2732
THE NEW ZEALAND GAZETTE.
[No. 77

distinct; or the contrary — and any other circumstance bearing
upon the reliability and satisfactory character of the observations.
(See Appendix 1.)

Computations.

10. The computations of the series of triangles should emanate
    from a base or well-established sides, and be carried forward sys-
    tematically so as to insure the best values obtainable, avoidance of
    discrepancies and disturbing factors, and the greatest weight ob-
    tainable for the value of sides in the series common to other trian-
    gulations.

Verification bases.

11. As bases are capable of more accurate determination than
    angular measurements, verification bases, measured in a similar
    manner to the original base, should be established at approved
    intervals.

Mapping.

12. Major triangulation is to be delineated upon mounted anti-
    quarian paper to a scale of 1 in. to two miles.

MINOR TRIANGULATION.

Breaking down.

13. When the country is already covered by a major triangula-
    tion, it will be necessary to incorporate therewith a minor series
    of triangles. This can be effected by “breaking down” from the
    major sides by a homogeneous network, which must be brought
    into harmony with the major series by the method of Ray Trace
    computation.

Procedure similar to major processes.

14. The measurements of a base, where major triangulation is
    not available, and also the observations and computations, are to
    be conducted in a similar manner to those prescribed for major
    triangulation, and the datum for computation of heights taken
    from the standard maps.

Trigonometrical stations.

15. Stations should be as nearly as practicable from two to
    four miles apart, and are to be marked in the following manner:
    Iron tubes, 2 in. internal diameter, cut to 2½ ft. length, are to be
    inserted into cast-iron plates with sockets, and secured by iron
    pins. The survey district distinguishing alphabetical letter of the
    station is to be cut on the upper end of the tube, or the circuit
    numeral stamped in, and the tube sunk to a depth of 2 ft. 3 in.
    and well rammed, a bottle being first placed below it. Excepting
    in sandy soil, a circular ditch, 12 ft. diameter, 1 ft. deep, and
    18 in. wide, should be dug around the tube, and the soil excavated
    spread evenly within the circle. On rocky ground, where a ditch
    cannot be dug, a circle of large stones should be substituted. It is
    not desirable to build mounds, but at times these may be found
    necessary; the surveyor will in such cases exercise his own judg-
    ment. If mounds are built, the exterior rim should be of stone
    or sods, with earth in the centre. In positions where the nature
    of the soil may require modifications, special directions will be
    given. (See Appendix 5.)

Signals.

16. The signals and flags to be used must be varied to suit the
    positions and relative elevations of the stations. Metal or timber
    pyramids of the regulation pattern are to be provided for the prin-
    cipal stations, but temporary and smaller ones will suffice for the
    others. (See Appendix 6.)

Triangles and their arrangement.

17. The stations are to be selected so as to furnish well-con-
    ditioned triangles, no angles being less than 30° nor greater than
    120°, except under special circumstances. As far as practicable,
    overlapping triangles are to be avoided, excepting where they serve
    to form quadrilaterals, and each triangle should appear on the
    map distinct from others; but when a valuable additional series
    of triangles can be constructed from the observations these should
    be plotted and shown on a separate plan. It is essential that,
    whenever practicable, the triangulation be carried forward in a