CHANGE OF RIVER BED. 
401 
both in the great Arabian peninsula and in all the provinces 
of Spain which had the good fortune to fall under their sway. 
The Spaniards of the fifteenth and sixteenth centuries, who, in 
many points of true civilization and culture, were far inferior 
to the races they subdued, wantonly destroyed these noble 
monuments of social and political wisdom, or suffered them to 
perish, because they were too ignorant to appreciate their 
value, or too unskilful as practical engineers to be able to 
maintain them, and some of their most important territories 
were soon reduced to sterility and poverty in consequence. 
Another method of preventing or diminishing the evils of 
inundation by torrents and mountain rivers, analogous to that 
employed for the drainage of lakes, consists in the permanent 
or occasional diversion of their surplus waters, or of their entire 
currents, from their natural courses, by tunnels or open chan¬ 
nels cut through their banks. Nature, in many cases, resorts 
to a similar process. Most great rivers divide themselves into 
several arms in their lower course, and enter the sea by dif¬ 
ferent mouths. There are also cases where rivers send off lat¬ 
eral branches to convey a part of their waters into the channel 
of other streams.' 55 ' The most remarkable of these is the junc¬ 
tion between the Amazon and the Orinoco by the natural 
canal of the Cassiquiare and the Rio Negro. In India, the 
Cambodja and the Menam are connected by the Anam ; the 
Saluen and the Irawaddi by the Panlaun. There are similar 
examples, though on a much smaller scale, in Europe. The 
Tornea and the Calix rivers in Lapland communicate by the 
Tarando, and in Westphalia, the Else, an arm of the Haase, 
falls into the Weser. 
The change of bed in rivers by gradual erosion of their 
banks is familiar to all, but instances of the sudden abandon¬ 
ment of a primitive channel are by no means wanting. At a 
* Some geographical writers apply the term bifurcation exclusively to 
this intercommunication of rivers; others, with more etymological pro¬ 
priety, use it to express the division of great rivers into branches at the 
head of their deltas. A technical term is wanting to designate the phe¬ 
nomenon mentioned in the text. 
26 
