In 1923, Duncan and Marjorie Phillips sailed to France in June to relax and to shop for art. Soon after arrival they attended the party of a Frenchman who had invested heavily in Impressionist paintings, and on that evening they saw for the first time Pierre Auguste Renoir's "The Luncheon of the Boating Party." Within six months they had acquired what is widely regarded as the painter's most ambitious work for the then-staggering sum of $125,000.

Since it arrived at the Phillips home, now the Phillips Collection, at 21st and Q NW, "The Boating Party" has traveled from there only three times: to the New York World's Fair in the late 1930s; to the Louvre in 1958 (the first time it had ever been shown publicly in France); and now, since July 4, "The Boating Party" has hung in San Francisco's Palace of the Legion of Honor. It's the piece de resistance in the 75-painting show the Phillips is sending to four cities over the next 18 months to raise funds for the collection.

To ensure the safety of so famous a work, the San Francisco museum has taken the extraordinary step of hiring a guard to stand by it during public viewings. And there are numerous guards as well within the crowd.

Also there are "shin barriers," ropes hung on metal posts, to prevent anyone from getting any closer than 4 1/2 feet from any of the works. "I'm 6-feet-3, with long arms and I can't reach them," says San Francisco curator, Thomas Lee, who mounted the show. The crowds vary from 300 to 500 an hour, he says.

Such security precautions as the shatterproof Plexiglas placed on Leonardo's "Mona Lisa" when it visited the National Gallery in 1962 were not considered for the Renoir. "That would be particularly unfortunate for so lush and gorgeously textured a work," observes Lee.

Is the public adoration of "The Boating Party" justified? Lee replies, "Well, I have always said that Monet is the greatest Impressionist painter, but that this is greatest Impressionist painting.