266 NEWTON S PRINCIPIA. 



CHAPTER VII. 



THE MOTION OF WAVES. 



1. General consideration on the nature of Waves. 



2. Waves in air sound. 



a. The nature of sound deduced from the phenomena. Scholium, 



Prop. L. 



j8. Examination of the case considered by Newton. 

 7. Velocity of sound Newton s error. 



5. The manner in which sound spreads after entering through an 



orifice. Newton xlii. 

 . The notes sounded by different pipes. Scholium, Prop. L. 



3. Waves in water. 



a. The motion is of the vibratory kind, 

 fr Newton s reasoning on this subject. Newton, xliv. 

 7. Velocity of waves. Newton xlv. & xlvi. 



e. The nature of the motion of waves as given by a strict hydro- 

 dynamic theory. Note viii. 

 Waves caused by the motion of a boat, 

 yw. Cause of breakers over sunken rocks. 



6. How the wind raises the waves. 



1. To one who has never considered the nature of the motion 

 that occasions the appearance of a wave, the idea is at first 

 difficult. John Bernoulli the younger * declared that he 

 could not understand Newton s proposition on this sub 

 ject. The best illustration is that of a field of standing 

 corn, because it clearly shows that, in some waves at least, 

 there is no actual transfer of a quantity of matter. When 

 the wind blows on the field a hollow will be seen travelling 

 along it. This is a wave. There can manifestly be nothing 



* Whewell, History of Inductive Sciences, vol. ii. p. 310. quotes Prize 

 Dis. on Light, 1736. 



