1996_137.pdf

New Interpretations of Viking Age

Weathervanes

By Jan Engström and Panu Nykänen

Engström, J. & Nykänen, P. 1996. New interpretations of Viking Age weather-

vanes. Fornvännen 91. Stockholm.

The famous Viking Age weathervanes which have been found in Sweden, Norway

and Finland are re-examined. The authors daim that weathervanes were not

merdy objets d'art or symbols of rank but also played an important part as navi-

gation instruments. Weathervanes were used as angle measuring devices for es-

timating the height of the sun or stars above the horizon. Låter on the weather-

vane was adopted by the Christian Church and its original use was forgotten.

Panu Nykänen, fan Engström, Dejmrlnient of archaeology, University of Helsinki, PL 13,

El-00014 Helsingin YUopisto, Finland.

Viking navigation

It is common knowledge that the Vikings were

very active sailors throughout the Viking era.

Their extensive journeys were made possible

by their relatively seaworthy vessels, their high

standard of seamanship and their knowledge

of celestial navigation.

Ships were navigated on the open sea by ex-

pert navigatörs who were very highly respected

in their society (Norr 1987). Some physical ev-

idence concerning the actual practice of

Viking age navigation and sailing has been pre-

served. Most of this knowledge is obtained

through interpretations of the Icelandic sagas

and by means of experiments with replicas of

Viking ships (Crumlin-Pedersen & Vinner eds.

1986). However, navigation in particularly has

been neglected and up-to-date descriptions of

Viking Age navigational skills and aids are rare.

It is true that very few actual artefacts which

could be associated with both navigation and

the Viking Age have been preserved but there-

is one object which bas been taken as being

wholly other than a navigation instrument.

The Viking age weathervanes (or wind-

vanes), most of which bave been found in

Medieval churches in Norway, Sweden and

Finland have hitherto been regarded as non-

finictional windvanes, mere symbols of rank

and power. There is no reason to disagree with

the opinion that they were indeed used also for

tbis purpose, but in our view they were de-

signed primarily as navigation instruments;

only låter were they adopted by the Christian

Church, and the original function forgotten.

The weathervanes

The weathervanes seem to have been used to

measure celestial angles in two different ways.

The first probably served to measure the stars"

height from the horizon since the vanes are de-

signed to be focused directly onto the object.

Naturally this was impossible with regard to the

sun. The so-called miniature weathervanes

from Saltvik, Äland and Björkö, Sweden are of

this type I. The measurement is performed

through a diopter siglu, and the reading can be

taken with a lead-line attached to the plate

(Fig. 1). The weathervanes of type II were most

likely used for mcasincment of the height of

the sun using the shadow thereof as an indic-

ator (Fig. 2). The instruments accuratdy

aligned with tlie horizon with the help of a lead

or a wooden plank floating in a bucket of water.

Fornvännnni 91 (1996)

138 J. Engström åf P. Nykänen

Fig. 1. The so called miniature weathervanes (type I) can be used to determine a star's height above the ho-

rizon. - De s.k. miniatyrvindflöjlarna (typ I) kan användas för alt bestämma stjärnornas höjd över horison-

ten.

Some minerals are capable of polarizing

light, so that the position of the main light

source can be determined despite the presence

of clouds. The use of this so-called sålarsteinn

(sunstone) has enabled measurements even

when the skies were overcast (theory by Ram-

skou 1967). A sålarsteinn could easily have been

attached to the weathervane.

The most important fact is that the division

of the readings in all the instruments is the

same, approximately 4.8 degrees up to the

height of 70° above the horizon. The reading

divisions of the weathervanes are measured

from the angle between the vertieal axis and

the marks along the edge of the instruments.

It must be noted, that while the readings

from the weathervanes can be measured nowa-

days very predsely with modern devices and

computer technology, formerly the measure-

ments were based only on human eyesight, pre-

sumably in very rough conditions. So computer

interpretation could lead to wrong impressions

of tlie instrument because of two sources of er-

ror. The significant facts in the reading of

angles could be distorted, so that a modern

man would search for meanings which were

unibinkable in the Viking Age. So all the given

numbers have only a representative value—

they were not in use in real life.

