On the Fhyficnl and Political Gcop'aphy of North Africa. 253 



"The elementary principles of bitumen are, hydrogen, carbon, fometimes azote, and pro- 

 bably fome oxygen, which, by its a£lion on the other principles, tends to form the concrete,; 

 bitumens, and alfo produces that portion of acid obtained by chemical operations. Thefe 

 fame principles, hydrogen and carbon, conflitute the vegetable oils and refins ; and the fame, 

 with fome azote, form the oils and greafe of animals. Now it is Icnown that very fmall 

 changes in the rcfpeftive proportions of thcfc ingredients, and in the circurnflanccs which 

 attend the combination of them, will caufe confiderable variations in the nature of the pro- 

 dufts; and in like manner, it appears very probable, that when the organized bodies in their ' 

 recent ftate, and in the full poffeifion of the above-mentioned principles, have been buried'in 

 a fituation where thefe principles have been long elaborated under certain favourable circuin- 

 ilances, and fubje<fled to the adion of mineral bodies ; I fay that it appears highly probable, 

 that a new combination, which we call bitumen, may be formed, which, although different 

 in fome refpc£ls from the vegetable and animal products, flill, however, retains many cha- 

 rafters of thofe fubftanccs from the principles of which it has been formed. 



Hammersmith, 

 April 26, lyg-]. 



III. 



Olfervattorts on the Phyfttal and Political Geography of North Africa. 



By James Rennml-, Efq. F. R. S. * 



J. O our view. North Africa appears to be compofed of three diftinft parts, or members. 

 The firft and fmalleft is a fertile region along the Mediterranean^ lying oppofite to Spain, 

 Franc», and Italy (commonly diflinguifhed by the name of Barbary) ; and which, coiild we . 

 fuppofe the weflern bafon of the Mediterranean to have once been dry land (bating a lake t 

 or recipient for the furrounding rivers), might be regarded as a part of Europe j as pofTefling. 

 much more of the European than the African charadcr. \ 



The fecond part is what may be deemed the body of North Africa, comprifed betweetr' 

 Cape Verd and the Red Sea, on the eaft and weft; and having the Great Defert (or ^ 

 Sahara) and its members, on the North ; the Ethiopia ocean and South Africa, on the op- - 

 pofite fide. The prominent feature of -this immenfe region Is a vaft belt of elevated land of 

 great breadth, often fwelling into lofty mountains, and running generally from weft to eaft, . 

 about the tenth degree of latitude. Its weftern extremity feems to be Cape Verd j the 

 mountains of Abyffinia, the eaftern. To the north, its ramifications are neither numerous 

 nor extenfive, if we except the elevated tradt which turns the Nile to the northward beyond 

 Abyffinia. Towards the fouth no particulars are known, fave that a multitude of rivers 

 fome of them very large, defcet.c' from that fide and join the Atlantic and Ethiopic feas, from 

 the Rio Grande on the weft to Cape Lopez on the eaft; proving inconteftably that by far 

 the greateft proportion of rain water falls on that fide during the periodical feafon of the 



» Copied by pcrmiflion from his " Geographical Tlluftrationsof Mr. Park's Journey,'' in the Proceedings of 

 the African Aflbciation, 1 798. On this fubjeft fee likewife our Account of Books in the prefent Number N. 



