302 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



staging and the pontoons passed between the piers with the keel 

 of the vessel clear above the middle line of blocks on the staging, 

 the outer or bilge-blocks being temporarily turned down. As 

 soon as the vessel is over the keel-blocks, the dock is slightly 



PLAN OF GRIDIRON STAGING 

 FIG. 296. 



lowered to allow the ship to take a bearing on them ; the bilge- 

 blocks are then adjusted, and the dock is lowered clear of the 

 vessel and withdrawn. A slight variation in the level of the 



FIG. 297. 



water can always be accommodated by the use of more or less 

 blocking. 



The operation of lowering the vessel from the staging into 

 the water is the exact reverse of that of depositing. 



Figs. 29G to 299 show the general arrangement of a deposit- 

 ing dock constructed at Barrow-in-Furness, by Messrs. Clark and 

 Standfield. 



