Keaton's character in "Sherlock Jr." is very much Buster's. Sherlock is cultivated, well dressed, virtuous, and fortunate. He is the forerunner of the well-heeled central figure of "Battling Butler" (1926), of the posh college son of the old captain in "Steamboat Bill, Jr." (1928), and, most of all, of Rollo Treadway, the augustly decorous hero of "The Navigator" (1924, but later than "Sherlock Jr."). In the beginning of his dream, The Boy is constantly buffeted by the alien film's overcutting by what Keaton once called to me "the homeless camera." (Like Renoir, among most other great directors, Keaton detested restless editing, and chose that audiences be able to watch in their own time what he was doing.) No sooner does Sherlock jump off a rock into water than it turns out to be snow. No sooner is he on a mountain than he finds himself on flat earth again, between two...