copi £>[£ Preliminary Report ON Organization and Method OF v» Investigations ILLSNOIS STATE GEOLOGICAL SURVfc U R B A N A 1I5RARY University of Illinois 19 13 c ILLINOIS COAL MINING INVESTIGATIONS CO-OPERATIVE AGREEMENT State Geological Survey Department of Mining Engineering, University of Illinois U. S. Bureau of Mines The Forty-seventh General Assembly of the State of Illinois, with a view of conserving the lives of the mine workers and the mineral resources of the State, authorized an investigation of the coal resources and mining practices of Illinois by the Department of Mining Engineer- ing of the University of Illinois and the State Geological Survey in co- operation with the United States Bureau of Mines. A cooperative agree- ment was approved by the Secretary of the Interior and by representa- tives of the State of Illinois. The direction of this investigation is vested in the director of the United States Bureau of Mines, the director of the State Geological Survey, and the head of the Department of Mining Engineering, Uni- versity of Illinois. The reports of the investigation are printed in the form of bulletins. For copies of these bulletins or any information regarding the work, address "Coal Mining Investigations, University of Illinois, Urbana, Illinois." ILLINOIS STATE GEOLOGIC Al_ SI -VE-jT 3 3051 00006 3812 ILLINOIS COAL MINING INVESTIGATIONS CO-OPERATIVE AGREEMENT State Geological Survey Department of Mining Engineering, University of Illinois U. S. Bureau of Mines PRELIMINARY REPORT ON ORGANIZATION AND METHOD OF INVESTIGATIONS ILLINOIS STATE GEOLOGICAL SURVEY LIBRARY Springfield, III. Illinois State Journal Co., State Printers CONTENTS. Page . Introduction 5 Personnel of the investigation 8 Method of conducting the investigation 10 Study of geological features 25 1. Coal resources of Illinois 25 2. Scope of new work on geology of the coal fields 26 3. Chemical quality of Illinois coals 26 4. Utilization of clay materials of coal mines 28 5. Safeguards of gas wells and oil wells in the coal fields 2S Study of the mining methods 30 1. Systems of mining 30 2. Blasting and explosives 31 3. Timbering 31 4. Haulage 33 5. Hoisting 33 6. Ventilation and mine gases 35 7. Mine stoppings 35 8. Humidity of mine air 36 9. Coal dust 43 10. Machine cuttings 46 11. Preparation of coal for market 47 Appendix "A" 48 Geology of the Illinois coal fields 48 Introduction 4S The coal-bearing area 4S The coal-bearing formations 48 Pottsville 49 Carbondale 49 McLeansboro 50 The spoon-shaped structural basin 50 Mining centers and districts 51 Chemical character of Illinois coals 56 Appendix "B" 59 Illinois mining systems 59 Room-and-pillar 59 Unmodified 59 Panel system 61 Longwall 63 Stripping 64 Appendix "C" 67 Equipment of coal dust laboratory at Urbana, Illinois 67 Description of apparatus 67 Operation of apparatus 70 ILLUSTRATIONS. F t gs. Page . 1. Diagram showing coal production at intervals of ten years 6 2. Map showing mines selected for cooperative investigation 11 3. Coal grinder for mine sampling 27 4. Riffle for reducing mine samples 27 5. Sketch showing arrangement of shots in coal face 31 6. Sketch of typical room showing location of timber ; 32 7. Tonnage and percentage of coal hauled by different methods 33 8. Mine-air sample report card 34 9. Approximate coal areas (Bement) showing U. S. Weather Bureau hygrograph stations and mines at which hygrometers have been installed 38 10. Hygrometer and hygrometer shelter 40 11. ) 12. } Diagrams showing moisture in air-current in summer, winter, and spring 42 13. j 14. Curves showing relative explosibility of coal-dusts 45 15. Map showing coal-measures area in Illinois 48 16. Map showing production of coal, calendar year of 1911 50 17. Plan of room-and-pillar mine 60 18. Plan of panel mine 62 19. Plan of longwall mine 64 20. Stripping-mine thorough-cut 65 21. Stripping-mine haulage way 65 22. Stripping-mine coal face 66 23. Stripping-mine second cut 66 24. Coal-dust laboratory, University of Illinois 67 25. Explosibility apparatus in dust laboratory 68 26. Detail of dust explosibility apparatus 69 ORGANIZATION AND METHOD OF INVESTI- GATIONS. INTRODUCTION. Illinois lias long been an important contributor to the coal production of the country. The first record of coal in the United States is con- tained in the journal of the Jesuit Missionary, Father Hennepin, who as early as 1679 reported a "cole" mine on the Illinois River near the present city of Ottawa. The recorded output to the close of 1911 approximates 850 million tons, a record surpassed in this country only by Pennsylvania. The increase in production, practically doubling each ten-year period (fig. 1), is but parallel to that generally experienced elsewhere. It emphasizes the need for the fullest possible knowledge of the coal re- sources themselves, and also of the practices that will make coal mining as safe and as profitable as possible for all affected by the industry. Mining is co-important with agriculture, both being indispensable to modern life and commercial development. In the calendar year, 1911, the coal mines in Illinois produced 53,679,118 tons, and employed 77,000 workmen. Under the practice which has developed naturally, in response to competitive conditions, possibly 50 per cent of the coal in the ground has been lost, and a large part of the mined portion wasted by its improper or inefficient use. Moreover, 2 to 3 lives have been lost annually for every 1,000 miners employed, or 3 to 4 for each million tons produced, and the number of serious injuries has been even greater. This condition is due to the rapid expansion of the coal mining industry, and the condition under which such mining is carried on in the United States. Mining is, however, but one of the industries in which such records have been made. It is believed that more efficient mining methods will save a large por- tion of the coal resources of the State, cut down the present rate of deaths and accidents, and make for safer mining investments. With these matters in mind, the Forty-seventh General Assembly of Illinois and the Secretary of the Department of the Interior authorized an investigation of coal mining under a cooperative agreement between the State Geological Survey, the Mining Department of the University o 10 o C/3 z o 3 S j S c ■"* C/3 55 C _ H oi O I C/J o 1 ... . ■■_, . ■ 1 1 So g 8 o o o_ o" O 0! § s 1,552 9,118 CM CO CO 8 CM Cf CO ccT >/ r^.' eo~ « CM LO a: ^^ . ^ _ < LO CO r^ oo o 5 O r- >- 00 oo oo oo a > Ci O ** *"" ' * H ~ « INTRODUCTION. 7 of Illinois, and the United States Bureau of Mines. The work began in the summer of 1911, each cooperating party furnishing trained specialists for particular phases of the investigation. Before the work was planned and in order to obtain the view-point of those connected with the coal mining interests in Illinois, a number of conferences were held with the State Mining Board, the State mine inspectors, the several organizations of coal operators, and with the officials of the United Mine Workers. Many suggestions were received from each of these organizations that were of great assistance in select- ing typical mines, and in planning and carrying out the work. The United States Weather Bureau, has heartily cooperated with the Mining Investigation as is described later in this bulletin. The co- operation has made it possible to gather very complete information upon the atmospheric conditions in Illinois as they affect the ventilation of mines and coal-dust dangers. The object of this first report is to outline the organization, scope and methods of work, and to suggest the nature of results to be expected. Separate reports will present the results obtained in each district by the geologists, engineers, and chemists. This series, together with reports on special subjects and summaries for the whole State, will define the extent and character of Illinois coal beds ; furnish a comprehensive description of methods of mining; and supply much new information on important mining problems. COAL MINING INVESTIGATIONS. PERSONNEL OF THE INVESTIGATION. U. S. BUREAU OF MINES J. A. Holmes, Director, Washington, D. C. R. Y. Williams, Mining Engineer, Urbana, 111. J. J. Rutledge, Mining Engineer, Urbana, 111. A. C. Fieldner, Chemist, Pittsburgh, Pa. N. H. Darton, Geologist, Urbana, 111. L. A. Scholl, jr., Junior Chemist, Urbana, 111. J. M. Webb, Foreman Miner, Urbana, 111. In Consultation — George S. Rice, Chief Mining Engineer, Pittsburgh, Pa. J. K. Clement, Physicist, Pittsburgh, Pa. ILLINOIS STATE GEOLOGICAL SURVEY F. W. DeWolf, Director F. H. Kay, Assistant State Geologist K. D. White, Assistant Geologist Prof. S. W. Parr, Consulting Chemist J. M. Lindgren, Chemist Analysts — F. H. Whittum S. C. Taylor J. F. Kohout G. Simpson C. W. Sievert L. T. Fairhall DEPARTMENT OF MINING ENGINEERING, UNIVERSITY OF ILLINOIS Prof. H. H. Stoek, Head of Department of Mining Engineering S. 0. Andros, Mining Engineer C. M. Young, Mining Engineer H. H. Lauer, Mining Engineer C. W. Porter, Laboratory Assistant PERSONNEL Samplers — C. W. Smith M. L. Nebel S. T. Wallage H. L. Stafford J. E. McDonald 10 COAL MINING INVESTIGATIONS. METHOD OF CONDUCTING THE INVESTIGATION. The work of the cooperative investigation is intended to be constructive as well as statistical. It is necessary that it be prefaced and based npon accurate information and that all existing conditions be carefully con- sidered if the results are to be of benefit to the coal industry of Illinois. Deductions from these investigations should aid the operators and miners of the State to produce coal more safely, more cheaply, and less wastefully. In Illinois, according to the report of the State Mining Board for the year ending June 30, 1911, there are 845 mines. Of this number, 387 are shipping mines and 458 are non-shipping mines, commonly known as country banks. The size of the mines is approximately shown by Table 1. Table 1. — Tonnage of mines for 1911 Under 1,000. 1,000 and under 10,000. 10, 000 and under 50,000. 50, 000 and under 100,000. 100,000 and under 200,000. 200,000 and over. Total mines. 235 213 138 82 101 76 845 For the purposes of this investigation the State has been divided into nine districts as shown in Table 2, and mines working the same bed under similar conditions have been grouped together. A few scattered mines which have not been included in any of these groups are so similar to the mines in nearby districts as not to require special examination. One hundred typical mines as shown in fig. 2 have been chosen for examination; i. e., about one-quarter of the shipping mines. Any gen- eralization based upon so large a proportion of the mines should be applicable to all of the mines of the State. Fig. 2. Mines selected for cooperative investigation. 12 COAL MINING INVESTIGATIONS. Table 2. — Districts into which the State has been divided for the purpose of investigation In- ves- ti- ga- tion dis- trict. Coal bed. Method of mining. Counties. Inves- tigation numbers for mines examined. I No. 2 Longwall Bureau, LaSalle, Grundy, Will, Putnam, No. 2 Room-and-pillar. . . Room-and-pillar. . . Room-and-pillar. . . Room-and-pillar. . . Room-and-pillar. . . Room-and pillar. . . Room-and-pillar. . . 1 to 11 II Jackson Rock Island, Mercer, Warren, McDo- nough, Fulton, Schuyler, Brown, Scott, Green, Calhoun, Henry, Jersey, Han- 12 to 16 III Nos. 1 and 2 No. 5 (Central) .... No. 5 (Southern)... No. 6 (East of Du- Quoin anticline). No. 6 (West of Du- Quoin anticline). Nos. 6 and 7 (Dan- ville district) Nos. 2 and 5 (Work- ing two seams) . . 