The white Harutsch, crossed by Mr. Horneman, is in this vicinity, and extends southward, from the line of his route across it, from Augila to Mourzouk: so that it is not improbable that the “hilly desert” just mentioned, is a continuation of the white Harutsch. What renders it more probable is, that Mr. Horneman was told, that certain _black_ mountains, which he suspected to be a part of the black Harutsch, are crossed in the way from Fezzan to Bournu. And it has been shewn, that the black Harutsch adjoins to the white Harutsch on the east; and this arrangement may continue, southward: in which direction Mr. Horneman was informed the black Harutsch stretched, beyond the line of his route. This gentleman describes the hilly part of the white Harutsch to consist of “_loose friable limestone_, in which the petrifactions are _imbedded so loosely_, that they may be taken out with ease.” No rocks therefore are more likely to contain natural caves, or are more easily excavated, when wanted. This tract, therefore, seems, as well from description, as position, to be that inhabited by the Rock Tibbo. A circumstance in Herodotus (Melpom. 183), leads one to conclude, that these are the _Ethiopian Troglodytæ, hunted by the Garamantes_. The Garamantes, I trust, I have made to appear, are the Fezzaners; and here are a tribe of Troglodytæ, on their very borders. They are said, in the same place, to be very swift of foot. Mr. Horneman says, that the walk of the Tibbos is light and swift: as if remarkably so: but then he speaks of the Tibbo, collectively; and not of any particular tribe. But, on the other hand, it appears that he saw more of the Rock Tibbo, than any other: for he says, “they go in multitudes to Fezzan;” and it may be that his opinion of the nation at large was, in a great measure, formed by what he saw of this tribe.[68] A strange particular is related of the Troglodytæ, by Herodotus. He says, that their language bears some resemblance to the screaming of bats.[69] Melpom. 183. 2. _The Febabo._ This tribe is found at 10 journies SSW from Augila; between which territories, on the side of Augila, is a desert of 6 journies, void of water. And notwithstanding this circumstance, and the distance from the sea coast of Bengasi (20 days, at least), they are annually exposed to the depredations of the people of Bengasi, who, joined with those of Augila, go to _steal_ men and dates. See above, on Gegabib, page 148. 3. _Burgu, or Birgu._ (This must not be mistaken for Bergoo, a state situated in the quarter of Darfoor.) It appears in D’Anville and Delisle, as well as in Leo, under the name of _Berdoa_; but the name is too often repeated by Mr. Horneman to be a mistake of his. This tribe resides to the south of Febabo, at the distance of _some_ days; and at eighteen, eastward from Tibesty. Hence the Burgu tribe may be placed S a little W from Augila, and about the parallel of the south of Fezzan.