28 SCIENCE IN AFRICA 



ditions well enough, mainly because there are relatively permanent 

 physical features such as hedges, ditches, and fences to safeguard 

 the rights of the owners. 



In Africa farms are for the most part unfenced and only par- 

 tially developed. The title of a landowner rests on a plan attached 

 to his deeds on which are shown the beacons marking the corners 

 of his land and the lengths and bearings of his boundaries. These 

 lengths and bearings have been calculated by a cadastral survey 

 based on the controlhng triangulation, and the co-ordinates of 

 the corner beacons have been mathematically computed in rela- 

 tion to the framework provided by that triangulation, and regis- 

 tered on plans in the Survey Records Office. The field notes of 

 the original survey are also registered in that office. If the beacons 

 are destroyed, as they often are, ownership is still safeguarded by 

 the assurance that they can be replaced from registered data with 

 the accuracy attained in the original survey. Such a system is essen- 

 tial to all security of ownership in territories such as South Africa 

 or Kenya, and the work which it entails absorbs the entire energies 

 of the survey staffs which the Colonies have found it possible to 

 maintain in times of depression. 



The history of land surveying in South Africa illustrates the dis- 

 advantages which ultimately result from cadastral surveys made 

 without adequate geodetic control. This question is so important 

 that a few quotations from authorities in South Africa are given 

 by way of illustration. 



The Government of the Cape Colony in 1878 appointed a 

 Commission 'to make a full investigation into and report upon a 

 more adequate means of testing the accuracy of land surveys in 

 the Colony'. The principal recommendation (No. XVIII) was 

 that a secondary triangulation based upon the geodetic coastal 

 chains of Maclear and Bailey be extended over the Colony (1878). 

 A year later Sir David Gill, in submitting his famous scheme for 

 the geodetic survey of South Africa to the High Commissioner, 

 objected to this uncontrolled triangulation. He insisted that a 

 scientific system of triangulation 'is much more economical both 

 in execution and reduction than that recommended in Section 

 XVIII of the report; and coupled with secondary triangulation 

 can be made to afford any desired accuracy' (1880), 