17 to 24 IV Peoria, Fulton, Tazewell, Logan, Menard, 25 to 42 V Saline, Gallatin 43 to 49 VI VII VIII JelTerson, Perry, Jackson, Franklin, Wil- liamson Sangamon, Christian, Moultrie, Shelby, Macoupin, Montgomery, Madison, Bond, St. Clair, Clinton, Marion, Wash- ington, Perry, Randolph, Henry 50 to 65 66 to 90 91 to 97 IX Bureau, LaSalle, Livingston, McLean 10, 98, 99, 100. For convenience in reference an alphabetical arrangement by counties is given in Table 3. Table 3. — Alphabetical arrangement of counties County Coal bed District 6 VII 1, 2 III 2 I, IX 1, 2 III 1. 2, 6 III, VII 6 VII 6 VIII 6 VI 1, 2, III, IV 5 V 1, 2 III 2 I 1, 2 III L 2, 6 III, VII 2, 5 II, VI 6 VI 1, 2 III 2 I, IX 2 IX 5 IV 5 IV 6 VII 6 VII 6 VII 1 2 I County Coal bed District Bond Brown Bureau Calhoun . . . Christian.. Clinton Edgar Franklin. . . Fulton Gallatin . . . Greene Grundy Hancock . . . Henry Jackson Jefferson . . . Jersey LaSalle Livingston. Logan Macon Macoupin . . Madison . . . Marion Marshall . . . McDonough. McLean Menard Mercer Montgomery . Moultrie Peoria Perry Putnam Randolph . . . Rock Island. St. Clair Saline Sangamon... Schuyler Scott Shelby Stark Tazewell Vermilion . . . Warren Washington . Woodford Will Williamson . . I* 2 2 5 li 2 6 6 2 5, 6 2 6 1, 2 6 5 2, 5 1, 2 1, 2 6 2 5 6 li 2 6 2 2 III IX IV III VII VII IX VI, VII I VII III VII V IV, VII III III VII I IV VIII III VII I I VI The collection of the general information at each mine has been accom- plished with the aid of the following series of field notes. METHODS OF INVESTIGATION. 13 COAL MINING INVESTIGATION Cooperative Agreement Operator Date Ccal Bed Address Supt Address Mine Mgr R . R Cap. per Day tons. Aver, per Day tons. Tipple: Steel or wood. Cage: Type Size Loading Tracks: No Cap Hoist. Eng.: Mfg Size Kind Drum: Diam Length Boilers: Type No Total H. P Av. Steam Press Elec. Generator: K. W D. C— A. C. Volt Compressors: No Size Press Fan: Type Diam Width How Driven Blowing, Exhaust, Water-gage Magazine: Const Dist. from nearest bldg Surface Plant: Plan Const Surf, fire protec Hoist, shaft: Depth Size No. Compts Lining Cost of sinking Air shaft: Depth Size No. Compts Lining Cost of sinking No. employees: Surf Underground Nationality: Ownership: Surface, leased Fee Coal, leased Fee Acreage aband Under devel Unmined Life of mine: Past Future Improvements Underway Trade name of coal Market . . . Selling agts Fit. rates. Show on mine map land leased and held in fee. Town Mine Co. A.— SURFACE SHEET. Collector No. 14 COAL MINING INVESTIGATIONS. COAL MINING INVESTIGATION Cooperative Agreement Haulage System Cars: Wt Cap Ties: Kind of wood Size -Rail wt.: Entry Room Track gage System of mining Entry width: Main Cross Room Entry length: Main Cross Room Coal recov. %: 1st Working Drawing pillars Total Time of drawing pillars: Room Entry Sketch method Entry pillar width: Main Cross Room Barrier pillar width: Main Cross Rooms: No Width Length Coal cutters: Type Mfg Cut Does coal stick to roof? Does immediate roof fall in rooms? Do pieces get loaded with coal? Floor: Soft, hard, smooth, rough? Does coal stick to floor? Do pieces get loaded with coal? Gas: Found in— roof , coal, floor, rooms, entries Quantity Max. in ret Section. Ft. No. Desc. In. .Max. Min. Coal seam, Thick: Av Vert. ht. to nearest workable coal Vert, depth to nearest workable coal Dip Direction Cleat Direction Detailed description of physical properties and variability of roof and floor materials and coal peculiarities Collector B.— UNDERGROUND SHEET. Nameofseam No. METHODS OF INVESTIGATION. 15 COAL MINING INVESTIGATION Cooperative Agreement Mine water: Gals, per min Pump driven by. Charac. of water Occurrence: At faces At shaft At special sections Humidifying: Where and how: Cars: How often Gals, per 24 hrs. . . . Hose: How often Gals, per 24 hrs. . . . Sprays: How often Gals, per 24 hrs. . . . Dist. between sprays Dist. wet from face Exhaust steam: Method Effect: On roof On men Calcium chloride: How applied Shale dust: How applied Where obtained Results Is present method considered efficient? Expense of installation . Expense to maintain. Place. Time. Dry B. Wet B. Barom. Quant. Air Surface on entering Surface on exit Station Station Station Station Collector C— HUMIDITY SHEET. 16 COAL MINING INVESTIGATIONS. COAL MINING INVESTIGATION Cooperative Agreement Entry timbers: Life. . . Sketch, Preservatives: Kind Cost How applied Treated timber: Cost Life Untreated timber: Cost Life Steel timbers: Cost to install Cost to maintain Room Props.: Length Cross Section . . First cost Life No. per 100 sq. ft. of room Per ton of coal Size of < caps. Accidents from falls of roof: No. fatal in years. No. non-fatal in yea r s. Sketch typical room: Show length, width, positions oi track, props, amount of gob, distance from nearest row of props to room face. Collector D.— TIMBERING SHEET. No. METHODS OF INVESTIGATION. 17 COAL MINING INVESTIGATION C coper ative Agreement Explosives: Kind Size Lbs. per charge Lbs. per ton of coal Cost per ton of coal Tamping material: Kind Furnished to miners? Where obtained? Holes: Length Diam Tamping bar Needle How fired: Squib, fuse, fuse and cap, electric detonators How stored How thawed. How delivered: To mines. To miners. Hydraulic device: Name, description and results. Results of blasting: Frequency of windy shot s Of blown-out shots Of mine fires Per cent of lump coal Effects of blasting on roof Accidents from blasting: No. fatal in years No. non-fatal in years Shot-firers: No Holes per man Fire runners: No Sketch blasting method: Show position, length .inclination of holes. Givefronl and side elev. and plan Collector E.— BLASTING SHEET. No -2 M I 18 COAL MINING INVESTIGATIONS. COAL MINING INVESTIGATION Cooperative Agreement 1. Assigned cause of fire 2. Acreage affected 3. Amount of coal lost 4. Method of fire fighting 5. Kind and effectiveness of seals 6. Cost of fire sealing Collector F.— MINE FIRE SHEET. No. METHODS OF INVESTIGATION. 19 COAL MINING INVESTIGATION COOPEKATIVE AGBEEMENT Acreage affected Coal lost: Amount % Overburden: Ht Wt. per sq. ft Nature Cost of checking squeeze Coal extracted previous to squeeze Correlate on map any surface cracks with workings Sketch method of checking squeeze, showing walls, cogs, surrounding pillars of coal. Describe any special features Collector G.— MINE SQUEEZE SHEET. 20 COAL MINING INVESTIGATIONS. COAL MINING INVESTIGATION Cooperative Agreement Run of mine shipped:^Per cent Price per ton Sizes ' ' ' ' Names ' ' ' ' ' Per cent ' ' ' Screen ' ' ' ' ' Bar, Length, Inc! ° Space Width Size. Shaker: Length Incl .. .° Width Shakes per min Sizes of holes Revolving: Length Incl ° R. P. M Diam Holes: Shape Sizes Picked: On chute, belt, car No. pickers ' Crusher: Type Size Cap Washery : Type Builder Cap • A v. daily tonnage Unwashed storage cap Coal screened when Hydraulic classifiers: No No. compt Dimen Sizes of products Coarse coal jigs: No Cap Strokes per min. Fine coal jigs: No Cap Strokes per min. Cone washers: No Dimen Storage cap Car loaders Refuse disposal Weighing devices Cost of preparation Collector H.— PREPARATION SHEET. No METHODS OF INVESTIGATION. 21 COAL MINING INVESTIGATION Cooperative Agreement Operator Date 191 Mine Located Miles* fromf Location in mine Total (vertical) depth from surface at point of sampling ft In describing the beds and character of the members, note any member that is rejected by the miner Note all clay and sulphur partings, whatever their thickness. Exclude from sample all clay and sulphur partings j{ inch thick or over (and even those of less thickness if they are rejected at mine or tipple). Section of Bed at Point Sampled. No. DESCRIPTION. Feet. Inches. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Total Is coal wet or dry? Time exposed hours. Weight gross . What are the impurities, and how do they occur? . . . .minutes. net What are shipped? What are excluded from the sample? ^Direction (N., NE., etc.). Coal bed fNeareal railway station. Town Mine. Sample No Can No I.— COAL SAMPLE SHEET. Sampler... .Co. .No. 22 COAL MINING INVESTIGATIONS. COAL MINING INVESTIGATION Cooperative Agreement Mine Name or No. mile.. Operator. 191 Operator, 191 ft (above. I below . .T T. Sec. Entrance Elev L ueiuw — Depth to bottom coal ft Alt R. R. Surface Data A. Topography See . B. Superficial materials (1) Character (2) Thickness (3) EfTeet'onjnining and shaft-sinking, of former drain- age lines, underground water strata, etc .See. .See. C. Outcrops (1) Character (2) Structure (3) Fossil horizons See . Collection No (4) Evidences of subsidence See . D. Note collection of mine maps, drill records and shaft logs See drill record sheet. E. Notes on surrounding area. See. Coal bed name: Local Collector Mine L.— SURFACE SHEET (Geol.). .Co. .Survey ...State No. .Coop. No. . METHODS OF INVESTIGATION". 23 Underground Data F. Thickness of rock above bed worked. (1) Important variations G. Note pras3nce of strata having important effect on mining. .See.. ...See. (1) Position (2) Character (3) Persistence (4) Other workable coal beds. H. Cap rock (1) Thickness (2) Height above coal . I. Immediate roof. (1) Thickness.. .....See.. (2) Contact with coal (3) Horizontal variation . J. Draw slate. (1) Thickness. See. .(2) Contacts . (3) Persistence. K. Coal bed: Max Min Av inches (1) Benches (a) Position (b) Persistence. See. (2) Bedded impurities, kind, position in benches, persist- ence, ease of separation See. (3) Irregularities in continuity of bed (due to deposition, erosion, or movement) . See . (a) EiTect on mining. . See . .See. Collector . Mine .Coal. SECTION. Ft. In. Name Index Sym. State No. .Co Coop. No. M.— UNDERGROUND SHEET (Geol.). 24 COAL MINING INVESTIGATIONS. Underground Data (cont'd.) K. (5) Physical character of coal in benches . (a) Relative hardness ( b) Lustre (c) Fracture (d) Texture See . (6) Impurities in coal, other than bedded (a) Kind (b) Position and persistence (c) Rejected Ease of separation , See. L. Floor: (1) Material (2) Thickness (3) Variation (4) Note character, condition, tendency to heave, relation to undercutting, commercial value See. (5) Clay sample No Location M. Stratigraphy (1) Fossiliferous horizons underground. Collection No '. Location . N. Notes on effect of deep drilling in coal mine areas . .See. Collector Coal | | State No. Mine Co Coop. No. . N.— UNDERGROUND SHEET (Geol.). GEOLOGICAL STUDIES. 25 STUDY OF GEOLOGICAL FEATURES. 1. COAL RESOURCES OF ILLINOIS The area underlain in Illinois by coal-bearing formations approximates 36,800 square miles, but this is only indirectly an index to the amount of coal available under existing commercial conditions, for coal must be thick enough and of good enough quality to permit profit in recovery, or it will not be mined. The production of Illinois mines in the calendar year 1911, according to statistics compiled jointly by the State Geological Survey and the U. S. Geological Survey, amounted to 53,679,118 tons valued at $59,- 519,478. The tonnage exceeds that of 1910 by 7,778,872 tons or 16.9 per cent. The phenomenal increase in production, shown in fig. 1, gives rise to conjecture as to the total coal remaining and the number of years that it will sustain the increasing commercial and domestic needs. The first Illinois Geological Survey under Dr. A. H. Worthen deter- mined that there were 16 different coal beds, and numbered them in order beginning with the lowest. It is now clear that coal exists at many additional horizons in the Pennsylvanian series, but that the extent and thickness of the beds is probably unsatisfactory except in the case of a very limited number. Calculations by Bement 1 for 1909 (fiscal year) indicated that, of the total output, Coal Xo. 6 (Herrin, Belleville, etc.) produced 59 per cent, Coal Xo. 5 (Springfield, Earrisburg, etc.) yielded 25 per cent, and Coal No. 2 (La Salle, Third Vein, Wilmington, etc.) produced 12 percent. The small remainder. 