HYDRAULIC LIFTING-DOCK. 



307 



the sea, in order to allow the dock to be emptied into the air- 

 chambers. 



Fig. 307 shows the position of the dock when heeled over 

 in order that the bottom may be cleaned or repaired. 



In docking small vessels, the dock has sufficient buoyancy 

 to lift them quite out of the water, when the caissons are not 

 required. 



Hydraulic Lifting-Dock, The following extract, taken from 



FIG. 303. 



FIG. 301. 



FIG. 307. 



a paper by Mr. E. Clark, 1 on the hydraulic-lift graving clock 

 erected at the Victoria Docks, London, gives a very clear 

 description of this class of dock (Figs. 308 to 311). 



"The lift is a direct mechanical appliance for raising the 

 vessel by means of hydraulic presses. It consists of tworows 

 of cast-iron columns, each 5 feet in diameter at the base, and 

 1 M.r.I.C.E.,vol. xxv. p. 292. 



