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This document presents detailed investigative records of Incident #75, a reported unidentified flying object sighting near Twin Falls, Idaho on August 13, 1947. A farmer and his two sons (ages ten and eight) witnessed a sky-blue, disk-shaped object traveling through Snake River Canyon at approximately 75 feet altitude and 300 feet distance. The object moved east to west, following ground contours, made a swishing sound, and measured roughly 20 by 10 feet. Witnesses reported observing turbine or exhaust flames from the device and notably described trees spinning "as if they were in a vacuum" as it passed overhead. The document includes witness statements, sketches, FBI correspondence, and Dr. Hynek's scientific evaluation. Hynek concluded the object was likely a rapidly moving atmospheric eddy. The document also catalogs 244 UFO incidents from Project Grudge, categorizing them by astronomical probability, conventional explanations (balloons, aircraft, rockets), or lack of evident explanation.