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By D. N. Witman

One of the special uses to which the electric furnace has been put recently is the melting of an alloy of nickel and cast iron for the production of electrical-resistance grids. The metal sections of these grids, Fig. 1, are quite uniform for each pattern, but there is, among the various patterns, a variety of thicknesses. The cross-sections vary from 1/2 by 3/16 in. to as small as 1/8 by 1/8 in. The electrical resistance of a perfect casting lies within 10 per cent. above or below the fixed listed resistance for each pattern. Good molding is essential to success in the making of these grids, for with absolutely correct metal, a variation of 0.01 in. in width and thickness of section on some of the patterns may mean as much as 12 or 14 per cent. variation in resistance. The service for which these castings are intended demands that the metal, even in the smallest castings, be very soft, showing an open, gray, highly graphitic structure, in order that they may be resistant to shock, and stand up well under rough usage. The metal used for this purpose is a gray iron alloyed with 4 to 5 per cent. of nickel, which element, when the composition of the alloy is correct, imparts toughness and pliability to the metal and helps to overcome the tendency of metal to run white and become brittle because of the rapid cooling action of the sand mold. When cold, these castings can be twisted into various shapes, taking a permanent set without breaking. The alloy has approximately double the e1etrical resistance of ordinary cast iron. The metal specification is as follows: Per Cent. Silicon............................................. 2.40 to 2.60 Sulfur............................................. Under 0.05 Phosphorus......................................... Under 0.08 Manganese......................................... Under 0.40 Total carbon....................................... 3.60 to 4.00 Nickel............................................. 4.00 to 5.00 Copper............................................ 0.50 to 0.70

Jan 1, 1922

By Howard Scott, Henry S. Rawdon

The method of demonstrating the structure existing in a metal or alloy at high temperatures, by etching a polished sample after it has been heated to the desired temperature, is quite familiar to metallog-raphists. The usual procedure1 2 is to heat the specimen, previously polished for microscopic examination, to the desired temperature, in a neutral atmosphere (hydrogen or nitrogen), then admit the etching gas (chlorine, hydrochloric acid or similar gas) for a few seconds, and finally, after flushing out the etching gas with the neutral one, cool the specimen in the neutral atmosphere. The pattern produced by etching at a definite temperature is usually taken as a record of the microstructure prevailing at that temperature. It has frequently been pointed out that changes in composition of the surface metal occur during the preliminary heating in the neutral atmosphere, so that the appearance produced by the etching at high temperature may not exactly represent the condition of the interior of the specimen. To overcome this uncertainty, the heating has sometimes been done in vacuo,3 the etching gas being admitted when the desired temperature was reached, then pumped out and the specimen cooled in vacuo. The studies of Rosenhain, Humfrey, and other workers 4, 5, 6, 7, 8 dem-

Jan 1, 1922

By L. C. IlsLey

Briefly, a permissible schedule of the Bureau of Mines establishes certain minimum standards for safety; it gives details of test methods adopted to determine whether these standards have been met, and a list of charges for such tests. Any manufacturer has the privilege of submitting his product for test in accordance with the conditions outlined in the schedules. His action is wholly voluntary, for the Federal Government has no jurisdiction as to what equipment shall be used in mines, this authority being left to the various States. When the product of a manufacturer has met the schedule requirements, he is permit¬ted to advertise this fact and to attach an approval plate with the bureau's seal to each machine he makes that is identical in every way with the equipment tested, inspected, and approved by the bureau. This work of approval has grown by the addition of new schedules until at present a great many mines are using one or more classes of permissible equipment, and there is still a demand for other approved apparatus in the ever-widening field of electrically operated machinery. The safety of electrical equipment of this type depends on four fundamentals, namely, (1) correct principles of design; (2) proper assembly of parts at the factory; (3) proper assembly and installation of equipment at the mine; (4) and proper operation and maintenance after installation. The first two factors are within the province of the manufacturer. The bureau either inspects and tests several models of one product, such as electric cap lamps, or one model, such as an electric motor. If this series of tests proves satisfactory, the manufacturer is given the privilege of making other appliances, and assembling them in the same way; the approval plate he attaches is his guaranty that the equipment is identical with the one tested and inspected by the bureau. The third and fourth factors concern those who use such permissible equipment, and it is to them that this paper is mainly addressed, in an effort

