[Illustration: _Plate 21_ _THE SPIRAL NEBULA M 81, URSAE MAJORIS_] [Illustration: _Plate 22_ _THE NEBULA H.I.163, SEXTANTIS_] [Illustration: _Plate 23_ _THE SPIRAL NEBULA H.I.199, URSAE MAJORIS_] [Illustration: _Plate 24_ _THE DOUBLE NEBULA H.II 28-29, LEONIS_] [Illustration: _Plate 25_ _THE PLANETARY NEBULA H.IV 27, HYDRAE_] [Illustration: _Plate 26_ _THE NEBULA H.V 46, URSAE MAJORIS_] [Illustration: _Plate 27_ _THE OWL NEBULA, M 97, URSAE MAJORIS_] [Illustration: _Plate 28_ _THE SPIRAL NEBULA M 65, LEONIS_] [Illustration: _Plate 29_ _THE SPIRAL NEBULA M 66, LEONIS_] [Illustration: _Plate 30_ _THE SPIRAL NEBULA H.II, 730, URSAE MAJORIS_] [Illustration: _Plate 31_ _THE NEBULA H.V 41, CANUM VENATICORUM_] [Illustration: _Plate 32_ _THE SPIRAL NEBULA M 99, COMAE BERENICES_] [Illustration: _Plate 33_ _THE SPIRAL NEBULA H.V 43, URSAE MAJORIS_] [Illustration: _Plate 34_ _THE SPIRAL NEBULA M 61, VIRGINIS_] [Illustration: _Plate 35_ _THE SPIRAL NEBULA M 100, COMAE BERENICES_] [Illustration: _Plate 36_ _THE NEBULA H.I 197-198, CANUM VENATICORUM_] [Illustration: _Plate 37_ _THE SPIRAL NEBULA M 88, COMAE BERENICES_] [Illustration: _Plate 38_ _THE SPIRAL NEBULA H.V 2, VIRGINIS_] [Illustration: _Plate 39_ _THE SPIRAL NEBULA H.I 92, COMAE BERENICES_] [Illustration: _Plate 40_ _THE NEBULA H.V 24, COMAE BERENICES_] [Illustration: _Plate 41_ _THE NEBULA H.V 42, COMAE BERENICES_] [Illustration: _Plate 42_ _THE SPIRAL NEBULA H.I 84, COMAE BERENICES_] [Illustration: _Plate 43_ _THE SPIRAL NEBULA M 94, CANUM VENATICORUM_] [Illustration: _Plate 44_ _THE SPIRAL NEBULA M 94 CANUM VENATICORUM_] [Illustration: _Plate 45_ _THE SPIRAL NEBULA M 64, COMAE BERENICES_] [Illustration: _Plate 46_ _THE SPIRAL NEBULA M 63, CANUM VENATICORUM_] [Illustration: _Plate 47_ _THE SPIRAL NEBULA M 51, CANUM VENATICORUM_] [Illustration: _Plate 48_ _THE STAR CLUSTER M 3, CANUM VENATICORUM_] [Illustration: _Plate 49_ _THE SPIRAL NEBULA M 101, URSAE MAJORIS_] [Illustration: _Plate 50_ _THE DOUBLE NEBULA H.II 751-752, BOOTIS_] [Illustration: _Plate 51_ _THE NEBULA H.I 215, DRACONIS_] [Illustration: _Plate 52_ _THE STAR CLUSTER M 5, LIBRAE_] [Illustration: _Plate 53_ _THE STAR CLUSTER M 13, HERCULIS_] [Illustration: _Plate 54_ _THE STAR CLUSTER M 12, OPHIUCHI_] [Illustration: _Plate 55_ _THE TRIFID NEBULA, M 20, SAGITTARII_] [Illustration: _Plate 56_ _THE NEBULA M 8, SAGITTARII_] [Illustration: _Plate 57_ _THE PLANETARY NEBULA H.IV 37, DRACONIS_] [Illustration: _Plate 58_ _THE HORSE SHOE OR OMEGA NEBULA M 17, SAGITTARII_] [Illustration: _Plate 59_ _THE RING NEBULA, M.57, IN LYRA_] [Illustration: _Plate 60_ _THE DUMB-BELL NEBULA IN VULPECULA_] [Illustration: _Plate 61_ _THE ANNULAR NEBULA H.IV 13, CYGNI_] [Illustration: _Plate 62_ _THE SPIRAL NEBULA H.IV 76, CEPHEI_] [Illustration: _Plate 63_ _THE NET-WORK NEBULA IN CYGNUS_] [Illustration: _Plate 64_