The latest theory which has been employed•to count for the aurora borealis is that of our-ingenious-, countrythan Mr Dalton, who considers it as a mag netic phenomenon, whose beams are governed by the magnetism of the earth. He supposes that theses beams are cylindrical portions of a magnetic fluid, which are actually parallel to the dipping needle, and therefore appear tp converge to the magnetic pole and that the light is produced by the transmission of electricity, which disturbs their magnetic properties. Mr Dalton observes, that the luminous arches are al ways perpendicular to the magnetic meridian ; and that, from the permanency of their form, they afford an opportunity of determining the height of the teors. From an observation on a base of 22 miles, he found its altitude to be about 150 miles. See-. Dalton's Meteorological Observations and 1793, p. 54. 153.
The Abbe Bertholon ascribes the aurora borealis. to a ...phosphorico-electric light. A full account of this theory has been given by its author in the Encyc.. Method. art. AURORE.
Much interesting information respecting the aurora borealis, will be found in the following works : Muschenb. Instit. Phys. e. 41. Tract. Phys. ct Hist. de l' Aur. Bor. par M. de Mairan,. Paris, 1754, 9to. Beccaria Dell. Electricismo Arti f. et Nat. • Smith's P.
221 mith's Optics, p. 69. D'Alembert's Opus
cules Mathematiques, vol. vi. p. 334. Phil. Trans. 1716, p. 406 ; 1717, p. 584, 586 ; 1719, p. 1099,, 1101, 1104, 1107 ; 1720, p. 21 ; 1721, p. 180, 186; 1723, p. 300 ; 1724, p. 175 ; 1726, p. 128, 132, 150 ; 1727, p. 215, 253, 255, 301 ; 1728, p. 453 ; 1729, p. 137 ; 1730, p. 279; 1731, p. 53, 55 ; 1734, p. 291 ; 1756, p. 241 ; 1740, p. 368 ; 1741, p. 744, 859, 840, 843 ; 1750, p. 319, 345,.346, 499 ; 1751, p. 39, 126 ; 1762, p. 47•, 479 ; 1764, p. 326, 332 ; 1767, p. 108 ; 1769, p. 86, 367 ; I 770,.p. 532 ;.
• 1771., p. 128 ; 1781, p. 228 ; 1790, p. 101.
) Mixed'. 13erolincns. 1710, vol. i. Comment.
Petrcp. tom. i. p. 351 ; iv. p. 121. Acta Pctropol. 1780, vol. iv. p. 1. Mem. Arad. Par. 1717, p. 363, 4.23 ; 1731; 1751. 411cm. Acad. Berl. 17.17, p.117. Selnved. Abbandlungen, 1752, p. 1n9; 1753, p. 85 ; 1761•, p. 200, 251. Bergman Opusc. vol. v. p. 272. Americ. 'Trans. vol. i. p. 101.. Mem. de Mathemat. et Phys. tom. viii. p. 180. llnzicr, vol. xiii. p. 409 ; xv. p.128 ; vol. xxxiii. p. 153. Franklin's Works, vol. ii. Weidler De Aurora Borealc. Nocetus De fridc el Aurora Bo•cale cum Notis Boscovich, Rome, 1747. Soc. Bal. vol. vii. p. 153. Gilbert's Journal, vol. xv. p. 206. But particularly, Dr T. Young's Nat. Phil. vol. i. p. 687, 716 ; and vol. ii. p. 488. (T) (n)