Nor, indeed, must it be forgotten that the search for new and more direct connexions with the routes of Oriental trade is one of the motives underlying the Crusades themselves, and leading to what may be called the 13th-century discovery of Asia.
The transport concerns land routes and sea routes, the latter being the more important.
The winds closely depend on the routes followed by both.
One of the ancient trade routes across the Sahara - that from Tripoli to Kuka in Bornu - strikes the lake at its northwest corner, but this has lost much of its former importance.
Each department controls and maintains the routes dpartementales, usually good macadamized roads connecting the chief places within its limits and extending in 1903 over 9700 m.
