Note 111 — Chapter IV · The Microscopic and Optical Characters of Minerals.
Reading edition
This test is only possible when suitable sections of the given feldspar in the rock section can be found. The method, however, can be used with great accuracy with the aid of some form of apparatus for properly orienting the section. See “Klein’s Apparatus for the Orientation of Thin Sections,” Sitzungsber. Berlin. Akad., 1895, 1151; (also in N. Y. Acad. Sci., Vol. XVI, p. 51, 1897); and Von Federov’s “Universal Table,” Zeit. für Kryst, etc., Vol. XXV., p. 351.