By optics or sight; with reference to optics.
<-- def. of Optically active needs rewriting -->
Optically active, Optically inactive Chem. Physics, terms used of certain metameric substances which, while identical with each other in other respects, differ in this, viz., that they do or do not produce right-handed or left-handed circular polarization of light. -- Optically positive, Optically negative. See under Refraction.
© Webster 1913.