Mining Magazine v.ll, no.3 March IS05
THE MONTANA COAL FIELDS:
THEIR COMMERCIAL VALUE
By J. P.
-j A /T ONTANA
tt % /1 ranks first
1V1 in the
production of cop- per, fifth in the pro- /flf \ duction of gold, and
tUKn ttt of the Rocky Moun-
I lr tain States, it ranks
9 I A third in the produc- tion of coal. Its coal area, however, greatly exceeds that of any Western State, and it bids fair to equal Colorado and Wyoming within a few years.
Its coal fields have been mined for more than a quarter of a century, but, owing to the size of the State and the sparsity of its population, the fields have been very slowly developed. In 1880 less than 250 short tons of coal, valued at less than $1,000, were produced in the entire State. In 1903, however, the production amounted to upwards of 1,600,000 tons, valued at over $2,600,000 at the mines. The production for 1904 was a little less, owing to a few shut-downs. That of 1905 is expected to exceed the output of any previous year.
More than $6,000,000 are now invested in the coal properties of Montana; nearly 3,000 men are employed, receiving salaries amounting to nearly $2,000,000 annually. The average number of days each miner works during a
ROWE
year is about 245. However, the mines at a few places are working alternate days. There are now 550 finished coke- ovens and 100 others partially finished. In 1901 over 57,000 tons of coke were produced in the State, valued at about $360,000 at the ovens. In 1904 the production was about 30,000 tons of coke.
The coal fields may be divided into three general groups: First, the Eastern or Plains Cretaceous Lignites— covering more than half of Montana. Second, the Metamorphosed or Middle Mountainous Cretaceous Deposits—including semi-bituminous, bituminous, semi-anthracite and coking coals—running northwest-southeast across the State. Third, the extreme Western or Tertiary or Neocene Lake Beds Lignite, embracing almost the entire width of the State. In each of these general groups many mines are now in operation.
The most productive area is the Middle Metamorphosed group, which furnishes all fhe coke and practically all the coal. It is divided into ten fields, as follows:
(1) Flathead: Flathead County
(North, Middle, and South Forks). 2. Great Falls: Teton County( Choteau) ; Lewis and Clark County (Augusta) ; Cascade County (Sand Coulee, Belt and Stockett); Fergus County; Meagher County (Northwest Corner,
MINING MAGAZINE
SLLOWSTONI
Bated on U.S.Geological Suruey Maps j and Personal Field Work J J.P.ROWE
The Coal Fields of Montana.
Smith Creek). (3) Judith Basin: Fergus County (Lewiston). (4). Clark’s Fork: Meagher, Sweetgrass and Yellowstone Counties; Carbon County. (5) Yellowstone: Gallatin, Sweetgrass and Park Counties. (6) Cinnabar: Park County (Aldridge). (7) West Gallatin and Trail Creek: Gallatin County. (8) Ruby Valley: Madison County. (9) Rocky Fork: Carbon County (Red Lodge). (10) Bull Mountain: Yellowstone County.
The commercial coal and lignite occur almost entirely in the Cretaceous formations, chiefly in the Upper or Laramie. Some coal has been found in formations lower than the Cretaceous, but in amount too small to be of commercial value. Lignite and semi-bituminous coal are also found in the Neocene deposits, but are yet unknown in a commercial way.
The geological formations where good coal and lignite are found, and the producing counties, are as follows:
Tertiary: Ravalli and Missoula
Counties.
Fort Union (?): Carbon Co. (Red Lodge) and Yellowstone Co.
Cretaceous - Laramie (Transition): Granite, Deer Lodge (?), Powell, Fergus (lignite), Meagher, Sweetgrass, Yellowstone, Carbon, Gallatin, Park, Madison, Valley, Choteau, Dawson, Custer, Rosebud and Beaverhead Counties.
Cretaceous: Montana, Colorado
Dakota (Upper Cretaceous—coal beds wanting), Kootanie (of Dawson— Lower Cretaceous), Flathead, Teton, Lewis and Clark, Cascade, Fergus, and Meagher Counties.
