an article by John Ward
and Margaret Folkard
3 Bedford Street
The New Zealand Garden Journal (Journal of the Royal New Zealand
Institute of Horticulture), Vol. 1, No. 4, December 1996, pp. 16-19.
John Ward and Margaret
Folkard explore the history, use, and range of sundials available
today. The articles are based on their book, Sundials
Australia, the second edition was published in 1996.
1 Historical background to sundials
Most of us know of a
garden containing an old sundial tucked away in a corner, surrounded
by flowers, quietly telling the time. Sundials in one form or another
have been used by different societies for more than 5,000 years.
The Greek historian Herodotus (484-425 BC) stated in his writings
that sundials originated with the ancient Chaldeans and Sumerians
who lived in Babylonia between the Tigris and Euphrates rivers in
the region formerly called Mesopotamia and now known as Iraq (Gibbs
1976). They used vertical rods on their buildings as shadow casting
devices for telling the time and date, and were the first people
to divide the day into 24 hours, the week into 7 days, and the year
into twelve months (after first having divided the sky into the
12 signs of the zodiac.)
From these beginnings, methods for designing and constructing various
types of sundial have been developed by many different cultures
right through to the present day. Many articles have been written
about the history of sundials. However, a large number of them use
uncertain sources and are somewhat contradictory. Readers who are
interested in pursuing in detail the fascinating study of sundials
from the beginning of mankind's recorded history will find the following
references helpful (Gatty 1900, Newton and Mayall 1938, Hogben 1946,
Winthrop 1975, Gibbs 1976, Wilson 1980, Rohr 1982, Apel and Pytel
Greeks and Romans in particular created a great variety of sundial
types and used them throughout their far-flung empires (Gibbs 1976).
In the following paragraphs we give a brief outline of some of the
most important events connected with time keeping in that part of
Anaximander of Miletus is
believed to have introduced the first knowledge of sundials to Greece
during the 6th century BC. The Greeks had many public sundials consisting
of tall columns casting shadows onto the ground, and many citizens
had their own sundials. Aristophanes' play 'The Frogs' written in
405 BC (Tucker 1906) contains the line "When the shadow is ten steps
long, come to dinner"
About 340BC Berosus,
a Chaldean astronomer-priest living in Egypt during the time of
Alexander the Great, developed the hemisphericum, in which a vertical
post was placed centrally inside a hollowed out hemisphere. The
inside surface of the hemisphere had vertical lines carved on it
to divide the daylight period into 12 hours, and horizontal lines
to show the seasons. The shadow cast on the inside surface of the
post marked out the path of the sun as it travelled across the sky.
From this developed the
hemicyclium, shown in Figure 2, which was widely used throughout
the civilised world right up until the 14th century.
About 100BC the Tower
of the Winds (De Solla Price 1967, Aked 1992, Aked 1993, De Solla
Price and Noble 1968, and Figure 3) was erected in Athens at the
foot of the North Slope of the Acropolis. This is an octagonal tower
whose walls face towards the 8 cardinal directions North, South,
East, West, North-East, North-West, South-East and South-West. It
is so named because each wall features a carving with allegorical
representations of the wind which blows from that particular direction,
together with its name. Although it was primarily designed to contain
a Clepsydra (waterclock), a large sundial with a horizontal rod
gnomon was carved into each wall. The angle of the shadow on each
sundial told the time, while the length of the shadows told the
date, so the building acted as both clock and calendar. The Tower
is accurately aligned North-South, so the sundial markings on the
complementary faces (e.g., NE and NW) are repeated as mirror images.
The carved lines of the sundials were reported as being very faint
some 60 years ago, but today they are almost indistinguishable due
to the ravages of pollution and acid rain. After all this time,
it is not surprising that the gnomons are missing.