4 per cent, was mined from No. 7 (Danville), No. 1 (Rock Island), and scattering Beams. It is clear that only Nos. 6, 5, 2, 7, and 1 are important producers at present, and that the bulk of production is likely to come more and more from the two beds first mentioned. It will doubtless require many years and many changes in competitive relations or in state supervision before we shall extensively mine coals as thin as 24 inches, after the present manner of some foreign countries. Assuming, however, that such thin coals should be included in estimates of future reserves the State Geological Survey in L908 calculated that the total remaining coal was approximately 136 billion tons. An estimate by the U. S. Geological Survey based on coals 20 inches or more in thickness amounted to 240 billion tons. Bement calculated, in 1909, on the basis of coals measuring 12 inches or more, that there was approxi- mately 201 billion tons. The State Geological Survey has now re-calcu- lated the probable reserves and is disposed to think that there may be 200 billion tons exceeding two feet in thickness. » Bement, A. Bull. Illinois State Geol. Survey, No. 14, p. 186, 1910. 26 COAL MINING INVESTIGATIONS. 2. SCOPE OF XEW WOEK OX GEOLOGY OF THE COAL FIELDS The work of the Geological Survey under the cooperative investigation has been devoted principally to the careful examination of surface and underground geology at each of the one hundred mines selected as typical. The objects of this work have been : To secure all available information regarding the coal resources of the State ; To continue the investigations of the character and quality of Illinois coal, as shown by analysis; To determine the commercial availability of clay materials in typical coal mines; To investigate the problem of safeguarding coal properties from danger- ous gas, oil, and water borings. The special studies on the surface involved the effect of topography and of surface materials, such as clay, quicksand, etc., on shaft-sinking and on surface subsistence due to mining. Another phase of the work has been the collection of all new drill records that could be secured, and the study of these together With several thousand already in the Survey files. Many of the latter had been collected in cooperation with the IT. S. Geological Survey in 1908. The underground studies related to a number of definite problems including : Position, character, and extent of cap-rock, and other roof materials af- fecting mining operations; Character of floor materials as affecting undercutting of coal, and mine-squeeze; Distribution and character of iron pyrites (sulphur), bone, clay bands, and other impurities in the coal beds; Character and probable extent of faults, rolls, clay veins, and erosion areas in the coal beds. The schedules "L," "M," and "X" (pp. 22-24) were used in collection of routine information and were supplemented by additional notes. 3. CHEMICAL QUALITY OF ILLINOIS COALS Since the character of a coal determines its possible uses, there has been a growing public interest in learning the characteristics of Illinois coal, and all the various uses to which it is especially adapted. , Since 190G the Geological Survey has published bulletins 3, 4, 8, 14, and 16 which relate, in part at least, to studies of the subject made by the Survey in cooperation with the Department of Applied Chemistry and the Engineering Experiment Station at the University of Illinois. , In connection with the cooperative investigation practically all of the 100 mines selected, and a small additional number, were sampled. accord- ing to new standards, as stated below : A fresh face which represented average conditions, as nearly as possible, was cleaned by taking off a layer of 2 or 3 inches, after which all loose pieces were removed from the immediate roof. A large piece of oilcloth was then spread on the floor, and a, strip of coal amounting to at least five pounds to the foot was cut down from top to bottom. Any .bone, GEOLOGICAL STUDIES. 27 Fig. 3. Coal grinder for mine sampling 1 1 1 .5 <0 *>r:i- §^^P «■ Fig. 4. liiille for reducing mine samples 28 COAL MINING INVESTIGATIONS. blue-band, sulphur, or other impurity exceeding three-eighths inch in thickness was discarded, instead of next being quartered, as in some earlier collections, the entire sample was quickly ground to one-eighth inch size or smaller in a special grinder (fig. 3). The coal was then reduced repeatedly by means of a mechanical riffle (fig. 4) to a sample weighing 5 pounds, which was placed in an air-tight can. This method yielded results which were more free from accidental or personal error than any of our previous efforts. As a further improvement, samples were taken from three to six places in each mine, and duplicates were frequently sent to the laboratory of the U. S. Bureau of Mines, so results could be compared with those obtained at Urbana. The field notes were collected on coal sample sheet "I" (p. 21). The laboratory work Avas done in the laboratory of the University of Illinois, under direction of Prof. S. W. Parr, by J. M. Lindgren and assistants, previously listed. The analyses yielded valuable results regarding the accuracy of sam- pling and analytical methods, and supplied new data as to moisture, ash, calcium carbonate, volatile matter, fixed carbon, and calorific value of the coals. The first report by Professor Parr is nearly ready for publi- cation, and others will follow. 4. UTILIZATION OF CLAY MATERIALS OF COAL MINES The roof shales and the under-clays at many Illinois mines give promise of being usable in the manufacture of fireclay products, paving- blocks, or other clay wares. Already the clay materials at a few of the mines are so utilized. It seems probable that a large auxiliary industry can be created at many mines, where clay materials can be produced economically, and where fuel and transportation facilities are already at hand. As a part of the cooperative investigation the Geological Survey under- took to secure samples from about 30 promising mines which represent the various districts. The Ceramics Department at the University of Illinois is contributing a thorough test and report on the samples. 5. SAFEGUARDS OF GAS WELLS AND OIL WELLS IN THE COAL FIELDS There have been numerous instances throughout the country, in which gas, oil, and water from active and abandoned wells have been released in coal mines with disastrous results. Many states have legislated with a view of providing safeguards or restrictions so as to minimize the danger. Many if not all of the present laws are inadequate, and the subject is a live one throughout the country. GEOLOGICAL STUDIES. 29 As a part of the cooperative investigation the Geological Survey under- took to study the matter carefully and to recommend means of meeting the problem. Already a committee of the various State Geologists is at work, in cooperation with the U. S. Bureau of Mines, and representative coal and oil operators. As, early as possible a report with recommendations will be presented, and all states concerned will be urged to adopt uniform legislation on the subject. 30 COAL MINING INVESTIGATIONS. STUDY OF MINING METHODS. The conditions under which coal is mined in Illinois have been studied under the following headings : 1. Systems of mining 2. Blasting and explosives 3. Timbering 4. Haulage 5. Hoisting 6. Ventilation and mine gases 7. Mine stoppings 8. Humidity of mine air 9. Coal dust 10. Machine cuttings 11. Preparation of coal for market. 1. SYSTEMS OF MINING Since the topography of Illinois is as a rule flat, and the coal seams lie nearly horizontal, the coal in practically all the shipping mines is reached by shafts, the location of which is determined mainly by the shape of the properties and by the shipping facilities. The plan of underground development for any particular mine should be based on the careful consideration of such important factors as : Character, thickness, and weight of overburden Nature of roof and floor Inclination and thickness of the seam Physical character of the coal Presence and pressure of gas in the seam Danger of spontaneous combustion, etc. Failure to consider these factors and the desire for an immediate return on the investment, have often resulted in the abandonment of large areas in many mines because of squeezes, fires, etc. ; lives have been lost; and heavy expense has been incurred in the attempt to repair the damages. One of the objects, therefore, of the cooperative investigation has been to study the prevalent mining methods: room-and-pillar (and its modifi- cation known as the panel system), long wall, and stripping, in order to compare the practice under different conditions in the mines of the State and to note such modifications of each method as make the mining successful. Data on systems of mining as shown on field-note sheets "A," "B," "D," and "E" (pages 13, 14, 16 and 17) have been collected from each of the 100 mines visited. MINING METHODS. 31 For information of readers who may not be familiar with the mining practice in Illinois there is given in Appendix "B" (p. ) a general description of the fundamental systems of mining which prevail. 2. BLASTING AND EXPLOSIVES According to the Illinois Coal Report for 1911, during the eleven years from 1901 to 1911 inclusive, 14.4 per cent of all fatal accidents have been due to blasting. Blasting has caused also a large number of explosions and mine fires. Nearly all of the accidents from explosions may be attributed to the careless or excessive use of powder. During 1910 and 1911 the number of fatal accidents from the use of explosives in Illinois was only 5.3 per cent of all the fatal accidents. Thus it appears that the average for the past eleven years as noted above is unnecessarily high and that the subject is worthy of careful study. The data that have been collected on blasting methods in Illinois may be seen by reference to the "E" sheet of the field notes (p. 17). At each mine visited, a general sketch was made of the method of placing the holes (fig. 5). Fig. 5. Sketch showing arrangement of shots in coal face In addition to the general information on the blasting methods, ;i special investigation has been made of the field use of "permissible explosives" and their adaptability to Illinois mining conditions. 3. TIMBERING Falls of roof and coal arc causes of 50 per cent of the total accidents in mines. One of the means of lessen ing them is the intelligent use of timber. Inasmuch as, good mine t milter is becoming more scarce and 32 COAL MINING INVESTIGATIONS. expensive every 3 r ear, the method of timbering adapted for any mine is an important item not only of mine safety but also of the operating expense. Fig. 6. Sketch of typicaljoom showing location of timber There are two main reasons for using timber in mines : to control roof subsidence during coal extraction, and, secondarily, to give miners warn- ing of approaching roof falls. Timbering methods in Illinois have been MINING METHODS. 