An Improved Orientation Stage for Microscopic Optical Crystallography

Abstract

A PRELIMINARY description has been published¹ of an accessory to the polarizing microscope embodying novel principles which allow a full range of optical qualitative studies, quantitative measurements, and refractive index determinations to be carried out simply and accurately on diverse crystalline material such as well-developed crystal individuals, fragments, and sectioned aggregates. The crystal occupies the centre of a glass sphere, formed of two easily detachable segments, which has complete freedom of rotation about its centre, thus allowing the conoscopic or orthoscopic phenomena to be observed for any desired direction of transmission within the crystal. Morphological and optical data representing axial or planar directions within the crystal, as, for example, the optic axes, are adjusted to the cross-hairs and recorded by an automatic plotting device in their equivalent positions on the outer surface of the sphere. Simple great circle and polar relationships only are involved, and the angular data plotted upon the surface of the sphere is measured on a vernier to one-tenth of a degree, on the periphery of a single horizontal graduated circle.