192. What is the third advantage? Give examples. How is the velocity of motion in machinery usually varied? What is the fourth advantage? Mention examples. Describe the instrument called a Lewis.
193. What is said of the title by which Aristotle distinguished man from other animals?
CHAPTER XII.
194. What is sound? What relation has sound to rapidity of vibration? Mention cases in which the vibration of sounding bodies is manifest to the sight and touch. What is said of wind instruments?
195. State the analogy of a sounding body to a pendulum. Describe the process by which the sensation of sound is produced. Where does the vibration caused by the sounding body stop in the ear? What is transmitted from thence to the brain?
196. Give examples of the transmission of sound through various substances? State the experiment by which it is shown that sound is not transmitted through a vacuum. What is said of sound at great heights?
197. How far has the sound of a volcano been heard? If the same sound were made in space at that distance from the earth why could not the inhabitants hear it? What is the cause of the noise of bodies passing through the air? Why do the heavenly bodies, moving so rapidly, produce no sound? Cite examples showing the different velocities of sound in different media.
198. What is said of the uniformity of the velocity of sound? Show how we can measure distances by sound as compared with light in velocity. Upon what does the loudness of sound depend? Illustrate this point.
199. What is said of the diffusion of sound? What of its reflection? What of echoes?