Sun – Current – Ocean Swell: Additional Remarks on Viking-Age Navigational Skills

The function of the so-called ‘sun compasses’ was recently discussed in this journal by Wojciech Filipowiak, who dismissed the idea of their use as a navigational aid of the Vikings to find their way across the open seas (Filipowiak, 2020). There is, apart from a few remarks, nothing to add to his argumentation, but there are a couple of other navigational means, recorded outside the late medieval North Atlantic region, which are worth considering, but have not been discussed yet. Unlike the use of astrolabes and cross-staffs, which have been tested on transatlantic passages (Beach & Atkinson, 2004; Knox-Johnston, 1991, pp. 191–200, 2013, pp. 69–71; Köberer, 2014) there is only one mentioned, but failed attempt of practical testing of a sun disc. In 1991/92, Burghard Pieske crossed the Atlantic from Denmark to New York in a scaled-down copy of the Gokstad ship, Wiking Saga (Pieske, 1993, pp. 28, 33–35). In 1992 (no date given), after wintering in Greenland, it was planned to use a sun disc for measuring the latitude on a passage to Labrador. On the beginning of the passage, though the sky was partly overcast, the instrument was tested. Unfortunately, under these conditions the central pin of the disc did not cast a shadow. Later on, the sky became totally overcast and this lasted until the end of the crossing (Pieske, 1993, pp. 330, 333–334). When using the sun for finding the latitude during a passage, one has to allow for the sun’s declination moving to the north or the south. Apart from a couple of weeks, immediately before and after the summer or winter solstice, this reaches up to 24 ́ a day (Reed’s, 1981, pp. 12–81). It adds up to about 2° on a five-day passage, which equals 120 nm at the equator. On the other hand, simple navigational instruments can well be used as aids for steering the right course, as Timothy Severin showed in 1980 when he was able to find the latitude on a trip from the Persian Gulf to India by using a ‘kamal’ and Polaris (Severin, 1983, pp. 96–98). Apart from the Pole Star others were utilized as well by the Arabs on long-distance voyages (Shihab, 2013, pp. 21–34). These techniques were practically tested in 2010 during a passage from Muscat to Singapore on Jewel of Muscat (Staples, 2013, pp. 51–60). It must be pointed out that in Nordic written sources there are no hints for the use of any kind of instrument for navigational purposes. Instead, there is a note from AD 1267 about an expedition to northern Greenland, stating that ‘the sun shone day and night. When he was south, he was not higher above the horizon that his shadow covered the face of a man who was laying on a thwart in a six-rower’ (Schnall, 1975, p. 90, translation author). The settlement of far-off lying islands started in the early Neolithic period not only in Europe, but elsewhere as well (e.g. Weski, 1982, p. 191), which is a clear indication that the necessary skill for offshore navigation must have been available. This applies also to the trade between the Red Sea and India from the Roman Period onwards or the settlement of the Faroes by persons from the British Isles about 300 years before the arrival of Nordic peoples (Blue, 2007, p. 265ff; Curtin et al., 2021, p. 5). Further, there are hints for navigation without instruments in other geographic areas or periods (e.g. Anichtchenko, 2016, p. 307; Davydov, 1977, pp. 155–156; Hansen, 1965, p. 105; Weski, 1982; 2012, pp. 231–232; Whitridge, 2004, pp. 221–226). Considerable navigational knowledge was also required for other passages like crossing the Pentland Firth near the Orkneys with its strong tidal streams (Weski, 1982, p. 201, 2012, p. 232). Finally, navigators must have possessed knowledge of weather lore. For example, in about AD 400 on a passage from Egypt to Libya the captain made a long slant offshore, because he expected strong winds from another direction and did not want to be caught by a lee-shore (Casson, 1952, p. 296; Fitzgerald, 1926, Epist. 4,10; Kahanov, 2006, p. 439). Before Early Modern Times written sources mentioning navigational skills are rare with the exception of Nordic sagas (see below). For example in AD 1075 Adam of Bremen wrote that the distance between Jutland and Norway could be covered in a ‘saltu per noctem’. From this Detlev Ellmers concluded that