286 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



when a line of 12-inch sheet- 

 piling was driven, and when the 

 level of the bottom of the basin 

 was met, the whole width of 

 the apron was 80 feet ; it was 

 laid with stone blocks 5 feet in 

 thickness on the side next the 

 sluices, and 3 feet thick for a 

 width of 50 feet in the basin. 



The sluicing paddles or 

 valves were made of greenheart 

 timber, wedge-shaped, 6 inches 

 thick at the point, and 24 

 inches at the butt. Prepara- 

 tion was also made for a third 

 valve, of iron, which sliding in 

 a groove outside the other two, 

 was for use only when examina- 

 tion or repair was necessary to 

 the appliances within. 



Hydraulic power was used 

 for working the valves, and 

 was so applied and connected 

 with suitable* machinery that 

 one or more of the paddles or 

 valves, or the whole, could be 

 raised or lowered simultane- 

 ously, swiftly or slowly, as 

 might be required. 



In addition, two large cul- 

 verts, each 7 feet high by 6 feet 

 in width, were built within the 

 north and south side walls. 

 These culverts terminated at 

 the pier-heads in a group <!' 

 small outlets, and were intended 

 for clearing away any deposit 

 which, having been driven 

 down the basin by the action 

 of the main sluices, might 

 find a resting-place near the 



