Inventory no. 54358 - Former Display Label
NAVICULA DE VENETIIS, or SHIP DIAL, of unknown origin.
?c1450.
Brass. Unsigned and undated.
This instrument is, in principle, similar to the Regiomontanus dial. On the 'mast' of the 'ship' is the latitude-scale on which is set the slide from which hangs the plumb-line. The 'mast' is tilted until its projecting end, at the bottom of the instrument, lies against the correct part of the Zodiac-scale. The thread of the plumb-line is then held against the same relative position in the second Zodiac scale, on the right-hand side of the instrument, and the bead which slides on the thread moved to that position. The sights of the instrument (in the castellated 'poop' and 'forecastle' of the 'ship') are directed towards the sun, and the plumb-line allowed to hang freely, when the bead will indicate the time on the hour-lines on the 'hull' of the 'ship'.
The reverse side of the hull is engraved with a shadow-square, similar to those on astrolabes, and unequal hour quadrant, for finding the time in unequal (or planetary) hours.
There is a ?14th century description of the construction of an instrument of this type in MS Bodley 68. The construction is also fully described, together with the method of use, and the instrument illustrated in Opere di Orontio Fineo del Delfinato ... tradotte da Cosino Bartoli ... (Venice, 1670), pp. 521-5.
[G. 73]
Lewis Evans Collection.