September 17, 1908J 



A'. 4 rURE 



499 



refuses to pay for an arc along the thirtieth meridian in 

 the fear that directly this is completed he will be asked 

 to pay for one along the twentieth meridian, and then 

 along the tenth, and so ai infinitum. It behoves us, 

 therefore, as practical men to make sure that our demands 

 are reasonable and limited to the actual requirements of 

 the case, and where such limits cannot be set we should 

 make this fact clear at the outset. When, however, it 

 is possible to set such limits, we should not hesitate to 

 do so ; and in the case of the African arc this latter course 

 is fortunately possible. 



If we take the map of Africa we shall see that the arc 

 along the thirtieth meridian passes through, or near, all 

 the colonies of British South Africa, close to British 

 Central Africa, or Nyasaland, through Uganda, and is 

 thus connected with British East Africa, through the 

 British Soudan and through Egypt. There remain abso- 

 lutely untouched by it only the West Africa colonies — 

 Nigeria, the Gold Coast, Sierra Leone, and the Gambia. 

 These latter will eventually get their geodetic framework 

 by an extension southwards of the French triangulation 

 of Algeria, a work of a high order of precision. We are 

 therefore entitled to say — and I take this opportunity of 

 saying it wi^i all due emphasis — that with the exception 

 of some triangulation to join the West African colonies 

 with the French triangulation, the arc along the thirtieth 

 meridian is the only primary triangulation required for 

 the adequate mapping of the whole of British Africa. The 

 remainder of the gc-odetic framework can be supplied by 

 ribs of secondary triangulation branching out from the 

 main backbone, such as the line already completed along 

 the boundary between British and German East Africa, 

 passing to the north of the Victoria Nyanza and thence 

 westward to the thirtieth meridian. 



You will observe that I here speak only of the triangula- 

 tion required for mapping purposes, not of that demanded 

 by the geodesist for the study of the figure of the earth. 

 The latter is satisfied only with a survey of the highest 

 attainable precision covering as large an area of the earth's 

 surface as possible, or at all events with arcs, both 

 meridional and longitudinal at frequent intervals. It can- 

 not be other than a very long period before the whole of 

 Africa is surveyed upon this scale of accuracy, and in the 

 meantime we must devote ourselves to the far more urgent 

 duty of mapping the country, leaving the more remote 

 and abstract task to our descendants, well satisfied if in 

 our hands the foundations have been well and truly laid. 



Furthermore, as we shall see presently, if we are pre- 

 pared to recognise as a national duty the minutely precise 

 survey of our own land and of all territories under our 

 flag — and I do not see how any reasonable man can with- 

 hold this recognition — then there are duties of this nature 

 lying closer to our hands than any to be found in Africa. 



Having thus passed in brief review the ultimate geodetic 

 basis of our African surveys, let us enter more into detail 

 and glance at the actual survey work now in progress in 

 the different regions of the continent. 



In British South Africa, as we have already noted, the 

 political conditions are at present unfavourable to any com- 

 prehensive scheme of operations. There is, however, in 

 progress a first-class topographical survey of the Orange 

 River Colony and a reconnaissance survey of Cape Colony. 

 The former is an excellent example of the class of work 

 that can be done by a small military party of the highest 

 technical training working upon systematic lines, and I 

 should like to devote a few minutes to a short descrip- 

 tion of the methods adopted and of the results obtained. 



The survey party consists of two Royal Engineer oflficers 

 and four non-commissioned officers, the former undertaking 

 the triangulation and the general supervision of the field 

 work, and the latter the plane tabling. The positions are 

 primarily based upon the points of the geodetic survey 

 broken^ up into a secondary triangulation with sides 

 averaging ten miles. In 1907 'the average triangular error 

 of the secondary work was 29 seconds of arc, and the 

 greatest linear errors of displacement, as tested by the 

 geodetic triangulation at the end of a chain forty-five 

 miles long, were three feet in latitude and two feet in 

 longitude. The probable error of a trigonometrical height 

 was under a foot. You will see, therefore, that the 

 accuracy is ample for all mapping purposes, even upon 

 XO. 2029, VOL. 78] 



