5 /4.G6-. AMERICAN ASSOCIATION OF PETROLEUM GEOLO.C BULLETIN OF ILLINOIS COAL MINING INVESTIGATIONS COOPERATIVE AGREEMENT Issued bi-monthly VOL.1 September, 1914 No. 4 State Geological Survey Department of Mining Engineering, University of Illinois U. S. Bureau of Mines BULLETIN 7 Coal Mining Practice IN District II BY S. O. ANDROS Published by University of Illinois Urbana, Illinois (Entered as second-class matter, June 1, 1914, at the postoffice at Urbana, Illinois, under the Act of August 24, 1912.) 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 Engineering of the University of Illinois and the State Geological Survey in co-operation with the United States Bureau of Mines. A co-operative agreement was approved by the Secretary of the Interior and by representatives 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, University of Illinois, who jointly determine the methods to be employed in the conduct of the work and exercise general editorial supervision over the publication of the results, but each party to the agreement directs the work of its agents in carrying on the investigation thus mutually agreed on. The reports of the investigation are issued in the form of bul- letins, either by the State Geological Survey, the Department of Mining Engineering, University of Illinois, or the United States Bureau of Mines. For copies of the bulletins issued by the State and for information about the work, address Coal Mining Investiga- tions, University of Illinois, Urbana, 111. For bulletins issued by the United States Bureau of Mines, address Director, United States Bureau of Mines, Washington, D. C. ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00006 3697 ILLINOIS COAL MINING INVESTIGATIONS COOPERATIVE AGREEMENT State Geological Survey Department of Mining Engineering, University of Illinois U. S. Bureau of Mines A MERICAN AS SOCIATION OF PETROLEUM GEOLOGISTS BULLETIN 7 Coal Mining Practice IN District II BY S. O. ANDROS Urbana University of Illinois 1914 1 J? 7^ CONTENTS PAGE Introduction 7 Description of bed 9 System of mining 10 Ventilation 13 Blasting 14 Timbering 17 Haulage is Hoisting 1!) Preparation of coal 21 TABLES No. PAGE 1. Comparative statistics for District II and the State for the year ended June 30, 1912 8 2. Analyses of No. 2 coal in Districts I and II 9. 3. Pressures developed by face samples in explosibility apparatus , 10 4. Dimensions of workings in feet , . . . . 12 5. Per capita production of coal 13 6. Ventilating equipment 14 7. Blasting 17 8. Timbering ....'. 18 9. Haulage 19 10. Hoisting '.'....' 20 11. Sizes of coal made 21 12. Tipple equipment 21 13. Power plant equipment 22 ILLUSTRATIONS PAGE Fig. 1. Map showing area of District I Frontispiece Fig. 2. Arching of top coal in entries 11 Fig. 3. Method of shooting after hand snubhing 15 Fig. 4. Method of shooting after chain machine ] 5 Fig. 5. Method of shooting after puncher machine 16 Fig. 6. Timbering in entries under shale roof 17 Fig. 1. Map Showing the Area (Shaded) of District It BULLETIN OF ILLINOIS COAL MINING INVESTIGATIONS COOPERATIVE AGREEMENT Issued bi-monthly VOL. I SEPTEMBER, 1914 No. 4 COAL MINING PRACTICE IN DISTRICT II By S. O. ANDROS INTRODUCTION District II of the Illinois Coal Mining Investigations, as shown in fig. 1, comprises those mines in Jackson County which produce coal from bed 2 of the Illinois Geological Survey correlation. A detailed description of the districts into which the State has been divided and the method of collecting the data upon which this bul- letin is based is contained in Bulletin 1, "A Preliminary Report on Organization and Method." The physical characteristics of the coal bed and the mining practice of this district differ from those in districts in northern and northwestern Illinois, where bed 2 is also mined. The district prop- erly cannot be considered a part of any other in southern Illinois because in the other southern districts either bed 5 or bed 6 is mined. Therefore, it is necessary to treat this restricted area — although it has few mines and a small production — in a separate bulletin. The first historical record of coal mining in Illinois refers to a flatboat load of coal mined in 1810 at a point on the Big Muddy River in Jackson County. One of the eight mines now operating in the district was opened about forty years ago ; the other seven have been in operation from seven to nine years. The total production of coal during the year ended June 30, 1912, was 500,102 short tons, 0.9 per cent of the total production of the State. This coal was nearly all undercut, 479,779 tons — 95.9 per cent — of the total output having been mined by machines. Machine mining has