402 
NILE CANALS—DIVERSION OF RIVERS. 
period of unknown antiquity, the Ard^che pierced a tunnel 
200 feet wide and 100 high, through a rock, and sent its whole 
current through it, deserting its former bed, which gradually 
filled up, though its course remained traceable. In the great 
inundation of 1827, the tunnel proved insufficient for the dis¬ 
charge of the water, and the river burst through the obstruc¬ 
tions which had now choked up its ancient channel, and re¬ 
sumed its original course.* 
It was probably such facts as these that suggested to 
ancient engineers the possibility of like artificial operations, 
and there are numerous instances of the execution of works for 
this purpose in very remote ages. The Bahr Jusef, the great 
stream which supplies the Fayoum with water from the Nile, 
has been supposed, by some writers, to be a natural channel; 
but both it and the Bahr el Wady are almost certainly arti¬ 
ficial canals constructed to water that basin, to regulate the 
level of Lake Moeris, and possibly, also, to diminish the dan¬ 
gers resulting from excessive inundations of the Nile, by serv¬ 
ing as waste-weirs to discharge a part of its surplus waters. 
Several of the seven ancient mouths of the Nile are believed 
to be artificial channels, and Herodotus even asserts that King 
Menes diverted the entire course of that river from the Libyan 
to the Arabian side of the valley. There are traces of an 
ancient river bed along the western mountains, which give 
some countenance to this statement. But it is much more 
probable that the works of Menes were designed rather to 
prevent a natural, than to produce an artificial, change in the 
channel of the river. 
Two of the most celebrated cascades in Europe, those of 
the Teverone at Tivoli and of the Yelino at Terni, owe, if not 
their existence, at least their position and character, to the 
diversion of their waters from their natural beds into new 
channels, in order to obviate the evils produced by their fre¬ 
quent floods. Remarkable works of the same sort have been 
executed in Switzerland, in very recent times. Until the year 
* Mabdigny, Memoire sur lea Inondations de VArdeche, p. 13 . 
