Eiffel Tower was to be dismantled in 1909, when its ownership would revert to the City of Paris. The City had planned to tear it down (part of the original contest rules for designing a tower was that it should be easy to dismantle) but as the tower proved to be valuable for communication purposes, it was allowed to remain after the expiry of the permit. Eiffel made use of his apartment at the top of the tower to carry out meteorological observations, and also used the tower to perform experiments on the action of air resistance on falling bodies. For the
Gustave Eiffel designed by Charles Garnier, later among the most prominent critics of the Tower. The dome, with a diameter of , was the largest in the world when built and used an ingenious bearing device: rather than running on wheels or rollers, it was supported by a ring-shaped hollow girder floating in a circular trough containing a solution of magnesium chloride in water. This had been patented by Eiffel in 1881. The design of the Eiffel Tower was originated by Maurice Koechlin and Emile Nouguier, who had discussed ideas for a centrepiece for the 1889 Exposition Universelle. In May 1884 Koechlin,