Gilbert’s ‘Journal,’ vol. xv. p. 206; and (particularly) Dr. T. Young’s ‘Nat. Phil.’ vol. i. pp. 687, 716, and vol. ii. p. 488. Wiedeburg, ‘Ueber die Nordlichter.’ Jena, 1771. Hüpsch, ‘Untersuchung des Nordlichts.’ Cologne, 1778. Van Swinden, ‘Recueil de Mémoires.’ Hague, 1784. Wilke, ‘Von den neuesten Erklärungen des Nordlichts,’ Schwed. Mus. Wismar, 1783. Dalton’s ‘Meteor. Observ.’ 1793, pp. 54, 153. Loomis, ‘Sill. Journal,’ 2nd series, xxxii. p. 324; xxxiv. p. 34. The same, 3rd series, v. p. 245; B. V. Marsh, 3rd series, xxxi. p. 311. Oettingen and Vogel, Pogg. Ann. cxlvi. pp. 284, 569. Galle and Sirks, _ibid._ cxlvi. p. 133; cxlix. p. 112. Silbermann, ‘Comptes Rendus,’ lxviii. pp. 1049, 1120, 1140, 1164. Prof. Fritz, “Geog. Distrib.,” Petermann’s Mitth., Oct. 1874. Zehfuss, ‘Physikalische Theorie.’ Adelman, Frankfort. ‘Nature,’ iii. pp. 6, 7, 28, 104, 126, 346, 348, 510; iv. pp. 209, 213, 345, 497, 505; x. 211 (Ångström). ‘Edinburgh Astronomical Observations,’ vol. xiv. 1870-1877. ‘English Mechanic,’ No. 461 (January 23, 1874), pp. 445-447; and No. 462, pp. 475, 476. APPENDIX B. EXTRACTS FROM THE MANUAL AND INSTRUCTIONS FOR THE (ENGLISH) ARCTIC EXPEDITION, 1875. _Note on Auroral Observations. By Prof. STOKES, Sec. R.S._ The frequency of the Aurora in Arctic regions affords peculiar facilities for the study of the general features of the phenomenon, as in case the observer thinks he has perceived any law he will probably soon, and repeatedly, have opportunities of confronting it with observation. The following points are worthy of attention:— _Streamers._—It is well known that, at least as a rule, the streamers are parallel to the dipping-needle, as is inferred from the observation that they form arcs of great circles passing through the magnetic zenith. It has been stated, however, that they have sometimes been seen curved. Should any thing of this kind be noticed, the observer ought to note the circumstances most carefully. He should notice particularly whether it is one and the same streamer that is curved, or whether the curvature is apparent only, and arises from the circumstance that a number of short, straight streamers start from bases so arranged that the luminosity as a whole presents the form of a curved band.