Hemisferium Nocturnal and Tide computerThis piece is a replica of a Nocturnal and Tidal Abacus from 1570, signed by Humphrey Cole, an English maker of scientific instruments and engraver. Currently, this instrument can be found in the British Museum, London. One of its faces is a Tidal Abacus and the other is a Nocturnal. The Nocturnal was used to keep time at night. By observing the stars, it was noted that certain boreal constellations rotated around the Pole Star as if a giant clock