Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . den. But we must not go to extremes, or wemay find the engineer hoist with his own petard. Thus it wasclearly an excess of zeal which prompted the Chief of the Berlinpolice to prohibit all ascents in the year 1884 before the 15th ofAugust, on the ground that otherwise much damage might bedone to the crops by the descent of the balloon. Generallyspeaking, since the introduction of the ripping-cord in Germany, BALLOONING AS A SPORT. 231 the number of accid
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . den. But we must not go to extremes, or wemay find the engineer hoist with his own petard. Thus it wasclearly an excess of zeal which prompted the Chief of the Berlinpolice to prohibit all ascents in the year 1884 before the 15th ofAugust, on the ground that otherwise much damage might bedone to the crops by the descent of the balloon. Generallyspeaking, since the introduction of the ripping-cord in Germany, BALLOONING AS A SPORT. 231 the number of accidents has greatly decreased; even in a stiffwind the dangers of being dragged and bumped along the groundare much smaller if the envelope is suddenly emptied of its landing normally takes place somewhat as As soonas it is determined to make the descent a suitable spot is selected,partly by consulting the map, and partly by taking account of thegeneral lie of the land. When the place has been chosen, arough calculation must be made as to the height at which it isbest to open the valve. Experience shows that the fall takes. Fig. 142.—Landing in a tree. place at the rate of 8 or 10 ft. per second; therefore, if thehorizontal velocity is known, as also the distance of the point ofdescent, it is easy to fix the level at which the valve must beopened. The rate of falling is about 6 miles an hour, and letus suppose that the balloon is travelling at a speed of 12 milesan hour, the distance of the spot selected for landing being onemile, , 5,280 ft. The height at which the valve must beopened will be -fy X 5,280, , 2,640 ft. Shortly before thelanding place is reached the balloon must be brought to rest bymeans of the guide-rope, ballast being thrown out if necessary. 1 See Dr. Richard Emdens article on the Theory of Landing,* in the IllnstrierteAeronaiitiscJie Mitteilungen for March, 1906. 232 AIRSHIPS PAST AND PRESENT. This is a very simple matter if there are
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