WATER IN FOUNDATIONS. 91 



bolted (Fig. 60). This addition was a great improvement, as the 

 site of the boil could, on the casting being placed over it, at 

 once be covered with concrete, and by means of an elbow sub- 

 sequently bolted to the horizontal pipe, the outlet could be 

 gradually raised vertically by short lengths of pipe as the con- 

 creting was proceeded with. When a vertical pipe had been 

 used directly over the casting, it had been found that the water 

 almost invariably came up through the fresh, concrete surround- 

 ing the casting; for, as the surface of the concrete had to be 

 kept at least 1 foot below the top of the pipe, in order to leave 

 room to bolt on the additional lengths of vertical piping, the 

 water had less height to rise than would have been the case if 

 it had flowed up the pipe. Another obvious advantage in using 

 the horizontal pipe was the removal of the flow of water to a 

 distance from the concrete. A canvas hose had been tried for 

 this purpose, but the first objection to the vertical pipe applied 

 equally to it. 



Four vertical pipes 6 inches in diameter were brought up 

 in the concrete west of the compartments ; when the concrete 

 round the pipes had set, additional lengths were bolted to them, 

 until the top of the pipe exceeded the level to which the water 

 would rise. As much cement grout as they would hold was 

 then poured into them. 



It had hitherto been found quite useless to attempt to stop 

 even small boils with concrete alone ; accordingly, when a 

 boil now occurred in the concrete a shaft of brickwork set 

 in cement was built over it, an opening for the escape of the 

 water being left on the side nearest the pumps. From this 

 opening a narrow channel was formed by two brick walls 

 extending in the direction of the pump to a distance from the 

 shaft depending on the size of the boil and more or less perfect 

 state of the concrete. On the top of the shaft was placed 

 a stone with a hole in the centre. The top of the stone was 

 set even with the finished level of the concrete, which was then 

 put round the brickwork. When this concrete was consolidated, 

 the narrow channel between the brick walls was also filled, 

 and the water forced up through the hole in the stone. 



The water flowing through the concrete in the silt was thus 

 confined to five places. Owing to settlement which was still 

 going on, an unforeseen difficulty occurred at the pump-hole. 

 The liine concrete parted from the more rigid layer of cement 



