Black and white spirits

I have a friend, Olof Ehrensvärd, a Swede by birth, who yet, by reason of a strange and melancholy mischance of his early boyhood, has thrown his lot with that of the New World. It is a curious story of a headstrong boy and a proud and relentless family: the details do not matter here, but they are sufficient to weave a web of romance around the tall yellow-bearded man with the sad eyes and the voice that gives itself perfectly to plaintive little Swedish songs remembered out of childhood. In the winter evenings we play chess together, he and I, and after some close, fierce battle has been fought to a finish—usually with my own defeat—we fill our pipes again, and Ehrensvärd tells me stories of the far, half-remembered days in the fatherland, before he went to sea: stories that grow very strange and incredible as the night deepens and the fire falls together, but stories that, nevertheless, I fully believe.
One of them made a strong impression on me, so I set it down here, only regretting that I cannot reproduce the curiously perfect English and the delicate accent which to me increased the fascination of the tale. Yet, as best I can remember it, here it is...