104 COSMOS. 



of Africa, through South America westward, we shall find 

 in this direction that the distance of the nodes from one an- 

 other is about 8^ too great, which is a proof that the curve 

 of which we are here speaking is not one of the great circles. 



According to the admirable and comprehensive determina- 

 tions which were made by Captain Elliot from 1846 to 1849, 

 between the meridians of Batavia and Ceylon, and which 

 coincide in a remarkable manner with those of Jules de 

 Blosseville (see page 65), it would appear that the magnetic 

 equator passes through .the northern point of Borneo, and 

 almost due west into the northern point of Ceylon, in 9 45' 

 N. lat. The curve of minimum total intensity runs almost 

 parallel to this part of the magnetic equator,* which enters 

 the western part of the continent of Africa, south of the Cape 

 of Gardafui. This important re-entering point of the curve 

 has been determined with great accuracy by Rochet d'Heri- 

 court on his second Abyssinian expedition, from 1842 to 

 1845, and by the interesting discussion to which his magnet- 

 ic observations gave rise.| This point lies south of Gau- 

 bade, between Angolola and Angobar, the capital of the 

 kingdom of Schoa, in 10 1 / N. lat., and in 41 13' E. long. 

 The course of the magnetic equator in the interior of Africa, 

 from Angobar to the Gulf of Biafra, is as thoroughly unex- 

 plored as that in the interior of South America, east of the 

 chain of the Andes, and south of the geographical equator. 

 Both these continental districts are nearly of equal extent, 

 measured from east to west, each extending over a space of 

 about 80 of longitude, so that we are still entirely ignorant 

 of the magnetic condition of nearly one quarter of the earth's 

 circumference. My own observations of inclination and in- 

 tensity for the whole of the interior of South America, from 

 Cumana to the Rio Negro, as well as from Cartagena de In- 

 dias to Quito, refer only to the tropical zone north of the 

 geographical equator, while those which I made in the south- 

 ern hemisphere, from Quito as far as Lima, were limited to 

 the district lying near the western coast. 



The translation of the African node toward the west from 

 1825 to 1837, which we have already indicated, has been 

 confirmed on the eastern coasts of Africa by a comparison 

 of the inclination-observations made by Panton, in the year 

 1776, with those of Rochet d'He'ricourt. The latter ob- 

 server found the magnetic equator much nearer the Straits 



* Elliot, in the Phil. Transact, for 1851, pt. i., p. 287-331. 

 t Duperrey, in the Comptes rendus, t. xxii., 1846, p. 8*4-806. 



