and Observations on Visible Vibration. 423 



Whenever a note is produced, where the centres of vibra- 

 tion include the lip or handle, the lower fundamental note 

 will be produced, as in Figure 1 ; but where the centres of 

 vibration do not include the lip or handle, then the upper 

 fundamental note will be produced, as in Figure 2. The 

 difference between these two cases is, that in Figure 1, 

 where a centre of vibration is in the lip, the velocities of 

 the vibrations of the vessel are diminished, the lip clogging 

 the whole vessel : the result is, therefore, a lower note 

 than in Figure 2, where the lip occupies the place of a 

 node, and the four vibrating arcs being scarcely impeded 

 by the lip, the result is a higher tone. A similar explana- 

 tion applies to the production of the two secondary tones 

 of the first kind, except that, with the lower note of the 

 two, one-sixth part of the vessel is damped by the lip or 

 handle instead of one-fourth, as in the former case. A 

 vessel with both a lip and a handle does not alter the result, 

 double fundamental notes and secondary tones being pro- 

 duced. If a common blue cylindrical cup with a handle 

 be employed, my theory can be proved in an interesting 

 manner. Such a cup will yield two fundamental notes with 

 an interval of about a third between them ; but if the handle 

 be struck off, the lower fundamental note ascends nearly, and 

 in some cases, quite to the upper, and the two first secondary 

 tones merge into one. It is necessary that the handle be 

 removed carefully : — a small saw moistened with turpen- 

 tine effects the purpose best, and the part where the handle 

 was affixed must be filed down smoothly, and on a level 

 with the exterior surface of the cup. In one case, where 

 this amputation was nicely performed, an interval of a fifth 

 between the two fundamental notes of the cup with a 

 handle, was reduced to unison when that appendage was 

 removed, the upper note of the two, of course, always 

 being the one fundamental note remaining. 



125. Supposing this explanation to be correct, I saw no 

 reason why, a priori^ vessels of glass, provided they were 

 lipped or furnished with handles, should not yield similar 

 results. In this supposition I was not disappointed, for, 

 on vibrating a small lipped chemical test glass 1^ of an 

 inch in diameter containing coloured water, I got two 

 fundamental notes, each producing four fans. One note 



