The latest pieces to leave the Westervelt-Warner Museum of American Art, at 8 on Tuesday morning, include a rare historical work by Edward Hopper, Daniel Garber's luminous 'Tanis,' one of Mary Cassatt's Denise paintings and a landscape that overflows the cover of the book 'An American Odyssey.'

'An American Odyssey' is the coffee-table book about Jack Warner's pursuit of what's been called one of the finest privately held collections of American art in the world. Frederic Edwin Church's airy 'Above the Clouds at Sunrise' illuminates its cover.

The other titles being removed today are Hopper's 'Dawn Before Gettysburg' and Cassatt's 'Denise in Hand Mirror.'

With the earlier removal of such keystone works as Asher B. Durand's 'Progress (The Advance of Civilization)' and Thomas Cole's 'The Falls of Kaaterskill,' this marks the loss of 25 paintings considered core to the collection.

'As if many of the seminal works haven't been taken already, (‘Above the Clouds at Sunrise' is) the one you most quickly associate with the Warner collection,' said Graham Boettcher, William Cary Hulsey Curator of American Art at the Birmingham Museum of Art, and a frequent visitor to and student of the Westervelt-Warner Museum.

The Westervelt Co., owner of the artworks, declined to comment. Of 42 paintings previously removed this year, 29 go on auction at Christie's on May 18. The others presumably have been or are being sold privately.

The Westervelt Co. is taking advantage of a law under which it can make greater profits by selling art, considered a non-core asset, in 2011. In past weeks, the company has declined to discuss how works have been selected, or what dealer is handling the sales.