'The Nile for these thirty years has but once so failed as to 

 occasion dearth; but never in that period so as to produce 

 famine in Egypt.' This refers apparently to the thirty years 

 previous to 1773, the low Nile being perhaps that of 1772. He 

 further speaks of three of these floods having been exceptionally 

 abundant, which would apply to those of 17-">7, 17 OS, and perhap- 

 1753. The exceptionally low floods of 1783 and 1784 are men- 

 tioned by Volney, who speaks of them as causing a serious famine. 



" For comparison with this earlier series of years, rainfall data 

 do not exist as for the nineteenth century, -till it can be said with 

 certainty that the curve is not one which shows any more similarity 

 to the alternating dry and wet groups of years, having a period of 

 about 35 years, than has been found in the later series. 



"We may conclude then with reference to the variation of the 

 Nile flood from year to year, that no trace appears of any such 

 definite periodicity as might be of assistance 



whole much the same as for the nineteenth century. 



"The long period from 1781 to 1799, when apparently all floods. 

 except two, were below the average, prevents any average length 

 of the oscillation between floods in excess or defect being estimated 

 satisfactorily. Essentially, then, the Abyssinian rainfall which is 

 represented by the Nile flood, fluctuates at short intervals, and 

 does not increase more or less regularly for a period of years, and 

 then decrease in a similar way. These fluctuations are short, and 

 if the number of years between the different crests of the curve 

 be taken (whether such crests rise above the average or not) the 

 length of time between such crests is :— 



2 years in 12 eases in the nineteenth century 



