Bob Holmström, Editor, Phone: 503-292-3685, <holmstro@europa.com>

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 <emartt@cyberdrive.net>

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.

Bob Holmström

Pages Contents

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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