Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 Excerpt: ...that there is a "back" skirting, the object of which has already been stated, leading to the return airway of the district. VOL. III. G Extraction of Large Pillars.--Fig. 83 represents in detail a method adopted in working off some large pillars, 71 yards by 47 yards centre to centre, or 66 yards by 44 yards of coal, the section of the seam being as follows: Ft. In. Top coal (unworked)...16 Good coal..... 4 i,, The depth from the surface was about 900 feet. The roof was not good, and did not allow of long juds being driven. The arrows denote the direction in which the juds were driven. The pillars were skirted along the bottom end and the pillar to be worked jenkined up its full length and a skirting driven along its top end, the pillar being judded from this skirting for a distance of about 22 yards, the two last juds of the row being driven up instead of down, a narrow place being set into the solid for a distance of about 10 yards for this purpose. A skirting was then driven (loose) alongside the bottom end of the fallen juds, and the same course of operations followed until the pillar was entirely removed. All jenkins and skirtings were driven narrow, viz. 2 yards in width. CHAPTER IV MODIFICATIONS OF THE BORD AND PILLAR SYSTEM SINGLE AND DOUBLE STALL; WIDE OR SQUARE WORK; THE METHOD OF WORKING "REARERS" Various Modifications.--The modifications which may now be considered of the bord and pillar system of working coal are: The single and double stall, by which thin seams and seams of moderate thickness, whether flat or inclined, are worked. The systems adopted in the United States of America and elsewhere of working thick seams which are highly inclined. The square or wide work system of working thick, flat seams. The modification kn...
"synopsis" may belong to another edition of this title.