While all of the above counties produce either coal or lignite, but ten yielded in 1904 material amounting to as much as $1,000. Rosebud, the lowest of these ten, produced about $1,100 worth of semi-bituminous coal; while Cascade, the highest, yielded an output valued at upwards of $1,250,000.
MONTANA F1L£
THE MONTANA COAL FIELDS
The mining methods and machinery employed in the larger mines of Montana are similar to those of other States, only a few of the large producing mines using pick mining. The Nelson Coal Company, of Sand Coulee, the latest to change to machine mining, has made more rapid advancement than any other in the State. Its output in 1903 was 53,000 tons, in 1904 over 100,000 tons. The coal seam is 10 feet thick and one of the best in the State; the coal is good gas and steam c.oal, free from bone. There are two streaks of coking coal, about 8 inches each, but these are not separated.
The mine product, about 500 tons daily, is taken from the mine in cars holding 1 y2 tons each, drawn by mules; the run is 150 yards from the entrance of the mine to the tipple. Most of the output is shipped to Great Falls or sold direct to the Great Northern Railway Company. The miner’s
lamp is the only source of light in the mine.
The wages received by the men, for an eight-hour day, are as follows: Inside: miners, $3.60; machine runners, $3.60; drivers (one or two mules), $3-I3I greasers, $1.60; general unclassed, $3.00. Outside: engineers
(first-class license), $4.00; blacksmith, $3.50; carpenter, $3.50; firemen, $3.00; tipple laborers, $2.50; not classified, $2.50. About 130 men were employed here during-the past summer.
Near this mine, on the same vein, but a little thinner, is another, owned by a Mr. Gerber. It produced about 75,000 tons during the past year. Eight machines are used and 170 men employed; wages are the same as at the. Nelson mine. Many smaller mines are also found in the vicinity.
The mines at Stockett are among the largest producers in Montana. Five have been opened here, and three al-
Plant at Belt, Mont
MINING MAGAZINE
ready worked out. The seam is a continuation of the Sand Coulee, but is not so thick. The mines are owned by the Great Northern Railroad Company, and produce about 400,000 tons annually. During 1903 a coal breaker was constructed at a cost of about $43>~ 000. The mines are well ventilated, lighted by electricity and have now in use thirty-six Harrison mining machines and twelve Rand air-drills. The coal contains quite an amount of iron pyrite nodules and some bone, but since the introduction of the new cleaner the works compare favorably with any in the United States.
A. C. M. Plant at Belt, Mont.
By the agreement of the United Mine Workers of America with the coal companies of Montana, the miners receive the following, per square foot. For all places over 12 feet wide: machine men, i)4 cents, machine helpers, 1 y2 cents. For all places 12 feet wide or under: machine men, 3 cents, and helpers, 2 cents. In deficient places, machine men are paid $3-6° a day ar*d machine helpers $3.00; loading coal 21 cents per ton of 2,000 pounds, run of mine. No loader shall load coal in rooms of entries farther than 10 feet, and pillars no farther than 15 feet; loaders shall keep all rock 9 feet from
the face; where more than the average quantity of rock exists, the company shall furnish men to clean such places. Here, as at other coal mines in the State, the miners have the privilege of employing a check weighman at their own expense.
The mines at Belt are owned by the Anaconda Copper Mining Company, and part of the coal is coking. This is mined and loaded separately from the rest of the seam; when washed and coked, all of the product is shipped to the smelters at Great Falls and Anaconda. The mines have many miles of rope haulage and air-ways. One main trail-rope system, about a mile long, runs through the main entry to the tipple. As the seam has many rolls, there are several independent rope systems which handle the cars from the partings nearest the working faces to the main parting. Twenty-two Ingersoll- Sergeant punchers are used in this mine. During the past year 560 men have been employed. The output of coal and coke for 1904 was 145,000 tons. There are 100 coke ovens at this place.
