Abstract: An open-cycle air-conditioner for compressing and expanding gas with heat rejection for cold production and more particularly to improved means for carrying out thermodynamic cycles in open cycle systems using an internal, stationary, porous body as a thermal capacitor.

Abstract: Method and apparatus for comminuting a tree stump in its entirety while still rooted in the ground, utilizing a large, heavy cylindrical roller or drum rotating at high speed and having cutters mounted on a peripherical surface thereof for engaging and comminuting the stump from the side thereof. The roller is journaled for rotation about a horizontal axis in a carrier attached to the front end of a heavy four-wheel vehicle which is driven hydraulically over the ground surface from a selfcontained power source such as an internal combustion engine. The hydraulic system which drives the vehicle also includes a hydraulic motor mounted on the carrier for rotating the roller. The roller, through the carrier, is mounted to the vehicle frame for swinging movement in a vertical plane relative to the ground and a hydraulic cylinder included in the hydraulic circuit is provided for effecting said vertical swinging movement.