Abstract: A set of one or more closed receptacles, each having an internal partition dividing the interior into two compartments, each compartment being partially filled with a translucent flowable material such as a colored liquid. Preferably the receptacles are cylindrical in shape with the partitions extending diametrically, and the flowable material in a receptacle compartment is of a different color from that of the other compartment of the receptacle and, desirably, different from the color of flowable materials in other compartments of a particular set. Means are provided for rotating the receptacles about axes transverse to their partitions and, when a set of two receptacles is used as a clock, one receptacle is rotated at two revolutions per day and the other at one revolution per hour, as by a conventional synchronous clock motor.