and engineering journal . shafts, while the other two are set offat an angle of 45 deg. to the right and left. Levels areset off every 300 ft. along the centre main road, whilecorresponding levels are set off from the east and west slantsat 425 ft. apart to correspond with the levels on the mainslant. Jburg, September 10, 1921. /HE MIMING AMD ENGINEERING JOURNAL. L9 In the levels stentons are cut through every 66 ft., andin the extraction of the coal approximately 33 ft. of coal istaken out and .33 ft. left standing, while these pillars areagain pierced by stentons at fit; ft.,
and engineering journal . shafts, while the other two are set offat an angle of 45 deg. to the right and left. Levels areset off every 300 ft. along the centre main road, whilecorresponding levels are set off from the east and west slantsat 425 ft. apart to correspond with the levels on the mainslant. Jburg, September 10, 1921. /HE MIMING AMD ENGINEERING JOURNAL. L9 In the levels stentons are cut through every 66 ft., andin the extraction of the coal approximately 33 ft. of coal istaken out and .33 ft. left standing, while these pillars areagain pierced by stentons at fit; ft., so that pillars •>?) ft. x66 ft. are left to support the roof. This practice is muchvaried, depending on conditions, and in some parts of bhimine pillars larger than the Size specified arc left standing. Coal-cutting machinery has been experimented with, butin no instance have the results equalled those obtainedfrom hand labour. The coal is drilled with Elliott or Con-queror hand-drilling machines, two natives being able to. Wankie Collieries.—A General View. drill sixteen holes to a depth of five feet comfortably forthe shifts work. Roughly 5 ft. 6 in. of the seam is takenout in the first operation, and the top coal dropped downafterwards. The explosive used is 60 per cent, gelignite. Some faults exist, especially in the eastern section ofthe mine, where the coal is thinner, one fault displacingthe coal 16 ft. With the exception of this large fault, nofaults over 8 ft. occur, some faults showing about a 2 The western section of the mine, where the coal isthicker, is free from this condition, the general conditionunderground being that a coal seam of excellent width and value exists and the unfavourable conditions mentioned as• e not set up difficulties in mining, and aretherefore an unimportant item in a coal deposit which hassuch immense possibilities. New Mine. Ah. the present colliery site is congested, which makesfurther expansion difficult, it was some t
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Keywords: ., bo, bookcentury1800, bookdecade1890, booksubjectmineralindustries
