This narrow gorge, seven hundred feet in length with granite walls sixty to seventy feet high, was formed thousands of years ago when magma filled an east-west fracture in the side of Mt. Liberty. Erosion from water flowing over this lava dike through the ages created the Flume seen today. Its walls are overarched by a forest canopy and covered with mosses, ferns, and flowers that in summer produce a tapestry of color, while the floor where Flume Brook flows is strewn with rocks deposited eons ago. In winter, great icicles hang from the walls. For centuries, a large egg-shaped boulder hung suspended between the walls of the gorge until June 20, 1883, when a cloudburst on Mt. Liberty started an avalanche of water, earth, rock, and trees that roared through the Flume and carried the stone away. According to local folklore, the Flume was discovered in 1808 by "Aunt Jess" Guernsey, a pioneer of the region, who at age ninety-three went trout fishing and returned home telling of a great chasm. At first no one believed her, but later word reached the outside world and brought visitors to this natural wonder.