FOR GREA T BRITAIN AND IRELAND. 79 



SMALL CLOSE HARBOURS MORE DIFFICULT TO DESIGN 



THAN LARGER. 



" Difficulties of design increase greatly as the extent of 

 the works diminishes. Indeed if the piers inclose a very 

 large area some of the elements of difficulty will nearly 

 altogether disappear. Little attention need then be given 

 to the questions which are so troublesome in small basins, 

 regarding reductive power, want of spend, recoil of waves, 

 and comparatively little as to width of entrance." With 

 the above last-quoted paragraph, Mr. Stevenson leaves 

 this part of the subject. 



THE APPLICATION OF THE NATURAL PRINCIPLES 

 OF REDUCTION OF WAVES TO THE PROJECTION 

 OF ARTIFICIAL HARBOURS. 



At the first glance at the accompanying diagram, the 

 reader may imagine that the circle and semi-circle 

 constitute nothing more than a fanciful conception of the 

 writer, but in a few words he hopes to show that they have 

 a very deep significance, and that the projection of a 

 harbour by the aid of a circle is the true method of 

 performing such a work, and that in fact it is the key 

 of the subject. 



All undulation, either from a free pier-head or break- 

 water, or from between two pier-heads, is of a radiative 

 character, and provision for its reduction should be made 

 by the aid of a circle on this account. 



Another reason is that no other figure conveys to the 

 mind of man so definite a conception of either proportion 

 or distance. 



Radiation of undulation manifestly implies the existence 

 of a centre, which we find commences, as above mentioned, 



