16. SEISMOGRAM RECORDED AT SHIDE, ISLE OF WIGHT, ON AUGUST 31, 1898 35 17. PHOTOGRAPH OF THE SURFACE OF THE MOON, IN THE VICINITY OF THE CRATER OF COPERNICUS 62 18. SUN-SPOT GROUP AND GRANULATION OF THE SUN 74 19. PART OF THE SOLAR SPECTRUM OF JANUARY 3, 1872 75 20. METALLIC PROMINENCES IN VORTEX MOTION 76 21. FOUNTAIN-LIKE METALLIC PROMINENCES 76 22. QUIET PROMINENCES OF SMOKE-COLUMN TYPE 77 23. QUIET PROMINENCES, SHAPE OF A TREE 77 24. DIAGRAM ILLUSTRATING THE DIFFERENCES IN THE SPECTRA OF SUN-SPOTS AND OF THE PHOTOSPHERE 78 25. SPECTRUM OF A SUN-SPOT, THE CENTRAL BAND BETWEEN THE TWO PORTIONS OF THE PHOTOSPHERE SPECTRUM 78 26. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 79 27. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 80 28. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 81 29. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 82 30. PHOTOGRAPH OF THE SOLAR CORONA OF 1900 83 31. PHOTOGRAPH OF THE SOLAR CORONA OF 1870 84 32. PHOTOGRAPH OF THE SOLAR CORONA OF 1898 85 33. PHOTOGRAPH OF ROERDAM’S COMET (1893 II.), SUGGESTING SEVERAL STRONG NUCLEI IN THE TAIL 100 34. PHOTOGRAPH OF SWIFT’S COMET (1892 I.) 101 35. DONATI’S COMET AT ITS GREATEST BRILLIANCY IN 1858 102 36. IMITATION OF COMETS’ TAILS 104 37. GRANULAR CHONDRUM FROM THE METEORITE OF SEXES. ENLARGEMENT 1:70 109 38. ARCH-SHAPED AURORÆ BOREALIS, OBSERVED BY NORDENSKIOLD DURING THE WINTERING OF THE VEGA IN BERING STRAIT 1879 124 39. AURORA BOREALIS, WITH RADIAL STREAMERS 125 40. AURORA WITH CORONA, OBSERVED BY GYLLENSKIÖLD ON SPITZBERGEN, 1883 126 41. POLAR-LIGHT DRAPERIES, OBSERVED IN FINNMARKEN, NORTHERN NORWAY 127 42. CURVE OF MAGNETIC DECLINATION AT KEW, NEAR LONDON, ON NOVEMBER 15 AND 16, 1905 138 43. CURVE OF HORIZONTAL INTENSITY AT KEW ON NOVEMBER 15 AND 16, 1905 139 44. ZODIACAL LIGHT IN THE TROPICS 146 45. SPECTRUM OF NOVA AURIGÆ, 1892 154