The factories of motion-picture plants must be as delicately handled as any piece of intricate machinery. The temperatures of the various rooms, and also of the chemical baths used in the different processes, must be kept constant at certain points. Dust must be conspicuous by its absence, for the slightest particle of foreign matter may scratch and otherwise harm valuable film. The water used in the factory is an important item, and in cases where the regular supply has been shown to be inferior by chemical analysis, picture companies have often gone to the expense of drilling artesian wells to secure a pure supply. This was one of the moves made at a factory near Philadelphia, which boasts of its ability to turn out six million feet of positive film each week. Though most motion pictures made in the United States are produced in California, practically all of the factory work is done in the East. This is largely due to the fact that New York is the distributing point and business center. Not all of the companies known for their film productions have developing and printing plants. Many of the factories do the mechanical work for numerous other firms. In addition there are scores of companies doing only factory work and staging no pictures of their own. The picture is now all but ready for the market. Most of the directors take part in the assembling stage when the film is cut to its proper length, the subtitles inserted, and the finishing touches applied that make the picture ready to meet the eyes of the outside world. This is indeed one of the most important stages in the making of a picture, for here the work of the best of directors may easily be unalterably ruined, or, perhaps, a poorly staged picture made into a passable or even good one.