344 HISTORY OF ACOUSTICS. 



but it was not shown that no other type of oscilla- 

 tion would give rise to the same accordance of force 

 and motion. Newton's reasoning also gave a deter- 

 mination of the speed of propagation of the pulses : 

 it appeared that sound ought to travel with the 

 velocity which a body would acquire by falling 

 freely through half the height of a homogeneous 

 atmosphere ; " the height of a homogeneous atmo- 

 sphere" being the height which the air must have, 

 in order to produce, at the earth's surface, the 

 actual atmospheric pressure, supposing no diminu- 

 tion of density to take place in ascending. This 

 height is about 29,000 feet; and hence it followed 

 that the velocity was 968 feet. This velocity is 

 really considerably less than that of sound, but at 

 the time of which we speak, no accurate measure 

 had been established ; and Newton persuaded him- 

 self, by experiments made in the cloister of Trinity 

 College, his residence, that his calculation was not 

 far from the fact. When, afterwards, more exact 

 experiments showed the velocity to be 1142 English 

 feet, Newton attempted to explain the difference by 

 various considerations, none of which were adequate 

 to the purpose ; as the dimensions of the solid 

 particles of which the fluid air consists; or the 

 vapours which are mixed with it. Other writers 

 offered other suggestions; but the true solution of 

 the difficulty was reserved for a period considerably 

 subsequent. 



Newton's calculation of the motion of sound, 