resulted in a low powder consumption. During the year ended June 30, 1912, 4,500 kegs of powder, 0.3 per cent of the total for the State, were used for blasting coal in the district. The mines employed an average of 750 men for an average of 156 days. Table 1 gives comparative statistics for the District and for the State during the year ended June 30, 1912. COAL MINING INVESTIGATIONS Table 1. — Comparative statistics for District II and the State for the year ended June jo, IQI2& District State Per cent 500,102 57,514,240 0.9 479,779 25,550,019 1.9 3,206 359,464 4,566 1,313,448 0.3 156 160 750 79,411 0.9 117,000 12,705,760 0.9 97 7,049 1.3 653 72,362 0.9 441 43,308 0.8 6.7 10.3 4.3 4.5 33.0 50.9 4.9 4.9 7.3 6.1 180 8 800 1.0 35.7 45.5 25.0 26.3 10.7 10.1 62,513 71,893 Total production Tons mined by machine Average daily tonnage Kegs of powder used in blasting coal Days of active operation Total employees Days work performed Surface employees . Underground employees Average number of face workers (miners, loaders, and machine men) b Underground employees per each surface employee Tons mined per day per employee Tons mined per day per surface employee . . Tons mined per day per underground em- ployee Tons mined per day per face worker b Fatal accidents Non-fatal accidents Per cent from falling coal or rock Per cent from pit-cars Injuries per 1000 employees Tons mined to each man injured Compiled from Thirty-first Annual Coal Report of Illinois. Shipping mines only. Thanks are due to the operators of this district for granting permission to inspect their mines and to the superintendents and mine managers who assisted in collecting data. Special acknowledg- ments should be made to Mr. John McClintock, State Mine Inspector, and to Mr. Thomas Little, former State Mine Inspector, for their valuable assistance. DESCRIPTION OF COAI. BED DESCRIPTION OF COAL BED Bed 2 in Jackson County has only a shallow cover, the coal lying at depths varying from 25 to 160 feet at different mine loca- tions. A characteristic feature of the bed is its division into two benches by a gray laminated shale band varying in thickness from -J inch to 36 feet. Where this parting is thick the lower bench has sometimes been called, erroneously, bed 1. The bottom bench varies in thickness from 3^ to 4 feet, averaging 3f feet. The top bench averages 2 feet. The bed contains few nodular concretions of iron pyrites, but has a layer of bone 2 to 3 inches thick, generally next to the floor. This floor in most places is sandstone, but in sections is shale or fire- clay. The coal shows a pronounced cleavage, northeast to southwest. The chemical composition and calorific value of "No. 2 coal as found in District II vary considerably from those of the coal of the same bed in District I, comprising Bureau, Grundy, LaSalle, Mar- shall, Putnam, Stark and Will Counties. A comparison between the coals of these districts is given in Table 2. Table 2.— A nalyses of No. 2 coal in District I and II \ -l-> "a £ w 6 Proximate analysis of coal: 1st; "As rec'd," with total moisture 2nd; "Dry," or moisture free pq o '£ s S-c 'o ~ u > c II in < 5m I 33 16.18 Dry 38.83 46 . 33 37.89 45.21 7 . 08 8.45 2.89 3.45 10981 13101 1452S II 15 9.28 Dry 33.98 37.46 51.02 56.24 5.72 6.30 1.29 1.42 12488 13765 14818 a. Analyses made by J. M. Lindgren under the direction of Prof. S. W. Parr The superiority of the coal in District IF is apparent. It has less volatile matter, more fixed carbon, less ash and moisture, and a higher calorific value than the coal of District I. The small amount of gas given off by the bod is usually found only in abandoned workings. Where the parting is thin and the two benches are united, the roof over the coal is a hard gray shale, but where the parting is thick and only the lower bench is worked the parting becomes the roof. 10 COAL MINING INVESTIGATIONS Where this parting is a light gray shale it is easy to support ; where it is dark colored it slakes much on exposure to the air. In all the mines of this district numerous small faults occur and horses, usually of a hard dark gray micaceous sandstone, are found in the vicinity of the faults. The presence in places of a quicksand deposit about thirty feet below the surface has a marked effect on surface subsidence after roof-caves. Table 3.