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By L. C. Graton

The federal taxes on incomes and excess profits are of course heavy. In 1917, the value of the mineral production of the United States was a little in excess of $5,000,000,000. The total of federal taxes for that year, for the mineral producing companies, as computed by themselves, amounts, according to tentative compilations, to about $207,000,000, and the total for the comprehensive group of mineral and metal industries to about $766,000,000, which figures represent respectively 9.5 per cent. and 35.1 per cent. of the total tax paid by all corporations. Because of greater complexities in applying the revenue laws to mineral properties than to most other industries, opportunity is afforded for wide differences of view. The taxes indicated above, therefore, are not final and may conceivably be very materially increased. For 1918, the taxes are expected to be still greater, but no compilations are yet available. Taxes at a high rate are to continue indefinitely. The subject is clearly of gravest import to the mining industry in particular. The Commissioner of Internal Revenue, who is charged by law with the administration and collection of the taxes, is determined that these functions shall be performed in a just and businesslike way. Fairness and finality are to be the chief objectives. In view of the peculiar conditions that attach to the tax program as applied to mines and other wasting industries, like oil, gas, and timber, the Commissioner has resorted to professional advice and assistance by manning a Sub-division of Natural Resources with competent engineers, brought in from the several industries, into whose hands he has placed for solution the technical questions involved. These engineers have a two-fold duty: (1) to devote to the solution of these problems their own knowledge and experience; (2) through their acquaintance with their respective industries, and with the men engaged in those industries, to focus upon these problems, by conferences and otherwise, the best opinion of the country. The principal object of this paper is to acquaint the mining profession with the attitude of the

Jan 1, 1923

AT THE dinner at the Cosmos Club in Washington, tendered to Herbert Hoover on Jan. 5, on the occasion of his retirement from the presidency of the Federated American Engineering Societies, he made an informal speech in which he pointed out not only the unique position which the engineer now occu-pies by virtue of the new Federated Societies but also the opportunity that is thus presented for national service. In this connection and in pointing out some of the reasons for the present economic maladjust-ment, Mr. Hoover said in part: This body has entered upon a path of public serv-ice that is unique in the whole United States. The engineer has devoted himself all these years to the upbuilding of the material values of the United States. He has done that effectively more effectively than-has been accomplished in any other of the great countries of the world. The birth of this society marks the evolution of the engineer into an interest in public affairs. With his intelligence, his experience and training and the unique knowledge that he possesses not only of the material but the intangible values among our people, he is now organized so that his united voice may become heard outside of his profession. We have probably 175,000 engineers in our country, representing an intellectual possibility for service possessed by no other group. It is therefore an augury of real social development when the engineers of the United States join together for purposes of public service.

Jan 3, 1922

By Vincent P. Gi. ccnella

GOLD was discovered in Gold Canyon on May 15, 1849. Following this discovery placer miners worked the gravels in the canyon for-ten years, finally discovering the outcrop of the Comstock lode at Gold Hill in May, 1859, and in Ophir ravine on June 12 of the same year. Before long large quantities of gold and silver, were taken from the lode and one of the West's most spectacular mining booms drew thousands of fortune seekers to Nevada. After a long period of production activity waned and in late years little mining was done. The recent reopening of the old mines and the discovery of ore in other parts of the vein, and in other veins of the district, has led to a revival of interest in the Comstock. Virginia City, Gold Hill, and Silver City, situated along the great vein system, are enjoying a period of prosperity and a large influx of people.

Jan 1, 1934

By G. Sachs, Jr. Brown W. F., Ebert L. J.

