STANFORD MERTHYIt COLLIERY. 337 



The seam being worked is the bottom Greta seam_; it is 

 from 19ft. 5in. to 23ft. thick, but 220 yards from the surface 

 it splits, the upper division being 12ft. to 15ft. thick, while the 

 lower division is 4ft. Gin. to 6ft. thick. The split starts with 

 dirty coal, which gradually turns into shale, and finally gives 

 place to sandstone and conglomerate. 



The upper Greta seam is found on parts of the property, 

 but is not being worked. 



The colliery is worked from tunnels. The main tunnel is 

 an intake, and used as a haulage road by endless rope from 

 No. 4 level to the surface. The little tunnel serves as an in- 

 take and travelling way, and in the bottom section, from the 

 fifth to the fourth level, where the seam becomes steeper, cages 

 are used for raising the coal. Where levels cross the tunnels, 

 overcasts are used, as they are in the coal, which is easier to 

 excavate than rock, and gives some return towards the cost 

 of construction. Undercasts are used at the deeper crossings 

 when the seam splits, as this enables the lower split to be 

 prospected. 



In the steep portion of the little tunnel, where the cage 

 is used, the cage takes two skips, side by side, and as the long 

 rope has a spring in it which alters the position of the cage 

 when skips are run in and out of it, chairs were devised for the 

 cage to rest on. 



The endless rope in the main tunnel travels at the rate 

 of 4i miles per hour. The engine that drives it is a strongly 

 built duplex engine, with 22in. cylinders and 3ft. Gin stroke, 

 geared 7 to 1, which uses lOOlbs. steam pressure. The skips 

 are attached to the rope by Allan's screw clips. 



Jigs are sunk in advance of the workings with electric 

 winches, and are not constructed by stripping down cut- 

 throughs. The seam is not so steep as at East Greta, but 

 they use jig cages in places, though sometimes the driving 

 track has to be made flatter at the bottom end by raising the 

 track, so that the full cage can get a fair start. Jigs have 

 been worked by gravity, at as low an angle as 8 degrees, and 

 in one jig near the surface the empty cage has to be assisted 

 up by an electric hoist, as the angle is too flat for a dummy to 

 be effective. Boys work the brakes at the top of the jigs. Two 

 ropes are wound round one drum, which has a brake path in 

 the centre. The brake is a band fitted with wooden blocks. 



The bords are turned off from one side of a jig, the first 

 12 yards being narrow work. Oft. to 10ft. wide, then a cut- 

 through is made parallel to the jig, connecting the bords for 

 ventilation purposes. The bords are widened out to 8 yards. 

 The pillars left are strong enough to stand till worked, prior 