Jan 1, 1922

By Lewis C. Karrick

In studying the destructive distillation or pyrolysis of oil shales, the primary consideration is to determine the effects of heat on the organic components of the shale. The impracticability of separating these organic components, collectively known as "kerogen", from the mineral matter with which they are associated renders the problem extremely complex. The behavior of the kerogan in the shale while undergoing the heating process is probably different from that of the same kerogen if it could be isolated and treated under similar temperature conditions, and in fact the results of actual distillations have shown that the physical properties of the mineral matter in the shale may be the cause of much variation in the products of retorting. It must be remembered that the inorganic .material of the shale is a heterogeneous mixture of minerals solidified into a very close-grained compact mass. This mineral mass has a thermal conductivity different from that of the kerogen, thus complicating the problem of even distribution of heat. Furthermore, the temperatures of dehydration of gypsum end some; hydrous silicates are included within the temperature range of the shale distillation, These minerals are frequently present in the shales; and the evolution of water vapors from them will affect the partial pressures of the hydrocarbon vapors evolved from the kerogen, probably tending toward, the improvement of the quality of the oil distillates. Carbonates and sulphides which are also frequently present begin to decompose within this range of temperature, and the gases produced from them may alter the chemical constitution of the oils produced from the kerogen.

Jan 1, 1922

By Graham Bright

Up until a few years ago most of the electrical equipment used in the mines of this country was developed for industrial purposes and was adapted for use in mines by slight modifications. It became apparent, however, that mining conditions differed widely from most industrial applications and it became necessary to design and develop apparatus, particularly suited for use under mining conditions. Most of the electrical apparatus used in mines today, however, does not owe its success entirely to mining development, but in many cases developments in other branches have been taken and improved upon and modified to meet mining conditions. Power Plant: In the earlier days the power plant for the production of electric power usually consisted of fairly small belt driven direct current generators operated from reciprocating non-condensing steam engines. Today where possible the mines purchase power from central stations and where not possible it is ususally produced from turbine driven plants using non-condensing turbines for the smaller plants and condensing turbines for the larger plants. The bad water conditions at many of the coal mines in this country is, responsible in a large measure for the high cost of upkeep and repairs in isolated power plants. This feature with the type of labor available makes it difficult to operate an isolated plant condensing except in the larger mines where water conditions are good and the apparatus can be taken care of. The geared turbine is a particularly simple and rugged piece of apparatus and requires very little attention over long periods of time. Hoists: The first electric hoists to be installed used various types of motors designed for railway or industrial purposes, and the control furnished was far from satisfactory. Today most of the mine hoist motors are of the alternating current type, especially designed for hoisting service. The control for motors of 200 H. P. or over is usually of the magnetic of liquid rheostat type, and as built today will operate over fairly long periods with a very moderate cost of up-keep. Hoists of 1000 H. P. or larger are usually of the direct current type using field control and receiving power from a flywheel or synchronous M. G. set. Hoists of this type have made remarkable records in regard to continuity of operation and low cost of up-keep. Where high speed operation is desired in either coal or metal mines, the D. C. equipment using field control and a separate M. G. set to supply power to the hoist motor is not only the safest and most economical but in many cases is the only type of equipment capable of satisfactorily obtaining the output required. A number of improvements have been brought out with the field control scheme in connection with the acceleration, retardation, overfeed and overwind of the hoist. With these new developments the hoist operator can no longer abuse the hoist by improper manipulation of the control handle. Until a few years ago the matter of safety devices was not given much consideration when installing hoisting equipment. At the present time the safety devices are considered one of the most important items in connection

