The North and South both are losing the modern-day Battle of Gettysburg.

The monuments that make the rolling hills one of the world's largest outdoor museums are melting. Every time rain drips from the marble and bronze memorials, acid slowly but steadily washes away pieces of history."The marble ones are definitely on their way to destruction," said David Ballard, maintenance director at Gettysburg National Military Park. "You can wax bronze, but there isn't a . . . lot you can do about marble. The marble's just going to keep on fizzing away."

Only granite markers and monument bases seem immune. Across the sprawling battlefield, the effects of acid rain are obvious to even a casual observer. Brass plaques are stained and streaked with corrosion in shades of black, gray, green and white. Marble markers are badly pitted and misshapen.

On Cemetery Ridge, the high ground that Union forces held on the decisive third day of the 1863 Civil War battle, Ballard gestured helplessly toward an octagonal marble marker. Inscriptions had been chiseled on all eight sides, but only a stray letter or two remain visible.

"Whatever the heck was here, it's gone now. It's history," he said.

A short hike away, in the cemetery where Abraham Lincoln delivered the Gettysburg Address, is the first monument erected here. The Soldiers' National Monument, whose dedication took up much of the front page of The New York Times on July 2, 1869, is "probably the most endangered piece we have in the park right now," Ballard said.

The monument features a woman representing liberty atop a classical column, which rests on a pedestal. At the four corners of the pedestal, sculpted marble figures represent War, History, Peace and Plenty. Damage from acid particles in rain isn't apparent at first because of the stark beauty of the work viewed as a whole. A closer look reveals a missing toe here, a washed-out detail there.

Fighting the acidic effects of airborne pollution, according to a draft National Park Service report, is a losing battle:

"Only memories last forever. In time, metal corrodes and stone crumbles. What worries park managers at Gettysburg National Military Park is the speed with which our monuments to those honored dead are disappearing."