September 17, igo8] 



NA TURE 



501 



governing colonies. As on this occasion I was consider- 

 ing the whole question more exclusively from the military 

 side, no reference was then made to the question of 

 cadastral maps, and it was tacitly assumed that these 

 would fall to be constructed by the land office or a land 

 survey department belonging to each separate colony. On 

 the present occasion we are not restricted to the military 

 point of view, but are permitted a wider outlook. Our 

 task is to consider the map in all its aspects, both as 

 regards its method of construction and its ultimate use, 

 whether for military, administrative, engineering, or purely 

 scientific purposes. This enlargement of our scope does 

 not, I think, modify our previous conclusions, and were 

 I now called upon to devise a scheme for the mapping of 

 British Africa, I should base it upon the principle of a 

 central Imperial body for executing the triangulation and 

 topography, leaving the land survey to local organisations. 



The arguments in favour of this policy are manifold. 

 As regards the triangulation they hardly require stating. 

 It will be obvious to all that such work must be closely 

 coordinated, and that some central, directing head is 

 imperatively called for. The enormous waste of money 

 that is ultimately involved by tolerating imperfect work, 

 of which many examples could be cited, is alone a sufficient 

 justification for holding this view. VVe may, however, 

 pause to examine a little more closely into the advantages 

 of centralisation as regards one particular operation in a 

 survey. That is the measurement of the initial base line 

 upon which the accuracy of the whole framework depends. 

 This task used to be one of the most laborious and 

 difficult with which the surveyor is confronted. The 

 apparatus employed, some form of compensation bar, was 

 cumbrous and difficult to use, the site selected had to be 

 levelled, and the preparatory alignment carried out with 

 the most scrupulous care. Thus the Loch Foyle base for 

 the triangulation of Great Britain and Ireland was about 

 six miles long, and the actual measurement, quite apart 

 from the time spent on the preparation of the ground, 

 took sixty days, an average rate of work of just more 

 than 500 feet per working day. 



A few years ago the discovery was made of the nickel 

 steel alloy with a very small or zero coefficient of 

 expansion, the so-called invar. This valuable metal, by 

 abolishing the necessity for any temperature correction, 

 has enormously simplified all physical measurements of 

 length, and, a fortiori, those measurements, such as base 

 lines, which are perforce done in the open air and over 

 a large range of temperature. Survey bases are now 

 measured with an invar wire stretched to carefully regu- 

 lated tension, and either laid along a flat trough, or what 

 appears to give equally good results, hung freely between 

 supprarts. The gain in precision due to the avoidance of 

 errors of expansion or contraction in the measuring 

 apparatus is substantial, while the gain in rapidity is 

 very great. Thus, aj a contrast to the Loch Foyle base, 

 let me give a short account of the measurement of a 

 base in Spitsbergen by the Russian party of the joint 

 Swedish and Russian missions in 1900, extracted from a 

 review already written for the Geographical Journal. 



The conditions for accurate work were very unfavour- 

 able : no site even approximately flat could be found, and 

 the base was therefore irregular in contour and traversed 

 rough and in some parts marshy ground. The weather 

 conditions were far from ideal. The cycle of operations 

 was as follows : An auxiliary base 175 metres long was 

 measured with Struve's apparatus, twice before the main 

 base n^easurement and twice afterwards. The two wires 

 used ft • the main base were standardised on this subsidiary 

 base four times, twice before and twice after use. The 

 main base, 6-2 kilometres long, was measured twice In 

 each direction by each of two wires, eight measures in 

 all. The limit of error In the final value was 17 milli- 

 metres — say, one part in 360,000. 



