Iii BOXES. 



( 14J ) p. 169. Arago, in t!ie Annales de Ohhnie, T. xxxii. p. 214 ; Brewstr f 

 1 realise on Magnetism, 1837, p. Ill i Baumgarlner, in the Zeitschrift fiii 

 i'Dys. und Mathem. EL ii. S. 419. 



( 148 ) p. 169. Humboldt, Examen critique de PHist. de la Geographic, 

 T. iii. p. 36 



( 14C ) p. 169. Asie cent. T. i. Introduction, p. xxxvii. xlii. The western 

 nations, the Greeks and the Romans, knew that magnetism could be imparted 

 permanently to iron (" sola hsec muteria ferri, vires a magnete lapide accipit 

 '.etinelque lonyo lempore" Plin. xxxiv. 14.) The gr,at discovery of the 

 earth's directive force wou'd, therefore, also Lave been made in the west, if 

 any one had accidenta^y observed a fragment of loadstone more long than 

 broad, or a magnetised bar of iron suspended bv a thread, or floating freely on 

 the surface of water on a wooden support. 



( 15 ) p. 170. Topographical surveys, made solely by compass, and without 

 any provision for corrections for changes of terrestrial magnetism, cannot fail 

 ultimately to produce great confusion in the boundary lines between different 

 properties, excepting in those parts of the earth where the magnetic declina- 

 tion is either invariable, or at least is subject only to exceedingly small secular 

 changes. Sir John Herschel says, "The while mass of "West India property 

 has been saved from the bottomless pit of endless litigation by the invariability 

 of the magnetic declination in Jamaica and the surrounding archipelago, during 

 the whole of the last century, all surveys of property there having been con- 

 ducted solely by the compass. Compare Robertson, in the Phil. Trans, for 

 1806, Part ii. p. 348, on the pe.maneney of the compass in Jamaica since 

 1660. In the mother country (England), the magnetic declination has altered 

 during the same period fully 1*. 



( 151 ) p. 171. I have shewn elsewhere that the documents of Columbus's 

 voyages which have come down to us, give, with much certainty, three 

 determinations of points in the Atlantic line of no declination for September 13, 

 1492, May 21, 1496, and August 16, 1498. The direction of this curve was 

 at that time from N.E. to S.W.; and it touched the continent of South 

 America, a little to the east of Cape Codera, instead of, as at present, in the 

 northern part of Brazil, (Examen critique de 1'histoire de la Geographic, T. iii. 

 pp. 4448). We learn from Gilbert's Physiologia nova de Maguete, Lib. iv. 

 cap. i. the remarkable fact that, iii tb. year 1600, as in the time of Columbus, 

 the magnetic needle had scarcely any declination in the \ icinity of the Azores. I 

 think that I have shewn satisfactorily, from documentary evidence (in my Exa- 

 inc'ii critique, T. iii. p. 54), that the famous line of demarcation by which Pope 