It is a generally recognized fact that a steel quenched from the austenitic range and tempered to yield a structure composed of tempered martensite becomes increasingly more ductile with increasing tempering temperature. However, the conventional tensile test fails to yield any value that is sensitive to differences in behavior on tempering among the various low-alloy steels or among different heats of a particular steel. The notched impact bending test, on the other hand, has been recognized for a considerable length of time as capable of revealing differences in impact properties among various steels tempered to 'the same strength level (i.e., the same tensile strength in a conventional tensile test). However, this test is very complex and its significance has not been clarified up to the present time. Of its three characteristic features—the high speed, the notch, and the bending—the notch has been found by Davidenkov2 to be the most potent embrittling factor. Recent investigations on low-alloy steels have shown static notch-bar tensile tests to be more lucid and to evaluate the metal properties in much the same manner as impact tests. In an attempt to analyze the fundamental nature of this test, it was found possible to separate the effects of the two basic characteristics of the stress pattern introduced by the presence of a circumferential notch, the stress state and the high initial stress concentration at the notch bottom. The major conclusions drawn from these previous investigations were as follows: I. The magnitude of the triaxiality at fracture depends primarily on the initial notch depth. Its effect is a great reduction in the average ductility (contraction in area at fracture in the notched section) as compared with that observed in uniaxial tension. This triaxial stress state occurs at a point in the interior of the notch specimen. It determines the notch ductility if the notch is mild and/or the metal possesses a considerable ductility. On the contrary, brittle specimens probably fracture on the metal surface (at the notch bottom) at which point biaxial stress state is present. This biaxiality also considerably reduces the ductility of the metal. For small notch ductilities the notch strength and the notch ductility become very sensitive to embrittling factors. This is contrary to the behavior. of the ductility values derived from a conventional tensile test, which are comparatively insensitive.

Jan 1, 1947

By Ebert L. J., G. Sachs, Jr. Brown W. F.

It is a generally recognized fact that a steel quenched from the austenitic range and tempered to yield a structure composed of tempered martensite becomes increasingly more ductile with increasing tempering temperature. However, the conventional tensile test fails to yield any value that is sensitive to differences in behavior on tempering among the various low-alloy steels or among different heats of a particular steel. The notched impact bending test, on the other hand, has been recognized for a considerable length of time as capable of revealing differences in impact properties among various steels tempered to 'the same strength level (i.e., the same tensile strength in a conventional tensile test). However, this test is very complex and its significance has not been clarified up to the present time. Of its three characteristic features—the high speed, the notch, and the bending—the notch has been found by Davidenkov2 to be the most potent embrittling factor. Recent investigations on low-alloy steels have shown static notch-bar tensile tests to be more lucid and to evaluate the metal properties in much the same manner as impact tests. In an attempt to analyze the fundamental nature of this test, it was found possible to separate the effects of the two basic characteristics of the stress pattern introduced by the presence of a circumferential notch, the stress state and the high initial stress concentration at the notch bottom. The major conclusions drawn from these previous investigations were as follows: I. The magnitude of the triaxiality at fracture depends primarily on the initial notch depth. Its effect is a great reduction in the average ductility (contraction in area at fracture in the notched section) as compared with that observed in uniaxial tension. This triaxial stress state occurs at a point in the interior of the notch specimen. It determines the notch ductility if the notch is mild and/or the metal possesses a considerable ductility. On the contrary, brittle specimens probably fracture on the metal surface (at the notch bottom) at which point biaxial stress state is present. This biaxiality also considerably reduces the ductility of the metal. For small notch ductilities the notch strength and the notch ductility become very sensitive to embrittling factors. This is contrary to the behavior. of the ductility values derived from a conventional tensile test, which are comparatively insensitive.

Jan 1, 1947

By G. Sachs, L. J. Ebert, W. F. Brown

IT is a generally recognized fact that a steel quenched from the austenitic range and tempered to yield a structure composed of tempered martensite becomes increasingly more ductile with increasing tempering temperature. However, the conventional tensile test fails to yield any value that is sensitive to differences in behavior on tempering among the various low-alloy steels or among different heats of a particular steel. The notched impact bending test, on the other hand, has been recognized for a considerable length of time as capable of revealing differences in impact properties among various steels tempered to the same strength level (i.e., the same tensile strength in a conventional tensile test), However, this test is very complex and its significance has not been clarified up to the present time. Of its three characteristic features-the high speed, the notch, and the bending-the notch has been found by Davidenkov2 to be the most potent embrittling factor. Recent investigations on low-alloy steels3,4,7,8 have shown static notch-bar tensile tests to be more lucid and to evaluate the metal properties in much the same manner as impact tests, In an attempt to analyze the fundamental nature of this test,8 it was found possible to separate the effects of the two basic characteristics of the stress pattern introduced by the presence of a circumferential notch, the stress state and the high initial stress concentration at the notch bottom, The major conclusions drawn from these previous investigations were as follows: I. The magnitude of the triaxiality at fracture depends primarily on the initial notch depth. Its effect is a great reduction in the average ductility (contraction in area at fracture in the notched section) as compared with that observed in uniaxial tension, This triaxial stress state occurs at a point in the interior of the notch specimen, It determines the notch ductility if the notch is mild and/or the metal possesses a considerable ductility. On the contrary, brittle specimens probably fracture on the metal surface (at the notch bottom) at which point biaxial stress state is present, This biaxiality also considerably reduces the ductility of the metal. For small notch ductilities the notch strength and the notch ductility become very sensitive to embrittling factors, This is contrary to the behavior of the ductility values derived from a conventional tensile test, which are comparatively insensitive.

