50 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



piece attached being first driven, and afterwards the other. The 

 grooves thus left were for the reception of sliding panels, to be 



used in order to fill up the 

 spaces between the several 

 twin piles, as shown in Fig. 

 36. Waling-pieces of whole 

 timber were fixed to the 

 inside and outside, both at 

 the top and as near to the 

 low-water level as possible. 

 As the piles were driven, 

 proper struts and ties were 

 inserted to stiffen and 

 strengthen the dam, and 

 strongly framed raking struts 

 were fixed against abutments 

 composed of piles backed 

 with concrete. 



The panels were com- 

 posed of a series of timbers 

 7 inches thick, and of a 

 length necessary to enable 

 them to slide in the grooves, 

 fastened together by 1^-inch 

 round-iron bolts, and further 

 co strengthened and weighted 

 by flat wrought-iron plates 

 6 inches wide by 1 inch thick 

 fixed on one side. In order 

 to put these panels into place, 

 a frame was erected (Figs. 

 37, 39), from which they were 

 i suspended, and from which 

 they could be lowered, and 

 raised again if necessary, by 

 pulleys. 



The panels in the lowest 

 tier were pointed at the 

 lower end so that they could 

 be driven some depth into 

 the mud. When all the iirst 





