Clocks around Rome, Part I


I like clocks, and in planning “How can we cram relaxingly fit many interesting things into just a few days?” I found out that there were a lot of really interesting clocks around Rome.  With very sore feet we managed to see most of them.  In chronological order (heh heh):

This is the Sundial of Augustus.  It’s an obelisk that was originally erected by Psammetichus II (aka Psamtik II) in the sixth-century BCE in the city of Heliopolis by the Nile Delta, but was taken to Rome by Augustus (aka Gaius Julius Caesar Augustus aka Octavian) in 10 BCE, where it became the gnoman (stick-thingy) if a GIGANTIC sundial.

This particular photo was taken (and placed into public domain) by someone named Arpingstone, and it’s much better than any we could have taken, particularly because it was dark when we went to this obelisk.   Which would have been a terrible shame if it were still a working sundial, but it isn’t.  I mean, it still casts a shadow, but I’m not sure if this is the spot it was originally placed on (it fell down for a few centuries); more significantly, the original lines for the sundial, which might have looked like this 19th century painting

but might have just been a meridian [marking noon], seem to be under buildings and stuff.  Rome just doesn’t look like that painting anymroe — it’s a lot more crowded.  So this is only part of a sundial, but it’s still pretty impressive.  (References:  this official sounding page and this Wikipedia article).

Jump forward about 1500 years.  The Baths of Diocletian were built about 1700 years ago and used for over 200 years; part of the remains of the frigidarium (the cold water part of the baths) were turned into Santa Maria degli Angeli e dei Martiri thanks in large part to Michelangelo.  According to Wikipedia,

At the beginning of the eighteenth century, Pope Clement XI commissioned the astronomer, mathematician, archaeologist, historian and philosopher Francesco Bianchini to build a meridian line, a sort of sundial, within the basilica. Completed in 1702, the object had a threefold purpose: the pope wanted to check the accuracy of the Gregorian reformation of the calendar, to produce a tool to exactly predict Easter, and, not least, to give Rome a meridian line as important as the one Giovanni Domenico Cassini had recently built in Bologna’s cathedral, San Petronio.

Here’s a picture from 1703 of how the whole thing would work, from Bianchini’s De nummo:

And this is how the left-hand side of that picture now looks:

See that hole in the wall in the upper right?  Here’s a close-up:

This lets the sunshine in, and there’s a cut in the cornice so that the light shines on the floor.  This is on the floor:

It’s a meridian, and I think the sunlight is supposed to strike it at noon, with “noon” referring to whatever time the sun is as high as it’s going to get that day.  But we were there around noon clock-wise and I looked for sunlight and couldn’t find it.  (In this picture, though, it almost looks like there is some light near the meridian.  It’d be really cool if that was the missing sunlight, but it might just be candles.)

Here’s a diagram that explains it all (click for a larger version).  It’s all in Italian, though.

There was more on the floor — concentric ovals which might have had something to do with Easter, and another meridian-looking thing that was raised in a display box held up by feet:

Despite feeling a little unsure about the details, it was pretty neat to see this sundial.  I’d read about it in this article and was glad to see it in person.

This meridian, by the way, served as an official timekeeper for about a hundred and fifty years.  After that mid-day was marked by another sundial and a cannon fired at noon from the Castel de Sant’Angelo, a tradition that is kept up even today in the form of a cannon fired at noon from the top of the Janiculum Hill.

More clocks coming up!


2 Responses to “Clocks around Rome, Part I”

  1. Consumer Review Says:

    Fascinating article! I also love clocks and sun dials – so interesting!
    Thank you!

  2. Erin Says:

    It would not have dawned on me to plan a tour of sundials while in Rome but what a great idea! I think the one at Basilica of St. Mary of the Angels and the Martyrs looks most intriguing. Maybe it’s the blend of the incredible architecture of the church with the in-floor meridian. I’d love to see that one in person! Beautiful pictures. Thanks for sharing!

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