Abstract: A method of propping fractures in a subterranean formation employing high-strength particles of propping agent having at least one passageway formed through each of the particles and having the usual high compressive strength and particle size range and density to enable emplacement in the fracture by hydraulic transport. Each particle has its at least one passageway formed substantially directly therethrough for increased permeability to flow of fluids from the subterranean formation. Particles may have any of the shapes that are commonly and economically available.

Abstract: A conveyor system for conveying trays containing articles has a positive drive for enabling extreme angles of inclination of the conveyor system. The conveyor system includes a plurality of spaced apart drive rollers, each having an annular row of teeth. The tray has a row of teeth that engages the teeth of the drive rollers. A drive system, which is preferably a belt having teeth on its outer surface, rotates the drive rollers. The drive rollers have cylindrical portions on each side of the teeth of lesser diameter than the teeth. The teeth on the bottom of the tray are located in a recessed channel, with flat surfaces on either side that engage the cylindrical portions. This enables the tray to be used also on a conventional conveyor system.