We do not know for how long navigatörs

have used measurements of degrees of angle

readings. Most probably the basic unit used by

the Vikings was the semidiameter (S.D.) of the

sun—wiz. 0° 16'. 20 x S.D. = 5° 20' nearly coin-

ddes with the mean division of the readings in

the weathervanes. Twenty is known to be an an-

Fornvännnen 91 (1996)

New interpretations of Viking age weathervanes 139

få

Fig. 2. The so called weathervanes (type II) contain marks which were probably used for measurement of the

height of the sun. In all five known cases the division of the readings is approximately 4.8 degrees. - De

större vindflöjlarna (typ II) har punkter som troligen har använts för att mäta solhöjden. Pä alla de fem

kända flöjlarna är delningen ca 4,8°.

dent measurement unit in many contexts. The

reading accuracy is, of course, much better.

The instruments in question could easily be

read in the accuracy of 10 S.D.'s—which surely

enabled a landfall on Iceland or the Faeroes.

The marked division of angles in the instruments

(the artefacts are listed in Lindgren & Neumann

1984); def. = deformed structure.

Saltvik, Rangsby, Åland, Type I.

4.5°; 9.9°; 14.3°; 22.1°; 27.7°; 36°; 41.5°; 50.5°; 56.5°;

64°; 68,6°; 73.1°; 80.3°

Björkö, Sweden, Type I.

?; 8.0° def?; 13.7° def?; 15.3°; 20.7°; 25.0°; 29.6°;

33.8°; 38.7°; 42.2°; 46.5°; 50.5°; 54.3°; def.; def.

Söderala,Hälsingland, Sweden, Type II.

3°; 7.2°; 11.8°; 16°; 20.8°; 25°; 29.1°; 33.8°; 38°; 42.5°;

46.2°; 50.8°; 55.3°; 59.8°; 64.2°; 69.3°; 73.9°

Källunge, Gotland, Sweden, Type II.

3.9°; 9.1°; 14.1°; 19.2°; 23.7°; 30°; 35°; 40.2°; 45.7°;

50.9°; 55°; 61°; 67°

Hoyford, Vestfold, Norway, Type II.

5.1°; 11.2°; 16.8°; 23.1°; 29.2°; 34.2°; 41°; 46.8°; 52.2°;

59°; 65.2°; 72°; 79°

Tingelstad,Oppland, Norway, Type II.

5.1°; 11.9°; 18.5°; 25.4°; 31.7°; 39.4°; 46.3°; 54.3°;

61.8°; 68.7°

Heggen, Buskerud, Norway, Type II.

4.2°; 10.7°; 16.7°; 22.5°; 29.1°; 35.5°; 42.7°; 50.5°;

57.4°; 65.7°; 73.5°; 82.5°

The inaccuracies between the instruments can

be explained by the manufacturing techniques

and the usage of the instruments. Each of them

was made to suit the experience and knowl-

edge of those who would use it. Therefore the

mathematical approach to the task of mea-

surement is not necessary. However since the

the reading accuracies of various instruments

are very similar, there must have been a rule of

thumb for the division of angles. The similar

Fornvännnen 91 (1996)

140 J. Engström åf P. Nykänen

lSknn^i¥\

Fig. 3. Part of a picture of Viking ships from Bergen, Norge. It shows some ships equipped with weatherva-

nes beating into Ihe wind. Note the flag with stripes in the opposite direction. - Utsnitt av ristning med vi-

kingaskepp från Bergen. Den visar några skepp utrustade med vindflöjlar riktade mot vinden. Märk vimpeln

vänd i andra riklingen.

division may originate in the sailing experi-

ences in the Northern Atlantic. Moreover at

least some of the existing weathervanes are

copies, in which case the significance of their

markings had been forgotten.

(Beckman 1913). Thus a Viking navigatör

could try to sail along the same latitude all the

way to the desired destination. This method is

commonly known as latitude sailing. In order

to remain on a specific latitude, a navigatör

needed to know the sun's meridian passage

height from the horizon or a certain star's

zenith height on the desired latitude. Further-

more, he must be able to see both the horizon

and the astronomical object, and have a device

to measure the angle (i.e. the height). The

quadrant and the solsskuggafjol which are

known from literary sources, must have served

this purpose and according to our studies so

did the so-called weathervane.

Since the voyages över the North Atlantic

were fairly fréquent, the Vikings must have felt

confident when setting out to a transatlantic

passage. Naturally, good weather, especially a

fair wind and clear skies, were awaited before

embarking on a journey. Nevertheless, the

Vikings were the best navigatörs of their times

and weathervanes were the top-of-the-line nav-

igation instruments in which beauty and func-

tionality merged.

