Reviews — Dr. J. W. Gregory's Great Rift Valley. 325 



proportion of the book, there is abundance of matter for the political 

 economist, for the geographer, anthropologist, and the geologist. 

 Botany and zoology have also gained by the varied novelties that 

 Dr. Gregory has brought back. Some interesting cases of mimicry 

 were observed by the author, one of which (drawn by Mrs. Gregory), 

 representing a cluster of insects (Flata nigrocincta) grouped so as to 

 resemble a flower-spike, forms a charming frontispiece to this 

 volume. 



Eeverting to the title of the book, one is led naturally to seek for 

 explanation of the term " the Great Rift Valley." We find an 

 answer (on p. 3) where the author refers to Mr. F. Galton's state- 

 ment, when discussing Mr. Thomson's paper on his journey through 

 Masailand, namely, that the great depression or trough in which 

 Naivasha and Baringo lie, is part of one " which begins with the 

 Dead Sea, extends down the Red Sea, and ends at Tanganyika." 



A study of the Lake-system of East Africa enables us to see 

 clearly that the lakes are developed according to two absolutely 

 different types. " Some are rounded in shape, as the Nyanza; others 

 are long and narrow, as Tanganyika and the Nyasa." An examina- 

 tion of the lakes themselves shows "that the round lakes have low 

 shelving shores, and that the long ones lie like fiords, between 

 high, precipitous cliffs." 



" The map shows us that these two types of lakes are not 

 distributed haphazard, but on a definite plan. The long fiord-like 

 lakes occur on two lines, which pass one on either side of the 

 Nyanza and meet at Basso Narok (Lake Rudolf). Thence the line 

 continues northward as a long strip of low land, dotted with lakes 

 and old lake-basins, and sinking in places below the level of the 

 sea. This extends to the southern end of the Red Sea, which repeats 

 the structure of these fiord-like lakes on a larger scale : it is long 

 and narrow, and, excluding some strips of coast deposits, has high, 

 precipitous shores. From its northern end the Gulf of Akaba leads 

 to another valley with similar characteristics, and from this the 

 Dead Sea and Jordan valley continue the same type of geographical 

 structure, till it ends on the plains of northern Syria. 



" From the Lebanons, therefore, almost to the Cape there runs 

 a valley, unique both on account of the persistence with which it 

 maintains its trough-like form, throughout the whole of its 

 course of 4,000 miles, and also on account of the fact that scattered 

 along its floor is a series of over thirty lakes, of which only one has 

 an outlet to the sea. 



" This valley and its lake-chain are so different from anything else 

 on the surface of the earth, that it is natural to ask whether different 

 portions of it have been formed independently, or whether it was 

 all formed at the same time and by the same process. The final 

 answer to this question must be given by geology, but history 

 affords us some useful hints. All along the line the natives have 

 traditions of great changes in the structure of the country. The 

 Arabs tell us that the Red Sea is simply water that did not dry up 

 after Noah's deluge. The Somali say that when their ancestors 



