"The Flume was discovered in 1808 by 93-year-old “Aunt” Jess Guernsey when she accidently came upon it while fishing. She had trouble convincing her family of the marvelous discovery, but eventually persuaded others to come and see for themselves. At that time, a huge egg-shaped boulder hung suspended between the walls. The rock was 10 feet (3m) high and 12 feet (3.6m) long. A heavy rainstorm in June of 1883 started a landslide that swept the boulder from its place. It has never been found. The same storm deepened the gorge and formed Avalanche Falls." (nhstateparks)