20 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



entrance to this basin is also 60 feet wide, and opens into the 

 Severn slightly to the south of the mouth of the river Ely, 

 through protecting jetties forming a deep, trumpet-shaped 

 embayment. 



On the sills of both the outer entrance and the lock the 

 depth of water at ordinary spring tides is 35 feet, and at neap 

 tides 25 feet. 



The outer entrance is somewhat exposed, and subject during 

 stormy weather to seas of a considerable height ; outer or sea 

 gates are therefore provided. 



Penarth Tidal-harbour. 1 As a typical example of an open 

 tidal harbour, the lower reach of the river Ely may be referred 

 to. This part of the river forms the Penarth tidal harbour 



FIG. 11. 



(Fig. 11). The depth of water at the loading-berths at high water 

 of ordinary spring tides is 30 feet, and at neap tides 20 feet. 

 Vessels up to 800 tons can be accommodated. The maximum 

 run of the tide in this harbour is about 2 J knots per hour. 



Barry Docks. 2 Fig. 12, showing the Barry Docks, is a good 

 example of the adaptation of the plan to the peculiar configura- 

 tion of the site available, which consisted of a channel about a 

 quarter of a mile in width between the mainland and Barry 

 Island. 



Alexandra Dock, Newport, Mon. 3 This dock (Fig. 13), com- 

 pleted in 1875, from the designs of Mr. J. Abernethy and Mr. 



'jineering, vol. xxxviii. p. 148. 2 M.P.I C.E., vol. ci. pp. 129-152. 



* Engineering, vol. xxxviii. p. Hi). 



