damage of this kind under water, and still more difficult to 

 satisfactorily effect repairs. One thing is quite certain, 

 ferro-concrete structures of this class should only be placed 

 in the hands of experts to carry out, as extraordinary care 

 is necessary to secure reliable work. To allow the work 

 to be executed by persons without considerable knowledge 

 of the principles of its construction is simply courting 

 disaster. 



In other parts of the world groups of piles and cylinders 

 have been tried with success, but from what we are able 

 to judge of the cost of such work it seems highly probable 

 that a sea wall could have been built for the same or per- 

 haps even less cost, and would certainly have proved a 

 more substantial class of construction. While oifering 

 these criticisms I do not wish to imply that I consider 

 reinforced concrete unadapted to wharf construction. 

 Quite the contrary, but I do think that thoroughly suitable 

 methods have yet to be evolved. 



The widely varying conditions under which harbour works 

 have to be designed, prevailing winds and currents, rise and 

 fall of tides, nature of material available, etc., make marine 

 works a particularly interesting, as well as a dillicult study, 

 and yet perhaps in connection with no other professional 

 work do we find so many amateurs ready to give advice 

 and criticism. 



Take for example, the much discussed question of the 

 Sow and Pigs reef, near the entrance to Port Jackson. 

 Some advocate its removal because it disfigures our other- 

 wise beautiful harbour ; others because it is a danger to 

 navigation, while on the other hand, we heard an interest- 

 ing paper read not long ago, advocating the construction 

 at this place of extensive wharves and jetties to accom- 

 modate the whole of our over-sea shipping. This reef is 

 some three-quarters of a mile long, at its eastern end, 