The whole of these operations, including the laying out 

 of the standard and the comparison of the wires, were 

 completed in a period of three weeks ; Monsieur Back- 

 lund, who superintended the actual measurement, left the 

 observatory at Pulkowa on June 11 and returned to it 

 on July 24. It was therefore possible to standardise the 

 wires not only by the check base upon the spot, but also 

 by the permanent standards of the observatory within 



O. 2029, VOL. 78] 



three weeks of their use for the actual measurement. It 

 need hardly be pointed out that this was eminently 

 favourable to the attainment of the highest exactitude, 

 and we have here a marked example of the value of 

 centralisation. The proposed trigonometrical survey de- 

 partment of Africa would probably find it advantageous 

 to adopt similar procedure, and, instead of trusting a base 

 measurement to a local staff unacquainted with the work, 

 it would send out one or two men of highly trained 

 technical skill equipped with the best apparatus. The 

 money spent in journeys would be more than saved — ■ 

 firstly, by the unquestionable gain in accuracy and the 

 consequent avoidance of the costly necessity for repeat- 

 ing bad work ; and, secondly, by the gain in time, due 

 to the fact that the local staff would not be called upon 

 to learn the use of an unfamiliar set of instruments. 



Similar advantages would arise from a partial specialisa- 

 tion of the angular measurements. Thus the first-class 

 observer with a theodolite must possess certain qualities of 

 eyesight, health, and judgment, rarely combined in one 

 individual. When such a combination of qualities is found 

 it should be made the best use of, and a good man should 

 not be wasted on second-class work. At present, upon 

 the system of regarding each colony as an isolated unit, 

 it is not possible to employ every man to the highest 

 advantage, and there are doubtless many examples at 

 present In Africa of able men being set tasks much below 

 the standard of their ability, and, per contra, men of no 

 such qualifications being given work beyond their powers. 

 It Is only by working with an extended organisation, 

 employing a large staff and responsible for a large area 

 of country, that any approximation can be made towards 

 that Ideal wherein every member of the establishment Is 

 used to the best advantage according to his special 

 qualifications. 



To turn from the triangulation to the question of topo- 

 graphy, we shall find analogous argi.mnents in favour of 

 entrusting this work to one central department. Whether 

 we consider the necessity for a uniform system of train- 

 ing for the topographer, or whether, looking at the matter 

 from the other side, we consider the desirability of a close 

 degree of uniformity in the resulting map, we arrive at 

 the same end. Nor need we confine ourselves to theo- 

 retical arguments; practical results are before us as 

 examples. It is not possible at the present moment to 

 point out a single case of a thoroughly satisfactory topo- 

 graphical map of any country whatever which has not 

 been executed by men trained in a properly organised 

 survey department or, what Is equivalent, in the Corps of 

 Royal Engineers. Examples of failure to accomplish this 

 are numerous. Thus we have the cases of the British 

 Colonies in South Africa before the war ; of Canada, where 

 no topographical map existed until two years ago, when 

 the work was taken up by the military department ; and 

 of Ceylon, where, in spite of the vast sums spent on 

 survey' and the small size of the island, no topographical 

 map of the slightest pretensions to completeness exists of 

 any part of the country. 



it may also be noted that, especially in the case of a 

 developing country, it is of enormous advantage that the 

 map shall be begun and finished within some reasonable 

 lime. If a long interval elapses between the commence- 

 ment and the completion, the first sheets are out of date 

 before the last are done, and the whole exhibits a most 

 undesirable lack of uniformity. 



With a central organisation the mapping of each pro- 

 tectorate can be taken up in turn and dealt with rapidly, 

 thus producing a homogeneous map impossible to a small 

 local body. Upon the converse point, the question as to 

 whether our central department should or should not 

 undertake cadastral survey, the arguments are perhaps not 

 so one-sided. It is, however, quite clear towards which 

 side the balance of advantage tends. Taking into account 

 the intimate connection of "the cadastral survey with the 

 system of land holding and land taxation, the fact that 

 these systems necessarily vary and that as a financial 

 matter 'of account the receipts and expenditure of each 

 colony are separate, It is not difficult to see that the land 

 survey is better left to local control. This would not 

 preclude any particular colony from arranging with the 

 central bodv for the execution of any definite piece of 



