Gustave Eiffel placed his tower under the symbolic protection of seventy-two men of science whose names are engraved on the perimeter of the first floor. As early as 1889, the Eiffel Tower became the site of scientific experiments designed to demonstrate its usefulness after 1909, when the 20-year concession granted by the City of Paris came to an end. A giant Foucault pendulum was fixed under the second floor to demonstrate the forces that govern the rotation of the earth. A 300-metre-high mercury manometer accurately measured high pressures and calibrates industrial manometers. A weather station provided daily data published by Gustave Eiffel.