IN IDLE HOURS at the beach, the woman and her children wandered. In her ruffled Victorian gown, she could be seen lounging with a young daughter on a huge orange pillow with tassels, on the dunes above the water. Or picking flowers on the dusty path among the sea grasses and bayberry bushes. At the breakwater one gentle summer morning, she and the other women, in their gowns and bonnets and parasols, alighted on the sand like colorful dragonflies.

She seemed blissfully unaware of the man who followed her with easel and paints. But her husband, William Merritt Chase, was painting a turn-of-the-century suite, the joyful summer song of his career. "William Merritt Chase: Summers at Shinnecock, 1891-1902" opens at the National Gallery on Sunday, and it sounds just the right wistful note on which to end the season.

Chase went with his family to the eastern tip of Long Island to run a school for painters -- America's first important school of open-air painting. He was teaching the new Impressionism he had been studying and collecting, although he was not a total convert. He admired and collected the work of Berthe Morisot, for example -- and Chase's exhibit is a grace note to her retrospective here at the Gallery. But he thought Velasquez was the ultimate. One can detect Whistlerian touches in his work as well, in his paintings of the dark-haired Alice, sitting in the studio in a kimono or chatting with a neighbor come to call.

He paints a picture of domestic tranquility -- from a distance. His children are unspecific, just everywhere. Rather than personalities, he conveys atmosphere, the soft breezes of halcyon days. WILLIAM MERRITT CHASE: SUMMERS AT SHINNECOCK, 1891-1902 --

Opening Sunday in the National Gallery of Art's East Building, through November 29.