78 PHENOMENA OF HEAT AND SOUND. 



Aristotle appears to have believed that the motion to 

 which sound is due travels in a straight line, and not in all 

 directions, if the medium is unbroken. There is not any 

 passage in his vv^orks v\^hich seems to represent clearly his 

 views on this subject, but in the Aristotelian treatise, De 

 Audibilibus, it is stated that it is shown, by means of 

 ships' masts and long pieces of wood, that sound travels in 

 a straight line, for if these are struck at one end the sound 

 is carried straight along, unless there is a chink in the 

 wood, and it bends back at the knots and cannot proceed in 

 a straight course.* 



Aristotle says that sound is heard in water, but to a less 

 extent than in air.t Sound is heard more distinctly in 

 water than in air, as is well known, and it is very probable 

 that Aristotle was relying not on experiment but merely on 

 abstract reasoning. 



It is stated in the Problems, xi. 23, that in the pro- 

 duction of an echo the reflection is in the direction of a 

 like angle, Tand therefore the voice of the echo is like the 

 voice to which it is due. The Problems is an Aristotelian 

 treatise, probably not written by Aristotle, but the above 

 statement shows that the writer knew that, in the case of 

 sound, the angles of incidence and reflection are equal. 



* De Atidibilibus, 802. f De Anhna, ii. c. 8, 4196. 



