Question: What silent film adapted from the novel "The Clamsman" did Elmer Clifton appear in?
Context: Elmer Clifton (March 14, 1890 – October 15, 1949) was an American writer, director and actor from the early silent days.  A collaborator of D.W. Griffith, he appeared in "The Birth of a Nation" (1915) and "Intolerance" (1916) before giving up acting in 1917 to concentrate on work behind the camera, with Griffith and Joseph Henabery as his mentors.  His first feature-length solo effort as a director was "The Flame of Youth" with Jack Mulhall. Down to the Sea in Ships is a 1949 seafaring drama directed by Henry Hathaway, starring Richard Widmark and Lionel Barrymore.  The supporting cast includes Dean Stockwell, Cecil Kellaway, Gene Lockhart, and John McIntire.  This was a remake of the silent film version, directed by Elmer Clifton and starring Marguerite Courtot, Raymond McKee and Clara Bow. Daughters of the Night is a lost 1924 silent film melodrama produced and distributed by the Fox Film Corporation.  It was directed by Elmer Clifton with Alyce Mills as the lead actress. Six Cylinder Love is a lost 1923 silent film comedy produced and distributed by Fox Film and directed by Elmer Clifton.  It is based on a popular 1921 Broadway play and stars Ernest Truex from the play.  Also appearing in the film from the Broadway play were Donald Meek and Ralph Sipperly. Ten Laps to Go (King of the Speedway) is a 1938 American action/drama film directed by Elmer Clifton.  The film stars Rex Lease as a champion race car driver, Duncan Renaldo as his rival, and Muriel Evans as the romantic interest.  Former silent film star Marie Prevost has a small role in this film, which would prove to be her last; her death from self-inflicted malnutrition and alcoholism occurred less than six months later. Battling Jane is an American silent melodrama film released in 1918.  It was directed by Elmer Clifton as a vehicle for Dorothy Gish and included some patriotic overtones.  According to the Progressive Silent Film List at SilentEra.com, it is not known whether the film currently survives. Turning the Tables is a 1919 American comedy silent film directed by Elmer Clifton and written by Wells Hastings and Lois Zellner.  The film stars Dorothy Gish, Raymond Cannon, George Fawcett, Eugenie Besserer, Kate Toncray and Rhea Haines.  The film was released on November 2, 1919, by Paramount Pictures. Her Official Fathers is a 1917 American silent film that was co-directed by Elmer Clifton and Joseph Henabery.  It was produced as a starring vehicle for Dorothy Gish, and she may have directed some parts of the film. Nugget Nell is a 1919 American comedy silent film directed by Elmer Clifton and written by John R. Cornish.  The film stars Dorothy Gish, David Butler, Raymond Cannon, Regina Sarle, Jim Farley, and Bob Fleming.  The film was released on July 27, 1919, by Paramount Pictures.  It is not known whether the film currently survives. The Birth of a Nation (originally called The Clansman) is a 1915 American silent epic drama film directed and co-produced by D. W. Griffith and starring Lillian Gish.  The screenplay is adapted from the novel and play "The Clansman", both by Thomas Dixon Jr. Griffith co-wrote the screenplay (with Frank E. Woods), and co-produced the film (with Harry Aitken).  It was released on February 8, 1915.
Answer: The Birth of a Nation