Inside the Cathedral of the Madeleine, the stained glass windows are loose. Years of dirt have dulled the brilliant colors in murals depicting religious scenes. Worshipers have worn grooves in the floor between rows of pews.

A campaign to raise $6.3 million to restore the interior of the 80-year-old Catholic cathedral was announced Sunday, a project that is expected to take until 1992 to complete.The fund-raising drive will be headed by John W. Gallivan, chairman of the Kearns-Tribune Corp.; Jon M. Huntsman, chairman of Huntsman Chemical Corp.; and Ian M. Cumming, chairman of Leucadia National Corp.

The building, which was designated a National Historic Monument in 1971, is more than the state's principal Catholic church, according to Bishop William K. Weigand of the Catholic Diocese of Salt Lake City.

"It is also an important architectural, historic and artistic treasure of both Salt Lake and the state of Utah," Weigand said, adding that it serves too as "a symbol of the diversity of Utah's history."

Ground was broken for the cathedral in 1899, but it was not completed and dedicated for another 10 years. It took several more years for the plain, plaster-finished interior to be decorated.

The work done then still stands today, but time has taken its toll. During a tour of the cathedral, the Rev. M. Francis Mannion points to one mural that has been cleaned.

The reds and other colors in the several-foot-high figure of an Italian archbishop stand out in sharp contrast to a nearby mural of Old and New Testament saints.

The murals are covered with layers of soot from a coal furnace used in the cathedral for decades as well as the pollution that has come in from windows opened to cool the cathedral in warmer months.

Those windows, the bottom panels of the massive stained glass windows that line the cathedral, are in danger of collapsing, the Rev. Mannion said. Pollution has loosened the lead in the windows as well as their frames.

Part of the restoration project will include the installation of air conditioning. Besides making the cathedral more comfortable for worshipers, the cool air will allow the windows to be sealed, keeping out pollution.

Canvas installed on the walls and draped across the ceiling to improve the acoustics of the cavernous building will be removed as part of the restoration, but the Rev. Mannion said the interior will look the same.

"We want to preserve every element in the building if we can," he said. "There will not be editing of anything you see. Even when the canvas is removed, the ceiling will appear as it does now."

The various designs painted on the canvas, including a group of angels on the ceiling, will be reproduced on the rebuilt ceiling and the exposed walls, the Rev. Mannion said.

No no date has been set for the restoration project to start, but once it does, the cathedral will remain open as much as possible for daily Masses, services and community events.