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1 Introduction Resonant waves can be generated when a disturbance such as an earthquake or tornado moves down the edge of a bay or harbour. The qualitative e¤ect of such a disturbance can be observed in a classroom, with minimal apparatus, on a small scale by anyone who causes a partially …lled wineglass to ”sing”(resonate) using a wet …nger. If one carefully examines the surface of the liquid it is possible to see that four ridges or crests follow the …nger around the rim. The photographs below were obtained using a turntable (Apfel’s idea [1]), milk as the liquid, a clear wineglass and a blackened wineglass. The surface of the liquid also exhibits other, smaller patterns called crispations (edge or cross waves [6]) which we do not attempt to model here (see Figure 2): The vibration pattern of the glass is called a ”quadrupole vibration” in the literature and the e¤ect of this vibration has undoubtedly been know ever since mankind discovered the delights of drinking liquids from …ne glass containers. Indeed the e¤ect of a singing wineglass is noted in the literature by the ever inquisitive Michael Faraday [2] in 1831! We discuss a simulation of the crests (not the crispations) using mathematics easy enough for senior undergraduates to understand as well as an animation of this e¤ect using the CAS Mathematica.

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