"The study deals ... with the records of the rise [of the Nile] during the twelve and a half centuries from 641 to 1890 A.D. ... The chronicles of ......
"The study deals ... with the records of the rise [of the Nile] during the twelve and a half centuries from 641 to 1890 A.D. ... The chronicles of ... Ibn-Taghrî Birdî ... are the principal source of the statistics of the Nile for 641-1470 A.D."