National Association of Watch and Clock Collectors, Inc.
Horological Science Chapter #161
Horological Science Newsletter
Issue 1999-5 December 1999
Bob Holmström, Editor, Phone: 503-292-3685, <firstname.lastname@example.org>
Bill Givens, Sec. &: Publisher, 3850 Ashford Dr., Eugene, OR 97405 Phone (H): 541-465-9311 <Lbanks@ix.netcom.com>
Everett Jones, Treas., 11929 East Hill Drive, Chesterland OH 44026 Phone: 440-729-4811
Ernie Martt, Founding Editor, Phone: 440-247-6712, Phone: 440-247-6712 <email@example.com>
This issue is devoted primarily to circular error correction devices. Quite by accident, several authors
submitted articles that addressed this topic. I have chosen to collect them into a single issue and add
supplemental material relating to other attempts at "isochronal correction." Considerable creativity
has gone into invention of circular error correction devices but few examples of working devices exist.
It has been said that all of them involve the attachment of springs or small mechanisms to the pendulum
and that in every case, such devices would introduce greater errors into the going of a good clock than
the errors they are supposed to eliminate. [Haag, J. Annales Francaises de Chronometrie - Vol 3 (1933)
p. 255-92] That has not, however, stopped horologists from proposing and testing correction devices!
Occasional issues of HSN that focus on a single topic may occur again in the future - I propose an issue
devoted to temperature correction devices and results for HSN 2000-3 - please contact me if you are interested
in contributing material for this issue.
1 Index of this issue.
2 - 5 Introduction and summary of references to circular error correction devices by Bob Holmstrom
6 - 12 Bulle Isochronism Spring by N.R. Heckenberg
13 - 15 Notes on Isochronous Pendulums by Robert Katsma
16 - 19 The Period of a Cycloidal Pendulum with Rotation Proportional to Displacement by Robert Katsma
20 - 28 Circular Error and its Reduction by the Use of Permanent Magnets by Malcolm Pipes
29 - 31 Isochronous pendulum length by E. F. Wale
32 Erratum on compound cycloidal pendulum + Postscript on Aesculus Hippocastanum by Philip Woodward
Above: Drawing from Apians Cosmographicus Liber of 1533, showing how a nocturnal is used to tell the
time at night from the Great Bear.
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