Early thermometers could show that one day was warmer than another, but they could not be compared with each other. Ea tube he a slig different amo of liq, and s every ma had t be ma by ha, which meant that no two tubes agreed. The answer was to borrow two points that nature repeats: the temperature at which ice melts and the temperature at which water boils. Once those marks were settled, the distance between them could be divided the same way in every workshop.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.