i may be geographically represented by plotting 



"These data should show some signs of an alternating series of 

 high and low floods, that is, of a periodicity in the floods if such 



"On Plate xliii the Nile floods for 78 years, 1825 - 1903, are 

 shown as well as an earlier series of 64 years from 1737 to 1800. 



ber rainfall on the Abyssinian table land, the rains and the 

 meteorological conditions which determine them must be subject 



flood diagrams. 



"Essentially the .succession of Nile floods for the last SO years 



1800, though the range of oscillation is not so large, if the obser- 

 vations can be relied on. 



"The long series of years following 1738 in which the Nile flood 

 was almost invariably good is corroborated by Bruce, who writes: — 



