CELTIC NAVIGATIONAL TECHNIQUES

Today, navigation is regarded primarily as a science, and seafarers have many aids to help them find their way and keep a reckoning of their position in the seas off northwest Europe. Before the twelfth century AD this was not so; the only instrument in use was the sounding lead, and navigation was more of an art in that personal skills were used. Being essentially non-instrumental, there is no artefactual evidence for the methods used by the Celts. There is, however, indirect archaeological evidence and some documentary evidence, and we can also draw on comparative evidence from other times and places with a generally similar technological background (Olsen 1885; Lewis 1972; Waters 1978: 3-38; Binns 1980: 79-80; McGrail 1989).

The alignment of neolithic and bronze age megalithic structures in Britain, Ireland and Erance indicates a knowledge of the sun’s movements and possibly those of the moon (Wood 1978: 184-8; Heggie 1981: 222-3). The Celtic world inherited this learning and extended it: Caesar {De Bello Gallico vi.14) describes the Celts’ knowledge of astronomy, ‘the stars and their movements’, and there was particular emphasis on the moon (Piggott 1974: 104-5); being the chief arbiter of tides, the moon would be of particular importance to maritime Celts. Recent analysis of the fragments of a second century AD calendar, found in 1897 in a vineyard at Coligny, north of Lyons, has shown that it was primarily a lunar calendar adapted to the solar cycle, with an error of only i day in 455 years (Olmsted 1992). This further emphasizes the Celts’ ability to study the heavens systematically, an ability which would have been especially needed by Celtic navigators.

Precisely how directions and distances at sea were measured and described by the Celts is not clear, but contemporary Roman usage and comparative evidence from such diverse sources as the Vikings (McGrail 1987) and Homer in his account of Odysseus’s voyages (McGrail forthcoming), suggests that distances would have been in units of a standard day’s sail. Directions, when land was out of sight, would probably have been estimated relative to the wind, the swell, sunset and sunrise, and at night from the Great Bear (Ursa Major) or even the Little Bear (Ursa Minor) or other constellations (McGrail 1983) for in those times there was no star actually at the North Pole (the null point about which the heavens appear to revolve).

Celtic navigators would have ‘plotted’ these estimates of distances and directions travelled on their ‘mental sea charts’ and so determined their position relative to their home base or to their overseas destination (McGrail 1983).

The Celts paid great attention to memory training and oral instruction for the transmission of learning (Caesar, De Bello Gallico vi.14; Chadwick 1970: 45-7; Ross 1970: 125-6). The motions of the heavenly bodies, the phases of the moon and the ebb and flow of the tides, the weather sequences, descriptions of coastal landscapes, safe channels and sailing marks leading to the main landing places, the direction and distance between point of departure, and landfalls for each overseas route used - all these would have had to be memorized by Celtic seamen, encapsulated in easily remembered phrases and rules of thumb, possibly in verse form, which medieval Arabs are known to have used (Tibbetts 1981).

We can theorize that the following oral sailing directions might have been learned and used by a fifth-century BC seaman crossing from Mounts Bay, Cornwall, to Ushant off Brittany:

Leave Mounts Bay in the afternoon on an ebb tide and with a westerly wind (as is often the case in the sailing season). Keep this wind as far forward of the starboard beam as is practicable and steer away from land, noting your track by reference to memorized landmarks and seamarks; use the sounding lead if necessary.

Take departure from land before sunset by noting your position relative to Lizard Head or Gwenap Head, and maintain or turn to that heading which puts the wind just forward of the starboard beam. Note the relative direction of the sea swell. Confirm the boat’s heading at sunset when the sun should be on or near the starboard beam. When dark, keep the Great Bear constellation fine on the starboard quarter. Check wind and swell direction against this bearing. At dawn check them against the bearing of sunrise which should be on the port quarter.

Certain types of cloud or the flight line of birds may give early warning of the French coast. If the standard speed [4 kts in twentieth-century terms] has been maintained, and visibility is good, high ground beyond the French coast should be seen on the port bow at around the time of day when the sun is at its highest. The island of Ushant will be sighted fine on the port bow during the afternoon, well before sunset.

Use landmarks and seamarks to identify your position, and plan your approach to the land so that you have a flood tide for entering your destination haven; use the sounding lead.

Celtic seamen had solved the problems of deep-sea voyages in some of Europe’s most dangerous waters by the fifth century BC or even earlier. As the evidence stands at present, in their use of these skills they were well ahead of their contemporaries in northern Europe.