The Colours of the Striæ in Mica

Abstract

PROBABLY the striæ, regarded by the authors as boundaries between regions of slightly different thicknesses, are the same lines as can be seen by reflections of soda light, as described in my note on “Regularity of Structure in Actual Crystals” (Phil. Mag., vol. xix., p. 96, 1910). Doubtless the Foucault method shows them in a more striking manner, and, in any case, the colour effects are novel, so far as I know, and worthy of a closer examination.