In metric, one milliliter of water occupies one cubic centimeter, weighs one gram, and requires one calorie of energy to heat up by one degree centigrade—which is 1 percent of the difference between its freezing point and its boiling point. An amount of hydrogen weighing the same amount has exactly one mole of atoms in it. Whereas in the American system, the answer to ‘How much energy does it take to boil a room-temperature gallon of water?’ is ‘Go fuck yourself,’ because you can’t directly relate any of those quantities.

The ruins stretch from the river to the base of that mountain over there, about half a kilometre.’ ‘How far is that in regular measurements?’ Percy asked. Frank rolled his eyes. ‘That is a regular measurement in Canada and the rest of the world. Only you Americans –’ ‘About five or six football fields,’ Hazel interceded, feeding Arion a big chunk of gold. Percy spread his hands. ‘That’s all you needed to say.