44 THE TANGANYIKA PROBLEM. 



of this nature has gone on ; and the only further demon- 

 stration which is required to make the tale complete are 

 some observations which will show that the floor of the valley 

 of Nyassa has become, or is becoming, actually thrust down. 

 Such evidence is readily to be obtained at the north end of 

 the lake. The water of Nyassa has fallen many feet within 

 no great number of years, and in consequence, wide plains 

 of old lake deposit and alluvium covering what was once its 

 floor have become dry land near Karonga and further north. 

 At the end of 1895, when I first visited the lake, the water 

 of Nyassa was shown by observations made by the officers 

 of the gunboats to be lower on the whole than it had been 

 for many years ; but notwithstanding this, I was shown to 

 my intense surprise a number of old trees not far from 

 Karonga, which were standing about two hundred yards 

 in the water of the lake, and the trunks of which were 

 then submerged some five feet. Moreover, the old natives 

 of the district, whom Dr. Cross interrogated on this subject 

 for me, assured us that they could remember a time when it 

 was possible to walk out to these same trees, which were 

 then not near the water at all, and at whatever rate the 

 change in level has taken place, it is quite clear that it can 

 only have been produced by local subsidence of the ground, 

 i.e., by the sinking of the floor of the Nyassa Valley during 

 the life of these particular trees. 



Thevalleyof Nyassa, like that of Tanganyika, is continued 

 beyond the lake to the north (see map, opposite p. 48), and 

 although its magnitude becomes lessened and partially filled 

 up, there is no doubt that the individuality of the depression 

 can be traced as far north as the valley of Lake Rukwa, 

 which lies to the east of the Tanganyika depression, but 

 finally runs into and crosses it obliquely from east to west. 

 It is in the floor of the Nyassa depression, some way to the 



