SITES NEAR THE SEA. 5 



silt, available for supplying the basins, a dock may be more 

 suitably placed than where the supply is from the sea or tidal 

 water, if it is much loaded with matter in mechanical suspension. 



No hard-and-fast rule can be laid down as to the selection of 

 a location and the preparation of a dock scheme, as so much 

 must of necessity depend upon local conditions such as prevailing 

 winds, rise and fall of tide, strength and set of currents, configu- 

 ration of the land, and many other points. 



Sites near the Sea. Owing to the increased size of ships, and 

 consequently the greater accommodation required, the tendency 

 is to select sites nearer the sea than was formerly the case. In 

 considering, however, the advantages and disadvantages of avail- 

 able sites, it is necessary to bear in mind that the principal 

 benefits derivable from them are the conveniences and facilities 

 they offer for commercial purposes, facts which should have the 

 greatest weight in governing the selection of a site, and which 

 would perhaps warrant the works being placed at a distance 

 from the sea. 



Should the position selected be in a land-locked bay or a 

 narrow river, no particular precautions as regards the dock 

 entrance is called for. On the other hand, as regards the more 

 exposed positions near the sea, the position and form of the 

 entrance will require careful consideration. With a considerable 

 fetch, waves might be generated during gales of such a height 

 as to endanger the entrance gates or interfere with their being 

 worked during stormy weather. 



In reference to entrances and entrance channels, Sir John 

 Rennie very clearly expressed his opinion as to the broad prin- 

 ciples on which he held such works should be designed, and 

 although his views referred more particularly to harbour 

 entrances, and the days of sailing-ships than to dock entrances, 

 yet, they are applicable to a very great extent to the latter 

 when constructed, as is at times unavoidably the case, in exposed 

 positions, and probably requiring an outer basin or entrance 

 channel. It may, therefore, not be altogether out of place to 

 quote them. These principles are: 1 "That every harbour 

 should have its entrance so placed as to face as much as possible 

 the direction from which vessels can most conveniently enter 

 in stormy weather ; but that the heads should be made of such 

 a form as to admit of the least sea entering, or so as to occasion 

 1 Lives of the Engineers," vol. ii. 



