FOR GREAT BRITAIN AND IRELAND. 71 



OF THE RADIA TIVE MOTION AND FORCE OF WA VES, 

 AND OF THE MEANS ADOPTED OR SUGGESTED 

 FOR REDUCTION OF THE SAME IN OPEN OR 

 CLOSE HARBOURS. 



This is a very difficult portion of the subject, so difficult, 

 indeed, that the writer approaches it with much diffidence ; 

 nevertheless it must not be shunted into a siding, so to 

 speak, for on the careful solution of this problem the success 

 of any work as a harbour must depend. 



So much damage has resulted in bad weather to boats 

 and vessels in artificial harbours from the violence of the 

 undulation or run of the sea, that in forming any design 

 for a harbour the reduction of the waves within the sphere 

 of the works should be looked on as the mainspring and 

 regulating principle of the form of the design. The 

 constructive strength in form of pier or piers, both of out- 

 line and of face, must of course be kept prominently in 

 view, and it does so happen that the form of pier which 

 promises the greatest tranquillity within the enclosure also 

 promises the greatest strength in construction ; the writer 

 refers to convexity of outline, which relieves the masonry 

 where most exposed, at the points of impact, where 

 circumstances permit of such a form, by dispersing the 

 force of the waves laterally on the outside, and allowing 

 them also to expand in like manner \vithin the enclosed 

 area. 



On this subject of the reduction of the waves, Mr. 

 Stevenson says : " I cannot but express regret that no 

 attempt has been made, so far as I am aware, to lead us 

 from mere speculation and guess to the exactness and 

 certainty derivable from calculations based on theoretical 

 or experimental data (page 118). I have been unable 



