120 THE COLLIERY GUARDIAN. January 21, 1916. This outburst detached about 22,000 cu. ft. of coal, but the volume of gas was less than in the previous out- bursts. In hole 2 this outburst was preceded three hours by a slight drop in pressure, and quickly followed by a sharp descent of about 30 lb., then a rise to original pres- sure, and another sharp drop of less amount than the first, after which the pressure finally rose to 115 lb., where it remained into the next day. Closely similar oscillations were shown in hole 1 after the outburst, the pressures varying from 50 lb. to 28 lb. Some of these changes were simultaneous and of similar amounts. On the afternoon of the next day there was a fourth small outburst of gas. Three hours altar this outburst both tubes showed equal falls of pressure and a series of oscillations. After this the pressure in hole 2 rose a trifle, and then remained stationary for several days. The pressure in hole 2, however, rapidly diminished after the oscillations to about 101b., and then diminished very gradually for several days. From the connection of the oscillations of pressure with the gas outbursts Maquet came to the conclusion that a coal bed with its gas-filled pores acts as an elastic body, and transmits wave movements due to pressure variations. He suggests that there are centres of pres- sure of differing degree and intermediate zones of varying pressure in unstable equilibrium, so that the trans- mission of waves of varying pressure would not be uniform in speed or amount in all directions. These centres of pressure of varying degree would account for the different pressures found in the holes at different pointe. Ghysen did not accept this hypothesis, but held that the pressure of gas in pores of coal is very high and in stable equilibrium except when cracks give outlet or movement. He explained the rapid drop in pressure in hole 1 as due to a crack opened by mining in the rise, and maintained that such cracks started the first out- burst. Finally, the crack drained off the gas until the pressure dropped to 45 lb. It did not reach hole 2, but the pressure of the latter was relieved momentarily at the time of the second outburst, and following the third and fourth. These breakings of the coal finally led to the declines and ultimate ceasing of pressure in hole 1. Gas Pressure in Coal Beds in France. In 1893, A. Simon, chief engineer of the Lievin mine, tested the pressure of gas in solid coal by experiments similar to those of Wood and others. The tubes were inserted far out in the workings, at a depth of about 1,560 ft. The coal contains 30 per cent, of volatile matter, and the mine is uniformly gaseous throughout. Two-inch holes were bored into the headings, and fitted with copper tubing 0'4 in. in diameter, reaching to within 7-J in. of the bottom. The tamping, damp clay, was of different lengths. Pressures were measured with a gauge, and volumes of gas with a meter. Two series of holes were tried, one in virgin coal, the other in an area where there may have been some fissuring from mining. The first series of holes was about 820 ft. ahead of the mining, in a gangway, in the Frederic bed, that had been made in the foregoing six months. At that place the bed is about 4| ft. thick, and the test was near a fault where the strata dip 23degs. Six holes were drilled into the side of the gangway to depths of 30| ft. to 39 j ft., with 13 ft. or more of tamping. Hole 1 was first; 80 ft. farther in was No. 5; and then at intervals of 20 ft. to 25 ft. Nos. 2, 4, and 3, the latter being at the end of the gangway. It was found that the pressure was not closely related to the length of tamping, but that the volume of gas for a given pressure was in pro- portion to the vacant space at the bottom of the hole. The pressures (lb. per square inch) in holes 2, 3, and 5, all with about 13 ft. of tamping, were as follow, the figures in parentheses indicating the pressure at the end of two years :—Hole 2, 77 lb. (59 lb.); hole 3, 59 lb. (35 lb.); hole 5, 80 lb. (52| lb.) The maximum pressure was attained in four to six days in most cases, but sometimes after the cock had been closed the pressure would rise to the maximum in a few hours. The observations show how slowly the coal gives up its gas, or, in other words, its slight perme- ability. That the roof is only slightly permeable also was proved by a test hole in which a pressure of only 1’4 lb. per square inch was developed. The other series of teste was in the Alfred bed at about the same depth as the first. The coal is about 7 ft. thick, contains 33 per cent, volatile matter, and has a hard floor, but a friable roof. The holes were made diagonally into a face at the end of an area of active mining. The results were as follow (figures in parentheses show pressure at the end of three months) :—Hole 1, 64J lb. (491b.); hole 2, 85| lb. (591b.); hole 3, 96| lb. (591b.); It should be noted that