33 studied with these facts in mind, and information has been obtained to show the relative merits of the various methods, and the manner in which the timber cost varies with the different dimensions of rooms and pillars. Data on the size, cost, and life of wood, steel, and concrete timbering- has been obtained as shown on the "D" sheet of the field notes (p. 16). Also, a sketch (fig. 6) has been made, which shows a typical room and the details of the timbering method in each mine visited. 4. HAULAGE Mine-car and mine-locomotive accidents caused over 17 per cent of the fatalities in Illinois mines during 1911. Because of this fact, and because good haulage roads are of prime importance in the economical operation of any mine, careful attention has been given to this subject by the Cooperative Investigation and data have been collected as shown on the "B" sheet of the field notes (p. 14). In 137 of. the 387 shipping mines there were used for haulage 300 electric and 3 gasoline locomotives. Mule haulage was used in "210 KIND of HAULAGE SHORT TONS 10 PERCENTAGE 20 30 40 50 GO LOCOMOTIVE MULE ROPE MAN 29.310.173 10,839,883 2.321.010 287.585 60.1 ■i 4.9 1 0.6 Fig. 7. Tonnage and percentage of coal hauled by different methods mines; rope haulage in 24 mines; and in 7 the cars were pushed to the bottom by men. Fig. 1 shows the number of tons and Die percentage of the total output of the State handled in each manner. .V HOISTING In most, of the shipping mines in Illinois the hoist ing-plant. is efficieni and capable of handling all the coal that can be brought to the shaft bottom. Self-dumping steel cages are in general use. The new law requires that the means of ingress and egress he protected against fire. Notes in regard to hoisting equipment were gathered as shown on sheet "A" and «B» (pp. 13 aml'l I). Since a number of accidents are reported every year as having been caused by bad hoist ing-practice or by defective machinery, the present investigation has obtained information regarding: type, size, and manu- -3 M I 34 COAL MINING INVESTIGATIONS. FORM NO. (A) MINE AIR SAMPLE 6—662 Rec'd, (Section Chief's Reference) Bottle No. Laboratory No. State, County, Township, S., T., R., Town (distance and direction from) Name of coal bed, ft. in. Mine, Carrier, Room, Entry, Location in same, Operator, Method of sampling, Velocity, Area, Quantity, Barometer: Inside, Outside, Corrected to sea level : Inside, Outside, Bulbs: Wet, Dry, Humidity, % Collector, Mailed, , 191 (B) MINE AIR SAMPLE (over) Rec'd, (Laboratory Record) Bottle No. Laboratory No. State, County, Township, S., T. R., Town (distance and direction from) Name of coal bed, ft. in. Mine, Carrier, Room, Entry, Location'in same, Operator, Method of sampling, Velocity, Area. Quantity, Barometer: Inside, Outside, Corrected to sea level : Inside, Outside, Bulbs: Wet, Dry, Humidity, % Collector, Mailed, , 191 (C) MINE AIR SAMPLE (Sample Receipt) Designation, Lab. No. Collector, Bottle No. Mailed, , 191 ; Received, ,191 Remarks : (Signed) Chief Chemist. To Mr. Address, Chem. Lab. No. Fig. 8. Mine-air sample report blank MINING METHODS. 35 facture of hoisting-engine; length and diameter of drum; type, number, total horse-power, and average steam pressure of boilers; methods of stoking; speed of hoisting; method of caging; type of signaling devices; kind of head-frame; depth, size, and lining of hoisting shaft; size, mate- rial, and life of guides ; type of cage, and use of safety-chains. 6. VENTILATION AND MINE GASES The causes of mine-air pollution are : respiration of men and animals ; gases from the use of explosives ; fumes from miners' lamps ; absorption of oxygen by coal and pyrites; exudation of gas from the seam; emana- tions from excrement; decay of timber ; coal dust from mining operations, etc. These factors often combine to impoverish mine air and render it injurious to the health of the miners. The problem of preventing excessive pollution of the air is, therefore, very important. The Cooperative Investigation lias collected data on the following phases of the subject of mine ventilation ; the fan installation ; the efficiency of the method used to conduct the air through the mine; and the quality and quantity of the air at the "face." The quality was determined by taking duplicate samples of the mine air for analysis in order to learn the kind and amount of impurities present. The informa- tion collected to accompany each sample is shown in fig. 8. A careful investigation of the occurrence of methane (marsh gas) has been carried on in southern Illinois where explosive gases are some- times found in large quantities. Air samples from most of the mines in that territory have been collected and the manner of occurrence of the gas noted. In 20 of these mines, holes 2 1 /' inches in diameter and L0 feet in length were bored in the solid coal. In these holes a half-inch galvanized iron pipe was placed so that its end extended three feel outside the rib. The hole was then tamped with fire clay. A pressure gage was attached to the projecting pipe and the pressures were read three times daily by the mine-manager. Samples of the borings were placed immediately in securely sealed cans and forwarded to the Pittsburgh laboratory, where at weekly intervals the gas emanations were drawn oil', measured for volume, and analyzed. A careful measurement was also made of the exposed coal in the workings and of the total amount of gas per 2 1 hours in the return. This relation was determined, for comparison, both in the new workings and the old workings of the mine. 7. MINE STOPPINGS 'Idic leakage of air through stoppings is no! only a possible source of danger to the safety of the mine, hut miay also be a heavy item of expense. Special inquiry has, therefore, been made into the cosl and efficiency of the stopping- nsc aj PP s s S ft p. a s 2 £ £ £ CM carry at that temperature. The relative humidity is thus indicated because the rate of evaporation at a given temperature, and consequently the amount of depression of the wet bulb thermometer, is dependent on the degree of saturation of 40 COAL MINING INVESTIGATIONS. STUDY OF MINE HUMIDITY. 41 aqueous vapor, or, as commonly expressed, on the amount of moisture carried by the air. When the difference in readings between the dry and the wet bulb is known, the relative humidity can he determined from prepared tables. 3 In order to protect the hygrometers from breakage in the mines, a shelter (fig. 10) was made of 24-gage galvanized-iron, consisting of two cylinders intersecting at a right angle. The horizontal cylinder is open al both ends, thus allowing a perfect circulation of air around the ther- mometer bulbs. 'Idic {'lids of the cylinder are protected by a screen of one-quarter inch mesh hardware-cloth. In the vertical cylinder there is a similarly protected opening to allow the thermometers to be read conveniently. The hygrometers are installed at points in the mine where there is a velocity of air of at least 15 feet per second, in order that the proper rate of evaporation of moisture from the muslin hag may he obtained. CALCULATING MOISTURE CONTENT OF MINE AIR From an average of the daily readings of the hygrometers there is obtained the relative humidity of the air entering the mine from the intake air-shaft and that of the air passing out through the return shaft. From the Psychrometric Tables there can be obtained for any given temperature and relative humidity, the weight of a cubic foot of aqueous vapor or, popularly, the weight of moisture contained in a cubic foot of air. At the place where each hygrometer is placed the velocity of the air- current is read with a standardized anemometer and the area of the air-course is measured to obtain the cubic feet per minute of ail' passing each hygrometer. Having obtained the amouni of air and the weight of moisture carried by it as it passes each hygrometer, it is simply a matter of multiplication to obtain the weight of water carried into the mine and out of the mine each 24 hours, and the number of gallon- of water carried by 100,000 cubic feet of the ventilating current. EXTRACTION AMI DEPOSITION OF MOISTURE I'.V THE VENTILATING CURRENT The action of the aii' in extracting or depositing moisture as the rea- sons change and as the temperature of the outside air and of the intake air-current vary is illustrated by the diagrams in figs. 11, L2, and 13, platted from actual readings in a mine. In fig. 11 "A" shows, in terms of gallons per 24 hours, the amount of moisture carried out of the mine for each working day of I he week beginning Monday, March 11, 1912, and "\>" the amount of moisture i Marvin, C. F., Psychrometric tables for obtaining the vapor pressure, relative humidity and temperature of the c'ew-poitii: Bull. U.S. Weather Bureau, No. 235! This bulletin may be obtained at a cost of 10 cents by applying t > the Director of the United states Weather Bureau, Washington, D. C. HON our TUESDAY WEDNESDAY THURSDAY FRIO AT SATURDAY 18.000 18,000 HETU w Air -CUR ft EHT 14.000 A ! * 10.000 5 S fe 8,000 3 6.000 '* r **c ^ _ , 4 000 B *~ 'get gfir; *' ^ ^ — " .-■ 1,009 Moisture in air-current in winter in. 0~~ / / ^ H -""' »~ 000 B ' Is / / S ' ^ >.«^ ^ / A '*-#//( ■cut* f*r ana Moisture in air-current in summer MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY 18,000 A £f\ — - .^-. 18,000 !$3 ^ / ■ *f ** *>* s *> / / / B INT A E AIR CM« 2^ 12,000 Moisture in air-current in spring Figs. 11, 12, 13. Showing moisture in air-current in winter, summer and spring COAL DUST. 43 brought into the mine during the same period. Thus on Friday, March 15, the air brought in 4500 gallons of water in 21 hours, and the return air carried out 15G00 gallons, or 11100 gallons more than was brought in. This mine has an average daily production of 1250 tons; and the quantity of air passing through the mine averages 95000 cubic feet per minute. In fig. 12 the diagram shows the amount of moisture contained in the intake air-current "B" and return air-current "A" for the week begin- ning Monday, August 12, 1912. During this period the moisture of the intake air exceeded that of the return air, and the ventilating current therefore deposited moisture in the mine. The greatest deposit was on Tuesday, at the rate of 4300 gallons per 24 hours. In fig. 13 the diagram shows the amount of moisture carried into the mine by the intake current "B," and the amount carried out by the return current "A" for the week beginning Monday, May 20, 1912. This diagram shows that on Monday the ventilating current was extract- ing water from the mine at the rate of 4000 gallons per 24 hours. The amount of moisture brought into the mine and the amount carried out became equal on Monday, and afterwards the intake moisture became greater than the return moisture. During the remainder of this week, following surface temperature changes, the intake current carried at times more, and at other times less, than the return air-current. For each of the twenty mines in which hygrometers have been installed, and consequently for the entire State, the calculations made from the hygrometer readings during the period of a year show that in winter the coal dust on the ribs and floors loses the greater part of its moisture. This work will demonstrate the necessity of humidifying the air in all gassy or dusty mines in winter. The methods of lessening the dangers of coal dust in use ai the present time, and which the Mining Investigation hopes to study later are: Sprinkling the floor from water-cars Introducing exhaust steam into the intake air-shaft Spraying at intervals along the intake air-course Washing down the face and ribs of working-places before shooting Putting on the floor some chemical salt which will retain moisture. 