Hemisferium Miniature Tide Computer With Stand

This piece is a replica of a Nocturnal and Tidal Abacus from 1570, designed 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 European Horologium Noctis was made in the mid-17th century and 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 hand were keeping time around a celestial sphere of 24 hours.

The abacus or tidal calculator is used to figure the time of the tides. The tides, with their constant change in the water level, greatly affect navigation both in harbours and for fishing. On this face, the outer circle is divided into 360 degrees with 1-degree intervals. The centre ring is divided into 12-hour sections, placed so that each quadrant moves in a clockwise direction. The interior is an exquisite compass rose with 32 directions.

The Miniature Tide Computer measures 130mm in height, 50mm across and 6mm thick.