A third type of wave is a torsional or twisting wave. If you stretch a slinky out between two points and gently twist it at one end, the twist will travel down the slinky as a wave pulse. This is an example of a torsional wave. We saw two YouTube examples of bridges undergoing torsional motion in the last chapter: twisting bridge, Tacoma Narrows. These were examples of standing torsional waves.