The Keystone Arch

"The Romans were the first builders in Europe, perhaps the first in the world, fully to appreciate the advantages of the arch, the vault and the dome." This statement, attributed to D.S. Robertson, author of Greek and Roman Architecture, 2nd edn., Cambridge 1943, p.231, is cited in Wikipedia's entry entitled "Arch."

Note, in this quotation, the correct use of an un-split infinitive, "fully to appreciate." Colloquially we may say, "to fully appreciate," but, if we have old-school training ("never split an infinitive"), we remember, somewhere in the back of our mind, that this usage is often seen as incorrect.

So, moving on.

A post-and-beam span, that is, an opening framed by two posts with a beam across the top, supports itself by distributing the weight of gravity from the center of the beam to the two sides and down the posts.

The keystone arch cannot support itself until the keystone, the wedge-shaped puzzle piece at the apex, is put into place. The arch is first built on top of a framework, called a "centering." The centering is removed when the arch becomes a true compression form with the placement of the keystone.

The arch supports itself by distributing the weight of gravity from the wedge-shaped keystone to the next wedge-shaped voussoir and the next, on down to the springers at the spring line. The spring line is defined by the two points at the base of the arch and the theoretical center point, "drawn" from the two lower points of the keystone and crossing at the spring line. The springers have trapezoidal tops and level bottoms to continue spreading the weight of gravity down the posts.

We have an example of an early keystone arch in the northern gate, one of seven, in the walls encircling Perugia, the capitol city of Umbria. The walls were built of limestone block between 600 and 300 BCE to protect the city from the enemy, Rome, about a hundred miles away.

The original settlers of Perugia, or in Latin, Perusia, were the Umbri, an ancient--and perhaps the most ancient--tribe in Italy.  They spoke Umbrian, an Italic language related to Latin and Oscan. But their neighbors in Etruria, the Etruscans, spoke an unrelated language, which some scholars now believe may be a Tyrsenian language like the Raetic language of the Alps and the Lemnian language of Lemnos.

By the time the Roman general Fabius Maximus Rullianus led a successful expedition against Perugia in 310 or 309 BCE, the Umbrians had intermingled with the Etruscans and Perugia counted itself as one of the twelve cities of the Etruscan League. According to Livy, our source in this matter, the Perugians lost the battle and were accorded a thirty-year truce with Rome.

In a rebellious move, Perugia took part in the Second Samnite War against Rome in 295 BCE and had to renegotiate the treaty. By 216 and 205 BCE, the city found it prudent to help Rome in the Second Punic War.

Then the city fell a third time, when Mark Antony's younger brother and supporter Lucius sought refuge there in 40 BCE. Octavian, the future emperor Augustus, besieged the city and Lucius was compelled to surrender. The city was burned to the ground, but, based on archaeological evidence, rebuilding began almost immediately.

Soon thereafter, as part of a public-works program, Octavian repaired the wall and the ancient northern gate of Perugia, whose Umbrian or Etruscan name, as far as I can tell, we do not know. He rebuilt the keystone arch that the Perugians had originally built and this gate soon became known as the Augustan Gate, Porta d'Augusta.

So, as they often did, the Romans adopted the keystone arch from the people they conquered and used it widely in bridges and aqueducts, triumphal arches and gates, vaults and domes.

Gloucester

I went for a walk in my neighborhood a few days ago and it started to drizzle on the way back. Just the sort of weather to make me think of the word moisty, as in one of my favorite nursery rhymes:

The Old Man of Gloucester
One misty moisty morning,
When cloudy was the weather,
I chanced to meet an old man,
Clothed all in leather.
He began to compliment
And I began to grin.
How do you do? And how do you do?
And how do you do again?

I thought, "Maybe there's a post in the word moisty." Was that a word that English-speaking people use outside of nursery rhymes, I wondered. According to the Urban Dictionary, the word has acquired a vulgar meaning, a moisty being the feminine version of boner.

Now, if you are comfortable using moisty or boner in casual conversation and informal writing, good. But I am not.

So, moving on . . . .

"Maybe there's a post in Gloucester." One time I read that British towns whose names end in caster, like Lancaster, chester, like Winchester, cester, like Worcester, were originally Roman camp towns.

Through hundreds of years of fielding armies and occupying countries, the Romans had developed an almost unassailable plan for the castrum or fortified camp. The soldiers lived in the camp when they were not marching or fighting; on occasion, they retreated to it to save their skins. So when they occupied Britain, or Provincia Britannia, from 43 to 409 CE, they built many such camps to accommodate the men, and these became towns and cities.

For a legion of 5000 to 6000 soldiers, officers experienced in camp construction would lay out a square 450 to 550 feet on each side, with headquarters (the praetorium) in the middle. They would supervise digging a trench around the perimeter, raising the wall, and laying the criss-cross of roads with gates at each end of camp. On the road, every soldier marched with his palus, or fence-post, which became part of the palisade around the top of the wall. The camp was complete in six hours at most, and could be built, if necessary, while the legion was under attack.

Gloucester (pronounced "gloster") became a market center in about 48 CE and a Roman colonia, or retirement center, in 97 CE. The Roman word glevum (the first part of Gloucester) means
bright place or caer glow in Celtic.

Layout of a Roman camp.

Kastell Theilenhofen Iciniacum (English). CC BY-SA 3.0. Mediatus.

Queen Anne's Lace

The lacy flower head of Queen Anne's Lace is called an umbel, from Latin umbella (ae), parasol; the word is a diminutive form of umbra (ae), shadow or shade.

Each umbel has about thirty tiny white flowers in a flattened round, and sometimes the umbel has a purple center flower. The white flower bears two seeds and one fruit each: The flat inner sides of the seeds are stuck together until they are dry enough to separate, and the rounded outer sides are covered in burrs. The purple flower is sterile.

As the flower head dries, its stems close in on themselves like a parasol, eventually to let go of the parent plant and fly away. Seeds drop during flight or after landing, and some are carried even farther away by animals whose feather or fur picks up the burrs. So, nearly a failsafe system for making sure that seeds have a chance to find new ground.

Here's the kicker, though, and I was not ready for this. Nobody knows why some umbels have a central purple flower and some do not, and nobody knows why the purple flower is sterile.

Do you know about eol, Encyclopedia of Life? The purpose of which is to provide information about, and pictures of, every kind of life on the planet, all in one database. Eol is a wonderful resource for projects like this.

The word umbel was known to my old-lady Latin teacher through its use in Martial and Juvenal. Evidently the first use of the word umbel in English is in dispute, but the earliest reference seems to date to 1590.