Aug. 29.] THE NEW ZEALAND GAZETTE. 2733

polygonal or quadrilateral series, and it must be closed upon adjacent triangulations.

Limit of error.

18. The maximum error in minor triangulation must not exceed 6 in. to the mile, represented by the discrepancies in the computed values of common sides in the polygons and quadrilaterals, or by the close on to another series; the error in the summation of angles of a triangle can, with care, be kept under 10″, and must not exceed 20″. All work having error in excess of these limits will require revisal.

Computations.

19. The calculation of the triangulation is to be made and recorded upon the printed forms, seconds corrections being systematically applied so as to make the side values and closures harmonize. When the final values of the sides and angles have been determined, the positions of all stations are to be calculated on the meridian and perpendicular of the initial station of the circuit, and a table of the same prepared, from which maps must be constructed to prescribed scale. (See Appendices 2 and 3.)

Mapping.

20. The trigonometrical work in each survey district is to be mapped on one plan, which should show major or geodetical stations with three, and minor stations with two, concentric pink circles, with their alphabetical letters or numbers and local names, which should be the original Native ones where obtainable. A base-line should be shown in pink colour, other lines in blue, bearings in blue, calculated distances and bearings black, the observed angles and the summation in the middle of each triangle black. (See Appendix 7.)

21. The meridian and perpendicular values, and the respective altitudes of each station above mean sea-level, should be tabulated on the plan. There should also be a note giving the results of the several measurements of the base-line, if any, and on completion of a triangulation of any class the surveyor should send in a special report stating the instruments used, number of triangles, maximum and average error of angular measurement, detailed list of closures, clear statement and diagram of origin of bearing, originating sides, closing and verification sides, and general remarks.

TOPOGRAPHICAL SURVEY.

Described.

22. Combined with the trigonometrical operations a topographical survey is to be made of the natural features, also roads, tracks, remarkable objects, natural and artificial, &c., and these must be shown on a topographical map. For altitudes, vertical angles are to be observed to prominent objects and important points such as peaks, passes, valleys, and confluence of streams. A surveyor with a good eye can make a serviceable sketch-map from the trig. stations by means of cross-bearings, and bearings with estimated distances of objects; but if the country be intricate, bearings from intervening positions should be taken. Prismatic compass and aneroid may be used for filling in detail; in forest country this is especially necessary, as is also the determination of heights of saddles and valleys, river-beds, lakes, swamps, &c.

Topographical map.

23. The topographical map must show the trig. stations as named, lettered, or numbered, trigonometrical heights in feet (in pink), barometrical heights also in pink and marked “Bar.,” streams (in blue), hills shaded (in Indian ink), the Native or local names of places, streams, hills, &c.; roads in use (in firm burnt-sienna lines), tracks (dotted burnt-sienna), bush (green), suggested main lines of future roads (in firm pink line), and any other features, natural or artificial, which can be shown. Shade the boundary of the district in colour. (See Appendix 8.)

STANDARD TRAVERSE.

Marking of stations.

24. As implied by its designation “standard traverse” is a more elaborate and accurate class of work than ordinary traverse,