SUBMARINE TUNNEL1M, 



the tunnel. The water would then accumulate in this pocket, 

 softening up fresh mat* rial on the sides until it had gained a 

 suHicient head to burst through the dam which confined it, 

 when it would come rushing int> tlie tunnel, carrying with it 

 large quantities of the softened matt-rial. These rushes were 

 accompanied by a loud bubbling sound that quite mystified the 

 mm, which was, of course, the sound of the air displacing the 

 water in the cavity. As soon as the pocket had emptied itself, 

 for a time the trouble was over, until with the falling of more 

 material the outlet was again closed and the operation was 

 repeated. These rushes of water, with the accompanying 

 sound of the bubbling air, soon became more and more alarming 

 to the men. The cavity was constantly increasing in size, and 

 extending up toward the river-bed. Each recurrence would 

 now send the men running for the shaft, by no means certain 

 that the river had not at last made a connection with the 

 tunnel. 



All work in the small drift was abandoned, and on Dec. 31 

 a bulkhead was hurriedly constructed at the face to prevent the 

 threatened flooding of the shaft. Up to this time over 25 yards 

 of material had been washed into the tunnel, all of which had 

 come from along the rock face. With the river-bed only 45 ft. 

 above the tunnel-roof, there is every reason to believe that this 

 bulkhead was put in none too soon, and a connection with the 

 river narrowly averted. The bulkhead was well packed with 

 hay to prevent, as much as possible, further washing of the 

 material, and a discussion was now entered into as to the 

 method of future procedure. The contractors were in favor of 

 abandoning the heading and returning to the shaft, to sink to a 

 lower level and start anew in hopes of meeting more favorable 

 conditions at a greater depth. There had l>een a somewhat 

 similar experience on the Croton Aqueduct, where that tunnel 

 passes under the Harlem River. Soft material had been en- 

 countered on the first established level, which proved so trouble- 

 some that after two or three unsuccessful attempts had been 



