In 1935, New York's Museum of Modern Art began one of the earliest institutional attempts to collect and preserve motion pictures, obtaining original negatives of the Biograph and Edison companies, and the world's largest collection of D. W. Griffith films. The following year, Henri Langlois founded the Cinémathèque Française in Paris, which would become the world's largest international film collection. For thousands of early silent films stored in the Library of Congress, mostly between 1894 and 1912, the only existing copies were printed on rolls of paper submitted as copyright registrations. For these, an optical printer was used to copy these images onto safety film stock, a project that began in 1947 and continues today. The Library hosts the National Film Preservation Board, whose National Film Registry annually selects 25 U.S. films "showcasing the range and diversity of American film heritage." The George Eastman House International Museum of Photography and Film was chartered in 1947 to collect, preserve and present the history of photography and film, and in 1996 opened the Louis B. Mayer Conservation Center, one of only four film conservation centers in the United States. The American Film Institute was founded in 1967 to train the next generation of filmmakers and preserve the American film heritage. Its collection now includes over 27,500 titles. In 1978, Dawson City, Yukon Territory, Canada, a construction excavation inadvertently found a forgotten collection of more than 500 discarded films from the early 20th century that were buried in and preserved in the permafrost. This fortunate discovery was shared and moved to the United States' Library of Congress and Library and Archives Canada for transfer to safety stock and archiving. However, to move such highly flammable material such a distance ultimately required assistance from the Canadian Armed Forces to make the delivery to Ottawa. The story of this discovery as well as excerpts of these films can be seen in the 2016 documentary film, "". Another high-profile restoration by staff at the British Film Institute's National Film and Television Archive is the Mitchell and Kenyon collection, which consists almost entirely of actuality films commissioned by traveling fairground operators for showing at local fairgrounds or other venues across the UK in the early part of the twentieth century. The collection was stored for many decades in two large barrels following the winding-up of the firm, and was discovered in Blackburn in the early 1990s. The restored films now offer a unique social record of early 20th-century British life. Individual preservationists who have contributed to the cause include Robert A. Harris and James Katz ("Lawrence of Arabia", "My Fair Lady", and several Alfred Hitchcock films), Michael Thau ("Superman"), and Kevin Brownlow ("Intolerance" and "Napoleon").