  Modern advances in polarized beam control should make it possible to
accurately measure Stern-Gerlach (S-G) deflection of relativistic beams. Toward
this end a relativistically covariant S-G formalism is developed that respects
the opposite behavior under inversion of electric and magnetic fields. Not at
all radical, or even new, this introduces a distinction between electric and
magnetic fields that is not otherwise present in pure Maxwell theory.
Experimental configurations (mainly using polarized electron beams passing
through magnetic or electric quadrupoles) are described. Electron beam
preparation and experimental methods needed to detect the extremely small
deflections are discussed.