Jan 1, 1946

By A. F. Banks

INTRODUCTION Selective flocculation as a method of desliming potash flotation plant feed has been in commercial use since November, 1974.l It was installed to replace a 1ess efficient mechanical desliming process. While most plants operating in the Saskatoon area of Saskatchewan were designed for 4% to 5% insolubles in practise the quantity and quality of the insoluble materials in the ore has been variable. The variability of the ore has contributed to less than optimum efficiency in the desliming and consequently, the potash flotation circuits. This lower than expected efficiency contributed to the commercialization of a patented process2 through large scale pilot plant testing. Referring to published information and experience, the application of selective flocculation-flotation of slimes to sylvinite ores will be compared with the more conventional mechanical methods of desliming. THE ORE The ore beds being mined in the Saskatoon area of Saskatchewan have proven to be much less uniform than originally thought (Figure 1). The insoluble content of the plant feed is variable in both quantity and quality due to two factors, the presence of disturbances and the structural weakness of the mud seams immediately above the ore beds. Some alteration of the insolubles in the vicinity of disturbances has made them more difficult to liberate and makes ore from the disturbed areas less amenable to treatment.

Jan 1, 1980

In accordance with the requirements of By-Law LX,- I beg leave to submit herewith the report of the Library Committee for the year 1916. The activities shown by the sale of the Institute's publications during the year are somewhat larger than last year, due principally to the increased sale of special editions on account of the larger sale of the Posepny and Emmons Volumes, owing to increased advertising and to the reduction in price of the Emmons Volume. The sales were distributed as follows: Sale of Transactions $3,237.07 Sale of Special Editions 1,722.50 Sale of Bulletins and Pamphlets 2,263.95 Total $7,223.52, The Institute library has now been merged with the libraries of the. other three Founder Societies and is known and administered as the Library of the United - Engineering Society. When this merger, was effected, a proviso was made that the books contained in the Institute library up to the date of the merger were still to be considered as the individual property of the Institute, and this arrangement applied also to the libraries of the other two Founder Societies. At the time that the American Society of Civil Engineers joined as a fourth Founder Society, they immediately turned over their entire library to the United Engineering Society, relinquishing all property rights in the books entirely.

Jan 2, 1917

By Simon H. Ash

The coal-mining districts of Washington are mainly west of the Cascade Mountains; Fig. 1. The mines are on the foot hills of the slope, the lignite fields of Lewis and Thurston counties extending into the valleys west of the mountains. An exception is the Roslyn field, a small but important area on the eastern slope. If western Washington is divided into three areas from north to south, the bituminous coal fields and most of the active operations will be found largely in the middle area. The southern portion contains lignites over a large area. In the northern portion, mining is practically restricted to one mine, the Bellingham, which is working a subbituminous coal seam near the city of Bellingham. The degree of alteration that the coal of a particular field has undergone may be gaged roughly by the position of the field with reference to the Cascade Mountains. The lignites of Tenino, Tono, Mendota, and Castle Rock, on the railway line connecting Seattle and Portland, occur in a region of low relief, in which the Eocene coal measures have suffered only minor disturbances. Subbituminous coals occur in the foot hills, as at Renton, Newcastle, and Bellingham. Coalg high in fixed carbon are found nearer the mountains, where the measures have been sharply tilted and folded, as at Black Diamond and Carbonado. The two typical anthracite fields are located still higher, in the rugged mountains where outcrops appear both in deep gorges and on ridges at elevations approaching 5000 ft. At Carbonado is found the only semianthracitc seam worked on a commercial basis. The occurrence of this seam in a region of bituminous coal is due to the nearness of an igneous sill, which has changed its character from bituminous to semianthracite. Purpose of Paper On account of the various faults and dips and the varying nature of the wall rock, many difficulties are encountered in mining and winning the coal. The paper gives some of the methods used in mining and, in some detail, the conditions that affect the efficiency of these methods.

