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Horizontal Dial
Attributed to Carlo Plato
Dated 1578; Rome
Gilt brass; 125 mm in diameter

The dial is double sided and has a reversible compass (needle missing), pivoted at the centre, with a sixteen point wind-rose engraved on the hemispherical surface of the box, eight directions being named by their initials.

Side 1: The edge of the instrument is marked with a wind rose of 16 named points, the cardinal points being written in upper case, the intermediate points in smaller upper case and the subdivisions of these in upper and lower case. Within this ring is the inscription and within this symmetrically disposed around the compass are four pin-gnomon dials each named for 'Hor? Itali?, sive ab occasu' (Italian hours, or hours from sunset); 'Hor? Astronomic? ('astronomical hours', i.e. equal hours counted from midnight); 'Hor? Planetari? sive i{n} a?q{ua}les' ('planetary or unequal hours'); 'Hor? Bohemic?, sive ab ortu' ('Bohemian hours, or from sunrise'). The Italian and astronomical hour scales are drawn slightly larger than the other two

Side 2: The edge of the instrument is marked with a wind-rose similar to that on side 1. Disposed in the same way as on side one are four further dials labelled 'Horologiu(m) Italicum Latitudo 42 Gradu{u}m' ('Italian hours for 42?'); 'Horologiu{m} Italicum Latitudo 45 Gradu{u}m' ('Italian hours for 45?'); 'Horolo{ogium} Astronomicu{m} Latitudo 42. Gra{duum}' ('Equal hours for 42?'); 'Horolo{ogium} Astronomicum{m} Latitudo 45. Gra{duum}' ('Equal hours for 45?').

On either side of the dial for Italian hours at 42?, 'Rom? 1578' is repeated.

This dial has close resemblances with a rectangular quadruple horizontal pin-gnomon dial signed by Carolus Platus at Rome in 1593. The general layout of the two instruments with four small dials on each side of the plate, a common pivoting compass, compass points and wind-directions written around the edge of the plate with the cardinal points in upper case letters, intermediary points in upper and lower case or in a smaller upper case, is similar. There are also some more specific points of resemblance. The right hand minim of several of the capital H's on both dials is treated in curved form like that of a capital C; flourishes in the script are generally few; a characteristic decoration, in the middle of wind and compass-direction names consisting of a bisected triangle one half of which is hatched, is common to the two instruments. That they derive from the same workshop seems not unlikely.

Anthony J. Turner

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 246

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