LAMBTON B. COLLIERY. 



309 



soon as one cut across is finished, the machine is placed on a 

 trolly and conveyed to another face, while three holes are 

 drilled in the place just left, one in the middle and one at 

 each side, about 3ft. 9in. deep. The holes are drilled by a 

 hurdy-gurdy hand machine about six inches from the roof; 

 they are directed slightly upwards and sideways, so as to 

 give a lift to the shot. The coal being soft, the auger type of 

 drill works much quicker, and with less trouble, than the or- 

 dinary hammer and drill used for rock. A nich is made in the 



Fig. 198. Headgear of Downcast Shaft. 



roof about 18 inches from the face, into which one end of the 

 jack screw at the top of the standard fits. This standard is 

 made of two notched sides, and in these notches fit trunnions 

 fixed to the side of a nut. A threaded rod (at one end of which 

 the cutter is attached, while at the other is a handle), passes 

 through this nut. The turn of the handle not only causes 

 the bit to cut, but gives the screwed rod a positive feed for- 

 ward. When drilled, the three holes are charged, the centre 

 one with 5oz. of monobel, and the two back ends with 4oz. 

 Only one shot is fired at a time ; first the centre shot, and sub- 

 sequently the back ends in turn. The firing is done by an 

 electric Battery, of which they have two types, one by Davis, 

 of Derby, the other by Nobel. 