9. COAL DUST It is a well-recognized fact that dry bituminous coal dust is inflam- mable or explosive under certain conditions. Obviously, therefore, methods of controlling this dust are of great importance to mine safety. It is necessary, however, before a practical and efficient method may be adopted for rendering the dust of any mine inert that accurate data be collected on the quantity, quality, and relative explosibility of the par- ticular dust to be treated. The Cooperative Investigation has collected samples of coal dust in such a manner as to determine the amount of dust per unit area,, the chemical quality, the fineness, and the relative explosibility of the dust in each of the 100 mines visited. In the near future, ibis information will be tabulated and submitted in a bulletin together with deductions 44 COAL MIXING INVESTIGATIONS. which will show the coal dusts in Illinois that are dangerous, the condi- tions of temperature at which explosions of the dust of the various coals will take place, the pressures that may he developed during the explo- sion in the laboratory, and the effects of the admixture of ash, moisture, and marsh gas on the explosibility of the dusts. The gathering of the samples in the mines and their treatment in the laboratory has been accomplished according to the following methods : Two kinds of samples have been collected; (1) Bib-dust samples have been taken at three points in each mine visited; namely, on the main haulage road, on the subsidiary haulage roads, and inside the last crosscut near the face of an entry or a room. These samples were taken according to the following uniform method: A chalk line was drawn from the mine roof to the floor. On one side of this line an area of rib was cleaned with a one-inch varnish brush from the top to the bottom of the coal seam. This area was made of sufficient width for the dust to fill a 40-gram glass bottle. The material was collected on a sheet of celluloid or a piece of clean paper and trans- ferred to the bottle which was then sealed with a rubber cork. The height and width of the area of rib brushed was measured. Note was also made of the temperature, the relative humidity, and the distance that the air had traveled from the intake to the point of sampling. From these three samples are obtained : (a) The condition of the rib-dust of the working places where the velocity of the ventilating current is low and where hand-working or machine-cutting, shooting, and loading, place great quantities of dust in suspension; (b) The condition of the rib-dust on the main and secondary haulage entries, where the velocity of the air-current is high and, as a conse- quence, the finer dust, made by the grinding of the car-wheels and the pounding of the feet of men and mules, remains in suspension. (2) Road-dust samples were taken at two points in each mine visited ; namely, on the main and on the subsidiary haulage roads near the points where the rib-dust samples had been obtained. These samples are taken according to the following uniform method : Covering a distance of about 100 feet along the entry, the 100 feet being so chosen that the above mentioned rib-dust sample was taken at approximately the center of this distance, the sampler gathered on a metal spatula about one ounce of road dust for each 3-foot interval measured along the entry. This material was placed in a metal can having a capacity of at least three pounds. In the laboratory these samples were weighed in order to determine the quantity per unit area ; they were subjected to a proximate analysis, which shows the amount of moisture and the quality of the dust; they were screened through 20-mesh, 60-mesh, 100-mesh, and 200-mesh sieves to determine the fineness under different mining conditions; and finally they were tested in the explosibility apparatus to determine the relative inflammability of each dust. This apparatus, which is described in detail in Appendix "C" (p. 67), consists essentially of a large (1500 c.c.) glass retort in which any desired COAL DUST. 45 Pressure developed in the flask in grams 3 H-> => % © % 8 o ( < ••J c 1* \ V l\ ! \ \ 1- \ V f 1 1 \ \ o 1 \ ^ 1 \ \ 1 1 \ V h- \ CD | \ \ \ \ o \ \ I ) \ \ 1 1 \ \ \ i a> to tn \ \ \ > > % \ \ \ \ ^* 8 Q * ► O 46 COAL MINING INVESTIGATIONS. high temperature may be maintained by the passage of an electric current through a platinum wire. Through the bottom of the retort a definite quantity of coal dust is thrown into the heated atmosphere and against the hot platinum wire; and the outlet for the resulting explosion is through the top of the retort where an attachment determines accurately the amount of pressure generated. An increase in the amperage of the electric current will raise the temperature in the retort and will cause a greater pressure to be generated by the explosion of the coal dust. The results of the tests on each coal dust are plotted, using pressure and temperature as the coordinate, as is shown by example in fig. 14 (p. 45). 10. MACHINE CUTTINGS From the very few tests that have been made in this country to deter- mine the amount of coal dust resulting from machine and hand mining, it appears that there would be 15,000 to 41,000 pounds of 20-mesh dust produced per 1,000 tons of coal. 1 No tests, however, have heretofore been made on Illinois coals; and as this subject is of practical value from the point of view both of mine safety and of the commercial product of the mines, the Cooperative Investigation dining the summer of 1912 made determinations of the sizes of the undercuttings at 10 mines. The results of these tests have made possible comparisons of the amounts of dust and small sizes of coal produced as between the different seams, between machine and hand mining, between puncher and chain machines, and between the various cutting bits in use. The following method was used in carrying on this work at each mine : A room was chosen in which were found average conditions for the mine with respect to hardness of coal, velocity of ventilating current, width of room and room centers on the entry, if the mine is worked on the room-and-pillar system. The floor and ribs for a distance of 20 feet from the face were swept clear of the dust made by previous work. If cuttings were to be tested, the mining machine was then placed in posi- tion and the depth of cut usual in the mine was made. The dimensions of the face and of the cut were measured precisely and the cuttings w r ere loaded out and accurately screened and weighed on the surface. These cuttings included the dust swept from the ribs and floor for a distance of 20 feet from the face. The coal was then shot down by the method of blasting in customary use in the mine, and the coal thus gained was loaded out and weighed at the tipple. All machine cuttings passing through the i/o-inch screen were weighed and quartered down to a sample of 250 pounds, which was shipped to the coal-washing laboratory at Urbana, and there put through screens of the following meshes per inch: 20, 40, 60, 80, 100, and 200. The sets of screens were made especially for this work, and the sizes of openings accurately measured. The sizes screened and weighed at the tipple are of the following meshes in inches : 1%, 1%, 1, %, y 2 and 14. i Jones, B. F., Comparative amounts of dust made in mining: Mines and Minerals, March, 1908, p. 397. Scott, C. E., Dust made in mining coal: Mines and Minerals, May, 1908, p. 477. Rice, G. S., Explosi- bility of coal dust: Bull. U. S. Bureau of Mines, No. 20, p. 33, 1912. COAL DUST. 47 By this method there has been obtained definite information as to the amount of coal made by under-cutting, in each of the following sizes : lump (passing over 1% i ncn screen), l 1 /^ inch, 1 inch, % inch, % inch, i/4 inch, 20-mesh, 40-mesh, GO-mesh, 80-mesh, 100-mesh, and 200-mesh. The power used in under-cutting with electric machines was obtained from the records made by a Bristol's recording wattmeter for direct current having a register of 38 K.W., 250 volts, 150 amperes; together with a Weston voltmeter reading to 300 volts. For punching machines a pressure-gage registered the air pressure, and notes were taken on the size of delivery-pipe, the length of strokes, the number of strokes per minute, and the diameter of cylinder. 11. PREPARATION OF COAL FOR MARKET Because of keen competition, both within the State and with adjoin- ing states, a large amount of work is considered necessary in order to prepare Illinois coal for market. This preparation consists both of removing the impurities, and of dividing the product into many different sizes. Most of the shale and "sulphur" is removed by hand-picking by the miners at the "face," but this is often supplemented by pickers in the tipple or on the railroad cars. The sizing is accomplished by screen- ing equipment which is provided in nearly all tipples, and in some cases a re-screening plant is used for separating the smaller sizes. At the present time there are 35 operating, commercial washeries. A large amount of data has been obtained to show the meihocls, results, and costs of the preparation of the coal (p. 20) and of the washing of the coal (p. 20). Complete data on the wet sizing of coal, however, has not been obtained by the Cooperative Investigation as this subject is being treated in a bulletin of the Engineering Expe- riment Station, University of Illinois. 48 COAL MINING INVESTIGATIONS. APPENDIX A. GEOLOGY OF THE ILLINOIS COAL FIELDS. IXTItODUCTlOX The following geological review is presented because the coal publica- tions by the Geological Survey are almost entirely out of print, and the new cooperative results are not yet ready in final form. In the future, bulletins on coal resources and mining practices will be published for each of the nine districts into which the State was divided for the Cooperative Investigation. Later, a summary report on the Illinois coal fields will be furnished by the Survey as a part of the cooperative work. THE COAL-BEARING AEEA The occurrence of coal in Illinois is limited to the area of the Penn- sylvanian or coal-measures series, as shown by fig. 15. Even within the indicated area the coal is not everywhere present in workable thick- ness and quality. The region which is certainly barren lies outside of the Pennsylvanian boundary in northern, western, and southern Illinois. The coal formations underlie part or all of 86 counties, including approximately 36,800 square miles or about 65 per cent of the entire State. The area underlain by bituminous coal is greater in Illinois than in any other state of the Union. The productive area along the eastern and southeastern borders of the State extends into Indiana and Kentucky, and the fields of the three states comprise the Eastern Inte- rior Field. Probably this coal area at one time was continuous with that of Michigan and with the Western Interior Field which lies west of the Mississippi, but the wearing away of the rocks by surface erosion has separated the neighboring areas. THE COAL-BEARIXG FORMATIONS The coals of Illinois exist as wide-spread beds or as local pockets among layers of shale, sandstone, and limestone which together make up the Pennsylvanian series. There are five coals known to be impor- > t v ; " . >^ j^w ' n cio n — rjc, -nL ^ ----;- i-^J^>^ <^jy. M" /K ^m s vi., *-*ra \-A""»'-^- ' \,ckin '/ >^_ ^ M_ " ,\ /-■'•/ s _/- ' h i r/<> '- IB, K ■ SlflSb^ ■ i '^- vM""< , x V Fig. 15. Map showing coal-measures area in Illino GEOLOGY OF COAL FIELDS. 