284 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



the effect of a river passing through the basin with a gentle 

 current, not strong enough to hinder vessels of light draught 

 remaining there during the operation ; on the contrary, it was 

 assumed that the scouring process would be more effectually 

 carried on while the vessels were there than if the basin 

 remained unoccupied. 



The scouring water was to flow through the basin like a 

 sub -aqueous river, sweeping over the bottom with scarcely any 



disturbance of the surface ; there were to be no eddies or fc 

 currents, as were known to exist under the ordinary modes 

 sluicing, the surface water would not be much agitated, thei 

 would be no bubbles rising up, neither would there be anj 

 tearing up of the bottom. 



To effect this object, the head walls were to be construct 

 with sluices so designed as to pour forth for the whole width 

 stream of water as nearly as possible in a continuous sheet. 

 The sills of these sluices were to be laid about 2 feet above the 





