American Bridge

By the early 1900s there were four telescope domes on the walls of the Vatican: The equatorial photographic telescope Carte du Ciel was located on the Leonine Tower, which was later renamed the Tower of St John. A large refracting telescope, the Visuale, was sited on what later came to be called the Tower of Pius X. A telescope specially designed for photographing the sun, a heliograph, was located on the terrace of what is now the residence of emeritus Pope Benedict XVI. Finally, a 10.2 cm Merz telescope was located on the semi-circular “half-tower”.

In 1854 a section of the Vatican wall connecting these various towers had collapsed, so that in order to go from one telescope to another the astronomers had to descend from the wall and then climb back up, a serious inconvenience. An architect from Chicago proposed to Fr. Hagen that this problem would be resolved by installing a metal bridge, connecting across the gap in the wall. An 85 m bridge was constructed in 1907, on four steel pillars. But the bridge was not much appreciated by Roman urban planners, and it was demolished soon after the Observatory’s transfer to Castel Gandolfo in 1935.