"I made more than 100 films. A great many of them have been lost, of course," said Lillian Gish. Her soft voice belied the fact that she was speaking on a literally explosive issue.

The famous actress, her gray hair set off strikingly by a large black hat, still had the complexion and beautifully fine bone structure at 83 years of age that she had when she made "Birth of a Nation" 65 years ago. Her film career has spanned most of the 20th century.

Escorted by George Stevens, director of the American Film Institute, Lillian Gish testified yesterday at a hearing of the House Government Information and Individual Rights Subcommittee. The subject was millions of feet of old film, owned by the federal government, which are a national treasure but also a menace to health and safety.

The films are printed on cellulose nitrate, which becomes highly explosive as it deteriorates with age. Twice in the last two years, there have been serious fires in the National Archives vaults in Suitland where the films are stored, and Prince George's County Fire Chief M.H. Estepp yesterday told the subcommittee that their storage in a populated area is "a threat to public safety."

Stevens, while admitting that the film can be a fire hazard, insisted that it has incalculable artistic and historic value. "We should not treat it like waste from Three-Mile Island," he said.

Lost in the two Suitland fires were 12.6 million feet of newsreel film-part of a cache totaling 28 million feet that had been donated to the National Archives by Universal Studios.

A third building in Suitland houses films owned by the Library of Congress, much of whose total of 70 million feet is stored at Wright-Patterson Air Force Base in Dayton, Ohio. So far, the Library of Congress has not been hit by a fire-but it has moved all nitrate films out of its downtown buildings since the fires in Suitland.

Preserving the old films and eliminating the hazard is "essentially a financial problem," Stevens said. "The only time it really comes to our consciousness is when we have a fire or something bordering on a catastrophe." He estimated that it would cost between $15 and $30 million to transfer all existing nitrate film to modern safety film.

The Archives and the Library of Congress are hard at work on such transfers at a cost of about 15 cents per foot. They try not to duplicate one another or other organizations (such as the museum of Modern Art) engaged in similar work.

The AFI hopes to locate and preserve the nitrate film (estimated at 30 million feet) which is in private hands and in danger of being lost forever either through slow deterioration or more spectacularly through spontaneous combustion.

National Archivist James B. Rhoads told the subcommittee the Archives has examined the film in its possession for historic value and has decided to preserve about 7 million feet. Transfer of this material to safety film should be completed by the fall of 1980, he said. The Library of Congress is setting up facilities in Dayton and expects the transfer of another 70 million feet to take about seven years.

Chief Estepp said he thought the transfer of nitrate prints to safety film would solve the problem. "Do that," he added, "and do it away from Suitland."

When subcommittee chairman Richardson Preyer (D-N.C.) asked him whether he thought the film could be kept in Suitland with better storage facilities, the firefighter retorted:

"Would you like to have several cases of dynamite stored in your neighborhood?"

Earlier, Rep. Richard L. Ottinger (D-N.Y.) had said that the vaults in which some old films are stored "turn thousands of reels of film into virtual bombs."

Chief Estepp agreed. In the latest fire, on Dec. 7, 1978, he said, 14 firemen were hospitalized for burns or the inhalation of toxic smoke, and more than 100 families and businesses had to be evacuated from the area.

Before hearing testimony, the subcommittee saw samples of the kind of material that is being preserved. Newsreels showed dramatic confrontations between strikers and police during a Depression-era dock strike in San Francisco which escalated into a general strike and declaration of martial law.

There were clips of historic figures: Thomas Edison, Luther Burbank and Henry Ford chatting; John D. Rockefeller grinding a movie camera; William Jennings Bryan confronting Clarence Darrow; Bernard Shaw joking about himself, and Will Rogers kidding Franklin D. Roosevelt.

Adolf Hitler marched menacingly across the screen, and Bruno Hauptmann was cross-examined about the Lindbergh kidnapping. A very young Rep. Richard Nixon was shown talking about the Red Menace, and there was a hilarious scene of Bess Truman christening a new aircraft with a champagne bottle that refused to break.

Recalling the Truman scene in his questioning of Lillian Gish, chairman Preyer said it was an experience "beyond words."

Gish agreed. "Great historians from the beginning of time have tried to make history visual with words," she said. "And then we come along in the 20th century and we have a visual record - beyond words. Everything that has happened in the last 100 years is on film. . . . It's powerful history, and we should preserve the living record of it."

Later, in a impromptu press conference, she was asked about whether she thought all old film should be preserved.

"Goodness, no," she said, "but many of the newsreels are important - the history, the wars, everything good and bad. Someone said, "The only thing we can learn from history is that we can learn nothing from history.' Well, up to now, we've had history in words. Now, we can have history in action, and maybe we can learn from that." CAPTION: Picture, Lillian Gish; by James K.W. Atherton - The Washington Post