314 



Vibrations of 

 plane & curved 

 elastic sur- 

 faces. 



Elastic plates. 



£<cat»ir.ation 

 r>i these by 



Paradisi. 



The vibrations 

 tjo throufh a 

 ser.ies of 

 changes. 



SCIENTIFIC NEWS, . 



of the sound of bells ; but Mr. Chladni has shown very 

 truly, that his hypotheses do not accord with nature. 



The last two sections of this part are devoted to the vi- 

 brations of plates and bells, or plane and curved surfaces in 

 general, a subject altogether new in experimental philoso- 

 phy; and which, notwithstanding the striking regularity of 

 the phenomena, has resisted the efforts of the able geome- 

 tricians, who have attempted to treat on it. 



Mr. Chladni has ascertained the places, which the tones 

 we may draw from plates by giving them different forms, 

 and by causing them to sound in different methods, occupy 

 in the musical scale. But these inquiries are particularly 

 interesting, when combined with those for determining the 

 portions of each plate that have distinct and coexisting vi- 

 brations, and the remarkable curves that form their perime- 

 ters. For these experiments the plate, covered with fine 

 dry sand, is to be held between the thumb and one finger, 

 the ends of which press on directly opposite points of the 

 two faces, while a bow is drawn over some point of its peri- 

 meter. Sometimes a third linger is applied at different 

 points of one of the faces, to vary the results of the experi- 

 rnents. The point of support is always in one of the curves 

 of equilibration. The figure of these curves, and their ar- 

 rangement, depend on the position of the point of support, 

 that of the point to which the bow is applied, and that of 

 the different sounds we wish to produce by rubbing the bow 

 in different ways on the same point. A change in either of 

 these produces a correspondent change in the curves. 



While speaking of these curious phenomena, we cannot 

 avoid noticing a paper inserted in the first volume of the 

 Transactions of the Italian Institute, entitled Inquiries con- 

 cerning the vibrations of elastic plates. The author, Mr. 

 Paradisi, says in a note, that he was led to make his expe- 

 riments by a passage in the Bibliotheque Britannique where 

 Mr. Chladiffs were described. Having provided an appa- 

 ratus, by meanis of which he could keep the plates fixed at 

 any point of their surfaces without the assistance of the fin- 

 gers, he first perceived, that the curves of equilibration did 

 not arrive at settled figures, till after a gradual and continual 

 succession of variable figures; the generation of which, be- 

 ing 