4!) taut enough to have special nanus, and numerous other beds occur at various depths. The maximum thickness of Pennsylvanian rocks is known to be at hast 2,200 feet, though it is not to be assumed that a single bore-hole could penetrate all of the various formations at tic place of extreme thickness. The Pennsylvanian series has been divided for convenience of descrip- tion into three formations which present different characteristics as to time of deposition, physical composition, and economic importance. The divisions from the bottom upwards are the Pottsville, Carbondale, and McLeansboro formations. POTTSVILLE FORMATION The lowermost formation of the Pennsylvanian in Illinois is com- posed chiefly of massive sandstones interrupted by thinner beds of shale and beds or pockets of coal and fireclay. The prevalence of coarse sand- stone and locally of quartz pebbles has led to the common name "con- glomerate" or "millstone grit'" for the Pottsville in Illinois, as in other states. In Illinois this formation carries plant fragments which indicate, according to White, 1 that deposition took place during late Pottsville time of the Appalachian coal basins. The waters probably first entered the Illinois area in the region of Eardin and Gallatin counties, and extended westward and northward, laying down sandy sediments which,, locally at least, are loo feet thick. The early sediments are thinner to the north and west and are nearly or quite ahsent over much of the State. Massive sandstones in the Rock Island region .">•" of Pottsville age, but later than the first sediments of southern [llinois. inc., Lire a number of occurrences of coal in th" Pottsville in southern counties hut at present they have no commercial importance, because of local or pockety character. The No. 1 coal of Rock Island and Mercer counties is similarly restricted in area but is thick' enough to he valu- able. The topmost sediments of the Pottsville in Illinois include the Cheltenham fireclays, which have been traced through (he counties between SI. Louis and Rock Island, and thence eastward to Ottawa. Evidently much of Illinois was then at or near sea level. The Pottsville closed just before the deposition of Coal No. 2. ( Murphysboro, La Salle, Third Vein, etc.) CARBONDALE FORM ATHi\ The second division of the Pennsylvanian series extends from the base of Coal No. 2 up to the top of Coal No. 6 (Herrin, Belleville, blue-band, etc.). It represents a time interval comparable to the Alle- gheny formation of the eastern states, though the close of Allegheny time in Illinois has not been definitely determined and may include some of the strata Ivine- above the Carbondale as here defined. i White, David., Bull. State Geol. Survey No. II, p. 293, L908. — 4 M I 50 COAL MINING INVESTIGATIONS. The Carbondale is composed, chiefly of shale and lesser amounts of sandstone, coal, and limestone. It includes all the coals mined for commercial shipment except the Rock Island (No. 1) bed, and the Danville (No. 7) bed. This formation extends over practically the whole coal-area, but its upper beds are absent along the rim and its lower beds are not well known in the central part of the basin. The thickness varies considerably, being from 200 to 240 feet in the La Salle region, 200 feet at Peoria, 300 feet at Mattoon, and 285 feet or more in the southern counties of the coal field. MCLEANSBORO FORMATION The topmost division begins at the top of coal No. 6 and extends up to the highest Pennsylvanian rocks of the State. With the exception of the Danville coal (No. 7) which at present is included in this forma- tion, there are no coals of known importance, although a thin bed in Shelby County is mined for local use. The formation is dominated by beds of shale and sandstone, among which are found some thin lime- stones. The Carlinville (Shoal Creek) limestone occurs about 275 feet above the base of the formation and is persistent over a considerable area, The greatest thickness of the formation seems to be in the vicinity of Hamilton and White counties where coal No. 6 lies approxi- mately 1000 feet beloAv the surface. A somewhat less reliable record at Olney indicates a depth of 1155 feet for this coal. THE SPOON-SHAPED STRUCTURAL BASIN The strata beneath the surface deposits of Illinois to a great extent lie horizontal, but locally dip as much as 350 feet to the mile. When all the evidence from mine-shafts and bore holes is studied it is evi- dent that the State is an immense spoon-shaped basin with the tip in the extreme northwest counties and the bowl in the region of Wayne, Edwards, Hamilton, and White counties. The long axis of the "spoon" passes near Olney in Richland County and Lovington in Moultrie County, and the dip in the central part of the basin towards this axis is, commonly as low as 10 feet per mile. Thus, an east-west section from Springfield eastward to Cerro Gordo in Piatt County has a dip of 300 feet in 50 miles or 6 feet per mile. Similarly, the dip eastward from Iuka in Marion County to Olney in Richland County is 400 feet in 40 miles or 10 feet per mile. The warping of the strata along the southwestern and southern rim of the basin has been much more pronounced and has been somewhat relieved by the Shawneetown fault, which extends as a narrow belt from western Kentucky into Illinois at Shawneetown and has been traced at least 15 miles farther west. This fault causes the strata on the north to be about 1400 feet lower than those on the south. North of the fault and along the border of the active coal field, the dip from Cottage Grove in Saline County northward to Eldorado averages 115 feet per mile. Similarly from Marion northward to West Frankfort it averages 50 feet Via. 16. Map showing production of coal, calendar year, L911. (l) Over 0,000,000 short ions; (2) over 5,000,oo<); (3) 3,000,000 to 5,000,000; (4) 1,000,000 to 3,000,000; (5) loo, ()()() to 1,000,000; (6) under 100,000. GEOLOGY OF COAL FIELDS. 51 per mile and locally is double this amount. In the hills 5 miles north- west of Murphysboro the dip is eastward at a rate of 350 feet per mile. The same pilch exists also in the area one mile east of Du Quoin. Although the Illinois basin is approximately spoon-shaped there are minor folds and terrace-like flats on the flanks. The most notable is the La Salle anticline, which is pronounced at La Salle and also in the oil fields of Clarke Crawford, and Lawrence counties. Doubtless it extends as a persistent feature with a rather uniform direction between these distant areas. The west side, facing the axis of the basin, is much steeper than the east flank. Another pronounced anticline has been traced from the region 5 miles west of Murphysboro to Du Quoin and thence northward to Centralia and Sandoval. This Du Quoin anticline is also steeper on the side facing the axis of the basin, in this case the east side. Folds and faults of appreciable size other than those men- tioned have been discovered, and doubtless they will be found to be numerous, as detailed surveys proceed. The structural relations in Illinois arc on the whole unusually favor- able to coal-mining. The first effect is of course to make the coal around the border of the field more easily available than that in the deeper portion, but the extreme depth necessary to reach the most important coal (No. 6, Herrin, blue-band) probably will not greatly exceed 1000 feet, and the shaft at Assumption is already operating successfully to approximately this depth. MINING CENTERS AND DISTRICTS The following notes, in part repeated Prom Bulletin No. II. relate to important geographical district- or mining centers recognized by the public. Relative productions for the calendar year 1011 are shown on fig. 10. WILLIAMSON, FRANKLIN, AM) PERRY COUNTIFS Williamson County led the production of the State for mil with more than 6,600,000 tons. The coal is similar to that in Franklin County and' in the eastern part of Perry County, and has a rapidly growing market. The producing bed is the No. (I or blue-band coal (Herrin, Belleville, etc.) which is from 5 to 10 feet thick, averaging 9 feet over a large area. The top coal, about £0 inches thick, is com- monly left to support the shale roof, and locally is withdrawn after the rooms have been mined out. The ff blue-band" is a clay or shale parting from 1 to 2 inches thick, and about 20 inches above the floor. There is a general northeast dip, amounting io 60 feet per mile in the central part of the county. Local faults occur, in places with 20 to 30 feet displacement. The bed outcrops near Marion, but elsewhere is reached by shafts from 100 to 200 feet deep. There is no sharp line between this field and its neighbors. The same coal is mined in Perry and Franklin counties and to the cast, It maintains some uniformity in physical character and thickness, but 52 COAL MIXING INVESTIGATIONS. varies from place to place in fuel value. At Du Quoin the coal is nearly horizontal, hut east of town it clips rapidly and becomes thicker and somewhat better in quality. SANGAMON, LOGAN, MACON, AND MENARD COUNTIES The Springfield, district, extending into several adjoining counties, has long been one of the most important. Sangamon County produced more than 5,000,000 tons in 1911. The coal of the district is commonly known as No. 5 or the "Spring- field" coal, though in the region south of Chatham, No. 6 only is mined. Xo. 5 is cut by numerous vertical clay veins, from a few inches to four feet in thickness, and lacks the fi blue-band" which characteristically occurs near the floor of No. G. Both beds may have a limestone cap-rock within a few feet of the coal. No. 5 lies about 250 feet below the surface at Springfield and GOO feet at Decatur on the east. The average thickness is a little less than G feet at Springfield and about 4.5 feet at Decatur. There are three higher coals, all too thin to be mined at present, and lying respectively 50, 100, and 175 feet above No. 5. There are likewise several coals below No. 5, but drilling has not yet deter- mined their commercial values. CHRISTIAN, MACOCTIN, MONTGOMERY, AND MADISON COUNTIES The district extending from St. Louis nearly to Springfield and operating in coal No. G is one of the largest producers of the State. The four counties named above had an output in 1911 of about eleven and one-half million tons, of which Macoupin alone produced 4,G88,000 tons. The coal varies considerably in depth and thickness in the counties mentioned. In Christian County it ranges in depth from 340 feet at Ldinburg to 735 feet at Pana, and varies in thickness from 6 to 8 feet. In Montgomery County, the depth varies from 50 to G50 feet and the thickness from 8 to 8V2 feet. In Macoupin County, the depth at Benld is 350 feet and the thickness 8 feet, and at Staunton the depth is 290 feet and the thickness 7% feet. In Madison County the depth is 100 to 325 feet and the thickness 5 to 7 feet. ST. CLAIR, CLINTON, MARION, RANDOLPH, WASHINGTON, AND JEEFERSON COUNTIES St. Clair has long been one of the important coal producers of the State. In the calendar }-ear 1911, it produced approximately 4,000,000 tons. This district, known as the Belleville district, is not set off sharply from its neighbors, since the same coal bed is mined under similar conditions in adjoining counties. It is the "blue-band" seam (No. G), with a parting near the base, and a limestone cap-rock, usually above the slate, but in some places directly overlying the coal itself. The coal outcrops along the western side of St. Clair and Randolph counties and dips eastward from 10 to 20 feet per mile. Local varia- MINING CENTERS AND DISTRICTS. 