Yes, there really is a vital connection among a mussel known as Elliptio crassidens, Samuel Beckett's play "Waiting for Godot," a fish called the slipjack herring and a 1913 Mississippi River dam at Keokuk, Iowa.

Once common in the Upper St. Croix River, that freshwater mussel depends on the migratory slipjack to complete its reproductive cycle. With the advent of the dam a century ago, the slipjack could no longer navigate from its adult habitat in the Gulf of Mexico to the headwaters of the St. Croix. Recently though, biologists discovered in the St. Croix some very old E. crassidens waiting futilely, like the Godot characters, for "a fish that will never come again."

With that mournful dash of Charles Darwin, St. Croix River rat Don Mitchell penned one of those rare perspective-shifting essays that echoes in the mind long after you've turned the page.

The book, "Shimmering Blue Line," a collection of Mitchell's essays with paintings by James Wilcox Dimmers, is full of such unexpected insights and observations about the tannin-tinged waterway that for 164 miles forms the border of Minnesota and Wisconsin. To call Mitchell and Dimmers "river rats" is no disparagement, but rather high praise for friends whose lifetime love of a river has spawned a beautiful book and hundreds of paintings recording it in every season.

The book also comes with a CD of lilting folk and bluegrass-style music written by Mitchell and recorded in a Marine on St. Croix church by a pickup band whose members -- Greig Tennis (bass), Linda Wadsworth (flute), John Wenstrom (guitar), Denise Dellinger (piano) and Mitchell (violin) -- all have other careers, as teachers, lawyer, tech writer. Throw in the recording engineers (Gene DiLorenzo and Evan Johnson) and the book's foreword by explorer Ann Bancroft, and it seems that the whole St. Croix Valley was engaged in the project.

River fever

In a sense, it was. Mitchell and Dimmers have lived in the valley for decades and loved the river from first contact. Mitchell and his wife, Barbara, have a house on the very edge of an 80-foot cliff overlooking the water near Scandia, Minn., while Dimmers lives not far from the river in Osceola, Wis. Over the years they've explored pretty much every byway from the river's origin in a beaver-dammed pond near Solon Springs, Wis., to its junction with the Mississippi. Mitchell writes engagingly about everything from geological potholes and pileated woodpeckers to the scenic easements that have for 40 years preserved the valley from commercial development.

Dimmers, 64, had river fever even while growing up in White Bear Lake. As soon as they got their driver's licenses, he and his best friend would head for the St. Croix to swim at the boom site just north of Stillwater. After graduating from the University of Minnesota, he settled into an old valley farmhouse (without electricity) and set to work honing his impressionist techniques.

Philanthropist Aimée Butler provided a monthly stipend in exchange for paintings. "Thanks to her I have over 60 paintings hanging in Hazelden," the addiction treatment facility near Center City, Minn., Dimmers said. He had a studio for 27 years above the landmark Marine General Store before settling in Wisconsin six years ago.

In all that time, the river fascinated him with its fickle light and shimmering seasons. His colorful, richly textured canvases capture the dappled lemony greens of spring and the darker hues of summer waters ripping beneath cottonwoods and maples bent into the current. Autumn sets the valley ablaze with crimson, gold and fierce blue skies, while winter strips it bare above a blanket of lilac snows. Most of the pictures are grounded by muddy banks or grassy shorelines, but some look as if they've been painted, as Dimmers' hero Claude Monet used to, while sitting in a boat in the middle of the stream. Like Monet, he grounds the picture's authenticity in specific places at particular times of day, "Crunchberry Island Under Sunrise Mist" or "Narrows Across From the Log House Landing."

Dimmers used to carry a sketchbook and do all his work on-site, but has succumbed to the charms of a high-speed digital camera that enables him to "carry home with me the exact line of the horizon, approaching rain, the way light catches on an island." He made more than half of the 84 paintings especially for the book, where they complement but do not illustrate the essays.

"In painting, the inspiration comes from inside, but I really love that digital," he said. "It's hard to admit that because I feel I'm leaving Vincent [Van Gogh] and Claude behind, but more of my work is completed in the studio now."

Preservation celebrated

Mitchell, too, came to the river as a young man and has spent more than half of his 61 years in the valley. After growing up in Wayzata and graduating from Stanford, he took a teaching post in Stillwater and lived in a converted garage upriver. When his elderly landlords died, he and his wife bought the entire property with its spectacular views of the river.

While working as a technical writer, he's applied his background in geology to studying the cliffs of limestone formed millenniums ago at the bottom of an ancient ocean. He and his wife tap their maple trees in spring, watch the seasonal migrations, hike and canoe. All that is fodder for his musings and music. One jig, "The Pothole Grind," even has a descending chromatic pattern that he wrote as an audio imitation of "rock grinding on rock," a reference to the bizarre pits formed in granite by rocks swirling in glacial melt eons ago.

"There's a lot of valley lore in this," Mitchell said. "We want to highlight conservation and preservation of the river. When people visit us from other parts of the country, they say 'How did you do this? You're 30 miles from a half-million people, but it's almost undisturbed.' But that's hats off to those who set it up as a Wild and Scenic River and came through with the political will to actually accomplish that back in 1968." • 612-673-4431