Effect of Magnet on wide Air (Aurora) tube: pp. 149-153. Stratification (note on): pp. 149, 150. Effect of magnet on Plücker (air-) tube: pp. 150-152. Effect of magnet on Plücker tube (tin chloride): pp. 152, 153. Effect of magnet on tin-chloride Geissler tube: p. 153. CHAPTER XVII. Effect of Magnet on bulbed Phosphorescent Tube: pp. 154-156. Effect of magnet on small phosphorescent (powder) tubes: pp. 156, 157. Lighting-up tubes with one wire only (Marquis of Salisbury’s observations): pp. 157, 158. CHAPTER XVIII. Action of the Magnet on the Electric Spark: pp. 159, 160. CHAPTER XIX. The Discharge _in vacuo_ in Larger Vessels, and Magnetic Effects thereon: pp. 161-165. Some of Baron Reichenbach’s magnetic researches tested: pp. 165, 166. Summary of the foregoing Experiments and their Results: p. 167. CHAPTER XX. Some concluding Remarks: pp. 168-171. APPENDICES. A. References to some Works and Essays on the Aurora: pp. 173, 174. B. Extracts from the Manual and Instructions for the (English) Arctic Expedition, 1875: pp. 175-181. C. Extracts from Parliamentary Blue-book, containing the “Results derived from the Arctic Expedition, 1875-76:” pp. 182-188. D. Aurora and Ozone: pp. 189-193. E. Dr. Vogel’s Inquiries into the Spectrum of the Aurora: pp. 194-207. LIST OF PLATES. Plate. I. The Aurora during the Ice-pressure _To face page_ 14 II. Aurora seen by Dr. Hayes, 6th January, 1861 ” ” 16 III. Aurora, Guildford, Oct. 24, 1870 ” ” 18 IV. Aurora, Guildford, Feb. 4, 1872; Eclipsed Moon, Aug. 23, 24, 1877 ” ” 20 V. Corona, Graphical Auroræ, Zodiacal Light, &c. ” ” 21 VI. Aurora, Guildford, Feb. 4, 1874; Spectrum des Nordlichts (Vogel) ” ” 22 VII. Aurora, Kyle Akin, Isle of Skye, Sept. 11, 1874 ” ” 24 VIII. Herr Carl Bock’s Lapland Aurora, Oct. 3, 1877 ” ” 25 IX. Compared Aurora and other Spectra. Loomis’s curves of Auroras, Magnetic Declination, and Solar Spots ” ” 59 X. Spectroscope, Micrometer, Tubes ” ” 91 XI. Aurora-spectra, Candle-spectrum ” ” 102 XII. Aurora-spectrum, Solar spectrum, and Candle-spectrum ” ” 104 XIII. Vogel’s Aurora-lines, Aurora-lines near G, and in the red and green ” ” 108 XIV. Aurora, Hydrocarbons, Oxygen ” ” 110