Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . ke off some of the dead-weight. The lens must be verycarefully handled, and experi-ence seems to show that afew words on this subject willnot be out of place. A veryimportant point is to cleanthe lens by means of a softcamels hair brush from any Fig. Spelterini, of Zurich. dugt ^ mfty haye settM Qn it; the need for this is fairly obvious, and the reasons have beenalready mentioned. It is necessary to pay special attention toany alterations in
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . ke off some of the dead-weight. The lens must be verycarefully handled, and experi-ence seems to show that afew words on this subject willnot be out of place. A veryimportant point is to cleanthe lens by means of a softcamels hair brush from any Fig. Spelterini, of Zurich. dugt ^ mfty haye settM Qn it; the need for this is fairly obvious, and the reasons have beenalready mentioned. It is necessary to pay special attention toany alterations in the level of the balloon. As soon as it passesfrom a cold atmosphere into a warm, damp one, the surface ofthe lens will be covered with a thin film of moisture, and ablurred exposure would result. It is doubtful whether this matteralways receives sufficient attention. Often enough the sky isperfectly clear, and yet failures are the only result. The causeis quite likely to be found in the fact that the lens has not beenproperly cleaned. In a balloon, moisture is very frequentlydeposited on the lens. The camera has perhaps been put away. PHOTOGKAPHIC OUTFIT FOR BALLOON WORK. 321 in a corner of the basket, where it is well protected from the raysof the sun, and it has about the same temperature as the surround-ing atmosphere, which is generally far lower than that of theearth. A film, of moisture has therefore probably coated the is possible to use a sliding tube of highly-polished metal toprotect the lens from the suns rays; and if the sun is low downit might prevent its direct light from shining on the lens. Theinner surface of such a tube must of course be coated with a mattblack paint, in order to prevent any irregular reflection. The Development of the Plates. Every photographer knows that he can do much to save aplate which has not been properly exposed by suitably carryingout the developing process. The developer can be strengthenedor diluted; potassium bromide or
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Keywords: ., bookcentury1900, bookdecade1900, bookpubl, booksubjectaeronautics
