444 of 520
Sorted by:
Instrument type

Signed by Giovanni Battista Giusti
Dated 1568; Florence
Brass; 226 mm in radius

The limb of the instrument carries a scale of 90? reading to 1? by alternate hatched and unhatched divisions and numbered by groups of five in a separate scale with the 1? divisions indicated by dots. Above this the left side of the instrument is filled with the diagram for an Italian hours dial (9 to 23 without subdivisions) the morning hours being indicated by smooth lines, the afternoon hours by dotted lines. On each side of the diagram the two halves of an undivided zodiacal calendar are marked, and the remaining space at the right of the instrument carries the inscription 'QUADRANS: HORARIVM AD LATITVDINEM GRAD{I}: XXXXIII: M{INUTA} XL LINEA: PVNTORV{M}: POS{T} MERIDIES. LINEA SINE PVNTI ANT{E} MERIDIES' ('Horary quadrant for latitude 43? 40'; dotted line afternoon; smooth line morning'). Below this is a magic square of three, '4 9 2' / '3 5 7' / '8 1 6' which totals 15 in all directions and has a sum of three times itself, i.e. 45. In the apex of the instrument is a circular table labelled 'ROTA MEDII MOTVS SOLIS E QUANTITATIS DIEI' ('Wheel of the mean solar motion and the length of the day'). This consists of six concentric circles divided into sectors by radial divisions. The outer ring contains the names of the twelve signs of the zodiac indicated by their first two letters. The second ring supplies the month indicated by the first three letters of its name together with the corresponding time of noon in the Italian hours reckoning. The third and fourth rings read together supply the length of the day. The fifth ring contains the initials of eight wind directions and the innermost ring is blank. Two decoratively moulded block sights are set along the top edge of the instrument and there is a suspension hole for a thread cursor and runner at the centre/apex of the quadrant. The reverse of the instrument is engraved with a shadow square of 12 reading to half points and numbered in groups of three with the numbered divisions extended as full radial lines to the centre.

Anthony J. Turner

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 2520

© Istituto e Museo di Storia della Scienza, Firenze. All rights reserved. Information and images provided here may not be reproduced in any form or by any means without the prior written permission of the museum.

Basic URL:

|| Introduction || Essay || Museums || Bibliography || Conventions || Credits || Privacy || Help ||
|Catalogue entries |Handlist || Makers || Places || Articles || Glossary || Search || Home ||