Foucault pendulum: a straight cable to measure a rotation

The Foucault pendulum (1870) made it possible to demonstrate for the first time directly the phenomenon of Earth's rotation. It is a sphere of lead covered with iron and it suspended from the ceiling by a long steel cable that is put into oscillation to demonstrate the phenomenon of Earth's rotation.

Read more information in:
http://en.wikipedia.org/wiki/Foucault_pendulum
http://www.museoscienza.org/dipartimenti/catalogo_collezioni/scheda_oggetto.asp?idk_in=ST060-00037&arg=Astronomia