Observations on Visible Vibration. 369 



any particular tone be accute or grave, provided it be 

 tbe lowest in point of pitch, that can be obtained from 

 the glass, such a tone is the fundamental note of the glass, 

 and is due to a quadripartite system of vibration. In ascend- 

 ing in the scale, the first secondary tone divides the glass 

 into six parts, the second secondary tone into eight parts, 

 and so on ; and this, I believe, will be found true of all 

 vessels of glass of whatever dimensions. I believe it will 

 also apply to vessels of porcelain and crockery ware, as 

 well as of metal ; but this will require a separate paper for 

 investigation. 



100. The centres of vibration are indicated by the longest 

 lines which dart from certain equi-distant parts of the inner 

 circumference of the glass on the liquid surface towards the 

 centre, which lines decrease in length on either side of the 

 centre of vibration until they cease to be perceptible (see 

 figure 1); and the nodes are shewn by the tranquillity of 

 the water between any two centres of vibration. When a 

 glass contains water, and the bow is strongly drawn against 

 its edge, the water at and about the centres of vibration 

 will be elevated, and at the nodes, the water will be de- 

 pressed ; and when the vibrating action has ceased, and the 

 surface of the water become tranquil, these elevations and 

 depressions will be exhibited in the form of a curved line 

 passing round the interior surface of the glass and above 

 the surface of the water. If the action of the bow be strong 

 the water will be sprinkled about on the interior surface of 

 the glass above the liquid surface, and this sprinkling will 

 exhibit the curved line very perfectly. Figure 2 will 

 illustrate this. 



Fig. 2. 



