39't> Experiments on Vibrating Surfaces. 



fore, were fo much the more valuable ; but, as far as I know, 

 few befides himfelf have employed their attention on this 

 fubjec"l, and perhaps beeaufe it requires long pra&ice to 

 perform experiments of this nature, fo as to make progrefs 

 in a branch of fcience hitherto uncultivated. But, until 

 thefe experiments fliall more engage the attention of philo- 

 fophers, we cannot expeiSt that the fubject will be much 

 illuftrated; and therefore I conceive it may be of fome utility 

 if I here give a fhort account of the method of making expe- 

 riments on vibrating furfaecs, which I hope will enable any 

 one to repeat them with facility. 



I have for fome time paft turned my attention to fuch ex- 

 periments, and I flatter myfelf that I have made improve- 

 ments in regard to thofe which Dr. Chladni announced in 

 his New Theory of Sound. By my experiments I was con- 

 dueled to many rules, a knowledge of which will render it 

 very eafy to repeat thefe experiments. I made them accord- 

 ing to the inftruetions given by Dr. Chladni in the work 

 above mentioned, which appears to me, however, to be rather 

 too fhort. 



The vibration figures arife, it is well known, beeaufe 

 during the movement of a furface, which is connected with 

 the fenfation of found in our organs of hearing, fome parts 

 of the furface arc at reft, and others in motion. If the fur- 

 face be ftrcwed over with bodies eafilv put in motion, fuch 

 for example as fand, thefe during the vibration remain on 

 the parts at reft, and are thrown from the parts in motion. 

 The form of the parts at reft, which will be fhewn by the 

 fand that remains unmoved, and which in general is fym- 

 metric, is called a vibration figure. To produce fuch a fi- 

 gure, nothing is neccfifary but to know the method of bring- 

 ing that part of the furface which you with not to vibrate 

 into a ftate of reft, and of putting in motion that which you 

 with to vibrate : on this depends the whole expertnefs of pro- 

 ducing vibration figures. 



The furfaces fitteft for being made to vibrate, are panes 



of 



