358 French National Institute. 



the operations, and reflections on some small corrections 

 which may be neglected in tlie most common circumstances. 



Terrestrial Magnetism. 



The observations of the magnetic needle which M. Hum- 

 boldt made with great care in the countries which he vi- 

 sited, have given M. Biot the idea and the means of making 

 researches in regard to the mathematical theory of terres- 

 \s\ii\ magnetism*. 



GEOGRAPHY. 



The results of the attempts hitherto made by the society 

 in England for making discoveries in the interior parts of 

 Africa are well known. Bv the accounts of the different 

 travels it caused to be undertaken, the difficulties and danger 

 which attend such expeditions are seen, and it mav therefore 

 be readilv conceived why that part of the world is so little 

 known. There was reason to think that the antients had a 

 more extensive and correct knowledge of it ; and in conse- 

 quence of this idea the Class of the Moral and Political Sci- 

 ences proposed, as the subject of a prize in the year 9, a 

 comparison of the geography of Ptolemy concerning the 

 interior of Africa with what has been since written on it by 

 modern authors and those of the middle ages. As no me- 

 moir was presented, and as the subject of the prize was 

 withdrawn, jNI, Buache thought it his duty to communi- 

 cate to the class a detail of the researches wh.ich he had be- 

 fore made on the same subject. In 1 787, before the forma- 

 tion of the English African Society, he had announced his 

 opinion in regard to it, in a memoir read in a public sitting 

 of the Academy of Sciences ; and this opinion, contrary to 

 all the ideas before received, was of such a nature as to ex- 

 cite the attention of geographers, had it been developed as" 

 it is in the new memoir which M. Buache presented to the 

 class this year. 



In this uienioir, whicli is entitled RescarcJws in regard to 

 the Interior of Libya of P/ulemi/, the author examines in 

 succession, and in the order in which thev are, all the de- 

 tails contained in the sixth and fourth books of Ptolemy ; 

 and according to the various information he has found, and 

 which he discusses bv presenting them under tlicir real 

 point of view, he endeavours to indicate nearly the position 

 of the diflcrent objects described by the antient geographer. 

 He presents this immense labour only as a iuere commen- 

 tary, destined to throw light on the knowledge which the 



* ?fe his p;>por on this siibject in the last and present Number. 



autients 



