LXVIII. NOTES ON WHARF IN DEEP WATER, DAWES' POINT. 



staying a jetty by diagonal piles has since become common in 

 Sydney harbour ; it was the only one possible in this case. In 

 securing the diagonal piles, there are not only bolts to the head- 

 stocks and girders at their heads, but also two 1J in. galvanised 

 bolts, put in by divers, right through at their intersections with 

 the vertical piles. 



When the jetty was approaching completion, permission was 

 obtained from the Government, and a few hundred tons of sand- 

 stone ballast were dropped on to the soft mud around a few of 

 the piles near the end, to act as a stiffener. The author is 

 indebted to Mr. C. W. Darley, Engineer-in-Chief, for the sugges- 

 tion to put this ballast on a mattrass, made of timber framing 

 and ti-tree fagines, in order to keep the ballast together, which plan 

 was adopted. The line shown on the drawings (ascertained after 

 it had had some weeks to settle) shows that it has not spread as 

 might have been anticipated from the softness of the mud. 



When the piles were 60 feet in the water, they were often 

 more than 20 feet above the head of the pile driver, and had 

 it not been that the soft mud allowed them to be dropped from 

 20 to 25 feet into it, that is from 80 to 85 feet below water line, a 

 pile driver, with shears from 70 to 80 feet high, would have had 

 to be built specially for the work. 



Probably the most interesting matter to many members in 

 connection with such a work, is the pile driving, and the author 

 regrets that he has not collected sufficiently accurate data to 

 supply material for a new formula. Personally, he has no great 

 faith in the practical value of any pile driving formulae, because, 

 for actual work, the pile last driven generally affords information 

 to guide the engineer as to the treatment of its neighbour, which no 

 theory can supply. Some particulars, however, were taken of 

 a few piles, which may be a guide for future work of this kind 

 The provisions of the specification as to ram or monkey, were 

 that short and rapid blows would be preferred by Sisson's 

 Lacour's or Nasmyth's machine, and that the engineer was to be 

 satisfied that all piles reached the rock, and have any pile drawn 

 he disapproved of. 



