year, was better than the record for any other year during the period 1930-34 for which complete figures covering fatal and nonfatal accidents at the mines are available. The number of accidents was 89.98 per million man-hours of employment compared with 86.74 for the year 1933, the latter being the lowest rate in any of the 5 years referred to. The rate was 105.60 for 1930, the first year covered by available data. Employment increased in 1934; the number of workers represented an increase of 8 percent over the year 1933, man-shifts of labor increased 16 percent, and the number of man-hours of labor increased 7 percent. The total number of man-hours of employment also exceeded the number reported for 1932, and was almost equal to the record for 1931.

Jan 1, 1936

By The Staff

FOR forty years cyanide men have been intensively engaged on the treatment of sulpho-telluride ores. So far as we know, the processes used today were-with the important exception of the concentration plus high-lime process at the Victor mill (1915)-in use, or had been tried, in the earl y years of the century. Roasting, bromocyanide, ordinary cyanide, table and vanner concentration, floating and treating the concentrate, roasting con-centrates prior to treatment, etc., all were used at Kalgoorlie in 1904 or earlier. Flotation, followed by shipment of the concentrate to the Golden Cycle mill, was the practice at the Vindicator mine, Cripple Creek, for some years prior to 1917. Similar practice was employed in the Portland Independence mill at Victor, Colorado, and was lacer superseded by the table concentration, high-lime cyanide treatment of rails of the older Portland Victor mill. During all this time, an immense amount of research was being clone on these ores by the staffs of numberless companies. Conclusions were drawn and mills built. But if the results of one per cent of this research were ever published in sufficient detail for intelligent use by others, the Lake Shore staff has been unable to discover them, or does not recall having clone so. Government laboratories-as for instance chose of the Mines Branch, Ottawa, in or about 1927-have touched upon certain methods in their publications, but they simply have not had the time to finish the job. The paper by W. E. Johnston, Tellurides-Problem or Alibi? (E. & M.]., Aug., 1933), aroused wide interest and comment. It published conclusions, some right and some wrong, and gave the evidence adduced by the author i:n support thereof. Conclusions published without supporting evidence are to most of us worse than no conclusions at all. We suggest chat, if even one-tenth of the operators had published full, detailed results of their laboratory work, ad vance in the treatment of sulpho-telluride ores would have been very much accelerated. Therefore, we venture to inflict upon the Institute a compendium of the results of laboratory work performed during the past few years at the Lake Shore mill. It is really a summary of the more interesting results to date, prepared by the mill staff for their own use and benefit. But we hope chat the discussion under any heading is so detailed chat it will be intelligible to anyone interested in that phase of the subject.

Jan 1, 1936

By Chas. G. Maier

The absence of plants on the Pacific coast for the reduction of iron ores usually is attributed to the fuel situation there. Thus, the bulletin of the. State Division of Mines for 1933, entitled "California Mineral Production," says: "There are considerable deposits of iron ore known in California, notably in Shasta, Mad era, Placer, Riverside, San Bernardino, and Los Angeles Counties, but production has so far been limited for lack of an economic supply of coking coal." It has been estimated that the six major steel plants of the Pacific coast have an annual ingot capacity of 600,000 tons. The present need for tin plate averages 300,000 tons yearly for California alone, of which some 12 percent is manufactured locally. If the consump¬tion of other iron and steel products in 1929 may be taken as an approximate, estimate of the normal requirement for such products, it may be estimated further that, 65,000 to 75,000 tons each of cast-iron pipe and steel reinforcing bars and 300,000 to 400,000 tons of structural shapes and plates will be required annually in California.

Jan 1, 1936

By Chas. F. Jackson

This bulletin is one of a series of Bureau of Mines reports dealing with mining methods, practices, and costs. A study of this subject was undertaken by the Bureau in cooperation with a large number of mining companies in 1928. This study continued for 5 years, during which engineers of the Mining Division of the Bureau visited most of the larger mines and many smaller ones in the United States, as well as several mines in Canada and Mexico. As a result of this study, 75 reports dealing with underground mining methods and costs at different mines were published as information circulars. Circulars also were issued on 6 open-pit mines and 2 gold-dredging operations. These circulars were written by the managers, superintendents, and engineers in charge of the operations, in some instances in collaboration with Bureau engineers. They were prepared according to a standard outline drawn up by the Bureau to obtain uniformity in textual treatment and in the arrangement and basis of setting up cost and operating data.

Jan 1, 1936

By D. Harrington

Part III-B, presented in this circular, completes the series reviewing the literature on effects of breathing dusts with special reference to silicosis; it includes data on the status and cost of compensation for silicosis in the United States and several foreign countries and a summary and general conclusions covering the whole series. Parts I, II, and III-A of the series have been issued as Information Circulars 6935, 6840, 6948 , and 6957; Part I defines and classifies dusts, indicates sources of exposure, and describes the physiological effects of breathing dusts; Part II-A discusses the principal dust factors producing pulmonary pathology and methods of determination of dust in air; Part II-B presents data on the engineering and medical control in the prevention of dust diseases and general recommendations for their control in industry; and Part III-A deals with the economic and legal aspects of dust diseases in industry.

Jan 1, 1936