It is important as having been adopted by Regnault (and also by many subsequent calculators) for the expression of his observations on the vapour-pressures of steam and various other substances.
He had been in France in 1773, where he had not only the famous vision of Marie Antoinette at Versailles, "glittering like the morning star, full of life, and splendour and joy," but had also supped and discussed with some of the destroyers, the encyclopaedists, "the sophisters, economists and calculators."
They didn't have calculators in Victorian schools, but they did have the abacus!
They were starting to make good use of graphic calculators with some classes.
Some fancy calculators have a ` ` ^ ' ' key that does the same thing.