the difference in maximum pres- sure in holes 2’and 3 is small, notwithstanding the great difference in coal surface exposed. This relation is variable. The rapid diminution of pressure in three months was due to the greater permeability of the bed and to some fissuring from the advancing workings. The gas in this series in hole 3 showed higher pressure than in the holes in 'the Frederic bed, and afforded over 0'35 cu. ft. a minute, or nearly 50 times as much in relative volume when the small area of coal exposed (1| square feet) is considered. The maximum pressure observed in the mine was 105 lb. per square inch in a hole 39 ft. deep, and is very much less than those recorded by Wood in his teste in an English mine, and by other observers in French and Belgian mines. It was found that the variation in pressure was not uniform, and although it increased with depth of hole in most eases, the results do not accord with Mallard’s formula. The long gangway in the Frederic bed where the six test holes were made drained the gas very slowly for about two years, and the pressure decreased only about one-third in that time. Mallard’s view that the volume of gas increased with pressure was not sustained by Simon’s tests, which showed that with practically the same pressures the gas volume per square foot of coal exposed was 50 times as much in the Alfred bed, which is disturbed, as in. the Frederic bed, which is undisturbed. In 1907, Morin made some determinations of pressure of gas in coal in a gangway down the dip in virgin coal of the Leonard bed, where the volume of gas in the return air current was 31 cu. ft. per minute. Into this bed boreholes were driven to various depths. A copper tube was inserted into each borehole to within 8 in. of the bottom. The space about the tube was then care- fully tamped with clay to within 4 ft. of the bottom. In one of these holes, which was 25 ft. deep, the pressure of the gas was 10-6 lb. per square inch, diminishing to 7 lb. two weeks later. The volume of gas given off at 7 lb. pressure was 23| cu. ft. per minute from an exposed surface of 2| square feet. After allowing this gas to flow freely for two hours, the pressure gauge was again attached, and in 45 minutes the gas regained its original Canadian Northern Railway’s Coal Dock, Port Arthur (Ont.) pressure. The pressure remained at this point for three weeks, but a week later it diminished to 4 lb., and still later to less. Compared with the results obtained by Simon in 1893, the pressures were lower, the flow of gas more copious, and the renewal of pressure more rapid. Further teste of the same holes indicated a failing pressure, but with- out corresponding decrease in volume, which appears to prove that, when gas drainage begins, the loss is slow at first and then rapidly increases as the drainage becomes well established. In investigating the cause of several coal and gas outbursts at St. Etienne, Petit (see Colliery Guardian, Oct. 15, 1895, p. 733) made some teste of pressure of gas in the coal similar to those made by Wood, Schorn, Maquet, Simon, and others. The bed tested was No. 13, which averages about 14 ft. thick, and is 380 ft. below sea level. Petit used iron tubes, 0’43 in. in diameter and 3 ft. to 23 ft. long, set in holes 2'6 in. in diameter. In order to have a uniform exposure of 3'164 square feet of coal surface in all tests, he placed each tube 6 in. from the bottom of the hole in coal, and made the space free from tamping 3 ft. 3jin. long. The number of holes tested was 135, and pressures were taken for every metre (3'28 ft.). In general it was found that the pressure and gas volume increased with depth of holes and with time, but at irregular rates. In the shallow holes up to 10 ft. deep ■the pressures were as low as | lb. to the square inch, but in some the pressure was as high as 5J lb. In holes 23 ft. deep the pressure varied from 31b. to 181b., but in some of them it was as high as 44 lb. The time required to give maximum pressures varied. For holes of the same depth the pressure was much less in stalls than in headings. To test the drainage possibilities of a hole, a boring 15 ft. deep, with an initial gas pressure of 441b. to the square inch, was left open for six weeks. The pressure was reduced only to 31'3 lb., indicating that a hole is not very efficacious in drainage of gas. In one series of tests the holes were bored in the face of a working heading as it progressed into the solid. In one hole of the series, a pressure of 17 lb. was observed, although the pressures at previous stages of progress had been less than lib. However, adjoining holes in the same heading gave low pressures, 31b. or less, which indicated that the high pressure was due to a crevice leading back into the more solid coal. This experiment was repeated with similar results. Petit’s conclusions were as follow :—(1) High pres- sure is manifested where coal is exceptionally