Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . SCIENTIFIC BALLOONING. 257 Observatoire cle la Meteorologie dynamique. Balloons areused, made of the lightest silk, cambric or paper, varnished withrubber solution or linseed oil; their capacities vary from 1,000to 17,500 cubic feet. The weight of the instruments is verysmall, and therefore the size of the balloon depends generallyon the height to which it is proposed to ascend. The net is of. Fig. 160.—Ascent of a balloon, fitted with a parachute, at Li
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . SCIENTIFIC BALLOONING. 257 Observatoire cle la Meteorologie dynamique. Balloons areused, made of the lightest silk, cambric or paper, varnished withrubber solution or linseed oil; their capacities vary from 1,000to 17,500 cubic feet. The weight of the instruments is verysmall, and therefore the size of the balloon depends generallyon the height to which it is proposed to ascend. The net is of. Fig. 160.—Ascent of a balloon, fitted with a parachute, at Lindenberg. very light construction ; it has merely to resist the internalpressure and carry the basket containing the has designed an arrangement whereby an alarumclock opens the valve after a certain time, and thereforecauses the balloon to descend after it has reached a certainheight. In order to prevent the effects of solar radiation, theballoon must be prevented from hovering in one position, so thatthe thermometers are continually brought into contact with s 258 AIKSHIPS PAST AND PRESENT. volumes of air, in a manner similar to that adopted in theaspirator-psychrometer. If the balloon is made to rise quicklyand then to fall at once, the thermometers give correct values;but if it is allowed to drift gently along, exposed to the rays ofthe sun, the readings will be too high. Attempts have beenmade to shield the instruments by placing them in a wickerbasket, covered with highly polished silver
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Keywords: ., bookcentury1900, bookdecade1900, bookpubl, booksubjectaeronautics
