nS NOTES ON DOCKS AND DOCK CONSTRUCTION. 



SECTION OF DOCK WALL 



to be protected by a thin casing of harder material (in this 



case Bramley Fall 

 rubble), to preserve 

 it from injury before 

 the backing could be 

 carried up (Fig. 78). 

 A modification con- 

 sisted in the substi- 

 tution of Portland- 

 cement concrete for 

 -Drain Pipe the Ashlar and chalk 

 rubble in the lower 

 part of the walls. 

 The proportion for 

 the face was 5 of 

 stone and sand to 1 

 of cement, and for the 

 backing 7 of stone to 

 1 of cement (Fig. 79). 

 Calais Basin Walls. 1 

 For putting down 

 the foundations of 

 the north-eastern and 

 south-western walls 

 the system adopted 

 by Mr. Vetellart pos- 

 sesses many features 

 of interest. The ground 

 consisted of fine sand, 

 and it was necessary 

 in the case of the 

 north-eastern quay to 

 reach a depth of 16 

 feet below the normal 

 bottom of the basin. 

 The ordinary method 

 of excavating and 

 removing the sand 

 would have involved 

 great trouble and 



H.W.O.S.T. 



Drain Pipe 



-Drain Pipe 



SCALE 



FIG. 79. 



Engineering, vol. xlvii. p. 577. 



