'X~6 On the Tones produced hj an Organ-pipe 



depends merely on the length of the pipe, and not on its di- 

 ameter; fo that the velocity is not changed when the pipe 

 is intlclinitelv enlarged, or, what is the fame thing, when it 

 is totallv removed, fo as to aiford free accefs to the air on all 

 fides. Sound therefore is diffufed through a certain fpaceof 

 air, in the fame lime in which a column of air inclofed in a 

 pipe makes one vibration ; a propofition which has been 

 proved in the before-mentioned papers of Eulcr, Bernoulli, 

 and Lambert, and alfo bv Count Giordano Riccati in his 

 Treatife on Elaftic Fibres or Strings, and which is confirmed 

 by ex-pcricnce. Hence it follows, that the number of the 

 vibrations made by the air in a pipe mav be found, if the real 

 vclocitv with which found is conducted through the air be 

 divided by the length of the column of air contained in the 

 pipe. 



The labours undertaken by Newton, Euler, Daniel Ber- 

 noulli, Lambert, Giordano Riccati, and others, to deter- 

 mine, from general mechanical principles, the velocity with 

 which found is condu(?t;ed, have given no other rcfults 

 than thofe taught by experience. By all thefe theoretic re- 

 fearches the fpace through which found paffes in the air, or, 

 in general, in any expanfible fluid fubfl:ance, was found to 



be = a/—^— ; where g is the fpace through which a heaxy 



h 

 body falls in a fecond, or in any given time; a the elaflicity 



of the expanfible fluid, which is alTumed equal to the pref- 

 fure it fufta'ns from the atmofphere; and Z* the deufity of 

 the expanfible fluid : a may be alfo the height of the baro- 

 meter, if the denfity of the mercurv be confidered as i. 

 Theory gives, therefore, about 900 Parifian feet as the dif- 

 tance to which found is tranfmitted through the air in the 

 courfe of a fecond ; whereas this fpace has been found, by 

 experience, to be equal to about 1038. No one has ever yet 

 alligned a fufficieut reafon for this difference. The moit 

 common conjecture i?, that it muft be owing to a mixture 

 of various foreign particles 3 but this, by thofe acquainted 



with 



