429 
THE GEOLOGICAL HISTORY OF THE RIFT 
VALLEY 
By Prof. J. W. Gregory, D.Sc., F.R.S. 
[An Address to the Society, delivered at Nairobi, May 31, 1919.] 
When in May, 1893, I camped on the unoccupied site of 
Nairobi, I little thought that, twenty-six years later, I should 
find it transformed into the capital of a vigorous and flourishing 
colony, and that I should have the honour of addressing here 
a Natural History Society which has already taken a good 
place among the scientific societies that have added so greatly 
to the knowledge of the Empire and its resources. Still less 
did I imagine when, a few weeks later, I decided to suggest 
4 Rift Valley ’ as the technical term for the type of valley 
between Naivasha and Baringo, that the name would be 
generally adopted for the district and used in the 4 Rift Valley 
Hotel ’ and 4 Rift Valley Club.’ 
The problem which mainly attracted me to British East 
Africa in 1892 was the nature of the valley which crosses the 
country from Lake Rudolf to Lake Magadi, and which I followed, 
in 1898, from the Kedong to Lake Baringo. It had long been 
recognised that a valley of an unusual type extends from the 
Jordan and the Dead Sea through the Gulf of Akaba 
into the Red Sea. The exploration of East Africa led to the 
discovery of a series of long fiord-like lakes and valleys, with 
many features similar to those of the basins of the Red Sea and 
Dead Sea. The conclusion that the Jordan-Red Sea valley 
was continuous with that of the fiord-like lakes of equatorial 
Africa was adopted by Professor Suess, after the discovery 
of Lakes Rudolf and Stephanie by Count Teleki and his gifted 
companion von Hohnel. Suess suggested that the basins 
of the Red Sea and the long lakes of East Africa were all 
parts of an almost continuous trench which extends from 
Galilee to the Zambesi. 
