NOTES. XXV 



Admiralty Manual, p. 17, I find the force at the stronger southern focus altered 

 accordingly to 15'8. 



( 102 ) p. 99. Sabine, in the English translation of Kosmos, Vol. i. p. 414. 



( 103 ) p. 100. See the interesting representation entitled: Map of the World, 

 divided into hemispheres by a plane coinciding with the meridians of 100 and 

 280 E. of Greenwich, exhibiting the unequal distribution of the magnetic in- 

 tensity in the two hemispheres, Plate V., British Association Reports for 1837, 

 p. 72 74. Erman found the force almost always below 0'76 (very weak 

 therefore) between 24 25' and 13 18' S. lat., and between 34 52' and 32 42' 

 W. long, from Greenwich. 



( 104 ) p. 100. Kosmos. Bd. i. S. 193 and 435. Anm. 30 (English edition, 

 p. 175 and Note 160). 



( 105 ) p. 100. Ross's Voyage in the Southern Seas, vol. i. p. 22 and 27. See 

 also Kosmos, Bd. iv. S. 84, Anm. 88 (English Edition p. 92, and Note 88). 



( 106 ) p. 100. See Table of Sulivan's and Dunlop's Observations in Phil. 

 Trans. 1840, Pt. I. p. 143. Their minimum, however, was not lower than 

 8-00. 



( 107 ) p. 101. We obtain 1:2'44 by comparing, in the absolute scale, 6'4 at 

 St. Helena with 15- 60 at the stronger southern focus; or 1 : 2'47 by comparison 

 of St. Helena with the southern maximum augmented to 15'8 (Admiralty 

 Manual, p. 17); 1 : 2'91 by comparing, in the relative scale, Erman's observa- 

 tion in the Atlantic (0706) with the southern focus (2'06); and even 1 : 2 - 95, 

 if we compare, in the absolute scale, the weakest force observed by Erman (5*35) 

 with the highest result for the southern focus (15'8). A mean number would 

 be 1 : 2'69. Compare for the intensity of the force at St. Helena (6'4 in abso- 

 lute, or 0'845 in relative scale) the earliest observations by Fitz Roy (0'836), 

 Phil. Trans, for 1847, Pt. I. p. 52, and British Association Report for 1837, 

 p. 56. 



( 108 ) p. 101. Compare English translation of Kosmos, Vol. i. Editor's Note 

 158 p. liii. Iviii., and No. VII. of Contributions to Terrest. Magnetism, p. 256. 



( loe ) p. 102. What can have led to the erroneous result obtained in the 

 coal mines of Flenu, viz., that at a depth of 83 French feet the horizontal in- 

 tensity increased O'OOl? Journal de 1'Institut, 1845, Avril, p. 146. In an 

 English coal mine, at a depth of a thousand feet, Kenwood found no increase of 

 force. (Brewster, Treatise on Magnetism, p. 275.) 



() p. 103.-Kosmos, Bd. i. S. 418, Bd. iv. S. 36 (English edition, Vol. i. 

 Note 124; Vol. iv. p. 36). 



( m ) p. 103. In my observations, a diminution of magnetic force with in- 



