ORIGINS OF SCIENCE IN THE ANCIENT WORLD 13 



lithic cultures that extend to a very remote period in the 

 past. 2 



The geological history of the Nile region 3 has been such 

 that we may determine the sequence of cultural remains in 

 quite a definite fashion. Their actual age is, of course, sub- 

 ject to the limitations of all geological estimates of time. 

 An exact time correlation with Europe is exceedingly dif- 

 ficult, if not impossible with our present data. Nevertheless, 

 these remains are of great importance, because the complete- 

 ness of the record is hardly duplicated in any other locality. 

 The Nile valley originated, shortly before the European 

 Glacial Age, in what is called a block or rift-fault. As shown 

 by Figs. 2 and 3, a narrow section or fault-block (a a') 

 of the Eocene limestone, extending from the former coastline 

 near Cairo as far south as Coptos (Fig. 1), settled eight 

 hundred or more feet below the general surface of the plateau. 

 Lesser faults extended the valley southward a total distance 

 of almost four hundred and fifty miles to Gebelen. The 

 northern end of this rift, as shown by marine fossils, was for 

 a time occupied by a fiord of the sea while to the south a 

 fresh-water lake or chain of lakes existed for thousands of 

 years. Later the fiord also became converted into a lake 

 (Fig. 2). Eventually, this series of waterways became the 

 River Nile, which in its early history carried a greater 

 volume of water than at the present time. 



Existence of the lake or lakes is evidenced by the extensive 

 beds of lacustrine deposits which still appear along the val- 

 ley walls (Fig. 3). The heavy rainfall of earlier times swept 

 quantities of sand and gravel from the plateau. Many feet 

 of this material were deposited in the lake upon the top of 

 the fault-block (Fig. 2). After the river was established, its 

 erosion cut the lake-beds almost to their bottom before the 



2 Breasted, J. H., "The Origins of Civilization," Sci. Monthly, Oct., 1919, 

 pp. 304-8. 



3 Blanckenhorn, M., "Geschichte des Nil-Stroms," Zeitsch. der Gesell. fur 

 Erdkunde, 1902. 



