TERRESTRIAL MAGNETISM. 63 



sagacity of the Chevalier Borda, not by successful experi- 

 ments made by himself personally, but by those suggested 

 by his sagacious anticipations, and carried into execution in 

 consequence of the influence which he perseveringly exercised 

 on travellers and voyagers preparing for distant expeditions. 

 His long-cherished conjectures were first confirmed by 

 Lamanon, the companion of La Pe rouse, in the years 

 1785 1787. These observations, although their results 

 had been made known so early as the summer of the last- 

 named year to the Secretary of the Academic des Sciences, 

 Condorcet, remained unnoticed and unpublished. The 

 credit of the first, although on this account incomplete, 

 recognition of the important law of the variation of the mag- 

 netic force with the magnetic latitude, belongs without 

 dispute to the ill-fated expedition of La Perouse,( 67 ) the 

 preparations for which were of the highest scientific merit ; 

 but the law itself, I venture to believe, first became a living 

 fact in science by the publication of my observations made 

 from 1798 to 1804 in the south of Prance, in Spain, the 

 Canaries, and the interior of tropical America north and 

 south of the equator, and in the Atlantic and Pacific Oceans. 

 The scientific voyages of Le Gentil, Peuille'e, and Lacaille, 

 the first attempt to construct an inclination map, by Wilke 

 in 1768, and the memorable voyages of circumnavigation of 

 Bougainville, Cook, and Vancouver, all deserve honorable 

 mention for the data they afforded in respect to the previ- 

 ously much neglected element of the inclination, so impor- 

 tant for the establishment of the theory of terrestrial 

 magnetism. The instruments employed were, indeed, of very 

 unequal merit, and the determinations (which, although 

 widely distributed over the earth's surface, were generally 



