Abstract: A fiber sheet manufacturing apparatus, such as a paper machine, is described, including a rotary through dryer for drying the sheet material on the same foraminous conveyor where it is initially formed. The dryer is provided with a plurality of separate vacuum chambers circumferentially spaced within the foraminous dryer drum, which are each in registration with a different one of a plurality of sources of hot air outside of the drum. The hot air is transmitted through the sheet material and the conveyor into the vacuum chambers to dry the sheet material. Each of the vacuum chambers and the hot air sources is independently controlled to provide different temperatures and vacuum pressures for more efficient and versatile operation. The air is transmitted from the vacuum chambers out of the drum through their separate exhaust conduits extending through the end of the drum and spaced from the drum support bearings.