In two other ways, however, Newton's system was less coherent. First, his explanation of "partial" reflection depended not only on the supposed forces of attraction between corpuscles and media, but also on the more nebulous hypothesis of "Fits of easy Reflexion" and "Fits of easy Transmission". Second, although his corpuscles could conceivably have "sides" or "poles", whose orientations could conceivably determine whether the corpuscles suffered ordinary or extraordinary refraction in "Island-Crystal", his geometric description of the extraordinary refraction was theoretically unsupported and empirically inaccurate.