NOTES. xv 



determinations of declination and inclination." .... This hitherto unregarded 

 document of Leibnitz does not manifest any particular theoretical views. 



( 196 ) p. 150. See my magnetic observations in "Asie Centrale," t. iii. p. 400. 



( 197 ) p. 150. Erman, Astron. und magn. Beobachtungen (Reise urn die 

 Erde, Abth. II. Bd. ii.), S. 532. 



( 19S ) p. 150. Hansteen, in Poggend. Ann. Bd. xxi. S. 371. 



( 199 ) p. 152. Sabine, Magn. and Meteor. Observ. at the Cape of Good Hope, 

 vol. i. p. Ix. 



( 20 ) p. 152. In judging of such near epochs, we must not forget, in reference 

 to this subject, how easily, with the instruments and methods then in use, an 

 rror of a degree might occur. 



C 201 ) p. 153. Kosmos, Bd. i. S. 430, Anm. 20 (English edition, Note 

 150). 



( ?02 ) p. 153. Euler, in the Mem. de 1'Acad. de Berlin, 1757, p. 176. 



( 203 ) p. 153. Barlow, in the Phil. Trans, for 1833, Pt. II. p. 671. Great 

 uncertainty prevails as to the older magnetic observations at St. Petersburg, in 

 the first half of the 18th century. They would make the declination to have 

 been always 3 15', or 3 30', for the whole period fr9m 1726 to 1772! (Han- 

 steen, Magnetismus der Erde, S. 7 and 143.) 



( 204 ) p. 154. Kosmos, Bd. i. S. 198210 (English edition, p. 179189) ; 

 and Dove, in Poggend. Ann. Bd. xix. S. 388. 



( 203 ) p. 154. The meritorious examinations of Lottin, Bravais, Lilliehb'b'k, 

 and Siljestrom, who observed the phenomena of auroras from September 19, 

 1838, to April 8, 1839, at Bossekop in Finnmarken (lat. 69 58'), and at 

 Jupvig (lat. 70 6'), have been published in Part IV. of the " Voyages en 

 Scandinavie, en Laponie, au Spitzberg, et aux Feroe, sur la corvette 'la Recherche ' 

 (aurores boreales)." To these observations are added important results obtained, 

 from 1837 to 1840, by English superintendents employed in the copper mines 

 at Kalfiord (lat. 69 56'), p. 401435. 



( 206 ) p. 154. Compare p. 437 444 of the above-named work, on the subject 

 of the " Segment obscur de 1'Aurore bore'ale." 



( 207 ) p. 154. Schweigger's Jahrbuch der Chimie und Physik, 1826, Bd. xvi. 

 S. 198, and Bd. xviii. S. 364. The dark segment and the incontestable shooting 

 upwards of black rays or streamers, in which the luminous process is nullified 

 (? by interference), may recall to us Quet's "Recherches sur rElectrico-chhnie 

 dans le Vide," and Ruhmkorff's fine experiments in which, in spaces containing 

 only very rarefied air, red light streamed from the positive, and violet from the 

 negative, metallic ball, but the intensely bright parallel strata of beams were 

 regularly separated by wholly dark strata: "La lumiere repandue entre les 