In the following centuries
the Greeks developed the sundial further, and experimented with
hemicycles, conical dials, cylindrical dials and flat dials set
at various angles. In those days, a system of unequal or temporary
hours was in common use, with the available period of daylight divided
into 12 parts resulting in 12 long daylight hours in summertime
and 12 short daylight hours in wintertime. Astronomers, however,
used 'equal' hours (just as we do today) for charting the moving
The Romans are not believed
to have developed any new sundial types, but they certainly used
all the Greek sundial developments, and sundials were extremely
popular throughout their empire. Surviving specimens of Roman portable
sundials have been found designed for latitudes from Britain through
Narbonne in France to Ethiopia and Mauritius.
The playright and poet
Titus Maccius Plautus (250-185 BC) produced the following verse
which demonstrates just how common sundials had become in Rome during
his lifetime (The English translation given here is taken from Mayal
and Mayal 1973):
The Roman architect, engineer
and writer Vitruvius mentioned 13 kinds of sundials including portable
types, in the 9th volume of his work on architecture 'De Architectura
Libri Decem'. This treatise, containing two chapters dealing with
gnomonics was published in 27 AD but was later lost, and only rediscovered
in 1486 (Granger 1931-1934). One of the sundials discussed by Vitruvius
was the pelekinon, the type built by the Emperor Augustus in Rome
in 9 BC which covered a vast floor area of 180m x 110m and used a
30m tall obelisk from Heliopolis in Egypt as its vertical gnomon.
This particular sundial will be discussed in a later article.
"The gods confound
the man who first found out
How to distinguish hours! Confound him, too,
Who in this place set up a sun-dial,
To cut and hack my days so wretchedly
Into small portions. When I was a boy
My belly was my sun-dial; one more sure,
Truer, and more exact than any of them.
This dial told me when 'twas proper time
To go to dinner, when I had aught to eat.
But now-a-days, why, even when I have,
I can't fall-to, unless the sun give leave.
The town's so full of these confounded dials,
The greatest part of its inhabitants,
Shrunk up with hunger, creep along the streets."
150 AD Ptolemy of Alexandria (Ptolemaeus 1984, Peters and Knobel
1915) produced a book entitled 'He Mathematike Syntaxis ('The Mathematical
Collection') which 9th century Arabic astronomers renamed the Almagest
or 'Greatest Work'. In this work Ptolemy set forth his theory that
the earth is stationary and at the centre of the universe, and that
the Sun and the Moon and all the planets revolve around it. He also
showed how to draw the hour lines of a sundial by projection and
invented the analemma. His book was fortunate to survive the tragic
burning of the great library at Alexandria in the mid 7th century
Although the Greek Aristarchus
had suggested 400 years before Ptolemy that the Earth and other
planets circle the Sun (Anon 1986), the Ptolemaic Earth-centred
theory was taken virtually as an article of faith right up until
the 16th century when it was replaced by the Copernican Sun-centred
system (Copemicus 1976). However, the Earth-centred concept is still
perfectly satisfactory for describing and designing sundials, so
we are probably the only members of the human race still sticking
to Ptolemaic principles!
One of the many controversial
dates in gnomonic history relates to when the gnomon of a sundial
ceased being either vertical or horizontal, and was first inclined
at the latitude angle to make it parallel to the axis of rotation
of the Earth. Only when this happened could sundials tell time according
to the system of equal hours. By the 14th century this method of
constructing sundials had become common in Europe, and at about
the same period mechanical clocks which divided the day into 24
equal hours started to appear. The early clocks were rare and very
expensive, and not terribly accurate. They were often wrong by several
hours and were frequently calibrated using sundials. Some mediaeval
towns became famous because of their sundials one example
is Rothenburg ob der Tauber in Germany which still has many splendid
sundials that were made long ago.
In addition to telling
the time using lines and numbers marked on a dial plate, sundials
needed to have human appeal. Fine craftsmen developed high levels
of artistic skill and decorated their sundials with embellishments
of every kind. This artistic decoration, or 'furniture' as it is called,
required many hours of labour to be carried out on both the dial plate
and the gnomon (the part which casts the shadow). Many of these old
sundials are now family heirlooms and very costly antiques which only
museums and the like can afford to buy. As a direct consequence of
the design difficulties and the labour required to produce a sundial,
most people were unable to afford the high cost of such instruments.
