Congreve's rolling ball clock, a 1972 copy of William Congreve's 1808 original, now in the collection of Greenwich Heritage Centre, Woolwich, south east London, UK.
<a href="//commons.wikimedia.org/wiki/User:Kleon3" title="User:Kleon3">Kleon3</a>
<span class="int-own-work" lang="en">Own work</span>