WATER JET. 



401 



Small sheerlegs, fitted with blocks and falls, were erected 

 'midships, with a sufficient overhang to clear the side of tho 

 ship. 



About 50 feet of hose, fitted with a IJ-inch nozzle, was 

 attached to the delivery of the pump, and the suction-hose 

 passed into the sea. 



At the lower end or foot of the pile were fixed two staples 

 in which the nozzle was placed. At the end of the nozzle, below 

 the staples, a small line was secured, passed up outside the 

 staples, and held by the man directing the operations, so as to 

 keep the nozzle in its place. 



The pile suspended from the sheerlegs was then lowered to 

 its proper position, and on its touching the sand the pump was 

 started. As soon as the stream of water began to flow from the 

 nozzle under pressure the pile began to descend, and sank into 

 the sand at the rate of about 1 foot per second. 



When the required depth was attained, the small line attached 

 to the nozzle was let go, and the hose, with the water still flow- 

 ing, pulled up clear of the bottom ; the pump was then stopped, 

 and within a short time the sand settled to its original surface, 

 and the pile became immovable. 1 



Under the direction of the United States engineers, very 

 successful application of the water-jet was made in sinking 

 iron screw-piles at Lewes, Delaware. The piles consisted of solid 

 wrought-iron shafts from 5J to 8J inches diameter. In attempt- 

 ing to screw the piles down they broke, owing to the extreme 

 resistance of the material into which they were forced, before 

 they had reached the necessary depth. 



Attempts were made to reduce the resistance by leading a 

 jet of water to the material underneath the screw. The 

 prevalence of gravel in the sand and the insufficient power of 

 the pump led to unsatisfactory results. 



An examination of a broken pile led to the conclusion that 

 the greatest resistance encountered is on the upper surface of 

 the screw, and is doubtless due to the friction caused by the 

 superimposed cone of sand. 



It was thought that if a jet of water were forced into the 

 upper surface of the screw, it would accomplish the more com- 

 plete liquidity of the sand above the screw, and change the 

 volume of the pressure from that of an inverted cone to that 



1 Engineering, vol. xlviii. p. 55. 