Jan 1, 1922

By Carle Hayward

AT THE February, 1916, meeting of the Institute, a paper presented by Hayward and Raymond gave the results of a study on the effect of time in tempering medium-carbon steel, when the following conclusions were reached: It is not fair to consider the question settled when only three specimens were used for each treatment, but the results obtained indicate that for reheating quenched medium-carbon steel to temperatures below 500° it is only necessary to heat it through. Longer heating has little or no effect on the tensile strength, ductility, or hardness. At temperatures above 500°, increasing the time of treatment causes a slight falling off in hardness and tensile strength with a corresponding increase in ductility. In the discussion of the paper these conclusions were attacked and evidence presented that seemed to throw doubt on their accuracy. The authors, however, showed that this evidence was based on high-carbon or alloy steels and no facts regarding medium-carbon steel were presented. During this study the heat treatment was carried out in a small electric resistance furnace. It held nine specimens, but when these were placed in the furnace the temperature was lowered to such an extent that 30 to 40 min. were required to reach the desired heat. The authors pointed to this as a weak point in the investigation and it seemed wise to supplement the research by work on similar steel but using a different method of heating. This has been done and the results are given in the present paper. The Rhode Island Tool Co. cooperated by furnishing the steel and turning the tensile specimens.

Jan 1, 1922

By Thomas Varley

[For a year or more, statements have appeared in the technical press, and Especially in various trade journals, indicating that valuable metals such as gold, silver, platinum, and other rare metals, have been found and also have been successfully extracted from oil shales. These reports stated tat decarbonization and special methods of chlorination treatment, leaching and subsequent Precipitation, also cyanidation followed by table concentration of the residues after cyanidation, all indicated that told ad silver and other metals could be, and were, successfully recovered. Such articles have caused much misunderstanding, and as the correctness of some re of the statements made in them were questioned by some of the technical journals and by various chemists and metallurgists, an investigation of the subject. was begun by the metallurgical division of the Bureau of Mines, in order, if possible, to determine to what extent, if any, metals of value do occur in oil shales, and if so, the feasibility of attempting their recovery by tie processes said to have been used for teat Purpose. Inasmuch as the Bureau's station at Salt Lake City is investigating the recovery of oil from oil shales, the investigation of too recovery of metals from oil shales was assigned to my direction as superintendent 'of that station. An agreement had been entered into with the owner of m extensive oil shale deposit in Wyoming whereby I would personally collect the samples' of shales for use in the investigation.]

Jan 1, 1922

By James F. Kemp

In earlier gears, the custom prevailed of regarding the anthracite basins as cases of folding with slight development of faulting. Folding is so pronounced and, in the eastern and western Middle Fields, at times so violent, that the inference was a natural one and led to the widespread impression that practically all the disturbances of the seams could be explained in this way. The cross-sections and maps prepared forty or more years ago for the Second Geological Survey of P ennsylvania, by Mr. Ashburner under Prof. J. P. Lesley, exhibit little else than folds.' So far as I can discover faults fail in the charts, except in one small case in the Henry colliery near Plainsville on the outskirts of Wilkes-Barre. Some years ago, while spending a day or two in Wilkes-Barr, under the guidance of R. V. Norris, I looked over some recent and accurate cross-sections of a numbcr of the large collieries and was deeply impressed with the peculiar behavior of some of the seams and the intervening shales. Thus, a seam might present a small, more or less overturned fold, rising 30 to 50 ft. (9 to 15m.) above its general course, and yet the movement would be taken up in the overlying shales, so as hardly to be noticeable in the seams next above or below. These and similar anomalies, especially when shown with the accuracy of engineer's surveys, possess great scientific and practical interest, bearing as they do, not alone on coal mining, but on theoretical geology and the actual behavior of strata under great compressive stresses. In preparation for the semicentennial meeting of the Institute, an effort was therefore made to secure some of the most interesting sections for presentation to the members. The collection of illustrations here shown is mainly due to Douglas Bunting of the local committee, to whom and to the contributing companies acknowledgments are due. The illustrations are taken from all four of the main basins, but are chiefly from the portions nearest Wilkes-Barre. The first are in the

