although successful heavier-than-air flight is less than two decades old, and successful dirigible propulsion antedates it by a very short period, the mass of experiment and accomplishment renders any one-volume history of the subject a matter of selection. in addition to the restrictions imposed by space limits, the material for compilation is fragmentary, and, in many cases, scattered through periodical and other publications. hitherto, there has been no attempt at furnishing a detailed account of how the aeroplane and the dirigible of to-day came to being, but each author who has treated the subject has devoted his attention to some special phase or section. the principal exception to this rule—hildebrandt—wrote in 1906, and a good many of his statements are inaccurate, especially with regard to heavier-than-air experiment.

such statements as are made in this work are, where possible, given with acknowledgment to the authorities on which they rest. further acknowledgment is due to lieut.-col. lockwood marsh, not only for the section on aeroplane development which he has contributed to the work, but also for his kindly assistance and advice in connection with the section on aerostation. the author’s thanks are also due to the royal aeronautical society for free access to its valuable library of aeronautical literature, and to mr a. vincent clarkeviii for permission to make use of his notes on the development of the aero engine.

in this work is no claim to originality—it has been a matter mainly of compilation, and some stories, notably those of the wright brothers and of santos dumont, are better told in the words of the men themselves than any third party could tell them. the author claims, however, that this is the first attempt at recording the facts of development and stating, as fully as is possible in the compass of a single volume, how flight and aerostation have evolved. the time for a critical history of the subject is not yet.

in the matter of illustrations, it has been found very difficult to secure suitable material. even the official series of photographs of aeroplanes in the war period is curiously incomplete, and the methods of censorship during that period prevented any complete series being privately collected. omissions in this respect will probably be remedied in future editions of the work, as fresh material is constantly being located.

e. c. v.

october, 1920.