23.(Pg. [161]) What two angles are always equal in this case?
24.(Pg. [161]) To what law in mechanics, is this analogous, as represented in [fig. 4, plate 2]?
25.(Pg. [161]) What is represented by [fig. 6, plate 15]?
26.(Pg. [161]) By what light are we enabled to see opaque, and by what, luminous bodies?
27.(Pg. [161]) What enables us to see a ray of light in its passage, through a darkened room?
28.(Pg. [162]) By what reasoning would you prove that an object, such, for example, as a house, is seen by reflected light?
29.(Pg. [162]) Why may one side of such object appear more bright than another side?
30.(Pg. [162]) How is the fact exemplified by the sun, or moon, shining upon water?
31.(Pg. [162]) Why is this best evinced by moonlight?
32.(Pg. [163]) By what light do we see the moon, and why is it comparatively feeble?