1. A stiff breeze riffles the brush.

2. It riffles the torn papers on desks daubed with red, white and blue paint.

3. Any alteration of water clarity or silting over rock and riffles can be expected to be detrimental.

4. With the agitator (1) rotating, fine particles of the material to be separated and having a specific gravity higher than a certain figure are captured in 'dead-zones' created behind the riffles and move down through the fluid to a discharge tube (19).