History of aviation first published in 1915. According to the Preface: " Around the dry land of the earth are the oceans of water. We may never have seen them, but we have knowledge of them and their navigation, and their names suggest very definite and concrete objects of thought. We sometimes do not realize, however, that we live and move and have our being at the bottom of a vaster and deeper ocean that covers to a depth of many miles the whole earth, and to the surface of which man nor beast nor bird has ever ascended; an ocean with currents and whirlpools and waves of more than mountain height; an ocean in which we are as much at home as are the finny tribes and the monsters of the deep in their watery caverns. This is the ocean of the air. ?