Iapetus, Distance and Period of, 392.
Identification of Comets, 258.
India-rubber Ball, Height of, 19.
Inner Planets, The, 134.
Insects, Leaf-like, 204.
Institution, Royal, 53.
Internal Heat of Earth, 115.
Inventory of Worlds, 379.
Iris of the Eye, 202.
Iron Vapor, 291.
Island, Caroline, 42.