Observations, scientific, mischief of inaccurate, 38; tendency of unconnected, 40.
Ocean, general view of, 292-311; its extent as compared with the dry land, 288, 289; its depth, 160, 302; tides, 304, 305; decreasing temperature at increased depths, 302; uniformity and constancy of temperature in the same spaces, 303; its currents and their various causes, 306-309; its phosphorescence in the torrid zone, 202; its action on climate, 303, 319-320; influence on the mental and social condition of the human race, 162, 291, 292, 294, 310; richness of its organic life, 300, 310; oceanic microscopic forms, 342, 343; sentiments excited by its contemplation, 310.
Oersted, electro-magnetic discoveries, 188, 191.
Olbers, comets, 104, 109; aerolites, 114, 118; on their planetary velocity, 121; on the supposed phenomena of ascending shooting stars, 123; their periodic return in August, 125; November stream, 126; prediction of a brilliant fall of shooting stars in Nov., 1867, 127; absence of fossil meteoric stones in secondary and tertiary formations, 131; zodiacal light, its vibration through the tails of comets, 143; on the transparency of celestial space, 152.
Olmsted, Denison of New Haven, Connecticut, observations of aerolites, 113, 118, 119, 124.
Oltmanns, Herr, observed continuously with Humboldt, at Berlin, the movements of the declination needle, 190, 191.
Ovid, his description of the volcanic Hill of Methone, 240.
Oviedo describes the weed of the Gulf Stream as Praderias de yerva (sea weed meadows), 308.
Palaeontology, 270-284.
Pallas, meteoric iron, 131.