How exactly did it happen that billionaire philanthropist and arts patron Armand Hammer decided to give $1.15 million to the Corcoran Gallery?

He explained. He was sitting at his first meeting of the Corcoran's board of directors - just after his election to the board a few months ago - when he turned to Corcoran president David Lloyd Kreeger.

"I said to him, 'David, what does the museum need most?'" Hammer related last night at the gallery's 24th Annual Ball.

"Well, with a big sigh, David said, 'We're not competitive with the other museums. We charge admission and most don't.' I said to him, 'What would it take to change that?' David answered, 'A $75,000-a-year income.' I said, 'I think we can manage that.'"

Hammer laughed, recalling the conversation.

"Then, I said, 'Anything else you need?' And David said, 'Yes, the auditorium needs to be modernized.' I asked, 'How much will that take?' David said, 'A quarter of a million dollars.' I said, 'I think that can be corrected too.' And that's how we decided on the money."

Hammer laughed again. "I think it's more fun to give than to receive, don't you?"

The Corcoran Ball is one of Washington's premier annual balls, for which guests pay $100 per ticket. Hammer beamed throughout the evening as many came to thank him for the gift and gallery director Peter Marzio whisked him about for introductions. As of today the $1.50 admission fee to the gallery is dropped.

"Several people came up to me this evening," said Kreeger, "and said 'Why did you make the free admission effective Saturday? Why not tonight, so we wouldn't have to pay $100 to get in?' I told them, 'That's why.'"

About 1,100 people annually attend the ball, and all money is donated to the gallery and the Corcoran School of Art, according to the organizers of the ball.

Tickets are in such demand that a few people have to be turned away (balking a bit), according to organizers.

But one who chose not to come was Frank Stella, the acclaimed American artist whose work makes up the exhibit "Stella Since 1970," one of the two exhibits being previewed at the ball. The other is an exhibit of the work of late 19th-century French School artist Adolphe Monticelli.

"Stella doesn't like this sort of thing very much," one ball organizer said. "He came for the installation for the exhibit, and he'll be back for the official opening of the exhibit on Tuesday."

But it seemed everyone who came, ushered in by the pulsing beat of Brazilian street music (courtesy of local musician Bill Brown and friends who played during the cocktail hours), spent a giddy night hopping around from friend to friend.