Jan 1, 1922

By R. Dawson Hall

*This paper was not read as it arrived too late. In the beginning of the last century "cottage industry" gave way to the factory system, and at present manufacturing that was once performed in homes is done wholly in factories. Division of labor came into being at the same time. In earlier years rarely more than a half-dozen men worked at the home of the master workman. Each group performed all the labor involved in changing crude material to the finished article, and many of the masters in a cottage industry themselves took the raw material and converted it by their own efforts into a highly specialized product ready for the market. Mining has in a degree moved in the same direction. But for the most part every man still has his own room. Pick miners in many places get their cars at the room neck, push them to the face, undercut their coal, drill their shot-holes, load and fire them, complete the breaking down of their coal, fill their cars, push them to the entry and also test their roof for weak spots, examine for gas, timber their rooms, bail them out and lay their own track. Mining is still in a way a "cottage" industry, only the cottage is a room in the mines instead- of a home. The men who gather the coal and take it to the tipple are in a measure like the middlemen who went from cottage to cottage and gathered the product of the owners or "masters", to use the term then prevalent. The change in ordinary industry from old methods to new came with machinery. The machines then introduced needed power for their operation, and distribution of power from house to house was too great a task for those times. Power could not readily be taken to machinery where water power only was available. It was necessary for the machinery and its workers to go to the power. Nor when steam was harnessed could every cottage have its steam engine. Compressed air and electricity had not arrived, and con-

Jan 1, 1922

By N. A. C. Smith

This report on the physical and chemical properties of typical crude oils of southern Louisiana and southern Texas is the seventh in a series of preliminary chapters of a bulletin covering the producing districts of the United States. Preceding reports* may be obtained from the Bureau of Mines on request. The details of the methods used in this survey in collecting samples and making laboratory tests have been discussed in the first three papers. A method of summarizing and interpreting the laboratory data has also been given, but most of the crudes included in the present report differ so radically from those previously reported, that it has been found advantageous to adopt a somewhat different method in making summaries. This method is described in detail later. If any errors or omissions are noted by readers, it is hoped that these will be brought to the attention of the Bureau of Mines, for correction before the appearance of the final bulletin.

Jan 1, 1922

By F. M. Van Tuyl

The oil industry had its inception in the United States in 1859 when the first oil well was drilled by Col. Drake at Titusville, Pennsylvania. From, a production of 2000 barrels for that year there was a slow but steady increase, with some fluctuations, up to 1901 for which year the output was approximately 69,389,194 barrels. Since that time the production has increased with leaps and bounds due to the rapid rise of the automotive industry, the widening use of oil as a fuel under boilers and the development of the. Diesel engine. The production for 1921 is estimated to have been 469,639,000 barrels. During the same year more than 125 millions of barrels were imported from Mexico. The oil industry, including the production, transportation, refining and distribution of petroleum and its products, is now the third largest in the country. Present Condition of the Industry During and immediately after the war the demand for petroleum exceeded the domestic production plus the imports from Mexico with the result that our storage oil was heavily drawn upon. Prices for crude exceeded all previous levels in the history of the industry. Pennsylvania crude sold for $6.10 per barrel and Mid-Continent crude for $3.50. Such prices stimulated wildcatting greatly with the result that several important new oil pools were discovered. Then as production increased the depression came which caused a large falling off in consumption. Pennsylvania crude fell to $2.25 per barrel and Mid-Continent to $1.00. Large oil companies such as the Standard, Sinclair and Empire took advantage of the situation, erected additional storage tanks and bought up millions of barrels to hold until better prices returned. Prices have already improved owing to a better market, but the domestic production coupled with the Mexican importations is still in excess of the demand with the result that the surplus is being stored. At the close of the year 1921, the U. S. Geological Survey estimates that there were 183,890,000 barrels of crude in storage in this country, the largest stocks in the history of the industry, yet an amount sufficient to supply the country for only 119 days at the present rate of consumption. Price reductions are again anticipated in some quarters but in view of the probable falling off in the Mexican output in the near, future due to the rapid rate of exhaustion of several of the most important pools and in view of the expected increase in consumption of gasoline and kerosene during the spring and summer months it is more likely that the present price level will be maintained. Present Sources of Domestic Supply Seven major oil fields are recognized by the U. S. Geological Survey in the United States. These are the Appalachian, Lima-Indiana, Illinois, Mid-Continent, Gulf Coast, Rocky Mountain and California. Two of these, Mid-Continent and California, supply about seventy-five per cent of the present total domestic output

