 Close shots of a railway train underway: track racing underneath, steam escaping, cars coupling, gears ratchetting, signals changing. The train reaches a lift bridge which must rise to allow a merchantman to pass below... Bridge section and counterweight move choreographically. The balletic motion of beam relative to girder creates an elegant, abstract expression of the precision of technology... The lift operator sets the bridge to the correct height then returns it to the original position. The train carries on its way, passing prosaically over the ship canal.