Their territory is said to be fertile, but they bear the character of robbers. A caravan of Fezzanners, from Begarmé and Bournu, about the time of Mr. Horneman’s visit, was plundered by them. The Sultan of Fezzan sent a force to punish them; the smallness of which, seems to prove that the Burgu are either not numerous, or are very much dispersed. (See above, page 107). The route of the Sultan’s army helps to fix the positions both of Burgu, and of the Rock Tibbo.[70] Mr. Beaufoy relates (ch. iv. 1790,) that on another occasion, the Tibbo of Tibesty plundered a caravan of Fezzan, which robbery was also punished: but on the last occasion, the Tibestians (who are the Rock Tibbo), aided the Sultan. It appears by the geography, that the caravans from the SE are much exposed to the Burgu and Tibesty, in their route to Fezzan.[71] 4. _Arna._ This tribe is said to live five or six journies to the eastward of the Burgu; and must therefore border on the sandy Desert of the _Lebetæ_. Mr. Horneman appears to have known them only by name. 5. _Bilma._ This is the principal tribe of the Tibbo. They occupy the middle space, between Fezzan and Bournu, adjacent to the great Desert of Bilma. Their capital of _Dyrke_ is said to be one journey from Bilma; which may be the Balmala of Edrisi. They carry on a commerce between Bournu and Fezzan. (See above, p. 106.) The _Billa_ of Ptolemy may possibly be meant for Bilma; but is too far to the eastward. Mr. Beaufoy states the distance to be 45 days of the salt caravans from Agadez to the lake of Dumboo; which is situated within the Desert of Bilma. These, at 13 G. miles per day,[72] give a total of 585 miles. The interval on the construction is about 60 less. Either then, Agadez is more to the west, or Dumboo more to the east. Two circumstances render it probable that Agadez should be more to the west: Mr. Magrah was told that it lay S 30° W from Fezzan: and that it lay N from Kashna. That part of the General Map of 1798, has not been altered. 6. _Nomadic Tibbo._ These are the most southerly of the tribes; and are seated in the _Bahr-el-Gazel_, which, Mr. Horneman was told, was a long and fruitful valley, 7 journies north of Begarmé. Of the _Bahr_ (or _Wad_)-el-Gazel, I have already spoken, in page 168. The distance of 7 journies N of Begarmé would place the Nomadic Tibbo within the empire of Bournu. Perhaps, in Bournu, as in Persia, both ancient and modern, Nomadic tribes find plenty of room:[73] but whether so far southward, may be a doubt, for a river of the name of Wad-el-Gazel, is said to flow even into the Desert of Bilma. Antelopes are found in the neighbourhood of Dumboo; and there may be a river denominated from them, in that quarter, as well as in that of Begarmé. _Of the_ TUARICK.[74]