the Necessity of lifting Ships, 247 



block on the top will drop down. When the work is per- 

 formedj the block must be replaced under the keel, and the 

 wedges driven back bw working the rams athwart-ships, 

 as described in the section. 



N. B. In returning. the iron wedges, to avoid straining 

 the angular blocks, it is proposed to leave a few of them 

 out forward and aft, and stop the ship up, by laying one 

 iron wedge on the other, as shown at Fig. 1 , Plate IV. 



To facilitate the business, blocks may be cleared forward 

 and aft at the same time, sufficient to get in place one 

 length of false keel. If the false keel should want repairing, 

 it may bedone without any additional shores, by clearing one 

 block at a time ; and when the keel is repaired in the wake 

 of that block, return the wedges, as above directed, and 

 clear the next^ &c. 



Section and Plan, Plate IV. Fig. 2. 



A, Keelson. 



B, Ceiling. 



C, Floor timber. 



D, Dead or rising wood. 



E, Plank of the bottom. 



F, Keel arrd false keel. 



G, Angular blocks with a half-inch iron-plate bolted to 

 them. 



H, Cast-iron wedges. 



I, Iron -plate of three-fourths of an inch thick on the 

 bottom of the dock. 



K, Battering-rams, with wheels, and ropes for th.e 

 hands. 



L, Cast-iron wedges, having received a blow from for- 

 ^V'ard. 



M, Shores under the ship to sustain her weight. 



Fie. 3. represents part of a top-gallant mast fitted with 

 a wedge fid. 



a, Top-gallant mast. 



I, Fid, with one horizontal wedge worked on it. 



c. Moveable wedge, with the iron strap and pin over it, 

 to keep it in its situation. 



df Trussel trees. 



<3 4 XXXVII. On 



