Ogden Canyon, curious example of a rock fold, [238]
Ohio River, how the Old Men of the Mountain helped it by turning some rivers around, [31]
Omar Khayyam, answer of Science to the universal riddle that puzzled him, [261]
Origin of Species. (See [Evolution].)
Oxygen, its use in making the world's air, [16];
how the sea feeds oxygen to the corals, [225]
Pack Rat, his remarkable fortress in the desert, [187]
Paleontologists, the wizards of queer anatomies and the strange forms they conjure up from the fragments of old bones, [266]
Palestine. (See [Dead Sea].)
Palisades, how they were made in the "Middle Ages," [241]
Pebbles, how they tell of old sea beaches on inland mountain and hill, [14];
their enormous age, [18];
dramatic stories the pebble scratches tell, [26];
how the Old Men of the Mountain used pebbles in turning New England rivers around, [31];
how pebbles helped deepen the basins of the Great Lakes, [34];
how they still help run the thousand-year clock at Niagara Falls, [35];
how they help the glaciers talk, [56];
why the pebbles of Glacier Land can't walk as the big stones do, [62];
how the river pebbles act as bankers for the farmers and the sea, [80];
how the pebbles helped dig the Grand Canyon, [82];
how they tell about doings in the Fairyland of Change, [97];
how a pebble may, in its time, play many parts, [99];
how they help unravel the secrets of the hills, [119];
how they help dying rivers multiply by two, [167];
how they report the fact that the storms on the Sea of Galilee are particularly severe, [203];
their fixed place in the rock-making system of the sea, [227];
how they tell of rough experiences in river travel, [250];
and of high winds at sea, desert sandstorms, rides on glaciers, and in what compartments they travel, [251]