抄録
A series of striae equally spaced was observed in a region of electron-micrograph where two thin rectangular crystal flakes of sericite, a clay mineral, overlapped each other in almost parallel orientation, but with a small rotational angle around their common axis. An interpretation of this striation by hypothesis of double diffraction of electrons caused by rotational overlapping of two crystal flakes was carried out. The possible spacing of the net plane responsible for this diffraction was calculated from the separation of the striation and the small rotational angle of the two flackes. The result did not contradict with that from the electron diffraction photograph of a single flake obtained by a three-stage electron microscope. Thus, this hypothesis has proved itself to work for the interpretation of the present observation.