Jan 1, 1925

THE Copperton mill in reality was a sort of proving ground. It was. designed to serve three purposes: (1) to verify the accuracy of the mine sampling by actually treating substantial tonnages of ore, (2) to demonstrate on a reasonably large scale the percentage of the copper in the ore that could be recovered, and (3) to permit the testing of various kinds of machines and devices for crushing and concentrating the ore, so as to guide the engineers in designing the proposed 6000-ton milling plant at Garfield. As a matter of fact, it contained a lot of second-hand equipment sent by MacNeill and Penrose from the works of the United States Reduction &Refining Co. in Colorado; and it was by no means a model installation. Probably it would have been even less efficient, except for the skillful work of George O. Bradley and-Frank-G, Janney, both of whom had worked with Jackling at Mercur. Bradley was a mechanical engineer employed to design the plant. Later he directed the design of the concentrator at Garfield and remained as consulting mechanical engineer to the company until 1915. Janney, who afterwards became manager of mills, a position that he retained until his death in 1916, was a skilled mechanic at the Golden Gate mill at Mercur when Jackling built the plant in 1897. His flair was making machinery do what it was intended to do. He was not an ore-dressing engineer in a technical sense; but Jackling him- self was a specialist in this respect as well as in designing and construction and Janney's mechanical aptitude made him a particularly valuable man in the Utah organization. John McDonald, another of Jackling's Mercur associates, was the first mine superintendent. With practically all of the available funds earmarked for construction of the Copperton

Jan 1, 1933

. S. W. PARR, * Urbana, Ill. (written discussion ? ).-Multiplication of argument is unnecessary to establish the desirability of coking coals at low temperatures, that is to say, below 1200° F. The value of the semi-coke thus produced would doubtless go far toward solving the problem of smoke prevention, and suggests the possibility of the substitution of a smokeless fuel for anthracite and so-called smokeless coals. Whether such coke would have any value as metallurgical coke is a question which cannot be answered for lack of any experimental data in the use of such material. Of course interest is accentuated, at the present time, in the amount and character of the tars, which promise greatly to exceed in values the products obtainable from. the high-temperature process. The difficulties encountered in adapting the principles of low-temperature carbonization to industrial methods are well nigh insurmountable. Briefly stated, there is involved the heating of the center of a mass of non-conducting material by the external application of heat. It is a well established fact that the center of the mass of coal in a standard

Jan 11, 1918

By Austin Park

More metal at a lower profit continued to be demanded from the mining industry during 1969. Correspondence with U.S. and Canadian mining districts and a study of the mining literature indicate that, a large majority of the mines are keeping pace and rising to the challenge. Continued research and better understanding of pneumatically applied concrete for roof and wall support was of top interest. Many mines are changing mining methods for the adaptation of load-haul-dump units. The most recent adaptation being the use of these units in cut- and-fill stoping and in various types of development headings. Boring methods and use of two- or three- boom drilling jumbos mounted on rubber tires for versatility continues to be the favorite approach to the demand for rapid excavation.

Jan 1, 1970

By AIME AIME

IN many countries the lack of liquid petroleum supplies has centered interest upon the hydrogenation of coal and coal tars for the preparation of motor fuel. In the United States, hydrogenation has been of greater interest for grading up low-value petroleum fractions to the more valuable volatile fuels and for the preparation of a variety of premium products, including aviation gasolines, solvents, Diesel fuels, and lubricating oils. Chemically, the basic reason for this process is that, as shown in Table 1, the ratio of hydrogen to carbon (H/C ratio) in available raw materials is quite different from that characterizing the products sought.

