BOSTON, MASS. -- If there were any doubts that Winslow Homer is America's greatest artist, they should be laid to rest by the splendid retrospective now on an East Coast tour. The first comprehensive Homer exhibition in nearly a quarter century, including just about all of the loanable works that have become icons of American art, underlines the magnificent versatility, technical skill, scope, scale and sheer beauty of the artist's achievements. "Winslow Homer" is not to be missed.

Since the last overall exhibition of Homer's work at the Whitney Museum of American Art in 1973, several shows focusing on periods and themes of his career have added useful insights into the painter's life and oeuvre. Much of the analysis and current research is synthesized in the current exhibition and the outstanding catalogue that accompanies it. All this indicates that Homer was a more complex and interesting artist than many have thought - and suggests why this quintessential Yankee continues to intrigue scholars and laymen alike.

Homer fans owe a great debt of gratitude to Nicolai Cikovsky, Jr, and Franklin Kelly, the National Gallery of Art's curators of American and British paintings who organized the show and prepared much of the catalogue. Utilizing approximately 180 paintings, watercolors and drawings, "Winslow Homer" offers a broad vision of Homer's output. Arranged in rough chronological order, the works appear in thematic groupings that include depictions of the Civil War; genre scenes celebrating the rural and outdoor life; heroic images of life on or near the sea; powerful Maine seascapes and the somber, visionary works of his final years.

Following its opening at the National Gallery, the exhibition is on view at the Museum of Fine Arts, Boston, through May 26 and will be at the Metropolitan Museum of Art, June 20-September 22.

At the Metropolitan Museum, the traveling show will be complemented by "American Printmaking 1860-1900: Winslow Homer and His Contemporaries," consisting of lithographs, wood engravings and etchings from the museum's collection by artists active in Homer's time, such as Edwin Austin Abbey, John George Brown, Stephen Parrish, Charles Adams Platt, Thomas Moran and J. Alden Weir.

The 420-page exhibition catalogue, written by curators Cikovsky and Kelly with contributions by Charles Brock and Judith Walsh, is illustrated with 286 color plates and numerous black and white images. It includes quotations from Homer's contemporaries and new scholarship to provide a broad view of the quality and significance of his accomplishments. Published by the National Gallery with the support of the Henry Luce Foundation and distributed by Yale University Press, the catalogue is a bargain at $25 (softcover) and $60 (hardbound). It belongs in the library of every American art lover.

A tenacious, reticent, independent New Englander with enormous artistic talent, a restless intelligence and a fervent affection for nature, Homer (1836-1910) was born in Boston and raised in nearby Cambridge. His father, an outgoing sort, was a merchant/entrepreneur and his mother, an accomplished amateur watercolorist.

Based on early demonstrations of drawing ability, Homer, as a teen-ager, became an apprentice to a Boston lithographer. He took up freelance illustrating at 21, achieving some success with wood engravings for popular magazines. In 1859 he moved to New York to be nearer to publishers who commissioned illustrations. There, he executed numerous images of urban life for periodicals while studying painting at night. For a time he maintained a studio in the old University Building on Washington Square.

Homer first came to national attention during the Civil War with his accurate, vivid sketches of life at the front. As an artist-reporter he accompanied the Army of the Potomac in the Peninsula campaign in Virginia, observing camp life and some combat. While Homer drew a few traditional military scenes, such as bayonet and cavalry charges, he mostly depicted the utterly unheroic day-to-day activities of ordinary soldiers behind the lines.

Homer's Civil War drawings and paintings showed not only accurate down-to-earth details of soldiers' everyday lives but touched on themes of isolation, morality and nature's adversity, which he dealt with in his later art. To this day, these wartime images remain powerful reminders of this nation's most tragic conflict.

Homer's standing in the art world was firmly established by the mid-1860s when he was elected a full academician of the National Academy of Design. In 1866 he made his first trip to Europe, where he viewed "Prisoners" at the Exposition Universelle in Paris, toured the Louvre and painted a score of somber landscapes. That year in France appears to have had little impact on the man or his art.

Back in New York, the ambitious artist ranged around the Northeastern states, creating genre scenes of rural life, leisure activities and young people on farms and at the seashore. While hardly profound, these are sunny, accomplished images of a changing America - the passing of a carefree way of life.

In the early 1870s Homer stopped doing magazine illustrations to concentrate on oil paintings and take up watercolors. His early watercolors included cheerful portrayals of youngsters around the harbor in Gloucester, Mass., and farm girls in bonnets. The exhibition's scope permits viewers to trace the evolution of Homer's watercolors from these direct appealing first works to the more sophisticated, often intense, images of his later years.

