DELTA OF THE NILE. 359 



nishes an example of a country becoming drier and 

 drier ; it is entirely formed of the depositions from 

 the Nile." According to him, the Canopus, or 

 western branch, is the only natural one ; the others 

 appear to have been dug by man to facilitate 

 drainage. 



Plutarch (" Isis and Osiris ") says that in ancient 

 times the valley of the Nile was covered by the 

 sea, as is proved by the shells met with in the 

 neierhbourino: desert, and the saltness of the wells 

 dug there. Arabian authors of the middle ages 

 express the same opinion. 



It is very curious to remark, that ancient ob- 

 servers had already sufficiently studied this ques- 

 tion to recognise the slow but continuous elevation 

 of the bed of the river, and the deposition of its 

 suspended matter in the sea, so as to constitute a 

 delta. From this elevation of the bed it results, 

 that near their mouths, in very flat regions, the 

 rivers often flow at a level higher than that of the 

 surrounding plain, so that at each flood the waters 

 spread over the surrounding country, and cannot 

 re-enter their bed but from lakes. 



Often, as if uncertain of their course, the waters 

 divide into several branches to reunite farther on. 

 The lightest inequality in the soil forms an insur- 

 mo atable obstacle to their progress. The waters 



