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height and 20 feet in width, and the track is 4 feet wide. The movable section oscillates on a 3-inch trun nion. Springs are provided to assist its quick move ment, and its upper end is heavily counter-weighted by iron bars which slide in between the girders. The releasing mechanism consists of a one-foot hinged movable section of the floor of the circle extend ing across the entire width of the roadway. The rider stands upon the blocks on the incline, which serve to raise the riderdoi:10.1038/scientificamerican05091903-357 fatcat:3ojayyhjpnex7bowhqnqluqd2u