=Reconnaissance for triangulation points= was carried out simultaneously with the triangulation itself. The distance of likely looking peaks was determined either by intersecting them from distant stations, or by special small triangulations from short bases, and such selection made as seemed most likely to secure well shaped figures and a good command of surrounding country. As a rule, the highest summits were selected as main (occupied) stations, while all other prominent peaks and other features were fixed by intersection from two or more main stations. The form adopted for the main triangulation net was a series of quadrilateral figures with diagonals, combined with centric polygons, all the angles of the figures being generally measured. The average length of side was about thirty-five kilometres. =Beacons.=—Main stations were marked by wrought-iron beacons, consisting of two lengths of stove piping about 15 centimetres diameter by 1½ metres long, the upper length fitting into a faucet made by splaying out the lower tube. Near the top of the tube were affixed four sheet iron wings, bolted on to angle iron cleats. A conical cairn of stones was built up round the tube, nearly up to the wings, so that the beacon when erected was about three metres high, two metres in diameter across the base of the cairn, and about a metre wide across the wings. The beacons were taken down while a station was being occupied, and replaced on leaving. Intersected points were sometimes marked with a beacon or cairn, but in general the peaks were simply bisected from several stations, as it was found that this gave sufficiently accurate results. =Measurement of Horizontal Angles.=—Angles were measured with a 6-inch theodolite furnished with reading microscopes graduated to 10″ and permitting of reliable estimations to 1″. The angles between main points were read on four arcs to eliminate circle errors. Intersected points were observed on one arc only. The average error of closure of main triangles was 3″·3. =Field Computation and Plotting of Triangulated Points.=—The triangles were computed by the ordinary method, but the angles were rounded off to 10″ to enable the sines to be taken direct from the logarithmic tables, and the logarithms were only taken to five places. The length of the sides having been thus found, the geographical positions were found by the ordinary _L M Z_ computation, using, however, only two latitude terms and 5-place logarithms, while azimuths were only taken out to the nearest 10″. The abbreviated form of computation used will be best illustrated by an example:—[63] _Computation of Position of_ △ _No. 260 from No. 275._ _l_ = 20042 m. { φ = 23° 55′ 30″·6 275 { _Z_ = 64° 29′ 20″ E of N. { λ = 34° 54′ 36″·9