Victorian illustration to download showing a lecturer demonstrating the rotation of the earth with a Foucault pendulum to a large audience. The pendulum swings above a large circle, 16ft in diameter, the 360 degrees marked on it. The lecturer was Dr Bachhoffner (1810-79), a popular lecturer on scientific subjects, lecturing in 1851 at the Polytechnic Institute, London, of which he was a founder. Leon Foucault (1819-68), the French physicist, first demonstrated his pendulum in 1851 at the Pantheon, Paris.