Nussbaum, F., cited, [161].

Oasis, [216].

Oblateness, of the earth, [10].

Observational geology vs. speculative philosophy, [5].

Obsidian, [463].

Obsidian Cliff, [33].

Ocean of Tethys, [16].

Oceanic platform, [19].

Oceans, arrangement of, [10].

Oldham, R. D., cited, [72], [76], [92].