"STONE ROLLS" in the BULLI COAL SEAM of 

 NEW SOUTH WALES. 



By W. G. Woolnough, d.sc, t\G s., Assistant Lecturer in 

 Geology and Mineralogy, University of Sydney. 



[Read before the Royal Society of N. S. Wales, July 6, 1910.] 



The various interruptions to the continuity of the coal in 

 those seams which are worked commercially have more 

 than academic interest. The constantly recurring industrial 

 disputes owe their origin, in no small measure, to the diffi- 

 culties experienced in framing satisfactory agreements for 

 the working of "deficiency places" where the miner cannot, 

 under ordinal v • ■inaiiiistunces, make what he considers a 

 fair living wage. In the Illawarra coalfield the chief causes 

 of such interruptions are faults, volcanic dykes, "wash- 

 outs," and " stone rolls." It is with the last of these that 

 this brief note deals. 



The descending section of the Illawarra Coal Measures 

 and associated rocks, so far as it concerns the present 

 question, is as follows (c./\ also fig. 6):— 



Basal Beds of Narrabeen Stage (Hawkesbury Series). 



Contemporaneously eroded junction Bulli Coal Seam. 



Bulli Coal Seam. 



Floor Shale of Bulli Seam. 



" Four-foot sandstone "—roof of the Four-foot seam. 



Four-foot seam. 



Floor Shale of Four-foot seam. 

 All these beds have a very gentle fall towards the west 

 at the rate of about 200 feet in a mile. 



The basal beds of the Narrabeen Stage consist of a 

 porous sandstone or conglomerate resting directly upon 

 the somewhat eroded surface of the Bulli Coal Measures. 