Jan 1, 1922

IN any assay office it is of paramount importance to keep the men interested in their work; and in order to do this, men on routine work, such as lead, zinc, and sulphur deterrrrinations, slag analysis, etc, should be changed around monthly. This gives some variety and helps to keep a man's interest on his work, so that better work results. It may be maintained that to keep a man on the same class of work indefinitely makes him more expert at his work. This is certainly true; but in assaying, where accuracy is so essential, it is absolutely necessary for a man to keep his mind on the work, and not 'get' into a mechanical method of working. He is also on the alert to discover means for shortening his analytical methods, and his capacity forwork is increased. Another advantage is that the men get a good all-round training, and one is never at a loss to replace a man on any class of work when he is absent from any cause. This tends to smoother and more efficient running of the assay department. In industrial assaying it is often advantageous to have a result quickly, so that it will be of maximum benefit in the running of some part of the plant, In such a case it pays to sacrifice a little accuracy to speed up a method. The shortest method is less costly, and a quick approximate method is all that is required to give the superintendent the requisite information. Time is thereby saved, and the cost is less. In carrying out assaying for any large industrial plant, such as a smelting works, there is always a tendency for superintendents running the different departments to send in more samples for assay than are absolutely necessary when no system of costing is in operation. Some of these samples may involve a lot of work and heavy expenditure, as, for example, the estimation of only one impurity in a sample of refined lead. If the superintendent knows that the cost of assaying all samples sent in by,him is charged up directly against...

Jan 1, 1922

By C. A. Allen

In presenting a summary of the uses of fine and pulverized coal the writer has borne in mind that we are not trying to determine what a combustion engineer should know but we are only trying to find out in what ways the consumption of slack can be stimulated. First discussing the use of powdered coal it can be stated that it has passed the first experimental stage but is still capable of much development and improvement. It has already found successful application in stationary and locomotive boilers, cement kilns, calcining furnaces, reverberatory smelting furnaces and many other types of furnaces, such as open hearth furnaces and annealing furnaces. For stationary boilers it seems to have been thoroughly demonstrated that powdered coal is more efficient than stoker installations. Over-all efficiences of boiler and furnace in stoker installations of the best type run from 70 to 76 per cent; whereas the efficiency of powdered coal installations averages slightly over 80 per cent. However, due to the increased cost of pulverized coal, the increased efficiency of these installations over stokers, from a money stand-point, will not be more than 1 or 2 per cent. The fusing of the ash in pulverized coal installations has given some trouble but apparently is easily overcome, on the other hand the fine ash, which is carried along with the draft, causes trouble both in the boiler and by settling on surrounding buildings or ground. Offsetting the disadvantages the great advantages of pulverized coal for stationary boilers seem to be: First-the ease with which a change in the load on the boiler can be taken care of. Second-when a boiler is cut out for a short period the "stand-by" losses are much less and, Third-a much poorer grade of fuel can be used. In many cases where pulverized coal has been used it has replaced slack coal which is of little advantage to the coal operator. However,, in other places it has replaced gas or oil and this is where the coal man is interested. Pulverized coal has the same advantages as the liquid or gas fuel but the question as to which is preferable depends on their relative cost at the point of use. In small stationary boilers where stokers are not used, very frequently the larger sizes of coal are, and it would be an advantage to the coal industry for them to be converted so as to burn pulverized coal, but so far there are only records of a few of such small installations having been a success and there is apparently room for a large amount of experimentation. In furnaces, such as smelting and assaying furnaces, annealing furnaces, etc., slack coal is not used and where pulverized coal has been installed it nearly always replaces fuel oil or gas. Just how much increased consumtion of coal can be made by pulverizing it for use in furnaces of this type can not be determined but it seems worthy of investigation. For locomotive boilers pulverized coal has found some application up to date but where it was being used in the United States it was stopped when we entered the war. In Brazil, however, the Central Railway has been using pulverized coal for locomotives with excellent results. If it could be possible to apply it to locomotive use where fuel oil is now used, or the larger sizes of coal, it would certainly make a big difference in the slack situation. Now as to the uses of slack coal without pulverizing. The writer's investigations lead him to believe that the greatest opportunities in this direction are in the line of increasing its use by apartment houses and small home owners. In fact in looking into the subject I found that a number of men in Salt Lake City are using run of mine coal in the usual type of house furnaces, some of them by separating the fines and wetting them down before feeding to the furnace claim they get no loss whatever through the grate. However, for best results with fine coal different types of furnaces must be installed and for apartment houses it would seem necessary to have either a small automatic stoker or else spray the fine coal in with an air blast from

