LARGE UNIVERSAL RING DIAL ON STAND, English, c. 1725, signed "B. Scott, Londini Fecit." Constructed entirely of brass, the sundial is 8" (20 cm) in diameter, set in a semicircular frame 9-112" across, and with an overall height on stand of 13-3/4" (35 cm). The sundial sets up as an analogue of the earth. An inner equatorial ring swings out 90 degrees, and is divided on its upper and inner surfaces every 2 minutes of time over twice-12 hours. This ring is mounted to the vertical meridian ring, which is divided every half-degree of latitude 0 ± 90 (i.e., for North and South latitudes), and which rotates within the fixed outermost frame. The swiveling "polar axis" bridge carries a sliding pinhole, to be set against the date and zodiacal position scales (divided for the "old style" Julian calendar with vernal equinox 11 March) and the 0 ± 23-1/2° North/South solar declination scale. Thus the sundial is a standard form of large universal ring dial, except it is not necessary to dangle it vertically from a suspension ring; rather one levels the base with three leveling screws, then rotates the sundial assembly until the spot of sunlight falls on the hour ring. No magnetic compass is required, and it is useable anywhere in the world. Condition is fine, noting light wear and staining. The semicircular framework and its conical axle are all original, but the leveling base itself is an old replacement.
Benjamin Scott was a wonderful craftsman of mathematical instruments. He had apprentieed to none other than John Rowley, and numbered among his own apprenti ces Thomas Heath. Scott is recorded as working in London 1712 -1733, but then there is a gap and we find him in Russia, 1747 - 1751, as head of the St. Petersburg Academy of Sciences'