NO. 10 SOLAR RADIATION AND WEATHER STUDIES ABBOT 6^] 



Table 12. — 23-YcaY Cycles in North Atlantic Cod Fisheries, 1812-1^27. 

 Values Given in Millions of Pounds 



" These two columns are 15 times their originals, as stated in the text. 



21. A Test of the 23-YEAR Hypothesis in the Flow of the 

 River Nile 



C. F. Talman, librarian of the United States Weather Bureau, was 

 good enough to draw to my attention to, and lend me, Prince Omar 

 Toussoun's " Memoire sur I'histoire du Nil," Cairo, 1925. Volume 2 

 of this pubhcation gives an extended table of annual high- and low- 

 water stages of the Nile beginning with A. D. 622. A short com- 

 parison indicated to me that the low-water stage was preferable for 

 my purpose. It showed much smaller apparently accidental fluctua- 

 tions than the high-water stage. The earliest low-water records seemed 

 probably less accurate, for they too showed wide irregular fluctuations. 

 After about 1430 until 1839, the low-water stage records were unfor- 

 tunately fragmentary, so that these four centuries had to be omitted. 

 After 1884 the work of British engineers so greatly modified the 

 natural flow of the river that the records cease to be useful for my 

 purpose. Because of these several considerations, I limited my re- 

 search to a study of low stages of the Nile for 690 years from 735 to 

 1424, and 46 years from 1839 to 1884. 



Figure 28 gives a number of individual 23-year cycles in the level 

 of the Nile at low water. It will be seen that the early cycles of the 

 eighth century diiier from the two cycles of the nineteenth century 

 in phase, indicating either that there is a slight deviation from exactly 



