P,R0'?AGATION or SOUND, 127 



Sincq the above' wa5 wTitten,: I )Havie been informed that He vlndicatca 

 ihi.s wfttter l.as^a^i^utllly been piiblidied, but know not in what '**^^'"** 

 work. I hopt;>y.Ott will itill have the goodnefs to infert this as 

 an oric^inedcpmnmmiUwfi, Bis.l do not think the person who 

 has publiOied it wiJl have the impudence to call it; his own, 

 and 9s Mr, Kirwan, and other celebrated chemifts long ago 

 advifed me. to publiftvit^ I have already ftated my reafons tor 

 not following luch good advice. ; • 



As I have noyv been forced to appear before the public, I 

 have hopes I ftiall be able to prevail on Tome of my friends to 

 tjommit themfelves in the fame way, in the confidence that 

 their labours will be ioatid ufeful to the public. 

 I am, Sip, 



Year's truly, 



ANDREW TH0MS0^3•. 



Banchory^ hy Aberdeeriy 

 May 5th, 1S05. 



XIX. 



Memoir on the Propagation of Sound. ^j/M.Hassenfratz.* 



1. HE production of found is afcribed by all natural philofo. Sound produced 

 phers to tiie vibration of the molecules of bodies. by vibrations. 



The vibration of (hefe molecules admits of two kinds of which differ ia 

 jnodification; Ifl, in velocity; 2ly, in magnitude. The fir^t ^t^m'tude.'* ''' 

 of thele determines ll^e nature of tones; the fecond, their 

 force or intenfU)'. , 



< Sound is tranfiDitted :o the ear by the molecules that fill the The fonorou* 

 medium or interval between the fonorous body and the organ jj°^^jJJ^[J^^j"jj 

 of the hearing. The movement ot the fonorous body impreflesfome medium, 

 on the molecules of the medium an impulfe, which they '^^''i^'■^^^*'"' ''^ 



r » / vvhich are con- 



tranlmit from one to another, till it reaches the ear, with a tinned to the 

 greater or lefs velocity. In this tranfmiffion the vibration may ^^'^^ 

 undergo two kinds of alteration: 1ft, in its velocity; 2dly, in 

 its intenfify. In this memoir I iliall only tranfcribe fome ex- 

 periments relative to the velocity of foujid. 



Philofophers have long been engaged in determining the The velocity of 



velocity of found, but conlidering the air as the chief medium . ^^^^^'^** 

 ' ° examined only 



* Annales- de Chimie, Vol. LIII. p. 64, 



m air. 



by 



