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Show Invention Tests Air. The Paris-London air service has an Ingenious instrument fer measuring measur-ing the depth of fog above the starting start-ing place at Oroydaa or Abbeville, and SQ to determine whether there is elear, dry weather a few hundred feet np. The Instrument, which Is based on the property of hamnn hair of contracting con-tracting sharply on passing from wet o dry air, consists of a hair attnehed to a trigger that helds a ring. The instrument is sent aloft with toy balloons bal-loons on a string; as soon ns It reaehes dry air the hair contracts, pulls the trigger, and down conies the ring on ths string. Youth's Companion- |