14.(Pg. [182]) What effect has this upon his apparent place?
15.(Pg. [182]) How is the length of the day affected by refraction?
16.(Pg. [183]) How are rays refracted, which fall obliquely upon a flat pane of glass, ([fig. 5, plate 19]?)
17.(Pg. [183]) What is the reason that objects are distorted, when seen through common window glass?
18.(Pg. [184]) What is meant by a lens?
19.(Pg. [184]) What are the five kinds called, represented at [fig. 1, plate 20]?
20.(Pg. [184]) What is meant by the axis of a lens?
21.(Pg. [184]) How are parallel rays, refracted by the double convex lens, [fig. 6, plate 19]?
22.(Pg. [184]) What is meant by the focus of a lens?
23.(Pg. [184]) What is the focal distance of parallel rays, from a double convex lens?