Jan 1, 1922

By Eugene McAuliffe

SINCE 1917, the bituminous coal industry has surged, violently at times, across the nation's social, industrial and economic foreground. To-day a silent, yet more active, force is working within the industry, and the movement now taking place, if allowed to continue, will cause serious consequences when coal is again wanted at the rate of 550,000,000 tons annually instead of at the rate of 400,000,000 tons, the apparent requirement for 1921. I refer to the shift of tonnage from the highly unionized fields of Pennsylvania, Ohio, Indiana and Illinois to the non-union fields of Pennsylvania, West Virginia, Alabama and certain western states, and to the so-called union fields in Kentucky and Colorado, on which the union saddle rests lightly. This movement, in the absence of the usual winter transportation shortage, is taking place rapidly and will be accentuated if, as is probable, work is suspended in the union mines on March 31 next. This drift of tonnage has been made possible by the unit wage reductions in the non-union fields and by the modification of the so-called conditions that have been saddled on all mines wherever the United Mine Workers have gained a foothold; these changes permitted the first reduction in mine cost, which made possible the securance of contracts; better running time assisted in making further reductions, and the transfer of ton-nage served to increase the unit cost in the field from which it was transferred. This situation not only opposes the highly unionized operation but brings about a transfer of traffic from the roads serving such mines to those that serve in a primary or secondary manner the more favored localities. The net result is evidenced in (a) the migration of union labor to the non-union mines; (b) the deteriora-tion and decadence of union properties; (c) the neces-sary curtailment in the purchase of new equipment and in the maintenance of existing equipment and track facilities on the part of the carriers serving the union fields. This, in turn, when business is restored to normal or to the point above normal that invariably follows an adverse swing of-the business pendulum, will cause (d) a shortage of coal and coal transportation facilities; (e) an era of coal speculative debauchery with exorbitant prices and serious deflection in the matter of quality; (f) a period of labor unrest followed by de-mands for increased wage rates supplemented by a marked loss in individual efficiency, with, resultant strikes, business unrest, and the pressure of new eco-nomic theories. In 1918, the labor status with respect to relative tonnage produced was approximately as follows: pro-duced in highly organized fields, 62 per cent.; produced in partly organized fields, 21 per cent.; produced in unorganized fields, 17 per cent. During the strike of November and December, 1919, the mines that remained at work attained 35 per cento of the nominal production of soft coal, a situation made possible by the migration of union labor to non-union mines and the concentration of the nation's coal trans-portation facilities on the rails of the carriers serving the non-union fields. The history of the efforts made by the carriers to untangle the car scrambling which took place during this period and which sent the self clearing battleship type of car into western territory where it could not be readily unloaded, and the western gondola type of car to New England and the seaboard, is yet painfully recalled. -This confusion proved a serious factor in the coal car shortage that continued throughout the following year. We are drifting toward a similar situation now, propelled by economic forces rather than by a sudden strike.

