39 



that we are called iipon to complete by artificial means those features that 

 exist naturally in a more or less perfect state, either by constructing 

 breakwaters or piers to obtain sufficient shelter, or by resorting to dredging 

 for the removal of shoals to acquire ample depth of water at all 

 states of the tide. 



In connection with harbour works, it would be manifestly absurd to 

 generalise or advocate any jjarticular mode of procedure or disposition of 

 structure that would be applicable to all circumstances and localities. No 

 works whatever require more careful consideration and skill, or are at- 

 tended with more aggravating consequences when hastily or improperly 

 devised. 



Of course shelter may be obtained in a broad expanse of sea by con- 

 structing an isolated breakwater in the midst of the bay, as at Plymouth, 

 or by running a pier from the land oi;t into deep water ; but if the 

 prevailing winds and the set of the tides are not carefully considered, 

 serious complications of tidal currents may be the result, and the harbour 

 instead of being a place of shelter easy of access, will be only a 

 trap for the accommodation of shoals and a terror to the mariner. 



In addition to possessing ample depth of water and good sheltered 

 anchorage at all times, it is obvious that a harbour of refuge should be 

 particularly easy of access ; greater facility should be afforded for the 

 entry of vessels than for their departure, because during an on-shore gale 

 when vessels seek the protection of a port on their lee, manoeuvering at 

 the entrance might result in their missing the harbour altogether and 

 becoming wrecks on the lee-shore, whereas when once inside and anchored 

 in safety they can very well remain there until the storm has abated. 



In the standard type of breakwater the substructure is formed by 

 depositing stone in the rough state along the site of the work, either by 

 tramways from the shore or by hopper barges directed in position by 

 beacons or landmarks ; a huge mound is thus formed which after exposure 

 to the action of the sea foi- some time becomes consolidated and assumes 

 a certain form. Within the limits of the tidal range the materials are 

 disposed of in the form of a long flat slope similar to a beach ; below low 