53 tions are frequent, and faults of 6 feet displacement have been observed; but the general conditions are uniform. The depth varies from the outcrop to approximately 400 feet at Breese, and 300 feet at Coulter- ville. Farther east it has a depth of 425 feet at Nashville, 865 feet at Mt. Vernon, 600 to 680 feet at Sandoval and Centralia, and 880 feet at Kinmundy. Throughout this entire territory, the coal ranges in thickness from 5% to 9 feet, and commonly averages between 6 and 7 feet. As to quality, analyses of face samples indicate considerable irregular variation. VERMILION COUNTY During the calendar year 1911, Vermilion County produced 3,385,000 tons. This has long been an important area shipping principally to the Chicago market. There are three persistent coal seams, two of which are worked. The top or Danville bed (No. 7) appears west of Vermilion River, and is mined along the outcrop and by shafts from 75 to 200 feet deep. It is about 6 feet thick around Danville but thins to about 3 feet ten miles further south. A band of bone or clay, lying 20 inches above the floor, occurs in some of the sections. The Grape Creek coal (No. 6) lies from 20 to 80 feet below the Danville and is more important. Tt becomes thicker southward from Danville, and covers many square miles with a thickness of from 6 to 9 feet. A band of shale or sulphur commonly occurs about 2 feel above the floor and gives rise to the general opinion that this is to be cor- related with the blue-band coal of southern Illinois. Several borings have shown a coal from 185 to 220 feel below the Grape Creek, and measuring from 4 to 8 feet, but badly broken by bands of shale and limestone. SALINE AND GALLATIN COUNTIES Saline County production has had a rapid increase since 1907, and in 1911 reached 3,820,410 tons. The production in Gallatin County remains from 65, 000 to 75,000 Ions per voir, but extensive drilling in 1912 indicates that there will he a considerable expansion in the immediate future. There are two seams, Xos. (i and 5, underlying the northern two- thirds of Saline and much of Gallatin counties, each approximately 5 feel thick, and lying from 90 to LOO feet apart vertically. The upper bed is the blue-band coal (No. (i) which runs west into Williamson and north into White and Hamilton counties. The lower seam is free from regular hands and has considerably higher heating value, though in this respect the upper seam also is excellent. The coals outcrop on the south, and have a general northward dip of 25 to 75 feet per mile. Thus, the coal which outcrops al Equality in Gallatin County is from 900 to looo feel deep in Hamilton County, 25 miles north. Farther northeast, diamond-drill records in the oil fields indicate the presence of the same coals. An east-wesi fault with 54 COAL MIXING INVESTIGATIONS. a down-throw to the north of more than 1000 feet crosses the middle of Saline and Gallatin counties, and probably is related to some minor faulting in this district. FULTON AND PEORIA COUNTIES During the calendar year 1911 Fulton County produced about 2,133,- 000 tons and Peoria County 1,037,000 tons, this being, in both cases, a marked increase over the production of the previous year. Most of the coal from this region goes to the northwest beyond the borders of the State. The principal coal, called No. 5, is from 4 to 4% feet thick, free from partings, and dips gently southeast, usually about five feet and locally as much as 60 feet per mile. Shafts reach the coal at from 75 to 150 feet. In all, seven beds are present here within 300 feet of the surface, but only four have proved thick and persistent enough to be mined. No. 1 and No. 2 are no longer worked and the production from Nos. 6 and 7 is for local use only. LA SALLE, BUREAU, PUTNAM, MARSHALL AND WOODFORD COUNTIES The La Salle or Northern district yields coal chiefly by long wall mining from seam No. 2 or the "Third A^ein." The production from La Salle County has been constant for several years at about 1,600,000 tons. Approximately this amount was mined in Bureau County during the calendar year 1911, while Putnam produced 772,000 tons. The coal averages about 3 feet in thickness, and is blocky and of good quality. It is reached by shafts from 125 to 530 feet deep. About 140 feet above No. 2 lies the so-called No. 5 or "Second Vein." Forty feet above No. 5 lies the No. 7 or the "First Vein." It is shipped almost entirely to the west and northwest, and a comparatively small part of it reaches the Chicago market, , GRUNDY AND WILL COUNTIES The Wilmington field of Grundy and Will counties produced in 1911 approximately 1,000,000 tons. The general conditions are almost identical to those in the district last described, except that the coal lies between 70 and 200 feet beneath the surface, and is reached by com- paratively shallow shafts. The thickness averages 36 to 39 inches and mining is by the longwall method. THE WESTERN FIELD The counties along the western edge of the State are underlain by coals Nos. 1 and 2 which have been traced from La Salle and Kock Island on the north to Murphysboro on the south. No. 1 coal is mined extensively in Rock Island and Mercer counties which together produced nearly one-half million tons in 1911. This coal occurs in restricted areas quite unlike the upper, wide-spread coals of the State. MIXING CENTERS AND DISTRICTS. 55 The mining in No. 2 coal, along the western field, is chiefly at coun- try banks with the exception of that in Jackson County where the famous "Big Muddy" coal is mined from this seam. This county produced 687,000 tons in 1911, of which a major part was from the No. 2 bed at Murphysboro and vicinity. It is shipped mostly to the region south and southeast of Cairo but in part is sent to Chicago where it competes with "Youghiogheny." The No. 2 coal is divided into two beds, each of which has been mined extensively. The beds are separated by shale which varies in thickness from 15 inches to 20 or even 35 feet. The coal is reached by shafts from 100 to 150 feet deep and is mined by the room-and-pillar method. 56 COAL MINING INVESTIGATIONS. CHEMICAL CHARACTER OF ILLINOIS COAL. It has Long been held that the various grades of coal have resulted from the decomposition and natural distillation of vegetal matter, buried under later sediments. At various stages in the process the material is classed as Peat Lignite Bituminous coal Semi-bituminous coal Anthracite coal. Study of the chemistry of Illinois coal has heen difficult both for the specialists who have heen engaged, and for the reading public which attempts to follow the progress of investigations. There has been rapid change in the viewpoint of chemists, and in the adoption of better methods and equipment for ('add sampling, and for laboratory procedure. An important feature of the cooperative investigation has been to collect new samples and to review the entire subject of the quality of Illinois coals. (See p. 26.) The general characteristics of Illinois coal have been presented 1 as follows : "All Illinois coals are bituminous, and, as contrasted with their prin- cipal market-competitor's, are relatively high in sulphur, ash, moisture, and volatile matter. Moreover, as Professor Parr has pointed out, 40 per cent of the volatile matter, or 14 per cent of the whole coal, is non- combustible, as contrasted with 22 and 4.2 per cent respectively, in the case of Pocahontas, W. Va., coal, and 47 and 21.63 per cent in North Dakota lignite. Illinois coals are essentially free-burning and non- coking. They are mainly used for heating and power-generation, and have no large or direct use in metallurgy. The amount of sulphur present precludes their use for furnace-coke and complicates the problem of storage. The large proportion of volatile matter introduces a smoke- problem when the coals are burned in cities, and the high content of ash also detracts from their value. Despite all these facts, they have a high average value for miscellaneous heating and for steam-generation, and many of them are excellently adapted for use in gas-producers. In a general way, it may be said that the Illinois-Indiana coals are not 1 Bain, H. F., Studies of Illinois Coal, Bull. Illinois State Geol. Survey. No. 14, p. 187, 1909 CHEMICAL CHARACTER OF COALS. Of inherently as valuable as the coals of the Appalachian basin, but more valuable than those of the Michigan and Western Interior fields, except- ing limited areas in western Arkansas and eastern Oklahoma." The analyses from mine samples published in Bulletin 16 indicate the general character of the various coals in the important mining- regions of the State. The following statement presents the average results from the old report. Table 5 — Analyses of mine samples (not exactly indicative of com- mercial output) Coal bed. Counties. No. of anal- yses. Coal as received. Moisture. Ash. Sulphur. B. t. u. Fulton Mercer Rock Island. f Bureau . . . | LaSalle... j Marshall. . Putnam. . I [Woodford. / Grundy . . . \Will Jackson . Fulton.. Peoria. . . Tazewell f Logan J Macon j Menard . . . ( Sangamon. /Gallatin. ( Saline. . Christian Clinton Jackson Jefferson Macon Macoupin Madison. . . . Marion Montgomery. Moultrie Perry Randolph. . . St. Clair Sangamon. . . Shelby Washington . f Franklin. . . White Williamson Vermilion. Vermilion. 16.60 14.22 16.12 II). ss 15.15 8.95 12.42 13.19 7 .52 8.23 ."i . 1 5 11.33 10.65 8.27 9.19 4.97 2. si 2.83 1.14 3.26 3.16 1 .85 1.24 2.90 10, 709 11,388 10,850 L2,385 10,547 10,658 12,513 11,012 1 1 , 929 11,110 11,2:56 58 COAL MINING INVESTIGATIONS. It should be remembered that the above values are derived from face samples, containing all natural moisture, ash, and sulphur, except that impurities measuring three-eighths of an inch or more in thickness were arbitrarily excluded. The results indicate the quality that can be obtained if impurities are removed from the coal in mining, and if dirt from roof and floor are excluded in loading the mine cars. Eun- of-mine coal as shipped usually contains impurities which were not present in the sample as analyzed. Prepared sizes, especially lump, may be slightly superior to the mine sample. Carefulness or carelessness in cleaning and otherwise preparing the mined coal for shipment may counteract the natural qualities inherent in the coal as indicated by the above table. 