PREFACE. THE modern application of ballooning to scientific purposes has caused a widespread interest to be taken in the sport, and this has been intensified by the successes which have attended the efforts of Santos Dumont and the brothers LBbaudy in another direction. The present moment,therefore, seems to be suitable for a survey of the development of the art, and, in making this attempt, the author has drawn on a large number of sources that have not hitherto been accessible to the general reader, and has also supplemented the historical outline with the result of many years of practical experience. The following pages contain a rough sketch of the past and present state of the art, and its , applications to scientific ends, and further it is hoped that the looker-on may find in them something to help him towards understanding the various problems which are now calling for solution and afford such a fruitful subject for discussion in the daily press. Certain matters have been described in some detail, such, for instance, as balloon photography and the use of the carrier pigeon and this has seemed to be desirable, seeing that hitherto no trustworthy information on these subjects has been forthcoming. Balloon photography has been very carefully studied of late years. The author can lay claim to considerable experience in this department, and has made about eighty ascents, mainly for photographic purposes. He has also had the advantage of Profossor hliethes assistance on many of these occasions, and Lieutenant-Colonel Klussman, who was formerly in command of the Prussian Balloon Corps, has also kindly contributed much valuable information as to the various optical phenomena that arise in balloon photography.....