the usual phenomena
(cropped from border; blur: radius 20, octagon (8))
showing the appearance when the first type [distinct and distant from each other] and the second type [slow moving striations] are observed together through the rotating mirror.
T. Kikuchi (1894?-1921 *). “On the Moving Striations in a Neon Tube.” Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. 99 (June 1, 1921): 257–261
epigram p 258
appearances; striations; waves; weather front
T. Kikuchi, “On the Moving Striations in a Neon Tube” (1921)