SLIPWAYS. 319 



forming the rest for the keel-blocks, and of two lighter side ribs 

 corresponding in position with the side- ways. 



From the centre rib to each of the sides stretch transverse 

 pieces of wood or iron, carrying sliding bilge-blocks, worked by 

 ropes and gear from the deck of the vessel, or from jetties. The 

 sliding blocks are trimmed with supplementary loose blocks, 

 shaped to suit the size and description of vessel to be hauled up. 

 The cradle ribs are carried on numerous cast-iron rollers 

 fitted in cast-iron carriages (Figs. 316, 317) ; those at the centre 

 being placed as close together as possible, while those for the 

 sides, where the pressure is small, may be placed some distance 

 apart; about ten of the centre carriages are formed to receive 

 the pawls for holding the cradle. It is also usual to provide two 

 or three short, independent cradles, which may be attached to 

 the top of the main cradle, according as the vessel to be repaired 

 is long or short. 



The other adjuncts of the cradle are wrought-iron ploughs 

 at the after end of each rib, for removing silt or mud, or any 

 other obstruction that may accumulate on the lower end of the 

 ways; hinged iron rods for guiding the keel of the vessel 

 properly into the centre of the cradle one pair being placed 

 at the top for the bow, and one pair at the bottom for the stern ; 

 also sundry gear for working the bilge-blocks and for lifting and 

 lowering the pawls. 



The arrangements for hauling up may consist of hydraulic 

 or steam machinery, or other gear, actuating strong forged-iron 

 rods and endless pitch chains, link chains, or steel-wire ropes. 



Whatever form of hauling-gear is adopted, it will generally 

 be of advantage to have a supplementary engine and crab with 

 chain, for traversing the empty cradle quickly up and down, 

 especially in positions where there is likely to be an accumula- 

 tion of mud at the lower end of the ways, in which case the 

 empty cradle, when run down, would not acquire enough velocity 

 to overcome and remove the obstruction. 



To avoid the expense of divers' work, various proposals have 

 been made and carried out; the simplest and usual plan is 

 to make the cradle telescopic that is, in several divisions 

 attached to each other by sliding lengthening bars which 

 permit the various sections to close up when the cradle is run 

 down for taking up a vessel, and to open out when the hauling 

 commences. 1 



1 M.P.I.C.R, vol. ixxii. p. 183. 