Jan 1, 1936

By J. T. Eash, W. S. Crowell, E. M. Wise

The practice of dentistry, particularly the construction of artificial dentures and "bridges," involves a unique and difficult application of the precious-metal alloys. Appliances used in the mouth are continuously exposed to corrosive agencies which can hardly be described as mild, and must remain free from tarnish and be substantially immune to corrosion. Limitations with respect to space and weight demand high physical properties, while complexity of form requires ease of working. The high corrosion resistance required necessitates the use of alloys of high precious metal content. The usual expedient of resorting to mechanical working to produce the requisite strength and stiffness cannot be utilized because of the frequency of annealing and soldering operations. To meet these difficult conditions manufacturers of dental goods were early led, unknowingly perhaps, to the production of precipitation-hardening or temperable alloys. The excellent properties of iridium-platinum may have suggested the addition of platinum metals to the conventional gold-silver-copper alloys to produce greater strength and hardness. It was found that such quarternary alloys retained their high physical properties after passing through the usual soldering process; i. e., heating to 750° to 800" C. and cooling naturally in the air. Later it was discovered that they could be softened and rendered more ductile by heating to the same temperature and quenching in water. These early examples of precipitation hardening, for years the common knowledge of dental practitioners and laboratory technicians, escaped the attention of the scientific world and discovery of the transformation which was responsible for this hardening was disclosed by the Russian investigators of the system Au-Cu, Kurnakow, Schemtschushny and Zasedatelev~,(~)$ although the optimum conditions for securing good properties in aged alloys were not given attention.

Jan 1, 1932

By N. K. Chen, R. Maddin, K. T. Aust

Lattice rotations occurring on the tension and compression sides during the bending of molybdenum single crystals at room temperature were followed in detail. Observations were also made concerning crystallite rotations and slip traces. &apos;The results indicated the participation of (110) as slip planes and the<111>as slip directions. Crystallite fragmentation during bending was also noted. EVERAL investigations have been conducted on pure bending of face-centered cubic metals.&apos;-" Structural changes as a result of "bend-gliding," and the importance of bending and constraints during conditions of axial stressing, have been noted.&apos;," It was evident that the mechanism by which the bending deformation occurs is more complex than the case of simple shear. Studies of the bending of body-centered cubic metals from the aspect of the crystallographic mechanism appear to be lacking. Molybdenum single crystals therefore were subjected to deformation by bending in order to determine the reaction of the body-centered cubic lattice to bending stresses. It might be expected for the bending of single crystals that lattice rotation as represented by the axis of compression would proceed toward the pole of the active slip plane and that rotation of the tensile stress axis should indicate the slip direction.&apos; It was believed therefore that a study of the tension and compression sides of bent molybdenum single crystals should give data concerning the operative slip system. Specific problems which are pertinent to the overall picture of plastic deformation were also investigated, e.g., whether the constraints offered by pure bending give rise to the deformation band, and also the nature of the asterism occurring on the tension and compression sides during the stages of deformation. Experimental Procedure Eight single crystal specimens were grown from sintered molybdenum rods 143 in. diameter using the method described previously.6 The purity of this material was reported as 99.9 pct as described elsewhere.&apos; The specimens were % to 1/10 in. in diameter x 7 in. long, with single crystals approximately 1 to 2 in. in length occupying the entire center sections of each specimen. The specimens were elec-trolytically polished using an electrolyte of 300 cc methyl alcohol, 60 cc H2SO4, 130 cc HCl, and a current density of 4 amp per sq in. Each specimen was then loaded in a bending apparatus similar to that used by Yen and Hibbard,&apos; as shown in Fig. 1. The load was applied by means of a spring and screw arrangement through four ball-bearing surfaces set 1.5 in. apart. Either the inner two bearings or the outer two (A, B, Fig. 1) were attached to a movable steel plate (D) through which the load was transmitted. Since the apparatus was mounted on a track of the X-ray apparatus, the tension or compression side of the specimen could

Jan 1, 1954

By Wallace Ralston

The East Texas district includes the northeast 38 counties of the State of Texas. It still remains one of the most important oil-and-gas-producing areas of the United States, since it includes within its boundaries the large East Texas field. Other fields of importance are: Van, Rodessa, Talco, Cayuga, Long Lake and Sulphur Bluff. Production is from the Nacatoch, Blossom, and Woodbine of the upper Cretaceous and the Paluxy and Glen Rose of the lower Cretaceous. Of these, the Woodbine is the most important, since it is the producing horizon iri the East Texas field. Fields East Texas Field.—There were 2471 oil wells, 1 gas well and 84 failures completed during the year of 1936 in the East Texas field; that is, 1565 fewer than in the year of 1935. The total number of producing wells is now 22,031, of which 50 are temporarily shut down; 18,435 wells flowing their production; 3150 pumping; 293 on gas-lift, and 82 operated by other methods. This shows an increase of 1642 wells on artificial lift over Jan. 1, 1935. The average daily salt-water production is estimated at 42,700 bbl. from 2327 wells—an increase of 1201 wells over the year of 1935. The field is now drilled to an average density of one well to 5.85 acres. Average bottom-hole pressure has dropped from 1193 Ib. to 1168 lb., approximately 1 lb. drop for each 6,600,000 bbl. of oil produced. During the month of December 1936, the estimated daily average production of illegal oil had dropped from 20,500 bbl. in December 1935 to 7500 bbl. The commercial gas production is of minor importance in the East Texas field, and figures for the amount of gas taken from the field are not available at the present time. Talco Field, Titus and Franklin Counties.—The discovery well was drilled by Housh, Thompson et al. on the C. M. Carr tract and completed in March 1936, as a pumping well making 552 bbl. per day of 24&apos; gravity oil. This well was first completed at a total depth of 4208 ft., the top of the sand being 4190 ft. Later it was deepened to 4260 ft., which increased the production from 552 to 725 bbl. per day. This field is producing

