258
15.5 Gnomonics and Archaeology
Angelo Secchi found a particular resonance in the study of the ancient sundials with
another of his interests, archeology: a cultural symbiosis that anticipated the methods of modern archaeoastronomy. Evidence of his commitment to this work can be
seen from a brief handwritten note concerning the Obelisk of Augustus and in particular from the mathematical illustration he made of the sundial of Emperor
Commodus (Altamore and Tuscano 2014).
35
The archaeological excavations of the time were uncovering ancient sundials
(among other things), and it was necessary to go back to first principles to interpret
how they worked. Sometimes, at the request of the museum institutions themselves,
astronomers who were cognizant of archaeological issues became involved in this
study. Ruggiero Boscovich had made a significant contribution to this topic; Secchi
refers to it briefly in his reflections on the gnomon of Campo Marzio
36
: (“(...) I find
Boscovich’s idea more probable, that the length of the days and nights were marked
by the lines and not by the numbers”) assuming that the inconsistencies of the markings “(...) could have come from the inaccuracy of the Julian rule (…)”.
37
If additional documents on this topic can be discovered, this may establish
whether Secchi had a wider interest of this issue, to be explored at some future time.
The Jesuit periodical Civiltà Cattolica of 1857 contains an article in the supplement on natural sciences about an ancient sundial, a gift of Cavaliere Luigi Vescovali
to the Kircher Museum.
38
The dial, which still exists, was reproduced at life-size
and consists of a disc circumscribed by a thin edge similar to a hollow cylinder. On
the contour band, you can see a slit for the passage of sunlight and the trace of a
weld with an original suspension ring that made the object usable as a portable
watch. On the back of the disc is engraved the effigy of the emperor Commodus
39,40
surrounded by the inscription M. COMMODUS. ANTONINUS. PIUS. Felix.
AUG. Brit. which thanks to the notation Britannicus allows one to infer that the
object dates from after 189 A.D. On the other side is engraved the drawing of a
sundial, which was accompanied by a small alidade, and the inscription ROME,
being the calculated path for a latitude of 42 degrees (Fig. 15.5).
35 APUG, Secchi Archive, 25.I - Note on the gnomon found in the excavations of Campomarzio (3 ff.)
36 “(Boscovich) scrisse dotte illustrazioni intorno all’ obelisco di Cesare Augusto e ad un orologio
solare trovato in un’antica villa scopertasi sul dosso del Tuscolo,” ([Boscovich] wrote learned
illustrations concerning Caesar Augustus’s obelisk and a sundial found in an old villa discovered
on the Tuscolo), Corniani G.B. – Ticozzi S., I secoli della Letteratura italiana, 1833.
37 “(…) stimo più probabile l’idea di Boscovich che la lunghezza dei giorni e delle notti vi fossero
indicate con le linee e non con i numeri (…) potevansi derivare dalla inesattezza della convenzione
giuliana (…)” APUG, Secchi Archive, 25.I - Nota sul gnomone trovato negli scavi di Campomarzio
(3 ff.). (Tuscano M.L. 2012a, Auber Alberi P.-Tuscano M.L. 2014).
38 Luigi Vescovali, a well-known scholar of Archeology, was a member of the Pontifical Roman
Academy of Archaeology.
39 The dial is currently kept in Rome in the Collection of the National Roman Museum.
40 Vitruvius in his treatise De Architectura names these instruments Viatoria pensilia».
M. L. Tuscano
15.5 Gnomonics and Archaeology
Angelo Secchi found a particular resonance in the study of the ancient sundials with
another of his interests, archeology: a cultural symbiosis that anticipated the methods of modern archaeoastronomy. Evidence of his commitment to this work can be
seen from a brief handwritten note concerning the Obelisk of Augustus and in particular from the mathematical illustration he made of the sundial of Emperor
Commodus (Altamore and Tuscano 2014).
35
The archaeological excavations of the time were uncovering ancient sundials
(among other things), and it was necessary to go back to first principles to interpret
how they worked. Sometimes, at the request of the museum institutions themselves,
astronomers who were cognizant of archaeological issues became involved in this
study. Ruggiero Boscovich had made a significant contribution to this topic; Secchi
refers to it briefly in his reflections on the gnomon of Campo Marzio
36
: (“(...) I find
Boscovich’s idea more probable, that the length of the days and nights were marked
by the lines and not by the numbers”) assuming that the inconsistencies of the markings “(...) could have come from the inaccuracy of the Julian rule (…)”.
37
If additional documents on this topic can be discovered, this may establish
whether Secchi had a wider interest of this issue, to be explored at some future time.
The Jesuit periodical Civiltà Cattolica of 1857 contains an article in the supplement on natural sciences about an ancient sundial, a gift of Cavaliere Luigi Vescovali
to the Kircher Museum.
38
The dial, which still exists, was reproduced at life-size
and consists of a disc circumscribed by a thin edge similar to a hollow cylinder. On
the contour band, you can see a slit for the passage of sunlight and the trace of a
weld with an original suspension ring that made the object usable as a portable
watch. On the back of the disc is engraved the effigy of the emperor Commodus
39,40
surrounded by the inscription M. COMMODUS. ANTONINUS. PIUS. Felix.
AUG. Brit. which thanks to the notation Britannicus allows one to infer that the
object dates from after 189 A.D. On the other side is engraved the drawing of a
sundial, which was accompanied by a small alidade, and the inscription ROME,
being the calculated path for a latitude of 42 degrees (Fig. 15.5).
35 APUG, Secchi Archive, 25.I - Note on the gnomon found in the excavations of Campomarzio (3 ff.)
36 “(Boscovich) scrisse dotte illustrazioni intorno all’ obelisco di Cesare Augusto e ad un orologio
solare trovato in un’antica villa scopertasi sul dosso del Tuscolo,” ([Boscovich] wrote learned
illustrations concerning Caesar Augustus’s obelisk and a sundial found in an old villa discovered
on the Tuscolo), Corniani G.B. – Ticozzi S., I secoli della Letteratura italiana, 1833.
37 “(…) stimo più probabile l’idea di Boscovich che la lunghezza dei giorni e delle notti vi fossero
indicate con le linee e non con i numeri (…) potevansi derivare dalla inesattezza della convenzione
giuliana (…)” APUG, Secchi Archive, 25.I - Nota sul gnomone trovato negli scavi di Campomarzio
(3 ff.). (Tuscano M.L. 2012a, Auber Alberi P.-Tuscano M.L. 2014).
38 Luigi Vescovali, a well-known scholar of Archeology, was a member of the Pontifical Roman
Academy of Archaeology.
39 The dial is currently kept in Rome in the Collection of the National Roman Museum.
40 Vitruvius in his treatise De Architectura names these instruments Viatoria pensilia».
M. L. Tuscano