CO129-329 - Governor Nathan - 1905 [7-12] — Page 508

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19' 2" below the Copper Bolt ((8)), equivalent to 16" below Ordnance Datur. the relative note on each of the three charts,

1459, 3279, and 3280, has been altered within the last few

months, as shown in Appendix 11.

15.

The Consulting Engineers say nothing about

the zero of the later editions of Chart 1468, and nothing defin-

ite is noted about it on the chart itself; but by measuring on it (Chart 1468) and also on Chart 1459, a certain area enclosed

by the 5 fathom contour lines, and other definite lines, I for-

-terly proved (20) that the soundings on both these charts were referred to the same zero. Indeed a rapid comparison of the con-

-tour lines on the two charts is enough to satisfy almost any

one that this is so

16.

1

1 concur in the Consulting Engineers'

recommendations ((17)) as to fixing a datum or zero, although I

do not see the advantage generally of adopting a moderately low

tide. Ey referring to an extremely low tide all minus quantities

are removed from fide Tables, and a great many from working draw-

-ings. In the present case, however, it will be advisable to

adhere to the "Rifleman" Zero, alias Ordnance Datum. It is prac-

-tically the level that the Consulting Engineers recommend (see

Appendix 111), and it has been consistently used by the Public

Works Department for many years, and is well known to local

engineers and architects generally.

17.

In my former remarks (128 and 42) on rean

sea level as a point of reference, 1 may not have made it clear

that 1 meant it to be a final point of reference, as it is the

only constant level in the world. Bench Marks for immediate

reference, and a selected Low Water as a Zero, are of course

necessary for working purposes; but bench marks have a way of

getting lost, and there are many different Low Waters. It may be

possible in future to preserve with practical accuracy the level

of