Jan 1, 1937

INTRODUCTION The after-tax rate of return that properly discounts future cash flows is usually referred to as the "discounted cash flow-rate of return" (DCF-ROR). The method is also referred to as the internal rate of return, true rate of return, and investor&apos;s rate of return in some literature. According to Stermole (1974, p. 188) industry polls indicate that the DCF- ROR method is the number one economic evaluation decision method used by more than 90% of the industrial companies that use for- mal economic evaluation procedures. Other economic evaluation methods that have been used in the past, such as payback period, accounting ROR, etc., have largely given way to DCF-ROR analysis because they fail to account properly for the time value of money. DCF-ROR is generally defined as that rate of return that makes the present worth of future generated cash flow over the life of the project (including after tax salvage value) equal to the present worth of all after-tax investments. The "present worthing" of future cash flow involves discounting future cash flow to a present value according to the mathematics of compound interest at some interest rate. The determination of the interest rate that equates the present worth of future after-tax earnings with the present worth of all after-tax investments necessary to create such earnings is properly called the discounted cash flow rate of return analysis. Although present worth calculations are usually used for determining the DCF-ROR, the same results can be obtained by comparing income and costs of any equivalent point in time, i.e., future worth, etc.

Jan 1, 1980

By Frederick T. Fischer

INTRODUCTION Post-Lower Ordovician karstification on a continental scale produced a wide-spread paleoaquifer in the upper portion of the Knox Group of the Southeastern United States. The presence of economic zinc deposits in the Knox of Tennessee is considered to be a con- sequence of this paleoaquifer(1). During The New Jersey Zinc Company&apos;s initial exploration of the middle Tennessee region the known artesian nature of modern Knox water and its potentially adverse effect upon mining activities was a matter of concern. This concern intensified as a mining situation appeared imminent and a program of hydrologic investigation was begun in early 1969 and continued through August 1972. The preliminary findings of this work were reported at the AIME World Symposium on Mining and Metallurgy of Lead & Zinc in 1970(2). This paper presents additional data acquired during subsequent stages of the program and relates the hydrologic relationships to the overall geologic framework of the area. PHYSICAL GEOGRAPHY The Elmwood mine is 85km east of Nashville and 8km southeast of Carthage in Smith County, Tennessee (Figure 1). Its physiographic location is in the Central Basin of Tennessee, a basin resulting from erosional breaching across the Nashville Dome of the Mississippian strata which now form the bordering Highland Rims. Both the Central Basin and Highland Rims are divisions of the Interior Low- lands Province. Outcropping rock units of the Central Basin are predominantly Middle Ordovician limestones with scattered high hilltops capped by Devonian and Mississippian strata. One outlier

