A visual display apparatus for producing toroid rings of a first liquid within a second liquid is disclosed. The apparatus comprises a subtantially transparent viewing vessel for containing the second liquid. A variable volume chamber has an ejection orifice in fluid communication with the second liquid contained within the viewing vessel. An ejection means is also provided for varying the volume of the variable volume chamber, thereby to dispel an ejection slug of the first liquid from the ejection port, thereby producing a series of toroid rings which propagate through the viewing vessel. A control means is connected to the ejection means for controlling the operation of the ejection means. The operation of the control means may be such that it can be used to vary the volume and frequency of the ejection slugs emitted from the ejection orifice.
展开▼
