SEVENTEENTH CENTURY ITALIAN GRAPHOMETER WITH CENTRAL SUNDIAL, constructed of sturdy brass, 16-9/16″ (42 cm) in overall width. This surveying graphometer has a mainplate with a large semicircular arc divided every half-degree and numbered every 5°; we note distinctive early hand-engraved numeral shapes, especially the 5’s. The plate is mounted with two small fixed sight vanes, and carries a rotating alidade which reads against the scale and which has its own pair of small vertical-slit vanes. This alidade is engraved with a lovely central four-lobed rose and terminal “leaves.” The plate has cruciform supporters to the 4-3/8″ (11 cm) diameter circular sundial and glazed compass. This horizontal dial is ruled and numbered every hour from 5am to 7pm, and is engraved for latitude 43° North. The thin gnomon is removable with pin feet. The compass itself has a 32-point rose on brass, with circumferential scale divided every 2° and punch-numbered every 10°, and is engraved with four directionals of a fleur-de-lys (for North), a cross (East), “M” (for Mezzodi, South), and “P” (Ponente, West). Condition is good, noting some very old minor repairs / reinforcements to the frame. Threaded holes either side of the compass probably allowed use with a staff mount, now lost.

This is a very early example of a graphometer, the classic Continental surveying instrument invented by Philippe Danfrie in the late 16th century. The use of a central sundial is known on some other early surveying instruments (e.g., see the fine Metz circle with dial, Tesseract Catalogue 26, item 49). Note that the present instrument has neither transversals nor vernier interpolation, also that some of the brass members have edge outlining characteristic of the early date. Italian graphometers are particularly rare, this one consistent (at 43° latitude) with Umbria, Southern Tuscany, and Elba.