n6 Dr. Young's Experiments and Inquiries 



exact mensuration. This species of sonorous cavity seems 

 susceptible of but few harmonic sounds. It was observed, that 

 a faint blast produced a much greater frequency of vibrations 

 than that which was appropriate to the cavity : a circumstance 

 similar to this obtains also in large organ pipes ; but, several 

 minute observations of this kind, although they might assist in 

 forming a theory of the origin of vibrations, or in confirming 

 such a theory drawn from other sources, yet, as they are not 

 alone sufficient to afford any general conclusions, are omitted 

 at present, for the sake of brevity. 



IV. Of the Velocity of Sound. 



It has been demonstrated, by M. De la Grange and others, 

 that any impression whatever communicated to one particle of 

 an elastic fluid, will be transmitted through that fluid with an 

 uniform velocity, depending on the constitution of the fluid, 

 without reference to any supposed laws of the continuation of 

 that impression. Their theorem for ascertaining this velocity is 

 the same as Newton has deduced from the hypothesis of a par- 

 ticular law of continuation : but it must be confessed, that the 

 result differs somewhat too widely from experiment, to give 

 us full confidence in the perfection of the theory. Corrected by 

 the experiments of various observers, the velocity of any impres- 

 sion transmitted by the common air, may, at an average, be 

 reckoned 1130 feet in a second. 



V. Of sonorous Cavities. 



M. De la Grange has also demonstrated, that all impres- 

 sions are reflected by an obstacle terminating an elastic fluid, 

 with the same velocity with which they arrived at that obstacle. 



