64 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



by the pile-driving machine, and is readily driven in line 

 with those already down. The throat of the " spider " guides 

 the point and body of the pile to its place, and the elasticity 

 of the hawser permits a pile or two to pass through before 

 slacking. In the result, the control of the work was so perfect 

 that, only at intervals of from 20 to 30 feet a special wedge- 

 shaped pile was required to be driven butt down to keep the 

 work vertical at the driving point. 



With a " spider," at least double the number of sheet-piles 

 could be driven in deep water, where the mud was shallow, 

 than was possible, at the same expense, without such a 

 contrivance, and the work was much better done. 



On the surfaces of contiguous sheet-piles a single thread 

 of ordinary spun yarn or marline was tacked; this made 



FIG. 47. 



the joint almost water-tight, as was proved by the fact that 

 the water was often found 2 feet higher inside than outside the 

 enclosed space. 



The sides of the enclosure with the cross dam and quay 

 having been completed for one block or section, the whole 

 was secured by ties and bolted together above the level of the 

 concrete. 



Esquimalt Dock. 1 The dam (Figs. 47, 48) adopted by Messrs. 

 Kiniple and Morris, M.M.I.C.E., to enclose the site of the 

 Esquimalt Dock, consisted of three rows of close sheet-piling 

 driven circular on plan to a radius of 400 feet for the outer row, 

 and 379 feet for the inner row. 



The bottom for the greater part of the length consisted of 



1 Engineering, vol. xlvi. p. 87. 