As a result of travels in Virginia during Reconstruction, Homer made a series of paintings of the life of African-Americans in the period after emancipation and the end of the war. With the exception of a couple of earlier inexplicable examples, he avoided the degrading stereotyped depictions of blacks frequently employed by his contemporaries, and he painted African-Americans with empathy and understanding.

Although always a reserved retiring person, Homer, during his two decades in New York City, worked hard at his craft, exhibited regularly, joined clubs and hobnobbed with fellow artists and potential patrons. One friend said he had the usual number of love affairs.

Around 1880, the formerly sociable Homer became more standoffish and irascible. His family always said an unhappy love affair caused him to turn his back on society. For whatever reason, Homer lived by himself that summer on lonely Ten Pound Island in Gloucester Harbor. Experimenting with styles and techniques, he created some of the finest watercolors of his career, primarily views of sailing ships.

For my money, the magnificent watercolor "Sunset Fires" (1880), with a sailboat dramatically outlined against a fiery harbor and sky, is the unexpected highlight of the exhibition. This 9¬ by 13Ö inch gem is in the collection of the Westmoreland Museum of Art in Greensburg, Penn.

The following spring Homer suddenly took off for England, where he spent 15 months in Cullercoats, a fishing village on the stormy North Sea. There, his art underwent significant changes. His slim American lasses at leisure were replaced by full-bodied, robust fisherwomen pitching in to help their men battle the perils of the sea. Conveying new artistic weight and power, these serious Cullercoats works reflect humankind's battle for survival against the forces of nature, a subject to which the artist returned often for the remainder of his career.

Upon his return to New York, Homer closed his studio and moved to his family's summer retreat in Prout's Neck, a rocky promontory just south of Portland, Me. On land in the Homer compound overlooking the ocean, he renovated an existing stable to serve as his year-round home and studio and spent the rest of his life face to face with the mighty Atlantic Ocean.

Those interested in further insights into Homer's life should consult Winslow Homer at Prout's Neck, written 30 years ago by Philip C. Beam, a Bowdoin College art professor. This invaluable study, based on interviews with neighbors who actually knew Homer, reveals the artist's human side and lays to rest myths about his misanthropy.

A dedicated outdoorsman, avid fisherman, animal lover and early conservationist, Homer is this country's finest artist of fish and wildlife. In pursuit of his passion and as a break from his Maine routine, for years the artist made annual visits to the North Woods Club in the Adirondacks where he executed splendid watercolors. Seeking larger fish and more adventure, Homer traveled into central and later northern Quebec, up the roaring Saguenay River, where he particularly enjoyed observing, catching and painting ouananiche - landlocked salmon - famed for their superb colors and fighting qualities.

In his later years, seeking to escape Maine's harsh winters Homer sojourned in the Caribbean and Florida, where he fished, did some watercolors and loafed as the spirit moved him. Out of these happy visits came not only brilliant images of tropical fish and patient anglers but sun-splashed evocations of white-washed walls and exotic vegetation in the Bahamas.

For fish and wildlife pictures Homer worked almost exclusively in watercolor because of the portability of equipment and the medium is best suited to capturing fleeting scenes. The pictures in this exhibition make clear why he had such an influence on the history of watercolor. Before Homer - and J.M.W, Turner in England - watercolor had been used by artists mainly for studies and sketches. Homer's masterful finished watercolors elevated them to the status of high art, transforming the course of American art.

Homer is probably best known today for the epic seascapes he executed at Prout's Neck in the 1890s. After countless hours observing the ocean in all kinds of weather, in all seasons and hours of the day, he distilled his knowledge in a number of monumental oils in which people were eliminated and the focus was on the eternal clash between sea and shore. The force of the wave, the solidity of the rock, the shock of the collision have never been better recorded.

Often ill toward the end of his life, Homer thought increasingly about his own death. In "Right and Left" of 1909 he depicted two ducks at the instant when a hunter in the distant boat has fired at them with his double barreled shotgun. The blast is indicated by a puff of smoke and flash of red.

"Right and Left" culminates the aging painter's investigations of the moments when life and death hang in the balance and his musings about his own mortality. He died a year later in his beloved Prout's Neck studio and was buried in the Homer family plot in Mount Auburn Cemetery in Cambridge, Mass.

Showcasing the unparalleled breadth of Homer's oeuvre, his mastery of oil painting and watercolor, his wide range of subjects, his keen observation of life and nature and his sensitivity to the great issues of his day, this grand Homer retrospective confirms his preeminent standing among American artists.

The vitality, freshness of vision, largeness of form, resonant color harmonies, superb decorative values and the elemental themes underlying his art make Winslow Homer's works as alive today as when he created them a century ago.