PRELUDE TO THE SOLUTION OF PROBLEMS. 27 



acuteness and graveness of notes is produced ;" and in tli ,s, after 

 noting generally the difference of sounds, and the causes of difference 

 (which he states to be the force of the striking body, the physical 

 constitution of the body struck, and other causes), he comes to the 

 conclusion, that " the things which produce acuteness in sounds, are a 

 greater density and a smaller size ; the things which produce grave- 

 ness, are a greater rarity and a bulkier form." He afterwards explains 

 this so as to include a considerable portion of truth. Thus he says, 

 " That in strings, and in pipes, other things remaining the same, those 

 which are stopped at the smaller distance from the bridge give the 

 most acute note ; and in pipes, those notes which come through holes 

 nearest to the mouth-hole are most acute." He even attempts a 

 further generalization, and says that the greater acuteness arises, in 

 fact, from the body being more tense ; and that thus " hardness may 

 counteract the effect of greater density, as we see that brass produces 

 a more acute sound than lead." But this author's notions of tension, 

 since they were applied so generally as to include both the tension of 

 a string, and the tension of a piece of solid brass, must necessarily 

 have been very vague. And he seems to have been destitute of any 

 knowledge of the precise nature of the motion or impulse by which 

 sound is produced ; and, of course, still more ignorant of the me- 

 chanical principles by which these motions are explained. The notion 

 of vibrations of the parts of sounding bodies, does not appear to have 

 been dwelt upon as an essential circumstance ; though in some cases, 

 as in sounding strings, the fact is very obvious. And the notion of 

 vibrations of the air does not at all appear in ancient writers, except 

 so far as it may be conceived to be implied in the comparison of 

 aerial and watery waves, which we have quoted from Vitruvius. It 

 is, however, very unlikely that, even in the case of water, the motions 

 of the particles were distinctly conceived, for such conception is far 

 from obvious. 



The attempts to apprehend distinctly, and to explain mechanically, 

 the phenomena of sound, gave rise to a series of Problems, of which 

 we must now give a brief history. The questions which more 

 peculiarly constitute the Science of Acoustics, are the questions con- 

 cerning those motions or affections of the air by which it is the 

 medium of hearing. But the motions of sounding bodies have both 

 so much connexion with those of the medium, and so much resem- 

 blance to them, that we shall include in our survey researches on that 

 ubject also. 



