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PREFACE
THIS BOOK was prepared for use as a home study course in horology and as a
reference work for the student in the horological schools. In its preparation, the
author has kept in mind the practical and theoretical knowledge required by
those organizations that prepare examinations and the state board examinations
of the several states which require a license to practice horology.
The author has consulted original sources and especially the works of those
who have made horological history. In addition, much of the work has been
drawn from scientific publications, particularly those concerned with the more
recent developments.
Most books on watch work give no space to the theoretical analysis. On this
point a departure has been made, and the reader will find that, in addition to the
practical treatment, there is a general survey of horological theory.
It is recognized that the practice of horology is largely one of manual skill,
the acquisition of a delicate touch, and muscular control of the wrist and fingers.
Practical work is, then, the starting point, and the material in this book is so
arranged. One must perform, at the outset, a satisfactory job of cleaning and
repairing a clock or watch before the more intricate work of isochronal, position,
and temperature adjusting can be achieved. When this plan of attaining a
horological education is followed, the student will find himself developing
progressively toward a successful career in a very interesting and pleasant
semiprofession.
HAROLD C. KELLY
263 May Avenue
Monrovia, California
CONTENTS
Preface
Introduction
Part I: PRACTICAL HOROLOGY
1. Introductory Remarks to Beginners
2. Practical Clock Repairing
3. Practical Watch Repairing
4. Repair and Adjustment Problems Taken From Practice
Part II: THE MECHANICS OF HOROLOGY
1. Wheel Work of Pendulum Clocks
2. Wheel Work of Balance Wheel Clocks and Watches
3. Gearing
4. Escapements for Pendulum Clocks
5. Escapements for Balance Wheel Timepieces
6. Striking Mechanisms
7. Automatic Watches
8. Stop Watches and Chronographs
9. Calendar Mechanisms
Part III: THEORETICAL HOROLOGY
1. A Study of the Pendulum
2. A Study of the Balance and Balance Spring
Bibliography
Index
INTRODUCTION
TIME AND TIME RECKONING
What is time? It is a something that has baffled thoughtful men since the
beginning of civilized history. Innumerable astronomers, mathematicians,
scientists, and philosophers have investigated this thing called time and have
advanced various theories and incidentally worked out systems by which it has
served mankind.
Old and New Concepts of Time
In 1687, when Sir Isaac Newton published his “Principia,” certain
philosophical concepts of time were given the world that have been accepted
even to this day. In fact the whole science of physics and mechanics is still based
upon these concepts and is so taught in our schools.
According to Newton, time is absolute and without any relation to bodies or
their motions. It is conceived as unbounded, continuous, unchangeable in the
order of its parts and divisible without end. Time exists without matter. If the
universe were destroyed, time and space would remain.
On the other hand Dr. Albert Einstein conceived a different idea of time.
Einstein said that time is relative. It cannot exist without being associated with
space. And since objects in space have three dimensions (length, breadth and
height), time is added to these, which gives all objects four dimensions.
Suppose, for example, we are in the capitol building in Washington today at
12:00 a.m. Returning there tomorrow at 12:00 a.m., the space will have changed.
The earth has rotated to the east on its axis; it has revolved to the east around the
sun; the sun has moved around the Milky Way. Thus when a given period of
time has returned, we cannot return to the same given space. Suppose, for
another example, the observer was placed on Mars or Venus. The unit value of
time would be different.
The dimensions of an object, its shape, the apparent space it occupies,
depend, according to Einstein, upon the object’s velocity — that is, upon the
time which the observer takes to travel a given distance, relative to the object.
Hence it is impossible to define space without time. That is why we now say that
the earth on which we live has four dimensions and that time is the fourth
dimension.*
* A very interesting and highly instructive discourse on Relativity is found in The Universe and Dr.
Einstein, Lincoln Barnett, William Sloane Associates, New York. Every horologist should read this book.
