Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . e the exposure, and it is hardlynecessary to say that the taking of photographs under theseconditions is a matter requiring much experience. Horizontal movements of the balloon exert less effect upon thesharpness of the image, the greater the distance of the objectfrom the lens; with rotatory movements the reverse is the case,and the nearer the object, the sharper will be the image. Oscil-latory swings, like those of a pendulum, mostly occur at thestart,
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . e the exposure, and it is hardlynecessary to say that the taking of photographs under theseconditions is a matter requiring much experience. Horizontal movements of the balloon exert less effect upon thesharpness of the image, the greater the distance of the objectfrom the lens; with rotatory movements the reverse is the case,and the nearer the object, the sharper will be the image. Oscil-latory swings, like those of a pendulum, mostly occur at thestart, particularly if the envelope is not vertically above thebasket; but they disappear very soon. In the kite-balloon they 294 AIKSHIPS PAST AND PEE SENT. ; are seldom met with, but with captive balloons they are of fre-quent occurrence. It is obvious that these oscillations may pro-duce very serious consequences on the negative. Dr. Stolze saysthat the basket performs an oscillation in 4 seconds, if it is at adistance of 50 ft. from the top of the balloon. Consequently ina tenth of a second it will perform one-fortieth of an Fig. 184.—Eastern Kailway Station, in Budapesth.(Photograph by Lieutenant Krai.) Let us suppose that a complete oscillation extends over an angleof two degrees, and that the time of exposure is to be one-tenthof a second. Then the basket in this time will oscillate throughan angle of three minutes, and this will cause an entire blurringof the image if the object is at a distance of 5 or 6 of this kind are always larger in the case of smallballoons, and it is not possible to neutralise their effect bydecreasing the time of exposure. Dr. Stolze has made use of theprinciple of the gyroscope in this connection. He arranges two BALLOON PHOTOGKAPHY. 295 discs on axes at right angles to one another, and these are capableof being rotated by means of strings. The discs are joined bymeans of a ball and socket joint to the camera,, whi
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