Harold Lloyd, the bespectacled film artist who hung precipitously from a clock more than 20 stories above downtown Los Angeles in "Safety Last" (1923), always has been in third place in the silent movie sweepstakes, behind Charlie Chaplin and Buster Keaton. Although he made more films than they, and effortlessly made the transition to sound, Lloyd remains more obscure than his two contemporaries. Even British film historians David Gill and Kevin Brownlow, the excellent producing and directing...