92 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



concrete above it, and with it the lower part of the pump-hole. 

 Through the crack thus formed in the walls of the pump- 

 hole the water found a vent. To remedy this, a wall of brick- 

 work set in cement was built round the well-hole of the pump 

 to a height beyond which the water would not rise. The 

 space so enclosed was then filled with concrete. The h<>l<^ 

 in the stones were stopped with wooden plugs ; but the plan 

 which of necessity had been adopted for the pump-hole, and 

 also for the cast-iron pipes, was found to be much preferable. 

 When plugs were used, the water was left with a free com- 

 munication to a point too near the surface, and consequently, 

 when the concrete had been formed to the different levels, and 

 the lower settled away from the upper layer, the brick shafts 

 were divided below the plugs, and the water escaped from 

 between the layers. 



The boils in the gate floor were treated in the same way 

 as those in the sills. A dam was placed across the masonry 

 of the invert, and the water was allowed to accumulate at the 

 east end of the lock until it attained a level of 2 feet above 

 the sill. On the water being pumped out, a strong boil was 

 found to have burst up through the cement concrete in the sill, 

 where further settlement had taken place. A wall of brick- 

 work set in cement was built round this boil, enclosing a space 

 of about 4t feet square. It was subsequently determined to 

 remove the east sill 190 feet to the westward, and to cover the 

 abandoned site of the sill, gate floor, and apron, with brickwork 

 set in Portland cement to within 2 feet of sill level. This 

 being done, the brickwork was continued beneath the lock 

 walls at the same level ; a portion of the back of the lock walls, 

 to a height of 12 feet, was also built of brickwork set in 

 lias-lime mortar. This brickwork effectually stopped the flow 

 of water. The space behind the lock walls was at once bricked 

 up, and the difficulties with these foundations seemed to be 

 finally overcome. 



Fleetwood Docks. 1 In dealing with the foundations for the 

 dock walls at Fleetwood, where difficulties were met with 

 from springs, the following course was adopted by the engineers. 

 The walls were constructed in timbered trenches throughout. 

 It was originally intended to found them at a depth of 17 f<vt 

 below the dock bottom, so as to reach hard clay ; but the level 



1 M.V.I.C.E., vol. xoii. p. 1>1. 