compact; (2) as a rule, pressure in coal for the first 3 ft. from the face is slight, as the gas is draining off rapidly by cracks caused by blasting and the heaving of the strata; (3) pressure and volume increase with depth, but irregularly, the rate depending on the compactness of the coal; (4) districts of high pressure are very irregular in extent because the permeability of coal is variable; (5) the time for equal pressures varies, the main factor being perme- ability until the final equilibrium is established; (6) holes bored ahead of workings will not greatly decrease pressure, nor drain off much gas. Gas Pressure in Coal in Austrian and German Mines. The Austrian commission (1893) made a number of tests of gas pressure in coal and found in general a rapid increase as the test holes were made deeper and deeper. However, in a 24|-ft. hole at Rossitz the pressure was 821b. to the square inch, and at Karwin Ostrau, a 21|-ft. hole gave a pressure of 142Jlb. A 13-ft. borehole in a newly opened section of the Hibernia mine in "Westphalia showed a gas pressure of 218 lb. to the square inch. (To be continued.) CANADIAN NORTHERN DOCKS AT PORT ARTHUR (ONT.)? Port Arthur, Ontario, claims the finest coal docks on the Canadian lakes. They were finished recently, and have been built on the newest lines of construction. Before navigation closes, they will handle over 1,500,000 tons, and the total may run as high as 2,000,000. Built by the Canadian Northern Railway, they were opened with one set of clams in 1906, the capacity at that time being 22,000 tons of hard, and 250,000 tons of soft coal. In 1913 this capacity was increased to 160,000 tons of hard coal and 500,000 tons of soft coal. Last year a fourth clam of two tons capacity, capable of handling three thousand tons per day of 10 hours, was added, and is now in operation. This enables the dock to load into railroad cars at the rate of 8,400 sons daily. The hard coal is contained in sheds, which are built of steel and concrete, and each have 100,000 tons capacity. It is possible to ship independently from any one; and all may ship together. A feature of these sheds for hard coal is that they have concrete con- duits for the loading belts to run in, thus greatly lessening the danger of fire. The whole dock is modern in construction, and is run by elec- tricity. It has three sets of track- weighing scales, which weigh the empties in, and the loaded cars out. It is possible to weigh loaded cars outward and empties inward at the same time. This feature is unique in coal docks at the head of the Canadian lakes. * Black Diamond. COAL TRAFFIC ON RAILWAYS AND CANALS IN 1914.* The following table shows the coal and coke carried by the various systems of railway, canal, and other inland navigation companies from colliery districts in the United Kingdom in 1914 and 1913 :— Name of railway. Railways, England a- d Wales Furness (coal) Great Cent'al (coal and coke) ... Great Northern (coal) Great Western (coal and coke)... Hull and Barnsley (coal and coke) Lancashire and Yorkshire (coal and coke) London and North-Western (coal) Maryport and Carlisle (coal and eoke) Midland(eoalandcoke, excepting gas coke) • North-Eastern (coal and coke)... North Staffordshire (coal and coke) South Yorkshire Joint Line Committee (coal and coke) Taff Vale (coal and coke) Railways, Scotland:— Caledonian (coal and coke) Glasgow and South - "Western (coal) North British (coal and coke) ... Railways, Ireland:— Cavan and Leitrim (coal) Great Southern and Western (coal) Canals, England:— Aire and Calder Navigation (coal and coke) Birmingham Canal Navigations (coal and coke) Bridgewater Canals (coal, in- cluding a small quantity of coke) Leeds and Liverpool Canal Com- pany (coal, including a small quantity of coke) Shropshire Union Canal (coal and coke) 1913. 1914. Tons. Tons. 164,001 ... 153,265 14,920,952 ... 13,583,303 8,739,556 ... 7,947,661 22,142,823 ... 20,521,077 2,559,117* ... 2,110,753* 9,396,275 ... 8/ 26,551 23,496,970 ... 21,351,254 357,744 ... 330,611 27,834,531 ... 26,593,971 41,501,521 ... 37,435,639 3,622,149 ... 3,596,447 997,628 ... 831,181 15,682,640 ... 14,872,879 13,026,909 ... 11,989,693 3,500,225 ... 3,465,686 21,233,792 ... 17,540,201+ 7,892 ... 7,282 5,009 ... 5,743 2.563,067 ... 2,064,732 3,640,221 ... 3,448,554 401,103 ... 375,304 794,487 ... 751,732 15,257 ... 16,610 189,755 ... 165,190 186,260 ... 180,912 112,293 ... 116,038 70,064 ... 60,309 25,364 ... 16,908 135 ... Nil itity were conveyed to ons to Methil Docks for Staffordshire and Worcester- shire Canal (coal and coke) ... Trent and Mersey Navigation (coal and eoke) Canals, Scotland:— Forth and Clyde Canal (coal and coke) Monkland Canal (coal and coke) Union Canal (coal and coke) Canal, Ireland:— Grand Canal (coal) * Including patent fuel. + 1,823,231 tons of this quar Burntisland Dock and 2,456,375 t shipment. * From Part III. of the General Report on Mines and Quarries, 1914.