CALAIS LOCKS. 



193 



tween the inner ebb gates 447 feet 3 inches ; when divided by 

 closing the intermediate gates, one chamber is 185 feet long, 

 and the other 258 feet 6 inches. 



On the left side of the larger dock there are two culverts, 



one 9 feet 10 inches wide and about 15 feet high, and the other 

 7 feet 3 inches wide by 9 feet 10 inches high. The larger 

 culvert takes the water from the floating dock, the dry dock,, 

 and the flood water from the Calais Canal, etc. The smaller 

 culvert serves for regulating the water level in the lock, and 



also for sluicing the outer port and the lower entrance and sill 

 of the larger lock. Other culverts are formed in the central 

 wall between the two locks, and on the right side of the smaller 

 lock. The former is 7 feet 4 inches wide by 9 feet 10 inches 

 high, and the latter 5 feet 3 inches wide by 9 feet 10 inches 



FIG. 177. 



high. Communications are made between these culverts and the 



locks by transverse channels, and a complete system of valves is 



introduced so as to control the flow of water through the culverts. 



The strata being fine sand, the sill was surrounded with 







