CO129-329 - Governor Nathan - 1905 [7-12] — Page 510

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507

Good specimens can be got in this way more cheaply and expedi-

:-tiously than by boring.

21.

The bulk of the stuff is mud (37), and un-

-suitable for a pump dredger ((18)). A ladder dredger, of the

"Canton River" type will probably be found to be the most suit-

-able.

22.

1 have plotted the accompanying sheet of

sections, from the Admiralty record charts, to show approximately

what will have to be faced in the way of dredging when the mat-

-ter comes to be taken up again. I think it may be assured, 00

general principles, that silting is proceeding very slowly. 1

"

have measured the quantities from the sections as they stood

when the soundings were taken, adding nothing for subsequent

silting. Carrying cut the dredging operations on the general

lines shown on my Chart 'F', partly to 5 fathoms, and partly

to 4 fathons, the quantity of stuff to be shifted is 15,000,000

tons. The old estimate was 27,000,000 tons (39). If the whole

area is to be dredged to 5 fathoms as suggested by the Harbour

Master, the quantity will become 25,000,000 tons.

23.

As the old estimate included a liberal

allowance for assumed silting after the date of the last survey,

and the new estimate includes no allowance for such silting,

the former may be regarded as being based on the worst view of

the case and the latter on the best. Some allowance should be

made, however, for such dredging as will unavoidably be done

below the intended maximum depth. But against this has to be set

the fact that 5 fathoms below "Rambler" Zero is 5 fathons and 6

inches below any but a phenomenal low tide. (The zero recently

adopted by the Admiralty for future sounding in these waters is

8" higher than "Rambler" Zero. See Appendix 11.). An inch in

depth of dredging over the entire area amounts to about 353,000

tons.

:

24.

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