The "
Story of Raudulf and His Sons" tells how King
Olaf visited the farmer Raudulf and his sons Dag and Sigurd. Sigurd claims an ability to locate the sun even in overcast conditions (an important navigational skill), and Olaf verifies his claim using what the saga seems to assume is a standard tool: the
sólarstein or sunstone:
Veður var þykkt og drífanda sem Sigurður hafði sagt. Þá lét konungur kalla til sín Sigurð og Dag. Síðan lét konungur sjá út og sá hvergi himin skýlausan. Þá bað hann Sigurð segja hvar sól mundi þá komin. Hann kvað glöggt á. Þá lét konungur taka sólarstein og hélt upp og sá hann hvar geislaði úr steininum og markaði svo beint til sem Sigurður hafði sagt. (Poster & Utz,
Constructions of Time in the Late Middle Ages)
It has
long been suggested that these sunstones may have been crystals of minerals – such as
iolite,
tourmaline, or
calcite – which respond to polarised light.
Viking Ship (stained glass by Edward Burne-Jones)A
recent article, summarised in
Nature News, lends support to the idea. Susanne Aakesson, one of the authors, reports that "I tried such a crystal on a rainy overcast day in Sweden. The light pattern varied depending on the orientation of the stone." The team has also done considerable quantitative experiments. Work is ongoing, however: "Since the psychophysical experiments, outlined above, cannot be performed with Viking navigators, we plan to measure the error functions by using male German, Hungarian and Swedish students. These measurements are in progress."
Iolite and calcite: was one of these the Viking sunstone?Hat tip:
Bayou Renaissance Man.
