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: photos by Marco Prins and Jona Lendering © |
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Horologium Augusti
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Unless
otherwise indicated, pictures on this page © Marco Prins and Jona
Lendering. Photos can be downloaded and used for non-commercial purposes,
but you have to acknowledge Livius. |
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One of the most remarkable monuments in imperial Rome is the Horologium
Augusti, a giant sundial, using as its gnomon an obelisk that was originally
made by a pharaoh
named Psammetichus
II (Neferibra Psamtik, 595-589). It was created by the emperor
Augustus,
who had conquered Egypt and had seized the monolith in Heliopolis. The
obelisk, 21.79 meters high, is now standing in front of the Italian parliament
and is again used as a sundial (a line in the pavement indicates the date).
The monument is described by Pliny
the Elder: |
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Augustus used the obelisk in the Field of Mars in a remarkable
way - namely to cast a shadow and thus mark the length of days and nights.
A paved area was laid out commensurate with the height of the monolith
in such a way that the shadow at noon on the shortest day might extend
to the edge of the paving. As the shadow grew shorter and longer again,
it was measured by bronze rods fixed in the paving. This device deserves
study; it was the result of a brainwave of Facundus Novius.
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The laws of physics can not be suspended and because we know the place
where the obelisk originally stood, it is a matter of mathematics to establish
where the original pavement with the network of bronze rods must have been.
In 1976, the German archaeologist Edmund Buchner predicted the exact location
of the pavement. Three years later, he found what he had been looking for
in the cellar of a cafeteria in the Via di Campo Marzio. |
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The Horologium Augusti is, of course, shown on the famous model of
ancient Rome in the Museo Nazionale della Civiltà Romana (Rome EUR).
On this picture, you can see it close to the upper edge. The small square
building in the upper left corner is Augustus' Altar of Peace (Ara Pacis).
On the date of the emperor's birth, the shadow of the obelisk indicated
the sanctuary. A line at right angle of this shadow would cross through
the center of the Mausoleum
of Augustus, the big round structure at the lower edge.
A satellite photo can be found here.
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