245
Cathedral of Milan, in order to gradually educate the population to the new time
system while awaiting the introduction of mean time.
Fr. Secchi, in his 1877 account L’Astronomia in Roma nel Pontificato di Pio IX
(Astronomy in Rome in the Pontificate of Pius IX), outlined the history of the time
service in the city, taking care to clarify various aspects of the situation
6
:
Soon after Pope Pius IX had taken the throne, he wanted to relieve Rome of this anomaly
of counting the time by the Italian method, marking 24 hours beginning at half an hour after
sunset, which was very inconvenient especially for visitors from abroad and which had no
reason to exist any longer, given the current rapid movement of communication between
nations. (...) The Pontiff therefore wished to replace this system, and he established the
common European usage of counting the hours from midnight.
The main difficulty of this hourly reform was to engage and bring along the public, for whom the official time signal had to be given every day. So it was decided
that, starting on December 1, 1847, the local midday time, as inferred from the regulatory pendulum of the Observatory of the Roman College, would be communicated
visually to Castel San Angelo, where it would be marked with the firing of a cannon (Secchi 1877).
7
When he began his directorship of the Roman College Observatory, Secchi took
care to maintain and perfect this time service for the city, as he described in his 1850
report Restauri fatti all’Osservatorio (Renovations made to the Observatory):
Among the notable improvements made at the observatory one would not want to neglect
mentioning the erection of a new device to give the public an indication of the mean noontime (...) The signal first tentatively adopted was a large black flag with a white star in the
center that was raised on top of the tower 5 minutes before the midday, and then lowered at
the precise instant of noon. But after a strong wind last year (1850) toppled the flagpole that
held it, with grave danger to those who were standing nearby, it was determined to replace
it with a sphere that was raised to the top of an long pole some time beforehand, and then
lowered instantly at noon. The height of the pole is 48 Roman palms or 10.72 meters, and
the diameter of the sphere 7 palms or 1.56 meters. This sphere is made of an iron shell
covered with canvas, and impaled on the pole as is done at the Royal Observatory in
Greenwich in order to avoid it shaking in the wind. A small electric telegraph connects the
clock to the chamber with the machine that drops the ball: 6 seconds before noon the telegraph gives the signal to drop the ball to the person stationed there, who drops it immediately, and if the cannoneer is ready to fire his piece, the gunshot reaches the Observatory at
exactly the middle of the day, and thus strikes the first stroke of the public clock.
The signal was first transmitted from the Calandrelli Tower, but after the construction of the new observatory, it originated from the gable of the facade of St.
Ignatius Church (Secchi 1856). Thus the Roman College became the new time reference for the City, taking over from Bianchini’s monumental meridian line in the
Basilica of Santa Maria degli Angeli, where the solar transit indicated the true
6 This publication was described and graciously provided by Mr. Renzo Lai, a former official of the
Library of the Pontifical Gregorian University, who is very much thanked.
7 The ritual of firing of the Castel San Angelo cannon created a certain fascination on the part of
many Romans who would gather at various places in the city, clocks in hand, to wait for it.
15 Angelo Secchi and the Measurement of Time
Cathedral of Milan, in order to gradually educate the population to the new time
system while awaiting the introduction of mean time.
Fr. Secchi, in his 1877 account L’Astronomia in Roma nel Pontificato di Pio IX
(Astronomy in Rome in the Pontificate of Pius IX), outlined the history of the time
service in the city, taking care to clarify various aspects of the situation
6
:
Soon after Pope Pius IX had taken the throne, he wanted to relieve Rome of this anomaly
of counting the time by the Italian method, marking 24 hours beginning at half an hour after
sunset, which was very inconvenient especially for visitors from abroad and which had no
reason to exist any longer, given the current rapid movement of communication between
nations. (...) The Pontiff therefore wished to replace this system, and he established the
common European usage of counting the hours from midnight.
The main difficulty of this hourly reform was to engage and bring along the public, for whom the official time signal had to be given every day. So it was decided
that, starting on December 1, 1847, the local midday time, as inferred from the regulatory pendulum of the Observatory of the Roman College, would be communicated
visually to Castel San Angelo, where it would be marked with the firing of a cannon (Secchi 1877).
7
When he began his directorship of the Roman College Observatory, Secchi took
care to maintain and perfect this time service for the city, as he described in his 1850
report Restauri fatti all’Osservatorio (Renovations made to the Observatory):
Among the notable improvements made at the observatory one would not want to neglect
mentioning the erection of a new device to give the public an indication of the mean noontime (...) The signal first tentatively adopted was a large black flag with a white star in the
center that was raised on top of the tower 5 minutes before the midday, and then lowered at
the precise instant of noon. But after a strong wind last year (1850) toppled the flagpole that
held it, with grave danger to those who were standing nearby, it was determined to replace
it with a sphere that was raised to the top of an long pole some time beforehand, and then
lowered instantly at noon. The height of the pole is 48 Roman palms or 10.72 meters, and
the diameter of the sphere 7 palms or 1.56 meters. This sphere is made of an iron shell
covered with canvas, and impaled on the pole as is done at the Royal Observatory in
Greenwich in order to avoid it shaking in the wind. A small electric telegraph connects the
clock to the chamber with the machine that drops the ball: 6 seconds before noon the telegraph gives the signal to drop the ball to the person stationed there, who drops it immediately, and if the cannoneer is ready to fire his piece, the gunshot reaches the Observatory at
exactly the middle of the day, and thus strikes the first stroke of the public clock.
The signal was first transmitted from the Calandrelli Tower, but after the construction of the new observatory, it originated from the gable of the facade of St.
Ignatius Church (Secchi 1856). Thus the Roman College became the new time reference for the City, taking over from Bianchini’s monumental meridian line in the
Basilica of Santa Maria degli Angeli, where the solar transit indicated the true
6 This publication was described and graciously provided by Mr. Renzo Lai, a former official of the
Library of the Pontifical Gregorian University, who is very much thanked.
7 The ritual of firing of the Castel San Angelo cannon created a certain fascination on the part of
many Romans who would gather at various places in the city, clocks in hand, to wait for it.
15 Angelo Secchi and the Measurement of Time