The original Archimedes Screw is used primarily for liquids, which is why it has to be installed on an angle, so the pockets of liquid are carried up it.   It's operating principle is gravity - each 'glob' of liquid stays in its 'pocket'.   (That would also work for a flowing solid like grain etc).    As a matter of constructional convenience some very large Archimedes screws e.g. in sewage works, are built with a rotating screw inside a fixed outer casing, but they still use gravity as the operating mechanism.   <br><br>This elevator looks very similar but the mechanism is quite different, it relies on relative motion between screw and casing and friction within the material being conveyed.    As Tom says, there is no difference whether the screw rotates or the casing rotates.   (An original Archimedes screw, with the screw fixed to the housing, would not work if stood vertically).<br>Fascinating though, I'd never seen or heard of this before.