Cross polarization is "regular" polarization. You place one polarizer between the light source and the slide, the other between the slide and your eye or camera. To produce the polarization effect you rotate either of the polarizers until its so-called "optical slits" are oriented perpendicular to those of the other polarizer. You know when this orientation is achieved because the direct light from the light source is almost entirely extinguished, creating a dark field. If there are any birefringent materials present, they will glow brightly against the dark background.
Histonet mailing list