Jan 1, 1922

IN previous discussions on the occurrence of gold in the Bendigo quartz reefs the opinion has been put forward that the gold shoots are primary concentrations in the quartz reefs during the period of vein-formation. The view has been based upon the constant features of the gold shoots in a large number of individual reefs, independent of their depth below the surface. These features include the mineral associations accompanying the gold, the appearance and association of the gold in the quartz, the similarity in all respects (excepting mineral content) between richly gold-bearing quartz and poor quartz, and the variations in mineral content in the reef apart from gold. The view has been supported by a relation of the gold shoots to faults, together with the dependence of the reefs on the existence of pre-mineral faulting. The secondary deposition of gold has only been observed in a few instances .associated with the younger monchiquite dykes, and is of no economic importance.

Jan 1, 1922

By G. B. Pryde, R. M. Magraw

In laying out a new mine, provision should be made for the ultimate recovery of as much coal in any given bed as is consistent with safety and economic mining. Though each mining district, if not each individual mine, has problems that make the adoption of any hard and fast rule impossible, certain basic principles are adapted to practically all conditions. One of the most vital is the provision for barrier pillars of ample dimensions to protect all haulage and permanent airways during the life of the property. Where conditions permit, room or butt entries should be driven on the strike or slightly to the rise, and rooms turned at right angles to these entries. The width of rooms and room pillars is governed by conditions prevailing in the mines under consideration. A safe rule is: In advancing, extract not more than 25 to 35 per cent. of the entire seam; in exceptionally thick seams, considerably less than 25 per cent. should be taken. Rooms usually vary in length from 250 to 350 ft. (76 to 106 m.) with a barrier pillar of not less than 80 ft. between the last crosscut. in rooms and the back entry of the level above. All entries, rooms, and entry-and-room crosscuts should be driven .on sights and room crosscuts should be driven at, right angles to the direction of the rooms. In mines under excessively heavy cover or where roof conditions are bad, rooms should be driven narrow and a barrier pillar left at every fifth to tenth room. This barrier should be of such dimensions that one or more rooms, with pillars of usual dimensions, may be turned through it when the barrier is no longer required. Two of the advantages of such a barrier are the protection of the panel against peaking of roof load during pillar extraction and the easy closing of the entry in case of fire. Where economic conditions permit, it is preferable to follow the retreating panel system of mining. In the case of coal that outcrops, and even in cases where no outcrop is exposed, it is preferable to commence pillar extracting on the high side of the mine. Where the retreating

Jan 1, 1922

By James E. Harding

The usual method of sampling mineral deposits is to drill holes and assay the sludge or core. Though the results thus obtained may not represent the true average value of the deposit, it is on these results that estimates of practically all large orebodies are made. In a large number of cases, the results of exploitation fall far short of the estimated value of the orebody. The standard method of making these estimates is to find the cubic contents of triangular prisms, in the apexes of which the drill holes are placed, by. multiplying the surface area by the average depth of the ore in the three drill holes and then multiplying the cubic contents by the specific gravity of the ore or rock to find the tonnage. The assay value is found by dividing the sum of the products of the depth of ore in each hole and the corresponding assay value by the sum of the depths of the ore in the three holes. As the latter part of this method is subject to many mathematical errors, it should not be depended on. Some engineers, therefore, use a discount factor, but as this factor is either arbitrarily selected or is obtained by obscure methods, the results are no better than guesswork. The standard method is correct when the drill holes are so laid out that the triangular prisms are equilateral in cross-section. But as ore deposits cannot always be drilled into at regular intervals and because of the human factor, if many holes are drilled, triangular prisms of all degrees of angularity are produced. In such cases it is necessary to assume that the influence of the different holes is not the same in all directions, which assumption of course is absurd. The area of the triangular prism is usually found by scaling; an ore-body of sufficient size to justify churn drilling is too large to be handled conveniently on maps having a scale larger than from 1000 to 1 to 1,500 to 1 and maps of such scales cannot be accurately measured. A variable is thus introduced in the first operation. In addition, the scaling is frequently done from blueprints, which sometimes shrink as much as 4 per cent. between printing, washing, and drying. The error due to scaling may be eliminated by surveying the location of each hole and

