IT is cyclone time on the Mississippi River during the making of the movie "Steamboat Bill Jr." Silent screen comedian Buster Keaton is busy bracing against those 1928 wind machines.Buster wore a sober, stone face under his trademark porkpie hat - he looked slightly sad through all the laughter his movies inspired. The melancholy eyes, eyelined against the whitened face with tight lips, firmly stared down all those cyclones, falling rocks, runaway cars, and general mayhem only a silent-film comedy can produce. The old silents are usually seen these days at film festivals, on video, and in museums. But if you happen to be strolling down North Fairfax Avenue in Los Angeles you will come upon the Silent Movie Theater. Nothing but silents. In keeping with the silent period, an usher will show you to your seat. For moviegoers of today who do not know what an usher is, may I explain. In the silently good old days, an usher was someone who was paid about $10 a week (probably less) to dress up in a uniform and flashlight you to your seat. Imagine! While we are in the spirit of such a visit, we ask the very tall lady in front of us, in our most polite manner, to please remove her huge feathery hat. And then we settle back to quietly munch our popcorn. Of course we will not engage in loud comments with our partner, all the better to enjoy the keyboard accompaniment as we watch Buster Keaton performing one of his great sight gags. When Buster came up with the idea for this particular stunt, nearly all of his staff rebelled. They thought it was too dangerous, too much flirting with death. Buster would stand in a street in River Junction, supposedly mesmerized by the storm, and the front wall of a house would come down on top of him like a fly swatter. The gag was that an opened second-story window would save him from being crushed. His window of opportunity, you could say. Stubborn Buster went ahead and ordered the cameras in place. The director couldn't bear the whole thing and retreated to his tent. The two cameras had to be supported with concrete as the wind machines roared to cyclone level. The cameramen had to hand-crank their cameras steadily at just the right number of frames per second. Buster got to his carefully marked spot, nodded "ready," and with screeching and wrenching, down came the front of the house. An awful moment! And so the wreckage settles around our hero, the Keaton face calm, sublime, and oblivious. He steps out of the window frame, not realizing what has happened until a step or two later. His face may look calm, but his feet are terrified. Fear and panic race on to the next crisis. SCENES like this are masterpieces of teamwork. Rudi Blesh, in his biography "Keaton," quotes Buster: "The clearance of that window was exactly three inches over my head and past each shoulder. And the front of the building - I'm not kidding - weighed two tons. It had to be built heavy and rigid in order not to bend or twist in that wind.... First time I ever saw cameramen look the other way." The story we are watching is a melodrama about rival riverboat owners, our hero the son of one, our heroine the daughter of the other. The hero's father's craft is old and creaky-leaky, while the heroine's mean father's steamboat is new, powerful competition. Dramatic complications, plus many more sight gags, transform our hero from wimp to man of action. He wins his father's hitherto withheld respect, humiliating the opposition and pulling everybody out of the wildly raging waters. At the last moment he saves the minister, who we know will perform the inevitable wedding ceremony. The wind machines turn off. All is well. The great silent stars had complete control over their films. Chaplin, for example, was an independent producer, while Keaton's career went downhill after he lost control over his pictures. Keaton was a master of every phase of picture-making. He literally took cameras apart, loving all the technical details. While he understood and used the photographic tricks of the time, he wanted his stunts to be as "real" as possible and would shoot straight through the action in one take. He respected the camera, w orked for it, and had it work for him. Well, the end of "Steamboat Bill Jr." has come. Keaton rescues the minister, looking as sober and wary as ever. Even wedding bells cannot quite affect the melancholy eyes. Lights up, the show is over. The lady puts on her big feathery hat, and our usher with the flashlight awaits the next audience.