I had noticed him waiting, like me, for the bus north to Ballard from downtown Seattle. Tall, fair-haired, perhaps ten years older than me. He had the same destination as me: the Nordic Heritage Museum where I took conversational classes. What business he had there, I had no idea.

Usually I had my nose in a book during transit time, but today in boarding the bus, he sat down just across the aisle from me and I decided to act human. Once we were both settled, I caught his eye, smiled, and said, "I come to the Museum, too, every Tuesday. Learning to speak Norsk."

He nodded. "I volunteer in the gift shop."

He went on to say more in Norwegian, but I shook my head. "I'm not very good at understanding. Not very clever." I added that last phrase in Norwegian.

He chuckled and introduced himself. Leif, a good old Norse name. "I have a book for sale in the gift shop," he said. "Would you like to hear about it?" He drew a trade paperback from his briefcase.

On the front, under the title, "Secrets of the Viking Navigators," the prow of a longship was breaking through fog. My eyes must have lit up. "Yes, I'd love to hear!"

At a time when most seafarers clung close to land, charting their course by landmarks, the Norse often cut across vast expanses of open ocean. A journey would begin at a particular location on the long serrated coast of the North Way (which now we call Norway) and head straight west to reach a matching location on that latitude: the shores of Britain, or islands further north like the Faeroes, the Shetlands, and Iceland.

Expert navigators could read the position of sun and stars to maintain a westerly course. On hazy days the directions of sea current and wind could help with orientation in between fitful sightings of those beacons. But how did the Norse manage to plow through dense sea fog or lowering cloud masses?

Not only had Leif studied the old Icelandic sagas for clues but he had spent years as navigator for the U.S. Merchant Marine in the North Atlantic. It didn't take him long to recreate a "horizon board," but the "sunstone" (solarsteinn), valued highly among the old Norse, had everyone mystified.

Then Leif stumbled across mention of a type of crystal that might have been used as a sunstone: Iceland spar -- which had been quarried in Viking times at several locations around Iceland. Each crystal naturally breaks across fault lines set at a particular angle such that each cross section forms a parallelogram. Light refracts through the crystal in such a way that a spot of black tar on the far side shows through as two spots.

On days of poor sun visibility, you hold the crystal overhead with the tar-spot side topmost. You rotate until the two spots line up. That indicates the direction of the sun.

Leif's book held a well-imagined narration of a Norse crew voyaging by knarr (a wide-bellied trading vessel) from Trondheim to Iceland. Also, ship diagrams, horizon-board illustrations, several appendices, and enough maps to delight a hobbit like me.

Yes, I visited the gift shop that day and bought my own copy!

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prompt: steer

"Secrets of the Viking Navigators," 2003, by Leif K. Karlsen, is still in print (as of December 2024)