2^8 Of Winds and Sounds,

three Numbers it is, when the Firji is to thi'Third, as the Difference between the Fr'ft

directly, and as the Square Root of the Tending Force &verfely. •„

6. Hence if D and F be given, T is as L ; that >•

if the Diameter of the String and its Tending f° rCcontinue the fame, the Time of a Vibration will f fwith the Length of the String , or be always proportffto it. Thus \ of the Monochord vibrates in Jr °* , eTime that it does, which is called an Octave ; ^ of OMonochord vibrates in ~ of the Time, and is calledFifth ; | vibrates in | of the Time, and is calledFourth , and so on. _ .

7. If F and L be given, T is as D ; that is, id^h

Tending Force and Length of the String remainfame, the Time of a Vibration will vary with , anaproportional to , the Diameter of the String . %

8. If D and L be given, then T is inversely as r ’

that is, if the Diameter and Length of the String pgiven, then the Time of a Vibration will be as the SqU aRoots of the Tendhig Force. ,

9. Now as the Tone of a String depends entity

upon the Time of a Vibration, it is easy to underft an ’that whatever the founding Body be, or how tr> a ^soever there be together, if when they emit a SoundVibrations in each are of the fame Duration, they 'f 1 .all be of the fame Note, Tone, or Tune, whichcalled Unison. - »

10. In a Drinking-Glass, if a Person pastes his Vted Finger briskly round the Brim of the Glass, P re ^ 1it at the lame. time, he will by Degrees raise Trjm 0I ” SVibrations in the Parts of the Glass, which wist P x0 °' l JiSalone or Sound, which will be constant so

the Action of the Finger is continued, and wof a ^ e -more intended or heightened': So that if thecontinued long enough, the Agitation will be so % l . ■as to disengage the Particles, or break theirand thus reduce the Glass to Pieces, if not too