21.(Pg. [151]) By what experiment might we prove that air is the principal vehicle of sound?
22.(Pg. [152]) What other bodies convey sound, and how can it be shown that they do so?
23.(Pg. [152]) What is meant by a sonorous body?
24.(Pg. [152]) To what do they owe this property?
25.(Pg. [152]) How is this explained by [fig. 6, plate 14]?
26.(Pg. [152]) How is it illustrated by a stone thrown into water, and how far does this illustration apply?
27.(Pg. [153]) How are the vibrations propagated?
28.(Pg. [153]) How can we prove that sound, does not travel as rapidly as light?
29.(Pg. [153]) At what rate is sound said to travel?
30.(Pg. [153]) Is the velocity much influenced by the direction of the wind?