The wages paid are as follows: Inside: miners, $3.60; machine runners, $3.60; rope riders, $3.50; parting men, $3.13. Outside: engineers (first-class license), $4.00; weighman, $3.50; machinists, $3.00; ashmen, $2.50; jigmen, $3.00; cokemen, $2.50. In places where the seam is over five feet thick, pick miners receive 70 cents per ton of 2,000 pounds; loaders, 35 cents; machine operators, 7 cents. Where the seam is less than five feet thick, pick miners receive 80 cents per 2,000 pounds; loaders, 41 cents; and machine operators, 9 cents.
The largest and most productive property in the State is located at Red
MONTANA FILE THE MONTANA COAL FIELDS *45
Coal Strata at Red Lodge, Showing Dip.
Lodge. It is owned by the Northern Pacific Railroad Company, and is modern both in methods and machinery. There are several seams developed here with a total thickness of 60 feet. The output of the mines in 1903 was nearly 550,000 tons, and about 480,000 tons in 1904. Over 500 men are employed. The mines at Red Lodge are lighted by electricity, generated by the company’s plant; in some of the mines electric motors haul the coal, while on the incline a cable is used.
While the seams at Sand Coulee, Stockett and Belt are nearly horizontal, these have a dip of from 160 to 20° to the south. No. 4 mine is the best developed seam. Five levels have been driven to the east, and four to the west. The third and fourth levels to the east have been driven about 9,000 feet from the slope, and the second
level west has been driven nearly a mile from the slope. A slight amount of gas is ocasionally found in the mines, but it has given no serious trouble. Everything inside is in excellent working order. The surface works are modern and include an excellent electric-light plant, generating both alternating and direct currents; a 600- ton Liihrig washer, recently installed; steel tipples; box car loaders, and both steam and electric fans.
The wages are as follows: Inside: miners, $3.60; car cutters, $3.00; mo- tormen, $3.13; trappers, $1.25. Outside: engineers (other than first-
class), $3.50; car repairers, $3.50; head washer, $3.50; other washers, $2.50; pin knockers, $2.75; tipple laborers, $2.50. There are also several smaller mines near Red Lodge.
The coal mines at Bridger are owned
246
MINING MAGAZINE
Northern Pacific Plant at Red Lodge, Mont.
by Senator W. A. Clark, of Montana; but one seam, five feet thick, is mined. The equipment, both inside and out, is first-class in every particular. The power-house has four boilers, with rated capacity of 125 h.-p. each, which supply steam to run two highspeed McEwen engines of 250 h.-p. each. These drive two 100-kw. bipolar Link-Belt electric dynamos, generating at 500 volts, supplying power to operate one 250 h.-p. electric hoist; one 80- li.-p. Link-Belt locomotive; one 60- h.-p. Worthington three-plunger electric pump for mine; seven Link-Belt electric chain breast mining machines; one 30-h.p. ventilating fan, etc. The tipple, located some distance from the mine,'is equipped with a Phillips dump and shaking screen; the Ottumwa boxcar loader is used. The output of this property is about 50,000 tons per year. Nearly a hundred men are employed
and the wages are practically the same as at Red Lodge. There are also other small producers around Bridger.
The property at Gebo, owing to litigation, has not shown its true worth. It has all the modern equipment and a good seam of coal six feet thick. The tipple, which is of steel with shaking screens, is about one mile from the mines. The power for hoisting, ventilating, drilling, etc., is furnished by a new and modern electric plant, installed by the Link-Belt Machinery Company. The output of this mine for 1904 was nearly 25,000 tons. Between 50 and 75 men were employed, receiving the same wages as at Bridger.
Storrs is a- comparatively new camp, I but gives fair indications of being an excellent property. It is owned by the Amalgamated Copper Company, and most of the coal is coking. A spur from Chestnut, which is on the main line of
MONTANA FILK
THE MONTANA COAL FIELDS
z47
the Northern Pacific, runs to Storrs —a distance of but three or four miles —thereby connecting the mine with Butte, Great Falls, and Anaconda, the homes of the Amalgamated Company’s smelters in Montana.
