496 of 520
Sorted by:
Instrument type

Signed by Petrus ab Aggere
Dated 1560; Toledo
Brass; 101 mm square

The simple theodolite has a square plate with an inscribed circle with four geometrical quadrant scales 0 to 12 to 0, divided to 3, subdivided to 1 and to 1/4 with alternate hatching, numbered by 3, and within this a degree scale 0 to 360, divided to 10, subdivided to 5 and to 1 with alternate hatching, numbered by 10. The corners outside the circle are marked 'A', 'B', 'C' and 'D'. Within the circle pivots a circular plate with four slit sights (one is missing) and four corresponding indexes for the two scales. The plate itself has a circular scale on its edge, 0 to 360, divided to 10, subdivided to 1, numbered by 10; a quadrant-shaped aperture in the plate reveals a scale of winds beneath, while on the solid part the degree divisions are continued in a radiating pattern to the centre. The wind scale is marked for eight named winds, each with a section divided into 16 parts by a circular scale, with alternate hatching, and the reading on this scale is given by an inward pointing index inside the quadrant aperture.

Signed on the reverse: 'Absoluit Toleti Petrus ab aggere Mathematicus Regius, anno dn 1560.'

Jim Bennett

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 1278

© 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 ||