large scales, and the degree of precision is in excess o£ 

 that demanded for a topographical map on the scale of 

 two miles to an inch. The rate of progress and the low 

 cost of work are, however, no less notable than ita 

 accuracy. The actual rate of out-turn is about eight 

 square miles per day per man, or for the whole party 

 twenty-three square miles of detail survey per diem, and 

 the number of trigonometrical points fixed about three 

 hundred per annum. The cost works out to about eight 

 shillings per square mile of the completed map, and the 

 whole area of 47,000 square miles will be finished, printed 

 and published, in five and a half years. 



These remarkable results are due in a large measure to 

 the energy and organising power of the officer in charge. 

 Captain L. C. Jackson, R.E. The detail survey is done 

 in sheets fifteen minutes square, each non-commissioned 

 officer being given one complete sheet, which he works at 

 until finished. Four such sheets are therefore in progress 

 at any given time, and each sheet takes about six weeks. 

 Seeing the rapid rate of progress maintained, it might 

 perhaps be thought that the country is a particularly easy 

 one for the topographer. Such is, however, by no means 

 the case. It is true that there is an entire absence of the 

 surveyor's greatest impediment, large areas of dense 

 forest, but there is much broken and difficult country, 

 rising in places to altitudes of above 7000 feet. 



In Cape Colony the reconnaissance survey is of a some- 

 what similar character, but owing to the large area of 

 the country and to the small amount of money available 

 the work has perforce to be of a more rapid nature. In 

 Natal, Bechuanaland, and Rhodesia no survey is at present 

 in progress. 



Passing northward through Africa, we come to the 

 British Protectorate of Nyasaland, formerly called Britisb 

 Central Africa. Of this country a certain number of maps 

 exist purporting to give topographical detail ; but as they 

 are not based upon any framework of triangulation, and' 

 as much of the detail only depends upon rough sketches, 

 it is impossible to say how far they can be accepted as 

 correct representations of the ground. 



It is most unfortunate that financial considerations 

 prevent the execution of any systematic trigonometr'cal 

 survey. The absence of such, and the fact that maps are 

 being made which must inevitably be withdrawn and re- 

 placed by others in the future, will undoubtedly be the 

 cause of ultimate waste of money. 



Passing northward again we come to the large and 

 important protectorates of British East Africa and Uganda, 

 in both of which systematic surveys are in hand. The 

 geodetic framework is supplied by a triangulation along 

 the Anglo-German boundary, connected with chains of 

 triangles along the railway in the neighbourhood of 

 Nairobi. In Uganda proper there is also a triangulatiom 

 covering a substantial area. As already noted, all this 

 work will eventually be tied into the thirtieth meridional 

 arc, though it is not likely that the final adjustment of 

 geodetic positions thus arrived at will necessitate any sub- 

 stantial alterations upon the maps. 



In both protectorates topographical surveys are in hand, 

 and maps on the scale of two miles to an inch will be 

 issued. In British East Africa, under the able direction 

 of Major G. E. Smith, R.E.^ rapid progress is being 

 made. This topographical mapping is additional to the 

 cadastral maps also in progress in both countries. These 

 latter are required for property purposes, in Uganda for 

 demarcating the estates given over to the native inhabitants 

 of the country under the agreement of 1900, and in East 

 Africa for attachment to title-deeds of lands alienated for 

 farming or stock-raising. 



In the Soudan the enormous area of the country — more- 

 than a million square miles — and the limited funds avail- 

 able have prevented any systematic survey being taken up. 

 A large amount of reconnaissance mapping has been done, 

 and a series of sheets on the scale of 1/250,000 (four miles 

 to an inch) have been published. These are corrected and 

 Improved by officers and Government officials as oppor- 

 tunity offers. The energies of the Survey Department are 

 almost entirely spent in meeting urgent local requirements 

 in the shape of cadastral maps of the cultivated areas 

 along the river. 



Somaliland, a British protectorate which came into un- 