59 APPENDIX B. ILLINOIS MINING SYSTEMS. INTRODUCTION For the information of readers who may not be familiar with the mining practice in Illinois, a general description is here given of the three systems of mining as nsed in the State, namely : Room-and-pillar Unmodified Panel system Longwall Stripping. The choice of a system for any particular mine should depend upon: Character, thickness, and weight of overburden Nature of roof and floor Inclination and thickness of the seam Physical character of the coal Presence and pressure of gas in the seam Danger of spontaneous combustion, etc. In Illinois the coal in practically all of the shipping mines is reached by shafts, and the drift and slope mines are nearly all found among the country banks. The local ion of the -hall, slope, or drift depends on: The shape of the property; the accessibility of a railroad; lie' direction in which practice in I lie district has proven that entry and room driving causes fewesl roof fall- and produces the Largesi amount of lump coal; surface topography; Inclination of bed. The surface topography of the Stale Is as a rule a rolling prairie, and with few exceptions the coal beds are practically Level so that the location of the mine opening is determined mainly by the shape of the property and the shipping facilities. When the coal has been reached and the hot loin arranged, if neces- sary, the procedure varies according to the system of mining adopted. KOOM-AND-PILLAB SYSTEM UNMODIFIED ROOM-AND-PILLAR SYSTEM As shown in fig. 17 (p. GO) in a typical room-and-pillar shaft-mine two parallel entries, one used for haulage ("A") called the main entry and one for carrying the ventilating current ("B") called the back 60 COAL MINING INVESTIGATIONS. JlRKiKTOl Ui1!iiiv5*?rrrrrrrr i III ■i... biifUmi JJLIl|UkLU iiiiii li! l.'llll hi MINING SYSTEMS. 61 entry, are driven on each side of the shaft through the solid coal towards the property boundaries. The consideration of cleavage or "cleat" in the coal does not generally determine the direction chosen for driving entries or rooms in Illinois. The main-entry-pillar between these two entries varies in width from 1(5 to 65 feet. The entries are advanced simultaneously, and outside the shaft pillar are connected at 60-foot intervals by cross-cuts for the purpose of maintaining a flow of air through the entries to the "face." At a distance from the shaft, commonly 300 feet, such that the solid coal surrounding the shaft will be sufficient to protect the shaft from injury by surface subsidence^ a pair of cross-entries is driven to the right and left of the main entries and at a right angle to them. The cross-entries vary in width from 8 to 20 feet, and the coal between them, called the cross-entry-pillar, from 12 to 50 feet. Rooms are turned off at a right angle to the cross-entries at a distance of •")() to 150 feet from the main entries, and thereafter at regular distances. The ((Til between the main-entry or the back-entry and the first room is the main-barrier-pillar. The rooms vary in width from L8 to jo feet, hut in order to protect the cross-entries from a squeeze a room i- not driven full width at first, hut for a distance varying from !» to is feet is driven as a narrow neck from ;) to is feel wide. In widening the rooms either of the two following methods is adopted : 1. One side of the nook- is continued in a straight line forming a side of the room. In this case the width of the room is gained by driving off the opposite side of the neck at an angle either of L5 degrees or of !)<) degrees from the direction in which the neck was driven, until the full width of the room ha- been reached • 2. An angle of T> degree.- or of 90 degrees is turned off each side of the ixck. and when the full room width is reached the driving is con- tinued parallel to the direction of the room neck. The length of rooms in Minois varies from 250 to 300 feet. The coal remaining between room-, called the room-pillar, is from 6 to 30 feel in width. PANEL ROOM-AND-PILL \i; 81 STEM A mine operated on the panel system, ha- room-entries or butt-i ntries as shown in fig. is (p. 62) turned oil' in pairs at intervals of 500 to 600 loot along the cross-entries. The -olid pillar of coal between tie 1 cross entry and the lir-i room, called the cross-barrier-pillar, is from 50 io 125 loot wide. The main-barrier-pillar in this system i- the pillar left between the main-entry and the ends of the rooms turned oil' those room-entries which are nearest to the main-entry. 'Idie obvious advantage of the panel system is thai each panel is sur- rounded (in all sides by a pillar of solid coal and is a separate unit in operation. A squeeze occurring in any panel is confined l>\ the barrier- G2 COAL MINING INVESTIGATIONS. Fig 18 Plan of panel mine MINING SYSTEMS. 63 pillars, if large enough. The ventilating current can be regulated so as to supply air according to the needs of each panel, and pillar-drawing can be more advantageously practiced, thus giving a higher coal-recovery. Whatever modification may be in use, room-and-pillar mining con- templates only a partial extraction of the coal during the first or advance working. The pillar coal left to support the roof is gained in the second or retreating working after the rooms have been driven to their full length. This second working is known as drawing or robbing the pillars and has been little practiced in Illinois up to the present time, partly through fear of surface subsidence and subsequent damage suits, and partly in the older mines because of unsystematic working and too small pillars. Many of the newer mines have been systematically projected and are being worked to secure the pillar coal. LONGWALL SYSTEM According to the longwall system as shown by an actual mine map in fig. 19 (p. 64) the entire bed is removed as the work progresses, the roof at the face being supported by timber, gob, and pack-walls, and the necessary roadways being maintained by pack-walls. A pillar of coal is usually left surrounding the .-haft for its protection from the subsidence of the surrounding strata. On each side of the shafl a main haulage way is driven; from the air shaft a similar entry is driven al a right angle to the first. In some cases these haulage ways are paralleled by other passages used as air courses. When the single entries or the two pairs of entries, as the case may hi', have been driven a distance suffi- cient to provide the desired shafl pillar an entry is driven i<» righl and left of each pair of cut ries or of each single entry. These entries-around- pillar block out the shaft pillar and establish the longwall face. After the shall pillar has been blocked out the main haulage entry 'is continued, and at an angle usually of L5 degrees to it cross-entries are turned oil' on each side at intervals of 200 to :'><>(> feet. From these cross-entries r< is are driven at an angle of to degrees. Room-centers are usually the flask by the release of the compressed air contained in the pressure bulb "K." Before ejecting (he dust into the flask, air is compressed in bulb "E" by means of the compression bulb "F" until a pressure of 200 in. in. of mercury is in- dicated by the manometer "G." 70 COAL MINING INVESTIGATIONS. The source of ignition is a coil of 100 cm. of No. 26 B & S gage plat- inum wire "H" wound upon quartz insulators which are attached to the heavy nickel leads "I." The temperature of this coil can at all times be accurately determined by finding the resistance of the platinum wire for any given current strength. The nickel leads pass through wooden bushings in the top brass plate and serve to suspend the coil in the center of the explosion flask. The ends of the platinum wire are soldered with silver to the nickel leads. The underside of the brass plate is covered with a piece of gasket rubber. The coil is heated by passing through it a direct current of 110 volts. The device used to measure the pressure developed in the flask is made up of a small 50 c.c. flask "K" containing a weighed amount of mercury, and a small steel ball "L" which is ground with emery powder to fit practically gas-tight into the brass tube "M." This tube has an internal diameter of 7 mm. and communicates with the interior of the large flask. "N" is a glass tube which slips into the neck of the flask containing the mercury and serves to keep it in position on the steel ball. OPERATION OF APPARATUS A weighed amount of dust (0.05 grams) is placed in a uniform posi- tion in the funnel. The funnel is next connected to the pressure bulb "E" by means of a short piece of rubber tubing closed with a pinch-cock "O" and placed in a shaped receptacle in the wooden block "P." Using the compression bulb "J?" the air in "E" is compressed to a pressure of 200 mm. of mercury, as indicated by the manometer "G." The explosion flask is then placed in position upon the brass plate "D." The upper brass plate, to which the coil is attached, is placed in position with the coil in the center of the flask. Gas tight connection between the upper brass plate and the ground edge of the top tubulure is made by means of the rubber gasket glued to the bottom of the brass plate. In order to obtain good contacts between the brass plates and the tubulures a steel plate is fitted over the top brass plate and tightened by turning the nuts on the two draw bolts. The steel ball is greased with vaseline and placed in position upon the brass tube "M" with the flask "K" rest- ing upon the top of the ball. Electrical connection is made with leads "QQ." After the apparatus has been thus assembled, the desired current is passed through the platinum coil for exactly three minutes, the expand- ing air in the flask being released by lifting the steel ball at intervals of 1, 2, and 2% minutes. At the expiration of the third minute the dust in the funnel is blown into the flask by the air pressure when the pinch-cock is opened. To prevent back-pressure in the pressure bulb, a check valve "R" is plated in the rubber tubing between the pinch-cock and the funnel. The pressure developed by the combustion of a definite amount of dust at a particular temperature is determined by ascertaining by repeated trials the smallest weight of mercury which must be placed in the flask to prevent the steel ball from being lifted from its position. The COAL DUST LABORATORY. 71 lifting of the ball and flask of mercury by the explosion or igniting of the dust is made evident by the disturbance of mercury in the flask, by the noise of the escaping gas, and bv the presence of carbon on the steel ball. The experiments at a particular temperature are repeated, the weight of mercury being altered each time, until the pressure is found to lie be- tween two weights five grams apart. The mean of the two values is then accepted as the maximum pressure which each dust being studied is able to produce at the temperature used. The maximum pressure which each dust will develop is determined in the above manner for five tempera- tures corresponding to five current strengths, viz : 5.0-5.5-6.0-0.5-6.0 amperes. By plotting the five pressures against the corresponding tem- peratures a clear conception of the behavior of the different dusts can be readily gained and also a means of comparing the different coals (see fig. 14). In all experiments 0.05 grams of the dust arc used, and the result- ant pressure checks consistently if identical conditions are maintained for all experiments. It is essential to have a steady current, and for this purpose an ammeter is always in circuit, the current being regulated very closely by means of a rheostat. \