A Three-Circle Goniometer

Abstract

The object of goniometrical measurement is to determine in the simplest and quickest manner possible the geometrical constants of crystals and the indices of their faces. The ideal instrument should enable the observations to he conveniently and quickly made, and present them in such a form that the indices of the faces may be easily calculated. It is claimed for the tbrm of goniometer described in this paper that it does approximate to such an instrument. Before entering into the description it will not be out of place to discuss briefly the two types at present in existence, and point out their advantages and disadvantages.