I frequently walk the ground of Arlington National Cemetery, not only for the exercise but because it’s a place of beauty and peace and comfort. Nearly every visit includes a stop at the Tomb of the Unknown Soldier. Why does the date on the pediment on the front of Arlington Memorial Amphitheater correctly show the year it was built — 1915 — as MCMXV, but the cornerstone on the amphitheater’s tomb side shows the year as MDCCCCXV. The latter is incorrect, at least in currently accepted format, but it does indeed say 1915 — in a convoluted logic. Why the inconsistency?

Gary Young, Arlington

Answer Man is innumerate in all major numbering systems — Roman, Arabic, hexadecimal — and not so hot in Latin, either. So he consulted T. Corey Brennan, a professor of classics at Rutgers University.

“Your reader stumbled onto — not the most pressing story of all time, but a much larger story,” Brennan said.

Today we are going to blow the lid off a debate that raged in America’s newspapers at the turn of the 20th century. Well, “raged” might not be the right word. But it did simmer.

First, a refresher course. Some Roman numerals are easy: I is 1. V is 5. X is 10. C is 100. D is 500. M is 1,000.

You can denote other numbers in two different ways. You can add numbers, so that VIIII is 9. Or you can subtract, so that IX is 9.

“If a smaller number precedes a larger number, you subtract it,” Brennan said.

As the year 1900 approached, Americans got very excited. They were going to party like it was 1899. But some were troubled: How should they write 1900 in Roman numerals?

“That is the question that is puzzling the heads of a number of good people of Wichita and elsewhere during the last few weeks before the new year,” the Wichita Beacon in Kansas wrote in December 1899.

Some camps favored the additive route, rendering 1900 as MDCCCC: 1,000 + 500 + 100 + 100 + 100 + 100.

Others favored the subtractive method of MCM: 1,000 + (1,000 – 100).

“Everyone had an opinion,” Brennan said.

The world’s biggest consumer of Roman numerals — the Vatican — opted for MDCCCC. That’s what was put on Pope Leo XIII’s pronouncements. The publishers of the most popular Latin grammar book of the day, Allen and Greenough, did the same.

But, Brennan said: “There’s a modern convention of not having more than three of the same character in a row. That’s mostly from book publishing in the 18th and 19th century.”

Boosters of MCM said it was more elegant than MDCCCC, especially in the way the second M hinted at the millennium to come.

The issue was known enough that in March 1900, a Pittsburgh bank placed a newspaper ad that read: "Which is right? MDCCCC or MCM? Send to us for correct ruling if you can't decide yourself — in the meantime save money and get 4 per cent annual interest compounded semi-annually." Said Brennan, "I don't know if you would call it a meme, but it was a thing."

Armed with this knowledge, let’s head over to Arlington National Cemetery on Oct. 13, 1915, when President Woodrow Wilson laid the cornerstone for the Memorial Amphitheater. Chiseled into the block was MDCCCCXV.

This, Brennan said, “immediately got the pedants out.”

These nitpickers included Daniel O’C. Callaghan, who after attending the ceremony penned a letter to the Washington Evening Star. “I looked at the stone and noted the carved date was expressed inaccurately,” he wrote. “I suggest that it should be MCMXV.”

It was several years before the Memorial Amphitheater was completed. And when it was, the pediment bore the inscription MCMXV. Brennan thinks the architects may have seen this as an opportunity to fix the clunky date on the cornerstone.

Answer Man had another thought. Both inscriptions are preceded by “ANNO DOMINI,” Latin for “the year of our Lord.” On the cornerstone, those words are above the date. On the pediment, they are on the same line as the date. Perhaps the designers thought a longer construction would look more balanced on the cornerstone:

ANNO DOMINI

MDCCCCXV

As opposed to:

ANNO DOMINI

MCMXV

And that seems to be the case. The cemetery unearthed an old memo that reads, “[It] would appear quite probable that the architects of the structure, the firm of Carrere & Hastings, believed the longer combination of Roman numerals would present a more aesthetic appearance on the face of the cornerstone.”

Brennan’s next book — due next year from Oxford University Press — is about another common feature of Roman architecture: fasces, those bundled rods that became a symbol of fascism.

We may never know for sure about Arlington’s dueling 1915s. As for the Romans themselves, Brennan says they were “indifferent” to such matters.

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