147
268–9). Results obtained by Secchi were later criticised by the physicist John
Ericsson (1803–1889) in 1876 (Cavanaugh 1999). His own trials, using similar
apparatus supplied by Casella, gave values exceeding 10 million K (Ericsson 1876:
317–26). All these experiments were subsequently overshadowed by the discovery
of the relationship of black-body radiation against temperature (Stefan-Boltzmann
law). This theoretical understanding allowed physicist Josef Stefan (1835–1893) to
calculate a solar surface temperature (5700 K), close to modern values (5778 K),
using data from Soret (Crepeau 2007; Stefan 1879: 391–428).
8.4 Universal Meteorograph
Secchi’s interest in telegraphy and his understanding of the new technology allowed
him to apply it to the collecting and recording of meteorological data. When Secchi
moved the Collegio Romano Observatory to the top of the St. Ignatius church, along
with installing a new Merz telescope, he established the first magnetic observatory
in Italy; but he left the meteorological instruments in their previous location nearby.
Later these measuring instruments were linked by mechanical and electromechanical means to a meteorograph housed in the observatory. The measurements collected were integrated into the new centralised system of information gathering that
had been established in the Papal State after the revolutionary upheavals of
1848–1849 (Mazzotti 2010: 62–3; Beltrano and Iafrate, Chap. 9 in this volume).
Created between 1850 and 1865, Secchi contrived a set of meteorological instruments into a “Meteorografo” (Brenni, Chap. 10 in this volume). The culmination of
his experimentation was his universal meteorograph, which was displayed and
awarded a medal at the Paris Exposition of 1867 (Secchi 1870b: 6–10). The immense
and complex mechanism was very costly, with Pope Pius IX donating 20,000 francs
for the completion of the instrument (Mazzotti 2010: 64). After its successful operation in Rome and exhibition in Paris, it was installed at the Collegio Observatory
where it functioned until the 1880s (Brenni 1992) (Fig. 8.6).
Fed by auxiliary meteorological instruments that were linked by electromechanical means, the immense meteorograph (length 1.5 m; depth 0.6 m; height 2.7 m)
recorded 5 parameters on 2 drum-driven paper charts with 12 recording pens. The
meteorological data were provided by a balance barometer, a bimetallic thermometer, a cup anemometer with wind vane, a psychrometer (wet/dry thermometer
hygrometer) and a pluviometer (rainfall amount/rate). Built in Rome by the instrument maker E. Brassart, the mechanism contained 11 telegraph transmitters, 6
counting mechanisms, a pendulum clock by Detouche of Paris and countless levers,
pulleys and weights. The complexity of the meteorograph can be gathered by contemporary accounts (Brassart 1872) and the explanation provided by Paolo Brenni
after the instrument’s cleaning and overhaul at the Museo di Storia della Scienza in
Florence (Brenni 1993). Due to its high cost and complexity, not many of Secchi’s
instruments were ever made (Brenni, Chap. 11 in this volume).
8 Angelo Secchi, Instrument Innovator
268–9). Results obtained by Secchi were later criticised by the physicist John
Ericsson (1803–1889) in 1876 (Cavanaugh 1999). His own trials, using similar
apparatus supplied by Casella, gave values exceeding 10 million K (Ericsson 1876:
317–26). All these experiments were subsequently overshadowed by the discovery
of the relationship of black-body radiation against temperature (Stefan-Boltzmann
law). This theoretical understanding allowed physicist Josef Stefan (1835–1893) to
calculate a solar surface temperature (5700 K), close to modern values (5778 K),
using data from Soret (Crepeau 2007; Stefan 1879: 391–428).
8.4 Universal Meteorograph
Secchi’s interest in telegraphy and his understanding of the new technology allowed
him to apply it to the collecting and recording of meteorological data. When Secchi
moved the Collegio Romano Observatory to the top of the St. Ignatius church, along
with installing a new Merz telescope, he established the first magnetic observatory
in Italy; but he left the meteorological instruments in their previous location nearby.
Later these measuring instruments were linked by mechanical and electromechanical means to a meteorograph housed in the observatory. The measurements collected were integrated into the new centralised system of information gathering that
had been established in the Papal State after the revolutionary upheavals of
1848–1849 (Mazzotti 2010: 62–3; Beltrano and Iafrate, Chap. 9 in this volume).
Created between 1850 and 1865, Secchi contrived a set of meteorological instruments into a “Meteorografo” (Brenni, Chap. 10 in this volume). The culmination of
his experimentation was his universal meteorograph, which was displayed and
awarded a medal at the Paris Exposition of 1867 (Secchi 1870b: 6–10). The immense
and complex mechanism was very costly, with Pope Pius IX donating 20,000 francs
for the completion of the instrument (Mazzotti 2010: 64). After its successful operation in Rome and exhibition in Paris, it was installed at the Collegio Observatory
where it functioned until the 1880s (Brenni 1992) (Fig. 8.6).
Fed by auxiliary meteorological instruments that were linked by electromechanical means, the immense meteorograph (length 1.5 m; depth 0.6 m; height 2.7 m)
recorded 5 parameters on 2 drum-driven paper charts with 12 recording pens. The
meteorological data were provided by a balance barometer, a bimetallic thermometer, a cup anemometer with wind vane, a psychrometer (wet/dry thermometer
hygrometer) and a pluviometer (rainfall amount/rate). Built in Rome by the instrument maker E. Brassart, the mechanism contained 11 telegraph transmitters, 6
counting mechanisms, a pendulum clock by Detouche of Paris and countless levers,
pulleys and weights. The complexity of the meteorograph can be gathered by contemporary accounts (Brassart 1872) and the explanation provided by Paolo Brenni
after the instrument’s cleaning and overhaul at the Museo di Storia della Scienza in
Florence (Brenni 1993). Due to its high cost and complexity, not many of Secchi’s
instruments were ever made (Brenni, Chap. 11 in this volume).
8 Angelo Secchi, Instrument Innovator