Mehl, Adolf. Der freiballon in Theorie und Praxis(Free Balloons in Theory and Practice). Stuttgart, Franckh'fchen, n.d. (ca. 1912). Vol I 259pp, Vol II 266pp, illus, dj, original box. 5.5x8", about very good. End papers have color tables of the 50 colored pennants of flying clubs throughout Germany. Some edge chips to dj. A beautifully illustrated set; Vol I is mostly history and ballooning basics including equipment on board, flying fields, etc. Vol II covers meteorology and more details on equipment including gas generators. German text.