A line shaft is a power-driven rotating shaft for power transmission that was used extensively from the Industrial Revolution until the early 20th century. Prior to the widespread use of electric motors small enough to be connected directly to each piece of machinery, line shafting was used to distribute power from a large central power source to machinery throughout a workshop or an industrial complex. The central power source could be a water wheel, turbine, windmill, animal power or a steam engine. Power was distributed from the shaft to the machinery by a system of belts, pulleys and gears known as millwork……wikipedia
Prior to the advent of practical electric motors, industrial buildings – factories, workshops, etc – would have one big engine (or sometimes a waterwheel) on the ground floor or in the basement, connected to all machinery in the building via an elaborate system of flat leather belts or ropes and overhead shafts and pulleys. The line shafts would turn continuously all the working day, and each machine would have a clutch to connect it to the drive as needed.