The instrument, made entirely of brass on a
square wooden base (17 x 17 cm) with four levelling screws, is essentially
an equatorial solar quadrant (or solar clock) made up of the following
parts:
§ a magnetic compass enclosed in the base which can be freely rotated with respect to a circular dial subdivided into four quadrants, each graduated from 0 to 90;
§ a circular quadrant supported by a staff fixed to the base, with a joint that may be blocked and which allows the quadrant to be inclined from 0 to 90 degrees with respect to the base; the quadrant is ideally subdivided clockwise into 24 hours (each division representing 4 minutes), but in reality the subdivision is in the interval from hour III to hour XII and from hour 0 to hour IX, which corresponds to the maximum duration of the day at latitudes in the temperate zones;