There are three tunnels, and in each the work is done by pick mining. The seams are greatly faulted and their products usually more or less fine; but very little lump coal is found. No. i entry dips to the north and varies from 350 to 45°; Nos. 2 and 3 dip north and east. The coal beds have an altitude of about 5,500 feet. The seam is about five feet thick, and from 100 to 200 men are employed. Owing to a shutdown during part of the past summer, the output of coal and coke for 1904 was only about 10,000 tons. One of the most modern and down-to-date plants in the United States is found here; it includes a large Liihrig washer, an electric-light, plant, and iog( finished and 100 partially finished .coke ovens.
The tipple and. coke-ovens are situated nearly a quarter of a mile from the mines. That part of the coal from the upper tunnel is conveyed to the track, on a level with the tipple, by means of a chute; the product from the other tunnels is loaded in cars in the mines and hauled direct to the tipple. The mines are easily drained and well ventilated. The wages paid here are practically the same as elsewhere. All coal 2,Va feet and over in thickness is paid for at the rate of 60 cents per 2,000 pounds.
The mines at Cokedale are among/ the oldest of the State, but have beenj closed for several years. They were re^ opened during the summer of I9°3»' however, and much development work
has since been done. The old washer has been repaired and the 100 coke- ovens are now in good condition. The output in 1904 was between 5,000 and 7,000 tons, the entire amount being used at the place. The number of men employed was about 75. These mines will probably be among the best producers during the year 1905. Cokedale is located on a spur of the Northern Pacific Railway about nine miles west of Livingston, just across the divide from Storrs.
Amalgamated Copper Company’s Plant at Storrs, Mont.
/The property at Chestnut, owned by (the Northern Pacific Railway Company, is probably the oldest large producer in Montana. The mines are situated near the Northern Pacific main track. Air is used instead of steam for the hoisting engine and a new washer has been constructed a few rods from the old works. The seam which is worked (for there are several seams here) is almost perpendicular and from 5 to 19 feet thick. It is greatly interstratified with bone and shale and most of the mine product is washed before being used. There are no mining machines used. About 200 men are employed at regular Montana coal-mining wages. During 1904 the production was between 60,000 and 70,000 tons.
248
MINING MAGAZINE
r Electric, or Horr, has been the largest coke producing place in Montana, but, owing to a change in local management and labor trouble, neither the coke-ovens nor the mines have operated since last August. The mines are located at Aldridge, about three miles from the coke-ovens, and have four workable beds. A tramway about a mile long, with a maximum grade of 42 per cent., is built from Electric, the location of the coke-ovens, to the top of the mountain. The cars running on this tramway are pulled by an electric hoist. From the upper end of the tramway, on the summit, a trolley line runs to the mines.
Coal Property near Forsyth, Mont.
This field is much faulted and some semi-anthracite coal is found. Four entries have been driven: No. 1, about
5.000 feet; No. 3, the main entry, about 7,000; No. 2, over 4,000; No. 4, about
3.000 feet. The coal is hauled from the main entry to the tipple by an electric motor. The washer is located; below the tipple and the product carried (by water in sluice boxes) to the large bunkers near the coke-ovens, a distance of over two miles. There are 250 coke-ovens at Electric and a coke extractor is used to pull the ovens. There is also an excellent electric power
plant. The product of these mines in 1904 was about 80,000 tons, but they yielded over 117,000 tons in 1903. The number of men employed at both mines and ovens was between 300 and 400, the usual wages being paid. There are two other mines of minor importance across the Yellowstone River from Electric.
The mines near Lewiston are all in the Judith Basin field and the product is a good grade of lignite. Though the first development dates back not more than six years, much progress has been made. The city of Lewiston is entirely supplied by these mines; since a railroad now connects it with many outside villages, the production for 1905 will doubtless be quite large. The Spring Creek Coal Company is the largest operator; its mines are about three miles from Lewiston. The output for 1904 was about 40,000 tons. From 10 to 25 men were employed in mining and hauling the product. There are several smaller mines, but statistics are not obtainable.
