26 HISTORY OF ACOUSTICS. 



back like a ball." Nothing material was added to such views till 

 modern times. 



Thus the first conjectures of those who philosophized concerning 

 sound, led them to an opinion concerning its causes and laws, which 

 only required to be distinctly understood, and traced to mechanical 

 principles, in order to form a genuine science of Acoustics. It was, 

 no doubt, a work which required a long time and sagacious reasoners, 

 to supply what was thus wanting ; but still, in consequence of this 

 peculiar circumstance in the early condition of the prevalent doctrine 

 concerning sound, the history of Acoustics assumes a peculiar form. 

 Instead of containing, like the history of Astronomy or of Optics, a 

 series of generalizations, each including and rising above preceding 

 generalizations ; in this case, the highest generalization is in view 

 from the first ; and the object of the philosopher is to determine its 

 precise meaning and circumstances in each example. Instead of 

 having a series of inductive Truths, successively dawning on men's 

 minds, we have a series of Explanations, in which certain experi- 

 mental facts and laws are reconciled, as to their mechanical principles 

 and their measures, with the general doctrine already in our posses- 

 sion. Instead of having to travel gradually towards a great discovery, 

 like Universal Gravitation, or Luminiferous Undulations, we take our 

 stand upon acknowledged truths, the production and propagation of 

 sound by the motion of bodies and of air ; and we connect these 

 with other truths, the laws of motion and the known properties of 

 bodies, as, for instance, their elasticity. Instead of Epochs of Dis- 

 covery, we have Solutions of Problems ; and to these we must now 

 proceed. 



We must, however, in the first place, notice that these Problems 

 include other subjects than the mere production and propagation of 

 sound generally. For such questions as these obviously occur : 

 what are the laws and cause of the differences of sounds ; of acute 

 and grave, loud and low, continued and instantaneous ; and, again, 

 of the differences of articulate sounds, and of the quality of different 

 voices and different instruments ? The first of these questions, in 

 particular, the real nature of the difference of acute and grave sounds, 

 could not help attracting attention ; since the difference of notes in 

 this respect was the foundation of one of the most remarkable mathe- 

 matical sciences of antiquity. Accordingly, we find attempts to 

 explain this difference in the ancient writers on music. In Ptolemy's 

 Harmonics, the third Chapter of the first Book is entitled, " II-\v the 



