UOTES, II 







C 144 ) p. 108. I have described, in the Journal de Physique of Lametherie 

 (1804, T. lix. p. 449), the application of the magnetic Inclination to deter- 

 minations of latitude along a coast running north and south, and, like that of 

 Chili and Peru, constantly enveloped by mist (garna) during part of the 

 year. In the particular locality alluded to, this application is the more 

 practically important, by reason of the strong southerly current, ex- 

 tending to Cape Farina, which causes great loss of time to navigators, who 

 have inadvertently passed to the north of the latitude of the port to whicli 

 they are bound. In the Pacific, from Callao to Truxillo, I have found, 

 for a difference of latitude of 3 5?', a change of Inclination of ^8.l ; an4 

 from Callao to Guayaquil, for a change of latitude of 9 50', a change o 

 Inclination of 20.7 (Relation historique, T. iii. p. 622). At Guarmey (la* 

 10 4' S.), Huaura Gat. 11 3' S.), and Chancay (lat. 11 32').. the Inclination* 

 were respectively : 6.l, 8.l, and 9.3. The determination of the ship's 

 place by means of the magnetic Inclination, when her course nearly 

 intersects the isoclinal lines at right angles, is distinguished from all other 

 methods by its independence of the time of the day, and by its not, therefore, 

 requiring the sight of any of the heavenly bodies. I have very recently 

 learned that, as early as the end of the sixteenth century, scarcely twenty years 

 after Robert Norman invented an Inclinatorium, William Gilbert, in his 

 great work " De Magnete," proposed the determination of latitudes by means 

 of the Inclination of the magnetic needle. In his Physiologia nova de Magnete, 

 Lib. v. cap. 8, p. 200, he extols the advantages of this method in thick weather, 

 " acre caliginoso." Edward Wright, in the preface which he has added to the 

 work of his illustrious master, says that this proposal is " worth much gold." 

 As he shared Gilbert's error in believing the isoclinal lines ( j be parallel to 

 the geographical equator, he did not perceive that the method is only appli- 

 cable in particular localities. 



( 145 ) p. 1GS. Gauss and Weber, Resultate des inagnctischen Vereins, 

 im J. 1838, 31, S. 46. 



( 146 ) p. 168. According to Faraday (London and Edinburgh Philosophical 

 Magazine, 1836, Vol. viii. p. 1?8), pure cobalt is not magnetic. I am aware 

 that other distinguished chemists (Hcinrich Rose and Wohler) do not consider 

 this a settled point ; but it appeal's to me that if one of two carefully-purified 

 masses of cobalt, both supposed to be free from any alloy of nickel, is found to be 

 non-magnetic, it is probable that the magnetism shewn in the other mass is due 

 to a want of purity ; and I am inclined, therefore, to believe Faraday's view 

 to be the more correct. 



