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depth during a passage from Wallis Island to the Mulgraves, he prepared several
disks of different diameter and color. Cialdi invited the astronomer Secchi to participate in an expedition onboard of the corvette “Immacolata Concezione” under the
papal flag and conduct a scientific program of clarity measurements in the
Tyrrhenian Sea.
The results from these experiments were first published in the abovementioned
brief report of Cialdi and Secchi (1865). In the same year, Secchi published a more
extended chapter in the Italian scientific journal Il Nuovo Cimento (Secchi 1865). A
year later, the same chapter was also published in Cialdi’s book Sul Moto Ondoso
del Mare (Secchi 1866). Over 32 pages, Secchi described every aspect of using a
disk to measure the clarity of the sea. He investigated dependencies on the disk’s
Fig. 13.2 Around 1864 the Jesuit scientist and astronomer at the Collegio Romano Observatory,
Angelo Secchi, and the commander of the papal steam corvette “Immacolata Concezione,”
Alessandro Cialdi, sailed the Tyrrhenian Sea near Civitavecchia to investigate different methods to
determine the transparency of the sea. (Note the misidentification in this figure of Father Secchi as
“Pietro,” a common confusion of the “P.” for “Pater” used for Fr. Secchi). (Courtesy of M. Wernand)
13 The History and Future of the Secchi Disk
depth during a passage from Wallis Island to the Mulgraves, he prepared several
disks of different diameter and color. Cialdi invited the astronomer Secchi to participate in an expedition onboard of the corvette “Immacolata Concezione” under the
papal flag and conduct a scientific program of clarity measurements in the
Tyrrhenian Sea.
The results from these experiments were first published in the abovementioned
brief report of Cialdi and Secchi (1865). In the same year, Secchi published a more
extended chapter in the Italian scientific journal Il Nuovo Cimento (Secchi 1865). A
year later, the same chapter was also published in Cialdi’s book Sul Moto Ondoso
del Mare (Secchi 1866). Over 32 pages, Secchi described every aspect of using a
disk to measure the clarity of the sea. He investigated dependencies on the disk’s
Fig. 13.2 Around 1864 the Jesuit scientist and astronomer at the Collegio Romano Observatory,
Angelo Secchi, and the commander of the papal steam corvette “Immacolata Concezione,”
Alessandro Cialdi, sailed the Tyrrhenian Sea near Civitavecchia to investigate different methods to
determine the transparency of the sea. (Note the misidentification in this figure of Father Secchi as
“Pietro,” a common confusion of the “P.” for “Pater” used for Fr. Secchi). (Courtesy of M. Wernand)
13 The History and Future of the Secchi Disk