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The great pioneer of accurate survey methods in New Zealand; under the Provincial Government was the late Mr. J. T. Thomson, F.R.G.S., then Chief Surveyor of the Province of Otago, who became in 1876 first Surveyor-General of New Zealand, after the establishment of Responsible Government. It was in 1856 that he established a rapid system of reconnaissance survey and a minor triangulation. In this he was ably assisted first by Mr. Alexander Garvey, and later by Mr. James McKerrow, F.R.A.S., who afterwards succeeded Mr. Thomson in the Surveyor-General-ship of the Dominion. Briefly, the process was to observe latitudes at stations about 60 miles apart on the same meridian, and to use the base so obtained for fixing the positions of all prominent mountains and other important features. Regarding Mr. McKerrow's surveys, the country did not lend itself to Mr. Thomson's system of astronomical bases. Mr. McKerrow selected three mountain-peaks, 60 or 70 miles apart, at which the latitude was determined, as also very carefully the times at each place, and by means of chronometers conveyed from point to point the longitude of these base points was ascertained; and, following on this, by ordinary triangulation methods, the topography of the country was filled in. It may be mentioned that on subsequent close trig, and topographical surveys taking place, the remarkable accuracy of these early reconnaissance surveys, costing as they did only a few shillings per square mile, has been fully demonstrated. The process was extremely rapid, as no stations were built, and was suited to the mountainous nature of the country, while a very fair degree of accuracy was attained. By these means a sufficiently accurate survey of Otago was effected, and used for the first disposal of the early pastoral runs, besides being utilized for many purposes of early settlement, leaving closer detail surveys to follow, as well as the marking-out of electoral, road, registration, and other districts. Information was also afforded of the heights of mountains, passes, lakes, and of distances between geodesical stations. Minor triangulation followed on this, and was used to check and control all section surveys. The limit of error in traverses then adopted (following Indian practice) was 8 links to the mile, and, as it was desirable that the error on the ground should never exceed 10 links in these early surveys, the minor trig, stations were established at an average distance of 2\ miles apart. Although the permissible error was 8 links to the mile, most of the work when checked showed errors ranging from half a link to 6 links per mile. The maximum error allowed by regulation has since been reduced to 4 links in rural surveys, and 1 link in town surveys; but in actual practice the error rarely exceeds 2 links per mile in rural surveys. The Province of Otago was divided into meridional circuits of about 120 miles in longitude and 90 miles in latitude; in each circuit the true meridian was observed at the initial station, and a system of standard bearings was extended wherever required, stations being established at intervals of about 12 miles. Each meridional circuit was divided into survey districts, 12 miles square, with sides parallel perpendicular to the initial meridian. Thus each survey district had a geodesical station within it, and a number of carefuly observed standard bearings, so that in the event of settlement surveys being carried out a minor triangulation could at once be put in hand, using the geodesical stations as the initial, and the standard bearings for the true, meridian. Each survey district was thus complete in itself, and either had its own base-line or extended the triangulation from an adjacent district. In this way very great flexibility was obtained, and no more triangulation need be carried out than that required for the settlement surveys in hand or anticipated. Triangulation with an accuracy in advance of the original Otago methods was carried out gradually throughout the Dominion after the abolition of the provinces in 1876, when Mr. Thomson took complete control as Surveyor-General of the Dominion, Mr. McKerrow being Assistant Surveyor-General. Long before this date, however, Captain T. Heale, Inspector of Native Surveys under the General Government, and Mr. H. Jackson, F.R.G.S., Chief Surveyor of the Wellington Province, had started in the Provinces of Auckland and Wellington a secondary system of triangulation, Captain Heale's work extending over a large area in the North Island", principally in connection with Native-lands surveys, whilst Mr. Thomas Humphries, Chief Surveyor of the Taranaki Province irfthe North Island, also made a beginning with a triangulation on sound lines, this triangulation governing his detail surveys. The main object of the triangulation has been practical utility rather than a strictly scientific work, and thus nearly every survey in Otago since 1856 may be said to be founded upon or connected with traingulation, and since 1876 the same statement applies to the whole Dominion. The minor triangulation has always been the forerunner of settlement work, and has formed part and parcel of it, and has generally been accompanied by topography on a scale of 40 chains to 1 in. These early trig, surveys met all settlement wants, and the topographical plans have given the fullest details regarding the character of the country, altitudes, soils, road routes, and all matters relating to the opening-up of land for settlement. Since 1876 in many of the more settled districts the triangulation has been revised from time to time, and as the topography becomes better known it has been possible to increase the lengths of the sides of the triangles.