Menu
412 of 520
Previousnext
FirstLast
Sorted by:
Instrument type
Maker
Place
Date
Overview
Details
 Catalogue


Proportional Instrument
Signed by James Kynvyn
Dated 1597; London
Brass; 310 mm in diameter

Circular brass plate with a suspension ring, and a degree scale on the edge 0 to 360, divided to 10, subdivided to 5, to 1, to 1/2 and to 1/4, numbered by 10. The central area is divided into four quadrants, two of which (90 to 180) have two sinecal quadrants whose sides have scales 0 to 40, divided to 5, subdivided to 1/2 with alternate hatching, numbered by 10. Dotted lines extend across the quadrant from the scales for every unit and continuous lines for every ten. The quadrant from 0 to 90 has parallel lines for every degree for a decreasing scale 0 to 90, numbered by 5, with every 5 line indicated by arrows; lines for only every 2 degrees are included between 70 and 80 and none between 80 and 90. It gives sines of angles for radii up to 200. A scale 0 to 200 on the left coincides with one on the pivoted index, divided to 10, subdivided to 2 and to 1, numbered by 10. The quadrant between 270 and 360 has a shadow square, the sides with scales 0 to 60 to 0, divided to 5, subdivided to 1, numbered by 5, and 0 to 12 to 0, divided to 3, numbered by 3.

The other arm of the counterchanged index, with shaped ends, has a scale 0 to 45, divided to 5, subdivided to 1/2 with alternate hatching, numbered by 5; this is for use with the sinecal quadrants. The index arm has two upright screws, and a shaped brass piece can be secured by two wing nuts. This may be the remains of a sighting device.

The remainder of the top face has decorative engraving of plants, dragons and an angel, and the signature: 'James Kenvyn fecit 1597'.

The underside has a socket for mounting on a tripod or staff, and is blank except for some practice engravings: 'Jacobu:', 'Iames' and (?)'Job'.

Jim Bennett

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 3174

© 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: http://www.mhs.ox.ac.uk/epact/catalogue.php?ENumber=43237

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