is worked to the dip. Since at Pendleton the main cleat makes a relatively small angle with the strike, breaks in the roof tend to develop the more easily when the coal is worked either to the rise or to the dip than when worked "on end."

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The significant fact emerged in the evidence of the General Manager that most of the serious crumps at Pendleton Colliery have occurred when the Rams Seam was being worked end," and this in spite of the fact that the face is often stepped. A possible explanation for this advanced by Mr. Browne seems to us reasonable. It is that when the coal is worked "on end," the roof cannot fracture so readily as it does when the coal is worked to the rise, and, to a less extent, to the dip. The inevitable result is, therefore, that when the coal is worked "on end," an ever increasing weight comes on to the coal at the face, with the serious risk of a severe crump.

Prevention of Crumps.-If the foregoing is the true explanation of the cause of those serious crumps which involve the sudden uplift of the floor of the mine, it is obvious, in order to minimise the risk of their occurrence, that a method of working should be adopted which is likely to throw as little extra weight as possible upon the coal-face. In order to do this, we agree with the view advanced by Mr. Browne that the Rams Seam in the deep parts should be worked to the rise or to the dip, and preferably the former. In driving levels to open out the coal, it will be necessary no doubt to work temporarily " on end." Where it is known that the coal occurs in very narrow strips between faults it may be advisable to leave it unworked and in no case should the seam be worked in such manner as will ultimately result in there being a comparatively small pillar of coal between two areas of goaf as was the case when the crumps numbered 2, 4 and 5 on Plate 1 occurred. Experience at Pendleton, confirmed by that in mines abroad where crumps are violent and frequent, points clearly to the danger of winning coal at great depths from small pillars in old workings. A very strong roof and floor, which on general grounds may conduce to the safe and economical working of the mine under ordinary circumstances, may intensify the danger of serious crumps where considerable stretches of roof are left insufficiently supported in old workings, as in practice they must almost always be. If it were possible by hydraulic stowage or perfectly packed goaf to support the roof absolutely, and so prevent subsidence, it is evident that the risk we are considering would not arise, but in practice this is not possible. We are, therefore, driven to the conclusion that under conditions like those which prevail at Pendleton, the method of working should, wherever possible, avoid leaving isolated pillars of coal to be worked.

In all cases strong and closely-spaced chocks should be built as near to the face as is possible consistent with coal getting, and where it is found necessary to drive" on end " in order to

open out faces to be worked to the rise, such drivage should be as narrow as is possible, the area on either side of the tub road being solidly packed.

In conclusion we desire to express our thanks to all those who assisted us in our underground inspections and in our inquiry.

We have the honour to be,

Sir,

Your obedient Servants,

H. WALKER (Chairman),

W. S. BOULTON,

STEPHEN WALSH,

PERCY L. WOOD.

(62816-22) Wt. 4847-3735 1000 9/27 H. St. G. 71