VI PREFACE. 



range of subjects, and is constantly dealing with new and complex 

 phenomena ; consequently, nothing is more certain than that he 

 who wishes to reach the perfection of his art must avail himself of 

 the experience of others as well as of his own, and that he will not 

 unfrequently find both little enough to guide him " (" Presidential 

 Address of the late Sir John Hawkshaw to the Members of the 

 Institution of Civil Engineers," Min. Proc. Inst. C.E., vol. xxi.). 



If this be true as it undoubtedly is of the profession of civil 

 engineering generally, it is eminently so of that admittedly 

 difficult branch of it which deals with sea-works. I therefore 

 feel that I need offer no apology for having consulted numerous 

 works, or for having collected information from all available 

 sources, in compiling the present volume. It is not, however, a 

 mere compilation of knowledge derived from the writings of 

 others, for it includes the results of my own research, and of 

 experience which I have gained in the course of a practice 

 extending over a period of well-nigh thirty years. 



In consequence of my time having been very fully occupied 

 by my professional duties, much of what I have written has been 

 jotted down in a somewhat fragmentary manner; and at times 

 many weeks, and even months, have elapsed without my having 

 been able to write anything at all, or even to put my notes into 

 shape.. I therefore beg the indulgence of my readers, and trust 

 they will deal leniently with me for all my shortcomings. 



I have endeavoured, by footnotes or otherwise, to record the 

 various sources from which I have gleaned information, but I 

 fear that in some instances I may have inadvertently omitted to 

 do so ; I now therefore very gratefully acknowledge my indebted- 

 ness to all those whose works I have consulted in the preparation 

 of this book, and I also tender my sincere thanks to my pro- 

 fessional brethren and others who have kindly furnished me 

 with much valuable information, which could not have been 

 obtained from other sources. 



WILLIAM SHIELD. 



PETERHEAD, N.B., 

 1895. 



