Early tidal clocks researchers designed ingenious apparatus! Bennett and co-workers described theirs in a 1957 paper: “. ….recording apparatus employed [to record Minuca pugnax activity] is illustrated in the [above ] figure]. The crab was placed with a small amount of sea water in a plastic saucer covered with a circular piece of cardboard (B) which fitted the saucer. Each of 10 saucers was supported on one side by metal bands (C) which in turn fastened to a rigid horizontal bar (D). To the opposite side was attached a nylon thread (E) which was fastened to the lever of a recording system (F) equipped with an ink-writing pen. The movements crabs in the finely balanced saucers were recorded on a kymograph which completed a revolution every 24h.” A drawing of a typical analogue kymograph is shown. The rotating drum (G) is driven by a motor (H). As the drum rotates the pen marks the paper. Movement of the crab is registered by movements of the pen on the kymograph.