EXAMPLES OF DOCK PLANS. 15 



at H.W.O.S.T. is 34 feet 6 inches, whilst the coping level is G 

 feet above the water. 



The entrance to the lock is placed at right angles to the 

 stream within a deep trumpet-mouthed embaymeut free from 

 tidal currents. The timber wharfage on either side is con- 

 tinued 300 feet up and down the river. This arrangement 

 of the entrance has answered admirably, vessels being able to 

 pass into the lock from either up or down stream without the 

 least difficulty. 



The entrance is exposed to a fetch of about 14 miles. Con- 

 sequently, with a south-westerly gale, there is a somewhat heavy 

 sea in front of the dock. Owing to the free access of the very 

 muddy water of the Humber into the original Hull Docks for 

 two or three hours each tide, the deposit introduced was found 

 to amount to as much as 1,250,000 tons of mud in the year, 

 necessitating the employment of a large dredging plant for its 

 removal. To obviate as far as possible the necessity of this 

 dredging in the Alexandra Docks, arrangements have been 

 made by which fresh water from the Holderness drain is 

 pumped into the basin to maintain the water leveL This drain 

 is a fresh-water stream draining a large portion of the Holder- 

 ness division of Yorkshire, and which has its outlet adjacent 

 to the Alexandra Dock. The pumps are capable of delivering 

 14,500,000 cubic feet of water into the basin in twenty-four 

 hours, thus benefiting the drainage of the district as well as 

 reducing the cost of maintenance of the dock. 



At Bordeaux, in consequence of the large quantity of mud 

 carried in the waters of the Garonne, a number of openings 

 were left in the upper part of the gates of the floating basin. 

 These openings stretch across the full width of the gates, and 

 are provided for the purpose of admitting the surface water 

 of the river at high spring tides. For supplying the basin 

 at low water, three artesian wells were specially sunk for the 

 purpose, from which a supply of fresh water varying from 

 24,000 to 31,000 cubic feet per hour is obtained, the water being 

 stored in a reservoir having an area of 40 acres, and from which 

 it is passed into the basin as required. 



Tilbury Docks (Fig. 9), on the Thames, constructed from the 

 designs of Messrs. Manning and Baynes, M.M.I.C.E., consist of 

 a tidal basin with a wide entrance to the river. A main dock 

 connected with the tidal basin by a lock and three subsidiary 



