1823.] ^ Mr. Wheatsione on Soiirid, 85 



cal divisions of sonorous bodies, each of which will give birth to 

 numerous vibrating corpuscles whose excursions are greater, 

 and the sound will be rendered audible. Dr. Savart has well 

 investigated the modes of division in surfaces put in motion by 

 communicated vibrations. Ail those phonics whose limited 

 superficies preclude them from exciting in themselves a sufficient 

 number of vibrating corpuscles, when insolated, produce scarcely 

 any perceptible sound, as extended chords, tuning forks, &c.but 

 those whose superficies or solidities are more extended, as bells, 

 elastic laminae, columns of air, &c. produce sufficient volume of 

 sound without accessory means. 



Loudness of sound is dependent on the excursions of the 

 vibrations ; volume, or fulness of sound, on the number of 

 co-existing particles put in motion. Thus the tones of the 

 iEolian harp, on account of the number of subdivisions of the 

 strings, are remarkably beautiful and rich, without possessing 

 much power ; and the sounds of an Harmonica glass, in which 

 a greater number of particles are excited than by any other 

 means, are extraordinarily so united, according to the method of 

 excitation, with considerable intensity ; their pervading nature 

 is one of the greatest peculiarities of these sounds. 



The following is a recapitulation of the various properties of 

 sound, which are attributable to modifications of the vibrating 

 corpuscles ; 



The tune "^ w f, velocities of the vibrations. 



The time <% I continuance of the vibrations. 



The intensity 



The richness, or volume 



The quantity (timbre) 



excursions of the vibrations, 

 number of co-existing vibrations, 

 magnitudes of the vibrating 

 corpuscles. 



It has often been thought necessary to admit the existence of 

 more minute motions than the sensible oscillations, in order to 

 account for many phenomena in the production of sound. Per- 

 vault in his " Essai du Bruit," insisted on their necessity more 

 than any other author I have read : he imagined, that the vibra- 

 tions have a much greater velocity than the oscillations which 

 cause them, but the experiment he adduced to prove this is far 

 from conclusive ; he mistook for these vibrations the oscillations 

 of the subdivisions of the long string he employed. Other dis- 

 tinguished philosophers have had ideas of a similar nature, and 

 Chiadni thinks their existence necessary to account for the 

 varieties of quality. I, however, conceived I was the first who 

 had indicated these phenomena by experiment, until a few days 

 ago repeating them, together with the others which form the 

 subject of this paper, in the presence of Prof. Oersted, of 

 Copenhagen, he acquainted me with some similar experiments of 

 his own. Substituting a very fine powder, Lycopodion, instead 

 of the sand used by Chiadni, for showing the oscillations of 



