ii2 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



of the water within the basin. Therefore, in dealing with outer 

 wharf walls such as in a tidal basin, or walls in any position 

 where the water level is likely to be influenced by outside swell, 

 it is necessary to provide a greater margin of safety between 

 the greatest draught of ships and the basin bottom than is the 

 case in an enclosed basin where the water is practically quiescent. 

 In basins, or alongside wharf walls, when this precaution has 

 been neglected, a slight send only may expose ships to a con- 

 siderable amount of risk. 



Veneering, In dealing with some of the sandstone rock met 

 with in carrying out the dock extension at Liverpool, Mr. G. F. 

 Lyster, M.I.C.E., adopted a method by which a very sound system 

 of " veneering " was attained. 1 



The rock was cut away to a nearly vertical face at a distance 

 of 2 to 4 feet behind the face line of the stonework with which 

 it was to be veneered. At distances of about 20 feet apart 

 along the line of the wall excavations were made from coping 

 to foundation levels in the form of counterforts. They were 

 5 feet in width by 4 feet in depth, and were dovetailed in shape 

 from top to bottom. Into these were inserted large blocks of 

 ashlar, also cut dovetail, so as to fit the excavated chamber, and 

 shaped dovetail outwardly to interlock the masonry panels 

 which intervened between the counterfort stones. The whole, 

 being of sound selected stone, presents to the eye the appearance 

 of a wall of ordinary character, and is so interlocked and held 

 in place by the dovetail jointing that no possible failure of the 

 panels can occur (Figs. 70, 71). 



Quay Wall at Greenore, 2 In constructing a quay wall at 

 Greenore, Mr. J. Barton, M.I.C.E., adopted the following method. 

 It was intended at first to form the whole of the foundation up 

 to low-water level with Portland-cement concrete, deposited in a 

 soft state through the water within close sheet-piling, and a short 

 length of 30 feet was commenced and carried out in this way. 

 In consequence, however, of some defects having been discovered 

 in the face of the work it was considered advisable not to 

 proceed further. 



The face below the water level was then formed of concrete 

 blocks, set in place by divers, and backed as far as the piling had 

 been driven by soft concrete deposited through the water us 

 before. The face blocks, 4 feet 8 inches by 4 feet by 3 feet, and 



1 MP.I.C.E., vol. c. p. 31. * Hid., vol. xliv. p. 131. 



