Another similar example is furnished by such glasses as that shown in Fig. 37. On the one side it is marked “King,” on the other “Tinker.” The “innocent” invited to drink was asked to choose from which side he would drink, and, prompted by loyalty, vanity, or pure folly, he was almost certain to drink with the king rather than the tinker. But artfully concealed in the band of decoration round the rim was a series of small holes, through which, when the glass was tilted, the liquor ran, soaking the drinker’s waistcoat instead of finding its way down his throat. Possibly the old coaching glasses may fitly find a place in this connection. They are without feet, the stem ending in a bulb which was often cut. When, in the old coaching days, the vehicle pulled up at a wayside inn, the landlord brought out his tray with the glasses inverted upon it. They were filled from the bottle and emptied at once--the idea being that as the drink would have to be consumed at once, there was no need to make the glass so that it could be set down while the liquor was only partly consumed. These are now rare, and to discover one would be a great achievement for the ordinary collector. One may also mention the singing glasses, which were made to vibrate to a certain musical note, and so would repeat the note when sounded or sung, just as the string of a piano or violin will do. This, of course, was a great mystery to unscientific persons, but is susceptible of a very simple explanation. Evelyn was greatly puzzled over the phenomenon. Certain glasses, he remarked, “made an echo to the voice, but were so thin that the very breath broke them.” The fact is, of course, that the glass broke through the intensity of its own vibration, just as a pane of glass in a church window will sometimes break when the organ is used. The note played having the same period of vibration as the pane of glass, the latter vibrates in unison with it, and if the note is continued for sufficiently long, the vibration becomes so intense as to break the pane. It is for an exactly similar reason that a regiment of soldiers breaks step when marching over a bridge, for fear that the rhythm of the march might chance to coincide with the period of vibration of the bridge, and so set up rhythmic movements which might weaken the structure. Such glasses are distantly allied to the musical glasses which, when filled up to a certain point, produce a musical note when the bowl is thrown into vibration by the finger or a violin bow. By filling such glasses to different heights, it is possible to produce a complete scale, and so to play any desired tune.