The Borghesi Astronomical Clock in the Museum of History and Technology: Contributions from the Museum of History and Technology, Paper 35Bedini, Silvio A.
History
The Borghesi Astronomical Clock in the Museum of History and Technology: Contributions from the Museum of History and Technology, Paper 35
Bedini, Silvio A.
Astronomical clocks
The next section of the central dial is inscribed
_Intumescite--Detumescite_ (rise and fall of the tides) repeated at
intervals of approximately every six hours. Within the next section is
the following inscription, inscribed continuously around the ring:
Lege fluunt, refluunt, dormitant hac maris undae: Ad Phoebi et
Phoebes concordia iussa moventur Aequora; discordi iussu
suspensa quiescunt.
Translated, this is:
By this law the sea waves ebb and flow and lie dormant: When
Phoebus and Diana agree in their commands, the waters are
moved; when they disagree, the waters lie silent.[16]
Within the central boss of the dial plate, the name of the maker is
inscribed:
Bvrghesio Doctore, et Bertolla Limatore Annaniensibvs*
Translated, this is:
[By] Doctor Borghesi and Bertolla, mechanician citizens of
Anauni.
INDICATORS IN THE FRONTISPIECE
There are 12 windows in the frontispiece, through each of which appears
an indication relating to time. Beginning at the top of the frontispiece
of the dial, the first opening occurs on the breast of the imperial
eagle. This indicates the dominating planet, represented by its symbol,
and its house.
The opening in the eagle's left claw, labeled "Lit. Dom." is the
dominical letter. The first seven days in the month of January are each
assigned one of the letters _a_ through _g_ in order of appearance. The
letter which coincides with the first Sunday within this period is
called the dominical letter, and it serves for the following year. In
leap year, two letters are required, one to February 29th and the letter
next proceeding for the remainder of the year. This letter is used in
connection with establishing the date of Easter Sunday. The date of
Easter regulates the dates of the other movable feasts.
The eagle's right claw is labeled "Cyc. EpEC" and represents the epact,
or the age of the moon on January 1st. It serves to find the moon's age
by indicating the number of days to be added to each lunar year in order
to complete a solar year. Twelve lunar months are nearly 11 days short
of the solar year, so that the new moons in one year fall 11 days
earlier than they did the preceding year. However, 30 days are deducted
as an intercalary month since the moon has made a revolution in that
time, and the remainder, 3, would be the epact.
Public-domain text, read in full here on John Shaqi.
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