The gilt dial is incised throughout with figures and inscriptions in engraving of the very finest quality, as is evidenced in the illustrations. The frontispiece is surmounted at its center by the crowned double eagle of the House of Hapsburg, indicating the identity of the sovereign in whose reign it was made, Emperor Francis I or the Empress Maria Theresa of Austria. Below the eagle at either side are flying cherubs supporting ribands with inscriptions. Centered at the bottom of the frontispiece immediately above the chapter rings is the moving silvered orb representing the sun. Surrounding it is a tableau of the Holy Trinity, with the Virgin Mary being crowned by Christ holding a cross at the left and God with a sword in hand at the right, and a dove representing the Holy Spirit hovering over the Virgin's head. Father S. X. Winters, S.J., considers it reminiscent of the triptych "The Coronation of the Virgin" by Fra Lippo Lippi. [Illustration: Figure 10.--DIAGRAM OF the dial plate.] [Illustration: Figure 11.--DIAL PLATE of the Borghesi clock.] KEY TO DIAGRAM OF THE DIAL PLATE A Dominating planet, represented by its symbol and its house; B Dominical letter (Lit. Dom.); C Epacts (Cyc. EpEC); D Roman indiction (Ind. Rom.), part of the reckoning of the Julian period; E Solar cycle, (Cyc. Sol.), part of the reckoning for the Julian period; F Golden number (Num. Aur.), part of the reckoning for the Julian period; G, H, I, J The era, or the current year; part of the six windows of the Iris, or rainbow; K Shuttered winding hole, for winding up the weights; part of the six windows of the Iris; L The era, or the month of the current year; part of the Iris, or six windows of the rainbow; M The sun in its epicycle; N The 12 signs of the sun's anomaly; O, P The first chapter ring representing the equatorial globe of the week, revolving from left to right; Q The coming day indicated through the window; R The second chapter ring; including the synodic-periodic measure of the tides, the days of the median lunar-synodic age, the signs and degrees of the signs for mean distance of the moon from the sun; S Epicycle of the moon with signs of its anomaly; T Head of the dragon (Cap. Draconis); U Tail of the dragon (Cauda Draconis), for measuring eclipses of the earth and of the moon; V Third chapter ring, with degrees of lunar latitude and some fixed stars; W Fourth chapter ring, showing firmament of fixed stars, signs of the zodiac and degrees of the signs, the months of the year, and days of the months, revolving left to right for the course of a mean astronomical year; X Adjustment marked _Claudit_ (it closes) and _Aperit_ (it opens) for disengaging dial work for the purpose of making astronomical experiments and computations; Y Adjustment marked _Concitat_ (it accelerates) and _Retardit_ (it retards) for fast and slow adjustments of the movement.