CHAPTER VI. 



Dry or graving doclcs Locks Early practice Docks in a tideless sea Method 

 of construction Slope of dock floor Dimensions of docks Plan of docks 

 Depth over sill Local and shipping conditions to be studied Floor of dock 

 Mud docks of India Avonmouth dock Genoa dry docks Panama canal locks 

 Wivenhoe dock Green's dock, Blackwall Toulon docks Timber docks 

 Mount Stewart dock Calais docks Somerset dock, Malta Extension of dork 

 at Leghorn Glasgow No. 2 dock Esquimalt dock. 



THE earliest example of a graving or repairing dock is illustrated 

 by the practice of the Greeks, who ran their boats upon the 

 sandy beach, and then dragging them out of the reach of the 

 tide, surrounded them with earthworks for their protection. 1 

 A natural improvement, where the ground was suitable, was to 

 prepare an inclined plane of timber to facilitate the operation. 

 Where the tides were favourable, the vessels were simply beached 

 at high- water spring tides, and then left high and dry till the 

 following springs. In situations, however, where the forma- 

 tion of the beach allowed of it, a convenient bed or grave was 

 dug for receiving the vessel during high water at springs, such 

 excavations being protected from the ingress of the water at 

 the following springs by an artificial bank thrown up in the 

 interval. This was the first graving dock. 



The ordinary dry dock, as formerly used in tidal rivers, was 

 generally a simple excavation, usually lined with timber, with 

 a brick or concrete floor, and, to exclude the tide, fitted with 

 gates or floating pontoons. The vessel entered at high tide, and 

 the entrance closed ; as the tide went down, the dock emptied 

 itself through a tidal sluice, and the vessel settled down on the 

 blocks prepared for it, and being at the same time shored 

 horizontally to prevent its heeling over. 



The sluice and entrance being closed, the returning tide was 



1 M.P.I.C.E., vol. xxv. p. 203. 



