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Arithmetic, Roman Style

Since the first century BCE, calculations were performed with  calculi, the Latin word for pebbles. For a hundred years before Miriam’s time, arithmetic was done by sliding pebbles, and eventually grooved beads, along numbered slots. The Romans developed this base-10 abacus from a more complicated version used by the Greeks and Babylonians. Calculations were done in a decimal system, and only when the answer was achieved, was it written in Roman numerals. And so, engineers, merchants, businessmen, bankers, moneychangers, and tax collectors had a quick way to perform basic operations including finding the cube root of a number.


Through Miriam, we learn that there were two models of this counting board. In The Deadliest Lie, we see that her father, an investor in mortgages, used a table model:


My father was studying the accounts he held with Amram, his brow pulled down in concentration, his index finger sliding down a column of numbers, his bronze pen borrowing its glitter from a stripe of sunlight. Standing next to his desk was his abacus, an antique marble-topped table marked with parallel lines.


In “The Fire”, a story in The Deadliest Deceptions, we learn that a glassblower used a portable version to run his business:


I followed him into a cave-like room, dim, low-raftered, and with a faint fecal odor I traced to a chamber pot. A sputtering oil lamp atop an iron stand spread a yellowish skin on two low stools, their seats stained with grease, and a narrow wooden table, its surface splintered and darkened with age. Floor-to-ceiling cubbyholes mounted on the back wall held the usual items: scrolls, oil lamps, an abacus, and writing supplies.


The Miriam bat Isaac Mysteries have been praised for their historical accuracy.  You can immerse yourself in an engaging story and at the same time, absorb the technology of the day. To choose one of the several books,


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