sriiMAIMNK TrXNKLINiJ 221 



means of this pipe all the obnoxious gases from the furnace 

 were removed from the air-chamber. After the riveting was 

 finished, the shield was brought to its right position for line 

 and grade, the hydraulic jacks and valves put in place, and the 

 necessary connections made. On Nov. 24 word was received 

 thr.t the work on the New York side was to be pushed with all 

 possible speed, and a force was at once organized of three 

 gangs, working in eight-hour shifts. More rings were built on 

 the ten rings already anchored in the rock, until the tunnel 

 lining was brought within the tail-end of the shield. 



The shield was now advanced until it was necessary to 

 disturb the bulkhead, the remaining bench ahead of the shield 

 being blasted out as the shield progressed. The most difficult 

 part of the work was now reached, for at the point where the 

 shield entered the soft, black mud on top there still remained 

 about 12 ft. of hard rock in the bottom, as the dip of this vein 

 was over 40 toward Long Island. Blasting had therefore to 

 M tinned in the bottom pockets of the shield after the top 

 had entered the much-softened material. As soon as the bulk- 

 head was passed it was with great difficulty that the bottom 

 pockets could be kept clear of the black slush from overhead. 

 The material had become so softened along the rock face that 

 it was almost impossible to confine it, and several rushes of 

 inflowing material occurred, until finally an open connection 

 with the river was established, and the tunnel was visited by 

 crabs and mussels, together with boulders, old boots and shoes, 

 brick, and tinware, direct from the river bottom. Notwith- 

 standing these adverse circumstances the work was still pro- 

 j nosing, although in 45 Ibs. of compressed air, which was now 

 escaping through the heading, and causing a very violent 

 ebullition on the river surface. This upward current of air 

 held in check the downward current of water, so that no effort* 

 were made to prevent ite escape. On Dec. 13 the shield finally 

 cleared the rock and was now fully entered into the soft, black 

 mud. The main difficulty was now surmounted, the work 



