Abstract: Apparatus for expelling air from between the sheets of stacks of superimposed sheets has a conveyor which advances successive stacks of a series of stacks along a horizontal first path from a stack assembling first station toward a second station. The conveyor employs a reciprocable carriage for one or more tongs which engage the front end portion of fresh stack at the first station and entrain the stack toward the second station. A roller is mounted in a conveyance for repeated movement with the conveyance along a downwardly sloping second path from a raised position above and away from the first path to a lowered position of engagement with successive stacks which are being advanced toward the second station.