THE SYDNEY HARBOUR COLLIERY. 



141 



water running- down the side of the brickwork. The brickwork 

 is shorn back just above the curb, so as to form a channel for 

 the water. Two-inch down pipes lead the water to the bottom 

 of the shaft, from which, under ordinary working conditions, 

 it is filled with the muck; but should water accumulate, cwing 

 to a stoppage of sinking, then it was baled out in a 250 gallon 

 bucket, with a self-acting valve. They could only draw 80 

 buckets a shift. In the Jubilee shaft a feeder of water was 

 tapped at 600ft., which yielded 1200 gallons of water per hour, 

 and this had to be eventually dammed back with 53ft. of iron 

 tubbing. 



The wedging curbs of the tubbing, which are cast hollow, 

 are 2ft. Gin. wide; they were made extra wide, as the rock was 



Fig. 75. Iron Tubbing. 



