Navicula de Venetiis for latitudes 20°-65° North. The main body of this instrument is topped by a castellated poop and forecastle and a mast. Its obverse side is inscribed with vertical hour-lines and there is a declination scale at the bottom of the instrument for setting the mast. The right-hand side carries an arced declination scale for the bead. On the reverse side, the left-hand quadrant contains a shadow square, the right-hand quadrant a degree scale. There is also a set of unequal hour lines for reading the planetary hours between sunrise and sunset. The 'mast' rule passes through the main body of the ship and is pivoted by a rivet at the centre of curvature of the instrument. A line down the centre of the part of the mast that extends below the ship is used to set the declination. The obverse side of the mast carries a latitude scale and the reverse side displays a list of towns and cities in England and their latitudes.

The navicula de Venetiis, or 'little ship of Venice', is a very rare form of sundial. It was developed in Europe in the Middle Ages, though it is possible that its origins were Arabic. This navicula is in remarkably good condition, suggesting that it was lost shortly after it was made. The castellations are not merely decoration (reminiscent of the form of mid-15th century ships), but also carry the pinhole sights for taking the sun's altitude. The shadow square on the reverse side is used, in conjunction with the sights, for taking altitudes for surveying.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.