Published online by Cambridge University Press: 14 March 2018
In a group of earlier publications details have been given of the application of multiple-beam interference methods to the study of mica. The characteristic structure of this mineral is exhibited by the Fizeau fringes which are produced when one side of a mica slip is silvered and placed against a similarly coated optical flat. The fringes show that the surface is violently contorted and crossed by cleavage steps, the heights of which appear to be integral multiples of the crystal-lattice spacing perpendicular to the basal plane of cleavage. If, however, a mica slip (thickness circa 1/100 mm.) is silvered on both sides then fringes of a totally different appearance are observed. It is frequently found that, despite the distortions on the surface, the Fizeau fringes are large areas of uniform illumination bounded by cleavage ‘lines’.
page 137 note 1 Tolansky, S., Proc. Roy. Soc. London, Ser. A, 1945, vol. 184, p. 51 ; ibid., 1946, vol. 186, p. 261 ; Phil. Mag., 1946, ser. 7, vol. 37, p. 390. [M.A. 10–134.]CrossRefGoogle Scholar
page 139 note 1 Tolansky, S., Proc. Physical Soc., 1946, vol. 58, p. 654. [M.A. 10–134.]CrossRefGoogle Scholar