The mines around Miles City and through Custer County belong to the Plains Cretaceous and yield nothing but lignite. However, Custer County is one of the best lignite counties in the State. Miles City, the countv-seat, is situated in the center of the great lignite area of the eastern part of Montana. There are several mines operating in this vicinity, and all are in flourishing condition. The seams vary from 6 to 18 feet in thickness; the lignite is used for fuel in the country districts. The best mine is about three miles from Miles City; the seam is between 4 and 5 feet thick. Most of the citizens of Miles City use this as a fuel. The output of the mines of the vicinity dur-
MQJMA FILE
THE MONTANA COAL FIELDS
249
Calorific Tests, Boiler Efficiencies, and Marketable Values.
County.
Price per ton.
B. T. U. per lb.
Boiler
Efficiency.
Locality.
Carbon ........................
$4.50*
10,255
93-4
Red Lodge
Cascade ......................
450
10,406
52.0
Belt
Custer ..........................
3.00
7,721
60.5
Miles City
Gallatin ......................
3-40
11,090
465
Chestnut
Lewis & Clark...........
4.00
10,200
Augusta
Madison .....................
4.00
Cameron
Meagher .....................
3.00
10,545
78.3
Thirteen-Mile Creek
Park ............................
6.00
12,984
100.0
Aldridge
Ravalli ........................
Rosebud ......................
3.00
3.00
Darby
Forsyth
* $6.00 in Missoula.
Output by Counties, of Coal, Lignite, and Coke in 1904.
Counties.
Coal.
Lignite.
Coke.
Principal Mines.
Carbon . Cascade
Choteau. Custer ..
Dawson .. Deerlodge Fergus ... Gallatin . Granite ..
Lewis & Clark.
Madison ..........
Meagher .........
Park ..................
485.000
740.000
105,000
100 100 to 200 100 87,000
8,000 to 10,000
8.000
10.000 to 15,000
10.000 to 15,000 100 to 500
40.000
7,000
15,000*
Ravalli . Rosebud Teton . . Valley .
100
250
100
400
Red Lodge, Gebo, Bear Creek, Bridger.
Sand Coulee, Stocket and Beet.
Near Havre
Miles City, Ekalaka,
Powderville Glendive Anaconda Lewiston Chestnut, Storrs Drummond, New Chicago Augusta Cameron, Ennis Sixteen-Mile Creek Cokedale, Electric, Aldridge Darby Forsyth Choteau Culbertson
*Shut down since August, 1904. Produced about 40,000 tons of coke in 1003 Chemical Analyses of Montana Coals and Lignites.
County.
Moisture.
Volatile
Comb.
Matter.
Fixed
Carbon.
Ash.
Total.
Locality.
Carbon ....................................
2.42 >-•
36701
50.054
10.823
99.998
Red Lodge
Cascade ..................................
4-23
22.65
55-00
18.12
100.00
Belt
Custer ......................................
I4-752
34-439
42,928
7.88
99.999
Miles City
Gallatin ...................................
8.64
23.10
56.18
18.08
100.00
Chestnut
Deer Lodge ..........................
5.00
45.00
35-00
1500
100.00
Anaconda
Granite ....................................
8.25
41-531
36.117
14.101
99.999
Near Drummond
Lewis & Clark......................
1763
40.77
45-914
U-552
99.999
Augusta
Madison (Semi-Anthracitel
5.282
5-634
84.671
4.412
99.999
Cameron
Meagher .................................
1.207
47.28
43-728
7-784
99.999
Thirteen-Mile Creek
Park .........................................
■97
30.60
58.00
10-43
100.00
Aldridge
Ravalli .....................................
17.68
19.29
38.803
24.226
99.999
Darby
Rosebud ..................................
9.516
38.212
44.724
7-547
99.999
Forsyth
Teton .......................................
Valley ......................................
9.077
37-866
39-693
13-364
100.000
Birch Creek Mine
Flathead ..................................
1.27
52.077
35-415
11.237
99.999
North Fork
Missoula .................................
9-3t
41.17
39.60
9.92
100.00
Missoula
MINING MAGAZINE
ing 1904 was between 10,000 and 15,- 000 tons. This lignite sells for $2.50 to $2.80 per ton, delivered in Miles City. At the dump it sells for 90 cents to $1.00 per ton.
