Mr. Horneman describes the black Harutsch to consist of matter, that, in his idea, was volcanic, or had undergone the action of fire: and its conformation appears very singular indeed. There exists in Pliny, an evident proof that it was known to the Romans; for they had crossed it, in their expeditions to Fezzan, and towards the Niger, &c.; and had even explored and remarked the shortest route across the same mountains. Pliny says, that “from _Cydamus_ (i. e. _Gadamis_, which, by the bye, he says lies opposite to _Sabrata_, on the sea coast) there extends a mountain a long way to the east, called by the Romans, MONS ATER; and which appears as if it were burnt or scorched by the rays of the sun.” (Lib. v. c. 5.) And he adds, that beyond those mountains, are deserts, and the towns of the Garamantes, which were conquered by the Romans under Balbus. In this description, we clearly recognise the SOUDA, or BLACK DESERT, to the north of Fezzan; and which Mr. Horneman _saw_, both there, and to the east, of the same country; and also _learnt_, that it _continued_ far westward, beyond the line of the road from Fezzan to Mesurata: in other words, towards Gadamis. Sockna, which is a town of some consideration, lies midway between this road and Gadamis: and it is known that the Desert of _Souda_ passes to the south of it. So that there is little doubt but that Pliny is right, in extending the _Mons Ater_ westward to _Cydamus_, (_i. e._ Gadamis) and to a long extent eastward of it. VII. _Fezzan._ It has been said, that there is no material difference between the position of the capital of this country (Mourzouk), as given by Mr. Horneman, and the former assumed position in the maps, drawn for the African Association, in 1790 and 1798; considered in the view of general geography. It is for this reason, that I have not altered it in the general Map, but have accommodated the positions eastward to it; instead of altering the entire Map. But in the Map of Mr. Horneman’s Route, all the positions affected by his observations, are given according to those observations. Neither do the boundaries and extent, as given by Mr. Horneman, differ materially from those given by Mr. Beaufoy; which is remarkable, considering under what disadvantage he collected his materials, compared with the mode of collecting them on the spot. But in arranging the boundaries, a distinction is to be made between the _proper_ country of Fezzan, and its _dependencies_.