Winter in the great Northwest; Winter Brothers: A Season at the Edge of America, by Ivan Doig. New York: Harcourt Brace Jovanovich. $10.95

At an age when many people think of retirement and rocking chairs, James Gilchrist Swan embarked on a three-month-long exploration of the Queen Charlotte Islands in the Pacific Northwest. His mandate was to collect Haida Indian artifacts for the Smithsonian Institution -- "we want the fullest collections of all kinds," they said -- and the year was 1883.

Swan had come west from Massachusetts in 1850, leaving behind his wife and two children. The magnetic pull of the West was strong then, and the promise of a new life across the continent obviously appealed to Swan. The variety of his new life, however, renders immobile even the most flexible of imaginations.

Over his years in the Pacific Northwest, Ivan Doig tells us, Swan worked as: "oyster entrepreneur, schoolteacher, railroad speculator, amateur ethnologist, lawyer, judge, homesteader, linguist, ship's outfitter, explorer, customs collector, author, small town bureaucrat, artist, clerk."

"Winter Brothers" is the story of Swan, pioneer extraordinaire,m whose diaries Doig, author of "This House of Sky," became entranced with while digging through the University of Washington libraries.

These diaries, kept regularly from 1862- 1890, are a treasure chest of information on life in the Pacific Northwest. Swan is especially enlightening about the Indians -- Haidas, Makahs, Nootkans, and others -- because not only did he know many of them, and closely observe their customs, but he liked them.

Into the crazy-quilt fabric of Swan's voluminous diaries is woven 90 days worth of diaries by Doig. The two are indeed winter brothers, kindred spirits in occupation (diarists) and in place (Doig lives in Seattle) if not in time.

The interchange between Swan and Doig is musical. Their moods dip up and down, sometimes in tandem, sometimes in counerpoint. They remark on the weather , on their personal lives, and they watch -- with eyes alert to its wonders -- the world that surrounds them.

Here is Doig describing the Olympic Peninsula. "The power and loft of the Sitkas [spruces] . . . are merely the might above the rampant details of the rain forest, like crags over delicate valleys. Nature here tries a little of everything green."

Here is Swan with a sliver of ornithological arcana. "I discovered a dead albatross on the beach yesterday which had a large dogfish which it had swallowed partially but it was too large, and while the fish's head rested in the bird's stomach, its tail was out of its mouth. Consequently the bird was soon suffocated. . . . I never met with a similar instance of voracity."

Observations such as these fill "Winter Brothers." A book of either man's diary pages alone would give more than any reader has a right to ask. But is is the interchange between Swan and Doig that gives the book its unique flavor.

"Our perimeters are strange," says Doig of Swan and himself, "unexpectedly full of flex when we touch against them just right. A winter such as this of mine . . . I think must be a kind of border crossing allowed us by time: special temporary passage permitted us if we seek out the right company for it, guides such as Swan willing to lead us back where we have never been."

We owe Doig more than we can repay for letting us make the enchanting journey that connects today and the past through the pages of "Wint er Brothers."