Investigators first of all checked with officials at Lowry Air Force Base, which served as a plotting center for all Skyhook balloons, but there were none in the East that day. Next they checked the possibility that the UFO had been a weather balloon, but nearby weather stations replied that none of their balloons could have been responsible for the sightings. After calling other stations within a 150-mile radius of Gordonsville with negative results, investigators called the weather station at Pittsburgh, Pennsylvania. A radiosonde (a small balloon attached to an instrument for taking soundings in the upper atmosphere) had been released that afternoon, but had been lost about sixty miles southeast of the station when it apparently sprung a slow leak and leveled off at 60,000 feet. The weather man at Pittsburgh offered to plot its probable course as determined by the prevailing winds, and soon telephoned Dayton to report that the UFO was probably their balloon. Southeast of Pittsburgh above 50,000 feet there was a strong current of air that fed into a stronger southerly stream flowing parallel to the Atlantic coast, just east of the Appalachian Mountains. The balloon would have floated along in this current like a log floating down a river, and should have arrived in the neighborhood of Gordonsville and Blackstone in the late afternoon or early evening. The UFO had been sighted near Gordonsville between 4:43 and 5:43 P.M., and near Blackstone between 7:35 and 8:00 P.M. The unknown was thus clearly identified as the lost radiosonde. _Skyhook and Pibal UFOs_ The year 1952 was a big year for experimental balloons--and for UFO sightings. Weather balloons in clusters, 100-foot Skyhooks, radiosondes, pibals (pilot balloons sent up to show the direction and speed of the wind) were released on schedule all over the continent. Launchings were recorded and the balloons were tracked, as far as possible, so that for any given day or area ATIC could consult a map and try to correlate the position of a known balloon with that of a reported flying saucer. When a balloon was lost, any UFO sightings it caused were not always easy to account for until--and unless--the balloon could be found again. These spheres of gas vary in size from a few inches in diameter to some two hundred feet. Often they look and behave very unlike the popular concept of a “normal” balloon, and under the right conditions they can fool even the most wary observer--particularly if he is more or less expecting to see something strange.