Jan 1, 1922

By William E. Ford, Edward Salisbury Dana

1. Normal Class (31) Axinite Type 2. Asymmetric Class (32) Calcium Thiosulphate Type Mathematical Relations of the Triclinic System 216. Crystallographic Axes. - The triclinic system includes all the forms which are referred to three unequal axes. with all their intersections oblique. When orientated in the customary manner one axis has a vertical posi-

Jan 1, 1922

By T. E. Swigart

In the production of oil end gas, engineering methods have been applied less than in any other branch of the oil industry. While refineries, gasoline plants, pipe-line and other transportation systems, and even drilling wells to a great extent, take advantage of engineering skill, the tendency has been to assume that the handling of producing wells is merely a mechanical and routine matter. At present few companies employ engineers to study oil and gas production methods with a view of increasing the general efficiency of recovery, but in vie, of the advancement in other lines of the petroleum industry by the application of engineering principles, does it not seem likely that the production branch may benefit also by engineering studies? Engineering applied to the handling of producing wells falls under two general headings, - first, the efficient handling of wells from the time of their inception in order to obtain the greatest possible ultimate production, and, second, the rehabilitation of old properties that have been handled carelessly in their early lives. To date, the engineering work that has been done on oil production problems falls mostly in the second class. For example, the use of vacuum and the application of compressed air have proved successful in some instances in stimulating wells of low gas pressure. These methods are costly to apply and are adapted to small wells in which the gas is almost exhausted, or in which the original gas pressure is negligible. The experiments described in this paper fall under the first heading, as they were made with an idea of learning toe probable extent to which the gas production of an oil well can be curtailed while gas in the sand is still plentiful, and thus saved for doing work during the later period of a well's life. Because of the scope of the experiments, this paper does not include a discussion of back pressure on flowing wells or for purposes other than cutting down the gas produced with each barrel of oil.

Jan 1, 1922

By W. H. Schacht

In the Lake Superior District, the air indoors must be heated continuously during eight months of the year and occasionally during the remaining months. Incident with mining in this district, therefor?, there is need for heating many of the buildings connected with these operations. In addition to the mine buildings, that is, shops, engine houses, offices, change houses, etc., such public buildings as schools, library, and theater, when close to the mines, are often supplied from the mine heating mains. At the Copper Range Company's mines, Champion, Trimountain and Baltic, the heating surface thus supplied from the mine mains is over 50,000 sq. ft. (4645 sq. m.) which requires a steam consumption, at times, of 18,000 Ib. (8165 kg.) per hour, or the equivalent of a rate of ovcr 50 tons of coal per day (were live steam used). This figure is based on a consumption of 1/3 Ib. per sq. ft. of heating surface during the coldest weather, and provided the system is not wasting steam by blowing it to the atmosphere or into the return line on account of leaky traps, which so often is the case. Under the latter conditions, steam consumptions of three to four times the above rate are not uncommon. This shows that the cost of heating is of enough importance to he given serious consideration, especially at this time of rising prices of fuel. The power and heating value of exhaust steam arc appreciated by most engineers, and its application for such purposes is general. At our stamp mills, the exhaust from the stamps is used to operate low-pressure turbines, thus reducing the former water rate per horsepower developed by more than 50 per cent. At the above-mentioned mines, electric motors have replaced the many small steam engines, so that this supply of exhaust steam has been practically eliminated. The larger engines are compound, triple, or quadruple condensing. The hoists, however, in all cases are simple and non-condensing and of two sizes, namely, 24 by 60 in. and 32 by 72 in. (61 by 152 cm. and 81 by 183 cm.). These hoists now offer the only available supply of exhaust steam; but as this flow is intermittent and varies from extreme violence to zero, the steam so discharged cannot be

Jan 1, 1922