— Pressures developed by face samples in explosibility apparatus District No. samples Pressure in pounds per square inch at 2192° F I 11 8.40 II 5 5.88 III 5 7.81 IV 17 7.70 y 7 7.11 VI 16 5.95 VII 24 7.00 VIII 6 8.93 The face samples of coal from this district when ground to 200- me'sh size, air-dried, and tested in the explosibility apparatus at the Urbana laboratory show less explosibility than the coal of any other district, although the rib dust of some other districts is less explosible on account of an admixture of fine shale dust. In Table 3 are com- pared pressures developed in the explosibility apparatus for the various districts in Illinois. SYSTEM OF MIOTMJ Although the coal bed in this district has a thin cover all mines are opened by shafts. There are no drifts, slopes or strippings. Seven of the eight mines are worked according to the double entry room-and-pillar system ; the panel system with triple main entries, maintaining one of the air-courses for a traveling way, is used in the other mine. The variable shale parting in the bed gives rise to two sets of conditions. Where the parting is less than 4 inches thick the two benches of the bed are worked as one and the working faces in rooms and entries are 6 to 7 feet high in places. Where the parting is over 4 inches thick the lower bed only is mined and the parting becomes the mine roof. The lower bench averages 3f feet. Where both benches are worked and the bed is over 6 feet thick only the lower 6 feet of coal is mined, 8 to 12 inches of top coal being MINING PRACTICE 11 left. The shale roof disintegrates on exposure to the air, but top coal is not affected by temperature and remains intact for many years. Where it is possible to leave top coal in entries the roof is arched, as shown in fig. 2. In driving entries the lower 3 feet of Fig. 2. Arching: of Top Coal in Entries. coal is drilled and shot off the solid; but all arching in the upper 3 feet is hand sheared, with the result that the top coal remains per- manently in place and requires no support except where fractured by slips. Top coal is arched in several districts in Illinois, but usually the arch is roughly formed by shooting, and the top coal is often fractured by the shots. Where the two benches of the bed are united but the coal is not over (\ feet thick the full thickness of the bed is mined, and the gray shale overlying the coal becomes the roof. In rooms 2 to 4 inches of this shale are drawn or come down with the coal. Where the lower bench only is worked, by the terms of the Illinois State Agreement between the Illinois Coal Operators' Association and the United Mine Workers of America the miner brushes 14 inches of roof over roadways in rooms. The width of brushing varies from 5 to 8 ^oot. The gob obtained is laid along both sides of the track. Only one of the mines examined operates with any regular dimensions of rooms and pillars. At all of the others pillar-gouging is permitted. In one mine the coal of the main barrier pillar was 12 COAT. MINING INVESTIGATIONS token out, leaving an insufficient pillar to protect the main entry. The main and cross entries vary in width from S to 9 feet. In the one mine operating on the panel system the width of room entry is 9 feet; 16 rooms being turned off each entry. No attempt is made to draw pillars except in the panel system mine and there when two adjacent rooms are driven up, the room pillar is drawn, where it has not been gouged, by taking a 6-foot slice off each rib. It is said that one-half of the pillar coal is thus recovered. Th*e cleat in the bed is well marked, but in the panel mine alone is advantage taken of the cleavage to drive entries on the butt of the cleat, and rooms on the face. Numerous horses of micaceous sandstone and small faults cause difficulty in mining and add considerably to the cost of coal pro- duction. In places these horses are of great length, one of them extending throughout a mine. In driving through these, blasting with dynamite is done off the solid. Table 4 gives dimensions of workings at each mine examined. Ta BLE 4.- — Dimensions of workings w /eg/ 00 Entry width Entry pillar width Room 'a Room-neck a ■5 £ p * o x £ ^ n £ E o *o %% c * & X o X X X S-B c^ u d CtI 6 ft Q t/3 C/2 2 o O C "3 2 o u O Sft bo a C ■5| 11 12 125 Room-and- pillar 8 8 12 12 20 24 150 18 8 10 45° to right and left 20 8 44 13 114 Panel 9 9 20 20 30 24 250 20 9 4 45° to left 20 9 55 14 135 Room-and- pillar 8 8 18 18 28 250 22 8 12 45° to left 22 8 46 15 160 Room-and- pillar 8 8 18 18 20 25 240 17 8 10 45° to right and left 20 10 49 To obtain full room width in two mines room necks are widened at an angle of 45 degrees to the left only ; in the others the widening is done at 45 degrees both to the right and left. Where the roof falls under quicksand deposits, sand and water are admitted. In one mine approximately 1,000,000 gallons per 24 hours flow into the mine through caves. This water is pumped out through drill holes by two automatically-started electric turbine pumps of 250 gallons per minute capacity; two