174 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



made for the purpose, and, as the work progresses, the caisson 

 is raised by forcing water out of it. In this manner the whole 



tffj-oo) 



---jS-oo--- 

 FIG. 153. 



of the dock bottom is put in by sections extending the full 

 width. After the bottom is completed, the concrete in the 

 side walls is put in by means of caissons slung from pontoons. 



rz-co 



K I2-OO ->, 



1 



N 



3S-00- 



FIG. 154. 

 Panama Canal Locks. 1 These locks, of which a typical 



1 Engineering, vol. xlviii. p. 512. 



