STOPPING LEAKS. 99 



clearance between the surface of the concrete and the planking. 

 After the floors were completed in this manner, cement grout 

 was pumped in, soon the leakage from one point and then 

 another ceased, and eventually the whole floor became perfectly 

 tight. 1 



In a case where the water overpowered the pumps, Mr. W. Dyce 

 Cay, M.I.C.E., adopted the following expedient. Instead of 

 trying to overcome the water, it was allowed to rise to the 

 natural level; the excavation was then completed by dredging, 

 and the pile heads cut off to their proper level by divers. The 

 area was then covered with jute cloth, sunk and fastened to 

 the piling, and Portland- cement concrete deposited on it under 

 water by skips opening at the bottom, and brought up to such 

 a height as would keep down the water pressure, and as tho 

 work allowed. After giving the concrete time to set, the water 

 was pumped out, and the work finished without further trouble. 3 



Borings put down to a water-bearing strata, or blow-holes, 

 may frequently be stopped by driving a pipe to the bottom of 

 the hole, or into a superimposed impervious bed, sufficiently 

 deep to ensure a water-tight joint, and allowing the water to 

 rise to the tide level, and then pumping in liquid Portland 

 cement; or, if the pipe is sufficiently large, running down 

 cement mortar, or fine concrete, the pipe being withdrawn as 

 the hole is filled. This latter course has been adopted in cases 

 where the holes were from 300 to 400 feet deep, and 10 to 24 

 inches in diameter. Provided there is no flow of water, blow- 

 holes, borings, or leaks may be effectually stopped by these 

 means. When the holes are small, an expanding screw plug 

 may be worked into the hole sufficiently low down as to be 

 well below the level of the foundations. 3 



For stopping a powerful spring at the bottom of a shaft, 

 Mr. Bateman, M.I.C.E., adopted the expedient of nearly filling 

 bags with shot, and sinking them to the bottom of the shaft. 

 The bags, not being quite full, took their shape one against 

 the other, and effectually overcame the difficulty. 4 



This would be a valuable expedient in cases where a great 

 weight is required within a limited thickness or depth to with- 

 stand hydrostatic pressure. 



Somerset Dock, Malta. 5 During the construction of tho 



1 Engineering. 2 M.P.I.C.R, vol. xcii. p. 177. Ibid., vol. xli. p. 120. 



4 Ibid. 5 Ibid., vol. xxxiii. p. 358. 