stationary electric pumps of 180 gallons per minute capacity; and five portable electric pumps discharging 70 gallons per minute. Water flows into some mines through chan- nels in the floor under the coal. The caves under quicksand deposits MINING PEACTICE 13 often bring about surface subsidence, one of 18 feet having been reported. The laborers in the district are principally of three nationalities : American, Italian arid Negro, the majority being Americans. Although nearly all the coal produced is undercut, the per capita production of all classes of employees iu the district is low as com- pared with that in all other districts of the State combined. (Table 5.) Table 5. — Per capita production of coal Mine No. Average daily tonnage Number employees Surface employees Underground employees Face workers (miners, loaders and machine men) Underground employees per each surface employee Tons of coal a day per employee . . Tons of coal a day per surface employee Tons of coal a day per underground employee Tons of coal a day per face workerb 12 150 54 4 50 12.5 2.8 37.5 3.0 4.1 13 1300 255 50 205 152 4.1 5.1 26.0 6.3 8.5 14 300 93 13 80 56 6.2 3.2 23.1 3.8 5.4 15 800 196 26 170 130 6.53 4.1 30.8 4.7 6.2 Dist- tricta 3206 750 97 653 441 6.7 4.3 33.0 4.9 7.3 All other districts combined* 356,258 78,661 6,952 71,709 52,877 10.3 4.6 51.3 5.0 6.8 a. For the year ended June 30, 1 ( .H2. b. Shipping mines only. The district has been fortunate in having but few fatal acci- dents, but the number of non-fatal accidents is greater than is war- ranted by the coal output. The sum, however, of both fatal and non-fatal accidents is consistent with this output, which for the year ended June 30, 1912, was 0.9 per cent that of the State. In this year 0.8 per cent of the combined fatal and non-fatal accidents in the State occurred in District I I. VENTILATION The ventilation of the mines in this district presents no difficult problems, and the ventilating equipment is suitable to their capacity. (Table 6.) The largest quantity of air delivered by the ventilating fan at any mine examined was 50,000 cubic feet a minute; a greater quan- tity is unnecessary because gas is not present in large quantities, and also because comparatively few men are employed in the present workings. Two of the mines examined had blowing fans, and two 14 COAL MINING INVESTIGATIONS •exhaust. Sling psychrometer readings in rooms for October, 1913, showed a relative humidity of mine air varying from 90 to 100 per cent. The return air at one mine had 100 per cent relative humidity, as shown by hygrometer readings reported daily by the mine officials from February 11, 1912, to February 16, 1913. Table 6. — Ventilating equipment No. Depth of air-shaft Size in feet of air-shaft in clear Type of fan Diameter of fan in feet Width of blade in feet 12 13 14 15 125 114 135 160 8 by 10 9 by 20 ±y 2 by iy 2 8 by 12 Paddle wheel 1 Robinson Paddle wheel Robinson 16 10 16 6 4 3 4 V/ 2 1. Paddle wheel refers to straight blade type of fan; often home made. ~Mo underground fires of consequence have occurred in the dis- trict. Seepage water makes unnecessary the sprinkling of roadways. The underground fire liability is further decreased by the stabling of mules on the surface. In mine 9 of the Big Muddy Coal and Iron Company danger of underground fire is reduced to a minimum by prohibiting the storing of oil in the run-around. The daily supply taken below is stored in a small room driven in the rib near the shaft and closed by a fireproofed door. The oil is also heated here by steam coils. This mine has one intake haulage entry and two return air-courses ; is operated on the panel system : and is one of the two mines of the district in which have been placed concrete stoppings on the perma- nent entries. These stoppings are built with concrete blocks 5 inches thick, having an exposed surface 8 by 20 inches. The blocks — made on the surface with 1 part cement and parts cinders — cost 6 cents each delivered at the pit mouth. Stoppings of untamped gob in two of the mines examined gave low ventilating efficiency because of the large amount of air short- circuiting through leaks. Although the dust of the district is not highly explosive the dan- gerous practice, observed in one mine, of leaving machine cuttings at the face while shots are being fired should be prohibited. At one mine a brick-lined air-shaft has recently been sunk. The air-shafts at all other mines are timber lined. BLASTING In District II a greater proportion of the coal mined is under- cut bv machines than in anv other district of the State. During the MINING PRACTICE 15 year ended June 30, 1912, the district produced 