Thus the scientists have given us two widely divergent concepts of time. We
as horologists shall leave that to the scientists to discuss among themselves. Our
interest is concerned with obtaining the mean of solar time in order to set our
clocks and watches. This much we are certain: that man has invented a method
of dividing successive rotations of the earth on its axis, in relation to the sun,
into days, hours, minutes, and seconds for the purpose of regulating his daily
activities. The method by which time is reckoned will now be considered.
The Earth as a Clock
The earth is our master clock. The rotation on its axis may be regarded as
practically invariable. The friction of the tides on the ocean floor is said to slow
down the earth’s motion, but calculations show a retardation of less than a
second in 100,000 years.
To get a clear picture of the earth clock and how it works, let us suppose that
we can place ourselves in space directly above the north pole, say 250,000 miles
from the earth. From this position we may see the earth from the north pole
nearly to the equator. Figure 1 shows how it will appear. We may observe the
earth’s rotation to the east at the rate of 18½ miles a second. Further observation
shows that half of the earth is light and the other half is dark, and we may see the
sun’s rays creep over the north pole as the summer season approaches, and also
become darkened when winter comes.
Figure 1.
Our earth clock is to have a 24-hour dial with two sets of figures reading
from 1 to 12 to show a.m. and p.m. Meridians of longitude will provide for the
location of the figures. The meridians are 15 degrees apart and the prime
meridian, which passes through Greenwich, England, indicates 12 a.m.
Greenwich time. Our earth clock differs from ordinary clocks in that the “hour
hand,” which may be any meridian for local time, turns counterclockwise.
The equinoxes. Suppose we are observing the earth at 12 a.m. on March 21
or September 23. These dates are called the vernal and autumnal equinoxes and
indicate a period when both the sun and an imaginary location in the sky (the
equinoxes, Figure 2) fall on a given meridian at precisely the same time. During
the periods of the equinoxes, the equator lies on the plane of the sun’s rays, or, to
put it in another way: both poles are an equal distance from the center of the sun
and night and day are of equal length everywhere on the earth.
A sidereal day is shorter than a solar day. Now, at about 11:56 a.m., mean
solar time, on March 22 or September 24, the earth clock has made one complete
rotation on its axis and the above given meridian again lies on the plane of the
equinoxes. The duration of one rotation—that is, a rotation of 360 degrees —is
called a sidereal day. In the meantime, the earth, in its revolution around the sun,
has moved to a new position as shown in Figure 3. From this location it can be
seen that further rotation is required before a solar day is completed. Thus a solar
day is almost 4 minutes longer than a sidereal day.
Figure 2.
Figure 3. The arrows point toward the vernal equinox.
Sidereal time is determined by observing the more distant stars and is,
therefore, consistent, whereas apparent solar time is not. Sidereal time, however,
is not useful for civil purposes because our daily activities are governed by the
sun’s position in the sky. Sidereal noon, for example, comes at night during part
of the year and a sidereal year contains 366¼ days instead of the 365½ days of a
solar year.
Solar days are longest in December and January. Apparent solar days are
not uniform for two reasons. The first can be explained by noting that the earth’s
orbit is an ellipse and the sun is situated near to one end of the ellipse as shown
in Figure 4. When the earth is nearest the sun, which occurs about December 22,
its revolution around the sun is fastest and the days are longest because the earth
must rotate farther to bring a given meridian to solar noon.
The second reason why apparent solar days are not uniform has to do with
the inclination of the earth on its axis. During the latter parts of March and
September, the earth’s rotation to the east is less than any other time of the year,
since part of the motion, as observed at the equator, is south in March and north
in September. When the rotation is eastward as in the latter parts of December
and June, further rotation is required to complete a solar day. The solar days are,
therefore, longest in December and June and shortest in March and September.
Figure 4.
The effect of the eccentricity of the earth’s orbit and the inclination of the
earth’s axis, when combined, tends to increase the length of the solar day on
December 22. The effect of the two phenomena, separately and combined, is
shown in Table 1.
Mean time or civil time. For practical reasons, it is necessary to arrange the