There are several good beds of lignite in Dawson County, a few miles from Glendive, measuring from 18 to 22 feet in thickness. Lignite, as a rule, is easily mined, and steps are being taken to briquette the Plains lignite of Montana and thereby open all the vast beds found throughout the-eastern half of the State. Glendive, Wibaux, Culbertson, and other towns in this county are supplied with good lignite fuel from neighboring beds. The output for 1904 would exceed 15,000 tons.
In Rosebud County, mines nine miles from Forsyth supply that city with a good grade of lignite; seams 8 to 10 feet thick near Darby, in Ravalli County, are now competing with outside coal in Hamilton. Havre and Fort
Benton, in Choteau County, as well as Choteau, Teton County, are all supplied with fuel from neighboring lignite beds. Augusta, Lewis and Clark County, has some good beds of bituminous coal, and considerable development work has been done during the past year.
There are many other places in the State where good coal is found, but most of them are some distance from a railroad and it will be some time before they are generally known. With natural fuel in almost every county, together with her many other natural resources, Montana is rightly named “the Treasure State.’’ The output of coal, lignite and coke, together with chemical analyses and other data, will be found in the following tables. The bibliography of the Montana coalfields, published in the Mining Digest, page 261 covers the principal literature of the subject.
Tipple at Bridger, Mont.
THE MINING DIGEST
261
THE MONTANA COAL FIELDS
A BIBLIOGRAPHY J. P. Rowe
1. The Flora of the Great Falls Coal Field. By J. S. Newberry. Amer. Jl. of Science, March, 1891.
2. The Rocky Mountain Coal Fields. By L. S. Storrs. U. S. Geol. Survey, 22nd Annual Report. Vol. 3.
3. The Cinnabar and Bozeman Coal Fields of Montana. By W. H. Weed. Bulletin Geol. Soc. of America, Vol. 2; March, 1891.
4. The Fort Benton Folio. U. S. Geological Survey.
5. The Three Forks Folio. U. S. Geological Survey.
6. The Livingston Folio. U. S. Geological Survey.
7. The Little Belt Mountains Folio. U. S. Geological Survey.
8. Two Montana Coal Fields. By W. H. Weed. Bulletin Geol. Soc. of America, Vol. 3; Jan. 28, 1892.
9. The Laramie and the Overlying Liv-
ACTION, INFLUENCE AND CONTROL OF THE ROOF IN LONG- WALL WORKINGS H. W. G. Halbaum Institution of Mg. Eng., June II, 1904 The author discusses in detail the conditions of the roof in long-wall workings, and best method of controlling its actions in various cases. He deals with the influence of the roof and the reaction on the roof itself. According to him, the direction of the total action on the roof is oblique; hence, the action of the roof, the reaction upon the roof and the fracture produced in the roof by that reaction all lie in the same straight line. Therefore, lines of fracture in the long-wall roof are deflected from the true vertical line and cleave in the direction of the limit of the draw. The obliquity of the line of fracture accounts for many things which could not be reconciled in the theory of vertical fractures.
He explains in detail, by diagrams, the
ingston Formation. By W. H. Weed. U.
S. Geol. Survey, Bulletin No. 105.
10. Correlation Papers. The Cretaceous. U. S. Geol. Survey, Bulletin No. 82.
11. The Great Falls Coal Field, Montana. By J. S. Newberry. Sch. of Mines Quart. July, 1887.
12. The Tenth Census of the U. S., Vol. 15, 1880, containing: Bituminous Coal and Lignite of the Northwest, by R. Pumpelly; Relation of the Coal of Montana to the Older Rocks, by W. M. Davis; Montana Coal Fields, by Geo. H. Eldrige.
