Jfl6 Experiments on the Tranfm:Jfton of Soiiiid. 



. 2. That thefe effe£ls arifc from the tranfmiffion of found by folid bodies being in general 

 better than by the air, and the peculiar modification of the tone by eacli. 



3. That the refonance of mufical inftrumcnts is more panicularly to be attributed to this 

 caufe '^. 



4. The experiments with mufical inflrumcnts afford reafon to conclude that th.e volume 

 of bodies has an influence on their rcfounding properties. 



J. M. dc Maupertuis -I- has afiirmed that tlie ri.fonance of mufical inftruments is owing to 

 the inftrumcnt containing fibres of every pofiible length; each found puts thafe in motion 

 which are either in unifon or concord witli itfelf, while the others remain motionlefs J. 

 But the fccond experiment, in which it is fliewn that there is no part of any refounding 

 body which docs not tranfmit the found, will not admit of the adoption of the ingenious 

 thought of that celebrated author. 



■ 6. As marble in fome degree extinguifhes found, and bears tlie fame rank among folid 

 bodies as inflammable air among fluids, it is not advifable to ufe it in the coiiflrutlion of 

 churches, concert-rooms, theatres, or other edifices in which the propagation of found is 

 defirable. 



Such are the principal refults of experiments which, on the whole, have engaged my at- 

 tention for a number of years ; notwithllanding which, I have not been yet able'to extend 

 them, particularly iliofe belonging to the fecond part, as far as they are capable of being 

 carried. 1 (hall not, however, have the mortification to think my endeavours ufelefs, if 

 the fociety to whom my works are addrefled ihall think they may conftitute an addition to 

 the fum of the difcoveries in fcience which they continually prefent to the world. 



Annotations to the Paper of M. Perrole on Sound. 



THE philofophy of found is flill exceedingly imperfe£l. Mathematicians have efta- 

 bliflied theories upon the (imple data that fonorous bodies vibrate, and that thefe vibrations 

 are communicated to the furrounding elallic fluid, of which the denfity and fpring are mea- 

 furable. M. Perrole's experiments fhew that the obje£t of rcfearch comprehends much 

 more than this. The following queries and remarks may perhaps prove of fome advantage 

 to the curious enquirer: 



I. There can be no doubt but that undulation in the air accompanies its propagation of 

 found, and that fonorous bodies are put into a vibrating ftate by percuffion. The proofs 

 of this are too numerous to be detailed. Sound propagated through fluids feems to diminidi in 

 proportion to the diftance, and fo probably it does in folid bodies. Its intcnfity mud depend 

 upon the elafticity and denfity jointly. The military pra<flice of lying down on the ground 

 to liften for footfteps is well known ; and Dr. Franklin relates that he heard the blow of 

 two flones flruck together at the diftance of near a mile, fmart and ftrong as if clofe at 

 the ear §. \Vc have no information refpeding tlie velocities of founds propagated through 

 folid bodies. 



** The numerous furfacci which thcfc inftruments prefent muft llkcwifc render thtm more fonorous. P. 

 . .(• Acad. Paris, 1714.. 

 ' 1 The memoir of M. de Mjupemiis relates to (Iringed inflrumentj only. P. 



§ Expe r' meuts and Obfcrvalions. London, 1774, p. 445. 



.X 2. As 



