PREFACE 



THE object of this work is to set forth the general principles 

 which should govern the design and construction of harbours, 

 and to describe the various types of breakwaters and the methods 

 of constructing them usually adopted in modern practice. 



Drawings of different kinds of breakwaters, including some 

 of the more prominent existing works, are given ; and, in addition 

 to these, numerous diagrams and sketches have been introduced 

 wherever it has been considered they would be useful in eluci- 

 dating the descriptions given in the text. 



The chance of successfully opposing an enemy depends much 

 upon knowledge, previously obtained, respecting his strength 

 and mode of attack, and of the means and materials available 

 for purposes of defence. It is, therefore, of importance that the 

 harbour-engineer should be well informed respecting the forces 

 against which he will have to contend, and also that he should 

 possess an accurate knowledge of the structure and properties of 

 the different materials which are available for use in harbour 

 construction. The subjects of wind, waves, tides, currents, and 

 materials have therefore been treated of at some length ; and 

 attention has also been directed to the more important physical 

 conditions which affect harbour construction. 



" The wide range of subjects which the profession of a civil 

 engineer embraces, renders it imperative on every member of it 

 to avail himself of all the help he can obtain. 



"The personal experience of one individual cannot fit him 

 for the exigencies of a profession which is ever extending its 



