WIVENHOE DOCK. 



177 



In the upper side of the pipes within the lock there are 

 openings aji frequent intervals along the whole length (Figs. 

 156 and 157), and it is through these openings that the water is 



* 



FIG. 159. 



FIG. 160. 



FIG. 158. 



discharged or admitted according as the sluices at either end 

 are operated. It is claimed that many advantages attend this 

 method of regulating the water level ; one of the most important 

 being that the admis- 

 sion or exit of the 

 water is unattended 

 with any agitation of 

 the surface. 



The arrangements 

 for closing the ends of 

 the lock was by float- 

 ing caissons moving into chambers with a swing-bridge spanning 

 the entrance, the whole being moved by hydraulic machinery. 



Wivenhoe Dock. 1 A good example of a small dry dock 

 suitable for yachting purposes is shown by Figs. 161 to 163. 



This dock, constructed from the design of Mr. R. M. 

 Wilkinson, A.M.I.C.E., is 205 feet long, 45 feet wide between 

 the copings, and 35 feet wide in the entrance. The total depth 

 from coping to invert is 18 feet, affording accommodation for 

 vessels drawing 15 feet of water. 



In plan the dock conforms, at the head, closely to the shape 

 of the class of vessel it is designed to accommodate, and so 

 economizes surface area, and reduces the quantity of water 

 to be pumped. 



Two rudder wells are provided, that nearest the caisson 

 being intended for steam-vessels which have their rudders 

 vertical, and the inner for sailing-ships in which the rudders 

 1 Engineer, vol. Ixvi. p. 30 ; vol. Ixix. p. 158. 



N 



