Dear Margaret,
Thirty or forty years ago, the Scientific American had an article on iceland
spar as a navigational aid. At 85, I now must rely on the computer to check
my facts. Using MOMMA, my favorite search engine I located the following
information, the rest is a quote.
http:%2F%2Fwww%2Erealtime%2Ecom%2F~gunnora%2Fnavigate%2Ehtm (Altavista) 85%
Gentle Readers: After my last informative article which discussed the
varieties of longships, I received the following missive: "Hey, Answer Lady!
You...
http://www.realtime.com/~gunnora/navigate.htm
Although it distresses the Viking Answer Lady to be faced with flatly
contradicting one of her Gentle Readers, I am afraid in this instance I must
do so. While it is true that the Vikings (like many other medieval mariners)
were unable to precisely measure longitude (east-west distance), they had
many very sophisticated techniques tailored for sailing in the northern
latitudes (latitude is north-south distance). The most important
navigational aid used by the Viking navigator was the Sun herself. In the
far northern seas, the sun indicates not only east (at sunrise) and west (at
sunset), but at noon the sun is due south, and in the months when the sun
does not set below the horizon, the position of the sun at midnight
indicates due north. Since the northern seas are often foggy or subject to
overcast weather, an ingenious Viking developed a navigational tool not
equalled until the development of polarized glass: this was the sunstone, a
crystal of Iceland spar or andulacite which naturally polarized light. This
enabled the Vikings to locate the position of the sun even when it was
screened by clouds, and many a Northern mariner wore his sunstone around his
neck as a lucky talisman.
References
Konugs skuggsiá. Edited by Ludvig Holm-Olsen. Oslo. 1945.
Sturlubók (Landnámabók, Sturla Ţórþarson's version) Ed. by Jakob
Benediktsson. Íslenzk fornrit 1: pts 1-2. Reykjavík. 1968.
Gelsinger, Bruce E. Icelandic Enterprise:Commerce and Economy in the Middle
Ages." Columbia: Univ. of South Carolina Press, 1981.
Gelsinger, Bruce E. "Lodestone and Sunstone in Medieval Iceland." Mariner's
Mirror 56(1970):219-26.
Gelsinger, Bruce E. "The Norse 'Day's Sailing'." Mariner's Mirror
56(1970):155-65.
Gelsinger, Bruce E. "Review of Thorkild Ramskou's 'Solstenen'" Scandinavian
Studies 42(1970):362-63.
Ramskou, Thorkild. Solstenen: Primitiv navigation i Norden fřr kompasset.
Copenhagen. 1969.
Sřlver, Carl V. "Leitharsteinn: the Compass of the Vikings." Old Lore
Miscellany 10(1946):293-321.
Taylor, E.G.R. The Haven-Finding Art: A History of Navigation from Odysseus
to Captain Cook. London. 1956. See esp pp 90-91 on the work of Star-Oddi
(Oddi Helgason).
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