Presidential Address. 41 



The main suction pipe of the " Octopus " was 44 inches internal 

 diameter, with flexible joint to withstand the movement of the vessel, 

 placed in a central wall in 'the bow, and of sufficient length to dredge 

 considerably below the depth required for navigation. There were 

 two sets of independent triple-expansion engines in addition to the 

 propelling engines, driving two 33in. centrifugal sand-pumps work- 

 ing out of the main suction pipe, and these could be worked 

 separately or together as required. The suction-pipe and hopper 

 doors for discharging the dredged material were controlled by 

 hydraulic power. The propelling machinery consisted of two sets of 

 triple-expansion engines driving twin screws to give a speed of 9^ 

 knots per hour. On one occasion, a piece of bar iron weighing 87 lbs. 

 was sucked up by the pumps of a sister vessel, the " Walrus," and 

 pieces weighing upwards of 56 lbs. have frequently been brought up 

 by both dredgers. The plan of dredging well below the required 

 navigable depth outside the entrance, and thus making allowance for 

 any shoaling during rough weather, I saw in use in Holland, in 1888. 

 where it was regularly practised by the Dutch, who at that time were 

 considerably ahead of English engineers in sand-pump dredging. 



The contract dredging capacity of the " Octopus " was 3.000 

 tons of sand per hour, but her record time in filling her hopper with 

 1,200 tons of sand was about 13 minutes or nearly 100 tons of sand 

 per minute. 



This boat Inaugurated, as I pointed out to the Legislature in 

 1895, the commencement of " greater experiments of outer sea 

 dredging than had probably been tried in anv other part of the 

 world." 



The conditions existing at the entrance to Durban Harbour at 

 this time, however, were not favourable to successful dredging 

 operations. The southern work at Durban on the weather side of the 

 entrance, known as the South Pier, from which the sand travel came, 

 overlapped or protruded further into the sea than the northern 

 work by some 700 feet, and a spit or tongue of sand constantly 

 formed under the lea of the projecting work, while the outflowing 

 tide followed the line of least resistance round the head of the 

 shorter North Pier, tending to form a northern channel there. 



I insisted on the absolute necessity for the immediate extension 

 of that work. The dredger could only w'ork on the line of the axis 

 of the Bluff or Entrance Channel, that is straight out to sea. To 

 have worked further to the Northward, with the tides, would have 

 brought her broadside on to the seas. and would have 

 been dangerous if not impracticable. In fact, to put it shortly, the 

 dredger could only work in one direction, while the tides worked in 

 another. Nature was being pitted against the artificial power of 

 dredging, and even if she did not win. yet the result would be to 

 greatly increase the annual cost of dredging instead of reducing it to a 

 minimum by bringing forward the North Pier abreast of the break- 

 water, and inducing the two powers to work together. 



