444 Experiments on the Tranfmijfion of found. [Book V. 



propagated. According to Mr. Haukfbee, who has 

 *made deep refearches into this branch of philofophy, 

 when air has acquired twice its common denfity it 

 tranfrnits found twice as far as common air ; whence 

 he reafonably concludes, that found increafes, not 

 only in direct proportion to the denfity of the air, but 

 in proportion to the fquare of this denfity. 



If found was propagated in an elaftic fluid more 

 denfe than the air, it ^would be carried proportionably 

 farther. I have proved this, fays M. Briflbn *, by 

 putting a fonorous body into carbonic acid gas or 

 fixable air, the denfity of which is about one-third 

 more than that of atmofpherical air; the confequence 

 was, that at that time, and in that fituation, the found 

 was very confiderably increafed. For the fame rea- 

 fon, the drynefs of the air, which increafes its denfity, 

 has a confiderable effe6b in rendering found louder 

 and more audible. Sound is alfo much increafed by 

 the reverberation of the pulfes of the air from thofe 

 furrounding bodies againft which they ftrike, whence 

 it happens that mufic is fo much louder in a clofe 

 apartment than in the open air. 



Elaftic fluids are, however, not the only medium 

 through which found may be tranfmittedj for it may 

 be propagated by means of water and other liquors, 

 which may be proved by immerfmg a fonorous body 

 in water; but it muft be obferved, that in this 

 cafe the found will be lefs perceptible, and will not 

 extend to fo great a diftancej the caufe of this dimi- 

 nution is, becaufe mediums for the tranfmiflion of 

 found fhould be elaftic, and that is a property which 

 water and other liquors poffefs only in a very re-i 

 ftrided degree. 



* Elem. de Phyfique, torn, ii. p. i6|. 



Sound 



