Mechanical Equinoctial Sundial
notes: label: Description
content: This brass universal mechanical equinoctial sundial rests on three legs, two with levelling screws. The third leg contains a latitude arc which is calibrated from 20 to 90 by 10 degrees, with line marks for each degree. The markings are crudely done; a mark for "10" was also scratched in after the arc was manufactured. The arc can be set for the proper latitude with a screw. The arc moves through a slot in an octagonal brass plate which contains an inset compass lettered for 4 cardinal points: P, T, L, M. The compass is calibrated from 0 to 90 x 4 with crude hash marks for every 2.5 degrees. A dragon and potted plant are engraved on either side of the compass. The base plate also contains a hinged piece which would have held a levelling bob. The latitude arc is fastened to a round, hinged hour plate which folds up from the octagonal plate containing the compass. The hour plate is calibrated from I to XII x 2 by I. The circumference is cut with teeth meshing into a brass minute dial on the alidade which also supports the gnomon. The geared mechanism of the minute dial is what makes this object "mechanical"; it magnifies the slight movement of the alidade so that the dial may be read to the minute rather than just to the quarter-hour. This dial may be Italian, in which case the cardinal points would represent 4 of the 8 Mediterranean winds (Ponente, Tramontan, Lebechio, and Mastro), and dates to the mid-1700s.
label: Location
content: Currently not on view
topic: label: Subject
content: Mathematics
label: Subject
content: Timekeeping
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Science & Mathematics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MA.320150
label: catalog number
content: 320150
label: accession number
content: 241222
objectType: label: Object Name
content: sundial, equinoctial
physicalDescription: label: Measurements
content: overall, closed: 8 cm x 12 cm x 14.5 cm; 3 5/32 in x 4 23/32 in x 5 23/32 in