As far as ancient films are concerned, "The Miller and the Sweep" is noteworthy for being an early British comedy and particularly for being a forerunner of later chase films and slapstick comedies. The chase film was one of the more important early film genres because of its influence on the development of continuity editing. "The Miller and the Sweep" and another early chase comedy "Chinese Laundry Scene" (1894), which was made by the Edison Company and based on a vaudeville act, consist of only one shot and scene, though. The chase film's effect on multi-shot films seems to have began with "Stop Thief!" (1901), which was made by Smith's friend and neighbor in Brighton-Hove, James Williamson. The chase comedy, it seems, became popular after "Personal" (1904)--leading to the popular Pathé chase comedies, then the Keystone films and eventually the chases in Buster Keaton's movies.
In its brief minute-or-so running time, "The Miller and the Sweep" begins with some messy knockabout slapstick between a miller with his bag of flour and a chimneysweeper and his bag of soot. Their wrestling then turns into a very brief comedic chase. None of the direction is particularly exceptional, as the episode takes place entirely before a stationary camera and within a limited 52 feet of film. In the background, a flourmill serves as a landmark. According to John Barnes ("The Beginnings of the Cinema in England 1894-1901"), it was the Race Hill Mill, located in Brighton.
In a larger context, "The Miller and the Sweep" is not an especially important film, and it's rather awkwardly constructed even for 1897, but the filmmaker who made it, George Albert Smith, was one of the more important pioneers of early cinema. Many of his films after this one (which was very early in his career), in ways, surpass anything else made by others (including the more acclaimed Edwin Porter and Georges Méliès), as Smith experimented with editing, some of the earliest multi-shot films, trick effects, close-ups and scene dissection.
On a further historical note, thanks to the comparatively detailed records of Smith's film production, Barnes also mentions that Smith first failed to produce a version of "The Miller and the Sweep" on 24 June 1897. This film is his second and successful try at the subject, filmed on 24 September 1897. Additionally, the following year, Robert W. Paul remade this film with the same title, so it must have been rather popular. In the Movies Begin series, it's claimed that the subject had a tradition in comic strips and stage acts.