xii PREFACE. 



vations, and unless the original data are published, 

 geographers and future travellers are unable to judge 

 to what degree the separate observations differed, or 

 what reliance is to be placed on the observing powers 

 of the earlier traveller. 



In giving to the public a much-improved map of 

 the field of my African explorations south of the 

 Equator, I am glad to have been able to correct the 

 errors of my former one. Most of the principal posi- 

 tions were there placed much too far to the east and 

 north ; and even those given by Dr. Petermann in 

 his second map, already mentioned, prove to be a few 

 miles too far in the same direction. Mr. Dunkin has 

 stated, at a meeting of the Royal Geographical Society, 

 that he considers the position of Mayolo as perfectly 

 well determined by my observations : this may there- 

 fore be considered a fixed point by cartographers in 

 reviewing my geographical work. But I must men- 

 tion that two places, to the west of Mayolo, namely, 

 Niembai and Obindji, have been placed on my map 

 according to a calculation of distances travelled, as I 

 had taken only one observation at each place. By 

 the position of Mayolo, and that of the Samba Na- 

 goshi Falls, visited by me in the last journey, I have 

 been able to correct greatly the course given in my 

 former map, and adopted by Dr. Petermann, of the 

 great River Ngouyai. Unfortunately, my longitudes 

 of these places render it difficult to connect my map 

 with that given by Lieutenant Serval, of the Ogobai 

 between Lake Anengue and the junction of the 



