izo NOTES ON DOCKS AND DOCK CONSTRUCTION. 



pumping the mixture of sand and water thus produced through 

 the opening in the middle of the block. For the latter purpose 

 a centrifugal pump driven by a 10 horse-power portable engine 

 was employed ; the suction-pipe was held suspended by a light 

 staging so that the mouth was set a little below the bottom of 

 the block. 



Four powerful pumps were used to force the water into the 

 sand; each pipe supplied three nozzles connected to the main 



* 



Fm. 82. 



FIG. 83. 



delivery by a rubber hose, which passed over a set of pulleys 

 mounted on a light portable scaffold. For convenience of trans- 



jConcreti 



FIG. 84. 



FIG. 85. 



port, the whole of this plant was mounted on four platform 

 waggons running on rails laid parallel to the face of the quay. Fig. 

 89 shows the manner in which the twelve jets were distributed. 

 Eight of them were arranged round the sides of the opening in 

 the curb, the four others were placed in the middle, round the 

 suction-pipe of the centrifugal pump. One of the four nozzles just 

 referred to was connected to the suction-pipe in such a way that 

 the jet of water discharged kept the pump constantly clear. 



