1835.] Observations on Visible Vibration. i'S? 



secondary tones, and in passing from them to the funda- 

 mental, or from the fundamental to the secondary tones 

 without shifting the finger from the glass. Thus, during 

 the continuance of the fundamental tone, the mercury or 

 liquid vibrates readily, and instantaneously becomes quies- 

 cent during the vibration of the secondary tone, and so on 

 alternately. I have even produced the fundamental tone 

 from one semicircle of the glass, and the secondary tone 

 from the other semicircle, so that during one whole circuit 

 of the finger round the glass, the contents have been 

 alternately vibrating and quiescent ; and if the double glass 

 (62) be employed, the fluids within and without the interior 

 glass, are alternately in a state of vibration and quiescence 

 during one whole revolution of the finger. 



66, I therefore venture to deduce from the statements 

 in the foregoing part of this paper, the following propo- 

 sitions : — 



1 . That a series of secondary tones can be produced by the 



vibration of a glass goblet^ which tones do not necessarily 

 harmonize with the fundamental note of the glass. 



2. That the interior surface of the glass is in a state of posi- 



tive vibration during the production of the fundamental 

 note, the exterior being negative. 



3. That the exterior surface of the glass is in a state of posi- 



tive vibration during the production of the secondaiy 

 tones, the interior being negative. 



67. There are few solids in nature incapable of yielding 

 musical tones. All earthenware and porcelain utensils will 

 yield such tones by passing the moistened finger round 

 their edges. I am informed that a musical instrument has 

 even been constructed and fine tones produced by the vibra- 

 tion of blocks of granite of peculiar and varying shapes. 

 I have produced musical notes from lumps of ice, and it is 

 known that by giving lead a peculiar shape it will elicit a 

 musical sound. I have procured loud and shrill tones 

 from watch glasses and from a great variety of plane surfaces 

 of window glass. Fracture is, I believe, often occasioned 

 by the efibrts of the glass to vibrate isochronously with an 

 externally vibrating object. Thus, a thin goblet may be 

 fractured by the unisonant human voice. The panes of our 

 windows are constantly undergoing severe discipline from 

 the action of hail, rain, and wind, from violent opening 



