Mr. Bubble on Mining Records. 323 



this manner, when the size of the winnings was increased to 15 yards, 

 the boards being driven 5 yards wide, and the walls or pillars being left 10 

 yards thick, the walls being holed at 22 yards, 2 yards wide, as in the former 

 case ; the proportion obtained from the seam being very nearly the same 

 as in the former case. This change of size in the winnings was not made 

 for the purpose of obtaining a greater produce in the first working of the 

 seam. But the notion of a future working of the pillars then began to be 

 entertained, and the increased size of the winnings was considered a more 

 favourable apportionment of the excavation and pillar for the attainment of 

 this object than the 12-yard winnings. 



A small isolated tract called the Threep-moor (see the Plan, Plate XV.) 

 was, however, wrought by reduced winnings, i. e. by 10-yard winnings, viz., 

 4 board and 6 wall, the walls being holed at 22 yards, as before ; by which 

 rrths or 45^ per cent, were obtained by the first working. This was then 

 considered to be about the maximum produce of the seam, attainable un- 

 der any mode of working. 



About this time, 1795, a plan of robbing, or partially working the pillars 

 of the Main Coal Seam, had been adopted by the late Mr. Thos. Barnes, 

 at Walker Colliery, which proving successful, was adopted at Bigge's-main 

 Colliery soon afterwards, and, subsequently, in Wallsend. This partial 

 plan of working the pillars consisted in forming the old workings into dis- 

 tricts of limited extent, of from ten to twenty acres, by pillaring and stow- 

 ing up the board-rooms and walls adjoining, to such an extent as was 

 deemed sufficient to prevent any creep which might occur from working 

 the pillars in the enclosed district, from extending to the adjoining pillars. 

 These artificial barriers were generally formed by stowing up two or three 

 boards in breadth, which, with the adjoining and intermediate coal walls, 

 gave a total breadth of 44 yards in the 12-yard winnings, and of 55 yards 

 in the 15-yard winnings. 



The districts so formed were not made of larger extent than it was pre- 

 sumed would stand without creeping, while the partial working of the pil- 

 lars was being accomplished. The preservation of the ventilation of the 

 workings within the prescribed district during that operation was indispen- 

 sable, as we had only naked candles for lights at that time. The system 



