A silent film is a film with no synchronized recorded sound, especially with no spoken dialogue. In silent films for entertainment the dialogue is transmitted through muted gestures, mime and title cards. The idea of combining motion pictures with recorded sound is nearly as old as film itself, but because of the technical challenges involved, synchronized dialogue was only made practical in the late 1920s with the perfection of the Audion amplifier tube and the introduction of the Vitaphone system. After the release of The Jazz Singer in 1927, the “talkies”, also known as sound film or talking pictures became more and more commonplace. Within a decade, popular widespread production of silent films had ceased, hence production moving into the sound era. A September 2013 report by the United States Library of Congress announced that a total of 70% of American silent films are believed to be completely lost. Many early motion pictures are lost because the nitrate film used in that era was extremely unstable and flammable. Additionally, many films were deliberately destroyed because they had little value in the era before home video. Though most lost silent films will never be recovered, some have been discovered in film archives or private collections. Discovered and preserved versions may be editions made for the home rental market of the 20s and 30s that are discovered in estate sales, etc. In 1978 in Dawson City, Yukon, a bulldozer uncovered buried reels of nitrate film during excavation of a landfill. Dawson City was once the end of the distribution line for many films. The retired titles were stored at the local library until 1929 when the flammable nitrate was used as landfill in a condemned swimming pool. Stored for 50 years under the permafrost of the Yukon, the films turned out to be extremely well preserved. These films are now housed at the Library of Congress. The degradation of old film stock can be slowed through proper archiving, and films can be transferred to digital media for preservation. Silent film preservation has been a high priority among film historians