240 TUNNELING 



boring showed that sand mixed with loam and gravel would be 

 found for a depth of 26 ft., then would come 15 ft. of red clay, 

 and finally a layer of hard clay like that penetrated by the 

 shore end of the tunnel. About the middle of December the 

 contractors made another attempt to pump the shaft, but find- 

 ing that the water came in at the rate of 25 gallons a minute, 

 abandoned the attempt. In the latter part of February prepa- 

 rations were made to put an air-lock in the shaft and use 

 compressed air. Hardly had the work been begun by this 

 system, when, on April 20, 1893, a terrific easterly storm swept 

 the top of the crib bare of the buildings and machinery, and 

 drowned all but one of the 15 men at work there. 



This disaster delayed the work for some time, but in June 

 the contractors erected a new building and new machinery, and 

 resumed work. Very little progress was made ; and the air es- 

 caped so rapidly that it loosened the sand surrounding the 

 shaft and reduced the friction to such an extent that on July 

 28 the entire cylinder lifted bodily about 6 ft., and sand rushed 

 in, filling the lower part of the cylinder to within 45 ft. of the 

 lake surface. No further work was done by the contractors, 

 although they submitted a proposition to sink a steel cylinder 

 inside the cast-iron cylinder and extending from 5 ft. above 

 datum to 100 ft. below datum for $300 per ft. This proposi- 

 tion was refused by the city; and since work on the tunnel 

 proper has been abandoned by the contractors some time before, 

 as had already been described, the city suspended their contract 

 on Oct. 19. 



Op Oct. 30 a contract was made with Mr. Thos. Murphy, 

 of Milwaukee, Wis., to sink a steel cylinder inside the old iron 

 cylinder. The water was first pumped out of the old cylinder, 

 and a timber bulkhead built at the bottom. On this the steel 

 cylinder was built, and then the bulkhead was removed. Air 

 pressure was put on, and the excavation proceeded successfully 

 until the bottom layer of clay was met with, when all chances 

 for trouble ceased. 



