When money was being raised for the Daniel Libeskind-designed addition to the Denver Art Museum, oil zillionaire Frederic C. Hamilton, then chairman of the board of trustees, met the challenge by throwing $26 million into the pot. That's why the addition is called the Frederic C. Hamilton Building. But Hamilton wasn't done. A couple of months ago, he announced that he was turning over his collection of impressionist paintings to the DAM, including pieces by Cézanne, Monet, Manet and all the other big names. The Hamilton paintings were on display in Nature as Muse when the announcement was made, allowing everyone to understand how the bequest beefs up the museum's impressionist holdings and makes the DAM a major repository of the style in the American West.