photographed, [225].

Nilosyrtis, unlike other canals, [262].

Nitro-bacteria, [350], [353].

Nitrogen, [83], [164], [166], [341].

Nix Olympica, [74], [78].

North America, geologic history of, [133-137].

Oases, detected later than canals, [30], [249];

three stages in appearance of, [250-252];

number of, [252];

kinds of, [252-254], [263];