152 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



suspended, was gripped on either side and so kept from 

 swaying. 



As soon as the block was lifted, the pontoon was warped 

 off from the wharf and the block lowered into the water about 

 half its height, so as to relieve the lifting gear by the partial 

 displacement. 



The vessel was then moored in position, and the block 

 lowered to within a few inches of the bottom, and close to the 

 block previously set. 



The exact adjustment of the block in line was effected by 

 temporarily fixing short timber bollards in the grooves left 

 in the sides of each block ; two were set in the block already 

 in position, and two in that about to be set. On either side 

 of these bollards a short piece of baulk timber was placed 

 horizontally, which secured by screw bolts to the block already 

 in place, kept all four in line, and adjusted the range of the 

 block being set, which was then drawn up into close contact 

 by a small tackle, one end of which was attached to the 

 top of the ^ suspending bars, and the other to one of the blocks 

 previously set. 



The Albert Harbour, Greenock. 1 A method of construction, 

 adopted by Messrs. Meller and Bell, in forming the outer 

 sea-piers of the Albert Harbour, Greenock, where the con- 

 ditions were such as to render the construction of a coffer- 

 dam inexpedient, consisted of cast-iron piles with stone 

 slabs enclosing them, and forming the face of the work with 

 concrete backing deposited in a soft state up to the low- water 

 level, above which the walls were continued in the ordinary 

 manner. 



The pier was 60 feet wide at the top, with quay walls on 

 both sides which were 33 feet in height from the foundations, 

 11 feet 6 inches thick at the base, and diminished to 5 feet at 

 the top (Fig. 133). 



The ground was very unequal, the hard substratum being 

 in some places 20 feet below the bottom of the wall, the upper 

 strata being mud and soft sand. In such cases, timber piling, 

 driven to the same level as the iron facing-piles, was used to 

 form a platform to sustain the part of the wall above the 

 low-water level, but where the ground was firm this was not 

 required (Figs. 133, 135). 



1 M.P.I.C.R, vol. xxii. p. 425. 



