THE RHON 7 DDA COLLIERY. 



261 



ing which time Mr. James Barr has been in charge. The seain 

 being worked is the Great Northern, a section of which is 

 shown in Fig. 168, but only the lower Tft. lOin. are worked 

 at present. The coal is not so good as that from the Borehole 

 seam, but it breaks up into large blocks. The workings are 

 reached through a tunnel (Fig. 169). The first few yards, 

 in loose soil and rock, are bricked up; further in, timber sup- 

 ports are used, till the rock stands by itself. 



This is a machine mine, the equipment consisting of two 

 Sullivan long-wall machines, and two Goodman chain-breast 

 machines, both driven by electricity. The Sullivan has the 

 advantage of working continuously across the face when once 



Fig. 167. Boring a Shothole. 



the sumpiiig cut is in, whereas the Goodman is only fed for- 

 ward, so has to be withdrawn for each cut. But there are 

 certain constructional features about the Sullivan machine 

 as put on the market which the manufacturers would do well 

 tc remedy, instead of leaving it for the users to alter. The upper 

 ball bearings of the armature shaft have had to be replaced by 

 ordinary brass bearings, as the balls were found to cut grooves 

 in the sleeve surrounding them ; this caused the bearings to 

 become heated. The heavy armature being arranged verti- 

 cally, its weight has to be supported on the lower bearing, 

 which is about two inches in diameter ; consequently much 



