1 84 DAVID LIVINGSTONE. [chap. ix. 



by longitudinal ridges on the east and west ; that origin- 

 ally, the depressed centre had contained a vast accumula- 

 tion of water, which had found ways of escape through 

 fissures in the encircling fringe of mountains, the result 

 of volcanic action or of earthquakes. The Victoria Falls 

 presented the most remarkable of these fissures, and thus 

 served to verify and complete his theory. The great 

 lakes in the heart of South Africa were the remains of 

 the earlier accumulation before the fissures were formed. 

 Lake 'Ngami, large though it was, was but a little fraction 

 of the vast lake that had once spread itself over the 

 south. This view of the structure of South Africa he 

 now found, from a communication which reached him at 

 Linyanti, had been anticipated by Sir Roderick Murchison, 

 who in 1852 had propounded it to the Geographical 

 Society. Livingstone was only amused at thus losing 

 the credit of his discovery ; he contented himself with a 

 playful remark on his being "cut out" by Sir Roderick. 

 But the coincidence of views was very remarkable, and it 

 lay at the foundation of that brotherlike intimacy and 

 friendship which ever marked his relation with Murchison. 

 One important bearing of the geographical fact was this : 

 it was evident that while the low districts were unhealthy, 

 the longitudinal ridges by which they were fringed were 

 salubrious. Another of its bearings was, that it would 

 help them to find the course and perhaps the sources of the 

 great rivers, and thus facilitate commercial and missionary 

 operations. The discovery of the two healthy ridges, 

 which made him so unwilling to die at the mouth of the 

 Loangwa, gave him new hope for missions and commerce. 

 These and other matters connected with the state of 

 the country formed the subject of regular communications 

 to the Geographical Society. Between Loanda and Quili- 

 mane, six despatches were written at different points. 1 



1 The dates were Pungo Andongo, 24th December 1S54 ; Cabango, 17th May 

 1855 ; Linyanti, October 16, 1855 ; Chanyuni, 25th January 1856 ; Tette, 4th 

 March 1856 ; Quilimane, 23d May 1856. 



