ON THE PERIODICITY OF THE AURORA BOREAUS. 



243 



gravity is farthest removed from the surface, either inwards or outwards. Peters ' 

 refutes the proposition, by introducing Neptune into the account in calculating the 

 position of the centre of gravity. 



Dove has found traces of a decimal period in the fluctuations of the mean annual 

 temperature of the earth. 2 Kluge deduces from his own investigations the conclu- 

 sion that a period of about 11.11 years governs the frequency of volcanic eruptions 

 and earthquakes, but in such a way that the minima of these outbreaks occur in 

 years most distinguished by an abundance of solar spots and frequent magnetic 

 disturbances. 3 



l Astronomische Nachrichten. 2 London Athenaeum for 1866, p. 236. 



3 Vierteljahrsschrift der Naturforsch. Gesellsch. in Zurich, IX 266 and X. 252. 



SECOND GENERAL CATALOGUE OF AURORAS. 



B. C. 



434. 

 176. 

 159. 



87. 



84. 



A. D. 



551? 



590. 



610. 



793. 



905. 



978. 



992. 

 1097. 

 1117. 

 1122. 



Oct. 20. 



April 12. 



Oct. 26. 



Feb. 17. 



Matthew, Penseyv 



Short. 1 

 Short. 

 Short. 

 Short. 

 Short. 



Westminster. 

 Short. 8 

 China. 

 Short. 



Short. 



Zurich ? Vogel, Wolf. 4 



Maier, Frobes ? 5 



Einsiedeln. Kuhn. 8 



Short. 



'A General Chronological History of the Air, Weather, &c. 

 H. 178. 



3 Annals of Philosophy, IX. 250. 



5 The Aurora was seen on three nights. 

 Vierteljahrsschrift der Xaturfoisch. Gesellsch. in Zurich, II. 

 83 and 401. 



5 Robert Monachi Historia Hierosol. Lib. V. Comm. Acad. 

 Scient. Petrop, 1726, I. 366. 



6 Vierteljahrsschrift der Naturforsch. Gesellsch. in Zurich, XI. 

 112. If this date is in old style, the Aurora may be the same as 

 that of Feb. 22. 



1128. Nov. 25. Bohemia? Stmadt. 1 



1130. Jan. 13. Bohemia? Strnadt. 



" Sept. 2. Bohemia? Strnadt. 



" Oct. 8. Bohemia? Strnadt. 



1132. Jan. 21. Bohemia? Strnadt. 



1138. May 18. Bohemia? Strnadt. 

 " Oct. 13. Bohemia? Strnadt. 

 " " 14. Bohemia? Strnadt. 



1139. March 14, Bohemia? Strnadt. 

 1177. Nov. Short. 



" Dec. Short. 



1189. Short. 



1193. England? 



1194. England. 

 1347. Short. 



1460. Jan. 13. Bohemia? Strnadt. 



1560. Dec. 28. Mark, Brandenburg. Beckmann. 



1562. March 23. Rauner." 



1564. Short. 



" Feb. 15. Scotland* 



" " 18. Scotland. 



1 Chronolog. Verzeichn. d. Naturgebenhen in Bohmen. 



s Neubrigensis Chronica Rerum Anglicarum, IV. 36. 



'Wochenschriftfiir Astronomie, Meteorologie, &c. NeueFolge, 

 VII. 230. 



4 Wolf quotes Chasma Coeli, Erffurdt. 



'Burton, in his History of Scotland, refers to Knox's History. 

 II. 417. 



