1835.] Observations on Visible Vibration. 359 



4. Among the Sciences which have been advanced more 

 or less towards perfection, the Science of Sound seems to 

 have shared an uncommon neglect, and, considering its 

 high importance, we are naturally surprised that no syste- 

 matic work, including details and recent discoveries in the 

 Science, exists. Many Philosophers of high character have 

 of late years added much, but their results are still con- 

 fined to the journals in which they first appeared, and most 

 cordially ought we to desire that some master mind would 

 devote itself to a full developement of this beautiful science. 



5. I believe that Chladni, a German philosopher, about 

 the year 1787, first propounded the general law, that, in 

 order to produce a musical note from a glass containing a 

 liquid, both glass and liquid must vibrate in unison as a 

 system. It will be seen, however, in the course of these 

 experiments, that this law (if such it be) is by no means 

 universal in its application. 



6. Chladni also first rendered vibration visible, and 

 reduced visible vibration to a system. His method con- 

 sisted in strewing sand on glass plates, which, when 

 vibrated, caused the sand to arrange itself into various 

 beautiful forms ; and, by means of experiment and calcula- 

 tion, he constructed tables of them, which have since been 

 extended considerably by Wheatstone and others. 



7. If a glass containing water be vibrated by moving a 

 moistened finger round the edge, the water will undulate, 

 but the form of the undulse will not be very distinctly seen 

 on account of the length and transparency of the fluid. 

 Now, it occurred to me that by employing a denser fluid 

 the figures would be stronger, and better defined. 



8. I accordingly poured about a fluid ounce of mercury 

 into a foot glass, and, as soon as the note was produced by 

 moving the moistened finger round the edge of the glass, 

 the mercury assumed a very beautiful appearance. A series 

 of concentric circles or bands of undulse were formed, the 

 centre of the mercury being the common centre of the 

 whole, round which centre a star appeared to revolve in 

 the direction of the finger, the radii of the star seeming 

 independent of the undulating bands. Within these bands 

 there also appeared a square figure with rounded corners, 

 which may be very distinctly seen by twilight, where the 