The essence of navigation

Terrestial navigation was based primarily on

experience and tradition, and special instru-

ments were used by navigatörs sailing in

friendly waters with land in sighl. When a sailor

wanted to cross open sea with no landmarks,

an wholly different approach and understand-

ing of space was necessary.

The Vikings had names for at least all of the

eight cardinal points of the compass, and they

were undoubtedly able to divide the rose even

more precisely when necessary. Sixteen inter-

cardinal points result already in an accuracy of

22.5 degrees, and in most cases without ad-

equate information on time this is the limit of

their precision notwithstanding that the poss-

ible bearing dial fragment found in Greenland

is divided into 32 sections (an accuracy of 11.25

degrees) (Binns 1971, p. 24).

The Viking navigatörs, particularly the Nor-

wegians, had an awareness of latitnde. Cen-

turies of sailing up and down the predomi-

nantly north-south oriented Norwegian west

coast had taught them how the height of the

sun and the stars över the horizon varies de-

pending on the season and on the point of ob-

servation. Proof of such observations have

been preserved in the manuscripls of the sagas

Dimensions in the Northe Atlantic

At first glance, the North Atlantic is a väst space

of sea, but if we take a doser look, we realize

that no matter what direction is followed from

the west coast of Norway, it would be almost

impossible not to hit either the British Isles, the

Shetland or the Faroe Islands, or Iceland. This,

of course, is not an appropriatc approach for a

1'oritvännnfi, 91 (1996)

New interpretations of Viking age weathervanes 141

merchant with a specific destination and pre-

sumably a cargo to deliver, but it gives an idea

of the degree of accuracy was called for when

sailing in the North Atlantic.

If, for the sake of the argument, we stipulale

that the Viking ships could sail with an average

speed of five knöts (nautical miles per hour), it

would then take less than five days to cover the

500 miles from Norway directly to Iceland.

With a speed of 3 knöts the journey would take

about seven days. So the time spent on the

open sea was not as long as would be expected.

Most of the sailing was done during the sum-

mer, when weather conditions were fair and

stable. Moreover Haasum (1974, p. 93) sug-

gested that the weather on the North Atlantic

in general was more stable a thousand years

ago than today. If the navigatör could measure

the ships latitude once a day an adequate ac-

curacy of navigation was attained.

The social status of lhe weathervane

The bronze of which the weathervanes were

made was so precious as to make the instru-

ments extremely valuable to the Vikings. But

their true importance lay in their usage. The

Viking ship which could afford to carry one

and an individual who could use it, was able in-

dependently to sail the open seas. This made it

possible to approach the British Isles and the

continent of Europé, and withdraw to the open

sea when the situation so required.

Probably the ship carrying the instrument

was leading a fleet, and because of ils special

status as a flag ship, the instrument functioned

as a pennant when not used for navigation

(Fig. 3) (see Lindgren & Neumann 1984, p.

24). All known examples of weathervanes, ex-

cept type I, are decorated with a recognizable

picture of a dragon (see Blindheim 1982; Lind-

gren & Neumann 1984, p. 21). This may per-

tain with the known fact that the biggest Viking

warships were called dreka. It is possible, of

course, that the instruments secondary func-

tion superseded its primary purpose already

during the Viking Age. Blindheim (1982) per-

ceived a change in the construction of the

weathervanes after the llth century. The

change could indicate the end of their primary

use.

Fig. 4. Reconstruction of a wooden instrument which

was probably used during the Viking Age to measure

Ihe height of the sun. - Rekonstruktion av träinstru-

ment som troligen har använts under vikingatiden

för att mäta solhöjden.

The other known type of instrument (Fig.

4) used in the Viking Age to measure the sun's

height is possibly easier to use—it can be hori-

zontally aligned simply by floating the whole

instrument in a bucket of water. It was also

much cheaper, beeing made of wood. So a new

instrument probably came into general use

soon after its invention. If so, it is remarkable

that this did not change the angle readings in

any of the known weathervanes.

The Medieval Church assumed the spiritual

power in Seandinavia just as the Viking raids

ended. Once the weather conditions deterio

rated and the routes between Seandinavia, Ice-

land and Greenland were closed, the trade

ceased. When commercial trade had no need

for open sea navigation—merchant vessels

hugged the coast—the navigation instruments

became useless. The Church adopted the status

Fornvännnen 91 (1996)

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