XXIV NOTES. 



p. 64 and 68; Contributions to Terrestrial Magnetism, No VII. in the Phil. 

 Trans, for 1846, Pt. III. p. 254. 



(*) p. 97. Sabine, in the Seventh Report of the Brit. Assoc. p. 77. 



( 97 ) p. 97. Sir James Ross, Voyage in the Southern and Antarctic Regions, 

 vol. i. p. 322. This great navigator crossed the line of greatest force twice 

 between Kerguelen and Van Diemen's Islands; first in 46 44' S. lat., 128 28' 

 E. long., where the force was 2'034, from whence it diminished to T824 at 

 Hobarton (vol. i. p. 103 and 104); and a year afterwards, from the 1st of 

 January to the 3rd of April, 1841, when we find, from the journals of the 

 Erebus, that from 77 47' to 51 16' South latitude, and 175 43' to 136 52' 

 East longitude from Greenwich, the intensity of the Earth's magnetic total 

 force was always above 2'00, and even reached 2'07. (Phil. Trans, for 1843, 

 Pt. II. p. 211 215.) Sabine's result for the one focus of the southern hemi- 

 sphere (lat. 64, long. 137 30' E.), which I have given in the text, is derived 

 from Sir James Ross's observations from the 19th to the 27th of March, 1841, 

 between 58 and 64 26' S. lat., and 128 40' and 148 20' E. long., " crossing 

 the southern isodynamic ellipse of 2'00 about midway between the extremities 

 of its principal axis." Contributions to Ter. Mag. in the Phil. Trans, for 1846, 

 Pt. III. p. 252. 



(") p. 97. Ross's Voyage, vol. ii. p. 224. According to the instructions 

 given for the voyage, the two southern foci of maximum force were conjectured 

 to be in 47 S. lat. 140 E. long., and in 60 S. lat. 235 E. long. 



(99) p 98. Phil. Trans, for 1850, Pt. I. p. 201 ; Admiralty Manual, 1849, 

 p. 16; Erman, Magnet. Beob. S. 437454. 



( 10 ) p. 99. On the map of the isodynamic lines in North America, in No. 

 VII. of Sabine's Contributions to Terrestrial Magnetism, by an accidental error, 

 14'88 is the number given instead of 14'21; but the latter, which is the true 

 number, is given in the text of the Memoir, p. 252. There is also 'a typo- 

 graphical error in the portion added to Note 158 in the English translation of 

 Kosmos (Vol. i. p. 414), 13'9 being printed instead of, as it ought to be, 14'21. 



( l01 ) p. 99. 15-60 is taken from No. VII. of Sabine's Contrib. p. 252. s 

 From the Table of the Observations of the Erebus (Phil. Trans, for 1843, 

 Pt. II. p. 169 and 172), we see that some of the observations, taken on the ice 

 in 77 47' S. lat., 172 40' W. long., even gave 2'124 in the arbitrary scale. 

 The value of 15'60 in absolute scale supposes the intensity of the force at 

 Hobarton to be 13*51 ; the latter value being to be regarded as provisional 

 (Mag. and Met. Observations at Hobarton, vol. i. p. Ixxv.), and having indeed 

 been a little augmented in vol. ii. p. xlvi., where it is given at 13' 5 6. In the 





