Roulette (curve) in this case, the point lies on the circle then the roulette is a cycloid. A related concept is a glissette, the curve described by a point attached to a given curve as it slides along two (or more) given curves. Formally speaking, the curves must be differentiable curves in the Euclidean plane. The "fixed curve" is kept invariant; the "rolling curve" is subjected to a continuous congruence transformation such that at all times the curves are tangent at a point of contact that moves with the same speed when taken along either curve (another way to express this constraint
The Rolling Bridge to this bridge. At present, this curling bridge is the only one of its type known to be in existence. Traditional use of the term "rolling bridge" dates from at least the Victorian era, and is used to describe a type of retractable drawbridge used to span a ditch or moat surrounding a fortification. That type of bridge is not hinged, and remains horizontal when it is rolled inside the gates of a fort. Modern versions are called retractable bridges or "thrust bridges". One particular version of the rolling bridge type was known as the Guthrie rolling bridge, examples of