170 



Expedition into Central Africa, 



[April 



security of guidance and prospect of safe return of the Expedition^ 

 will of course depend on obtaining an exact knowledge and preserv- 

 ing a faithful record of its route, which can only be done by the aid 

 of Astronomical observations made with due regularity and precau- 

 tion, not only at such stations as form the most interesting features at 

 the moment, in the eyes of those concerned, but at every station 

 where the Expedition may rest long enough to permit observations 

 to be taken deliberately, and with due regard to safety both of the 

 observer and instruments. The track of a caravan on land, as of a 

 ship at sea, is defined as well by the less as the more remarkable 

 points through which it passes, and it may very easily happen that 

 stations of the highest interest in a commercial, political, or physical 

 point of view, may, by reason of that very interest, be inappropriate 

 for selection as principal observing stations, either from the attention 

 of every individual being distracted to duties of immediate necessity 

 or from the risk attending the exhibition of instruments in the un- 

 avoidable presence of a rude, curious, and suspicious population. In 

 all such cases it will be proper to connect by observations of a less 

 elaborate nature, those stations with others not far distant, which, 

 although less intrinsically important, may be easier of exact deter- 

 mination. The Committee would therefore recommend, that stations 

 of observation be classed as either 'primary or secondary : those to 

 be considered primary stations whenever the circumstances may ap- 

 pear particularly favourable, by reason of leisure from other occupa- 

 tions, expected duration of halt, and freedom from annoyance, to 

 afford a good determination of the longitude and latitude, such as may 

 serve to render them useful for Zero points, to which the secondary 

 stations may be referred, either by dead reckoning of time and dis- 

 tance or by such less elaborate observations as can be obtained at the 

 secondary stations themselves. Of course, hov/ever, should circum- 

 stances permit, the more important in other respects the point which 

 can be made a primary observing station the better, and the Committee 

 would expressly notice Griqua Town, Lattakoo, Kurrechane, and 

 Meletta, as points of which the Geographical position should be de- 

 termined with care by observations on the spot, and the observations 

 then made transmitted home along with the latest communications 

 with the Colony. Since, however, the circumstances which may ren- 

 der stations objectionable as primary points are mostly of a moral or 

 political nature, it is expected that no great difficulty will occur in fix- 

 ing them at positions of especial geographical interest, as at the con- 

 fluence of rivers, at the extreme borders or on the culminating points 

 of mounting ranges, on remarkable rocks, &c. or at least of determi- 

 nating their bearings and relative situations with respect to such 

 prominent features, with some degree of exactness. A combination of 

 circumstances of this kind of local interest will of course have its due 

 weight in determining (casteris paribus) the halt of the expedition. 



At primary stations the Committee recommend the assiduous ap- 

 plication of every instrumental means for the determination of the- 