13. Seventh Report of the Bureau of Agriculture, Labor, and Industry of Montana.
14. Eighth Report of the Bureau of Agriculture, Labor, and Industry of Montana.
15. Some Montana Coal Fields. By J. P. Rowe. Amer. Geologist, Dec., 1903.
16. A Bituminous Coal Breaker in Montana. By L. Stockett. Mg. World, March 26th, 1904.
17. Fourth Annual Report of the Montana Inspector of Mines, 1905.
aa/ajJ
transmission of the pressure, the weightings and the bending of the roof. The locking of the roof, which often happens in long-wall workings, is explained by the existence of a strong lateral thrust which holds a great body of strata securely gripped and prevents it from falling. The action of the timber, according to the author, is merely to prevent the fragments of the roof and stratum from falling out and causing injury to the workers. The timber can never support the weight above the bridge at the roof line, as it is merely a system of centers, so to speak, the object of which is to maintain the constituent parts of the bridge in their relative positions. The purpose of the timbering is secured if the fragments of the shattered roof stratum are maintained in their relative positions.
In regard to the successful working of long-wall, the author maintains that it demands a roof only moderately strong, notwithstanding the assertion so frequently made in text-books that long-wall working
262
MINING MAGAZINE
requires a very strong roof. As a matter of fact, a very strong roof is more difficult to control than a roof which is distinctly tender. If in some seams it be thick and free from dirt partings, such a roof many render any system of pure long-wall a wholly objectionable mode of working. The author considers the various methods for the control of the roof in detail, dealing with the control by a direction of working, if the angle is with the line of dip, or with the line of cleavage. He then deals with the method of control by the rate of advance, by the arrangement of back walls and of roads, as well as by the system of timbering.
In regard to the latter, in order to get the double result of having props sufficiently strong and at the same time sufficiently elastic, the only way known to the author by which this double purpose may be obtained
with any degree of success is stated to be the employment of tapered or “chamfered” props, which rest on thick soles and are capped by substantial lids. The soles may also be bedded on a thin layer of dirt. As the roof slowly descends the prop head is forced through its lid. The foot is forced through the sole. The layer of mine dirt is ground out and the prop itself spreads out its fibers at either end. The roof is thus enabled to sink through several inches without breaking the prop itself, and without appreciably decreasing its efficiency as a support of the disintegrated roof stratum. For the timber of the main roads, especially main air-ways, he states it is possible that the Gothic or “herring-bone system of timbering a bad roof is not depreciated as fully as it deserves. The practice of carrying out this system of timbering is described.
COAL DUST AND EXPLOSIONS
Thomas A. Jackson Coal & Timber, Jan. 1905 The serious mine explosions that have occurred during the last few years—particularly in America—which have been attributed to the ignition of coal dust, have raised new doubts in the minds of some who have given the matter considerable thought, as to just the best methods to prevent similar occurrences. The author, writing from western Pennsylvania, probably gives the consensus of opinion of mining men in that section on this important subject. For many years the exact relation of dust and gas in mine explosions was not known, but recently careful investigation seems to have separated the two agents in explosions. However, there is a strong conviction that the presence of a certain percentage of gas greatly contributes to the chances of dust igniting on coming in contact with flame.
As evidence of an explosion of dust, the coked coal on timbers, roof and sides of mine workings is especially noted. The consequences of the explosion, including loss of life and property and possibly an underground fire, are results which might equally
well follow an ignition of gas. The extension of an initial explosion is considered at times inevitable on account of the general distribution of dust which accumulates on anything offering support. The force of an explosion of fire damp and air, when mixed in the most explosive proportion, is calculated to be 13.8 atmospheres steady pressure, or many times that of a hurricane moving at the rate of 100 miles an hour. When confined in narrow mine workings this force might be described as terrific.
Since the introduction of mining machines, Mr. Jackson considers that more dust is made than previously—the chain machine in undercutting producing fine dust which fills the air. Naked lights are used daily in the presence of such conditions without any serious results, to the author’s knowledge, although he cites a significant case of a man holding his open light close to an undercut, just after it was finished, resulting in the fine particles of dust going off like a flash of blasting powder. No evidence of gas had been found in the working place.
Attention is drawn to references in the reports of British mine inspectors to explosions, some of which are briefly cited.
Books, Pamphlets and Ephemera from the University of Montana