Consequently the owners of these enduring sundials throughout history
have been the wealthy and public institutions such as cathedrals,
parks and town halls. Figures 4 and 5 illustrate typical elaborate
and consequently expensive sundials.
Countless sundials have
been designed and made in every conceivable shape, size and form.
The most commonly used materials for these sundials were copper,
brass, bronze and stone, materials chosen mainly because of their
ability to resist corrosion and because skilled craftsmen could
work in these materials using traditional techniques. The time-telling
hour lines marked on these old sundials were carefully placed in
position using intricate graphical construction techniques which
were based on sound geometric theory developed over many centuries.
Hundreds of ancient sundial books abound which describe in confusing
detail how to 'lay-out' or draw a sundial. These geometrical methods
are complicated, tedious and very time consuming. Fortunately such
methods can now be totally discarded. The ready availability of
computers and pocket calculators allows even complicated sundials
to be accurately designed using simple mathematical equations derived
from the basic principles of spherical trigonometry. (The formulae
that allow you to do this yourself will be given in a future article).
Aked, C.K. 1992: The
Tower of the Winds. Bulletin of the British Sundial Society
No.92.3 & 93.1.
Anon 1986: On the
sizes and distances of the Sun and Moon. From Writings of
Archimedes and Plutarch, Encyclopaedia Brittanica (15th edition)
Vol. 1, p. 554.
Apel, J. & Pytel,
C. 1990: L'Ombre Domestique. Bonneyfoy, La Mesniere France.
De Solla Price, D.J.
1967: Athen's Tower of the Winds. National Geographic Magazine
Vol. 131, No. 4.
De Solla Price, D.J.
& Noble, J.V. 1968: The Waterclock in the Tower of the Winds.
American Journal of Archaeology Vol. 72, p. 345-355.
Dolan, W.W. 1975: A
Choice of Sundials. The Stephen Green Press, Vermont,
Duncan, A.M. (translated).
1976: Copernicus: On the Revolutions of the Heavenly Spheres.
David and Charles, Devon, UK.
Gatty, A. 1900: The
Book of Sundials. 4th edition. George Bell and Sons, London.
Gibbs, S.L. 1976: Greek
and Roman Sundials. Yale University Press, USA.
Granger, F. 1931-1934:
Vitruvius Pollio Marcus on Architecture. Laeb Classical
Library, Book number 251, London.
Hogben, L. 1946: Science
for the Citizen. George Allen and Unwin, London.
Mayal, R.M. & Mayal,
M.W. 1973: Sundials, How to know, Use and Make them.
2nd edition. Sky Publishing Company, Cambridge, USA.
Peters, C.H.F. &
Knobel, E.B. 1915: Ptolemy's Catalogue of Stars: (A Revision
of the Almagest). Washington Main Library USA.
Rohr, R.R.J. 1982:
Die Sonnenuhr. Callweg Verlag, Munchen, Germany.
Toomer, G.J. 1984:
Ptolemy's Almagest. Gerald Duckworth and Co Ltd, London.
Tucker, T.G. 1906:
The Frogs of Aristophanes. McMillan, UK.
Wilson, C. 1980: The
Book of Time. Westbridge Books, The Jacaranda Press.
more information on sundials, John
Ward and Margaret Folkard have published the book, Sundials
1996, 113 pages, A4 size, 90 black and white photographs and 100
line drawings. This authoritative book includes relevant facts about
the Earth, Sun and stars, and the various types of sundial, and
the relationship between sun and clock time. Formulae for calculating
hour lines are clearly listed. The blackness and sharpness of shadows
is discussed. There is also a collection of mottoes, a dictionary
of sundial terms, and a list of references. Price $A20 plus $A9
This book has briefly
been reviewed on
the RNZIH Horticulture Pages.
It is available from
Books and listed by Sundials
on the Internet (sponsored by the British
Sundial Society) and the USA-based company SunPath
to Part 2 of this article
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