1930. From a series of letters to the author's small nephew to explain to him about the formation of rivers, mountains, clouds, the earth and the stars. Contents: When the Earth Was Hot; The Air We Breathe; Seaweed and Jellyfish; Shells and Fishes; Mountains and Rivers; Volcanoes; Silurian Period; Devonian Period; Carboniferous Period; Glaciers; Permian Period; Triassic Period; Jurassic Period; Cretaceous Period; Eocene Period; Oligocene Period; Miocene Period; Pliocene Period; Pleistocene Period; and An Imaginary Period.