500,102 tons of coal of which amount 470,779 tons, 95.9 per cent of the total production, were mined by machines. Every mine in the district except two local mines has undercutting machines installed. PLAN Fig. 3. Method (if Shooting After Hand Snubbing At three of the four mines examined puncher machines operated by compressed air are used; in the other mine the coal is undercut with electric chain machines. The usual method of supplying air to PLAN Fig. 4. Method of Shooting After Chain Machine the puncher machines is to carry it from the compressor down the shaft and through the main entry in a 4-inch pipe, reducing to a 16 COAL MINING INVESTIGATIONS 2-inch in the cross entries and to 1^ inches from the cross entries to the faces of rooms. The large percentage of undercut coal accounts for the use of a comparatively small amount of powder. During the year ended June 30, 1912, the district while producing 0.9 per cent of the out- put of the State used 4,566 kegs of powder for blasting coal, only 0.3 per cent of the total for the State. Size FF black powder is used exclusively in blasting coal. The use of this small grained powder results in a low percentage of lump coal. At the mines examined the per cent of coal over 1^ inches varies from 50 to 70. The number of tons of coal gained per keg of powder varies from 100 to 150 and the output per machine from 35 to 150 tons. In the mines of this district the provision of the State law in regard to material for tamping holes is not observed carefully: machine cuttings in dummies are often used. Tn general the length of holes drilled is consistent with the depth of undercutting and the thickness of the bed. I FRONT SIDE PLAN Fig. 5. Method of Shooting After Puncher Machine The general methods of placing holes in the face are shown in Figs. 3, 4 and 5. Three holes constitute a round at every mine examined. The only variation of method is in the distance below the roof at which the center hole is drilled. Koof brushing, which is done with black powder, is easily accomplished, one hole about 2 feet long bringing down 4-J linear feet of roof. Table 7 gives blasting data for each mine examined. All of the MINING PRACTICE 17 figures for the percentages of lump coal over 1J inches were obtained from the books of the companies. Table ' r. — Blasting No. Kind of machine Tons a day per machine Length of holes in feet Tons of coal per keg of powder Powder cost in cents per ton of coal Per cent of lump over 134 inches 12 13 14 15 Compressed air puncher Electric chain Compressed air puncher Compressed air puncher 4 5 4^ 35 150 4 6 4% 5V 2 100 115 150 125 1.8 1.7 1.2 1.4 70 50 See foot note a 60 55 over \Yi inches TIMBEKIKG Where the two benches of the bed are united and the coal is over 6 feet thick, top coal is left up in entries and the roof is arched. (Fig. 2.) ~No timber is used in entries under top coal except where it is broken by slips. When the lower bench only is mined the roof is supported by three-piece timber sets having 8-inch crossbars and 6-inch legs. White oak is generally used for entry timbering. In a few instances the legs of the timber set are placed in hitches cut in the rib. (Fig. 6.) In one mine 80-pound steel crossbars with T section are used on white oak legs under bad roof on the main haulage entry and white oak crossbars in all other entries. Fig. Timbering in Entries Under Shale Roof 18 COAL MINING INVESTIGATIONS The roof in rooms not working under top coal is difficult to support. Roadways to the face are provided by brushing the roof in low coal and throwing the gob alongside the track. Propping expense is heavy; the number of props per 100 square feet of roof varying from 4.8 to 7.5 is greater than in any other district in Illinois. (See Table 8.) These figures were obtained by counting the number of props in 100 linear feet of typical rooms the widths of which had been measured. Room propping is carefully done in the district, especially in one mine, where systematic propping is enforced. At this mine, where pillars are drawn by cutting a slab 6 feet wide from each rib, two extra rows of props are set between the track and the right-hand rib to support the roof as the pillar is drawn. The operators of the district often are able to get 30 per cent of white oak timber in each shipment of props. Both split and round props with a diameter of 4-J inches at the small tip are used at each mine examined. Their length varies from 4 feet under low coal to 7 feet when both benches of the bed are united. The total timbering cost, including room propping and entry timbering, varies from 5 to 8 cents per ton of coal mined. All shafts in the district except one — which has a brick lining — have timber linings, as they were sunk before the passage of the State law requiring new shafts to be iireproofed. Table 8. — Timbering Total timber cost in cents per ton of coal. Room Props No. No. per 100 square feet of roof Cost in cents per 1C0 square feet of roof. ^ . tun QJ ■S.3 31 c o 12 13 8 6.6 4.8 7.5 5.5 26.4 33.6 33.8 38.5 4 7 7 18 18 18 24 33 15 14 25 15 30 HAULAGE Conditions in the district are not favorable to low haulage costs. Two of the mines examined had modern equipment, but in only one was sufficient attention paid to easing curves and maintaining MINING PRACTICE 10 uniform grades. In general throughout the district haulage entries are too narrow for safety, and are not kept free from gob. Pit cars are hauled from partiugs to the bottom by main-and- tail rope in one mine, by standard electric locomotives in one, by a rack-rail electric locomotive in one, and by mules in five. Hauling from face to partings at all mines is done by mules. They are kept in good condition. The rails are light, varying from 16 to 30 pounds on the main haulage and from 12 to 16 on the cross entries and in rooms. Track gages vary from 30 to 42 inches. Table 9 - —Haulage Rail weight in Pit Cars c Kind of haulage in main entry o a> H . o ° £ MM S.S pounds per yard Q & I 5 o +j • 6 CD be " s i Second- ary haulage Weight in pounds Capac- ity in pounds Per cent car weigh total load 12 Mule 36 16 16 1200 1800 1.5 40.0 13 Electric locomotive 2 42 30 16 2400 4300 1.8 35.8 14 Mule 32 16 12 1100 2600 2.4 29.7 15 Electric rack-rail locomotive 2 30 30 16 2200 3000 1.4 42.3 Those mines working in the lower bench where narrow and low entries are necessary have light pit cars of small capacity; at only one mine in the district do the pit cars each hold two tons. The average weight of these cars at the mines examined is 1,725 pounds; the average capacity, 2,925 pounds. Hence, an average of 37.1 per cent of the weight hauled from face to shaft is car weight. An excess weight of car is carried in transporting the coal in the mine. With a car lighter and of greater capacity, haulage expense could be lessened. ~No figures for ton-mileage of locomotives could be obtained. Table 9 gives haulage data for each mine examined. HOISTING No mine in the district has a sufficiently large daily production or is of such depth as to necessitate great hoisting speed, so that the hoisting equipment has no unusual features of size or arrangement. First motion hoisting engines are in use at all mines examined. Cylindrical and conical drums are each used at two mines. 20 COAL MINING INVESTIGATIONS Table 10. — Hoisting o3 4^ ■S-S w M*>, cu Drum T_l CD -M C CD C CD a .a ►3.9 12 150 Yes 125 6 by 14 No 12 by 16 Cylindrical 4H 8 13 1300 Yes 114 9 by 20 Yes 18 by 36 Conical 7 5 14 300 No 135 7 by 12 No 18 by 36 Cylindrical 434 8 15 800 Yes 160 7 by 16 No 16 by 32 Conical 6 6 1. Largest diameter if conical. Caging at the bottom is done automatically at one mine and by hand at three, although in only one is there a platform cage from which the cars are pushed by hand at the tipple. Table 10 gives hoisting data for each mine examined. PREPARATION OF COAL PREPARATION OF COAL 21 The sizes of coal made in this district, which differ at each mine examined, are shown in Table 11. Tipple equipment is given in Table 12. Table 11. — Sizes of coal made No. Name Size. 12 Lump Over 2 l /i inches Under 234 inches. Screenings 13 Six-inch lump Over 6 inches. Six-inch egg Over 4 inches and under 6 inches. One-and-one-half inch lump . . Nut Over \}/2 inches and under 4 inches. Over \}/% inches and under \}/2 inches. Screenings Under \}/% inches. 14 Six-inch lump Over 6 inches. One-and-one-half inch lump. . . Nut Over 13^ inches. Over % inch and under 1^ inches. 15 Six-inch lump Over 6 inches. Six-inch egg Over 3 inches and under 6 inches. Small egg Over 2 inches and under 3 inches. No. 1 Nut Over \ l /i inches and under 2 inches Over l /i inch and under \ l /i inches. Under l /i inch. No. 3 Nut No. 5 Nut At each mine examined shaking screens are used, with lengths varying from L6 to 42 feet, and with widths of 6 to 8 feet. They have an inclination of either -'5 or 4 inches a foot, and make 1 from 60 to 100 shakes a minute. At the one mine where a further separation is made after pass- ing the coal over a shaker-screen a washery of the Stewart type is installed. A description of this washery is contained in Bulletin 69, ( !oal Washing in Illinois, published by the Engineering Experiment Station of the University of Illinois. Table 12. — Tipple equipment Sizing screen Is coal rescreened or washed O u wj No. Inclina- tion (inches per foot) Shakes per minute Coo