THE RHONDDA COLLIERY. 267 



each tube may expand or contract independently of the others 

 without straining the boiler. The tubes are inclined at such an 

 angle as to admit of easy and rapid liberation, and ascent of 

 the steam generated in the tubes, and the circulation of water 

 is such as to maintain a uniform temperature in all parts ; 

 thereby reducing strains and leaks due to unequal expansion 

 and contraction. On account of the bend in the tubes it is not 

 so easy to look through and ascertain whether they are clean 

 as if they had been straight ; also the boiler would be improved 

 by having a larger water space in the upper drums. 



Northumberland Colliery. 



This colliery is owned by an English company, but is 

 leased to Mr.' F. It. Croft, and was managed by 

 Mr. J. Rice for 12 years. The original company sunk two 

 shafts about 20 years ago, one for about 500ft., the other for 

 25<)ft., in order to cut a Oft. seam supposed to have been found 



Fig. 172. Jeffrey Electric Chain Breast Machine. 



by a bore. But is they did not get the coal, they usd a dia- 

 mond drill for a further 50()ft., when they struck the borehole 

 seam, which at this place was found to be about 3ft. thick. 

 Besides these shafts a tunnel was driven into the side of the 

 hill on the Great Northern seam ; and this is the one now being 

 worked. The seam is about 15ft. high, but only 7ft. to 7ft. 

 Gin. of the coal is removed from the middle ; the top and bottom 

 coal being left for roof and floor respectively. The seam has a 

 splendid roof of conglomerate. 



There are two coal cutters at work in this colliery, one a 

 Jeffrey, the other a Goodman. The Jeffrey (Fig. 172), makes 

 a cut 6ft. deep and 3ft. 9in. wide, and is the lighter machine of 

 the two. The starter is at the rear of the machine, and a hand 

 wheel for revolving the chain when required to change picks is 

 at the side. The trolley on which the machine is mounted 

 when necessary to flit from one place to another is self-pro- 

 pelled by a chain from the machine, which passes round a 



