BORING 



451 



the solidity of a thickness of 12 feet of coal on each sido of the advancing rod, it is 

 usual to bore three holes, one in the line of the heading, and two flank holes, which 

 can either be driven frhni the corners, or as shown in the sketch. The flank holes aro 



194 



UPPOSED OLD HEADING 



bored at such an angle as will enable them to detect, within a given distance, the pre- 

 sence of any old works which may be in advance of them. Thus it will be seen on 

 fig. 194, that the direction of the hole is such that no old head could exist without 

 being discovered by the borers. 



Where no extraordinary pressure exists, it is usual for the centre holes to be bored 

 a distance of about 9 yards, after which the heading is advanced, say 3 yards farther, 

 by ordinary mining ; hence it will be seen that the use of the centre hole can bo con- 

 tinued, while new flank or side holes have to be bored every few yards. The usual 

 size of the holes driven for proving old works is about 1^ inch diameter, and the cost 

 of boring varies from Qd. to 2s. per yard, according to the length of the hole. 



In some cases, where a heavy pressure of water has to be encountered, the rush of 

 water is so rapid, that it is impossible for the borers to stem its progress by means 

 of plugs. 



In an important boring conducted under the superintendence of the writer, the 

 arrangement shown by fig. 195 was adopted. Here the bore-rod nearest to the handle 



195 



is of turned stool, working through a stuffing-box, s, which is attached to a tube, the 

 end of the tube being wedged tightly into the borehole. Near the stuffing-box is a 

 short elbow, in which is a valve or cock. When the old workings are pricked, and 

 the water is reached, the cock is closed to prevent the occurrence of any serious 

 consequences. About the centre of the tube a disc-bracket is placed, bearing against 

 two beams, one above, the other below the tube, the end of these beams being wedged 

 tightly into the sides of the coal heading. The adoption of this mode not only ensures 

 safety, but conduces to the accuracy with which the hole is driven. 



Norton's Patent Well Tubes. A method of well sinking, patented by Mr. J. L. 

 Norton, of London, by which a supply of water can be obtained in a very short space 

 of time, provided the geological conditions of the part selected for the sinking aro 

 favourable, deserves notice. 



The arrangement consists of a wrought iron tube, about 11 feet long and 1^- to 3 