Jan 1, 1977

By E. C. Skinner

Cardox, which consists essentially of a steel tube containing carbon dioxide compressed to the liquid state, is a trade name designating a device used principally in coal mines to break down coal. The use of Cardox to break down coal was developed in the Middle Western coal fields around 1927 or 1928. At first, a large, heavy tube was used, requiring many parts. Through experimentation and technologic improvement, the weight of the tube has been brought down from 88 lb. to 20 lb. and the new, light tube makes use of larger volumes of CO2 at lower pressures than formerly was thought possible. This blasting method is extensively used today in coal mines and probably one tenth of the bituminous coal produced in the United States is prepared with Cardox. Construction and Application As used in the coal mine, Cardox looks like a piece of steel pipe 2 to 3 in. in diameter and 3 to 5 ft. long. When it is necessary to fire a shot, the tube is wired with two leg wires that are long enough so that when the tube is pushed the desired distance into the hole the wires will protrude 5 to 6 in. It has been found that No. 18 insulated copper annunciator wire is the best material for leg wires. A two-conductor rubber-covered shot-firing cable of sufficient length is then attached to the leg wires. A 2 to 6-volt current is applied, either by means of shot-firing batteries or the standard type of shot-firing generator. Upon the application of the current, the charge in the cartridge is set off. Because the breaking action upon the coal is supplied by the relatively slow physical expansion of the carbon dioxide gas rather than by the rapid chemical formation of gases as in more familiar explosives, the result is a slow heaving action, somewhat similar to that produced by black powder, rather than a shap detonating effect. Permissible powder does its work at roughly ten times the pressures in use with Cardox. The escaped gas from a Cardox shot apparently works along the planes of weakness in the coal face, such as the coal cleats, the edges of the cut, and along the top of the seam, breaking off the coal toward the free faces and heaving the mass of coal outward. Cardox tubes are manufactured in various sizes to take care of variable conditions of seam size, undercut depth, cleatage, coal hardness, and so forth. The tubes range in diameter from 2 to 3 in. (Table I) and the normal CO2 charge is from 24 to 96 oz. For any one tube size, several sizes of shear disks are available, thus excellent control of the type of shooting desired is possible. In general, local experience and experimentation dictate the size of tube chosen for any particular job. For high coal, and deeper or wider cuts, a larger size is chosen to start with, and the opposite is true for low coal, softer coal, or small cuts. After the tube size has been experimentally selected, tests are run in the mine to determine how many shot holes are needed and where the holes should be placed. The size of the disk,

Jan 1, 1944

By E. C. Skinner

Cardox, which consists essentially of a steel tube containing carbon dioxide compressed to the liquid state, is a trade name designating a device used principally in coal mines to break down coal. The use of Cardox to break down coal was developed in the Middle Western coal fields around 1927 or 1928. At first, a large, heavy tube was used, requiring many parts. Through experimentation and technologic improvement, the weight of the tube has been brought down from 88 lb. to 20 lb. and the new, light tube makes use of larger volumes of CO2 at lower pressures than formerly was thought possible. This blasting method is extensively used today in coal mines and probably one tenth of the bituminous coal produced in the United States is prepared with Cardox. Construction and Application As used in the coal mine, Cardox looks like a piece of steel pipe 2 to 3 in. in diameter and 3 to 5 ft. long. When it is necessary to fire a shot, the tube is wired with two leg wires that are long enough so that when the tube is pushed the desired distance into the hole the wires will protrude 5 to 6 in. It has been found that No. 18 insulated copper annunciator wire is the best material for leg wires. A two-conductor rubber-covered shot-firing cable of sufficient length is then attached to the leg wires. A 2 to 6-volt current is applied, either by means of shot-firing batteries or the standard type of shot-firing generator. Upon the application of the current, the charge in the cartridge is set off. Because the breaking action upon the coal is supplied by the relatively slow physical expansion of the carbon dioxide gas rather than by the rapid chemical formation of gases as in more familiar explosives, the result is a slow heaving action, somewhat similar to that produced by black powder, rather than a shap detonating effect. Permissible powder does its work at roughly ten times the pressures in use with Cardox. The escaped gas from a Cardox shot apparently works along the planes of weakness in the coal face, such as the coal cleats, the edges of the cut, and along the top of the seam, breaking off the coal toward the free faces and heaving the mass of coal outward. Cardox tubes are manufactured in various sizes to take care of variable conditions of seam size, undercut depth, cleatage, coal hardness, and so forth. The tubes range in diameter from 2 to 3 in. (Table I) and the normal CO2 charge is from 24 to 96 oz. For any one tube size, several sizes of shear disks are available, thus excellent control of the type of shooting desired is possible. In general, local experience and experimentation dictate the size of tube chosen for any particular job. For high coal, and deeper or wider cuts, a larger size is chosen to start with, and the opposite is true for low coal, softer coal, or small cuts. After the tube size has been experimentally selected, tests are run in the mine to determine how many shot holes are needed and where the holes should be placed. The size of the disk,

Jan 1, 1944