MAGNETIC INCLINATION. 103 



The most complete series of observations which we pos- 

 sess in reference to the position of the magnetic equator was 

 made by my old friend Duperrey during the years 1823- 

 1825. He crossed the equator six times during his voyages 

 of circumnavigation, and he was enabled to determine this 

 line by his own observations over a space of 220°.* Accord- 

 ing to Duperrey's chart of the magnetic equator, the two 

 nodes are situated in long. 5° 50 / E. in the Atlantic Ocean, 

 and in long. 177° 20 / E. in the Pacific, between the merid- 

 ians of the Fejee and Gilbert islands. While the magnet- 

 ic equator leaves the western coasts of the South American 

 continent, probably between Punta de la Aguja and Payta, 

 it is constantly drawing nearer in the west to the geograph- 

 ical equator, so that it is only at a distance of 2° from it, 

 in the meridian of the group of the Mendana Islands.! 

 About 10° farther west, in the meridian which passes 

 through the western part of the Paumotu Islands (Low 

 Archipelago), lying in 153° 50 / E. long., Captain Wilkes 

 found that the distance from the geographical equator in 

 1840 was still fully 2°.J The intersection of the nodes in 

 the Pacific is not as much as 180° from that of the Atlantic 

 nodes; that is to say, it does not occur in 174° 10' W. long., 

 but in the meridian of the Fejee Islands, situated in about 

 177° 20 / E. long. If, therefore, we pass from the west coast 



79° 3' 37" W. long., inclination 2°*15 south. Humboldt, Recueil 

 d'Observ. Astron. (Nivellement Barometrique et Geode'sique), vol. i., 

 p. 316, No. 242, 244-254:. For the basis of astronomical determina- 

 tions, obtained by altitudes of the stars and by the chronometer, see 

 the same work, vol. ii., p. 379-391. The result of my observations 

 of inclination in 1802, in 7° 2' S. lat., and 78° 48' W.long., accords 

 pretty closely by a singular coincidence, and notwithstanding the sec- 

 ular alteration, with the conjecture of Le Monnier, which was based 

 upon theoretical calculation. He says, " the magnetic equator must 

 be in 7° 45' north of Lima, or at most in 6° 30' S. lat., in 1776" {Lois 

 du Magnetisme comparees aux Observations, pt. ii., p. 59). 



* Saigey, Mem. sur V Equatetir Magnetique d'apres les Observ. du 

 Capitaine Duperrey, in the Annales Maritimes et Coloniales, Dec, 1833, 

 t. iv., p. 5. Here it is observed that the magnetic equator is not a 

 curve of equal intensity, but that the intensity varies in different parts 

 of this equator from 1 to 0*867. 



f This position of the magnetic equator was confirmed by Erman 

 for the year 1830. On his return from Kamtschatka to Europe, he 

 found the inclination almost null at 1° 30' S. lat., 132° 37' W. long. ; 

 in 1° 52' S. lat., 135° 10' TV. long.; in 1° 54' lat., in 133° 45' W. 

 long. ; in 2° V S. lat., 139° 8' W. long. (Erman, Magnet. Beob., 1841, 

 s. 536). 



t Wilkes, United States Exploring Expedition, vol. iv., p. 263. 



